A preliminary report on the age and significance of Quaternary lacustrine deposits at Birnam, north-east Cape Province, South Africa
- Hanvey, Patricia M, Lewis, Colin A
- Authors: Hanvey, Patricia M , Lewis, Colin A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6686 , http://hdl.handle.net/10962/d1006688
- Description: The paper presents the results of preliminary investigations at Birnam, in the Rhodes area of the eastern Cape Drakensberg, which may have important implications for palaeoenvironmental reconstructions in Southern Africa. A study has been undertaken on a sedimentary sequence exposed by fluvial incision on the outer bend of the River Bokspruit, at an altitude of 1850 m.
- Full Text: false
- Date Issued: 1990
- Authors: Hanvey, Patricia M , Lewis, Colin A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6686 , http://hdl.handle.net/10962/d1006688
- Description: The paper presents the results of preliminary investigations at Birnam, in the Rhodes area of the eastern Cape Drakensberg, which may have important implications for palaeoenvironmental reconstructions in Southern Africa. A study has been undertaken on a sedimentary sequence exposed by fluvial incision on the outer bend of the River Bokspruit, at an altitude of 1850 m.
- Full Text: false
- Date Issued: 1990
An analysis of the early ontogeny of Aplocheilichthys johnstoni (Günter, 1893) from a life history perspective
- Authors: Haigh, Eliria H
- Date: 1990
- Subjects: Ontogeny -- History , Cyprinodontidae , Aplocheilidae , Fishes -- History
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5217 , http://hdl.handle.net/10962/d1005060
- Description: The reproductive and developmental styles of Aplocheilichthys johnstoni closely resemble those of other oviparous cyprinodont fishes reported in the literature. Reproductively it sorts to the guild of nonguarding phytophyllic broodhiders, is a daily, fractional spawner of relatively large, adhesive eggs. The length of the embryonic period varies between 14 and 19 days and the larval period can last for up to 30 days. Sexual maturity can be attained at an age of 150 days from fertilization. The embryology is described in detail and close comparison is made with the embryology of other cyprinodonts to highlight possible phylogenetic differences. Major differences with other cyprinodonts are in the rate of development, and heterochronic shifts in the appearance of certain structures in relation to each other. A discussion is included on the nature of development. It is suggested that development proceeds in a gradual stepwise fashion, interspersed with four major saltations, namely, fertilisation, onset of exogenous feeding, sexual maturity and death
- Full Text:
- Date Issued: 1990
- Authors: Haigh, Eliria H
- Date: 1990
- Subjects: Ontogeny -- History , Cyprinodontidae , Aplocheilidae , Fishes -- History
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5217 , http://hdl.handle.net/10962/d1005060
- Description: The reproductive and developmental styles of Aplocheilichthys johnstoni closely resemble those of other oviparous cyprinodont fishes reported in the literature. Reproductively it sorts to the guild of nonguarding phytophyllic broodhiders, is a daily, fractional spawner of relatively large, adhesive eggs. The length of the embryonic period varies between 14 and 19 days and the larval period can last for up to 30 days. Sexual maturity can be attained at an age of 150 days from fertilization. The embryology is described in detail and close comparison is made with the embryology of other cyprinodonts to highlight possible phylogenetic differences. Major differences with other cyprinodonts are in the rate of development, and heterochronic shifts in the appearance of certain structures in relation to each other. A discussion is included on the nature of development. It is suggested that development proceeds in a gradual stepwise fashion, interspersed with four major saltations, namely, fertilisation, onset of exogenous feeding, sexual maturity and death
- Full Text:
- Date Issued: 1990
The future of the past in South African schools : curriculum development, school leaving examinations and syllabus design and assessment in history : a comparative study
- Authors: Gunn, Alan Howard
- Date: 1990
- Subjects: Education -- South Africa , Education -- South Africa -- History , Education -- South Africa -- Forecasting
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1375 , http://hdl.handle.net/10962/d1001441
- Description: This is a two-part study dealing with the curriculum, school leaving examinations and History as a school subject in England and South Africa. Part One is a developmental study. Developments in the curriculum of both countries since the Second World War are traced. In England this period is characterised by a shift from a somewhat laissez faire approach of the authorities at Whitehall to the curriculum of individual schools to the prescription that seems inherent in the National Curriculum. The outstanding development in South Africa during this period has been the introduction of a system of differentiated education. In contrast to minor developments in the South African school leaving examination system, England has witnessed the consolidation of the two-tier GCE and CSE system into a single examination at 16+, the GCSE. In discussing developments in History as a school subject, one is struck by the growth of the "new history" in England (this is described in some detail) against the relative lack of development (at "official" syllabus level) in South Africa where the subject remains rooted in the "traditional", chronological, content-based approach. Part Two of this study compares the current situation in England and South Africa at both the macro (ie. curriculum and school leaving examination systems) and micro (ie. History as a subject in the curriculum) levels. At the macro level the curriculum and school leaving examination systems in both England and South Africa are contrasted and one notes an increasing trend towards centralization in both countries. At the micro level use is made of "official" syllabuses and examination papers to contrast the "new history" approach in England with the "traditional" approach in South Africa. In the conclusion two broad possibilities for curriculum reform in South Africa are considered: Broad reform across the curriculum on the one hand and reforms in History on the other
- Full Text:
- Date Issued: 1990
- Authors: Gunn, Alan Howard
- Date: 1990
- Subjects: Education -- South Africa , Education -- South Africa -- History , Education -- South Africa -- Forecasting
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1375 , http://hdl.handle.net/10962/d1001441
- Description: This is a two-part study dealing with the curriculum, school leaving examinations and History as a school subject in England and South Africa. Part One is a developmental study. Developments in the curriculum of both countries since the Second World War are traced. In England this period is characterised by a shift from a somewhat laissez faire approach of the authorities at Whitehall to the curriculum of individual schools to the prescription that seems inherent in the National Curriculum. The outstanding development in South Africa during this period has been the introduction of a system of differentiated education. In contrast to minor developments in the South African school leaving examination system, England has witnessed the consolidation of the two-tier GCE and CSE system into a single examination at 16+, the GCSE. In discussing developments in History as a school subject, one is struck by the growth of the "new history" in England (this is described in some detail) against the relative lack of development (at "official" syllabus level) in South Africa where the subject remains rooted in the "traditional", chronological, content-based approach. Part Two of this study compares the current situation in England and South Africa at both the macro (ie. curriculum and school leaving examination systems) and micro (ie. History as a subject in the curriculum) levels. At the macro level the curriculum and school leaving examination systems in both England and South Africa are contrasted and one notes an increasing trend towards centralization in both countries. At the micro level use is made of "official" syllabuses and examination papers to contrast the "new history" approach in England with the "traditional" approach in South Africa. In the conclusion two broad possibilities for curriculum reform in South Africa are considered: Broad reform across the curriculum on the one hand and reforms in History on the other
- Full Text:
- Date Issued: 1990
The pursuit of poetry : a defence
- Authors: Gouws, John
- Date: 1990
- Subjects: Poetry
- Language: English
- Type: Text
- Identifier: vital:632 , http://hdl.handle.net/10962/d1020701
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1990
- Authors: Gouws, John
- Date: 1990
- Subjects: Poetry
- Language: English
- Type: Text
- Identifier: vital:632 , http://hdl.handle.net/10962/d1020701
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1990
Radio studies of ionized hydrogen in the southern Milky Way
- Authors: Gaylard, Michael John
- Date: 1990
- Subjects: Interstellar hydrogen Milky Way Astrophysics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5440 , http://hdl.handle.net/10962/d1001993
- Description: This thesis describes the results of a survey of the HI42ɑ recombination line emission at 2.3 GHz from HII regions in the Southern Milky Way, carried out with the 26 m diameter Hartebeesthoek radio telescope. The Galactic Longitude range covered was 290° to 40°. Single recombination lines were detected from 375 positions. Multiple lines were observed towards 90 positions in the inner Galaxy. No line emission could be detected in 28 positions. Continuum antenna temperatures were estimated from drift scans or radio maps observed for the purpose. LTE electron temperatures and turbulent velocities of the HII regions were calculated where possible. The properties of the sample were compared to those observed in HI09ɑ surveys. The lines observed from over 50 positions were first detections, of which half were associated with optically-identified HII regions. In about 150 cases the lines were only the second to be detected from those HII regions. The processes of the radio emission, detection, and analysis were simulated numerically. The detectability of the emission and the magnitude of non-LTE effects and pressure-broadening in multi-component HII regions was predicted and compared to observations. The radio luminosity function of the HII regions was determined over a range of three orders of magnitude in intrinsic brightness for the first time, using techniques which corrected for different types of incompleteness in the samples. The luminosity function was compared to those in five selected spiral galaxies, and shown to lie between those of M33 and M81. An alternate form of the luminosity function was developed for use with a numerical model of the spiral arm structure of the Milky Way. The physical parameters defining the major spiral arms were established by comparing synthesized diagrams of radial velocity versus Galactic Longitude with those actually observed. The faint, extended HII regions S9 and RCW129 in Scorpius, the Barnard Loop in Orion, and S296 in Canis Major were analyzed, using all available data. All the recombination lines from these HII regions were first detections
- Full Text:
- Date Issued: 1990
- Authors: Gaylard, Michael John
- Date: 1990
- Subjects: Interstellar hydrogen Milky Way Astrophysics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5440 , http://hdl.handle.net/10962/d1001993
- Description: This thesis describes the results of a survey of the HI42ɑ recombination line emission at 2.3 GHz from HII regions in the Southern Milky Way, carried out with the 26 m diameter Hartebeesthoek radio telescope. The Galactic Longitude range covered was 290° to 40°. Single recombination lines were detected from 375 positions. Multiple lines were observed towards 90 positions in the inner Galaxy. No line emission could be detected in 28 positions. Continuum antenna temperatures were estimated from drift scans or radio maps observed for the purpose. LTE electron temperatures and turbulent velocities of the HII regions were calculated where possible. The properties of the sample were compared to those observed in HI09ɑ surveys. The lines observed from over 50 positions were first detections, of which half were associated with optically-identified HII regions. In about 150 cases the lines were only the second to be detected from those HII regions. The processes of the radio emission, detection, and analysis were simulated numerically. The detectability of the emission and the magnitude of non-LTE effects and pressure-broadening in multi-component HII regions was predicted and compared to observations. The radio luminosity function of the HII regions was determined over a range of three orders of magnitude in intrinsic brightness for the first time, using techniques which corrected for different types of incompleteness in the samples. The luminosity function was compared to those in five selected spiral galaxies, and shown to lie between those of M33 and M81. An alternate form of the luminosity function was developed for use with a numerical model of the spiral arm structure of the Milky Way. The physical parameters defining the major spiral arms were established by comparing synthesized diagrams of radial velocity versus Galactic Longitude with those actually observed. The faint, extended HII regions S9 and RCW129 in Scorpius, the Barnard Loop in Orion, and S296 in Canis Major were analyzed, using all available data. All the recombination lines from these HII regions were first detections
- Full Text:
- Date Issued: 1990
A study of the reading interests and reading habits of English (first language) secondary-school pupils in South Africa: with particular reference to the Province of Natal
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
Essential fatty acids and ascorbic acid- interactions and effects on melanoma growth
- Authors: Gardiner, Neil Stockenstrom
- Date: 1990
- Subjects: Fatty acids , Melanoma , Mice -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4549 , http://hdl.handle.net/10962/d1018230
- Description: The present study was carried out to determine the effects and possible mechanisms of action of the essential fatty acids (EFAs) (linoleic acid (LA), gamma-linolenic acid (GLA) and arachidonic acid (AA)) and ascorbic acid (Asc) on BL6 murine melanoma growth in cell culture and in mice. Interactions between the nutrients in influencing melanoma growth as well as possible mechanisms of the interactions were also examined in the above systems. Cell culture studies revealed that all three EFAs (0-SOμg/ml) and Asc (0-200μg/ml) significantly inhibited melanoma growth at the concentrations used. The EF As were also found to significantly inhibit growth, although to a lesser extent than BL6 cells, of monkey kidney (LLCMK) cells which were used as a non-malignant control cell line. Asc in contrast was found not to inhibit growth of these cells. Supplementation of Asc (lOO)μg/ml) to EFA containing (0-50μg/ml) medium was found to significantly increase inhibition of cell growth in both cell lines, and in the BL6 cells in particular, after taking into account the growth inhibitory effects of Asc in the absence of EFAs. The mechanism of cell growth inhibition by the EF As appeared to involve lipid peroxidation but not enhanced prostaglandin (PG) or leukotriene (LT) synthesis. While Asc was found to increase both lipid peroxidation and PG synthesis in the cells, these mechanisms and enhanced LT synthesis did not appear to have played a role in the inhibition of cell growth by Asc or in the growth inhibitory interaction between Asc and the EF As. In vivo studies revealed that diets containing essential or polyunsaturated fatty acids (EFAs/PUFAs) in the form of vegetable oils, and in particular GLA in the form of evening primrose oil, significantly promoted melanoma growth in mice when compared with an EFA/PUFA free diet containing predominantly saturated fats (SF). Supplementary dietary Asc in contrast was found to significantly inhibit melanoma growth in mice fed EFA/PUFA, and in particular GLA, containing diets but not in mice fed SF cont~g diets. This result appears to indicate the occurrence of an interaction between the two nutrients. Ul The mechanism of tumour promotion by the EP As/PUP As did not appear to have involved enhanced PG or LT synthesis or lipid peroxidation. Since dietary EPA/PUPA manipulation was found to significantly alter the EPA content of tissues, including the melanomas, the mechanism of tumour promotion may have involved changes in the EPA composition of the tumour cells. While supplementary Asc was found to significantly increase the Asc content of certain tissues, including the melanomas, which may have played a role in tumour growth inhibition by Asc, it was found not to affect the EPA content of tissues. Enhanced PG or LT synthesis and lipid perox:idation did not appear to have been involved in the tumour growth inhibitory interaction between Asc and the EP As/PUP As. THe activity of the enzyme delta-6-desaturase, a key enzyme in EF A metabolism which catalyses the desaturation of LA to GLA, and the influence of Asc on activity of the enzyme were also examined. The cultured cells, and BL6 cells in particular, were found to contain significant activity of the enzyme. Whereas murine liver microsomal fractions were found to contain delta-6-desaturase activity, microsomes from melanomas grown in mice were found to lack activity of the enzyme. The significant tumour promoting effects of the GLA containing EPO diet may have been the result of the lack of delta-6-desaturase activity in tumour cells grown in mice. Asc was found to stimulate activity of the enzyme in cultured BL6 cells but not in LLCM.K cells, while dietary Asc and EF A/PUP A manipulation did not influence activity of the enzyme in microsomal fractions. This study has confirmed previous reports of the in vivo tumour promoting effects of dietary EP As/PUP As and the tumour growth inhibitory effects of Asc. The in vitro cell growth inhibitory effects of Asc and the EP As also confirm the results of previous reports. Previous studies investigating possible interactions between Asc and EP As/PUP As in influencing tumour cell growth could not be located in the relevant literature. This study may therefore be one of the first investigations of any such interaction between these nutrients in tumour cells. While this study was not able to identify the mechanisms involved in the different tumour promoting or tumour growth inhibitory effects of the two nutrients in the two systems, it did eliminate a number of potential mechanisms. The results of this study also emphasise the difficulty of attempting to compare the results of in vitro and in vivo studies.
- Full Text:
- Date Issued: 1990
- Authors: Gardiner, Neil Stockenstrom
- Date: 1990
- Subjects: Fatty acids , Melanoma , Mice -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4549 , http://hdl.handle.net/10962/d1018230
- Description: The present study was carried out to determine the effects and possible mechanisms of action of the essential fatty acids (EFAs) (linoleic acid (LA), gamma-linolenic acid (GLA) and arachidonic acid (AA)) and ascorbic acid (Asc) on BL6 murine melanoma growth in cell culture and in mice. Interactions between the nutrients in influencing melanoma growth as well as possible mechanisms of the interactions were also examined in the above systems. Cell culture studies revealed that all three EFAs (0-SOμg/ml) and Asc (0-200μg/ml) significantly inhibited melanoma growth at the concentrations used. The EF As were also found to significantly inhibit growth, although to a lesser extent than BL6 cells, of monkey kidney (LLCMK) cells which were used as a non-malignant control cell line. Asc in contrast was found not to inhibit growth of these cells. Supplementation of Asc (lOO)μg/ml) to EFA containing (0-50μg/ml) medium was found to significantly increase inhibition of cell growth in both cell lines, and in the BL6 cells in particular, after taking into account the growth inhibitory effects of Asc in the absence of EFAs. The mechanism of cell growth inhibition by the EF As appeared to involve lipid peroxidation but not enhanced prostaglandin (PG) or leukotriene (LT) synthesis. While Asc was found to increase both lipid peroxidation and PG synthesis in the cells, these mechanisms and enhanced LT synthesis did not appear to have played a role in the inhibition of cell growth by Asc or in the growth inhibitory interaction between Asc and the EF As. In vivo studies revealed that diets containing essential or polyunsaturated fatty acids (EFAs/PUFAs) in the form of vegetable oils, and in particular GLA in the form of evening primrose oil, significantly promoted melanoma growth in mice when compared with an EFA/PUFA free diet containing predominantly saturated fats (SF). Supplementary dietary Asc in contrast was found to significantly inhibit melanoma growth in mice fed EFA/PUFA, and in particular GLA, containing diets but not in mice fed SF cont~g diets. This result appears to indicate the occurrence of an interaction between the two nutrients. Ul The mechanism of tumour promotion by the EP As/PUP As did not appear to have involved enhanced PG or LT synthesis or lipid peroxidation. Since dietary EPA/PUPA manipulation was found to significantly alter the EPA content of tissues, including the melanomas, the mechanism of tumour promotion may have involved changes in the EPA composition of the tumour cells. While supplementary Asc was found to significantly increase the Asc content of certain tissues, including the melanomas, which may have played a role in tumour growth inhibition by Asc, it was found not to affect the EPA content of tissues. Enhanced PG or LT synthesis and lipid perox:idation did not appear to have been involved in the tumour growth inhibitory interaction between Asc and the EP As/PUP As. THe activity of the enzyme delta-6-desaturase, a key enzyme in EF A metabolism which catalyses the desaturation of LA to GLA, and the influence of Asc on activity of the enzyme were also examined. The cultured cells, and BL6 cells in particular, were found to contain significant activity of the enzyme. Whereas murine liver microsomal fractions were found to contain delta-6-desaturase activity, microsomes from melanomas grown in mice were found to lack activity of the enzyme. The significant tumour promoting effects of the GLA containing EPO diet may have been the result of the lack of delta-6-desaturase activity in tumour cells grown in mice. Asc was found to stimulate activity of the enzyme in cultured BL6 cells but not in LLCM.K cells, while dietary Asc and EF A/PUP A manipulation did not influence activity of the enzyme in microsomal fractions. This study has confirmed previous reports of the in vivo tumour promoting effects of dietary EP As/PUP As and the tumour growth inhibitory effects of Asc. The in vitro cell growth inhibitory effects of Asc and the EP As also confirm the results of previous reports. Previous studies investigating possible interactions between Asc and EP As/PUP As in influencing tumour cell growth could not be located in the relevant literature. This study may therefore be one of the first investigations of any such interaction between these nutrients in tumour cells. While this study was not able to identify the mechanisms involved in the different tumour promoting or tumour growth inhibitory effects of the two nutrients in the two systems, it did eliminate a number of potential mechanisms. The results of this study also emphasise the difficulty of attempting to compare the results of in vitro and in vivo studies.
- Full Text:
- Date Issued: 1990
The enlightenment and modern French studies
- Fein, Patrick L-M. (Patrick Louis-Marie), 1938-
- Authors: Fein, Patrick L-M. (Patrick Louis-Marie), 1938-
- Date: 1990
- Subjects: French literature -- 18th century -- History and criticism , Enlightenment
- Language: English
- Type: Text
- Identifier: vital:623 , http://hdl.handle.net/10962/d1020692 , ISBN 0868102083
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1990
- Authors: Fein, Patrick L-M. (Patrick Louis-Marie), 1938-
- Date: 1990
- Subjects: French literature -- 18th century -- History and criticism , Enlightenment
- Language: English
- Type: Text
- Identifier: vital:623 , http://hdl.handle.net/10962/d1020692 , ISBN 0868102083
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1990
Tribute to the late Davadoss
- EIMWU
- Authors: EIMWU
- Date: 1990
- Subjects: Engineering Industrial and Mining Workers Union (EIMWU)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/162344 , vital:40921
- Description: To my knowledge the author of this adage was Brother Davadoss. Better known to many, far and wide, as “DAVVY”. Lesley Davadoss was one of nine children of a working class family. Grew up and spent his formative years in Bokmakierie, Athlone. Devout in his Catholic upbringing, later to be ordained as a Deacon at St. Mary of the Angels. Lesley was a very sincere person who concerned himself with the needs of the Community, which naturally resulted in his involvement at the Company where he worked with the problems of his workmates. Along with other like thinking persons, he formed the E.I.W.U. in the Cape, holding meetings at his home in Kayter Road Crawford. The Branch in Durban, along with the Cape Town Branch formed E.I.W.U.S.A.
- Full Text:
- Date Issued: 1990
- Authors: EIMWU
- Date: 1990
- Subjects: Engineering Industrial and Mining Workers Union (EIMWU)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/162344 , vital:40921
- Description: To my knowledge the author of this adage was Brother Davadoss. Better known to many, far and wide, as “DAVVY”. Lesley Davadoss was one of nine children of a working class family. Grew up and spent his formative years in Bokmakierie, Athlone. Devout in his Catholic upbringing, later to be ordained as a Deacon at St. Mary of the Angels. Lesley was a very sincere person who concerned himself with the needs of the Community, which naturally resulted in his involvement at the Company where he worked with the problems of his workmates. Along with other like thinking persons, he formed the E.I.W.U. in the Cape, holding meetings at his home in Kayter Road Crawford. The Branch in Durban, along with the Cape Town Branch formed E.I.W.U.S.A.
- Full Text:
- Date Issued: 1990
Cognitive-behavioral and existential-phenomenological approaches to therapy : complementary or conflicting paradigms?
- Authors: Edwards, D J A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6242 , http://hdl.handle.net/10962/d1007854
- Description: The relationship between the cognitive-behavioral and existential-phenomenological traditions in therapy is examined. While Beck cites phenomenological writers such as Heidegger, Husserl, and Binswanger, he does not initiate any dialogue with this tradition in depth. Parallels are drawn between the goals of psychotherapy as outlined by Rogers and goals identified in the contemporary cognitive-behavioral literature, between cognitive therapy's approach to clients' underlying assumptions and the phenomenological reduction as described by Husserl, and between a shared acceptance of the therapeutic use of the client-therapist interaction. While, in both approaches, therapists take on an educative role, in each approach a different aspect of the learning process is focused on. Phenomenological therapy's attitude to reality testing, the dangers of a directive stance by the therapist, the conflict between empathy and rational dialogue, and cognitive therapy's view of emotion are also discussed. The complementarity between the two approaches is emphasized and a continuing dialogue recommended.
- Full Text:
- Date Issued: 1990
- Authors: Edwards, D J A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6242 , http://hdl.handle.net/10962/d1007854
- Description: The relationship between the cognitive-behavioral and existential-phenomenological traditions in therapy is examined. While Beck cites phenomenological writers such as Heidegger, Husserl, and Binswanger, he does not initiate any dialogue with this tradition in depth. Parallels are drawn between the goals of psychotherapy as outlined by Rogers and goals identified in the contemporary cognitive-behavioral literature, between cognitive therapy's approach to clients' underlying assumptions and the phenomenological reduction as described by Husserl, and between a shared acceptance of the therapeutic use of the client-therapist interaction. While, in both approaches, therapists take on an educative role, in each approach a different aspect of the learning process is focused on. Phenomenological therapy's attitude to reality testing, the dangers of a directive stance by the therapist, the conflict between empathy and rational dialogue, and cognitive therapy's view of emotion are also discussed. The complementarity between the two approaches is emphasized and a continuing dialogue recommended.
- Full Text:
- Date Issued: 1990
Cognitive therapy and the restructuring of early memories through guided imagery
- Authors: Edwards, D J A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6241 , http://hdl.handle.net/10962/d1007853
- Description: This article describes the application of a guided imagery psychodrama technique to emotionally charged early memories. Such memories provide access to core schemata about the self and social relationships. Two case studies illustrate how the imagery technique enables the therapist to identify and restructure key cognitions out of which the schemata are constructed. The need for techniques to modify developmentally primitive schemata is discussed. Examples are given of ways to assist the patient in confronting the strong affect that may be aroused and in dealing with cognitions that block the process. Effectiveness is discussed in terms of the contribution of a guided imagery session to the overall process of ''learning to learn'' that takes place in cognitive psychotherapy.
- Full Text: false
- Date Issued: 1990
- Authors: Edwards, D J A
- Date: 1990
- Language: English
- Type: Article
- Identifier: vital:6241 , http://hdl.handle.net/10962/d1007853
- Description: This article describes the application of a guided imagery psychodrama technique to emotionally charged early memories. Such memories provide access to core schemata about the self and social relationships. Two case studies illustrate how the imagery technique enables the therapist to identify and restructure key cognitions out of which the schemata are constructed. The need for techniques to modify developmentally primitive schemata is discussed. Examples are given of ways to assist the patient in confronting the strong affect that may be aroused and in dealing with cognitions that block the process. Effectiveness is discussed in terms of the contribution of a guided imagery session to the overall process of ''learning to learn'' that takes place in cognitive psychotherapy.
- Full Text: false
- Date Issued: 1990
The taxonomy, biogeography and biology of cow and frilled sharks (Chondrichthyes : Hexanchiformes)
- Authors: Ebert, David A
- Date: 1990
- Subjects: Chondrichthyes Hexanchiformes Sharks
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5186 , http://hdl.handle.net/10962/d1001962
- Description: This study was undertaken to investigate the taxonomy, biogeography and biology of cow and frilled sharks (Chondrichthyes: Hexanchiformes). This taxon comprises two families, four genera and six extant species. The hexanchoids are a distinctive group of sharks characterized by six or seven paired gill openings, a single dorsal fin and an anal fin. Adult males of this group lack a siphon sac, but have in its place a clasper sac. This structure, which develops along the claspers, is unique to the Hexanchiformes. Hexanchoid sharks are widely distributed in area and depth. This group ranges from coastal bays and harbors along the open coast out across the continental shelf and down along the slopes to considerable depths. They occur from the equatorial zone to sub-polar regions. However, little is known about the ecology and life history of these sharks. Intraspecific variation of meristic counts were generally low for the Hexanchidae, but high for the Chlamydoselachidae, indicating that subpopulations, subspecies or even additional, new species exist within this family. Based on the indicators used in this study, maturity in male frilled sharks was attained at 916 mm TL, perlon sharks between 700 and 800 mm TL, sixgill sharks approximately 3140 mm TL, bigeyed sixgill sharks at about 1250 mm TL and sevengill sharks at approximately 1550 mm TL. Male reproductive success did not appear to be seasonal since males were found to contain viable sperm all year round. Female perlon sharks begin maturing between 950 mm and 1100 mm TL. Gravid females and newborns were absent from the other size classes and it is suspected that they aggregate in different locations to those of adult males and non-breeding females. Adult females are known at 4210 mm TL and immature at 3500 mm TL, However, a more accurate estimate of the size at maturity is wanting. Newborn sixgills were caught off southern Namibia during mid to late summer over three successive seasons. The occurrence of gravid females carrying term embryos during spring months and newborns during the summer months suggests a late spring or summer pupping period. Sixgill and sevengill sharks give birth in areas of high primary productivity. Energetically, this is advantageous for the newborns to be placed in an area with an abundant food source. The rapid growth rates of sixgill and sevengill sharks over the first year would enhance their survivorship since neither species has many predators. The number of female sevengills entering the breeding population is regulated to ensure that some portion of the population is reproductively active at any one time. The "staggering" of females which enter into the breeding population in any given year indicates a two year reproductive cycle. Fecundity estimates for 19 specimens with a largest egg diameter of at least 40 mm indicates a litter size of 67 to 104. The recapture of an adult female sevengill in approximately the same location in which it was tagged suggests that the same individual sharks may return to the same breeding grounds. As with any predators, sharks tend to exploit advantages over their prey. The hexanchoids, especially the sevengill, have evolved complex foraging strategies including social facilitation whereby they actively hunt in packs for large prey species. Sharks of the order Hexanchiformes, although lacking the diversity of the major shark orders, nonetheless play an integral role in the marine environment. The group's success can be attributed to their apical trophic position. In most habitats in which they occur, hexanchoids have no comparable competitors since equivalent sized sympatric squaloids and carcharhinoids feed at a lower trophic level.
- Full Text:
- Date Issued: 1990
- Authors: Ebert, David A
- Date: 1990
- Subjects: Chondrichthyes Hexanchiformes Sharks
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5186 , http://hdl.handle.net/10962/d1001962
- Description: This study was undertaken to investigate the taxonomy, biogeography and biology of cow and frilled sharks (Chondrichthyes: Hexanchiformes). This taxon comprises two families, four genera and six extant species. The hexanchoids are a distinctive group of sharks characterized by six or seven paired gill openings, a single dorsal fin and an anal fin. Adult males of this group lack a siphon sac, but have in its place a clasper sac. This structure, which develops along the claspers, is unique to the Hexanchiformes. Hexanchoid sharks are widely distributed in area and depth. This group ranges from coastal bays and harbors along the open coast out across the continental shelf and down along the slopes to considerable depths. They occur from the equatorial zone to sub-polar regions. However, little is known about the ecology and life history of these sharks. Intraspecific variation of meristic counts were generally low for the Hexanchidae, but high for the Chlamydoselachidae, indicating that subpopulations, subspecies or even additional, new species exist within this family. Based on the indicators used in this study, maturity in male frilled sharks was attained at 916 mm TL, perlon sharks between 700 and 800 mm TL, sixgill sharks approximately 3140 mm TL, bigeyed sixgill sharks at about 1250 mm TL and sevengill sharks at approximately 1550 mm TL. Male reproductive success did not appear to be seasonal since males were found to contain viable sperm all year round. Female perlon sharks begin maturing between 950 mm and 1100 mm TL. Gravid females and newborns were absent from the other size classes and it is suspected that they aggregate in different locations to those of adult males and non-breeding females. Adult females are known at 4210 mm TL and immature at 3500 mm TL, However, a more accurate estimate of the size at maturity is wanting. Newborn sixgills were caught off southern Namibia during mid to late summer over three successive seasons. The occurrence of gravid females carrying term embryos during spring months and newborns during the summer months suggests a late spring or summer pupping period. Sixgill and sevengill sharks give birth in areas of high primary productivity. Energetically, this is advantageous for the newborns to be placed in an area with an abundant food source. The rapid growth rates of sixgill and sevengill sharks over the first year would enhance their survivorship since neither species has many predators. The number of female sevengills entering the breeding population is regulated to ensure that some portion of the population is reproductively active at any one time. The "staggering" of females which enter into the breeding population in any given year indicates a two year reproductive cycle. Fecundity estimates for 19 specimens with a largest egg diameter of at least 40 mm indicates a litter size of 67 to 104. The recapture of an adult female sevengill in approximately the same location in which it was tagged suggests that the same individual sharks may return to the same breeding grounds. As with any predators, sharks tend to exploit advantages over their prey. The hexanchoids, especially the sevengill, have evolved complex foraging strategies including social facilitation whereby they actively hunt in packs for large prey species. Sharks of the order Hexanchiformes, although lacking the diversity of the major shark orders, nonetheless play an integral role in the marine environment. The group's success can be attributed to their apical trophic position. In most habitats in which they occur, hexanchoids have no comparable competitors since equivalent sized sympatric squaloids and carcharhinoids feed at a lower trophic level.
- Full Text:
- Date Issued: 1990
MORB-related dolerites associated with the final phases of Karoo flood basalt volcanism in southern Africa.
- Duncan, Andrew R, Armstrong, R A, Erlank, Anthony J, Marsh, Julian S, Watkins, R T
- Authors: Duncan, Andrew R , Armstrong, R A , Erlank, Anthony J , Marsh, Julian S , Watkins, R T
- Date: 1990
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/143299 , vital:38222 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailampidt=6938249
- Description: The Rooi Rand dyke swarm is approximately 200km long and up to 20km wide. It crops out in the southern portion of the Lebombo monocline where the dykes intrude basalts of the Sabie River Basalt Formation which is the major basaltic unit in the eastern portion of the Karoo volcanic succession. The Horingbaai dolerites form thin dykes and sills which intrude the base of the Etendeka lava pile (considered part of the Karoo Volcanics, but correlated with the Serra Geral Formation of Brazil) along the coast of Namibia. Both the Rooi Rand and Horingbaai magma types are similar in composition to enriched MORB and are compositionally distinct from most of the Karoo-basalts they intrude.
- Full Text:
- Date Issued: 1990
- Authors: Duncan, Andrew R , Armstrong, R A , Erlank, Anthony J , Marsh, Julian S , Watkins, R T
- Date: 1990
- Language: English
- Type: text , conference paper
- Identifier: http://hdl.handle.net/10962/143299 , vital:38222 , https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetailampidt=6938249
- Description: The Rooi Rand dyke swarm is approximately 200km long and up to 20km wide. It crops out in the southern portion of the Lebombo monocline where the dykes intrude basalts of the Sabie River Basalt Formation which is the major basaltic unit in the eastern portion of the Karoo volcanic succession. The Horingbaai dolerites form thin dykes and sills which intrude the base of the Etendeka lava pile (considered part of the Karoo Volcanics, but correlated with the Serra Geral Formation of Brazil) along the coast of Namibia. Both the Rooi Rand and Horingbaai magma types are similar in composition to enriched MORB and are compositionally distinct from most of the Karoo-basalts they intrude.
- Full Text:
- Date Issued: 1990
Sand inundation on rocky shores : its effects on species richness and the structure of species assemblages
- Authors: Dower, Katherine Mary
- Date: 1990
- Subjects: Intertidal ecology , Tide pool ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5814 , http://hdl.handle.net/10962/d1007183 , Intertidal ecology , Tide pool ecology
- Description: Although sand deposits are present on many intertidal rocky shores, their effects on species richness, zonation and trophic structure have often been overlooked. This study is the first to recognise sand as an important abiotic factor on South African rocky shores. Rocky shores in the eastern Cape Province of South Africa are subject to extensive sand inundation and are composed of two hard substrata of differing topographies. Four sites on one substratum and six on the other were sampled quantitatively using quadrats. The biota were identified, counted and/ or weighed to provide a matrix of species biomass and numbers in separate zones. This matrix was then analysed using ordination and classification. A total of 321 species were identified which is more than local rocky or sandy shores. While the intermediate disturbance hypothesis would predict high species richness on these shores, it does not fully explain this richness nor the distribution of species assemblages. Habitat heterogeneity, including the dynamics of sand deposits, is strongly influenced by substratum topography and is the most important factor generating species richness. Abrasion by sand (sand scour) causes local reductions in richness but the presence of semi-permanent sand deposits allows habitation by psammophilic and sand-dependent species. As a result the biota of a sand inundated rocky shore includes both a full rocky shore and a large sandy beach component. Substratum topography controls patterns of sand deposition and retention and community analysis showed that samples were clustered primarily according to species richness and secondarily according to substratum type. Ordination of species identified an arc of species assemblages of decreasing levels of sand tolerance. These corresponded to sample groupings so that th assemblages found in various habitats were characterised by particular levels of sand tolerance. The presence of sand has a negative effect on the biomass of primary producers and filter feeders but a positive effect on the biomass of deposit feeders. Because sand is retained to different degrees in different zones, trophic structure varies between zones and to a lesser extent, between rock types. In general, however, the trophic structure of sand inundated rocky shores is similar to that of non-inundated shores.
- Full Text:
- Date Issued: 1990
- Authors: Dower, Katherine Mary
- Date: 1990
- Subjects: Intertidal ecology , Tide pool ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5814 , http://hdl.handle.net/10962/d1007183 , Intertidal ecology , Tide pool ecology
- Description: Although sand deposits are present on many intertidal rocky shores, their effects on species richness, zonation and trophic structure have often been overlooked. This study is the first to recognise sand as an important abiotic factor on South African rocky shores. Rocky shores in the eastern Cape Province of South Africa are subject to extensive sand inundation and are composed of two hard substrata of differing topographies. Four sites on one substratum and six on the other were sampled quantitatively using quadrats. The biota were identified, counted and/ or weighed to provide a matrix of species biomass and numbers in separate zones. This matrix was then analysed using ordination and classification. A total of 321 species were identified which is more than local rocky or sandy shores. While the intermediate disturbance hypothesis would predict high species richness on these shores, it does not fully explain this richness nor the distribution of species assemblages. Habitat heterogeneity, including the dynamics of sand deposits, is strongly influenced by substratum topography and is the most important factor generating species richness. Abrasion by sand (sand scour) causes local reductions in richness but the presence of semi-permanent sand deposits allows habitation by psammophilic and sand-dependent species. As a result the biota of a sand inundated rocky shore includes both a full rocky shore and a large sandy beach component. Substratum topography controls patterns of sand deposition and retention and community analysis showed that samples were clustered primarily according to species richness and secondarily according to substratum type. Ordination of species identified an arc of species assemblages of decreasing levels of sand tolerance. These corresponded to sample groupings so that th assemblages found in various habitats were characterised by particular levels of sand tolerance. The presence of sand has a negative effect on the biomass of primary producers and filter feeders but a positive effect on the biomass of deposit feeders. Because sand is retained to different degrees in different zones, trophic structure varies between zones and to a lesser extent, between rock types. In general, however, the trophic structure of sand inundated rocky shores is similar to that of non-inundated shores.
- Full Text:
- Date Issued: 1990
The evaluation of qualitative examination questions at matriculation level in physics
- Authors: Dixon, Charles Harwood
- Date: 1990
- Subjects: Physics -- Study and teaching (Secondary) , Physics -- Examinations, questions, etc.
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1373 , http://hdl.handle.net/10962/d1001439
- Description: The style and format of Physics examination papers has changed markedly over the past hundred years. Physics was regarded formerly as a sub-division of Mathematics; hence, apart from giving formal statements of scientific laws, and some account of experimental procedures, examination candidates were required to spend most of their time, and to earn most of their marks by solving numerical problems. Most Physics examination papers today retain the emphasis on problem-solving by calculation. It has been recognised, however, that the ability to obtain correct numerical answers by substition in a formula does not necessarily imply understanding of the physical principles which underly the problem. There has been a reaction against the awarding of marks for algebraic or arithmetical manipulation. Bloom and his disciples, by calling on examiners to define precise behavioural objectives, have encouraged the development of qualitative questions. These require no calculation nor numerical answer, but do aim to test the candidate's insight, by requiring him either to explain phenomena in scientific terms, or to predict the outcome of changing conditions. In this investigation samples of both quantitative and qualitative questions were extracted from Physics papers past and present. A closer study was made of qualitative questions used in the Natal Senior Certificate Physics papers (both Higher Grade and Standard Grade) in November 1987. The examiners were asked to state the objective of each question, as well as its categorization in terms of a simplified Bloom taxonomy. Candidates' answers to these questions were extracted from the scripts written at a representative sample of Natal schools. In the case of multiple-choice questions, an item analysis was performed, and discrimination indices were calculated . The responses of individual candidates to the longer questions were collected, classified and discussed. In each case the effectiveness of the question was studied, as to whether or not it was successful in detecting the presence of correct scientific concepts in the candidates' thinking. It was concluded that most of the qualitative questions used by the examiners were effective. Suggestions were made as to how their efficacy could be improved. Much further study and experimentation are needed to develop the effective use of this type of question
- Full Text:
- Date Issued: 1990
- Authors: Dixon, Charles Harwood
- Date: 1990
- Subjects: Physics -- Study and teaching (Secondary) , Physics -- Examinations, questions, etc.
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1373 , http://hdl.handle.net/10962/d1001439
- Description: The style and format of Physics examination papers has changed markedly over the past hundred years. Physics was regarded formerly as a sub-division of Mathematics; hence, apart from giving formal statements of scientific laws, and some account of experimental procedures, examination candidates were required to spend most of their time, and to earn most of their marks by solving numerical problems. Most Physics examination papers today retain the emphasis on problem-solving by calculation. It has been recognised, however, that the ability to obtain correct numerical answers by substition in a formula does not necessarily imply understanding of the physical principles which underly the problem. There has been a reaction against the awarding of marks for algebraic or arithmetical manipulation. Bloom and his disciples, by calling on examiners to define precise behavioural objectives, have encouraged the development of qualitative questions. These require no calculation nor numerical answer, but do aim to test the candidate's insight, by requiring him either to explain phenomena in scientific terms, or to predict the outcome of changing conditions. In this investigation samples of both quantitative and qualitative questions were extracted from Physics papers past and present. A closer study was made of qualitative questions used in the Natal Senior Certificate Physics papers (both Higher Grade and Standard Grade) in November 1987. The examiners were asked to state the objective of each question, as well as its categorization in terms of a simplified Bloom taxonomy. Candidates' answers to these questions were extracted from the scripts written at a representative sample of Natal schools. In the case of multiple-choice questions, an item analysis was performed, and discrimination indices were calculated . The responses of individual candidates to the longer questions were collected, classified and discussed. In each case the effectiveness of the question was studied, as to whether or not it was successful in detecting the presence of correct scientific concepts in the candidates' thinking. It was concluded that most of the qualitative questions used by the examiners were effective. Suggestions were made as to how their efficacy could be improved. Much further study and experimentation are needed to develop the effective use of this type of question
- Full Text:
- Date Issued: 1990
Aspects of the biology of the infaunal bivalve Mollusc Solen cylindraceus (Hanley) in the Kariega estuary
- De Villiers, Casper Johannes
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
Fest-Quest '89: a survey of visitors to the 1989 Standard Bank Arts Festival
- Authors: Davies, William J
- Date: 1990
- Subjects: Standard Bank National Arts Festival Art festivals -- South Africa Performing arts -- South Africa Art and society -- South Africa
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/1730 , vital:20220 , ISBN 0868101990
- Description: The Standard Bank National Arts Festival is an annual event which invades the City of Grahamstown in early July. Over the years, it has become an important national cultural showcase of theatre, dance, music, and fine art. It also attracts a wide variety of handicraft and hone industry vendors, which together with other peripheral activities, transforms the City into a bustling place imbued with a festive atmosphere. Apart from its cultural significance, the Festival means a great deal to the local economy because it attracts visitors from all over the country who spend several million rand whilst they are in Grahamstown. The Development Studies Unit at Rhodes University and the 1820 Foundation have monitored the nature and extent of the festival's impact on Grahamstown since 1987. Information is collected by means of a voluntary questionnaire (the Fest-Quest) which provides a useful resource for the Festival organisers as well as insights into the relative economic importance of the occasion. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1990
- Authors: Davies, William J
- Date: 1990
- Subjects: Standard Bank National Arts Festival Art festivals -- South Africa Performing arts -- South Africa Art and society -- South Africa
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/1730 , vital:20220 , ISBN 0868101990
- Description: The Standard Bank National Arts Festival is an annual event which invades the City of Grahamstown in early July. Over the years, it has become an important national cultural showcase of theatre, dance, music, and fine art. It also attracts a wide variety of handicraft and hone industry vendors, which together with other peripheral activities, transforms the City into a bustling place imbued with a festive atmosphere. Apart from its cultural significance, the Festival means a great deal to the local economy because it attracts visitors from all over the country who spend several million rand whilst they are in Grahamstown. The Development Studies Unit at Rhodes University and the 1820 Foundation have monitored the nature and extent of the festival's impact on Grahamstown since 1987. Information is collected by means of a voluntary questionnaire (the Fest-Quest) which provides a useful resource for the Festival organisers as well as insights into the relative economic importance of the occasion. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1990
Community-based co-operative ventures in Port Elizabeth
- Authors: Davies, William J
- Date: 1990
- Subjects: Cities and towns -- Africa Cooperative societies Economic development Producer cooperatives Port Elizabeth (South Africa) -- Economic conditions
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/2329 , vital:20276 , ISBN 0868102032
- Description: This Working Paper reports on the results of an investigation into community-based co-operative ventures in Port Elizabeth. It represents part of an on-going research programme dealing with Black economic development undertaken by the Development Studies Unit (DSU) at Rhodes University. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1990
- Authors: Davies, William J
- Date: 1990
- Subjects: Cities and towns -- Africa Cooperative societies Economic development Producer cooperatives Port Elizabeth (South Africa) -- Economic conditions
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/2329 , vital:20276 , ISBN 0868102032
- Description: This Working Paper reports on the results of an investigation into community-based co-operative ventures in Port Elizabeth. It represents part of an on-going research programme dealing with Black economic development undertaken by the Development Studies Unit (DSU) at Rhodes University. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1990
1820 Foundation publications: an evaluation for the 1820 Foundation
- Davies, William J, Stewart, G M
- Authors: Davies, William J , Stewart, G M
- Date: 1990
- Subjects: 1820 Foundation -- Bibliography 1820 Foundation Standard Bank National Arts Festival Standard Bank National Schools Festival 1820 Foundation. Eisteddfod Anglo de Beers English Olympiad Gold Shield Award In-service education and training for teachers
- Language: English
- Type: Book
- Identifier: http://hdl.handle.net/10962/1639 , vital:20212
- Full Text:
- Date Issued: 1990
- Authors: Davies, William J , Stewart, G M
- Date: 1990
- Subjects: 1820 Foundation -- Bibliography 1820 Foundation Standard Bank National Arts Festival Standard Bank National Schools Festival 1820 Foundation. Eisteddfod Anglo de Beers English Olympiad Gold Shield Award In-service education and training for teachers
- Language: English
- Type: Book
- Identifier: http://hdl.handle.net/10962/1639 , vital:20212
- Full Text:
- Date Issued: 1990
ICEF Energy conference
- CWIU
- Authors: CWIU
- Date: 1990
- Subjects: CWIU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/152450 , vital:39279
- Description: The decline in world energy consumption caused by the twin oil price hikes of 1973 and 1979 checked development in the major market economies and triggered the process of industrial restructuring that has so profoundly affected all sectors and all regions. ore efficient use of more expensive energy and strategic policy changes have made major contributions to easing the historical reliance upon energy inputs - especially in the case of oil. As a result the ratio between energy consumption and growth of gross world production has diminished by nearly 25 % over the past fifteen years. It has been estimated that full use of available energy-efficient technologies could cut per capita energy use by as much as 50% without impeding economic growth. The extent to which these gains are realized will depend upon a wide variety of economic and developmental factors, among which the price management of fuels is a very important one. here has also been a change in the industrial mix of the major OECD economies with the decline of old industries using high energy imputs and the rise of high technology sectors with different and lower energy requirements. The shift of much basic manufacturing to new locations in the developing world and to the hitherto centrally planned economies is likely to precipitate a further important change in energy requirements. emand for energy is forecast to continue to grow at only about half the rate of general economic growth over the short to medium term. Consumption is very uneven on a world scale, however. In 1988 the world consumed energy equivalent to some 8 billion tonnes of oil (Tonnes Oil Equivalent, or TOE) - an average of 1.3 tonnes for every man, woman and child on Earth. While citizens of the USA will consume an average of 8 TOE per capita, however, the average for both Japan and Western Europe is around 3 TOE, while people in the Third World still rely on fuelwood and dried animal dung as important energy resources, consuming only a small fraction of a TOE each in many cases.
- Full Text:
- Date Issued: 1990
- Authors: CWIU
- Date: 1990
- Subjects: CWIU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/152450 , vital:39279
- Description: The decline in world energy consumption caused by the twin oil price hikes of 1973 and 1979 checked development in the major market economies and triggered the process of industrial restructuring that has so profoundly affected all sectors and all regions. ore efficient use of more expensive energy and strategic policy changes have made major contributions to easing the historical reliance upon energy inputs - especially in the case of oil. As a result the ratio between energy consumption and growth of gross world production has diminished by nearly 25 % over the past fifteen years. It has been estimated that full use of available energy-efficient technologies could cut per capita energy use by as much as 50% without impeding economic growth. The extent to which these gains are realized will depend upon a wide variety of economic and developmental factors, among which the price management of fuels is a very important one. here has also been a change in the industrial mix of the major OECD economies with the decline of old industries using high energy imputs and the rise of high technology sectors with different and lower energy requirements. The shift of much basic manufacturing to new locations in the developing world and to the hitherto centrally planned economies is likely to precipitate a further important change in energy requirements. emand for energy is forecast to continue to grow at only about half the rate of general economic growth over the short to medium term. Consumption is very uneven on a world scale, however. In 1988 the world consumed energy equivalent to some 8 billion tonnes of oil (Tonnes Oil Equivalent, or TOE) - an average of 1.3 tonnes for every man, woman and child on Earth. While citizens of the USA will consume an average of 8 TOE per capita, however, the average for both Japan and Western Europe is around 3 TOE, while people in the Third World still rely on fuelwood and dried animal dung as important energy resources, consuming only a small fraction of a TOE each in many cases.
- Full Text:
- Date Issued: 1990