Selective adsorption of PVP on the surface of silver nanoparticles
- Authors: Mdluli, Phumlani S , Sosibo, Ndabenhle M , Mashazi, Philani N , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , van der Lingen, Elma
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247143 , vital:51550 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.07.049"
- Description: The use of surfactants to affect the shape evolution of silver nanoparticles is explored. This allows one to fine-tune the morphological evolution and the optical properties of the metal nanoparticles. Polyvinyl pyrrolidone (PVP) has been used as a surfactant to control the growth of silver nanoparticles at room temperature. In this paper, molecular dynamics simulations were performed to understand regio-selective adsorption of PVP that leads to the preferential growth of silver nanoparticles in dimethylformamide (DMF). The interaction energies between PVP and Ag(1 1 0), Ag(1 0 0) and Ag(1 1 1) crystal planes were calculated and in addition the length density profile of the surfactant on silver surfaces was also examined. Importantly, it has been demonstrated that the length distribution profiles analysis obtained from the molecular dynamics study fully explained the adsorption of PVP on the surface of silver nanoparticles through the carbonyl group of the PVP ring. The application of molecular dynamics simulation technique is important in understanding the evolution of silver nanoparticles and is vital in choosing the right surfactants.
- Full Text:
- Date Issued: 2011
Synthesis, density functional theory, molecular dynamics and electrochemical studies of 3-thiopheneacetic acid-capped gold nanoparticles
- Authors: Sosibo, Ndabenhle M , Mdluli, Phumlane S , Mashazi, Philani N , Dyan, Busiswa , Revaprasadu, Neerish , Nyokong, Tebello , Tshikhudo, Robert T , Skepu, Amanda , Van Der Lingen, Elma
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/246446 , vital:51477 , xlink:href="https://doi.org/10.1016/j.molstruc.2011.09.057"
- Description: Gold nanoparticles capped with a bifunctional ligand, 3-thiopheneacetic acid (3-TAA) were synthesised by borohydride reduction at room temperature. The transmission electron microscopy (TEM) analysis showed that the particle aggregates and had semi-linear partial linkages that could be attributed to multi-modal binding of the ligand with various gold nanoparticles through the terminal thiolether (–S–) group and oxygen of the carboxylic (–COOH) group. This bimodal interaction led to limited stability of the resultant nanoparticles when tested using highly electrolytic media. To investigate further, density functional theory (DFT) quantum chemical and molecular dynamic calculations were conducted. The energetically favorable binding modes of the ligand to gold nanoparticle surfaces using the Gaussian program were studied. The DFT results showed kinetic stability of Au–3-TAA–Au interactions leading to inter-particle coupling or aggregation. Electrochemical analysis of the resultant nature of the capping agent revealed that 3-thiopheneacetic acid did not form a polymer during the preparation of Au–3-TAA. The cyclic voltammograms of Au–3-TAA nanoparticles coated glassy carbon electrode showed a typical gold character with the oxidation and reduction peaks at 1.4 V and 0.9 V, respectively.
- Full Text:
- Date Issued: 2012
The effects of carbon nanotubes on the electrocatalysis of hydrogen peroxide by metallo-phthalocyanines
- Authors: Mashazi, Philani N , Mugadza, Tawanda , Sosibo, Ndabenhle , Mdluli, Phumlani , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/247174 , vital:51553 , xlink:href="https://doi.org/10.1016/j.talanta.2011.07.069"
- Description: The pre-grafted screen-printed gold electrode modified with phenyl-amino monolayer was investigated for covalent immobilization of phenyl-amine functionalized single-walled carbon nanotubes (PA-SWCNT) and metal tetra-amino phthalocyanine (MTAPc) using Schiff-base reactions with benzene-1,4-dicarbaldehyde (BDCA) as cross-linker. The PA-SWCNT and MTAPc modified electrodes were applied as hybrids for electrochemical sensing of H2O2. The step-by-step fabrication of the electrode was followed using electrochemistry, impedance spectroscopy, scanning electron microscopy and Raman spectroscopy and all these techniques confirmed the fabrication and the immobilization of PA-SWCNT, MnTAPc and CoTAPc onto gold surfaces. The apparent electron transfer constant (kapp) showed that the carbon nanotubes and metallo-phthalocyanines hybrids possess good electron transfer properties compared to the bare, pre-grafted and the MTAPc modified gold electrode surfaces without PA-SWCNT. The electrochemical sensing of hydrogen peroxide was successful with PA-SWCNT–MTAPc hybrid systems showing higher electrocatalytic currents compared to the other electrodes. The analytical parameters obtained using chronoamperometry gave good linearity at H2O2 concentrations ranging from 1.0 to 30.0 μmol L−1. The values for the limit of detection (LoD) were found to be of the orders of 10−7 M using the 3δ for all the electrodes. The PA-SWCNT–MTAPc modified SPAuEs were much more sensitive compared to PA–MTAPc modified SPAuEs.
- Full Text:
- Date Issued: 2011
Factors affecting participation rates in farming in the rural areas of South Africa: case of Amathole District Municipality
- Authors: Zamxaka, Xolisa
- Date: 2015
- Subjects: Agricultural systems -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Agricultural Economics)
- Identifier: vital:11233 , http://hdl.handle.net/10353/d1021291 , Agricultural systems -- South Africa -- Eastern Cape , Rural development -- South Africa -- Eastern Cape , Sustainable development -- South Africa -- Eastern Cape , Farms, Small -- South Africa -- Eastern Cape
- Description: South Africa and the rest of developing countries are faced with poverty and poor rural development. Rural participation in agricultural activities is one of the components that can be used to address the poverty challenge facing the people residing in rural areas. The broad objective of this research is to determine factors affecting participation rate in farming in the rural areas of Amathole District Municipality of Eastern Cape. In this study stratified random sampling method was applied in order to choose a sample out of 30 households that were interviewed 13 people belonged to Participants and 17 people belonged to non-Participants. The results from this study show that women participate a lot in farming activities. The multiple regression model was used to test the participation rates of the people in Amathole region specifically Phumlani area. A number of variables were considered in this study to assess the impact of different variables on participation in farming activities. The results showed that about 57% of the respondents are not participating in farming while 43% of the respondents participate. The farming participants that were interviewed all claim that there is a lack in farming support in the area. When there is no support of any kind, rural people would not be motivated to start development projects on their own. Consequently, this lack of farming support in the Phumlani area may have an influence on the number of farming participants. Therefore, the lack of support in the area may serve as a motivation for non-participants not to be influenced to farm. Rural farming needs to be promoted amongst the youth so as to protect and sustain agricultural growth in rural areas. The study has discovered that the youth of Phumlani is not actively involved in farming activities. Government can provide community members with farming resources so as to promote farming in the area. It would be wiser for the government to provide physical farming resources and implements rather than cash grants.
- Full Text:
- Date Issued: 2015
Facile deposition of gold nanoparticle thin films on semi-permeable cellulose substrate
- Authors: Sosibo, Ndabenhle , Mdluli, Phumlani , Mashazi, Philani N , Tshikhudo, Robert , Skepu, Amanda , Vilakazi, Sibulelo , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242638 , vital:51063 , xlink:href="https://doi.org/10.1016/j.matlet.2012.08.043"
- Description: This study reports the facile method for the deposition of gold nanoparticle thin film onto a monoporous semi-permeable cellulose membrane through the diffusion of borohydride ions leading to the reduction of AuCl4− ions. The synthesis of gold nanoparticle thin film was deposited on one side of the membrane that was exposed to AuCl4− ions while the other side containing a reducing agent remained clear. The gold nanoparticle thin film exhibited a broad surface plasmon resonance (SPR) peak at 529 nm. Various characterization techniques were employed and all demonstrated the presence of gold thin film. The reported method represents a simplistic method for the deposition of gold nanoparticle thin films and various other metal nanoparticles may be deposited following this method.
- Full Text:
- Date Issued: 2012
Agreement and coordination in XiTsonga, SeSotho and IsiXhosa: an optimality theoretic perspective
- Authors: Mitchley, Hazel
- Date: 2016
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/3423 , vital:20491
- Description: This thesis provides a unified Optimality Theoretic analysis of subject-verb agreement with coordinated preverbal subjects in three Southern Bantu languages: Xitsonga (S53), Sesotho (S33), and isiXhosa (S41). This analysis is then used to formulate a typology of agreement resolution strategies and the contexts which trigger them. Although some accounts in the Bantu literature suggest that agreement with coordinate structures is avoided by speakers (e.g. Schadeberg 1992, Voeltz 1971) especially when conjuncts are from different noun classes, I show that there is ample evidence to the contrary, and that the subject marker used is dependent on several factors, including (i) the [-HUMAN] specification on the conjuncts, (ii) whether the conjuncts are singular or plural, (iii) whether or not the conjuncts both carry the same noun class feature, and (iv) the order of the conjuncts. This thesis shows that there are various agreement resolution strategies which can beused: 1) agreement with the [+HUMAN] feature on the conjuncts, 2) agreement with the[-HUMAN] feature on the conjuncts, 3) agreement with the noun class feature on both conjuncts, 4) agreement with the noun class feature on the conjunct closest to the verb, and 5) agreement with the noun class feature on the conjunct furthest from the verb. Not all of these strategies are used by all languages, nor are these strategies interchangeable in the languages which do use them – instead, multiple factors conspire to trigger the use of a specific agreement strategy within a specific agreement featural context. I show that these effects can be captured using Optimality Theory (Prince and Smolensky 2004). The analysis makes use of seven constraints: RES#, MAX[+H], MAX[-H], DEP[-H], MAXNC, DEPNC, and AGREECLOSEST. The hierarchical ranking of these constraints not only accounts for the confinement of particular strategies to specific agreement featural contexts within a language, but also accounts for the cross-linguistic differences in the use of these strategies. I end off by examining the typological implications which follow from the OT analysis provided in this thesis.
- Full Text:
- Date Issued: 2016
An investigation of the indigenous ways of knowing about wild food plants (imifino): a case study
- Authors: Cimi, Phumlani Viwe
- Date: 2009
- Subjects: Wild plants, Edible -- South Africa -- Eastern Cape -- Case studies Endemic plants -- South Africa -- Eastern Cape -- Case studies Ethnoscience -- Study and teaching -- South Africa -- Eastern Cape Science -- Study and teaching -- South Africa -- Eastern Cape Curriculum change -- South Africa -- Eastern Cape Competency-based education -- South Africa -- Eastern Cape Conservation of natural resources -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1652 , http://hdl.handle.net/10962/d1003535
- Description: This study was conducted in Grahamstown in the Eastern Cape, South Africa. It is a qualitative case study located within the interpretive paradigm and was carried out over a period of a year. The theory implicit in the interpretive paradigm is of human beings as interpreters and constructors of a meaningful world. Thus, the focus of this study was on investigating the benefits of indigenous ways of knowing about wild food plants (imifino) in conjunction with hands-on activity-based lessons. This was done with the view to promote a conceptual understanding of nutrition and conservation in the Natural Sciences. The transformation of the school curriculum in South Africa called Curriculum 2005 (C2005) underpinned by the outcomes-based education (OBE) philosophy also triggered this study. The C2005 and OBE emphasise that learners’ prior everyday knowledge should be taken into account during the teaching and learning processes. The intention of the curriculum is to promote the idea of grounding knowledge in local contexts, while being sensitive to global imperatives. Although the acquisition of western knowledge has been and still is invaluable to all, on its own, it has been incapable of responding adequately to modern society in the face of massive and intensifying disparities, untrammeled exploitation of resources, and rapid depletion of the earth’s natural resources. Essentially, indigenous knowledge systems represent both a heritage and resource that should be protected, promoted, developed and, where appropriate, conserved. It is a resource that should serve the present and succeeding generations as many people’s cultural practices still rely on the use of wild plants. Within this context it should be borne in mind that the overexploitation of natural resources threatens not only biodiversity but also local traditional knowledge systems and ultimately cultural heritage; and research has a role to play in this regard. The research process in this study evolved into two main phases. The initial phase involved mobilising Grade 7 learners’ prior everyday knowledge on wild food plants (imifino). This led to the second phase of the research project, which was aimed at developing concepts through three hands-on activity-based lessons. I invited a community member to give a lesson on what imifino is and how to collect and prepare it, with the belief that the involvement of parents and community members in learners’ education can help bridge the gap between everyday life and school science. It is for these reasons that I believe that the constructive perspective can provide an appropriate methodological framework, conceptual structure and terminology for analysis of teaching and learning activities on the use of wild food plants in this study. The data generation techniques used in this study were questionnaires, observations and interviews (semi structured and focus group). A wide range of data generation techniques were employed to crystallise and validate the data generated using triangulation. The results from the analysed data revealed that consideration of indigenous ways of knowing in conjuction with hands-on practical activities enhanced interaction and learning among the learners. Also, linking of scientific knowledge to learners’ everyday lives was useful in fostering meaning-making and conceptual development.
- Full Text:
- Date Issued: 2009
Electrochemical impedimetric immunosensor for the detection of measles-specific IgG antibodies after measles infections
- Authors: Mashazi, Philani N , Tetyana, Phumlani , Vilakazi, Sibulelo , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7325 , http://hdl.handle.net/10962/d1020575
- Description: The detection of measles-specific primary antibodies (IgG) using electrochemical impedimetric immunosensors is reported. The optimum conditions for electrode saturation were reached after 40 min for 1 μg ml−1 antibody concentrations. Surface roughness using AFM increased with each immobilization or antigen-antibody reaction step clearly confirming the surface modification and recognition between antigen and antibody. The human serum (HS) and new-born calf serum (NCS) spiked with antigen-specific antibody were studied to mimic the real sample analysis. The HS and NCS sera containing antibodies due to measles exhibited correlation between the increasing antibody serum concentrations and the charge-transfer resistance (electrochemically measured). This work clearly showed the potential use of impedance as the preferred electrochemical method for detecting measles-antibodies in label-free manner. , Original publication is available at http://dx.doi.org/10.1016/j.bios.2013.04.028
- Full Text: false
Graduation Ceremony May 2009
- Authors: University of Fort Hare
- Language: English
- Type: text
- Identifier: vital:11985
- Description: University of Fort Hare Graduation programme Friday, 8th & Saturday, 9th May 2009.
- Full Text:
Boundary demarcation and community identity concerns: an investigation of the Matatiele boundary dispute
- Authors: Tyabazayo, Phumlani
- Date: 2013
- Subjects: Conflict management -- South Africa -- Matatiele , Identity politics -- South Africa -- Matatiele , Matatiele (South Africa) -- Boundaries
- Language: English
- Type: Thesis , Masters , MPhil
- Identifier: vital:8357 , http://hdl.handle.net/10948/d1021019
- Description: This treatise explores the Matatiele boundary demarcation dispute and, in particular, the role that unmet basic human needs play in this dispute. The subject of identity is also explored. In 2006, the government of South Africa decided that Matatiele should no longer be part of the province of Kwa-Zulu Natal (KZN) and instead should be incorporated into the province of the Eastern Cape. This decision divided the community of Matatiele into two groups; one was pro-KZN and the other, pro-Eastern Cape. In 2008, violence broke out between these two groups. The government’s decision and the resulting violence have created a situation of protracted conflict in the community of Matatiele with rivalries and antagonism being part of the fabric of the society. This treatise attempts to analyse this conflict and link it to the theory of basic human needs as advocated by conflict theorists such as John Burton and Johan Gultang. Human needs theorists hold the view that unmet psychological and physical needs are sources of social conflict and can lead to protracted conflict. This treatise also explores the efficacy of problem-solving workshops and referendums as conflict-resolution techniques for boundary demarcation disputes. The data were collected from unstructured, in-depth interviews with a sample of eleven respondents. The data indicate that there is a nexus between this conflict and the theory of basic human needs and that community-identity concerns are central to this dispute. The findings of this study suggest that the conflict is multi-faceted and that the underlying causes can be attributed to unmet human needs. The data was analysed using the grounded theory approach. This allowed the key causes of the conflict to be identified and subsequently informed the recommendations presented in the conclusion of this treatise.
- Full Text:
- Date Issued: 2013
Petrographic and geochemical characterisation of the hangingwall and the footwall rocks (the Dipeta and R.A.T. stratigraphic units) to the Kinsevere and Nambulwa copper ore deposits of the Lufilian Arc, southern Democratic Republic of Congo
- Authors: Nkulu, Robert Kankomba
- Date: 2020
- Subjects: Petrogenesis -- Congo (Democratic Republic) , Analytical geochemistry -- Congo (Democratic Republic) , Copper ores -- Congo (Democratic Republic) , Ore deposits -- Congo (Democratic Republic) , Katangan Sequence , Geological mapping -- Congo (Democratic Republic) , Central African Copperbelt (Congo and Zambia) , Lufilian Arc , Neoproterozoic Katangan R.A.T. (Roches Argilo Talqueuse) Subgroup , Dipeta Subgroup
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/142772 , vital:38115
- Description: The Kinsevere and Nambulwa copper deposits in the Democratic Republic of Congo (D.R.C.) are set in the eastern side of the Neoproterozoic Katanga Supergroup, forming the Lufilian Arc, resulting from a cratonic collision between the Congo and the Kalahari Cratons (ca.620-570_Ma). The Katanga Supergroup was deposited in an extensional rift setting with a sedimentary thickness succession ranging between 7 to 10 km, sub-divided into: − the Roan, the Nguba and the Kundelungu Groups. The stratigraphic column of the Roan Group consists of the R.A.T. (Roche Argilo Talqueuse), the Mines, the Dipeta and the Mwashya Subgroups. Three major deformation phases have been described characterised by complex multiphase tectonics related to a curved superposition of folded, thrust and sheared blocks. The rocks of the R.A.T., Mines and Dipeta Subgroups are recognised as blocks that occur within a stratiform to discordant and diapiritic megabreccia. The blocks were rafted upward with salt tectonics, resulting in the juxtaposition with the hangingwall and the footwall terranes. Therefore, in that context it has been found that the Dipeta may appear overlying the R.A.T. Subgroup through the unconformity decollement surface of heterogeneous breccia. The petrographic observations made of the R.A.T. and Dipeta samples indicates in both units the presence of detrital quartz and feldspar that have been altered and replaced by sericite and muscovite minerals. Gypsum is intimately associated with magnesite, showing an evaporitic environment domain, while magnesite is common as alteration phase both in the R.A.T. and Dipeta Subgroups. Pyrophyllite has been observed in the Dipeta, resulting from reaction of silica with the Kaolinite at low temperature. Accessory detrital minerals include zircon, as well as xenotime intergrown with altered Fe-Ti-oxide hematite, forming complex textures with disseminated Ti-oxides both in R.A.T. and Dipeta units. Major and trace element geochemistry indicates that the Dipeta is more dolomitic and magnesite while the R.A.T. is clay-rich. The Ti2O value of Dipeta and R.A.T samples is relatively low, ranging between 0.36 and 0.69 wt.% respectively, which suggest highly evolved felsic material in the protolith. This is consistent with interpretation based on the Al2O3/TiO2 ratio, which ranges between 18 and 23 for the R.A.T. and Dipeta respectively, indicating an intermediate to felsic granitoids as the protolith of R.A.T. and Dipeta siltstones. The Ti/Zr ratio of R.A.T. and Dipeta samples of less than 10, while, the higher La/Sc ratio of between 2.6 and 5.5 (for the R.A.T. and Dipeta respectively) indicate that both the R.A.T. and Dipeta are active continental and passive margin tectonic setting. Based on the geochemical variation with depth across the R.A.T. and Dipeta and their contact zone, a geochemical fingerprinting suggests that the ratio TiO2/Al2O3 appears to be useful and could be considered as a stratigraphic geochemical maker able to discriminate the R.A.T. and the Dipeta Subgroups during the geological mapping.
- Full Text:
- Date Issued: 2020
Electrochemical sensing and immunosensing using metallophthalocyanines and biomolecular modified surfaces
- Authors: Mashazi, Philani Nkosinathi
- Date: 2012
- Subjects: Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Measles -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5580 , http://hdl.handle.net/10962/d1018248
- Description: The synthesis of cobalt and manganese phthalocyanine complexes bearing eight hexylthio and four amino substituents was carried out. The formation of thin films of these complexes using different modification methods was also studied. Hexylthio functionalized metallophthalocyanine complexes were immobilized onto gold electrode surfaces using the self-assembly techniques. Surface modifications using cobalt and manganese tetraamino phthalocyanine as polymers, monolayers (onto electrografted surfaces) and as carbon nanotube – metallophthalocyanine conjugates was also carried out. The new method of modifying gold electrodes with metal tetraamino phthalocyanine complexes was investigated. The modified electrode surfaces were studied for their electrocatalytic properties and as potential electrochemical sensors for the detection of hydrogen peroxide (H₂O₂). The limits of detection for the H₂O₂ were of the orders of ~10⁻⁷ M for all the modified electrodes. The modified electrodes gave very good analytical parameters; such as good sensitivity, linearity at studied concentration range and well-defined analytical peaks with increased current densities. The modification methods were reproducible, highly conducting thin films were formed and the modified electrodes were very stable. The design of electrochemical immunosensors for the detection of measles-specific antibodies was also carried out. The modified surface with measles-antigen as sensing element was accomplished using covalent immobilization for an intimate connection of the measles-antigen as a sensing layer onto an electrode surface. Two methods of detecting measles-specific antibodies were investigated and these methods were based on electrochemical impedance, i.e. label-free detection, and voltammetric method using horse-radish peroxidase (HRP) labeled antibody as a reporter. The detection of measles-specific antibodies was accomplished using both these methods. The potential applications of the designed immunosensor were evaluated in real samples (human and newborn calf serum) and the electrodes could detect the antibodies in the complex sample matrix with ease.
- Full Text:
- Date Issued: 2012
Synthesis and characterisation of lanthanide complexes with nitrogen- and oxygen-donor ligands
- Authors: Madanhire, Tatenda
- Date: 2016
- Subjects: Rare earth metals
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/13127 , vital:27154
- Description: The reactions of Ln(NO3)3∙6H2O (Ln = Pr, Nd or Er) with the potentially tridentate O,N,O chelating ligand 2,6-pyridinedimethanol (H2pydm) were investigated, and complexes with the formula, [Ln(H2pydm)2(NO3)2](NO3) (Ln = Pr or Nd) and [Er(H2pydm)3](NO3)3 were isolated. The ten-coordinate Pr(III) and Nd(III) compounds crystallise in the triclinic space group P-1 while the nine-coordinate Er(III) complex crystallises in the monoclinic system (P21/n). The reaction of PrCl3∙6H2O with H2pydm yielded the compound, [Pr(H2pydm)3](Cl)3, that crystallises in the monoclinic system, space group P21/c with α = 90, β = 98.680(1) and γ = 90°. The nine-coordinate Pr(III) ion is bound to three H2pydm ligands, with bond distances Pr-O 2.455(2)-2.478(2) Å and Pr-N 2.6355(19)-2.64(2) Å. X-ray crystal structures of all the H2pydm complexes reveal that the ligand coordinates tridentately, via the pyridyl nitrogen atom and the two hydroxyl oxygen atoms. The electronic absorption spectra of complexes show 4f-4f transitions. Rare-earth complexes, [Ln(H2L1)2(NO3)3] [Ln = Gd, Ho or Nd], were also prepared from a Schiff base. The X-ray single-crystal diffraction studies and SHAPE analyses of the Gd(III) and Ho(III) complexes shows that the complexes are ten-coordinate and exhibit distorted tetradecahedron geometries. With proton migration occurring from the phenol group to the imine function, complexation of the lanthanides to the ligand gives the ligand a zwitterionic phenoxo-iminium form. A phenolate oxygen-bridged dinuclear complex, [Ce2(H2L1)(ovan)3(NO3)3], has been obtained by reacting Ce(NO3)3∙6H2O with an o-vanillin derived Schiff base ligand, 2-((E)-(1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H2L1). Hydrolysis of the Schiff base occurred to yield o-vanillin, which bridged two cerium atoms with the Ce∙∙∙Ce distance equal to 3.823 Å. The Ce(III) ions are both tencoordinate, but have different coordination environments, showing tetradecahedron and staggered dodecahedron geometries, respectively. The reaction of salicylaldehyde-N(4)-diethylthiosemicarbazone (H2L2) in the presence of hydrated Ln(III) nitrates led to the isolation of two novel compounds: (E)-2[(ortho-hydroxy)benzylidene]-2-(thiomethyl)-thionohydrazide (1) and bis[2,3-diaza4-(2-hydroxyphenyl)-1-thiomethyl-buta-1,3-diene]disulfide. The latter is a dimer of the former. For this asymmetric Schiff base, 1 and the symmetric disulfide, classical hydrogen bonds of the O–H∙∙∙N as well as N–H∙∙∙S (for 1) type are apparent next to C–H∙∙∙O contacts. 4-(4-Bromophenyl)-1-(propan-2-ylidene)thiosemicarbazide was also prepared upon reacting 4-(4-bromophenyl)-3-thiosemicarbazide with acetone in the presence of ethanol and La(NO3)3∙6H2O. The C=S bond length was found to be 1.6686(16) Å which is in good agreement with other thioketones whose metrical parameters have been deposited with the Cambridge Structural Database. Classical hydrogen bonds of the N–H∙∙∙N and the N–H∙∙∙Br type are observed next to C–H∙∙∙S contacts. All synthesised compounds were characterised by microanalyses, single-crystal X-ray diffraction (except for [Nd(H2L1)2(NO3)3]), 1H NMR and IR spectroscopy.
- Full Text:
- Date Issued: 2016
An investigation of parameter relationships in a high-speed digital multimedia environment
- Authors: Chigwamba, Nyasha
- Date: 2014
- Subjects: Multimedia communications , Digital communications , Local area networks (Computer networks) , Computer network architectures , Computer network protocols , Computer sound processing , Sound -- Recording and reproducing -- Digital techniques
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4725 , http://hdl.handle.net/10962/d1021153
- Description: With the rapid adoption of multimedia network technologies, a number of companies and standards bodies are introducing technologies that enhance user experience in networked multimedia environments. These technologies focus on device discovery, connection management, control, and monitoring. This study focused on control and monitoring. Multimedia networks make it possible for devices that are part of the same network to reside in different physical locations. These devices contain parameters that are used to control particular features, such as speaker volume, bass, amplifier gain, and video resolution. It is often necessary for changes in one parameter to affect other parameters, such as a synchronised change between volume and bass parameters, or collective control of multiple parameters. Thus, relationships are required between the parameters. In addition, some devices contain parameters, such as voltage, temperature, and audio level, that require constant monitoring to enable corrective action when thresholds are exceeded. Therefore, a mechanism for monitoring networked devices is required. This thesis proposes relationships that are essential for the proper functioning of a multimedia network and that should, therefore, be incorporated in standard form into a protocol, such that all devices can depend on them. Implementation mechanisms for these relationships were created. Parameter grouping and monitoring capabilities within mixing console implementations and existing control protocols were reviewed. A number of requirements for parameter grouping and monitoring were derived from this review. These requirements include a formal classification of relationship types, the ability to create relationships between parameters with different underlying value units, the ability to create relationships between parameters residing on different devices on a network, and the use of an event-driven mechanism for parameter monitoring. These requirements were the criteria used to govern the implementation mechanisms that were created as part of this study. Parameter grouping and monitoring mechanisms were implemented for the XFN protocol. The mechanisms implemented fulfil the requirements derived from the review of capabilities of mixing consoles and existing control protocols. The formal classification of relationship types was implemented within XFN parameters using lists that keep track of the relationships between each XFN parameter and other XFN parameters that reside on the same device or on other devices on the network. A common value unit, known as the global unit, was defined for use as the value format within value update messages between XFN parameters that have relationships. Mapping tables were used to translate the global unit values to application-specific (universal) units, such as decibels (dB). A mechanism for bulk parameter retrieval within the XFN protocol was augmented to produce an event-driven mechanism for parameter monitoring. These implementation mechanisms were applied to an XFN-protocol-compliant graphical control application to demonstrate their usage within an end user context. At the time of this study, the XFN protocol was undergoing standardisation within the Audio Engineering Society. The AES-64 standard has now been approved. Most of the implementation mechanisms resulting from this study have been incorporated into this standard.
- Full Text:
- Date Issued: 2014
One-stop haematuria clinic: First experience in South Africa
- Authors: J John,
- Date: 2017
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/5613 , vital:44616
- Full Text:
One-stop haematuria clinic: First experience in South Africa
- Authors: J John
- Date: 2019
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/3823 , vital:43951
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A study of a class of invariant optimal control problems on the Euclidean group SE(2)
- Authors: Adams, Ross Montague
- Date: 2011
- Subjects: Matrix groups Lie groups Extremal problems (Mathematics) Maximum principles (Mathematics) Hamilton-Jacobi equations Lyapunov stability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5420 , http://hdl.handle.net/10962/d1006060
- Description: The aim of this thesis is to study a class of left-invariant optimal control problems on the matrix Lie group SE(2). We classify, under detached feedback equivalence, all controllable (left-invariant) control affine systems on SE(2). This result produces six types of control affine systems on SE(2). Hence, we study six associated left-invariant optimal control problems on SE(2). A left-invariant optimal control problem consists of minimizing a cost functional over the trajectory-control pairs of a left-invariant control system subject to appropriate boundary conditions. Each control problem is lifted from SE(2) to T*SE(2) ≅ SE(2) x se (2)*and then reduced to a problem on se (2)*. The maximum principle is used to obtain the optimal control and Hamiltonian corresponding to the normal extremals. Then we derive the (reduced) extremal equations on se (2)*. These equations are explicitly integrated by trigonometric and Jacobi elliptic functions. Finally, we fully classify, under Lyapunov stability, the equilibrium states of the normal extremal equations for each of the six types under consideration.
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- Date Issued: 2011
An assessment of the performance appraisal system utilised for junior and middle level management within the South African National Defence Force
- Authors: Terblanche, Graham Martin
- Date: 2004
- Subjects: Middle managers -- Rating of -- South Africa , South Africa. National Defence Force Officials and employees Rating of
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10884 , http://hdl.handle.net/10948/148 , Middle managers -- Rating of -- South Africa , South Africa. National Defence Force Officials and employees Rating of
- Description: The research problem of this study was to assess the extent to which the appraisal system for junior and middle level managers in the South African National Defence Force (SANDF) met the requirements and guidelines for performance appraisal as stipulated in the literature. To achieve this objective, the following procedure was followed: · A survey of existing literature, related to performance appraisal, was conducted. The literature study focused on the requirements for an effective performance appraisal system, appraisal methods and appraisal errors. Attention was also focused on who should take responsibility for performance appraisal and the importance of regularly evaluating the performance appraisal system to meet the demands of a changing environment. The second part of the literature study dealt with the guidelines for establishing an effective appraisal system as well as performance management processes and cycles that are critical for the effectiveness of an appraisal system. The theoretical study formed the basis for the development of a survey questionnaire to establish the extent to which junior and middle level managers in the SANDF agreed with the theoretical guidelines. The survey was administered to a randomly selected group of junior and middle level managers who were representative of the South African Army, Airforce and Medical Services. The empirical results indicated that there was concurrence with many of the guidelines in the literature, but that there were areas that could be improved. It became evident that many respondents felt that the current system was not entirely fair and was not adapted to meet the needs of the integrated SANDF. Specifically, results indicated that the system should be re-evaluated to eliminate bias and to enhance the development of clear standards, both on a quantitative and qualitative level. It became clear that training and communication were important to the successful development and utilisation of a performance appraisal system. An effective performance appraisal system that is integrated with the overall performance management system of an organisation will enhance productivity, satisfaction and the attainment of goals.
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- Date Issued: 2004
Fungal remediation of winery and distillery wastewaters using Trametes pubescens MB 89 and the enhanced production of a high-value enzyme therein
- Authors: Strong, Peter James
- Date: 2008
- Subjects: Fungal remediation Distilleries -- Waste disposal Wine and wine making -- Waste disposal Bioremediation Laccase Enzymes -- Biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3932 , http://hdl.handle.net/10962/d1003991
- Description: In this study white-rot fungi were investigated for their efficiency at distillery wastewater remediation and the production of laccase as a valuable by-product. Distillery wastewaters are high in organic load and low in pH. The presence of phenolic compounds can lead to extremely colour-rich wastewaters and can be toxic to microorganisms. The presence of the inorganic ions may also affect biological treatment. White-rot fungi are unique among eukaryotic or prokaryotic microbes in possessing powerful oxidative enzyme systems that can degrade lignin to carbon dioxide. These ligninolytic enzymes, such as lignin peroxidase, manganese peroxidase and laccase, are capable of degrading a vast range of toxic, recalcitrant environmental pollutants and this makes the white-rot fungi strong candidates for the bioremediation of polluted soils and waters. The laccase enzyme alone has shown remediation potential in wastewaters such as beer production effluent, olive mill wastewater, alcohol distillery wastes, dye-containing wastewaters from the textile industry as well as wastewaters from the paper and pulp industry. It has been shown to be capable of remediating soils and waters polluted with chlorinated phenolic compounds, polyaromatic hydrocarbons, nitrosubstituted compounds and fungicides, herbicides and insecticides.
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- Date Issued: 2008
An interevention strategy for improving reading comprehension in grade 9: a case study in one secondary school in East london education district
- Authors: Fesi, Liziwe
- Date: 2015
- Subjects: English language -- Study and teaching -- South Africa -- Eastern Cape Reading comprehension -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/5905 , vital:29417
- Description: The study focused on strategies for improving reading comprehension skills at Grade 9 level through story writing in one secondary school in the East London Education District. Vygotskian theory formed the theoretical framework for this study, aligned with language theories as relevant literature for this particular research study. Data was generated from 15 Grade 9 learners who were selected from 3 Grade 9 classes using convenience sampling, comprising of five learners from Grade 9(a) intervention group, five learners from Grade 9(b) and five learners from Grade 9(c) non-intervention group who were selected for this study with the inclusion of two Grade 9 teachers and one Grade 8 teacher. Involvement of the grade 8 teacher is relevant to determine the voice from a Grade 8 teacher as an informed voice, which filtered into understanding how and why Grade 9 learners are unable to read and write with understanding in their present grade. The teachers were given three questions for semi-structured interviews. All the learners were given a specific activity as a pre-assessment without intervention strategy. The Grade 9(a), which is the intervention class, used story writing as an intervention strategy where they began a two week study using intensive intervention strategies, amounting to a total of 18 weeks study from pre-assessment to post-assessment. At the conclusion of the study the selected learners undertook a post-assessment using the same specific activity as in the pre-assessment. Subsequently, these selected Grade 9 learners’ reading comprehension pre-assessment and post-assessment was analysed. Five of the grade 9(a) learners demonstrated significant improvement in the intervention activities they were given. Grade 9(b) and Grade 9(c) showed difficulty in the post-assessment as they were the non-intervention group. It was concluded that Grade 9(a) learners performed better in the post-assessment. This could be attributed to the use of story writing as an intervention strategy to improve their English reading and reading comprehension skills. Keywords: intervention, reading, comprehension.
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- Date Issued: 2015