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Entrance song

- Our Lady of Africa Congregation, Composer not specified, Dargie, Dave

Environmental requirements for the hatchery rearing of African catfish Clarias Gariepinus (Pisces: Clariidae) larvae and juveniles

- Britz, P J (Peter Jacobus), 1959-

  • Authors: Britz, P J (Peter Jacobus), 1959-
  • Date: 1988
  • Subjects: Catfishes -- Africa , Fish culture , Clariidae , Clarias
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5188 , http://hdl.handle.net/10962/d1001964 , Catfishes -- Africa , Fish culture , Clariidae , Clarias
  • Description: Inadequate seed production has historically been a factor limiting the commercial culture of Clarias gariepinus. The need to determine the environmental requirements of larvae was identified, in order to facilitate their successful mass rearing in hatcheries. The effects of key environmental factors on the growth, survival and aspects of the behaviour of C. gariepinus larvae and juveniles were investigated under controlled conditions. A strong emphasis was placed on the interpretation of the observed responses in terms of the natural history of the animal. Larvae were obtained by artificially inducing and spawning feral adult broodfish. Larval growth rates were highest in the temperature range 26-33ºC, with a peak at 30ºC. Survival of larvae was high between 22 and 33ºC. The final temperature preferendum of juveniles, determined in a thermal gradient was 30ºC, and it was concluded that this temperature is probably optimal for most of the physiological processes of the animal. Larvae and juveniles displayed strong negative phototaxis. When reared under different photoperiod regimes, larval growth increased with longer dark periods, however a similar rate of mortality was recorded in all photoperiod treatments. The provision of cover was found to enhance larval growth under conditions of continual light (24L/OD), however under conditions of continual darkness (OL/24D) similar growth rates were recorded regardless of the presence or absence of cover. All growth rates in continual darkness (OL/24D) were higher than those in continual light (24L/OD), regardless of whether cover was provided or not. It was concluded that a OL/24D photoperiod is optimal for larval rearing. At salinities between 0 and 5% similar growth and mortality rates of larvae were recorded. At 7.5 % larval growth and survival rates were lower, and at 10 % all larvae died within 48 hours. The 96h-LCSO for unionised ammonia was found to be 2.3 mg/l. The cytological effects of unionised ammonia were evident as degenerative changes in the gill and liver tissues. In an investigation of tank hygiene, it was found that larval growth and survival rates were highest in tanks not cleaned at all. As the frequency of tank cleaning increased, the growth and survival rates of larvae decreased. When reared at densities ranging from 45-450/1, larval growth was found to be density dependent. A model of hatchery productivity (number larvae of standard size produced/time/vol.) was developed based on the density dependent nature of larval growth. The model predicts that maximum productivity, will be achieved at a rearing density of 1400/1. The high growth and survival rates obtained over a broad range of each environmental parameter investigated serve to explain how larvae survive and grow in their unstable floodplain habitat in nature. The broad environmental tolerances of C. gariepinus are of benefit with respect to the culture of larvae, as successful larval rearing is possible over a fairly wide range of environmental conditions.
  • Full Text:
  • Date Issued: 1988

Etla le tleng go utlwa

- St Joseph's Choir, Composer not specified, Dargie, Dave

Etlang Kamoka le utlwe

- Pedi Workshop Group, Composer Not Specified, Dargie, Dave

Evagedi

- All Saints Choir, Composer Not Specified, Dargie, Dave

Evangedi

- All Saints Choir, Composer not specified, Dargie, Dave

Evangeli ye ihasane

- Ngwezi Catholic Church Congregation, Composer not specified, Dargie, Dave

Exit Hymn

- St Kizito Congregation, Composer not specified, Dargie, Dave

Exit Song

- Our Lady of Africa Congregation, Composer not specified, Simasiku, John Nyambe, Dargie, Dave

Explanation in rule-based expert systems

- Carden, Kenneth John

  • Authors: Carden, Kenneth John
  • Date: 1988
  • Subjects: Expert systems (Computer science) Ecology -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4569 , http://hdl.handle.net/10962/d1002034
  • Description: The ability of an expert system to explain its reasoning is fundamental to the system's credibility. Explanations become even more vital in systems which use methods of uncertainty propagation. The research documented here describes the development of an explanation sub-system which interfaces with the P.R.O. Expert System Toolkit. This toolkit has been used in the development of three small ecological expert systems. This project has involved adapting the results of research in the field of explanation-generation, to the requirements of the ecologist users. The subsystem contains two major components. The first lists the rules that fired during a consultation. The second component comprises routines responsible for quantifying the effects on the system conclusions of the answers given to questions. These latter routines can be used to perform sensitivity analyses on the answers given. The incorporation of such routines in small expert systems is quite unique
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  • Date Issued: 1988

Extractives from six species of Lamiaceae

- Davies-Coleman, Michael Trevor

  • Authors: Davies-Coleman, Michael Trevor
  • Date: 1988
  • Subjects: Lamiaceae
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4532 , http://hdl.handle.net/10962/d1016235
  • Description: In continuation of the phytochemical studies of plants belonging to the Lamiaceae (formerly Labiatae) the acetone extractives of six Southern African species from this family have been examined. The genus Syncolostemon has not been investigated before and a new 6- substituted-5 ,6-dihydro-a-pyrone , synrotolide was isolated from S. rotundifolius. The structure of synrotolide was fully elucidated as 6fixii [3'R, 61S-(diacetyloxy)-4 1R, 5 1 8-(dihydroxy)-1~-hepteny~ -5,6-dihydro-2H-pyran- 2-one. Oleanolic acid is the major component of both~ rotundifolius and S. densifloris. The flavonol quercetin was isolated from S. densifloris as its 3, 3', 4' , 7 tetramethyl ether. A further 6-substituted-5,6-dihydro-a-pyrone, boronolide, was obtained from Tetradenia barberae. The structure of boronolide was known but the absolute stereochemistry was unassigned. Chemical degradation established the total structure of this compound as 6R- [1 'R, 2'R, 3's -(trisacetyloxy)heptyl] -5,6-dihydro-2H-pyran-2-one. The chemistry of naturally occuring 6-substituted-5,6-dihydro-apyrones has not as such been previously reviewed and a comprehensive review covering the literature up to June 1987 is presented here. Three known labdane diterpenoids nepetaefuran, hispanalone and dubiin were iso lated from Leonotis nepetaefolia, Ballota africana and L. ocymifolia var. ocymifolia (formerly~ dubia). Both~ nepetaefolia and L. dubia have been examined before. An X-ray analysis of saponified dubiin and a circular dichroism study of 6-deacetyldehydrodubiin and related compounds corroborated the structure of dubiin as 48, 5R, 6R, 8R, 9R, 10R-[6-acetoxy-15,16-epoxy-9-hydroxylabda-13 (16), 14-dien-19, 20- olactoneJ. The chemotaxonomic relationships of the genera Ballota and Leonotis are discussed.
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  • Date Issued: 1988

Famba Moses Uya Ndzi Kombeta Vona

- Mabasa, Piet, Group of men, women and children, Composer Not Specified, Dargie, Dave

Famba uya Kongela Xikwembu Xa Wena

- Mabasa, Piet, Composer Not Specified, Dargie, Dave

Feeding by larvae of the American bollworm, Heliothis armigera (Hübner) (Lepidoptera: Noctuidae) on cotton plants

- Van der Walt, Susanna Johanna

  • Authors: Van der Walt, Susanna Johanna
  • Date: 1988
  • Subjects: Cotton -- Diseases and pests , Helicoverpa armigera , Lepidoptera
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5622 , http://hdl.handle.net/10962/d1004386 , Cotton -- Diseases and pests , Helicoverpa armigera , Lepidoptera
  • Description: H. armigera larvae are a key stage for pest management in conmercial irrigated cotton crops in South Africa. Effective survey methods for detecting larval populations in the field require an understanding of the biology of the larvae, particularly their feeding habits. Their feeding is central to the development of pest threshold levels for the implementation of integrated control programmes. This applies to routine surveys for the larvae as well as to the damage they cause. Biological characteristics of the larvae are described with the emphasis on the identification of the larval instars, which were consistently five in number in both field and laboratory populations. The distribution of H. armigera larvae on cotton plants in the field was examined, but was found to more or less random; had there been a clear preference for any height zones or compass direction this would have been an obvious avenue for improving the survey methods currently in use. Details of field and laboratory investigations of the selection of feeding sites by the larvae are given. The study confirmed a clear preference by the larvae for cotton buds, flowers and bolls (in the thesis collectively called "fruiting forms"), over leaves. There were indications that the larvae selected flowers more readily than buds or bolls. This "preference", however, is shown to be of no practical value for refining survey methods. Damage levels to cotton due to B. armigera are discussed. Both direct losses and indirect losses due to the abortion of fruiting forms are considered. These criteria are inadequate since they do not take into account the ability of cotton plants to compensate for these losses. It is concluded that this compensation by cotton plants should be taken into account in further studies of the pest status of B. armigera.
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  • Date Issued: 1988

Fest-Quest 87: a survey of visitors to the 1987 Standard Bank Festival of Arts

- Davies, William J

  • Authors: Davies, William J
  • Date: 1988
  • Subjects: Art festivals -- South Africa Standard Bank National Arts Festival
  • Language: English
  • Type: Book , Text
  • Identifier: http://hdl.handle.net/10962/2304 , vital:20274 , ISBN 0868101656
  • Description: Fest-Quest '87 was an attempt to secure information from visitors to the Standard Bank National Festival of the Arts held in Grahamstown from July 3 to July 11 1987. From the outset, this was an ambitious undertaking especially in view of the kinds of people and the ambient atmosphere associated with nine hectic days of cultural injection and serious literary and artistic discourse, interspersed with revelry and novel experiences; none of which is particularly conducive to filling in a lengthy questionnaire. Nevertheless, the exercise was well worth the effort and a number of lessons have been learned about how such a survey might be better conducted in future. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
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  • Date Issued: 1988

Fishes of the family Mullidae in the Red Sea, with a key to the species in the Red Sea and the Eastern Mediterranean

- Ben-Tuvia, Adam, Kissil, Geerge Wm

  • Authors: Ben-Tuvia, Adam , Kissil, Geerge Wm
  • Date: 1988
  • Subjects: Mullidae -- Red Sea , Mullidae -- Mediterranean Sea
  • Language: English
  • Type: Text
  • Identifier: vital:15011 , http://hdl.handle.net/10962/d1019744 , ISSN 0073-4381 , ISBN 0-86810-175-3 , Ichthyological Bulletin of the J.L.B. Smith Institute of Ichthyology; No. 52
  • Description: Thirteen species of Mullidae (goatfishes or red mullets) occur in the Red Sea: Mulloides flavolineatus, M. vanicolensis, Parupeneus cyclostomus, P. forsskali, P. heptacanthus, P. macronemus, P. rubescens, Upeneus asymmetricus, U. moluccensis, U. subvittatus (previously known only from the western Pacific), 0. sulphureus, U. tragula and U. vittatus. Descriptions, biological observations and black and white photographs are given for each of these 13 species. Keys are provided to the genera of Mullidae, to the species occurring in the Red Sea, and to the two Mediterranean species of Mullus that have been reported from the Suez Canal. The distinction between the genera Pseudupeneus and Parupeneus is discussed. , Rhodes University Libraries (Digitisation)
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  • Date Issued: 1988

For you my God

- Marimba Group, Composer Not Specified, Dargie, Dave

Forever shining

- Church Choir, Composer Not Specified, Dargie, Dave

Furbitten

- Marimba Group, Composer Not Specified, Dargie, Dave

Furbitten

- Marimba Group, Composer Not Specified, Dargie, Dave

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