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Spectroscopic behavior of cationic metallophthalocyanines in the presence of anionic quantum dots

  • Authors: Idowu, Mopelola A I , Nyokong, Tebello
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/262699 , vital:53545 , xlink:href="https://doi.org/10.1016/j.saa.2009.10.050"
  • Description: The interactions and spectroscopic properties between cationic zinc phthalocyanine derivatives (peripherally and non-peripherally tetrasubstituted and peripherally octa substituted with 2-diethylmethylaminoethylsulfanyl (βTZnPc, αTZnPc and βOZnPc)) and CdTe core quantum dots (QDs) capped with mercaptopropionic acid or thioglycolic acid (represented as CdTe@MPA and CdTe@TGA, respectively) have been studied in methanol:water mixture. Strong coupling of MPcs was deduced from the interaction since the UV–vis spectroscopic studies of the ground state complex formed on mixing both components showed loss of the phthalocyanine monomeric band with the formation of a dimeric band (spectrum of aggregated species). The dimerization constants were of the order of 104 M−1.
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  • Date Issued: 2010

Spectroscopic studies of nanostructures of negatively charged free base porphyrin and positively charged tin porphyrins

  • Authors: George, Reama C , Egharevba, Gabriel O , Nyokong, Tebello
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/261661 , vital:53432 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.028"
  • Description: Spectroscopic studies were carried out on the homoaggregates of negatively charged free base meso-tetraphenylsulfonated porphyrin ([H2TPPS4]4−) and heteroaggregates of a mixture of protonated ([H4TPPS4]2−) and tin meso-tetra (N-methyl-4-pyridyl) porphyrin ([SnTMPyP]4+). The spectroscopic studies were done to determine the optimal conditions required for the fabrication of porphyrin nanorods by ionic self assembly of two oppositely charged porphyrins. In addition, the various spectral changes of [H4TPPS4]2− with concurrent change in pH and concentration are also investigated. In acid media at pH more than 3, and at concentrations less than 1 × 10−5 M, [H4TPPS4]2− molecules form J aggregates. A mixture of [H4TPPS4]2− and [SnTMPyP]4+ forms heteroaggregates of the J type in acid media. At pH’s 2 to 3, the optimum ratio for the formation of J aggregates is 3:1 and for pH 1, the optimum ratio is 2:1. Transmission electron microscope images of the nanostructures formed show that they are of cylindrical shape.
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  • Date Issued: 2010

Statistical methods to model the influence of age and gender on the behavioral risk factors of HIV/AIDS

  • Authors: Tlou, Boikhutso
  • Date: 2010
  • Subjects: AIDS (Disease) -- Statistics , HIV infections -- Statistics , AIDS (Disease) -- South Africa , Health risk assessment , HIV infections -- South Africa , AIDS (Disease) -- Social aspects
  • Language: English
  • Type: Thesis , Masters , MSc (Biostatistics and Epidemiology)
  • Identifier: vital:11779 , http://hdl.handle.net/10353/400 , AIDS (Disease) -- Statistics , HIV infections -- Statistics , AIDS (Disease) -- South Africa , Health risk assessment , HIV infections -- South Africa , AIDS (Disease) -- Social aspects
  • Description: The effects of gender and age on the behavioral risk of HIV/AIDS are not clearly understood as previous distinct studies which have been carried out, have given disputable and contradictory outcomes. This study therefore, discusses the statistical methods which can be used to model the influence of age and gender on the behavioral risk factors of HIV/AIDS. In general, generalized linear models are the main methods which can be applied to depict the impact of age and gender on the behavioral risk of becoming infected with HIV/AIDS virus. In this study, the main methods used were logistic regression, log-linear regression and multiple regressions. Behavioral risk was taken as the dependent variable while age, gender, number of sexual partners, religious beliefs and alcohol and drug abuse were fitted as predictor variables. The three statistical methods gave significant results for gender and insignificant results for age. Furthermore, comparisons were made on the three regression methods and the logistic regression gave the best results. It was therefore concluded that gender plays a significant role on the behavioral risk of HIV/AIDS. The results of the study showed that gender of the student and number of sexual partners had a significant effect on the risk behavior of the university students. In future, it may be very important to find out why age is not a significant factor on risk behavior of HIV/AIDS among university students.
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  • Date Issued: 2010

Stock farmers and the state: a case study of animal healthcare practices in Hertzog Eastern Cape Province South Africa

  • Authors: Jenjezwa, Vimbai Rachel
  • Date: 2010
  • Subjects: Agriculture and state -- South Africa -- Eastern Cape , Traditional veterinary medicine -- South Africa -- Eastern Cape , Animal health , Domestic animals -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc (Geography)
  • Identifier: vital:11508 , http://hdl.handle.net/10353/269 , Agriculture and state -- South Africa -- Eastern Cape , Traditional veterinary medicine -- South Africa -- Eastern Cape , Animal health , Domestic animals -- South Africa -- Eastern Cape
  • Description: The animal healthcare practices of most communal farmers involve the use of both conventional and ethnoveterinary medicines. This study presents information on the animal healthcare practices of stock farmers in Hertzog, Eastern Cape Province, South Africa. It also presents the findings on the social, economic and political aspects surrounding animal healthcare. The research applied two theories namely structuration theory and the Context, Practice and Belief (CPB) framework. Interviews and participant observation were used to collect data. The communal farmers widely used conventional medicines however, proper administration methods were not followed. Ethnoveterinary medicines were used to prevent and treat disease, even by the younger stock farmers. The stock farmers used ethnoveterinary medicines mainly because of the lack of finance to purchase the conventional medicines, even though the latter was preferred. The stock farmers actively participated in state programmes but felt that they needed more state veterinarian visits and state provided medications because they could not afford private veterinarians and conventional medicines. Therefore, this study attempts to contribute to an understanding of the use of ethnoveterinary medicine and communal farmers’ animal healthcare practices.
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  • Date Issued: 2010

Strategic management guidelines for construction SMEs in the Eastern Cape

  • Authors: Appels, Gaynor
  • Date: 2010
  • Subjects: Construction industry -- Management , Strategic planning
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: vital:8663 , http://hdl.handle.net/10948/1414 , Construction industry -- Management , Strategic planning
  • Description: SMEs fulfil an important role in the long-term growth and development of the economy of the country. The development and growth of construction SMEs are important for all countries, as a strong SME base has the capacity to produce a high-quality infrastructure for the country. Construction SMEs also stimulate economic activity in other sectors of the economy. Research has, however, shown that the failure rate of small businesses within the first five years is high in South Africa. Reseatch has also indicated that the lack of long-term planning and the lack of strategic thinking are major contributing factors to the business failure of SMEs. SMEs operating in the construction industry are faced with the same challenges as their counterparts in other sectors of the economy, but in addition to those difficulties, construction SMEs also have to deal with the unique characteristics of the industry that have adverse implications for them. The construction industry has experienced considerable growth and success, in the past decade, particularly as a result of the government's considerable infrastructural spending, especially in the run-up to the 2010 FIFA World Cup. The growth in the construction industry has, however, not resulted in similar results for Construction SMEs; and research has shown that most of them have not developed into more established entities. In fact, in the Eastern Cape, 91 per cent of all registered contractors fall within the lowest level of the Construction Industry Development Board's classification system. Many construction SMEs perform poorly, but among them there are those that have the potential to grow and develop into larger more established entities. Research has shown that contractor development programmes aimed at assisting the growth and development of construction companies have been successful in increasing participation in the industry, but not in ensuring that small enterprises grow into self-sustainable established enterprises. In contrast, the research has shown that SMEs that practice strategic management perform better, and that there are many advantages for SMEs in applying strategic management principles. This study, therefore, investigates how strategic management can be applied to address the problems faced by construction SMEs, and to exploire techniques and tools of strategic management that can make a significant contribution to their growth and development.
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  • Date Issued: 2010

Structure and functioning of fish assemblages in two South African estuaries, with emphasis on the presence and absence of aquatic macrophyte beds

  • Authors: Sheppard, Jill Nicole
  • Date: 2010
  • Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5321 , http://hdl.handle.net/10962/d1005166 , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape
  • Description: Temporarily open/closed estuaries (TOCEs) are the dominant estuary type in South Africa. These systems are often characterized by extensive beds of submerged macrophytes, which form important foraging and shelter habitats for fishes, especially for estuary-dependent fish species such as the Cape stumpnose Rhabdosargus holubi and Cape moony Monodactylus falciformis that are commonly associated with them. A loss of submerged macrophytes from an estuary has been shown to affect the fish community as well as reducing overall system productivity. The TOC East Kleinemonde Estuary, situated in the warm-temperate biogeographic region of South Africa has been subject to an ongoing long-term fish monitoring project since 1995. During the period 1995 to 2002, this estuary contained large beds of the submerged macrophytes Ruppia cirrhosa and Potamogeton pectinatus. However, subsequent to a major flood event in 2003 these macrophytes have been largely absent from this system. The effect of the loss of submerged macrophytes on the East Kleinemonde fish assemblage was investigated through an analysis of seine and gill net catch data. Seine net catches for a 12 year period, encompassing six years of macrophyte presence and six years of macrophyte senescence, revealed changes in the relative abundance of certain fish species. Vegetation-associated species such as R. holubi and M. falciformis decreased in abundance whereas sediment-associated species, especially members of the family Mugilidae, increased in abundance following loss of the macrophytes in this estuary. The critically endangered pipefish Syngnathus watermeyeri was only recorded in catches during years in which macrophyte beds were present. In addition to the analysis of catch data, the importance of macrophytes as a primary energy source for selected estuarine fishes was explored through the analysis of carbon and nitrogen stable isotopes. Prior to conducting these analyses, common methodological practices to address the presence of carbonates and lipids within isotope samples were evaluated. A subset of samples were either acid washed to remove carbonates, or lipids were removed according to the method of Bligh and Dyer (1959) as both of these compounds have been shown to affect stable carbon and nitrogen isotope ratios. The suitability of the lipid normalization models of Fry (2002) and Post et al. (2007) for samples of estuarine fish muscle were also tested. Based on this evaluation both models are suitable for use with estuarine fish muscle tissue, however since neither carbonate nor lipid content of any of the samples used in this study was high all samples were left untreated in the following analysis. Carbon isotope ratios from a wide range of fish species collected from the East Kleinemonde Estuary during the macrophyte-senescent phase were compared with individuals of the same species from the neighbouring West Kleinemonde Estuary (where extensive beds of R. cirrhosa and P. pectinatus were present) and revealed the influence of submerged macrophyte material in the diet of fishes in the latter system. However, it was apparent that these plants are not directly consumed but rather contribute to the detrital pool that forms a food source for most invertebrate and some fish species. The most significant source of carbon for East Kleinemonde fishes during the macrophyte senescent phase appeared to have a more depleted origin; probably from benthic or pelagic microalgae. In conclusion, while the importance of macrophyte beds as shelter and foraging habitats for estuarine fishes are well documented, their role in terms of the structuring and functioning of fish assemblages in TOCEs remains somewhat uncertain. The findings of this study were possibly masked by the resilience of vegetation-associated species to the loss of this habitat, as well as by life history characteristics of species such as R. holubi that allow their numerical dominance despite habitat change. Nonetheless, macrophyte senescence in the East Kleinemonde Estuary resulted in the loss of at least one species and the reduced abundance of vegetation-associated species, probably reflective of reduced food resources and/or increased vulnerability to predation. As a result, beds of submerged macrophytes are an important habitat within TOCEs.
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  • Date Issued: 2010

Studies on mixed-species colonies of honeybees, Apis cerana and Apis mellifera

  • Authors: Yang, Ming-Xian
  • Date: 2010
  • Subjects: Bees Apis cerana Honeybee Honeybee -- Behavior Bee culture Honeybee -- Physiology Insect societies Animal communication Bees -- Nests
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5779 , http://hdl.handle.net/10962/d1005467
  • Description: The honeybees Apis cerana and Apis mellifera are derived from the same ancestral base about two million years ago. With speciation and evolution, they have acquired many advanced living skills in common, but have also evolved very different living strategies due to different distributions. This thesis is an intensive study of the biology of the mixed-species colonies of these species, the aims of which were to investigate their behavioural relationships and uncover the evolutionary conserved features of their behaviours subsequent to speciation. The results show that the two species can form a stable society to perform normal tasks. First, workers of both species in the mixed-colonies could form the typical retinue behaviour to hetero-species queens, thus indicating that queen pheromones could be spread to and by both species. Secondly, both species did not show significantly different ovarian activation under hetero-species queens, suggesting that the queen pheromones more likely play a role of "honest signal" rather than a "repression" substance in the honeybee colonies. Thirdly, both species could mutually decode each other‘s waggle dances, with unexpectedly low misunderstanding; revealing that the dance language in a dark environment is quite adaptive for cavity-nesting honeybees. Fourthly, workers of both species could cooperate with each other in comb construction, although the combs they built contain many irregular cells. Interestingly, A. cerana workers could be stimulated by A. mellifera workers to perform this task, thus confirming self-organization theory in the colony. Fifthly, A. mellifera workers behaved more "defectively" in thermoregulation, but perhaps because A. cerana workers are more sensitive to changes in hive temperature. Given these differences in strategy, A. mellifera workers‘ performance might in fact reduce conflicts. Lastly, when faced with threats of predatory wasps, both species engaged in aggressive defence. Although they did not learn from each other‘s responses, species-specific strategies were adopted by each of them so that the defence of the mixed-colonies is very effective. I conclude that the two species can adapt to each other‘s efforts and task allocation is reasonably organized allowing mixed-species colonies to reach stability. These results suggest that all of the social behaviours discussed here were highly conserved following speciation. This thesis could provide some clues for the study of honeybee evolution from open-nesting to the transition of cavity-nesting.
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  • Date Issued: 2010

Studies on the nutritional value of seven accessions of cocoyam growing in South Africa

  • Authors: Lewu, Muinat Nike
  • Date: 2010
  • Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
  • Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
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  • Date Issued: 2010

Studies towards the development of novel HIV-1 integrase inhibitors

  • Authors: Lee, Yi-Chen
  • Date: 2010
  • Subjects: HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Nuclear magnetic resonance , Heterocyclic compounds -- Derivatives , Enzyme inhibitors , Chemical inhibitors , Quinoline
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4357 , http://hdl.handle.net/10962/d1005022 , HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Nuclear magnetic resonance , Heterocyclic compounds -- Derivatives , Enzyme inhibitors , Chemical inhibitors , Quinoline
  • Description: The project has focused on the preparation of several series of compounds designed as potential HIV-1 integrase inhibitors. Various 2-nitrobenzaldehydes have been reacted with two activated alkenes, methyl vinyl ketone (MVK) and methyl acrylate, under Baylis-Hillman conditions to afford α-methylene-β-hydroxylalkyl derivatives in moderate to excellent yields. The reactions were conducted using the tertiary amine catalysts, 1,4-diazabicyclo[2.2.2]octane(DABCO) or 3-hydroxyquinuclidine (3-HQ) with chloroform as solvent, and yields were optimised by varying the catalyst, reagent concentrations and the reaction time. Reductive cyclization of the Baylis-Hillman adducts via catalytic hydrogenation, using 10% palladiumon-carbon catalyst in ethanol, afforded quinoline and quinoline N-oxide derivatives. In some cases “acyclic” reduction products were also isolated. Reaction of the Baylis-Hillman MVK adducts with HCl, has resulted in effective nucleophilic (SN’) displacement of the hydroxyl group to afford allylic chloride derivatives. Direct substitution of these chloro derivatives by secondary or primary amines, followed by catalytic hydrogenation gave quinoline derivatives containing a 3-aminomethyl substituent. The Baylis-Hillman ester adducts obtained from reaction with methyl acrylate were treated directly with various amines to give diastereomeric conjugate addition products. Reactions with piperazine gave N,N’-disubstituted piperazine products. The piperidine derivatives have been dehydrated to give cinnamate esters in moderate yields. The products, which have all been satisfactorily characterised by elemental (HRMS) and spectroscopic (1- and 2-D NMR) analysis, constitute a “library” of compounds for in silico and in vitro studies as potential HIV integrase inhibitors.
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  • Date Issued: 2010

Study South Africa

  • Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
  • Date: 2010
  • Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/64963 , vital:28640 , ISBN 9780620482172
  • Description: [Extract from message from Minister of Higher Education and Training, Hon. Dr BE Nzimande]: The 10th Edition focuses on the highly relevant issue of ‘Higher Education Internationalisation in the Development of Africa’. The internationalisation of higher education is of great importance for the continent, if Africa wants to be able to compete and participate in a global context. Currently, there are only three African institutions in the Top 500 of the Shanghai Academic Ranking of World Universities and all of these are in South Africa. Similarly, one South African institution appears in the Top 200 of the Times Higher Education World Ranking and no other African universities are represented. Despite being cautious about the methodology used to derive rankings, our aim in higher education should be to actively compete internationally and, more importantly, to serve the developmental challenges of Africa. It is imperative that Africa engages internationally and participates in the development of humanity’s knowledge. Research outputs and publications are particularly low on the continent, and African universities need to develop their research capabilities and direct resources to this important function. It is particularly important that research, which affects Africa and its development, is conducted on a large scale on the continent, supported by collaborative work and partnerships, rather than being carried out predominantly in other countries. The time has come for the tide to change and for our researchers and academics to focus on research opportunities presented on the continent. This is an important step for Africa to take if it is to deal effectively with the problems it faces and take its place in the international arena. One way to increase and develop knowledge outputs is through collaboration. An important opportunity for South African universities is the Erasmus Mundus Programme funded through the European Union (EU). This programme encourages collaboration between South African and European universities and provides resources for the exchange of staff and students within specific research programmes. It is also important for Africa to develop the research collaboration within the continent and with other developing and developed countries. In this regard, the Intra-ACP (Africa-Caribbean-Pacific) Scheme is of great importance. This initiative by the African Union (AU), working in collaboration with the EU, provides the opportunity for academic staff and student exchanges between universities in these regions. Intra-African exchanges are of particular importance in developing the continent’s capacity. Through such programmes African universities can work together to develop research and participate in the knowledge economy. We should also not ignore the challenges faced in improving the quality of teaching and learning in African universities, including many in South Africa. If sufficient attention and resources are not directed to improving these most basic activities of higher education, we will not only fail to meet the continent’s human resource development needs, but we will fail to establish the basis for future research advancement. Student mobility is very much a part of our fabric and provides the necessary intellectual stimulation, which is an essential part of student life. The number of African students from outside South Africa studying at South African institutions is growing annually, as is the number of non-African students. The networks established through such internationalisation are invaluable. There are also large numbers of our own students who, through universities’ reciprocal agreements, are studying abroad. The information provided in this publication provides a valuable opportunity to showcase our higher education sector and goes a long way to providing the necessary facts to encourage such student mobility. , 10th Edition
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  • Date Issued: 2010

Suitability of the leaf-mining fly, Pseudonapomyza sp. (Diptera: Agromyzidae), for biological control of Tecoma stans L. (Bignoniaceae) in South Africa

  • Authors: Madire, Lulama Gracious
  • Date: 2010
  • Subjects: Diptera -- Biological control , Bignoniaceae -- Biological control , Plants, Ornamental -- Diseases and pests , Agromyzidae
  • Language: English
  • Type: Thesis , Masters , MSc (Zoology)
  • Identifier: vital:11790 , http://hdl.handle.net/10353/255 , Diptera -- Biological control , Bignoniaceae -- Biological control , Plants, Ornamental -- Diseases and pests , Agromyzidae
  • Description: Tecoma stans (L.) Juss. Ex Kunth (Bignoniaceae) also known as yellow bells, has a native distribution from Northern Argentina, central America, Mexico and the Southern USA. In many warm climatic regions of the world, T. stans is commonly planted as an ornamental plant because of its yellow flowers, hence the name yellow bells, and pinnate foliage. As a result, this evergreen shrub has wide distribution in the tropical and subtropical parts of the western hemisphere. As is the case in many other parts of the world, T. stans was introduced into South Africa as an ornamental plant, but escaped cultivation and now invades roadsides, urban open spaces, watercourses, rocky sites in subtropical and tropical areas of five South African provinces; Gauteng, Mpumalanga, Limpopo, KwaZulu-Natal, Eastern Cape and neighboring countries. Tecoma stans has the potential of extending its range because its seeds are easily dispersed by wind. The purpose of this work was to carry out pre-release efficacy studies to determine the host specificity and suitability of Pseudonapomyza sp. (Diptera: Agromyzidae), a leaf-mining fly, as a biological control agent of T. stans. Available information suggests that the fly was brought to South Africa (SA) from Argentina in 2005. In that year a worker collected adult root feeding fleabeetles from T. stans and their eggs by collecting soil around the plants in the Argentinian Province of Jujuy, at San Pedro (24°12’592”S, 64°51’328”W). The soil was brought to the SA quarantine laboratory of the Agricultural Research Council, Plant Protection Research Institute (Weeds Division), Pretoria, and placed in a cage containing T. stans plants for flea-beetle larvae to emerge from the eggs. The Pseudonapomyza sp. flies which emerged from that soil were reared to produce a colony of flies used in the study reported here. The feeding behavior of Pseudonapomyza sp. adults is initiated by females which use their ovipositor to puncture holes in the leaf mesophyll and then they feed on the sap oozing from the holes. Since males have no means of puncturing the leaves, they feed from holes made by females. Eggs are laid singly into the tubular leaf punctures. Soon after hatching, the larva feeds on the leaf mesophyll tissue. As the larva feeds within the leaf it creates mines which eventually coalesce to form large blotches. The damaged leaf area reduces the photosynthetic potential of the plant especially when damaged leaves dry and fall off the plants. The potential of Pseudonapomyza sp. as a biocontrol agent is enhanced by the fact that it has a high level of fecundity and a short life cycle. As a result, its populations can build up rapidly to exert a significant impact on T. stans. Host-specificity tests undertaken on 35 plant species in 12 plant families showed that out of the 35 plant species tested, the fly was able to develop on T. stans only. Although Pseudonapomyza sp. adults fed on T. capensis, a South African indigenous ornamental shrub, no larval mines were observed on this plant. This suggests two possibilities; either females of Pseudonapomyza sp. do not oviposit on T. capensis or oviposition takes place but larvae cannot feed and develop on this plant. These studies indicate that this fly is sufficiently host-specific, and can be released against T. stans without posing any threat to either commercial or indigenous plant species grown in South Africa. Experimental designs simulating high populations of Pseudonapomyza sp. showed that the impact of leaf mining fly on T. stans can cause approximately 56 percent aboveground biomass reduction. Other concurrent studies have also showed that low and high density fly infestations can cause 23 percent and 48 percent belowground biomass reductions, respectively. Based on the available information, it appears that Pseudonapomyza sp. may have the potential to reduce the invasive capacity of T. stans in the affected areas. In order to exert more herbivore pressure on T. stans, it is suggested that agents belonging to other feeding guilds, such as root-, stem- and seed-feeding insects, be considered for release to complement the leaf-feeding of Pseudonapomyza sp. An application to release this fly in SA has been submitted to one of the two regulatory authorities.
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  • Date Issued: 2010

Sunday Times: Celebrating Women

  • Authors: Sunday Times
  • Date: 2010
  • Subjects: Nyokong, Tebello
  • Language: English
  • Type: Article , text
  • Identifier: vital:7187 , http://hdl.handle.net/10962/d1006279 , Nyokong, Tebello
  • Description: A passion for light drove Professor Tebello Nyokong of Rhodes University into her photodynamic therapy research, harnessing light for cancer therapy and environmental clean-up using special dyes. And with this groundbreaking work she won the Africa-Arab State 2009 L'Oreal UNESCO Award for Women in Science.
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  • Date Issued: 2010

Surveillance of invasive vibro species in discharged aqueous efflents of wastewater treatment plants in the Eastern Cape province of South Africa

  • Authors: Igbinosa, Etinosa Ogbomoede
  • Date: 2010
  • Subjects: Vibrio -- South Africa -- Eastern Cape , Water -- Fluoridation -- South Africa -- Eastern Cape , Water -- Pollution -- South Africa -- Eastern Cape , Effluent quality -- South Africa -- Eastern Cape , Water -- Purification -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD (Microbiology)
  • Identifier: vital:11267 , http://hdl.handle.net/10353/245 , Vibrio -- South Africa -- Eastern Cape , Water -- Fluoridation -- South Africa -- Eastern Cape , Water -- Pollution -- South Africa -- Eastern Cape , Effluent quality -- South Africa -- Eastern Cape , Water -- Purification -- South Africa -- Eastern Cape
  • Description: Vibrio infections remain a serious threat to public health. In the last decade, Vibrio disease outbreaks have created a painful awareness of the personal, economic, societal, and public health costs associated with the impact of contaminated water in the aquatic milieu. This study was therefore designed to assess the prevalence of Vibrio pathogens in the final effluents of wastewater treatment plants (WWTPs) in the Eastern Cape Province, as well as their abilities to survive the treatment processes of the activated sludge system either as free cells or as plankton-associated entities in relation to the physicochemical qualities of the effluents. Three wastewater treatment facilities were selected to represent typical urban, sub-urban and rural communities, and samples were collected monthly from August 2007 to July 2008 from the final effluent, discharge point, 500 meter upstream and downstream of the discharge points and analysed for physicochemical parameters, Vibrio pathogens prevalence and their antibiogram characteristics using both culture based and molecular techniques. Physicochemical parameters measured include pH, temperature, electrical conductivity, salinity, turbidity, total dissolved solid (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), nitrate, nitrite and orthophosphate levels. Unacceptably high levels of the assayed parameters were observed in many cases for COD (<10 - 1180 mg/l), nitrate (0.08 - 13.14 mg NO3- as N/l), nitrite (0.06 - 6.78 mg NO2- as N/l), orthophosphate (0.07-4.81 mg PO43- as P/l), DO (1.24 - 11.22 mg/l) and turbidity (2.04 -159.06 NTU). Temperature, COD and nitrite varied significantly with season (P < 0.05), while pH, EC, salinity, TDS, COD, and nitrate all varied significantly with sampling site (P < 0.01; P < 0.05). In the rural wastewater treatment facility, free-living Vibrio densities varied from 0 to 3.45 × 101 cfu ml-1, while the plankton-associated Vibrio densities vary with plankton sizes as follows: 180 μm (0 – 4.50 × 103 cfu ml-1); 60 μm (0 – 4.86 × 103 cfu ml-1); 20 μm (0 – 1.9 × 105 cfu ml-1). The seasonal variations in the Vibrio densities in the 180 and 60 μm plankton size samples were significant (P < 0.05), while the 20 μm plankton size and free-living vibrios densities were not. Molecular confirmation of the presumptive vibrios isolates revealed V. fluvialis (36.5 percent), as the predominant species, followed by V. vulnificus (34.6 percent), and V. parahaemolyticus (23.1 percent), and V. metschnikovii (5.8 percent) (detected using only API 20 NE), suggesting high incidence of pathogenic Vibrio species in the final effluent of the wastewater facility. Correlation analysis suggested that the concentration of Vibrio species correlated negatively with salinity and temperature (P < 0.001 and P < 0.002 respectively) as well as with pH and turbidity (P < 0.001), in the final effluent. Population density of total Vibrio ranged from 2.1 × 101 to 4.36 × 104 cfu ml-1 and from 2.80 ×101 to 1.80 × 105 cfu ml-1 for the sub-urban and urban communities treatment facilities respectively. Vibrio species associated with 180 μm, 60 μm, and 20 μm plankton sizes, were observed at densities of 0 - 1.36 × 103 cfu ml-1, 0 - 8.40 × 102 cfu ml-1 and 0 - 6.80 × 102 cfu ml-1 respectively at the sub-urban community‘s WWTP. In the urban community, counts of culturable vibrios ranged from 0 - 2.80 × 102 cfu ml-1 (180 μm); 0 - 6.60 × 102 cfu ml-1 (60 μm) and 0 -1.80 × 103 cfu ml-1 (20 μm). Abundance of free-living Vibrio species varied between 0 and the orders of 102 and 103 cfu ml-1 in the sub-urban and urban communities WWTPs respectively. Molecular confirmation of the presumptive vibrios isolates revealed the presence of V. fluvialis (41.38 percent), V. vulnificus (34.48 percent), and V. parahaemolyticus (24.14 percent) in the sub-urban community effluents. In the urban community V. fluvialis (40 percent), V. vulnificus (36 percent), and V. parahaemolyticus (24 percent) were detected. There was no significant correlation between Vibrio abundance and season, either as free-living or plankton-associated entities, while Vibrio species abundance correlated positively with temperature (r = 0.565; P < 0.01), salinity and dissolved oxygen (P < 0.05). Turbidity and pH showed significant seasonal variation (P < 0.05) in both locations. The Vibrio strains showed the typical multi-antibiotic-resistance of an SXT element. They were resistant to sulfamethoxazole (Sul), trimethoprim (Tmp), cotrimoxazole (Cot), chloramphenicol (Chl) and streptomycin (Str), as well as other antibiotics such as ampicillin (Amp), penicillin (Pen), erythromycin (Ery), tetracycline (Tet), nalidixic acid (Nal), and gentamicin (Gen). The antibiotic resistance genes detected includes dfr18 and dfrA1 for trimethoprim; tetA, strB, floR, sul2 blaP1, for tetracycline, streptomycin, chloramphenicol, sulfamethoxazole and β-lactams respectively. A number of these genes were only recently described from clinical isolates, demonstrating genetic exchange between clinical and environmental Vibrio species. This study revealed that there was an adverse impact on the physicochemical characteristics of the receiving watershed as a result of the discharge of inadequately treated effluents from the wastewater treatment facilities. The occurrence of Vibrio species as plankton-associated entities confirms the role of plankton as potential reservoir for this pathogen. Also the treated final effluents are reservoirs of various antibiotics resistance genes. This could pose significant health and environmental risk to the biotic component of the environment including communities that rely on the receiving water for domestic purposes and may also affect the health status of the aquatic milieu in the receiving water. There is need for consistent monitoring programme by appropriate regulatory agencies to ensure compliance of the wastewater treatment facilities to regulatory effluent quality standards.
  • Full Text:
  • Date Issued: 2010

Sustainable agricultural development in the Malawian smallholder agricultural sector: a case of Lilongwe District

  • Authors: Chizimba, Martha
  • Date: 2010
  • Subjects: Food security -- Malawi , Poverty -- Malawi , Sustainable agriculture -- Malawi Case studies , Sustainable development -- Malawi Case studies , Agriculture -- Malawi
  • Language: English
  • Type: Thesis , Masters , M Soc Sc (Dev)
  • Identifier: vital:11420 , http://hdl.handle.net/10353/365 , Food security -- Malawi , Poverty -- Malawi , Sustainable agriculture -- Malawi Case studies , Sustainable development -- Malawi Case studies , Agriculture -- Malawi
  • Description: Even though agriculture is the backbone of Malawi‟s economy, food insecurity has remained a continuous threat among the poor. Until the 1980s, Malawi had been achieving national food security through an extensive system of agricultural inputs and marketing subsidies. However, these subsidies were removed and at the same time, the agricultural credit system collapsed. Consequently, agricultural productivity in Malawi remained low, poverty remained pervasive and food insecurity remains a main constraint to national and household food security. Therefore, the success of the agricultural sector in Malawi is very critical for raising the living standards and for food self-sufficiency. In this vein, the study hypothesized that Malawi can only achieve sustainable agricultural development if its agricultural policies are focused towards intensifying agricultural productivity through active participation of smallholder farmers. The major aim of the study was to contribute towards an improved understanding of how the issues of sustainable agricultural development have been addressed in Malawi and how they have influenced the lives of smallholder farmers. The analysis of the results revealed that even though what was implemented in the 1970s to early 1980s was financially unsustainable, but it provided some solutions to the fundamental challenges of smallholder development in Malawi. However, the liberalisations eroded whatever economic benefits achieved then. Never the less, the re-introduction of the agricultural input subsidies restored back the means of production leading to significant transformation of the country from a net importer to a net food exporter. On the other hand, although the agricultural input subsidy programme is being commended for having helped in achieving food security, the study revealed that the programme requires complementary services of credit, extension, research and market to support it. This will provide an exit strategy, which can enable the producers to sell their produce at higher prices sufficient enough for them to afford agricultural inputs without subsidies.
  • Full Text:
  • Date Issued: 2010

Sustainable growth of SME's

  • Authors: Monks, Patrick Grant Standish
  • Date: 2010
  • Subjects: Success in business -- South Africa -- Port Elizabeth , Business enterprises -- South Africa -- Port Elizabeth
  • Language: English
  • Type: Thesis , Masters , MBA
  • Identifier: vital:8627 , http://hdl.handle.net/10948/1488 , Success in business -- South Africa -- Port Elizabeth , Business enterprises -- South Africa -- Port Elizabeth
  • Description: South Africa and more specifically Port Elizabeth is faced with many challenges with regard to economic growth and unemployment. It is generally acknowledged that the “Small to Medium Enterprises” (SME) are the largest employers in any economy, additionally SME’s are large contributors to the gross domestic product. Successful SME’s are the catalysts of the economy and over time they can develop into large enterprises. It is clear that in order for a country to have a strong and sustainable economy it needs to have a strong and successful SME sector. Unfortunately the South African SME sector performs relatively poorly in comparison with the SME sectors around the world (Herrington, Kew & Kew, 2009). With the knowledge of the importance of the SME sector to the economy and the knowledge that the South African SME’s are generally underperforming, this study will identify how to improve the relative success rate of the SME sector in Port Elizabeth South Africa. In order to achieve this, this study needs to identify why the SME sector is not performing on a par with other SME sectors from around the globe and what initiatives need to be implemented in Port Elizabeth that will enable its SME sector to perform at the same level or better than other SME sectors from around the globe. This study identifies that the South African SME’s are provided with a number of support initiatives. Some of these support initiatives have been very effective, while other support initiatives have been unsuccessful or have failed. This study concludes by identifying a number of areas that need improvement; of these areas two are identified as being critical to SME’s success and sustainability, these two areas are: · The need to make SME’s more aware of the government / business initiatives that are available; and · Establish more effective mentoring and coaching. In order to address these critical areas, the study suggests the use of an internet portal that can be used to coordinate all the activities between the mentors and the SME’s. This internet portal will be expanded to become the core information hub and collaboration centre for the flow of information between the SME’s and any of their stakeholders. Once all this information is centralised it will be a relatively simple process to measure the success rate of the SME’s and the effectiveness of the different mentors.
  • Full Text:
  • Date Issued: 2010

Swelling, erosion and drug release characteristics of salbutamol sulfate from hydroxypropyl methylcellulose-based matrix tablets

  • Authors: Chaibva, Faith A , Khamanga, Sandile M , Walker, Roderick B
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/184139 , vital:44177 , xlink:href="https://doi.org/10.3109/03639045.2010.488648"
  • Description: Background: Hydrophilic matrix formulations are important and simple technologies that are used to manufacture sustained release dosage forms. Method: Hydroxypropyl methylcellulose-based matrix tablets, with and without additives, were manufactured to investigate the rate of hydration, rate of erosion, and rate and mechanism of drug release. Scanning electron microscopy was used to assess changes in the microstructure of the tablets during drug release testing and whether these changes could be related to the rate of drug release from the formulations. Results: The results revealed that the rate of hydration and erosion was dependent on the polymer combination(s) used, which in turn affected the rate and mechanism of drug release from these formulations. It was also apparent that changes in the microstructure of matrix tablets could be related to the different rates of drug release that were observed from the test formulations. Conclusion: The use of scanning electron microscopy provides useful information to further understand drug release mechanisms from matrix tablets.
  • Full Text:
  • Date Issued: 2010

Symmetrically and unsymmetrically substituted carboxy phthalocyanines as sensitizers for nanoporous ZnO films

  • Authors: Masilela, Nkosiphile , Nombona, Nolwazi , Loewenstein, Thomas , Nyokong, Tebello , Schlettwein, Derck
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/249126 , vital:51780 , xlink:href="https://doi.org/10.1142/S1088424610002793"
  • Description: The photoelectroectrochemical studies of water soluble octacarboxylated oxotitanium (OTiOCPc), zinc (ZnOCPC), hydroxyaluminium ((OH)AlOCPc), dihydroxysilicon ((OH)2SiOCPc), hydroxygallium (OHGaOCPc) and low symmetry zinc monocarboxy (ZnMCPc) phthalocyanines were performed. The dyes were adsorbed to nanoporous ZnO electrodeposited in the presence of eosin Y as structure directing agent (SDA) on FTO substrates by refluxing or soaking the films in a solution containing the dye of interest such that a full surface coverage was achieved. High external (IPCE) and internal (APCE) quantum efficiencies of up to 50.6% and 96.7% were achieved for the OTiOCPc complex. There was a lower overall cell efficiency for cells sensitized with phthalocyanines containing hydroxyl as axial ligand ZnO/(OH)2SiOCPc, ZnO/(OH)GaOCPc and (OH)AlOCPc because of strong aggregation on the surface of the electrodes. To further suppress dye aggregation, the zinc complex of a new monocarboxylated phthalocyanine sensitizer with bulky naphtho side groups (ZnMCPc) was employed. Among the studied sensitizers, ZnMCPc gave the highest overall cell efficiency of phthalocyanine electrodeposited on ZnO of η = 0.48%.
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  • Date Issued: 2010

Synergistic potententials and isolation of bioactive compounds from the extracts of two helichrysum species indigenous to the Eastern Cape province

  • Authors: Aiyegoro, Olayinka Ayobami
  • Date: 2010
  • Subjects: Helichrysum -- South Africa -- Eastern Cape , Antibiotics , Antioxidants , Medicinal plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD (Microbiology)
  • Identifier: vital:11268 , http://hdl.handle.net/10353/250 , Helichrysum -- South Africa -- Eastern Cape , Antibiotics , Antioxidants , Medicinal plants -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Eastern Cape
  • Description: Helichrysum longifolium and H. pedunculatum belong to the Astereceae family and are used extensively in folkloric medicine in South Africa to manage stress-related ailments and as dressings for wounds normally encountered in circumcision rites, bruises, cuts and sores. The in vitro antibacterial time-kill studies, the synergistic potentials, the phytochemical screenings and antioxidant potentials as well as the isolation of the bioactive compounds from the extracts of these two plants were carried out in this study. The in vitro antibacterial activities and time kill regimes of crude extracts of H. pedunculatum was assessed. The extracts was active against both Gram positive and Gram negative bacteria tested at a concentration of 10 mg/ml. Minimum Inhibitory Concentration (MIC) values for all the susceptible bacteria ranged between 0.1 – 35 mg/ml. The average log reduction in viable cell count in time kill assay ranged between 0.17 Log10 to 6.37 Log10 cfu/ml after 6 h of interaction, and between 0.14 Log10 and 6.99 Log10 cfu/ml after 12 h interaction in 1 × MIC and 2 × MIC of the extract. The effect of the aqueous extract was only bacteriostatic on both reference and environmental strains and the clinical isolates were outrightly resistant to aqueous extract. This is worrisome and this could be one reason why, there is an incidence of high death rate resulting from circumcision wounds infection even after treating such wounds with H. pedunculatum leaf. In vitro antibacterial time kill studies of extracts of H. longifolium was assessed. All test bacteria were susceptible to the methanol extract, while none was susceptible to the aqueous extract. Two of the test bacteria were susceptible to the ethyl acetate extract, while ten and seven were susceptible to the acetone and chloroform extracts respectively at the test concentration of 5 mg/ml. The minimum inhibitory concentrations (MICs) ranged between 0.1 and 5.0 mg/ml, while minimum bactericidal concentrations (MBCs) ranged between 1.0 and >5 mg/ml for all the extracts. Average log reductions in viable cell counts for all the extracts ranged between 0.1 Log10 and 7.5 Log10 cfu/ml after 12 h interaction at 1 × MIC and 2 × MIC. Most of the extracts were rapidly bactericidal at 2 × MIC achieving a complete elimination of most of the test organisms within 12 h exposure time. The effect of combinations of the crude extracts of H. pedunculatum leaves and eight antibiotics was investigated by means of checkerboard and time-kill methods. In the checkerboard method, synergies of between 45.83-56.81 percent were observed and this is independent of Gram reaction, with combinations in the aqueous extract yielding largely antagonistic interactions (18.75 percent). The time kill assay also detected synergy that is independent of Gram reaction with a ≥ 3Log10 potentiation of the bactericidal activity of the test antibiotics. We conclude that the crude leaf extracts of H. pedunculatum could be potential source of broad spectrum antibiotics resistance modulating compounds. The interactions between crude extracts of H. longifolium in combination with six first-line antibiotics using both the time-kill and the checkerboard methods were carried out. The time-kill method revealed the highest bactericidal activity exemplified by a 6.7 Log10 reduction in cell density against Salmonella sp. when the extract and Penicillin G are combined at ½ × MIC. Synergistic response constituted about 65 percent, while indifference and antagonism constituted about 28.33 percent and 6.67 percent in the time kill assay, respectively. The checkerboard method also revealed that the extracts improved bactericidal effects of the antibiotics. About 61.67 percent of all the interactions were synergistic, while indifference interactions constituted about 26.67 percent and antagonistic interactions was observed in approximately 11.66 percent. The in vitro antioxidant property and phytochemical constituents of the aqueous crude leaf extracts of H. longifolium and H. pedunculatum was investigated. The scavenging activity on superoxide anions, DPPH, H2O2, NO and ABTS; and the reducing power were determined, as well as the flavonoid, proanthocyanidin and phenolic contents of the extracts. The extracts exhibited scavenging activity in all radicals tested due to the presence of relatively high total phenol and flavonoids contents in the extracts. Our findings suggest that H. longifolium and H. pedunculatum are endowed with antioxidant phytochemicals and could serve as a base for future drugs. Bioactivity-guided fractionation of the leaves of H. longifolium and H. pedunculatum yielded two known compounds. From the n-hexane fraction of H. longifolium a compound was isolated (Stigmasterol) and from the ethyl acetate fraction of H. pedunculatum another compound (β-sitosterol) was isolated. The compounds were isolated and identified using various techniques. The antimicrobial, anti-inflammatory, antioxidant, analgesic and anti-pyretic activities of these compounds have been reported in literatures. In general, the experiments and tests conducted in this study appear to have justified the folkloric medicinal uses of H. longifolium and H. pedunculatum for the treatment of stress related ailments and wound infections and make a substantial contribution to the knowledge base of the use of herbal medicine for the treatment of the microbial infections.
  • Full Text:
  • Date Issued: 2010

Syntheses and investigation of the effects of position and nature of substituent on the spectral, electrochemical and spectroelectrochemical properties of new cobalt phthalocyanine complexes

  • Authors: Akinbulu, Isaac A , Nyokong, Tebello
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/261677 , vital:53434 , xlink:href="https://doi.org/10.1016/j.poly.2010.01.004"
  • Description: The syntheses of new cobalt phthalocyanine (CoPc) complexes, tetra-substituted with diethylaminoethanethio at the peripheral (complex 3a) and non-peripheral (complex 3b) positions, and with benzylmercapto at the non-peripheral position (complex 5), are reported. The effects of the nature and position of substituent on the spectral, electrochemical and spectroelectrochemical properties of these complexes are investigated. Solution electrochemistry of complex 3a showed three distinctly resolved redox processes attributed to CoIIIPc−2/CoIIPc−2 (E½ = +0.64 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.24 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.26 V versus Ag|AgCl) species. No ring oxidation was observed in complex 3a. Complex 3b showed both ring-based oxidation, attributed to CoIIIPc−1/CoIIIPc−2 species (Ep = +0.86 V versus Ag|AgCl), and ring-based reduction associated with CoIPc−2/CoIPc−3 species (E½ = −1.46 V versus Ag|AgCl), with the normal metal-based redox processes in CoPc complexes: CoIIIPc−2/CoIIPc−2 (Ep = +0.41 V versus Ag|AgCl) and CoIIPc−2/CoIPc−2 (E½ = −0.38 V versus Ag|AgCl). Solution electrochemistry of complex 5 showed the same type and number of species observed in complex 3a: CoIIIPc−2/CoIIPc−2 (Ep = +0.59 V versus Ag|AgCl), CoIIPc−2/CoIPc−2 (E½ = −0.26 V versus Ag|AgCl) and CoIPc−2/CoIPc−3 (E½ = −1.39 V versus Ag|AgCl) species. These processes were confirmed using spectroelectrochemistry.
  • Full Text:
  • Date Issued: 2010

Synthesis and electrochemical characterisation of new tantalum (V) alkythio phthalocyanines

  • Authors: Chauke, Vongani , Nyokong, Tebello
  • Date: 2010
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/249093 , vital:51777 , xlink:href="https://doi.org/10.1016/j.ica.2010.05.003"
  • Description: The synthesis and electrochemical characterisation of octa-pentylthio (4a) and octa-octylthio (4b) – phthalocyaninato tantalum (III) hydroxide are hereby reported. These TaPc complexes absorb in the near infrared region (∼800 nm in dichloromethane). They show good solubility in most common solvents especially non-viscous solvents such as dichloromethane and chloroform. NMR, mass and infrared spectroscopy and elemental analysis confirmed the structures and purity of the synthesised complexes. The cyclic voltammograms (CVs) showed reversible reduction couples and irreversible oxidation peaks. The latter exhibited adsorption behavior. The reduction processes were observed at −0.74 and −1.13 V (versus Ag|AgCl) for 4a, and −0.67, −1.02 and −1.48 V (versus Ag|AgCl) for 4b. Spectroelectrochemistry confirmed one metal reduction, with the rest of the redox processes being centered on the phthalocyanine ring.
  • Full Text:
  • Date Issued: 2010
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