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Analysis of macrolide antibiotics

- Kanfer, Isadore, Skinner, Michael F, Walker, Roderick B

  • Authors: Kanfer, Isadore , Skinner, Michael F , Walker, Roderick B
  • Date: 1998
  • Language: English
  • Type: Article , text
  • Identifier: vital:7011 , http://hdl.handle.net/10962/d1008394 , http://www.sciencedirect.com/science/article/pii/S0021967398002763
  • Description: The following macrolide antibiotics have been covered in this review: erythromycin and its related substances, azithromycin, clarithromycin, dirithromycin, roxithromycin, flurithromycin, josamycin, rokitamycin, kitasamycin, mycinamycin, mirosamycin, oleandomycin, rosaramicin, spiramycin and tylosin. The application of various thin-layer chromatography, paper chromatography, gas chromatography, high-performance liquid chromatography and capillary zone electrophoresis procedures for their analysis are described. These techniques have been applied to the separation and quantitative analysis of the macrolides in fermentation media, purity assessment of raw materials, assay of pharmaceutical dosage forms and the measurement of clinically useful macrolide antibiotics in biological samples such as blood, plasma, serum, urine and tissues. Data relating to the chromatographic behaviour of some macrolide antibiotics as well as the various detection methods used, such as bioautography, UV spectrophotometry, fluorometry, electrochemical detection, chemiluminescence and mass spectrometry techniques are also included.
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  • Date Issued: 1998

Analysis of selected choral works by John Tavener with particular reference to the post-1977 works

- Imrie, Sally

  • Authors: Imrie, Sally
  • Date: 1998
  • Subjects: Tavener, John Choral music
  • Language: English
  • Type: Thesis , Masters , MMus
  • Identifier: vital:2642 , http://hdl.handle.net/10962/d1002307
  • Description: This thesis deals with sacred choral music written by John Tavener, a British composer born in 1944. It touches briefly on the background of Tavener and his early works (i.e. from about 1960-1976) - two works from that period have been selected for analysis, Celtic Requiem and Nomine Jesu. The main body of the thesis is concerned with those works composed,.after 1977, which show the influence of the Orthodox Church and Byzantine hymnography on Tavener's stylistic development. The selected works from this period to be analysed are: Ode of St Andrew of Crete, Two Hymns to the Mother of God, Magnificat, Nunc Dimittis, The Uncreated Eros, Eonia and We Shall See Him As Heis.
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  • Date Issued: 1998

Annotated records of blackfly (Diptera: Simuliidae) distribution in southern Africa

- Palmer, R W, de Moor, Ferdy C

  • Authors: Palmer, R W , de Moor, Ferdy C
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/452114 , vital:75104 , https://hdl.handle.net/10520/AJA10213589_229
  • Description: Regional and catchment distributions of blackflies (Diptera: Simuliidae) in southern Africa are presented and discussed relative to the biology and environmental preferences of the aquatic stages. Distribution data are based on all known records, both published and unpublished. Thirty nine blackfly species are recorded: 13 are widespread with no particular geographical affinities, 18 are restricted in distribution and eight are rare. Distributions are closely related to downstream changes in rivers, although eight species are endemic to parts of the southern and southwestern Cape, while eight are absent from the southern and southwestern Cape.
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  • Date Issued: 1998

Armee Mali

- Dieneba Seck (lead vocal, chorus), Nanou Coul, Wande Kouyate, Yves Ndjock (chorus), Djely Moussa Kouyate (rhythm guitar), Tom Toumani Diakite (ngamole, ngomi, percussion), Thio Mbaye (percussion, djembe, tama), Maka Tounkara "Badie" (ngomi), Jean Luc Pinot (violon), Ben's Belinga (saxophone), Yves Ndjock (bass, snare drum, guitar), Syllart Production

Aspects of renormalisation in some quantum field theories

- Roy, Alan A

  • Authors: Roy, Alan A
  • Date: 1998
  • Subjects: Quantum field theory , Renormalization group
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5400 , http://hdl.handle.net/10962/d1005214 , Quantum field theory , Renormalization group
  • Description: Renormalisation is an important aspect of Quantum Field Theory. It is used to create physically meaningful theories and some major developments took place in the 1970's and onwards. We consider Renormalisation in its application to the theories of ψ⁴ , Quantum Electrodynamics, Quantum Chromodynamics and the Background Field Method. Feynman diagrams are used to illustrate many of the concepts.
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  • Date Issued: 1998

Aspects of the biology of the doublesash butterflyfish, Chaetodon marleyi (Pisces: Chaetodontidae)

- Vine, Niall Gordon

  • Authors: Vine, Niall Gordon
  • Date: 1998
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:21103 , http://hdl.handle.net/10962/6396
  • Description: The doublesash butterflyfish, Chaetodon marleyi, indigenous to South Africa, is popular amongst marine aquarists. To provide a basis for the management of the species and assess its suitability for aquaculture, aspects of its biology were investigated. Specimens were collected between February 1996 and November 1997 from localities along the eastern Cape coastline of South Africa and from specimens in the RUSI fish collection. The dentition of C.marleyi is typical of non-coraline, benthic invertebrate feeding chaetodontids. The teeth are long, inwardly hooked and spatulate which allow easy grasping and manipulation of the prey. Stomach content analysis showed that the species fed predominantly on the tentacles of terebellid polychaetes with other polychaetes, crustaceans, hydro ids and ascideans contributing to the remainder of the diet. Juveniles had a larger volume of terebellid tentacles compared to adults which preyed more upon other polychaetes. The proximate composition (64.25% protein, 4.76% fat, 4.84% carbohydrate and 24.3 kJ/g total energy content) of the terebellid tentacles was determined suggesting a high energetic requirement of the fish or maximisation of feeding profit rates.
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  • Date Issued: 1998

Aspects of the ecology and reproductive biology of three cichlid fish species of Southern Lake Malombe (Malawi)

- Jambo, Collins Mayeso

  • Authors: Jambo, Collins Mayeso
  • Date: 1998
  • Subjects: Cichlids -- Africa, East -- Lake Malombe , Cichlids -- Ecology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5224 , http://hdl.handle.net/10962/d1005067 , Cichlids -- Africa, East -- Lake Malombe , Cichlids -- Ecology
  • Description: The three major species Lethrinops ''pinkhead'', Otopharynx argyrosoma "red" and Copadichromis. cf virginalis which used to dominate the catches (by weight) of Lake Malombe in the past decade were investigated. In order to make rational recommendations regarding size and boundary of the existing sanctuary area (lightly fished), distribution and abundance, population structure and reproductive biology of the three species were related to habitat types of the southern part of the lake (south western side and south eastern side). Analysis of catch composition showed that species richness was higher in the south eastern side than in the south western side of the lake. Rare species such as Labeo mesops and Opsaridium microiepis were observed in the south eastern side and there was visual absence of such species in the south western side of the lake. The overall fish abundance was significantly greater in the south eastern side than in the south western side of the lake. In the south eastern side, the catch per unit effort (CPUE) was twice that of the south western side (P< 0.05). Seasonal fluctuations in CPUE were also prominent, with the highest peak occurring during September-October period. However, there was an indication of weak relationship among CPUE, phytoplankton biomass, temperature and water depth. The length-weight relationships revealed that growth of the three species closely followed the cubic law for isometric growth in both sides of the lake. Differences in regression coefficients between sides were not significant (ttest, P>0.05). The length-frequency distribution analysis revealed that the three species had the same growth rate regardless of habitat type. However, females grew faster than males. An investigation of reproductive biology showed that the three species have low fecundity and they are asynchronous spawners, with a breeding peak during August and September period. Furthermore, the length-fecundity relationships for L. ''pinkhead'', and 0. argyrosoma "red" indicated that fecundity was more closely related to length in the south eastern side than in the south western side. Based on the above characteristics of L. ''pinkhead'', 0. argyrosoma "red" and C. cf virginalis, and the substrate types, it was strongly suggested that the existing sanctuary (lightly fished) in the south eastern side of the lake could immediately be enlarged to conserve the fish stocks, favourable substratum and aquatic animals that may be of tourists concern.
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  • Date Issued: 1998

Assi Olivier

- TP Audiorama Orchestra (performers), Showbiz

  • Authors: TP Audiorama Orchestra (performers) , Showbiz
  • Date: 1998
  • Subjects: Popular music , Popular music--Africa, West , Africa Cote d'Ivoire Abidjan f-iv
  • Language: French
  • Type: sound recordings , field recordings , sound recording-musical
  • Identifier: http://hdl.handle.net/10962/129606 , vital:36312 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC30-07
  • Description: Ako music from Cote d'Ivoire performed by the TP Audiorama Orchestra, the first orchestra to develp this genre of Ivorian music
  • Full Text: false
  • Date Issued: 1998

Asymmetric induction in reactions of chiral carboxylic esters and silyl enol ethers

- Evans, Melanie Daryl

  • Authors: Evans, Melanie Daryl
  • Date: 1998
  • Subjects: Ethers -- Synthesis Esters -- Synthesis Chirality Asymmetric synthesis Organic compounds -- Synthesis
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4409 , http://hdl.handle.net/10962/d1006762
  • Description: Several camphor and pinane derivatives have been synthesised and evaluated for use as chiral auxiliaries in asymmetric synthesis. Various blocking groups have been attached to the camphor skeleton in attempts to improve stereofacial selectivity; these include α-methoxybenzyl and xylyl groups, and novel stereoisomeric ketal moieties derived from meso- and (R,R)-(-)-2,3-butanediol. Benzylation reactions carried out on the lithium enolates of ester derivatives of the camphor-derived chiral auxiliaries afforded α-benzylated products in 5-60% diastereomeric excess. Stereochemical aspects have been explored using high resolution NMR, X-ray crystallographic and computer modelling techniques, and hydrolysis of selected α-benzylated products has permitted the diasteroselective bias to be confirmed. Opposite configurations at the new stereogenic centre are clearly favoured by the xylyl and ketal blocking groups - an observation rationalised in terms of the presence or absence of chelating potential in the blocking group. Baylis-Hillman reactions carried out on a series of specially prepared camphor-derived acrylic esters containing the ketal blocking group exhibited both low diastereoselectivities (0-30% d.e.) and very long reaction times. Chiral silyl enol ethers, synthesised using both pinane and camphor derivatives as chiral auxiliaries, showed up to 20% diastereomeric excess in MCPBA oxidation, alkylation and Mukaiyama reactions. Attempts to bring the prochiral centre in the silyl enol ether substrates closer to the chiral auxiliary, and thus improve the stereofacial selectivity, proved unsuccessful. The silyl enol ether derivatives, however, display interesting fragmentation patterns in their electron impact mass spectra, which were investigated using a combination of high resolution MS, comparative low resolution MS and metastable peak analysis.
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  • Date Issued: 1998

At play in the master's workshop: the experience of reading in the novels of Henry James

- Seddon, Deborah Ann

  • Authors: Seddon, Deborah Ann
  • Date: 1998
  • Subjects: James, Henry, 1843-1916 -- Criticism and interpretation
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2278 , http://hdl.handle.net/10962/d1007451 , James, Henry, 1843-1916 -- Criticism and interpretation
  • Description: James's belief that "it is art that makes life" is essential to his own literary technique and to the reading experience within and in relation to his novels. The thesis seeks to posit the notion of reading as a fundamental concern in Henry James's fiction. Drawing largely on the phenomenological and anthropological approaches to the reading process of Wolfgang Iser, this thesis examines the Jamesian text as a performative event involving author, reader and character in creative and interpretative narrational struggles. Iser uses "play" as an integral term to describe the dynamic between author-reader-text which produces a literary work of art. In James's fiction the doubling of the author/reader and reader/character role within the text crucially structures a narrative form which is itself an inquiry into the human use of fiction. The Iserian conception of the act of reading as an engagement with the "gaps" within the play-space of the literary text can elucidate James's structural and thematic use of such sites of indeterminacy to foreground the enlivening necessity of an indeterminate "felt life" within human narrative structures. What Maisie Knew highlights the most important rule in the game -- the necessity for the reader to create meaning from the indeterminate aspects of the text. The shared exercise for author-reader-character is the attempt to access the child's unformulated inner reality to ascertain what Maisie knows. In the section on The Portrait of a Lady Iser's notion of reading as an ideational activity aids an inquiry into the human use of mental fictive picturing to compose reality. The Ambassadors demonstrates the "anthropological" need for the particular mode of consciousness brought about by the literary text when we engage in a world as real as but different to our own. Strether is the reader's ambassador in this world and his interpretative activity mirrors the reader's quest. In The Golden Bowl the bewildering multiplicity of readings made possible by the indeterminate aspects of the literary text instigates a contest for narrative forms in which the chosen fictions of the readers/characters must be actively willed into existence.
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  • Date Issued: 1998

Atikoro

- Dieneba Seck (lead vocal, chorus), Nanou Coul, Wande Kouyate, Yves Ndjock (chorus), Djely Moussa Kouyate (rhythm guitar), Tom Toumani Diakite (ngamole, ngomi, percussion), Thio Mbaye (percussion, djembe, tama), Maka Tounkara "Badie" (ngomi), Jean Luc Pinot (violon), Ben's Belinga (saxophone), Yves Ndjock (bass, snare drum, guitar), Syllart Production

Atterrissage

- TP Audiorama Orchestra (performers), Showbiz

  • Authors: TP Audiorama Orchestra (performers) , Showbiz
  • Date: 1998
  • Subjects: Popular music , Popular music--Africa, West , Africa Cote d'Ivoire Abidjan f-iv
  • Language: French
  • Type: sound recordings , field recordings , sound recording-musical
  • Identifier: http://hdl.handle.net/10962/129611 , vital:36313 , International Library of African Music, Rhodes University, Grahamstown, South Africa , SDC30-08
  • Description: Ako music from Cote d'Ivoire performed by the TP Audiorama Orchestra, the first orchestra to develp this genre of Ivorian music
  • Full Text: false
  • Date Issued: 1998

Bagoogonnou

- Kenza Batoma Diallo (author, composer, lead singer), Aliou Traore (violin), Benogo Diakite (ngoni, kangnan), Kabin Kaba Diakite (guitar, bass, yabara), Halima Sangare (chorus), Souleymane Dembele (balafon), Kalibou Diarra (djembe), MALI K7 S.A. Ali Furka Toure Associe, Bamako

Barrier-free tourism in the natural environment for people with physical disabilities with specific reference to Eastern Cape facilities

- Chapman, Sally Lynn

  • Authors: Chapman, Sally Lynn
  • Date: 1998
  • Subjects: People with disabilities -- Travel -- South Africa , People with disabilities -- Services for -- South Africa , Game reserves -- South Africa -- Eastern Cape , Trails -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSocSc
  • Identifier: vital:693 , http://hdl.handle.net/10962/d1006384 , People with disabilities -- Travel -- South Africa , People with disabilities -- Services for -- South Africa , Game reserves -- South Africa -- Eastern Cape , Trails -- South Africa -- Eastern Cape
  • Description: Social workers are becoming increasingly involved in community projects, thus allowing them to reach more people. One of these areas involves the sensitising of society in the removal of barriers which prevent people with disabilities from living balanced and integrated lives. One aspect requiring particular attention is the natural environment which, until recently, has been neglected. In order to increase the knowledge of the researcher in the field of environmental accessibility, twenty six people with physical disabilities were interviewed to ascertain which factors they saw as important and relevant when assessing the natural environment. Their ideas were incorporated into practical assessments of a game reserve and a possible hiking trail for people with disabilities. As it is of vital importance to include the consumers in studies of this nature, selected people with varying abilities and disabilities assisted in these "hands on" studies. Qualitative interviews were also conducted on the owners of facilities who were in the process of making their facilities accessible. This allowed the researcher and selected people with disabilities to evaluate positive and negative experiences, thus adding to their knowledge base and building capacity for people with disabilities
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  • Date Issued: 1998

Baylis-Hillman derived benzopyrans and related systems : a synthetic and mechanistic study

- Robinson, Ross Stuart

  • Authors: Robinson, Ross Stuart
  • Date: 1998
  • Subjects: Benzopyrans Coumarins Heterocyclic compounds -- Derivatives
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4429 , http://hdl.handle.net/10962/d1007193
  • Description: The Baylis-Hillman reaction between substituted salicylaldehydes and various acrylate species has been shown to afford complex reaction mixtures, careful chromatography of which has led to the isolation of an extensive range of novel compounds. One- and two-dimensional NMR spectroscopic, mass spectrometric and X-ray crystallographic analysis of these compounds have permitted identification of no less than eight general classes of chromene and coumarin derivatives. The formation of the various product types is attributed to cascades of successive reactions stemming, in each case, from a Baylis-Hillman product as the common intermediate. The mechanistic sequence involved in the formation of the various chromene and coumarin derivatives have been elucidated by examining isolated or specifically prepared compounds as putative reaction intermediates. Conjugate addition and acyl or allylic substitution by various nucleophiles appear to be common processes in the formation of the chromene and coumarin derivatives, and studies focussing on these processes have been undertaken. Reactions of Baylis-Hillman adducts have been carried out, using oxygen, sulfur and nitrogen nucleophiles, in order to explore stereoselectivity and regioselectivity trends. The results show that the reactions proceed with a very high degree of regioselectivity, affording conjugate addition rather than acyl substitution products. The diastereoselectivity observed for the addition products, however was typically low. A kinetic study to explore the regioselectivity of the reaction between various Baylis-Hillman derived halogeno esters and the nucleophile, methyl 3-oxobutanolate enloate, in two different base-solvent systems at high dilution was also undertaken. The reactions were monitored by ¹H NMR spectroscopy, and the results revealed that the reaction kinetics are more complex than originally anticipated. A mechanistic rationalisation is offered which is consistent with both the kinetic data and the observed regioselectivity trends.
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  • Date Issued: 1998

Be Kou Will Konke

- Kenza Batoma Diallo (author, composer, lead singer), Aliou Traore (violin), Benogo Diakite (ngoni, kangnan), Kabin Kaba Diakite (guitar, bass, yabara), Halima Sangare (chorus), Souleymane Dembele (balafon), Kalibou Diarra (djembe), MALI K7 S.A. Ali Furka Toure Associe, Bamako

Bioequivalence testing of topical dermatological formulations, the gap between science and legislation

- Schwarb, Fabian P, Smith, Eric W, Haigh, John M, Surber, Christian

  • Authors: Schwarb, Fabian P , Smith, Eric W , Haigh, John M , Surber, Christian
  • Date: 1998
  • Language: English
  • Type: Conference paper
  • Identifier: vital:6341 , http://hdl.handle.net/10962/d1006608
  • Description: Bioavailability concerns for topical dermatological products are complex and it is especially difficult to determine the bioequivalence of similar topical formulations. Since only small amounts of drug dispersed in an appropriate vehicle are applied to the skin, the amount of drug that actually reaches the systemic circulation is often too small to be easily quantified. Additionally, it can be argued that the relevance of any serum/plasma concentration-time curve of a topical agent is questionable, since the curve reflects the amount of drug after the active moiety has left the site of action. For some topical drugs e.g., topical corticosteroids, it is possible to perform a pharmacodynamic bioassay to obtain acceptable bioequivalence data. In this case, the intensity of the side effect of blanching (vasoconstriction) in the skin caused by topical corticosteroids can be measured. The response is directly proportional to the clinical efficacy, and the skin blanching assay has proved to be a reliable procedure for the determination of topical corticosteroid bioavailability. Recently, we had sight of the results of a topical bioequivalence study, which was conducted for the registration of a new generic corticosteroid cream formulation. In this trial the new formulation was compared to two equivalent product from the local market and bioequivalence was demonstrated by the investigators for all three products. These results were examined with interest as the respective reference products have been used repeatedly as standard formulations in our laboratory. However, one of these reference formulations has consistently shown superior bioavailability in our trials, but was not demonstrated to be superior in the study results examined. In the present publication an overview of topical bioequivalence testing in general is given and the difficulties occurring in practice, for topical corticosteroid formulations in particular, are demonstrated.
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  • Date Issued: 1998

Biology and management of the Cape gurnard, Chelidonichthys capensis (Order Scorpaeniformes, Family Triglidae) in South Africa

- McPhail, Amanda Sue

  • Authors: McPhail, Amanda Sue
  • Date: 1998
  • Subjects: Scorpaeniformes
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5236 , http://hdl.handle.net/10962/d1005079 , Scorpaeniformes
  • Description: The South African demersal trawl fishery, as with most trawl-directed fisheries worldwide, has a substantial bycatch component. With increasing commercial emphasis being placed on retained bycatch, an urgent need has arisen to investigate these species. In the past the bycatch component has received little research or management attention. Members of the gurnard family Triglidae make up up to 2.4 % of the South African hake-directed demersal catch and are thus considered an important bycatch species. The catch history and biology, including population structure, reproduction, feeding, age, growth and mortality, of the Cape gurnard, Chelidonichthys capensis, sampled from the Agulhas Bank, South Africa, were thus investigated. Males (mean TL = 366mm) were significantly smaller than females (mean TL = 411mm). The sex ratio was close to parity, males being more dominant in commercial trawls and less dominant in research trawls. Gonad maturation and gonadosomatic indices showed this species to have an extended spawning period with peaks in reproductive activity during September, January and April. First approximations of size at 50 % maturity were similar for females (349mm TL) and males (348mm TL) but differed significantly in terms of age (3.6 years and 4.6 years respectively). Otolith growth marks were validated as annuli using marginal zone analysis. The maximum age estimated was 16 years for a female of 675mm TL and recruitment to the commercial fishery was estimated as taking place in the fifth year of growth for both males and females. Gut content analysis showed C. capensis to be an opportunistic feeder preying preferentially on the benthic crustaceans Goneplax angulata and Mursia cristimanus. Landings from the commercial linefishery were insignificant whilst those for the commercial trawl fishery ranged from 500 tonnes to 3250 tonnes between 1984 to 1995, and indicated that this species forms an important component of the South African trawl fishery bycatch. A first approximation of fishing mortality (0.36 year⁻¹) for the inshore commercial trawl fishery was higher than that of natural mortality (0.25 year⁻¹) suggesting some fishing pressure on this species on the Agulhas Bank. However this fishing mortality value was significantly less than that for F₀·₁ (4.78 year⁻¹) that was estimated using a yield-per-recruit model.
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  • Date Issued: 1998

Biology, stock assessment and management of the panga Pterogymnus laniarius on the Agulhas Bank, South Africa

- Booth, Anthony John

  • Authors: Booth, Anthony John
  • Date: 1998
  • Subjects: Fish stock assessment -- South Africa Bycatches (Fisheries) -- South Africa Pterogymnus laniarius Fishery management -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5242 , http://hdl.handle.net/10962/d1005085
  • Description: The panga, Pterogymnus laniarius (Cuvier, 1830), is a South African endemic sparid fish species. On the Agulhas Bank, South Africa it is a commercially important species, caught as bycatch in the hake directed trawlfisheries and targeted by offshore hook-and-linefishers. Recently there has been considerable interest shown in directing further fishing effort on this species. The lack of a suitable management procedure for teleost bycatch in South Africa was the principal reason for undertaking this study. This thesis investigates aspects the panga's life history, particularly those aspects that have management implications. A full knowledge of this species' distribution and abundance was necessary as this could highlight the existence of any nursery areas, ontogenetic migratory patterns and areas of high spawner biomass. The derived parameter estimates were then included as inputs into stock assessment models to determine the status and productivity of the resource. Growth studies based on sectioned sagittal otoliths revealed that the panga was a relatively slow growing fish with ages of 16 years being recorded. Growth was best described by the von Bertalanffy growth model as Lt=379.4(1-e⁻°·¹³⁽t ⁺ ¹·⁷⁸⁾). Total, natural and fishing mortalities were estimated at 0.36 year⁻¹, 0.28 year⁻¹ and 0.08 year ⁻¹, respectively. Detailed histological examination of the gonads revealed that panga is a late gonochorist, males and females maturing after a non-functional intersexual stage. Females mature at approximately 200 mm fork length or 4 years of age. Reproduction occurs throughout the year although there is a slight peak in winter. Gametogenesis was found to be similar to that of other sparid fishes and marine teleosts in general. The panga feeds predominantly on crustaceans with a distinct ontogenetic shift in feeding habits. Juvenile fish feed predominantly in the water column on mysids after which they move to the benthos. Subadult fish feed principally on ophiuroids and amphipods. Adult fish remain on or near the benthos, feeding predominantly on crabs, and on polychaetes, ophiuroids and fishes to a lesser extent. Several aspects of the panga's biology contribute to its ability to sustain a higher fishing pressure than other sympatric sparid species. These include its late gonochoristic reproductive style, protracted spawning season, maturation before recruitment and preference for soft substratum prey that enables it to utilise large areas of the Agulhas Bank. The panga's longevity, slow growth and low natural mortality rate, however, mitigated against these factors and were considered in the stock assessments. A heterogeneous Geographical Information System (GIS) was developed to analyse the distribution and abundance patterns of the panga. The GIS developed in this thesis makes a significant contribution towards the development of a South African Fisheries Information System to analyse and manage fish resources in general and bycatch resources in particular. The GIS developed in this study combines statistical Generalized Additive Modelling and standard GIS methods. Analysis of fourteen biannual fishery independent biomass surveys, disaggregated by life history stage, revealed that a nursery area for immature fish (<23 cm TL or < 4 years of age) exists on the Central Agulhas Bank. After sexual maturation, approximately 40% of the biomass migrated eastwards, colonising large areas of the Eastern Agulhas Bank.ilie location of the nursery area appears to be a result of the pelagic eggs and larvae being advected towards the coast in an anti-cyclonic gyre, stemming off the Agulhas current and later deposited over the Central Agulhas Bank. The weak bottom currents on the Central Agulhas Bank prevented juvenile loss to the Benguela system. The eurytopy of adult fish to various physical variables such as temperature, dissolved oxygen and stronger currents enabled it to reduce conspecific competition and migrate eastwards with distribution primarily determined by depth. Relative biomass estimates revealed a gradual increase in biomass of 5.5% per annum between 1988 and 1995. Predictions from yield-per-recruit, biomass-per-recruit and spawner biomass-per-recruit analyses showed that there was scope for further exploitation. A FSB₅₀ fishing strategy was considered to be the most appropriate fishing strategy as it did not reduce the spawner biomass-per-recruit to less than 50% of unexploited levels. Effort control was considered the most effective management tool as the age-at-50%-selectivity occurred after age-at-sexual maturity and releasing undersized fish was undesirable due to heavy mortalities resulting from severe barotrauma. The panga resource was also assessed using an age-structured production model. The values for the free parameters of the model were estimated using biomass indices derived from fishery-independent trawl surveys. Although the data were fairly uninformative about the productivity of the resource, the results indicated robustly, that the population has recovered from low levels in the mid-1970's and could sustain higher levels of fishing intensity. Risk analysis calculations were used to assess the sustainability of different catch scenarios. The level of sustainable catch was found to be sensitive to the selectivity pattern of the gear utilised. Both stock assessment methods used in this study to investigate the status of the panga resource showed that the resource could theoretically sustain higher catches. It was found that although the stock could be harvested using available fishing methods, the sympatry of this species with other commercial species was of concern as the latter would form a significant bycatch in a panga directed fishery. The failure of current harvesting methods to address the bycatch problem highlights the management problem in South Africa and stresses the need for creativity by both scientists and fishers in designing new and improved methods for selectively harvesting bycatch fish resources. Considering that no suitable method is currently available to fish the panga stock in a directed fishery the fishery should be managed as status quo until some suitable and efficient gear is developed.
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  • Date Issued: 1998

Camphor-derived chiral auxiliaries in asymmetric synthesis

- Molema, Warner Evert

  • Authors: Molema, Warner Evert
  • Date: 1998
  • Subjects: Asymmetric synthesis Chirality Camphor
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4417 , http://hdl.handle.net/10962/d1006848
  • Description: The investigation has been focussed largely on the chemistry and stereo-directing potential of camphor-derived compounds. The major regioisomer produced on partial hydrolysis of N-benzylcamphorimide was identified, by one- and two-dimensional NMR and X-ray crystallography, as (+)-(1S,3R)-(N-enzylcarbamoyl)-2,3,3-trimethylcyclopentanecarboxylic acid, the methyl ester of which was shown to undergo an unexpected intramolecular rearrangement during LAH reduction to afford (1S,3R)-Nbenzyl-3-hydroxymethyl-2,2,3-trimethylcyclopentane carboxamide. Several tartrate- and camphor-derived diols have been investigated as chiral auxiliaries in various asymmetric reactions of corresponding acetals of α,β-unsaturated aldehydes. MCPBA epoxidation of the tartrate-derived acetals afforded epoxy acetals in 4-12% diastereomeric excess. The camphor-derived acetals were obtained solely as the exosubstituted diastereomers, the stereochemistry being confirmed by two-dimensional NMR spectroscopy and X-ray crystallography. Simmons-Smith cyclopropanation of these camphor-derived acetals afforded cyclopropyl products with diastereoselectivities of 4% d.e. for the bornane-2,10-diol acetal and 46->99% d.e. for the bomane-2,3-diol acetals. In order to increase diastereofacial selectivity, a camphor-derived diol having a bulky substituent at C-10 was prepared, viz., phenyl 2,3-dihydroxybomane-10sulfonate, and α,β-unsaturated acetals of this diol were shown to undergo Simmons-Smith cyclopropanation with complete topological control (>99% d.e.), the diastereoselectivities being conveniently determined by ¹H and ¹³C NMR spectroscopy. Computer modelling, with the software package HYPERCHEM®, was used to explore the stereochemical aspects of the Simmons-Smith cyclopropanation, and hydrolysis of one of the cyclopropyl acetals has permitted the diastereoselective bias to be confirmed. (+)-Pinane-2,3-diol was also investigated as a chiral auxiliary in the Simmons-Smith reactions of α,β-unsaturated aldehydes, and moderate diastereoselectivities (20-30% d.e.) were observed. In a series of exploratory studies, the Diels-Alder reaction of the 2,3-dihydroxybomane-10-sulfonate acetal of trans-cinnamaldehyde with cyclopentadiene afforded a single cycloadduct, while OSO₄ dihydroxylation, MCPBA oxidation and alkylation of chiral acetals produced from both bomane-2,3-diol and phenyl 2,3-dihydroxybomane-10-sulfonate were less selective.
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  • Date Issued: 1998
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