Colour vision of the citrus psylla Trioza erytreae (Del Guercio) (Homoptera: Psyllidae) in relation to alightment colour preferences
- Authors: Urban, Alan Joseph
- Date: 1977
- Subjects: Trioza , Homoptera , Jumping plant-lice , Color vision
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5885 , http://hdl.handle.net/10962/d1013286
- Description: The colour vision of adult citrus psylla, Trioza erytreae, was investigated in the laboratory using the behavioural parameters: alightment and walking. Light green flushing leaves (under which the nymphs develop) were significantly preferred, visually, to dark green mature leaves for alightment. Diffuse reflectance spectroscopy showed (when expressed in the parameters of human colour vision) that flush has a very slightly longer dominant wavelength, and roughly double the reflectance and purity. Alightrnent frequency correlated almost equally well with "purity" (as noted by Moericke, 1952 et seq., in "yellow-sensitive" aphids) as with the aphidological colour parameter "long/short ratio" developed by Kennedy et al. (1961). Elucidation of the mechanism underlying the citrus psylla's alightment colour preference was initially attempted with a printed spectrum and several paint series of measured spectral characteristics. It was clear that T.erytreae belongs to the "yellow-sensitive" group of Homoptera, but it was impossible to distinguish which pararneter(s) of colour the psyllids were responding to. Phototactic (walking) response to the individual parameters of colour was therefore measured using a monochromator. The phototactic action spectrum (against wavelength) was tri-modal, with peaks in the yellow-green (YG), blue (B), and ultra= violet (UV). Rate of phototaxis was not influenced by bandwidth (roughly equivalent to purity), but was proportional to intensity (roughly equivalent to reflectance). To investigate the influence of the above three wavelength regions on alightment, use was made of a very simple flight chamber incorporating a target of coloured light. Yellow-green and UV light both independently stimulated alightment . Their effect was additive. Different thresholds indicated distinct YG and UV receptor systems. Blue light alone did not stimulate alightment, and was strongly alightment-inhibitory in combination both with YG and with UV light. On the basis of the above physiological/behavioural findings, a new alightment formula was drawn up for describing the hamopteran's apparent manner of alightment determining integration of surface reflectance. The flush preference and alightment distributions on the series of artificial surfaces were found to correlate slightly more accurately, on average, as well as more consistently, with the new formula than with previously-available colour parameters. These findings are placed in perspective to the literature, and their possible economic relevance is discussed.
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- Date Issued: 1977
Conscientious objection and the concept of worship
- Authors: Moulder, James Edward
- Date: 1977
- Subjects: Conscientious objectors -- Law and legislation -- South Africa , Conscientious objectors -- South Africa , Conscientious objection , Conscientious objection -- Religious aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2749 , http://hdl.handle.net/10962/d1013555
- Description: [Preface] " ... the focus of this inquiry is limited to some of the connections between conscientious objection in South Africa and the worship and imitation of Christ. More specifically, at the most general level this essay is an attempt to explore six questions: What kind of conscientious objection does South African law allow? Why are some conscientious objectors only conscientious noncombatants? Why are some Christians conscientious noncombatants? Is it appropriate to worship Christ? Does Romans 13 undermine conscientious noncompliance? And is there a prescription for servile compliance? These are, however, not the only questions which are raised in this essay. Nor are they the only questions which can and need to be asked. But they are the questions which interest me. In addition, they have not received as much attention as they deserve".
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- Date Issued: 1977
The polysaccharides of Opuntia ficus-indica (L.) Mill. and Opuntia aurantiaca Lindl.
- Authors: McGarvie, Donald
- Date: 1977
- Subjects: Polysaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4438 , http://hdl.handle.net/10962/d1007597
- Description: The partially acetylated acidic mucilage isolated from the cactus Opuntia ficus-indica consists of a highly branched molecule containing D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 2.9:6.6:3.8:1.3 : 1.0. A partial hydrolysis study led to the isolation of fourteen oligosaccharides and a degraded polysaccharide. Periodate oxidation of the degraded polysaccharide and methylation analysis of the degraded and reduced degraded polysaccharides led to the proposal of a structure for the degraded polysaccharide consisting of a chain of alternating α-l,4-D-galactopyranosyluronic acid and β-1,2-Lrhamnopyranosyl units with branches consisting of short chains of β-1,6-D-galactopyranosyl units Iinked to C-3 of the rhamnose residues. An insight into the nature of the peripheral side-chains was obtained by methylation studies of the oligosaccharides and the native polysaccharide. The majority of the side-chains are terminated by D-xylopyranosyl and L-arabinofuranosyl units while there is a small proportion of D-galactopyranosyl end-groups. The remaining units of the peripheral chains consists of mainly 1,3- and 1,5-1 inked L-arabinofuranosyl units. The acidic polysaccharide isolated from the jointed cactus Opuntia aurantiaca contains D-galactose, L-arabinose, D-xylose, D-galacturonic acid and L-rhamnose in the ratio 5.9:5 .5:3.4: 1. 2:1.0 . A partial hydrolysis study revealed a similar series of galactose containing oligosaccharides as was identified from the mucilage of Opuntia ficus-indica. The degraded polysaccharide isolated from the partial hydrolysate was methylated and a possible structure proposed for the repeating unit. Methylation studies of the native polysaccharide indicated a polysaccharide with a more complex structure than that for the mucilage of Opuntia ficus-indica.
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- Date Issued: 1977
A study of the rabbit eye test system to determine the activity of acidic non-steroidal anti-inflammatory agents
- Authors: Wiseman, Ian Charles
- Date: 1977
- Subjects: Nonsteroidal anti-inflammatory agents , Anti-inflammatory agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3855 , http://hdl.handle.net/10962/d1013276
- Description: From introduction : "Inflammation per se, has been defined sufficiently to permit a rational approach to the search for drugs that modify this process, but satisfactory animal models for most rheumatoid diseases are not available". (Swingle 1974) In the search for new meaningful procedures for the detection and evaluation of anti-inflammatory drugs, the rabbit eye as a test system was studied.
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- Date Issued: 1977
The intensifying vision of evil: the Gothic novel (1764-1820) as a self-contained literary cycle
- Authors: Letellier, Robert Ignatius
- Date: 1977
- Subjects: Gothic revival (Literature) , English fiction -- 18th century -- History and criticism , English fiction -- 19th century -- History and criticism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2274 , http://hdl.handle.net/10962/d1006920 , Gothic revival (Literature) , English fiction -- 18th century -- History and criticism , English fiction -- 19th century -- History and criticism
- Description: The purpose of this study is to investigate the Gothic novel, a much neglected and misunderstood school, as a unified literary cycle. Attention has been centred on the domains or sub-systems of the novel where cultural models and generic traits are particularly important and distinguishable: character, plot (with the necessary evocation of a fictional world), theme and symbol. No apology is offered for the many quotations: far too little recourse is made to the texts in most discussions of the Gothic novel and this has all too frequently led to misapprehensions and unfounded generalizations. The opening section places the genre in a historio-literary context, and centres attention on the major novels, while the final section opens additional perspectives on the cycle, suggests the importance of the Gothic school for modern times, and illustrates the inevitability of its central vision of evil.
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- Date Issued: 1977
Examination of the theological education of Africans in the Presbyterian, Methodist, Congregational and Anglican churches in South Africa from 1860 to 1960
- Authors: Gqubule, T Simon N
- Date: 1977
- Subjects: Theological -- Study and teaching Theological seminaries -- South Africa Theology -- Study and teaching -- Protestant churches
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1254 , http://hdl.handle.net/10962/d1012082
- Description: This is in many ways a limited study. The first limitation is that only four denominations, the Anglican, Congregational, Methodist, Presbyterian, are considered and nothing is said about the work of the Moravians, Lutherans, Roman Catholics and the Dutch Reformed Churches in the field of theological education. The second limitation is that it is a study of theological education as distinct from general, industrial and other forms of education. All the forms of theological education considered here were run at missionary institutions that offered other forms of education and prepared their students for public government examinations with certain government conditions to be met. Moreover, a certain standard of general education was required before candidates were admitted to the theological course. Therefore, theological education was constantly dependent upon and was influenced by secular education and government regulations concerning secular education. For that reason the first chapter is a very brief survey of White Education in the Cape and African education in all four provinces from the beginning to 1915, the year before Fort Hare opened its doors to students seeking 'higher' education. The second chapter discusses the educational programme of Lovedale because Lovedale generally determined the whole of African education in the Cape. When Lovedale and the Methodists transferred their training to the South African Native College at Fort Hare, theological students had to abide by educational and other regulations of the university College. Chapters III and IV deal with the Methodist theological schools and the courses followed at Fort Hare. The third limitation of this study is that it is a study of the theological education of Africans, which category includes Coloureds and Indians because in the four churches under review they were trained together with Africans. In all churches under review here the theological education of whites was done in an unsatisfactory and ad hoc way. Many men were ordained without a satisfactory theological education. They were given some training by their superintendents, bishops or other men appointed to do the job in addition to their own normal duties. A few were sent overseas and many went through some arrangement within this country. St Paul's Theological College for Anglicans was opened in 1902. A start was made with the training of white Methodist Candidates for the ministry in the buildings of the Wesleyan High School for Girls in Grahamstown, in July 1928, under the Rev. James Pendlebury, B.A. (a supernumerary). Dr. William Flint who started the Methodist College as Principal, at Bollihope, Cape Town, in 1929, was seventy-five years of age when he opened the new Sbllege. From 1948 white theological students of the Methodist, Presbyterian and Congregational Churches have been trained at Livingstone House, Rhodes University, Grahamstown. .The final limitation is that this study ends at the close of 1960 and thus omits some of the exciting developments in theological education that have taken place since then. These limitations and demarcations were, however, necessary in order to focus attention on a small area where the main problems could be seen clearly, unencumbered by lesser issues. Where the training was run on denominational lines, it seemed necessary wherever possible to give a chapter to each denomination, and to attempt to pull the threads together in a concluding chapter.
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- Date Issued: 1977
Art and power : an investigation into the effect politics, the church and economics have had on the content of a work of art and the development of art in general
- Authors: Heydenrych, Albert B
- Date: 1977
- Subjects: Art and religion , Politics in art , Art and industry , Art and state
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2499 , http://hdl.handle.net/10962/d1013390
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- Date Issued: 1977
The early history of Blythswood Missionary Institution
- Authors: Rodger, Alastair
- Date: 1977
- Subjects: Blythswood Missionary Institution -- History
- Language: English
- Type: Thesis , Masters , BDiv
- Identifier: vital:1269 , http://hdl.handle.net/10962/d1013075
- Description: The Mfengu, or Fingos, of the Transkei were a mixed group of refugees. Originally driven from Natal during the Mfecane, they moved into the Transkei and then the Ciskei. In the 1860's some were allowed by the Cape government to settle in an area in the Western Transkei which it had recently seized. The majority of those who moved were opposed to mission work and education. When therefore the government agent for Fingoland, Captain Blyth, and a Free Church of Scotland missionary, Richard Ross, gained the support of a few headmen for an educational Institution in the Transkei, and approached Dr James Stewart of Lovedale to found such an Institution on the lines of Lovedale, they had very slender support. Mfengu subscribe £10.00 towards the cost. Stewart agreed on condition the support for this somewhat startling and, to some, unpalatable request was gained mainly because it was known that the government intended introducing a hut tax which would be far more onerous than the levy which, it was estimated, would be required to find the sum Stewart was asking. Blyth was able to use the agreement to a voluntary levy for an institution to persuade the government to postpone the tax. The Institution was built on a larger scale than had been planned, for the Mfengu made two subscriptions, each larger than the total requested, and Stewart raised money in Scotland.
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- Date Issued: 1977
Death and transcendence in northern European art
- Authors: Pratt, S R
- Date: 1977
- Subjects: Death in art , Art -- Europe, Northern
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2505 , http://hdl.handle.net/10962/d1015230
- Description: [From Introduction]. Time has revealed two distinct tendencies in the history of thought and art in Europe. That development in European culture which began in Ancient Greece is marked by a positive confidence in the relationship of man to his world. Parallel with but in opposition to this development is a separate progression in culture. The continuity of art in Northern Europe appears to be associated with the adherence of Northern man to a negative, fatalistic sense of being - to a spirit which is in conflict with a hostile violent environment. The purposo of this investigation is to determine, through art the nature of this sense of being in Northern Europe. No direct definition would be capable of conveying the fullest meaning of that spirit. lt is a feeling. To understand this morbid fatalism, it is therefore necessary to refer to the pre-Christian religion of the Germanic Barbarians - through which the Northern spirit manifested itself in the form of ragnarök. Ragnarök which can be translated as a moaning obscurity, shadows, twilight, fateful destiny, was a term used by Nordic bards in its broadest sense to describe the end of the world - the inevitable destruction of life.
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- Date Issued: 1977
The holy spirit in the theology of St. Luke
- Authors: Paterson, Torquil
- Date: 1977
- Subjects: Bible. Luke -- Criticism, interpretation, etc. , Holy Spirit -- Biblical teaching
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1265 , http://hdl.handle.net/10962/d1013007
- Description: The essay consists of five main chapters with an introduction and conclusion. This defines the limits of the essay and explains the methodology employed. These chapters are examined particularly with reference to the Spirit as the agent of fulfillment of the old, and the inaugurator of the new. 'The main text examined is Lk. 1.35. The Spirit is shown to be also used in a skillful linking and differentiation of John the Baptist and Jesus. Through a fairly detailed synoptic comparison, the peculiarly Lukan emphasis is brought to light. The Baptism is linked with 1.35 and the Transfiguration. Again both the Baptism and Temptation are shown to be seen in the light of the fulfillment of the Old Covenant. All the lines of fulfilment join together in the Spirit's descent on Jesus. The immediate result of this is the testing of his Messiahship, and Proclamation in the synagogue of Nazareth. This proclamation is coupled with the Luken rejection motif. The Spirit is seen to be especially involved in Jesus' ministries of exorcism and healing, but also in his preaching and teaching. The position of Lk 4.18-19 is seen to be of great importance. The main problem is the lack of specific reference to the Spirit. This is resolved in similar fashion to the question of the Messianic Secret. The relation of the apostles to the spirit is also discussed, since this is relevant to the ministry of the Church. Firstly the relation between the Transfiguration and Ascension is examined. This points to the fundamental centrality of the Ascension in Luke's theology. Pentecost is then seen as the fulfilling of the Ascension in the Church. Secondly, as a minor theme, the resurrection appearances are looked into and the similarities with Johannine thought are noted. This raises the question of the historicity of the Lukan schematization. In the examination of Pentecost itself the problem of the quotation from Joel and also the relation of Pentecost to the founding of the Church and the Gentile mission are raised. The Spirit is revealed to be active in two main areas : (1) the mission of the Church in evangelization - this is especialy seen in the areas of preaching, miracles and the life of the Church ; (2) the establishing and justification of the Gentile mission - this overriding concern is shown to obscure the other functions of the Spirit especially in the realm of Baptism and the Christian life of the individual. Thus Luke's historical sense is seen to be coupled with a theological desire to justify and bolster the Gentile mission. This draws out the various conclusions within the essay. The question of 'salvation-history' is raised and a solution found in terms of Luke's use of the Spirit. In broad outline the schema of Conzelmann is accepted. The Lukan eschatology is mentioned in an attempt to find a solution to questions raised by the comparison of Luke with Paul and John. This comparison is only meant to place the main conclusions of the essay within the context of the wider New Testament.
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- Date Issued: 1977
Some aspects of the theory, application, and computation of generalised inverses of matrices
- Authors: Cretchley, Partricia C
- Date: 1977
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/6212 , vital:21063
- Description: The idea of generalising the classical notion of the inverse of a non-singular matrix arose as far back as in 1920, but it was not until the late fifties that the development of the theory gained any impetus. Since then , as is the case in the development of many new concepts , work done in parallel in various parts of the world has resulted in a great deal of untidiness in the literature : confusion over terminology , and even duplication of theory. More recently, however, some attempts have been made to bring together people active in the field of generalised inverses, in order to reach consensus on some aspects of definition and terminology, and to publish more general works on the subject. Towards this purpose, a symposium on the theory and application of generalised inverses of matrices was held in Lubbock, Texas, and its proceedings published in 1968 (see [25] ). A few other works of this nature (see [4], (19a] ) have appeared , but the bulk of the literature still comprises numerous diverse papers offering further ideas on the theoretical properties which these matrices have , and drawing attention to their application in areas of statistics , numerical analysis , filtering , modern control and estimation theory, pattern recognition and many others. This essay offers a look at generalised inverses in the following way: firstly a broad basis and background is established in the first three chapters to provide greater understanding of the motivation for the remaining chapters, where the approach then changes to become far more detailed. Within this general framework, Chapter 1 offers a brief glimpse of the history and development of work in the field. In Chapter 2 some of the most significant properties of these inverses are described, while in Chapters 3 and 4 and 5 attention is given to interesting and remarkable computational algorithms relating to generalised inverses (some well suited to machine processing). The material of Chapters 4 and 5 is largely due to Decell, Stallings and Boullion, and Tanabe, in [6], [24] and [27], respectively, while the source of material for the first three chapters is the literature generally, with Penrose's two papers providing a rough framework for Chapters 1 and 2 (see [17]).
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- Date Issued: 1977
Categories of experience amongst the Xhosa : a psychological study
- Authors: Schweitzer, Robert David
- Date: 1977
- Subjects: Xhosa (African people) -- Psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3237 , http://hdl.handle.net/10962/d1013172
- Description: Transcultural studies of psychological states may be seen as falling within two schools, one adopting a position in which universal criteria of "mental health" are assumed, the other a cultural relativist position in which phenomena are understood in terms of the context in which they occur. The present study, in adopting the latter position, examines categories of experience amongst the Xhosa in terms of their meaning within Xhosa cosmology. The thoughts and practices of a Xhosa Iqgira (diviner) were extensively examined using an idiographic approach. This was corroborated by in-depth interviews with his consultees who were undergoing the categories being studied. Three categories, thwasa, phambana and amafufunyana are explicated. Thwasa is seen to be related to the individual- shade communion. Phambana is predominantly related to custom and witchcraft. Amafufunyana is related to disharmonious interpersonal situations within the community. The universalist position, derived from descriptive psychiatry, has often viewed the mental status of amaqgira {diviners) as neurotic or even psychotic. This finding is not supported in the present study. The implications of the research for community mental health in Southern Africa are discussed.
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- Date Issued: 1977
An investigation of the relationship between acculturation, n achievement and n affiliation in Owambo
- Authors: Steyn, Daniël Marthinus
- Date: 1977
- Subjects: Ovambo (African people) , Acculturation -- Namibia , Achievement motivation , Affiliation (Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3241 , http://hdl.handle.net/10962/d1013295
- Description: The contents of this thesis were mainly determined by the traditional methodological requirements for a thesis of this nature. However a need was felt to include a somewhat expanded survey of the interrelationship between anthropology and psychology. This "need" developed during a review of the above-mentioned interrelationship especially when we found that the historical interaction between these two disciplines had never been followed from the earliest times to the present. Furthermore, although different writers have treated different aspects of this interaction, not one could be found that had treated all the different angles of the relationship. Thus although it is a well known fact that there is a prominent relationship between these two disciplines this was found to be quite inadequately documented. Furthermore, it is usually discussed from either a psychological or an anthropological viewpoint. The hazy view of the interrelationship between these two disciplines is naturally a frustrating situation for any researcher in this field - especially one who would prefer to have a view of the position of his research within the wider panorama of research surrounding it. Intro., p. 1.
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- Date Issued: 1977
Feeding ecology of the cichlid fish Sarotherodon Mossambicus in Lake Sibaya, KwaZulu
- Authors: Bowen, Stephen H
- Date: 1977
- Subjects: Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5837 , http://hdl.handle.net/10962/d1009688 , Cichlids -- Ecology , Fishes -- Ecology -- South Africa -- KwaZulu-Natal -- Sibaya, Lake
- Description: The feeding of the cichlid fish Sarotherodon mossambicus in Lake Sibaya, KwaZulu, was studied in relation to various biotic and abiotic features of the l ake environment from January, 1973 to July, 1975. The primary goal of the study was to determine the cause of stunting and poor condition of adults in this population. Juvenile and adult S. mossambicus feed on a mixture of detritus, bacteria and diatoms that occurs as a flocculent layer on sand substrates throughout the lake. Concentrated gastric acid, commonly at pH values of 1.5 and lower, lyses diatoms and bacteria which are subsequently digested in the intestine. This is the first report of digestion of bacteria by a fish, and the nutritional significance of the finding is discussed. Juveniles feed predominantly on shallow sand terraces found along the margin of much of the lake, while adults usually feed in offshore waters at depths of 3 m and greater. Benthic floc from feeding areas of juveniles and adults have similar concentrations of organic matter, total carbohydrate, soluble carbohydrate and calories, but differ markedly in respect to diatom and protein concentration. Diatom concentrations are generally high in terrace floc but are consistently low in floc from deep water. Protein concentration of benthic floc decreases with increasing depth from 0 - 5 m. Partial correlation analysis shows that protein and diatom concentrations have no correlation independent. of their common relationship to depth, and the evidence implicates detrital bacteria as the primary source of protein in benthic floc. Probable causes of the observed distributions of diatoms and protein are discussed. The protein content of benthic floc profoundly influences its nutritional value. A comparison with available data on animal nutrition shows that the ratio of digestible protein to digestible energy in floc in the shallows is high enough that this food resource would be expected to support good growth, but the ratio for deep water floc is so low that it would be expected to result in conspicuous malnutrition. Thus, inadequate dietary protein is identified as the principal cause of stunting and poor condition of adult S· mossambicus in Lake Sibaya; It is argued that the ratio of digestible protein to digestible calories can be expected to determine the food value of particulate organic matter that includes amorphous detritus in other ecosystems. Despite stunting and poor condition of adults, S. mossambicus are abundant in Lake Sibaya. The precocious breeding of this population is discussed as an adaptation that allows it to maximize reproductive output given the limited resources available to adults. Juvenile S. mossambicus perform daily movements from deep water onto the terraces where they feed and then back into deep water. During periods of relatively low lake level when terrace waters were usually less than 1.5 m deep (1-73 to 1-74), juveniles were present on the terrace throughout daylight hours. At relatively high lake levels (7-74 to 8-75), juveniles were present on the terraces for only about five hours following sunset. Periods of heavy wave action interrupt feeding activity and result in reduced numbers of fish in terrace waters. The possible roles of predator avoidance and temperature in determination of daily feeding behavior are discussed. Daily energy assimilation by juveniles, estimated by a field technique, is approximately 115 cal per g fish dry weight.
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- Date Issued: 1977
La femme dans l'oeuvre litteraire de Jean-Paul Sartre
- Authors: Seiler, Miriam Zimet
- Date: 1977
- Subjects: Sartre, Jean-Paul, 1905-1980 -- Criticism and interpretation
- Language: French
- Type: Thesis , Masters , MA
- Identifier: vital:3641 , http://hdl.handle.net/10962/d1014302
- Description: [From introduction]. Pourquoi examiner Ie rôle de la femme dans l' oeuvre de Sartre? Jean-Paul Sartre est l'un des philosophes les plus importants de ce siècle, un philosophe qui s'est consacré ấ un examen de l'homme et de ses rapports avec l'existence par la liberté conscienter; un penseur qui a montré son individualisme dans le domaine de la politique, n'acceptant que ce qu'il trouve défendable; un romancier et un dramaturge dont l'oeuvre a connu un succès mondial.
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- Date Issued: 1977
The performance of a 22 GHz radio telescope
- Authors: Gaylard, Michael John
- Date: 1977
- Subjects: Radio telescopes , Paraboloid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5520 , http://hdl.handle.net/10962/d1011946 , Radio telescopes , Paraboloid
- Description: The performance of the Rhodes 22 GHz radio telescope and its improvement are discussed in this thesis. The reflector surfaces of the Cassegrain antenna were surveyed and the surface errors minimised, while the magnitude of thermal and gravitational defomations was calculated. The design and operation of the microwave front end has been improved, and the mixer performance characterised. The continuum and spectral line receivers and their sensitivity are described. The aperture efficiency, which has been raised from 0,47 to 0,57, was deduced from solar and lunar observations and atmospheric attenuation measurements. The antenna beam pattern was also obtained from the observations, with the aid of a computer program, and is compared to that predicted for the telescope.
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- Date Issued: 1977
Pitch learning and the implications for music education
- Authors: Byrd, Audrey S
- Date: 1977
- Subjects: Musical pitch -- Instruction and study
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2627 , http://hdl.handle.net/10962/d1001867
- Description: A study of pitch learning must outline first the procedures involved in such learning and then identify specific factors appearing to influence the learning of pitch. Once identified, each factor can then be evaluated by controlled experiment before confirming its influence. Since it is what is heard and perceived that is learnt, I have started with the process of Hearing and Perceiving, for as Arnold Abramovitz, Senior Lecturer in Psychology at Cape Town says, “the reception, processing and interpretation of acoustic symbols constitutes some of the most elusive and complex phenomena to attempt to examine, gauge and measure, due partly to the transient, ephemeral nature of sound itself.”
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- Date Issued: 1977
The biology of Clarias Gariepinus (Burchell, 1822) in Lake Sibaya, Kwazulu, with emphasis on its role as a predator
- Authors: Bruton, Michael N
- Date: 1977
- Subjects: Catfishes -- South Africa -- KwaZulu-Natal -- Lake Sibaya. , Clarias , Clariidae
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:5886 , http://hdl.handle.net/10962/d1013313
- Description: Aspects of the biology of the sharptooth catfish, Clarias gariepinus (Burchell, 1822) were studied in a clear coastal lake (Lake Sibaya, KwaZulu.). Catfish reach maturity towards the end of the first year (total length 200-250mm) and breed in summer. Gonadal maturation is cyclical, and most fishes are ripe between September. and January e ach year. Maturation stages and fecundity are described. Twenty-two catfish spawning runs were witnessed. There were no large aggregations of catfish before the Summer rains, as reported in some impoundments and rivers, but catfish accumulated on the shallow terrace immediately before a spawning run. Spawning usually took place in flooded marginal areas after heavy rain on dark calm nights. Peak activity occurred between 20h00 and 02h30. Pre-nuptial aggression, courtship and mating are described and illustrated in detail for the first time from field observations. Gonadal products are released while in amplexus and fertilized externally. The eggs have an adhesive disc for attachment to plants, and develop rapidly. Early development and feeding are described. The growth rate of catfish was determined using rings on the pectoral spines, and validated using recent techniques. C.gariepinus in Lake Sibaya grow rapidly and remain in good condition to a length of 500mm, but larger catfish have a poor growth rate and condition, and few exceed 650mm. The modal length and weight of the Sibaya population is intermediate between that of other populations but the number and condition of larger catfish in Lake Sibaya is lower. Other studies on C.gariepinus growth are reviewed. Very high and low first year increments obtained previously may be due to methodological errors, but catfish do appear to have variable growth rates. The size reached by C.gariepinus is reviewed. Catfish are equipped morphologically and behaviourally to feed on a wide variety of·prey in different situations, but they usually feed at night on exposed, active benthic organisms. Social hunting facilitates the capture of prey which is too fast or manoevrable for a single predator. Food preferences are scored by three different methods and presented for the total catfish population and for different length groups, seasons, and habitats. Juveniles feed more often and on a greater variety of prey, and their condition is better than that of adults. The proportions of several food items in the diet changed at different lake levels as marginal areas became inundated. In particular, increasing lake levels resulted in a change in relative density of three cichlid prey in the shallow water feeding area of catfish. This situation provided the opportunity to study the effect of changing cichlid density on predation by catfish. The world literature on factors influencing the predator-prey relationship in fish is reviewed and several key factors are identified. The interaction of fish predators and prey in Africa, and particularly Lake Sibaya, is examined in detail, and prey density, modified by accessibility, is found to be an important factor. The effect of cichlid prey density on catfish predation was therefore investigated using field collections and experimental observations. Catfish prey on the cichlid species with greatest relative abundance, with some deviations which can be explained in terms of accessibility. The experimental results also describe feeding periodicity, imitative hunting and the effect of water depth , day-night light intensity changes and predator number on predation efficiency on cichlids. Catfish predation is discussed in terms of recent predation theory, and it is concluded that their ability to switch from one prey to another as prey availability (= density+ accessibility) changes , is an an important aspect of their success as predators. Catfish predate more efficiently on invertebrates, but feed largely on fishes after the first year. This preference for fish prey is probably related to food quality, as fishes contributed over 75% of the energy content of all ingested food, as well as abundant protein and the correct amino acid balance. Finally, I conclude that the role of C.gariepinus as a predator on S.mossambicus is three-fold: (a) to enhance species' fitness by removing enfeebled individuals i.e. to act as a 'cleanser' (b) to restrict the distribution of prey under certain conditions i.e. act as a 'restricter' (c) to dampen fluctuations in cichlid abundance i.e. act as a 'regulator'. The relative importance of these roles may alter at different lake levels in Lake Sibaya in response to changes in the vulnerability of fish prey.
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- Date Issued: 1977
Sensory dominance : an experiment across cultures
- Authors: Locke, Hester W
- Date: 1977
- Subjects: Perception -- Testing , Senses and sensation -- Testing , Dominance (Psychology)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3214 , http://hdl.handle.net/10962/d1012744
- Description: Physical and intellectual differences in the home environment of Xhosa and White children suggested that the interaction of touch and vision in situations of sensory conflict and the development of dominance may be different in children from these homes. Children aged 5-13 years were tested on apparatus which created a conflict of tactual and visual judgement about the perceived size of the stimulus. Xhosa and White subjects performed similarly except when only tactual judgement was allowed and the Xhosa group were less influenced by touch. The study concludes that for children touch and vision contribute equally to the resolution of sensory conflict when both senses are active in size-judgements and when only one mode is allowed for judging then the resolution is biased towards this mode. This outcome is different from that of experiments with adults and has implications for theories derived from them.
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- Date Issued: 1977
Pitch learning and the implications for music education
- Authors: Byrd, Audrey S
- Date: 1977
- Subjects: Musical pitch -- Instruction and study
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2675 , http://hdl.handle.net/10962/d1007403
- Description: From introduction: A study of pitch learning must outlina first the procedures involved in such learning ar~d then identify specific factors appearing to influence the learning of pitch. Once identified, each factor can then be evaluated by controlled experiment before confirming its influence. Since it is \'lhat is heard and perceived that is learnt, I have started with the process of Hearing and Perceiving, for as Arnold Abramovitz, Senior Lecturer in Psychology at Cape Town says, "the reception, processing and interpretation of acoustic symbols constitutes some of the most elusive and complex phenomena to attempt to examine, gauge and measure, due partly to the transient, ephemeral nature of sound itself."
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- Date Issued: 1977