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Title not specified

Asthenospheric and lithospheric sources for Mesozoic dolerites from Liberia (Africa): trace element and isotopic evidence

  • Authors: Dupuy, C , Marsh, J , Dostal, J , Michard, A , Testa, S
  • Date: 2002
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/140422 , vital:37887 , https://doi.org/10.1016/0012-821X(88)90067-2
  • Description: Combined elemental, and Sr and Nd isotopic data are presented for Mesozoic dolerite dikes of Liberia (Africa) which are related to the initial stage of opening of the Atlantic Ocean.
  • Full Text: false
  • Date Issued: 2002

A study of universal algebras in fuzzy set theory

  • Authors: Murali, V
  • Date: 1988
  • Subjects: Fuzzy sets Algebra, Universal
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5394 , http://hdl.handle.net/10962/d1001983
  • Description: This thesis attempts a synthesis of two important and fast developing branches of mathematics, namely universal algebra and fuzzy set theory. Given an abstract algebra [X,F] where X is a non-empty set and F is a set of finitary operations on X, a fuzzy algebra [I×,F] is constructed by extending operations on X to that on I×, the set of fuzzy subsets of X (I denotes the unit interval), using Zadeh's extension principle. Homomorphisms between fuzzy algebras are defined and discussed. Fuzzy subalgebras of an algebra are defined to be elements of a fuzzy algebra which respect the extended algebra operations under inclusion of fuzzy subsets. The family of fuzzy subalgebras of an algebra is an algebraic closure system in I×. Thus the set of fuzzy subalgebras is a complete lattice. A fuzzy equivalence relation on a set is defined and a partition of such a relation into a class of fuzzy subsets is derived. Using these ideas, fuzzy functions between sets, fuzzy congruence relations, and fuzzy homomorphisms are defined. The kernels of fuzzy homomorphisms are proved to be fuzzy congruence relations, paving the way for the fuzzy isomorphism theorem. Finally, we sketch some ideas on free fuzzy subalgebras and polynomial algebras. In a nutshell, we can say that this thesis treats the central ideas of universal algebras, namely subalgebras, homomorphisms, equivalence and congruence relations, isomorphism theorems and free algebra in the fuzzy set theory setting
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  • Date Issued: 1988

Aspects of the biology and population dynamics of the geelbek Atractoscion aequidens (Cuvier) (Pisces: Sciaenidae) off the South African coast

  • Authors: Griffiths, Marc H
  • Date: 1988
  • Subjects: Sciaenidae -- South Africa Fish populations -- South Africa Atractoscion Atractoscion -- South Africa -- Ecology Atractoscion -- South Africa -- Physiology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5194 , http://hdl.handle.net/10962/d1001970
  • Description: The geelbek Atractoscion aeguidens is an important commercial and recreational linefish species along the South African eastern seaboard . Aspects of its biology and population dynamics were investigated using data collected from various sampling sites along the South African east coast and from catch statistics obtained from both the Sea Fisheries Research Institute (Cape Town), and dealer records. The biological aspects studied included age and growth, reproduction and feeding. It was established that A. aeguidens is a fast growing species with a relatively late age at sexual maturity and a 1:1 sex ratio. Feeding studies revealed that it has become specialized to feed on small pelagic fish. The South African geelbek stock consists of three distinct age related sub-populations, each representing a particular phase in the life cycle. The sub-adults (1-4 yrs) occur in the South West Cape and feed predominantly on anchovy, Engraulis capensis, which they follow, moving inshore in summer and offshore in winter. The adults (5-9 yrs) undergo a seasonal inshore migration to Natal where they spawn in spring. The dynamics of this migration are strongly influenced by the annual movement of their principal prey viz. , Sardinops ocellatus, to that region. As a result the geelbek first arrive in Natal during mid winter. Evidence is also presented to suggest that a significant number of "adolescent " fish (4-5 yrs) undergo limited gonad maturation and a partial migration to at least as far as the South East Cape. Spawning appears to occur offshore. It is postulated that eggs and larvae are transported southwards by the peripheral waters of the Agulhas Current. After spawning the adults probably remain offshore and use the current to aid their return to the South and South West Cape, where they spend summer feeding on the Agulhas Bank. Juveniles (<1 yr) first appear in the South East Cape between January and March. They apparently use this region as a nursery area for almost a year before moving southwards to join the sub-adults in the South West Cape. In the South East Cape, the juveniles feed initially on mysids whereafter they switch to anchovies and pilchards. A preliminary stock assessment using yield per recruit and spawner biomass per recruit models, indicated that despite the current legislation the South African geelbek population is already overexploited. This is largely attributed to high rates of fishing mortality of the migratory adult population. Further management recommendations are therefore proposed. These include a size limit (660 mm FL), derived from an investigation of the interrelationship between natural mortality and somatic growth in a theoretical unexploited cohort, as well as a uniform bag limit for all user groups (5 fish per person per day)
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  • Date Issued: 1988

A contribution towards an understanding of the intensive tank culture of an ornamental Cichlid, Aulonocara Baenschi, from Chipoka, Lake Malawi

  • Authors: Impson, N D (Neville Dean)
  • Date: 1988
  • Subjects: Cichlids -- Nysas, Lake , Cichlids -- Nyasa, Lake -- Physiology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5208 , http://hdl.handle.net/10962/d1004596 , Cichlids -- Nysas, Lake , Cichlids -- Nyasa, Lake -- Physiology
  • Description: The intensive tank culture of ornamental mouthbrooding cichlids poses several problems which limit their aquaculture potential. This project addressed some of these problems for Aulonocara baenschi. The production of juveniles in 2501 aquaria was accelerated when: a) aquaria were equipped with refuges, b) females of less than 70mm in standard length were used as broodstock, c) mouthbrooding females were replaced with gravid females at seven day intervals, and d) embryos were removed from the mouths of females at replacement times for artificial incubation. Two sex ratios also accelerated juvenile production. The sex ratio (male:females) 1:30 yielded the highest spawning returns per tank, and therefore represented the most effective utilization of aquarium space (a critical consideration for the small-scale culturist). Contrastingly, the sex ratio 1:12 yielded the highest clutch sizes and a high percentage female spawning return, and therefore represented the most effective utilization of broodstock (an important consideration for culturists inhibited by financial constraints or having an abundance of culture vessels). The reproductive behaviour of A. baenschi was described. Emphasis was given to aspects of reproduction of relevance to culture, for example; spawning times and seasons, clutch size and its relationship with female size, age and size of sexes at first spawning, embryo development rate and size of first swimming juveniles. The slow growth rate of juveniles, combined with a late attainment of marketable size (± seven months) was a major limitation affecting the cuIture potential of A. baenschi. Two factors favouring the cuIture of this species was the high survival rate recorded for both adults and juveniles, and the comparatively high prices fetched by fish on domestic wholesale markets (R4,00 per fish). It is recommended that A. baenschi should not be cultured exclusively for the relatively small South African ornamental fish market. A more profitable strategy for domestic culturists should involve a major production effort with A. baenschi and other desirable species of Aulonocara (e.g . A. ethelwynnae; A. hansbaenschi; A. stuartgranti & A. maylandi) for foreign markets (in particular, the U.S.A.; Western Europe & Japan). Not only are these markets massive, but prevailing exchange rates of the Rand with these currencies favour such a strategy.
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  • Date Issued: 1988

Jazz: The success of a team

  • Authors: Carin, Sylviane
  • Subjects: McGregor, Chris--1936-1990 , Clegg, Johnny , Mousset, Christian , Angouleme , Chanzy Stadium , Jazz musicians
  • Language: French
  • Identifier: vital:13507 , http://hdl.handle.net/10962/d1005770 , McGregor, Chris--1936-1990 , Clegg, Johnny , Mousset, Christian , Angouleme , Chanzy Stadium , Jazz musicians
  • Description: Interview in a french newspaper of Christian Mousset, artistic director of the 13th Jazz Festival in Angoulême, France (1988), entitled "The 13th festival wouldn't have known an apotheosis end without the mobilization of everybody". The interview was done the day after the festival ended and Mousset is already talking about the 1989 festival. A picture is accompanying the article. From left to right: Johnny Clegg, Christian Mousset and Chris McGregor.
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Nyamaropa

Title not specified

Life history changes of two reef fish species in exploited and unexploited marine environments in South Africa

  • Authors: Buxton, Colin David
  • Date: 1988
  • Subjects: Reef fishes -- Africa, Southern Chrysoblephus laticeps Chrysoblephus cristiceps
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5189 , http://hdl.handle.net/10962/d1001965
  • Description: A detailed investigation into the life histories of Chrysoblephus laticeps and c. cristiceps in exploited and unexploited marine environments on the south-east coast of southern Africa is presented. The study provided information necessary for the evaluation of marine reserves as a management option for these and similar reef species. Visual underwater assessments showed a clear spatial separation between adults and juveniles of both species, suggesting a recruitment of juveniles into shallow water followed by a gradual outward migration into deeper water with age. Denslty estlmates of C. laticeps in the Noordhoek (0.0064 fish/m²) and Tsitslkamma (0.0254 fish/m²) areas were significantly different and were attributed to exploitation. Within area differences in density were also significantly correlated with temperature) depth and substratum relief. Similar comparisons for C. cristiceps were not possible because these fish shied away from divers. Habitat preferences were mirrored in the diets of both species which fed on a wide variety of reef associated benthic animals. Size of prey appeared to be gape limited, only larger fish being able to manipulate prey. Quantitative differences between the diets of fish sampled in different areas were a reflection of differences in available prey and not related to the relative density of predators. The dietary characteristics recorded in these fish were typical of search hunters. An age and growth study based on the examination of sectioned otoliths showed that both species were slow growing and long lived. Maximum recorded ages were 18 and 22 years for C. laticeps and C. cristiceps respectively. Growth rates in exploited and unexploited areas were not significantly different although there was an indication that growth was slower in the exploited areas for C. cristiceps. Several inconsistencies in otolith interpretation and terminology were evaluated. Contrary to other South African studies the results suggested that somatic growth was fastest just after spawning. This coincided with the winter months and was reflected by the deposition of a hyaline zone in the otolith. Two independent estimates, the Pauli derivation and visually assessed length frequency analysis, produced the same value for total mortality of C. laticeps in the Tsitsikamma area (0.2). This result, together with a significant difference in the rate of fishing mortality at different areas along the coast suggested that the populations sampled were discrete and supported the postulate that both species were sedentary. Further support was obtained from a mark-recapture study. Although sample numbers were low the results showed no evidence of large scale migratory patterns in these fish. An investigation of the reproductive biology of both fish showed that they were protogynous hermaphrodites, all males being derived from females with no evidence for polyandry. Males were shown to be capable of mating with a number of females and this, together with monandry, monochromatism and a small testis size, suggested a polygynous mating system in both species. Observations of the courtship behaviour in captive c. laticeps also supported polygyny. A significant difference in the mean size at sex reversal between unexploited and exploited populations supported the postulate that sex reversal was independent of the size or age of the animal. The size at which sex reversal occurred appeared to be dependent on sex ratio. A detailed yield per recruit analysis of the response of the population to different levels of fishing mortality and size at recruitment (t [subscript]r), showed that sex reversing species were particularly vulnerable to over fishing. This was due to a dramatic decline in the number of surviving individuals past t[subscript]r which resulted in a skewing of the sex ratio towards females. Evidence is presented to show that current legislation is inadequately protecting the spawner stock of both species. In conclusion it is shown that longevity, sex reversal, restricted movements and the occupation of a demersal habitat make these species particularly vulnerable to over exploitation in a size- selective fishery. The sustained yield in the linefishery is suggested to be a result of distant recruitment from relatively unexploited populations rather than the adequacy of current conservation measures. The need to protect the spawner stock is emphasised and the use of marine reserves as an additional protection for sedentary reef-dwelling species is therefore advocated.
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  • Date Issued: 1988

Title not specified

The effect of elevated temperature on the nutrient requirements of rainbow trout, Salmo gairdneri (Pisces : Salmonidae) and the development of "least cost" feeds for trout production in South Africa

  • Authors: McEwan, Anthony Graham
  • Date: 1988
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:21150 , http://hdl.handle.net/10962/6606
  • Description: A review of trout metabolism, ingested energetic pathways, essential dietary nutrient requirements and the effect of water temperature on trout physiology identified the need to determine the effect of elevated temperatures (>18oC) on the nutrient requirements of rainbow trout. This review led to the hypothesis that as the temperature exceeds the optimum the growth potential of trout decreases with a theoretical concomitant decrease in the protein requirement. However, the increased metabolic rates of the fish should be reflected by an increased demand for lipids. The experiments designed to test this hypothesis revealed that at temperatures in excess of 18 oC the protein requirement for small (4.5g) and larger (>25g) juvenile rainbow trout are 40 and 35% respectively. This represents a decrease of 10% for the small juveniles and no change for larger juveniles compared to their requirements at optimum temperatures. The lipid requirements for the small as well as the larger juveniles increased by approximately 5 percent, to between 20 and 23 percent, compared to the requirement at optimum temperatures. Consequently the hypothesis was accepted. A review of practical diet formulation is presented along with a description of the experiments conducted to test several "least cost" diets under South African conditions. Recommendations that winter and summer diets be formulated and that the trout producers manufacture their own feeds are made. The most appropriate diet formulated and tested effected a 21 to 29.9 percent saving compared to the currently available feeds in South Africa.
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  • Date Issued: 1988

Jazz with Chris McGregor

  • Authors: Unknown
  • Subjects: McGregor, Chris--1936-1990 , Jazz
  • Language: French
  • Type: Article
  • Identifier: vital:13718 , http://hdl.handle.net/10962/d1012730
  • Description: Photocopied article from the French newspaper Le Petit Bleu de Lot-et-Garonne about 2 solo performances in Penne-d'Agenais by Chris McGregor on the piano.
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Colour and sculpture : an investigation into the use of two dimensional media in sculpture

  • Authors: Wright, Jeanne
  • Date: 1988
  • Subjects: Sculpture -- Technique Sculpture -- History Color in art
  • Language: English
  • Type: Thesis , Masters , MFA
  • Identifier: vital:2436 , http://hdl.handle.net/10962/d1004783
  • Description: From Introduction: Creative images which are normally called 'art' can be distinguished as either 'plastic' or visual. Both these forms throughout the history of art have relied to a greater or lesser degree on the use of colour. It is my intention to investigate specifically the changing role which colour has played in sculpture - the 'plastic' media of the visual arts and to chart the technical and aesthetic reasons for the use of colour. This investigation will encompass the historical perspective, the material qualities, aesthetic considerations, transitional codes and methods of approach in sociological frameworks and the examination of colour as a metaphysical element in the presentation of three dimensional media.
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  • Date Issued: 1988

Jazz: Chris McGregor in Villeneuve

Mukavango

Kristos kwavali kile masacrament

Title not specified

The petrology, mineralogy and geochemistry of the main zone of the Bushveld Complex at Rustenburg Platinum Mines, Union Section

  • Authors: Mitchell, Andrew Alexander
  • Date: 1988
  • Subjects: Mineralogy -- South Africa Petrology -- South Africa Rustenburg Platinum Mines Geochemistry -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4903 , http://hdl.handle.net/10962/d1001563
  • Description: Union Section of Rustenburg Patinum Mines is situated in the northwestern part of the Bushveld Complex, some twenty kilometres north of the Pilanesberg Alkaline Complex. The mining lease area covers a roughly triangular segment of Lower, Critical and Main Zone rocks, transgressed to the north and south by magnetite-bearing ferrogabbro of the Upper Zone. The Main Zone at Union Section is the focus of this study. The prime source of sample material for the study is the deep exploration borehole SK2, but additional, supplementary samples were collected on surface and underground, as well as from a second surface exploration borehole, SK4. In line with the recommendations of SACS (1980), the top of the Critical Zone, and therefore the base of the Main Zone, is taken to be the top of the Bastard Cyclic Unit. Sharpe (1985) suggested that the succession from the base of the Main is an isotopically separate entity Zone up to the Pyroxenite Marker from the rest of the Bushveld layered succession. This is not strictly true, as there is evidence that more than one parental magma was involved in the formation of this interval. It is, however, true that there are fundamental differences, particularly in isotopic makeup, between the Main Zone rocks below the pyroxenite Marker and those above (the latter having been assigned by Molyneux (1970) to subzone C of the Main Zone). Kruger et al. (1986, in press) suggested that the Pyroxenite Marker marks the base of the Upper Zone, and this convention is adhered to here. The implication of this is that the rocks which formerly constituted subzone C of the Main Zone are now considered part of the Upper Zone. The Main Zone rocks below the pyroxenite Marker were originally subdivided by Molyneux (1970) into two subzones, A and B. The results of the present study indicate that this subdivision is not justified. Instead, eight units have been distinguished in the Main Zone on geochemical, petrological and mineralogical bases. Each of these units is characterized by a coherent set, or progression, of chemical and petrological characteristics. The specific assignment of genetic connotations to these units has been deliberately avoided , at least until further studies of the Main Zone prove this to be justified. The demarcation of the eight units is illustrated in the composite diagram (Fig. 34) in the back pocket of this work, and the reasons for the subdivisions are listed in Table 6 (at the end of chapter 7 of this thesis). Until the late 1970's, it was thought that most layered cumulates formed by crystal settling (Wager and Brown, 1968). More recently, there has been a fundamental conceptual change, and many workers now believe that most cumulate rocks formed by in situ crystallization at the floor and walls of the magma chamber (McBirney and Noyes, 1979, Irvine, 1980a; Campbell, 1987). There is, however, some evidence for the physical separation of phases undergoing cotectic crystallization, particularly in the Upper Critical Zone and lower part of the Main Zone (Eales et al., 1986). This process, which has been alluded to in the past by various authors (Ferguson and Botha, 1963; Vermaak, 1976) involves the flotation of early-formed plagioclase crystals due to their positive bouyancy in tholeiitic liquids. The result is an apparent decoupling of the chemistry of pyroxene and plagioclase, as in unit IV of the Main Zone, where plagioclase becomes more anorthitic upwards, whilst pyroxene becomes more iron-rich. There is some substantial evidence, particularly in reversals in the strontium isotope initial ratio and the orthopyroxene Mg/(Mg+Fe) ratio , for multiple intrusion in the Main Zone. Although the largest and most important magma influx in the Main Zone was a high-R₀ aluminous tholeiite, as suggested by Sharpe (1985), the intrusive history of the Main Zone is believed to be far more complex than Sharpe (op. cit.) suggested. Significantly, there is strong evidence for small influxes of Upper Zone-type (Fe-rich tholeiite) magma in the upper reaches of the Main Zone. These are believed to be precursors to the major influx of Upper Zone-type magma at the pyroxenite Marker (Kruger et al, 1986, in press). The fate of intercumulus liquids in cumulate rocks has recently recieved substantial attention (Sparks et al., 1985; Morse, 1986; Barnes, 1986: Campbell, 1987). It is believed that the migration, or at least redistribution, of intercumulus liquids has played a vital role in modifying fractionation trends in the Main Zone. More importantly, the accumulation of late-stage intercumulus liquids is believed to be responsible for the formation of the Fe-rich ultramafic pegmatite bodies that interrupt the layered cumulates in borehole SK2 , Adobe Acrobat 9.53 Paper Capture Plug-in
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  • Date Issued: 1988

Polymerized serum albumin beads for use as slow-release adjuvants

  • Authors: Martin, Michelle Elizabeth Denny
  • Date: 1988
  • Subjects: Serum albumin , Antigens , Vaccines
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3879 , http://hdl.handle.net/10962/d1001613
  • Description: Experimental vaccines have been made by covalently bonding virus particles into polymerized rabbit serum albumin beads. Using Nodamura virus as a model antigen, these model vaccines induced specific humoral antibody production, comparable with that achieved using Freund's adjuvants. Virus specific antibodies were also induced when Nodamura virus was covalently attached to the bead surface using different crosslinkers. However, when poliovirus type 2 (Sabin strain) was polymerized into beads, the levels of neutralizing antibodies were insignificant compared with control aqueous vaccines. The synthetic immunostimulator, muramyl dipeptide, was included with bead vaccines in an attempt to potentiate the immune response. Immunostimulation is achieved by a slow release of antigen coinciding with the gradual breakdown of bead structure.
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  • Date Issued: 1988

John Chrysostom's understanding of the Eucharist in its relation to the Christian life

  • Authors: Amos, Charles Harry
  • Date: 1988
  • Subjects: John Chrysostom, Saint, d. 407 , Lord's Supper , Lord's Supper -- Biblical teaching
  • Language: English
  • Type: Thesis , Masters , MTh
  • Identifier: vital:1217 , http://hdl.handle.net/10962/d1001547
  • Description: The aim of this thesis is to reveal the intimate relationship between John Chrysostom's Eucharistic theology and the christian life, and that at the Eucharist Man's true being is demonstrated. It investigates Chrysostom's exegetical and oratorical method in order to ascertain how he approached a text and how he delivered his understanding of it. He is a representative of the Antiochene School of Exegesis and his fame as a preacher was a result not so much of his oratorical construction, but of the underlying spiritual unity within the oration. The purpose of all his preaching and exegesis was to evoke a moral response from his hearers. In the consecration of the elements, Chrysostcm displayed a remarkable openness to the varying traditions. He saw reciting the words of institution and invoking the Spirit as effecting consecration. Not only this, but also the moral life of the congregation played its part in effecting consecration. Once the elements had been consecrated, Christ was sacrificed, symbolically and literally, not again but in memory (Greek letters) of the Passion, which thereby becomes a present reality. In Chrysostom's understanding of the real presence he displays yet again an openness to the traditions. Christ is both present symbolically through the elements and literally through the transformation of the elements. The real presence demanded of the communicant a high degree of morality. To approach the Table on which Christ lay demanded a life of virtue, not only from the individual communicant but from the whole community. Those who partook unworthily imitated Judas and shared his fate. The community had to approach the Table in unity. At the Table, however, the community received its unity from Christ, the community became the body of Christ. Through participation and becoming the body of Christ, the community was united with the Godhead . Schism, therefore, was a very serious sin for it tore the body of Christ apart. For Chrysostom, Christ was also present in and intimately united with the poor. The church had to be able to be aware of Christ's presence in the poor and be responsible toward Him. In giving to the poor, the communiicant acknowledged that he/she had received at the Table and also received his/her salvation from Christ through the poor. The whole Eucharistic feast not only fed the christian with spiritual food, but called the communicant away from gross materialism to a life-giving dependance on God. It called the communicant to give to others as he/she had received from Christ.
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  • Date Issued: 1988
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