List of Titles

Social parasitism by honeybee workers (Apis mellifera capensis Escholtz): host finding and resistance of hybrid host colonies

- Neumann, Peter, Radloff, Sarah E, Moritz, Robin F A, Hepburn, H Randall, Reece, Sacha L

Authors: Neumann, Peter , Radloff, Sarah E , Moritz, Robin F A , Hepburn, H Randall , Reece, Sacha L
Date: 2001
Language: English
Type: text , Article
Identifier: vital:6907 , http://hdl.handle.net/10962/d1011860
Description: We studied possible host finding and resistance mechanisms of host colonies in the context of social parasitism by Cape honeybee (Apis mellifera capensis) workers. Workers often join neighboring colonies by drifting, but long-range drifting (dispersal) to colonies far away from the maternal nests also rarely occurs. We tested the impact of queenstate and taxon of mother and host colonies on drifting and dispersing of workers and on the hosting of these workers in A. m. capensis, A. m. scutellata, and their natural hybrids. Workers were paint-marked according to colony and reintroduced into their queenright or queenless mother colonies. After 10 days, 579 out of 12,034 labeled workers were recaptured in foreign colonies. We found that drifting and dispersing represent different behaviors, which were differently affected by taxon and queenstate of both mother and host colonies. Hybrid workers drifted more often than A. m. capensis and A. m. scutellata. However, A. m. capensis workers dispersed more often than A. m. scutellata and the hybrids combined, and A. m. scutellata workers also dispersed more frequently than the hybrids. Dispersers from queenright A. m. capensis colonies were more often found in queenless host colonies and vice versa, indicating active host searching and/or a queenstate-discriminating guarding mechanism. Our data show that A. m. capensis workers disperse significantly more often than other races of A. mellifera, suggesting that dispersing represents a host finding mechanism. The lack of dispersal in hybrids and different hosting mechanisms of foreign workers by hybrid colonies may also be responsible for the stability of the natural hybrid zone between A. m. capensis and A. m. scutellata.
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Date Issued: 2001

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SoDA : a model for the administration of separation of duty requirements in workflow systems

- Perelson, Stephen

Authors: Perelson, Stephen
Date: 2001
Subjects: Electronic data processing departments -- Security measures , Computers -- Access control
Language: English
Type: Thesis , Masters , MTech (Information Technology)
Identifier: vital:10796 , http://hdl.handle.net/10948/68 , Electronic data processing departments -- Security measures , Computers -- Access control
Description: The increasing reliance on information technology to support business processes has emphasised the need for information security mechanisms. This, however, has resulted in an ever-increasing workload in terms of security administration. Security administration encompasses the activity of ensuring the correct enforcement of access control within an organisation. Access rights and their allocation are dictated by the security policies within an organisation. As such, security administration can be seen as a policybased approach. Policy-based approaches promise to lighten the workload of security administrators. Separation of duties is one of the principles cited as a criterion when setting up these policy-based mechanisms. Different types of separation of duty policies exist. They can be categorised into policies that can be enforced at administration time, viz. static separation of duty requirements and policies that can be enforced only at execution time, viz. dynamic separation of duty requirements. This dissertation deals with the specification of both static separation of duty requirements and dynamic separation of duty requirements in role-based workflow environments. It proposes a model for the specification of separation of duty requirements, the expressions of which are based on set theory. The model focuses, furthermore, on the enforcement of static separation of duty. The enforcement of static separation of duty requirements is modelled in terms of invariant conditions. The invariant conditions specify restrictions upon the elements allowed in the sets representing access control requirements. The sets are themselves expressed as database tables within a relational database management system. Algorithms that stipulate how to verify the additions or deletions of elements within these sets can then be performed within the database management system. A prototype was developed in order to demonstrate the concepts of this model. This prototype helps demonstrate how the proposed model could function and flaunts its effectiveness.
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Date Issued: 2001

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Solvent-free axial ligand substitution in octaphenoxyphthalocyaninato silicon complexes using microwave irradiation

- Maree, M David, Nyokong, Tebello

Authors: Maree, M David , Nyokong, Tebello
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/304830 , vital:58494 , xlink:href="https://journals.sagepub.com/doi/epdf/10.3184/030823401103168974"
Description: Several axially substituted octaphenoxy silicon phthalocyanines were prepared by condensation of the complexes used as axial ligands with octaphenoxyphthalocyaninato (dichloro) silicon under microwave irradiation.
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Date Issued: 2001

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Spatial aspects of the reproductive and feeding biology of the striped robber, Brycinus lateralis (Pisces: Characidae), in the Okavango Delta, Botswana

- Booth, Anthony J, McKinlay, Bruce W

Authors: Booth, Anthony J , McKinlay, Bruce W
Date: 2001
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/127020 , vital:35944 , https://doi.10.1080/15627020.2001.11657111
Description: The Okavango Delta is a vast inland wetland system situated in northern Botswana. High rainfall is received in early summer in the southern Angolan highlands and throughout the Delta with the flood waters reaching the upper riverine floodplain between March and May where it percolates through to the lower drainage rivers between July and September. Aspects of the reproductive and feeding biology of two allopatric populations of the striped robber, Brycinus lateralis, a small characin species inhabiting the northern riverine floodplain and southern drainage rivers, were investigated. Both populations were similar in the biological aspects studied, with the flood cycle having little influence on the timing of reproduction, sexual maturity and dietary composition. Female fish from both populations matured sexually at 57mmSL, breeding over a protracted period during the warm, summer months. In both populations, the sex ratio was female-dominated at 4.8:1 (riverine floodplain) and 2.2:1 (drainage rivers). The striped robber is an opportunistic micro-carnivore with immature fish feeding predominantly on Daphnia spp. and adults being largely insectivorous.
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Date Issued: 2001

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Spatial aspects of the reproductive and feeding biology of the striped robber, Brycinus lateralis (Pisces: Characidae), in the Okavango Delta, Botswana

- Booth, Anthony J, McKinlay, Bruce W

Authors: Booth, Anthony J , McKinlay, Bruce W
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/446838 , vital:74564 , https://doi.org/10.1080/15627020.2001.11657111
Description: The Okavango Delta is a vast inland wetland system situated in northern Botswana. High rainfall is received in early summer in the southern Angolan highlands and throughout the Delta with the flood waters reaching the upper riverine floodplain between March and May where it percolates through to the lower drainage rivers between July and September. Aspects of the reproductive and feeding biology of two allopatric populations of the striped robber, Brycinus lateralis, a small characin species inhabiting the northern riverine floodplain and southern drainage rivers, were investigated. Both populations were similar in the biological aspects studied, with the flood cycle having little influence on the timing of reproduction, sexual maturity and dietary composition. Female fish from both populations matured sexually at 57 mm SL, breeding over a protracted period during the warm, summer months. In both populations, the sex ratio was female-dominated at 4.8:1 (riverine floodplain) and 2.2:1 (drainage rivers). The striped robber is an opportunistic micro-carnivore with immature fish feeding predominantly on Daphnia spp. and adults being largely insectivorous.
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Date Issued: 2001

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Spectroscopic studies of the interaction of cobalt (II) N, N', N ″, N‴-tetramethyltetra-3, 4-pyridinoporphyrazine with amino acids and nitrogen oxides

- Thamae, Mamothibe A, Nyokong, Tebello

Authors: Thamae, Mamothibe A , Nyokong, Tebello
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/291617 , vital:56892 , xlink:href="https://doi.org/10.1002/jpp.551"
Description: The interaction of histidine, cysteine, NO and nitrite with cobalt(II) N,N',N″,N‴-tetramethyltetra-3,4-tetrapyridinoporphyrazine ([CoIItmtppa]4+) is reported. Metal-based autoreduction of [CoIItmtppa]4+ occurs with the formation of the [CoItmtppa(-2)]3+ species in the presence of histidine and cysteine. Kinetic data for the auto reduction of [CoIItmtppa]4+ in the presence of these amino acids gave the rate constants kf = 2.1 × 101 and 2.8 dm3 mol-1 s-1, for cysteine and histidine, respectively. One molecule of NO or nitrite was found to coordinate to the [CoIItmtppa]4+ species. The equilibrium and rate constants for the coordination of the nitric oxide were K = 2.3 × 104dm3mol-1 and kf = 7.5 dm3mol-1s-1, respectively. The coordination of nitrite to [CoIItmtppa]4+ occurred with an equilibrium constant of K = 2.0 × 102dm3mol-1 and a rate constant of kf = 4.0 × 10-3dm3mol-1s-1. There was no evidence for the coordination of two molecules of nitrite to the [CoIItmtppa]4+ species.
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Date Issued: 2001

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Strategies for the improvement of the industrial oxidation of cymene

- Harmse, Nigel

Authors: Harmse, Nigel
Date: 2001
Subjects: Oxidation , Cymene
Language: English
Type: Thesis , Masters , MTech (Chemistry)
Identifier: vital:10958 , http://hdl.handle.net/10948/73 , Oxidation , Cymene
Description: The oxidation of cymene with dioxygen has been investigated in some detail with the view of establishing the feasibility of improving the efficiency of the oxidation process. Of particular interest were the rate of cymene oxidation and the selectivity of the oxidation process for the tertiary cymene hydroperoxide, especially at conversions above 15%. In order to be able to evaluate the selectivity of oxidation processes, a reliable method for analysis of the individual hydroperoxides had to be established. Two methods were investigated, namely reduction of the hydroperoxides to alcohols using ferrous sulphate and reduction using triphenylphosphine, and analysing the reduction products by gas chromatography. Of these two methods, the triphenylphosphine method proved to be superior to the ferrous sulphate method and was used as the method of choice for this investigation. A number of oxidation systems were evaluated in an initial screening experiment for the oxidation of p-cymene. The results of this screening experiment showed that three-phase oxidation systems, i.e. systems containing an organic phase, an aqueous phase and gas, gave significantly lower activities than two-phase oxidation systems. In addition, the use of a base in the aqueous layer does not improve the overall selectivity of the oxidation process, but improves the selectivity towards the tertiary hydroperoxide to some extent due to the decomposition and extraction of primary hydroperoxide into the basic aqueous phase. Oxidation systems using a non-autoxidation catalyst, i.e. a catalyst that does not catalyse the conventional autoxidation of organic compounds, gave by far the most promising results. These systems gave both a high selectivity as well as high reaction rate. From the initial screening experiment, and using multi-factorial statistical techniques, two catalyst systems were selected for investigation, namely vanadium phosphate and boron phosphate. The results of these investigations showed that these two catalysts are remarkably active and selective for the oxidation of p-cymene, giving the cymene tertiary hydroperoxide in selectivities exceeding 85% and at substrate conversions as high as 25%. These results are a considerable improvement over currently known oxidation systems and may offer opportunities for further commercial exploitation.
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Date Issued: 2001

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Stratigraphy and geochemistry of the Makganyene formation, Transvaal supergroup, Northern Cape, South Africa

- Polteau, Stéphane

Authors: Polteau, Stéphane
Date: 2001
Subjects: Geology, Stratigraphic -- South Africa -- Northern Cape , Geochemistry -- South Africa -- Northern Cape
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5003 , http://hdl.handle.net/10962/d1005616 , Geology, Stratigraphic -- South Africa -- Northern Cape , Geochemistry -- South Africa -- Northern Cape
Description: The Makganyene Formation forms the base of the Postmasburg Group in the Transvaal Supergroup of the Northern Cape Province. The Makganyene Formation has diamictite as the main rock type, but siltstone, sandstone, shale, and iron-formations are also present. A glacial origin has been proposed in the past due to the presence of dropstones, faceted and striated pebbles. Typically, the Makganyene Formation contains banded iron-formations interbedded with clastic rocks (shale, siltstone, sandstone and diamictites) at the contact with the underlying iron-formations. This transitional zone is generally overlain by massive or layered diamictites which contain poorly sorted clasts (mainly chert) within a shaly matrix. Striated pebbles have been found during field work, and dropstones have been observed in diamictites and banded iron-formations during the study. The top of the Makganyene Formation contains graded cycles interbedded with diamictites and thin layers of andesitic lavas from the Ongeluk Formation. The basal contact of the Makganyene Formation with the underlying Koegas Subgroup was described as unconformable by previous workers. However field work localised in the Rooinekke area shows a broadly conformable and interbedded contact with the underlying Koegas Subgroup. As described above, banded iron-formations are interbedded with the clastic rocks of the Makganyene Formation. Moreover, boreholes from the Sishen area display the same interbedding at the base of the Makganyene Formation. This suggests that no significant time gap is present in the whole succession between the Ghaap and Postmasburg Group. The Transvaal Supergroup in the Northern Cape displays the following succession : carbonates-BIFs-diamictites/ lava-BIFs-carbonates. The Makganyene Formation is thus at the centre of a symmetrical lithologic succession. Bulk rock compositions show that the diamictites have a similar composition to banded iron-formation with regard to their major element contents. Banded iron-formations acted as a source for the diamictites with carbonates and igneous rocks representing minor components. Differences in bulk composition between the Sishen and Matsap areas emphasize that the source of the diamictite was very localised. The Chemical Index of Alteration (CIA) has been calculated, but since the source dominant rock was iron-formation, this index cannot be usefully applied to the diamictites. ACN, A-CN-K, and A-CNK-FM diagrams confer a major importance in sorting processes due to the separation between the fine and coarse diamictites. The interbedded iron-formations display little clastic contamination indicating deposition in clear water conditions. However, dropstones are present in one borehole from the Matsap area, indicating that iron-formation took place under ice cover, or at least under icebergs. Stable isotope studies show that the iron-formations, interbedded towards the base of the Makganyene Formation, have similar values to the iron-formations of the Koegas Subgroup. As a result of the above observations, new correlations are proposed in this study, relating the different Transvaal Supergroup basins located on the Kaapvaal Craton. The Pretoria Group of the Transvaal Basin has no correlative in the Griqualand West Basin, and the Postmasburg Group of the Northern Cape Basin has no lateral equivalent in the Transvaal Basin. These changes have been made to overcome problems present in the current correlations between those two basins. The Makganyene Formation correlates with the Huronian glaciations which occurred between 2.4 and 2.2 Ga ago in North America. Another Precambrian glaciation is the worldwide and well-studied Neoproterozoic glaciation (640 Ma). At each of these glaciations, major banded iron-formation deposition took place with associated deposition of sedimentary manganese in post-glacial positions. The central position of the Makganyene Formation within the Transvaal Supergroup in the Northern Cape emphasizes this glacial climatic dependence of paleoproterozoic banded iron-formation and manganese deposition. However these two Precambrian glaciations are interpreted in paleomagnetic studies as having occurred near to the equator. The controversial theory of the Snowball Earth has been proposed which proposes that the Earth was entirely frozen from pole to pole. Results from field work, sedimentology, petrography and geochemistry were integrated in a proposed depositional model of the Makganyene Formation occurring at the symmetrical centre of the lithologic succession of the Transvaal Supergroup. At the beginning of the Makganyene glaciation, a regression occurred and glacial advance took place. The diamictites are mostly interpreted as being deposited from wet-based glaciers, probably tidewater glaciers, where significant slumping and debris flows occurred. Any transgression would cause a glacial retreat by rapid calving, re-establishing the chemical sedimentation of banded iron-formations. These sea-level variations are responsible for the interbedding of these different types of rocks (clastic and chemical). The end of the Makganyene glacial event is characterised by subaerial eruptions of andesitic lava of the Ongeluk Formation bringing ashes into the basin. Banded iron-formation and associated manganese accumulations are climate-dependant. Glacial events are responsible for the build up of metallic ions such as iron and manganese in solution in deep waters. A warmer climate would induce a transgression and precipitation of these metallic ions when Eh conditions are favourable. In the Transvaal Supergroup, the climatic variations from warm to cold, and cold to warm are expressed by the lithologic succession. The warm climates are represented by carbonates. Cold climates are represented by banded iron-formations and the peak in cold climate represented by the diamictites of the Makganyene Formation. These changes in climate are gradual, which contradict the dramatic Snowball Earth event: a rapid spread of glaciated areas over low-latitudes freezing the Earth from pole-to-pole. Therefore, to explain low-latitude glaciations at sea-level, a high obliquity of the ecliptic is most likely to have occurred. This high obliquity of the ecliptic was acquired at 4.5 Ga when a giant impactor collided into the Earth to form the Moon. Above the critical value of 54° of the obliquity of the ecliptic, normal climatic zonation reverts, and glaciations will take place preferentially at low-latitudes only when favourable conditions are gathered (relative position ofthe continents and PC02 in the atmosphere).
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Date Issued: 2001

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StreetNet's progress to date and plans for the future

- StreetNet Association

Authors: StreetNet Association
Date: 2001
Subjects: StreetNet Association
Language: English
Type: text
Identifier: http://hdl.handle.net/10962/162170 , vital:40769
Description: The StreetNet offices were opened in February 2000, eighteen months ago. We are now half-way through our three-year programme to launch StreetNet as an international organisation of street vendors all over the world. tVhat progress has been made in the first eighteen months ? We have two people working part-time in the StreetNet office since February 2000. Pat Horn is the International Co-ordinator while Nozipho Lembethe is the International Administrator. We have been trying unsuccessfully to find a website manager/researcher to start working with us this year.
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Date Issued: 2001

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Studies on the kallikrein-kininogen system of the ostrich (Struthio camelus)

- Bothma, Leonard Frederick

Authors: Bothma, Leonard Frederick
Date: 2001
Subjects: Kallikrein , Kinins , Ostriches
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:11067 , http://hdl.handle.net/10948/275 , Kallikrein , Kinins , Ostriches
Description: Ostrich organs/tissue/fluids were screened for plasma kallikrein-like, tissue kallikrein-like and tonin-like activity in a continuous-fluorogenic-assay system using Pro-Phe-Arg-7-amino-4-methylcoumarine, Phe- Arg-7-amino-4-methylcoumarine and Val-Leu-Arg--7-amino-4-trifluoro-methylcoumarine as substrates. Ostrich liver and kidney showed the highest specific plasma kallikrein-like activity. Ostrich adrenal glands and kidney showed the highest specific tissue kallikrein-like and tonin-like activity. Ostrich high molecular weight kininogen was purified from plasma and low molecular weight kininogen was partially purified. The N-terminal amino acid sequences of both high- and low molecular weight kininogens from ostrich plasma were determined. Ostrich plasma high molecular weight kininogen was purified as a 118 kD protein. The purified high molecular weight kininogen inhibits the cysteine proteinase papain at a ratio of one molecule HKG to two molecules of papain. Ornitho kinin-like molecules were detected in ostrich urine using reverse phase HPLC.
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Date Issued: 2001

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Study abroad in South Africa

- International Education Association of South Africa (IEASA), Mason, Andy

Authors: International Education Association of South Africa (IEASA) , Mason, Andy
Date: 2001
Subjects: Education, Higher -- South Africa , Education and globalization -- South Africa Student mobility -- Africa International education -- South Africa Education, Higher -- International cooperation , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
Language: English
Type: text , book
Identifier: http://hdl.handle.net/10962/65375 , vital:28753 , ISBN 0620247290
Description: [Message from the Honorable Minister of Education, Prof. Kader Asmal]: I am pleased to provide a message for this important Guide to South African Universities and Technikons so soon after my appointment as Minister of Education. Each country depends on the higher education system to meet high human resource needs and to be the engine for the creation of new knowledge and innovation, and critical discourse. Our system offers students a wide choice of career options in a variety of differing environments of a world-class standard. Our universities and technikons play a vital role in preparing students, by equipping them with the necessary knowledge and skills, to take up their rightful place in society and to contribute to the socio-economic development of our country and the many other countries from which students come to study in South Africa. This also affords them the opportunity of making a substantial contribution to the development of human resources in their specialised fields. Like schools, our universities, technikons and other third level institutions must become vibrant centres of community and cultural life. We are looking at the ways in which universities can contribute to the responsibility of citizenship - within an atmosphere of voluntary help. This may be in the form of community service, which many institutions are already involved in, or, for instance, in the form of assisting with a national literacy campaign. In addition they must provide a safe and secure environment conducive to promoting their mission of teaching and learning, scholarship and research, and community service. Proper preparation for the challenges of a fast globalising world is essential if our students are to contribute to the development of the societies and the countries in which they live. Therefore I am committed to building a responsive higher education system of high quality. Such a system should demonstrate its readiness to meet the challenges of the 20st Century. , 1st Edition
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Date Issued: 2001

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Super-realistic rendering using real-time tweening

- Winnemöller, Holger, Bangay, Shaun D

Authors: Winnemöller, Holger , Bangay, Shaun D
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/432810 , vital:72902 , https://citeseerx.ist.psu.edu/document?repid=rep1type=pdfoi=eec3809e91a26dbf991a37a3a6a4f1291ae4ec4d
Description: The realism of contemporary computer graphics (and especially Virtual Reality {VR}) is limited by the great computational cost of rendering objects of appropriate complexity with convincing lighting and surface effects. We introduce a framework that allows rendering of objects in true photographic quality using tweening. The simple but effective design of our system allows us not only to perform the necessary operations in real-time on standard hardware, but also achieve other effects like morphing. Furthermore, it is shown how our system can be gainfully employed in non-VR contexts like extreme low-bandwidth video-conferencing and others.
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Date Issued: 2001

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Superstition, atheism and reasonable faith in Acts 26: a Graeco-Roman perspective on Paul’s defence before Festus and Agrippa

- Germiquet, Edouard Ariste

Authors: Germiquet, Edouard Ariste
Date: 2001
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:21065 , http://hdl.handle.net/10962/6224
Description: This thesis investigates Luke‟s presentation of Paul‟s final and climactic defence of the gospel which takes place before Festus and King Agrippa II (Ac.26). It indicates how Luke has made use of the philosophical doctrine of the mean in order to present Christianity as a reasonable and rational faith. This investigation explores how Luke creates a literary framework within which to promote Paul as reasonable and rational through the application of the topos that true piety is the mean between the two extremes of superstition and atheism. The thesis is therefore structured around three dominant sections in which the major themes of superstition, atheism and rational faith are treated independently. Each section consists of an analysis of Luke‟s choice of words and his description of the behavioural patterns of each representative group so that a consistent picture progressively emerges in support of the basic framework. At all stages of the investigation, reference is made to contemporary moral philosophers, Hellenistic Judaism and the early Christian apologists so that the language, literary settings and stereotypes used by Luke can be clearly defined. This not only clarifies the text of Acts 26 but contributes to an overall appreciation of Luke‟s literary technique. At all points in the development of the thesis, the relevance and centrality which the resurrection has for Luke is kept in mind. This not only acts as a backdrop in understanding Luke‟s depiction of the superstitious and the atheist but is crucial in grasping Luke‟s presentation of Christianity as a rational faith. The thesis is brought to a close by a discussion on Luke's intended audience and the significance of his dedication to Theophilus.
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Date Issued: 2001

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Syntheses and photochemical properties of octasubstituted phthalocyaninato zinc complexes

- Maree, Suzanne, Nyokong, Tebello

Authors: Maree, Suzanne , Nyokong, Tebello
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/304841 , vital:58495 , xlink:href="https://doi.org/10.1002/jpp.388"
Description: In this work a selection of octasubstituted phthalocyaninato zinc complexes were synthesized and their photochemistry studied. The substituents included cholesterol (3a), estrone (3b), naphthol (3c) and phenoxy groups substituted with CH3 (3d), C(CH3)3 (at two positions, 3e), C(CH3)3 (3f), NO2 (3g), NH2 (3h), COH (3i), COOH (3j), and H (3k). In general, complexes containing electron-donating groups attached to the phenoxy ring (e.g. 3e and 3f) were found to be photochemically unstable with photobleaching quantum yields of the order of 10−3. In the presence of electron-withdrawing groups (3g, 3i, and 3j) the photobleaching quantum yields were of the order of 10−6 to 10−5. Singlet oxygen quantum yields (ΦΔ) ranged from 0.01 to 0.73. The lowest ΦΔ was observed for the highly aggregated complex 3c. All the complexes showed aggregation at high concentrations. Electrochemical reduction using a thin-layer spectroelectrochemistry cell showed that the complexes become more monomeric following reduction.
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Date Issued: 2001

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Synthesis and characterisation of novel platinum (II) complexes potential chemotherapeutic drugs

- Datt, Michael Steven

Authors: Datt, Michael Steven
Date: 2001
Subjects: Chemotherapy Platinum
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:4366 , http://hdl.handle.net/10962/d1005031
Description: The present study involves the preparation of novel mixed-ligand platinum(II) complexes in the hope of expanding the range of platinum(II) complexes that exhibit anticancer activity and which are less toxic and have a broader spectrum of activity than cisplatin and its analogues. To this end, N-(3-R-benzoyl)-N’,N’-diethylthiourea, N-(3-R-benzoyl)-N’-morpholinothiourea, N-(3-Rbenzoyl)-N’,N’-di(2-hydroxyethyl)thiourea (R = NO2, Cl, H, CH3, OCH3), N,N-diethyl-N’-menthyloxycarbonylthiourea and N-menthyloxycarbonyl-N’-morpholinothiourea ligands, and their corresponding mixed-ligand platinum(II) complexes of the type [PtCl(L)(RR’SO)], were synthesised and characterised by elemental analyses, IR, 1H and 195Pt NMR spectroscopy and, in some cases, X-ray crystallography. Dimethylsulfoxide complexes were prepared using all the ligands, while complexes containing unsymmetrically substituted sulfoxides were prepared using the N-benzoyl-N’,N’-diethylthiourea and ,N-diethyl-’-(-)-(3R)-menthyloxycarbonylthiourea ligands only. The molecular structures of cis-(S,S)-[PtCl(DMSO)(L)] (where L = N-benzoyl-N’,N’-diethylthioureato, N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato), cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(MPSO)] and cis-[Pt(N-benzoyl-N’,N’-diethylthioureato)2] were determined by X-ray crystallography. The X-ray crystal structure of N,N-diethyl-N’- (-)-(3R)-menthyloxycarbonylthiourea was also determined. The spectroscopic and crystallographic data are consistent with complexes containing a (S,O)-chelated ligand and a sulfur-bonded sulfoxide ligand. However, the 1H and 195Pt NMR studies showed that the alkoxycarbonylthioureato complexes exist as geometric isomers with the sulfoxide coordinated either in a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand, whereas the acylthioureato complexes yielded only cis-(S,S)-[PtCl(L)(RR’SO)] complexes. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands was examined further by treatment of the [PtCl(DMSO)(L)] complexes, where L = Nbenzoyl-N’,N’-diethylthioureato, N-benzoyl-N’-morpholinothioureato, N,N-diethyl-N’-(-)-(3R)- menthyloxycarbonylthioureato and N-(+)-(3S)-menthyloxycarbonyl-N’-morpholinothioureato, with PPh3 to give the corresponding [PtCl(L)(PPh3)] and [Pt(L)(PPh3)2]+ complexes. 31P NMR studies of these complexes reveal that the alkoxycarbonylthioureato ligands bind less strongly than the acylthioureato ligands, which is consistent with the crystallographic studies. The morpholine derivatives of the acylthioureato and alkoxycarbonylthioureato ligand systems also appear to bind less tightly than the diethyl derivatives. The weaker binding properties of the alkoxycarbonylthioureato ligands might be a possible explanation for the observed geometric isomerisation of these complexes, with the mechanism of isomerisation involving a chelate ringiv opening step. Furthermore, crystallographic and 31P NMR studies suggest that the acylthioureato carbonyl oxygen donor atom is relatively softer and therefore has a greater trans-influence than the carbonyl oxygen donor atom of the alkoxycarbonylthioureato ligand. The substitution kinetics of the chloride and sulfoxide leaving groups by azide, iodide, thiocyanate, triphenylphosphine, 2-mercaptobenzimidazole, 4-(dimethylamino)pyridine and thiourea, from selected cis-(S,S)-[PtCl(N,N-dialkyl-N’-(3-R-benzoyl)thioureato)(RR’SO)] complexes, in methanol, were evaluated to determine if variation of the electronic properties of the chelated ligand and variation of the sulfoxide have a significant influence on the reactivity of these complexes. Two consecutive reactions were observed. It was found that neutral nucleophiles initially substitute the dimethylsulfoxide, while anionic nucleophiles substituted the chloride ligand. For all the nucleophiles studied, the first substitution step was evaluated, except for triphenylphosphine and 4-(dimethylamino)pyridine, where the second step was also evaluated. The overall order of reactivity for the first substitution step was; N3 - < DMAP < I- < SCN- < MBI < thiourea < PPh3, with the rate varying three orders of magnitude. The substitution of the dimethylsulfoxide ligand by PPh3 from cis-(S,S)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl-(DMSO)] to form cis-(S,P)-[Pt(N-benzoyl-N’,N’-diethylthioureato)Cl(PPh3)] was confirmed by X-ray crystallography. In general, manipulation of the chelating moiety, as well as interchanging the sulfoxide did not alter the reactivity of these complexes to a great extent. The anticancer activity of all the platinum(II) sulfoxide complexes were evaluated against a HeLa cell line, of which three complexes, cis-(S,S)-[PtCl(DMSO)(N,N-diethyl-N’-(3-nitrobenzoyl)- thioureato)], cis-(S,S)-[PtCl(DMSO)(N-morpholino-N’-(3-nitrorobenzoyl)thioureato)] and cis-(S,S)-[PtCl(DMSO)(N-(3-methoxybenzoyl)-N’-morpholinothioureato)] exhibited a concentration dependent anti-proliferative effect, but were less potent than cisplatin. These three complexes displayed a similar dose response in a MCF-7 cell line. Preliminary morphology studies with the three biologically active complexes in a HeLa cell line suggest that they induce cell death by apoptosis. Preliminary pBR322 plasmid DNA binding studies of selected [Pt(acylthioureato)Cl(RR’SO)]complexes clearly indicate that these complexes have a different mode of binding to DNA than cisplatin.
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Date Issued: 2001

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Synthesis, spectroscopy and electrochemistry of octaphenoxyphthalocyaninato silicon complexes

- Maree, M David, Nyokong, Tebello

Authors: Maree, M David , Nyokong, Tebello
Date: 2001
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/304863 , vital:58497 , xlink:href="https://doi.org/10.1002/jpp.361"
Description: A number of octaphenoxyphthalocyaninato silicon complexes containing a variety of axial ligands, represented by (OPh)8PcSi(X)2 (where X = chloro 3, hydroxy 4, (4-carboxybenzene) acetato 5, isonicatinato 6, propionato 7, nitrophenoxy 8 and dimethylaminoxy 9) have been synthesized using a convenient route starting with the 4,5-diphenoxy-1,2-dicyanobenzene. 1H NMR and UV/vis spectra, and the cyclic voltammetry of the complexes are reported. The complexes are obtained in high yield and are soluble in many organic solvents. Cyclic voltammetry revealed two reduction couples and one oxidation couple for these complexes. Analysis of the cyclic voltammograms showed that compounds 6 and 8 were easier to oxidize and more difficult to reduce than the rest. Also cyclic voltammetry data suggested that electron transfer was not governed only by diffusion.
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Date Issued: 2001

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Talking about teams within a team building context: a discourse analytic study

- Chapman-Blair, Sharon

Authors: Chapman-Blair, Sharon
Date: 2001
Subjects: Discourse analysis , Teams in the workplace
Language: English
Type: Thesis , Masters , MA
Identifier: vital:2947 , http://hdl.handle.net/10962/d1002456 , Discourse analysis , Teams in the workplace
Description: This research initiative responds to some of the issues raised by theoretical challenges leveled at Industrial Psychology (postmodernism), and practical challenges in the workplace (the use of teams) by investigating notions of what a team is via the postmodern methodology of discourse analysis. The research explores “team talk” – repertoires of speech employed by individuals to construct particular versions of “the team” for specific effects, of importance given emphasis placed on shared understanding, expectations and goals in a “team”. A Rhodes University Industrial Psychology Honours class required to work as a team (having participated in a team building exercise), as well as their lecturers who facilitated the team building process were interviewed to obtain “talk” to analyse. This uncovered a multiplicity of meaning, namely four ways of speaking about (constructing) the team. These repertoires are explored in terms of how they are constructed, how they differ across context and speakers, how they interrelate and what they function to achieve. The educational team repertoire constructs academic hierarchy, justifies individualism, positions members as experts and maintains distance from interpersonal processes. The machine repertoire divides work and interpersonal issues, regulates productivity and constructs team roles (defining individual activity and “team fit”), but is inflexible to change. The family repertoire voices emotive aspects to maintain cohesion via conformity, leaderlessness, group identity and shared achievement, but cannot accommodate conflict or workpersonal boundaries. The psychologised team repertoire constructs the team primarily as a therapeutic entity legitimately creating individual identities (and expertise) and facilitating personal growth, but this flounders when support in the “team” fails. Given that each repertoire has a different emphasis (reflective learning versus work processes versus building relationships versus personal growth), there are slippages / clashes between repertoires. This postmodern look at “the team” thus assists in recognizing and problematising these multiple meanings and identifying practical implications.
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Date Issued: 2001

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Teenage motherhood and the regulation of mothering in the scientific literature: the South African example

- Macleod, Catriona I

Authors: Macleod, Catriona I
Date: 2001
Language: English
Type: Article
Identifier: vital:6256 , http://hdl.handle.net/10962/d1007874
Description: The mainstream literature on teenage pregnancy highlights teenagers' inadequate mothering as an area of disquiet. `Revisionists', such as feminist critics, point out that a confluence of negative social factors is implicated in teenagers' mothering abilities. Whether arguing that teenagers make bad mothers or defending them against this, the literature relies on the `invention of "good" mothering'. In this article I highlight the taken-for-granted assumptions concerning mothering (mothering as an essentialized dyad; mothering as a skill; motherhood as a pathway to adulthood; fathering as the absent trace) appearing in the scientific literature on teenage pregnancy in South Africa. I indicate how these assumptions are implicated in the regulation of mothering through the positioning of the teenage mother as the pathologized other, the splitting of the public from the private, domestic space of mothering, and the legitimation of the professionalization of mothering. I explore the gendered implications of the representations of mothering in this literature.
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Date Issued: 2001

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