Geochemical and petrological trends in the UG2-Merensky unit interval of the upper critical zone in the Western Bushveld Complex
- Authors: Maier, Wolfgang Derek
- Date: 1992
- Subjects: Petrology -- South Africa -- North-western Transvaal Geochemistry -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4951 , http://hdl.handle.net/10962/d1005563
- Description: One of the most remarkable features of the layered sequence of the Bushveld Complex is its lateral consistency in lithology. This work has established a geochemical and lithological correlation along 170 km of strike of the interval between the UG2 chromitite and the Merensky Reef within the Upper Critical zone of the western limb of the Bushveld Complex. The correlation is based on geochemical investigations of 10 borehole intersections and lithological comparisons of more than 20 borehole intersections around the western lobe of the complex. The basic data presented include 123 whole-rock analyses for major and 12 trace elements, 97 analyses for ' 12 trace elements, and ca. 5500 microprobe analyses of all major phases. Patterns of cryptic variation are established. Some layers (the UG2 chromitite and pyroxenite) show considerable consistency with regard to geochemistry and lithology. Others can be traced along most of the investigated strike length, such as the Lone Chrome Seam, the Footwall Marker anorthosite and the immediate anorthosite footwall to the Merensky Unit. Most of the distinguishable members within the study section, however, show great variation along strike (i.e., the Lower and Upper Pseudoreef Markers, the central noritic sequence in the southern arm of the western limb and parts of the immediate Merensky Reef footwall succession). Several models have been evaluated to interpret the geochemical and lithological data. The author comes to the conclusion that the degree of lithological consistency depends on the variability of magmatic parameters within different parts of the chamber. The most important of these parameters are: (i) the size of fresh primitive influxes and consequently the heat flux, (ii) the composition of the residual liquid, and (iii) the frequency of the influxes. Fresh influxes of more or less similar composition thus spread out along the floor if the residual liquid was less dense than the fresh primitive liquid, but intruded the chamber as a plume where plagioclase had crystallized for some time and the residual liquid had become relatively dense. The size of the influx may be regarded as a measure of the amount of heat flux from the feeder into the chamber. A large influx created uniform physicochemical conditions in the chamber whereas a smaller influx created a strong lateral gradient of physicochemical parameters in the chamber, with subsequent differences in viscosity, density, convection currents, yield strength and thus different mixing behaviour of different liquids. Furthermore, a persistent heat flux from the feeder may have delayed crystallization of successive phases in those parts of the chamber proximal to the feeder . Therefore, new influxes would have been deposited on a footwall of varying thickness and lithology in response to different degrees of crystallization and accumulation along strike. The development of a normal cyclic unit (chromititeharzburgite-pyroxenite-norite (+anorthosite?)) may thus have been interrupted at various stages in different parts of the chamber. The ability to correlate anorthosites over great strike distances implies that their formation did not follow entirely random processes but was dependent on specific magmatic conditions which prevailed over laterally extensive portions of the chamber at certain stages during the evolution of the crystallizing liquid.
- Full Text:
- Authors: Maier, Wolfgang Derek
- Date: 1992
- Subjects: Petrology -- South Africa -- North-western Transvaal Geochemistry -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4951 , http://hdl.handle.net/10962/d1005563
- Description: One of the most remarkable features of the layered sequence of the Bushveld Complex is its lateral consistency in lithology. This work has established a geochemical and lithological correlation along 170 km of strike of the interval between the UG2 chromitite and the Merensky Reef within the Upper Critical zone of the western limb of the Bushveld Complex. The correlation is based on geochemical investigations of 10 borehole intersections and lithological comparisons of more than 20 borehole intersections around the western lobe of the complex. The basic data presented include 123 whole-rock analyses for major and 12 trace elements, 97 analyses for ' 12 trace elements, and ca. 5500 microprobe analyses of all major phases. Patterns of cryptic variation are established. Some layers (the UG2 chromitite and pyroxenite) show considerable consistency with regard to geochemistry and lithology. Others can be traced along most of the investigated strike length, such as the Lone Chrome Seam, the Footwall Marker anorthosite and the immediate anorthosite footwall to the Merensky Unit. Most of the distinguishable members within the study section, however, show great variation along strike (i.e., the Lower and Upper Pseudoreef Markers, the central noritic sequence in the southern arm of the western limb and parts of the immediate Merensky Reef footwall succession). Several models have been evaluated to interpret the geochemical and lithological data. The author comes to the conclusion that the degree of lithological consistency depends on the variability of magmatic parameters within different parts of the chamber. The most important of these parameters are: (i) the size of fresh primitive influxes and consequently the heat flux, (ii) the composition of the residual liquid, and (iii) the frequency of the influxes. Fresh influxes of more or less similar composition thus spread out along the floor if the residual liquid was less dense than the fresh primitive liquid, but intruded the chamber as a plume where plagioclase had crystallized for some time and the residual liquid had become relatively dense. The size of the influx may be regarded as a measure of the amount of heat flux from the feeder into the chamber. A large influx created uniform physicochemical conditions in the chamber whereas a smaller influx created a strong lateral gradient of physicochemical parameters in the chamber, with subsequent differences in viscosity, density, convection currents, yield strength and thus different mixing behaviour of different liquids. Furthermore, a persistent heat flux from the feeder may have delayed crystallization of successive phases in those parts of the chamber proximal to the feeder . Therefore, new influxes would have been deposited on a footwall of varying thickness and lithology in response to different degrees of crystallization and accumulation along strike. The development of a normal cyclic unit (chromititeharzburgite-pyroxenite-norite (+anorthosite?)) may thus have been interrupted at various stages in different parts of the chamber. The ability to correlate anorthosites over great strike distances implies that their formation did not follow entirely random processes but was dependent on specific magmatic conditions which prevailed over laterally extensive portions of the chamber at certain stages during the evolution of the crystallizing liquid.
- Full Text:
Geological controls for coal exploration and mining
- Authors: Noppé , Mark Adrian
- Date: 1992
- Subjects: Coal -- Geology , Coal mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4954 , http://hdl.handle.net/10962/d1005566 , Coal -- Geology , Coal mines and mining
- Description: The identification and interpretation of geological features is essential for the planning and ultimate success of any mining venture. Examples of geological features significant for mining are presented, and their identification during exploration discussed. In particular, the importance of coal qualities, seam thickness and seam elevation are emphasised in relation to longwall mining. Geostatistical analysis provides a powerful tool for improving the prediction and decision-making capabilities of both exploration and mine geologists. The availability of geostatistics, and the benefits resulting from its application, are demonstrated using actual data for calorific value, seam thickness and seam elevation. Contamination of run-of-mine coal is a common problem on highly-mechanised collieries. The problem generally arises from over-cutting of the designated mining horizon. A practical system for monitoring and controlling contamination on a mechanised bord-and-pillar and longwall colliery is presented. The results and benefits of applying such a system are cited for an actual longwall colliery. Numerical geological predictions are not always reported in terms of the reliability of such estimates. Many of these values can be reported in terms of confidence limits, particularly for routine grade control purposes. The methods and benefits of such reporting are described and illustrated by way of examples for calorific value and contamination levels.
- Full Text:
- Authors: Noppé , Mark Adrian
- Date: 1992
- Subjects: Coal -- Geology , Coal mines and mining
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4954 , http://hdl.handle.net/10962/d1005566 , Coal -- Geology , Coal mines and mining
- Description: The identification and interpretation of geological features is essential for the planning and ultimate success of any mining venture. Examples of geological features significant for mining are presented, and their identification during exploration discussed. In particular, the importance of coal qualities, seam thickness and seam elevation are emphasised in relation to longwall mining. Geostatistical analysis provides a powerful tool for improving the prediction and decision-making capabilities of both exploration and mine geologists. The availability of geostatistics, and the benefits resulting from its application, are demonstrated using actual data for calorific value, seam thickness and seam elevation. Contamination of run-of-mine coal is a common problem on highly-mechanised collieries. The problem generally arises from over-cutting of the designated mining horizon. A practical system for monitoring and controlling contamination on a mechanised bord-and-pillar and longwall colliery is presented. The results and benefits of applying such a system are cited for an actual longwall colliery. Numerical geological predictions are not always reported in terms of the reliability of such estimates. Many of these values can be reported in terms of confidence limits, particularly for routine grade control purposes. The methods and benefits of such reporting are described and illustrated by way of examples for calorific value and contamination levels.
- Full Text:
Guidelines to the evaluation of selectively mined, open pit gold deposits during the exploration stage of mine creation
- Pelly, Frederick Douglas Peter
- Authors: Pelly, Frederick Douglas Peter
- Date: 1992
- Subjects: Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4970 , http://hdl.handle.net/10962/d1005582 , Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Description: This dissertation studies the evaluation of selectively mined, open pit gold deposits during the exploration stage of the mine's life. Since 1970 a large number of selectively mined, open pit gold mines have come into operation. The most common deposits include epithermal vein, mesothermal lode and laterite gold deposits. In general the deposits are characterized by small tonnages (1-20 million tonnes), relatively high grades (2-10 grams per tonne gold), submicroscopic to coarse gold, inexpensive mining, and both free milling and refractory ores.The key components that require evaluating during the exploration period are the deposit's geology, ore reserves, pit design, ore metallurgy and environmental impact. Feasibility studies are the main vehicle by which to report and guide the exploration programme. During the exploration period a company may undertake an initial (geological feasibility), second (preliminary mine feasibility) and third (final feasibility) delineation programme in order to gather sufficient data to justify a mine development decision. The responsibility of evaluating the mineral prospect lies primarily with the exploration geologist and mining engineer. Broad experience, a professional attitude, a thorough understanding of mining economics, and a high level of geological, engineering and technical skills are traits required by the evaluators. In order for mining companies to make sound investment decisions the geographical, geological, mining, metallurgical, environmental, marketing, political and financial aspects affecting the economic potential of the venture must be integrated so that the likely costs, risks and returns of the investment alternative are quantified. Ultimately, it is the economic analysis of these three items that determine whether the mineral prospect is developed into a mine I delineated further I retained until economic circumstances improve, or abandoned. To assess the costs, risks and returns, extensive use of the risk analysis is advocated throughout the exploration period . When combined with intelligent judgement of the intangible risk elements, the probabilistic distribution of discounted cash flows are invaluable in making sound investment decisions. However, the economic analysis is only as good as the information on which it is founded. Accurate and representative field data is the most important prerequisite to successfully evaluating and developing a new mine.
- Full Text:
- Authors: Pelly, Frederick Douglas Peter
- Date: 1992
- Subjects: Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4970 , http://hdl.handle.net/10962/d1005582 , Mining geology , Gold ores -- Geology , Gold mines and mining -- Economic aspects
- Description: This dissertation studies the evaluation of selectively mined, open pit gold deposits during the exploration stage of the mine's life. Since 1970 a large number of selectively mined, open pit gold mines have come into operation. The most common deposits include epithermal vein, mesothermal lode and laterite gold deposits. In general the deposits are characterized by small tonnages (1-20 million tonnes), relatively high grades (2-10 grams per tonne gold), submicroscopic to coarse gold, inexpensive mining, and both free milling and refractory ores.The key components that require evaluating during the exploration period are the deposit's geology, ore reserves, pit design, ore metallurgy and environmental impact. Feasibility studies are the main vehicle by which to report and guide the exploration programme. During the exploration period a company may undertake an initial (geological feasibility), second (preliminary mine feasibility) and third (final feasibility) delineation programme in order to gather sufficient data to justify a mine development decision. The responsibility of evaluating the mineral prospect lies primarily with the exploration geologist and mining engineer. Broad experience, a professional attitude, a thorough understanding of mining economics, and a high level of geological, engineering and technical skills are traits required by the evaluators. In order for mining companies to make sound investment decisions the geographical, geological, mining, metallurgical, environmental, marketing, political and financial aspects affecting the economic potential of the venture must be integrated so that the likely costs, risks and returns of the investment alternative are quantified. Ultimately, it is the economic analysis of these three items that determine whether the mineral prospect is developed into a mine I delineated further I retained until economic circumstances improve, or abandoned. To assess the costs, risks and returns, extensive use of the risk analysis is advocated throughout the exploration period . When combined with intelligent judgement of the intangible risk elements, the probabilistic distribution of discounted cash flows are invaluable in making sound investment decisions. However, the economic analysis is only as good as the information on which it is founded. Accurate and representative field data is the most important prerequisite to successfully evaluating and developing a new mine.
- Full Text:
How taboo are taboo words for girls?
- Authors: De Klerk, Vivian A
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6143 , http://hdl.handle.net/10962/d1011596
- Description: In the past five years, there has been much interest in the question of whether women are really as concerned about politeness and status as they have been made out to be by such writers as Baroni and D'Urso (1984), Crosby and Nyquist (1977), Lakoff (1973), Spender (1980), and Trudgill (1972). Despite the commonly held perception that it is only males who bandy about derogatory and taboo words (Bailey 1985; Flexner 1975), Risch (1987) provided counterevidence based on data obtained in the United States. The results of the present study, based on data obtained in South Africa, strongly support her findings and challenge the assumption that women stick to standard speech, citing evidence that young females are familiar with, and use, a wide range of highly taboo/slang items themselves. In particular, attention is devoted to the question of pejorative words applicable to males and females, respectively, and the view that there are only a few pejorative terms commonly used to describe males (particularly by females) is challenged. (Women's language, politeness, linguistic taboo, stereotypes, slang, expletives, prestige forms).
- Full Text:
- Authors: De Klerk, Vivian A
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6143 , http://hdl.handle.net/10962/d1011596
- Description: In the past five years, there has been much interest in the question of whether women are really as concerned about politeness and status as they have been made out to be by such writers as Baroni and D'Urso (1984), Crosby and Nyquist (1977), Lakoff (1973), Spender (1980), and Trudgill (1972). Despite the commonly held perception that it is only males who bandy about derogatory and taboo words (Bailey 1985; Flexner 1975), Risch (1987) provided counterevidence based on data obtained in the United States. The results of the present study, based on data obtained in South Africa, strongly support her findings and challenge the assumption that women stick to standard speech, citing evidence that young females are familiar with, and use, a wide range of highly taboo/slang items themselves. In particular, attention is devoted to the question of pejorative words applicable to males and females, respectively, and the view that there are only a few pejorative terms commonly used to describe males (particularly by females) is challenged. (Women's language, politeness, linguistic taboo, stereotypes, slang, expletives, prestige forms).
- Full Text:
Illness as intersubjectivity: a sociological perspective
- Authors: Pitfield, Doreen Jennie
- Date: 1992
- Subjects: Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3329 , http://hdl.handle.net/10962/d1003117 , Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Description: This thesis explores the historical roots of scientific medicine in an effort to highlight the lack of humanist intersubjectivity within the contemporary medical model. The study notes that contemporary medicine is overtly scientific and that its scientific framework is upheld and furthered by a medical model which draws legitimation from the irrefutability of what is referred to variously within this work, as its scientific "regime". It is shown that in terms of the humanist tradition people, not science, constitute the epicentre of meaningful experiential participation in the defining of human social reality. This, it is argued, implies a radically different ontology from other sociological perspectives on medicine. The thesis suggests that the contemporary medical model loses sight of the patient's ability to cognitively participate in the defining of illness, diagnosis and treatment in terms of his/her experience thereof , and argues that contemporary medicine, by advancing the idea that it alone has the correct and only answer to such problems, has led to a situation which promotes an overmedicalisation of society . The study gives an indication of the way in which this overmedicalisation has led to areas of human life becoming conceived of only in relation to medical expertise. In this respect it is noted that medicine has so successfully infiltrated the human consciousness (involving areas as diverse as childbirth, genetic engineering, transplant surgery and death), that decisions on health are invariably taken from a foundation of scientific legitimation which seems to exclude the patient as subject. It is argued that this way of making decisions reinforces the requirement for a scientific medical model which as it negates the human element insidiously amplifies its power over human life; thereby devaluing the very people it seeks to serve. The thesis suggests that in terms of a humanist reading of the Oath of Hippocrates, medical decisions can only be taken within a framework of experiential involvement which includes both medical expertise and lay understanding. It is indicated that when this happens, social reality functions in terms of a symbolic participation which fosters a commitment to equalise the conditions of human existence, and promotes a dialogical negotiatory process which is both intersubjectively and ongoingly produced.
- Full Text:
- Authors: Pitfield, Doreen Jennie
- Date: 1992
- Subjects: Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3329 , http://hdl.handle.net/10962/d1003117 , Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Description: This thesis explores the historical roots of scientific medicine in an effort to highlight the lack of humanist intersubjectivity within the contemporary medical model. The study notes that contemporary medicine is overtly scientific and that its scientific framework is upheld and furthered by a medical model which draws legitimation from the irrefutability of what is referred to variously within this work, as its scientific "regime". It is shown that in terms of the humanist tradition people, not science, constitute the epicentre of meaningful experiential participation in the defining of human social reality. This, it is argued, implies a radically different ontology from other sociological perspectives on medicine. The thesis suggests that the contemporary medical model loses sight of the patient's ability to cognitively participate in the defining of illness, diagnosis and treatment in terms of his/her experience thereof , and argues that contemporary medicine, by advancing the idea that it alone has the correct and only answer to such problems, has led to a situation which promotes an overmedicalisation of society . The study gives an indication of the way in which this overmedicalisation has led to areas of human life becoming conceived of only in relation to medical expertise. In this respect it is noted that medicine has so successfully infiltrated the human consciousness (involving areas as diverse as childbirth, genetic engineering, transplant surgery and death), that decisions on health are invariably taken from a foundation of scientific legitimation which seems to exclude the patient as subject. It is argued that this way of making decisions reinforces the requirement for a scientific medical model which as it negates the human element insidiously amplifies its power over human life; thereby devaluing the very people it seeks to serve. The thesis suggests that in terms of a humanist reading of the Oath of Hippocrates, medical decisions can only be taken within a framework of experiential involvement which includes both medical expertise and lay understanding. It is indicated that when this happens, social reality functions in terms of a symbolic participation which fosters a commitment to equalise the conditions of human existence, and promotes a dialogical negotiatory process which is both intersubjectively and ongoingly produced.
- Full Text:
Images of a changing frontier worldview in Eastern Cape art from Bushman rock art to 1875
- Authors: Cosser, Marijke
- Date: 1992
- Subjects: Art, San , Rock paintings -- South Africa , Art, South African -- 19th century , Art -- South Africa -- History , Painters -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2400 , http://hdl.handle.net/10962/d1002196 , Art, San , Rock paintings -- South Africa , Art, South African -- 19th century , Art -- South Africa -- History , Painters -- South Africa
- Description: A discussion of the concept of worldview shows that how an artist conceives the world in his images is governed by his worldview - an amalgam of the worldview of the group of which he is a part modified by his own ideas, beliefs, attitudes, perceptions and upbringing. The author proposes that studying an artist's work can reveal his, and hence his group's, worldview and thus the attitudes prevalent when the work was produced. A brief historical sketch of the Eastern Cape to 1834 introduces the various settlers in the area. Though no known examples of Black, Boer or Khoi pictorial art are extant, both the Bushmen and the British left such records. A short analysis of rock art shows how the worldview of the Bushman is inherent in their images which reflect man's world as seen with the "inner" eye of the spirit. In white settler art, the author submits that spatial relationships changed in response to a growing confidence as the "savage" land was "civilised" and that the position, pose and size of figures - and the inclusion or exclusion of certain groups - reflect socio-political changes. The two foremost nineteenth-century Eastern Cape artists, Thomas Baines and Frederick I'Ons, succeeded in capturing the atmosphere of Frontier life but are shown to interpret their surroundings through the rose-tinted spectacles of British Romanticism. They also reveal individuality in approach - Baines preferring expansive views while I'Ons's landscapes tend to be "closed-in", strictly following the coulisse scheme of Picturesque painting. Perhaps, the author postulates, such differences result from the very different environments, i.e. Norfolk and London, in which the two grew up. I'Ons is shown typically to use generalised landscapes as backdrops for his foreground figures, while comparing Baines's scenes with modern photographs shows that he adjusted the spacial elements of the topography as well as the temporal sequence of events to suit aesthetic considerations. Lithographed reports of his work contain even further adjustments. The author concludes that the use of Africana art as historical records must be treated with great caution.
- Full Text:
- Authors: Cosser, Marijke
- Date: 1992
- Subjects: Art, San , Rock paintings -- South Africa , Art, South African -- 19th century , Art -- South Africa -- History , Painters -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2400 , http://hdl.handle.net/10962/d1002196 , Art, San , Rock paintings -- South Africa , Art, South African -- 19th century , Art -- South Africa -- History , Painters -- South Africa
- Description: A discussion of the concept of worldview shows that how an artist conceives the world in his images is governed by his worldview - an amalgam of the worldview of the group of which he is a part modified by his own ideas, beliefs, attitudes, perceptions and upbringing. The author proposes that studying an artist's work can reveal his, and hence his group's, worldview and thus the attitudes prevalent when the work was produced. A brief historical sketch of the Eastern Cape to 1834 introduces the various settlers in the area. Though no known examples of Black, Boer or Khoi pictorial art are extant, both the Bushmen and the British left such records. A short analysis of rock art shows how the worldview of the Bushman is inherent in their images which reflect man's world as seen with the "inner" eye of the spirit. In white settler art, the author submits that spatial relationships changed in response to a growing confidence as the "savage" land was "civilised" and that the position, pose and size of figures - and the inclusion or exclusion of certain groups - reflect socio-political changes. The two foremost nineteenth-century Eastern Cape artists, Thomas Baines and Frederick I'Ons, succeeded in capturing the atmosphere of Frontier life but are shown to interpret their surroundings through the rose-tinted spectacles of British Romanticism. They also reveal individuality in approach - Baines preferring expansive views while I'Ons's landscapes tend to be "closed-in", strictly following the coulisse scheme of Picturesque painting. Perhaps, the author postulates, such differences result from the very different environments, i.e. Norfolk and London, in which the two grew up. I'Ons is shown typically to use generalised landscapes as backdrops for his foreground figures, while comparing Baines's scenes with modern photographs shows that he adjusted the spacial elements of the topography as well as the temporal sequence of events to suit aesthetic considerations. Lithographed reports of his work contain even further adjustments. The author concludes that the use of Africana art as historical records must be treated with great caution.
- Full Text:
In search of home : Hillman's archetypal perspective on the therapeutic process of an adult patient
- Bradley, Margaret Antoinette
- Authors: Bradley, Margaret Antoinette
- Date: 1992
- Subjects: Hillman, James , Archetype (Psychology) , Psychotherapy -- Case studies
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3127 , http://hdl.handle.net/10962/d1006290 , Hillman, James , Archetype (Psychology) , Psychotherapy -- Case studies
- Description: The case study method was used to trace the therapeutic process of a 23 year old woman, over a period of 12 sessions. The focus of the study was her issue with abandonment which emerged as the central theme in therapy. Hillman's archetypal approach was used as a framework in understanding the process and resolution of her feelings of abandonment. According to Hillman, the therapy process activates the archetypal abandoned child. For a successful therapeutic outcome the process of de-literalisation must occur in order for the patient to move from literal acting out to symbolic containment. Core moments in the therapeutic process were used, together with an interpretation from Hillman's approach, to illustrate the various themes around the issue of abandonment. The present case study illustrates how the theory in area was relevant in practice with this particular case.
- Full Text:
- Authors: Bradley, Margaret Antoinette
- Date: 1992
- Subjects: Hillman, James , Archetype (Psychology) , Psychotherapy -- Case studies
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3127 , http://hdl.handle.net/10962/d1006290 , Hillman, James , Archetype (Psychology) , Psychotherapy -- Case studies
- Description: The case study method was used to trace the therapeutic process of a 23 year old woman, over a period of 12 sessions. The focus of the study was her issue with abandonment which emerged as the central theme in therapy. Hillman's archetypal approach was used as a framework in understanding the process and resolution of her feelings of abandonment. According to Hillman, the therapy process activates the archetypal abandoned child. For a successful therapeutic outcome the process of de-literalisation must occur in order for the patient to move from literal acting out to symbolic containment. Core moments in the therapeutic process were used, together with an interpretation from Hillman's approach, to illustrate the various themes around the issue of abandonment. The present case study illustrates how the theory in area was relevant in practice with this particular case.
- Full Text:
In vitro diffusion cell design and validation. II. Temperature, agitation and membrane effects on betamethasone 17-valerate permeation
- Smith, Eric W, Haigh, John M
- Authors: Smith, Eric W , Haigh, John M
- Date: 1992
- Language: English
- Type: text , Article
- Identifier: vital:6422 , http://hdl.handle.net/10962/d1006557
- Description: An in vitro permeation cell has been designed and validated for use in monitoring the transmembrane permeation of betamethasone 17-valerate. The design utilizes common laboratory equipment and incorporates as many beneficial features as possible from other designs. The importance of fully validating the hydrodynamic performance of the cell prior to experimentation is stressed. The cell was validated by monitoring the diffusion of betamethasone 17-valerate in isopropyl myristate solution into purified isopropyl myristate receptor phase at different temperatures, different agitation rates and through different synthetic and biological membranes. The results of the hydrodynamic validation agree with data from other researchers and show that the permeation cell is adequately sensitive to these experimental parameters. The results of the membrane evaluation allow appropriate selection of the barrier material for representative transdermal experiments to be conducted. While human and porcine stratum corneum/epidermis are similar in diffusive properties, hairless mouse skin appears to be the most convenient animal membrane for these studies. Although silicone and cellulose membranes appear to be useful in this application, porous filter membranes and egg-shell membranes are insufficiently discriminatory to betamethasone 17-valerate diffusion to provide useful in vitro permeation data.
- Full Text: false
- Authors: Smith, Eric W , Haigh, John M
- Date: 1992
- Language: English
- Type: text , Article
- Identifier: vital:6422 , http://hdl.handle.net/10962/d1006557
- Description: An in vitro permeation cell has been designed and validated for use in monitoring the transmembrane permeation of betamethasone 17-valerate. The design utilizes common laboratory equipment and incorporates as many beneficial features as possible from other designs. The importance of fully validating the hydrodynamic performance of the cell prior to experimentation is stressed. The cell was validated by monitoring the diffusion of betamethasone 17-valerate in isopropyl myristate solution into purified isopropyl myristate receptor phase at different temperatures, different agitation rates and through different synthetic and biological membranes. The results of the hydrodynamic validation agree with data from other researchers and show that the permeation cell is adequately sensitive to these experimental parameters. The results of the membrane evaluation allow appropriate selection of the barrier material for representative transdermal experiments to be conducted. While human and porcine stratum corneum/epidermis are similar in diffusive properties, hairless mouse skin appears to be the most convenient animal membrane for these studies. Although silicone and cellulose membranes appear to be useful in this application, porous filter membranes and egg-shell membranes are insufficiently discriminatory to betamethasone 17-valerate diffusion to provide useful in vitro permeation data.
- Full Text: false
In vitro effects of three organic calcium channel blockers on the rat pineal gland
- Authors: Brown, Clint
- Date: 1992
- Subjects: Calcium -- Antagonists , Pineal gland -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3745 , http://hdl.handle.net/10962/d1003223 , Calcium -- Antagonists , Pineal gland -- Research
- Description: The calcium signal has emerged as an imponant component of intracellular regulation. Pineal function was thought to be slowed by the prominent calcification seen with increasing age, but recently it has been shown that calcium plays a crucial role in the adrenergic regulation of the gland. Beta-adrenoceptor stimulation increases melatonin (aMT) synthesis by increasing the activity of cyclic 3 '-5' adenosine mono phosphate (cAMP). Cyclic-AMP regulates the production of the pineal hormone, melatonin, from serotonin via the rate-limiting enzyme N-acetyltransferase (NAT). Increased intracellular cAMP is essential to the adrenergic induction of NAT. Noradrenaline(NA)also elevates pinealocyte cyclic guanosine monophosphate (cGMP). Adrenergic regulation of these cyclic nucleotides involves both α₁ - and β-adrenoceptors. Beta-adrenoceptor stimulation is an absolute requirement. Alphal-adrenoceptor activation, which is ineffective alone, serves to amplify the β-stimulated cAMP and cGMP responses via a positive effect on a Ca²⁺⁻/ phospholipiddependent protein kinase (Protein kinase-C) and a net influx of Ca²⁺ into the pinealocyte. Previous studies suggest the use of organic calcium channel blockers (CCBs) as probes of calcium-mediated processes. Applying this concept, the study set out to investigate the influence of a representative of each of the structurally diverse groups of calcium channel blockers viz. verapamil, diltiazem and nifedipine, and to examine their effect on β-adrenoceptor stimulation. It used the β-agonist isoprenaline (ISO) and the mixed [α₁/β]agonist noradrenaline (NA), for its combined [α₁/β]adrenoceptor stimulation, on agonist-induced increases in the production of radio-labelled aMT and N-acetylserotonin(aHT) -measured as the sum of N-acetylated product- from [¹⁴C] serotonin. This was done using organ cultures of rat pineal glands. It was speciously assumed that this drug paradigm would allow the determination of Ca²⁺ influx and/or the blocking thereof in the reported potentiation by using ISO as a non Ca²⁺ -entry stimulating agonist, compared with NA and its Ca²⁺ -entry stimulating properties. Surprisingly, all 3 CCB's potentiated the effect of NA. Only diltiazem was found not to potentiate the effect of ISO. In an attempt to uncover the reason for these results, the study moved toward a mechanistic approach,focusing in an antecedent manner on the various steps in the indole metabolic pathway to identify the point at which the change occurred, and hence possibly elucidate the mechanism responsible for the paradoxical increase. Experiments which assayed the levels of NAT, under the same drug conditions, showed the paradoxical increase to be already evident at this stage. Secondary experiments confirmed that NA stimulation of the pineal is dependent on Ca²⁺, both in organ culture and with NAT: the Ca²⁺ chelator EGTA abolished adrenergically-induced stimulation, while Ca²⁺ added after EGTA, restored the enzyme activity. The ionophore A23187 (which is able to transport Ca²⁺ directly into the pinealocyte via a mechanism which differs from the α₁ - mechanism) when used in conjunction with ISO or NA, was able to potentiate the responses of these two agonists relative to control values (agonist-alone), but by itself had no effect. With the enzyme NAT critically dependent upon cAMP for its induction, it was decided to determine the levels of cAMP and then those of its regulator, cAMP-phosphodiesterase (cAMP-PDE). This reasoning was prompted by reports of anti-calmodulin activity shown by the CCBs, in addition to their channel blocking effects. By binding to calmodulin (CaM), the CCBs are reportedly able to inhibit the CaM-dependent activation of cAMP-PDE. Following NA stimulation, verapamil caused a significant decrease in cAMP-PDE levels and an increase in cAMP. The other CCBs showed a similar trend. Glands stimulated with ISO in the presence of verapamil and nifedipine showed no significant differences in cAMP or cAMP-PDE levels. Diltiazem, however, was found to decrease the effect of ISO on cAMP while causing a concomitant increase in cAMP-PDE. This i) supported a possible hypothesis that the observed enhancement is a result of cAMP levels remaining elevated due to an inhibition of cAMP-PDE by the CCEs and ii) pointed to the possible presence of a CaM-sensitive PDE within the rat pineal gland. To test this hypothesis, two drugs which are more specific in their actions on CaM effects were chosen to see if the earlier results could be mimicked and thereby confirmed. Glands stimulated with NA in the presence of the specific CaM inhibitor R 24571 showed increased NAT activity and [¹⁴C]-aMT production. cAMP-PDE levels were clearly down, thus corroborating the possibility of cAMP-PDE inhibition. Glands incubated in the presence of M&B 22948, a CaM-sensitive PDE inhibitor, showed similar increases in NAT activity and [¹⁴C]-aMT. These findings therefore support the initial results and although indirect, confirm the hypothesis that the paradoxical increase following predominantly NA stimulation could be a result of cAMP levels remaining elevated, due to inhibition by the CCEs of the CaM-dependent activation of its regulator cAMP-PDE. In summary, data presented herein concur with proposals that: i) the CCEs are not specific enough to be used as tools to research Ca²⁺ -mediated events, as they appear to have sites of action other than the voltage operated channel (VOC); eg. binding to calmodulin, ii) there are functional differences between the CCEs as shown by diltiazem in this series of experiments, iii) there is a CaM-sensitive-PDE present in the pineal.
- Full Text:
- Authors: Brown, Clint
- Date: 1992
- Subjects: Calcium -- Antagonists , Pineal gland -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3745 , http://hdl.handle.net/10962/d1003223 , Calcium -- Antagonists , Pineal gland -- Research
- Description: The calcium signal has emerged as an imponant component of intracellular regulation. Pineal function was thought to be slowed by the prominent calcification seen with increasing age, but recently it has been shown that calcium plays a crucial role in the adrenergic regulation of the gland. Beta-adrenoceptor stimulation increases melatonin (aMT) synthesis by increasing the activity of cyclic 3 '-5' adenosine mono phosphate (cAMP). Cyclic-AMP regulates the production of the pineal hormone, melatonin, from serotonin via the rate-limiting enzyme N-acetyltransferase (NAT). Increased intracellular cAMP is essential to the adrenergic induction of NAT. Noradrenaline(NA)also elevates pinealocyte cyclic guanosine monophosphate (cGMP). Adrenergic regulation of these cyclic nucleotides involves both α₁ - and β-adrenoceptors. Beta-adrenoceptor stimulation is an absolute requirement. Alphal-adrenoceptor activation, which is ineffective alone, serves to amplify the β-stimulated cAMP and cGMP responses via a positive effect on a Ca²⁺⁻/ phospholipiddependent protein kinase (Protein kinase-C) and a net influx of Ca²⁺ into the pinealocyte. Previous studies suggest the use of organic calcium channel blockers (CCBs) as probes of calcium-mediated processes. Applying this concept, the study set out to investigate the influence of a representative of each of the structurally diverse groups of calcium channel blockers viz. verapamil, diltiazem and nifedipine, and to examine their effect on β-adrenoceptor stimulation. It used the β-agonist isoprenaline (ISO) and the mixed [α₁/β]agonist noradrenaline (NA), for its combined [α₁/β]adrenoceptor stimulation, on agonist-induced increases in the production of radio-labelled aMT and N-acetylserotonin(aHT) -measured as the sum of N-acetylated product- from [¹⁴C] serotonin. This was done using organ cultures of rat pineal glands. It was speciously assumed that this drug paradigm would allow the determination of Ca²⁺ influx and/or the blocking thereof in the reported potentiation by using ISO as a non Ca²⁺ -entry stimulating agonist, compared with NA and its Ca²⁺ -entry stimulating properties. Surprisingly, all 3 CCB's potentiated the effect of NA. Only diltiazem was found not to potentiate the effect of ISO. In an attempt to uncover the reason for these results, the study moved toward a mechanistic approach,focusing in an antecedent manner on the various steps in the indole metabolic pathway to identify the point at which the change occurred, and hence possibly elucidate the mechanism responsible for the paradoxical increase. Experiments which assayed the levels of NAT, under the same drug conditions, showed the paradoxical increase to be already evident at this stage. Secondary experiments confirmed that NA stimulation of the pineal is dependent on Ca²⁺, both in organ culture and with NAT: the Ca²⁺ chelator EGTA abolished adrenergically-induced stimulation, while Ca²⁺ added after EGTA, restored the enzyme activity. The ionophore A23187 (which is able to transport Ca²⁺ directly into the pinealocyte via a mechanism which differs from the α₁ - mechanism) when used in conjunction with ISO or NA, was able to potentiate the responses of these two agonists relative to control values (agonist-alone), but by itself had no effect. With the enzyme NAT critically dependent upon cAMP for its induction, it was decided to determine the levels of cAMP and then those of its regulator, cAMP-phosphodiesterase (cAMP-PDE). This reasoning was prompted by reports of anti-calmodulin activity shown by the CCBs, in addition to their channel blocking effects. By binding to calmodulin (CaM), the CCBs are reportedly able to inhibit the CaM-dependent activation of cAMP-PDE. Following NA stimulation, verapamil caused a significant decrease in cAMP-PDE levels and an increase in cAMP. The other CCBs showed a similar trend. Glands stimulated with ISO in the presence of verapamil and nifedipine showed no significant differences in cAMP or cAMP-PDE levels. Diltiazem, however, was found to decrease the effect of ISO on cAMP while causing a concomitant increase in cAMP-PDE. This i) supported a possible hypothesis that the observed enhancement is a result of cAMP levels remaining elevated due to an inhibition of cAMP-PDE by the CCEs and ii) pointed to the possible presence of a CaM-sensitive PDE within the rat pineal gland. To test this hypothesis, two drugs which are more specific in their actions on CaM effects were chosen to see if the earlier results could be mimicked and thereby confirmed. Glands stimulated with NA in the presence of the specific CaM inhibitor R 24571 showed increased NAT activity and [¹⁴C]-aMT production. cAMP-PDE levels were clearly down, thus corroborating the possibility of cAMP-PDE inhibition. Glands incubated in the presence of M&B 22948, a CaM-sensitive PDE inhibitor, showed similar increases in NAT activity and [¹⁴C]-aMT. These findings therefore support the initial results and although indirect, confirm the hypothesis that the paradoxical increase following predominantly NA stimulation could be a result of cAMP levels remaining elevated, due to inhibition by the CCEs of the CaM-dependent activation of its regulator cAMP-PDE. In summary, data presented herein concur with proposals that: i) the CCEs are not specific enough to be used as tools to research Ca²⁺ -mediated events, as they appear to have sites of action other than the voltage operated channel (VOC); eg. binding to calmodulin, ii) there are functional differences between the CCEs as shown by diltiazem in this series of experiments, iii) there is a CaM-sensitive-PDE present in the pineal.
- Full Text:
Industrial social work : an exploration and an assessment of the practice of social work in industry in South Africa
- Authors: Rankin, Pedro
- Date: 1992
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3279 , http://hdl.handle.net/10962/d1006474
- Description: Industries in South Africa have been employing social workers in increasing numbers during the last decade, and in several of the bigger industries social work seem to have succeeded in establishing itself over the course of time. Certain forces seem to be operating in both industry and social work which could facilitate the introduction and development of industrial social work as a specialised field of practice in South Africa. Very significant variables in this regard are a rapidly changing labour force, and certain socio-political developments in South Africa, that took place especially during the last decade, and in particular during the past two years. A lack of knowledge about the practice of social work in industry exists in South Africa, mainly as a result of a general lack of empirical research into this field. The main purpose of this research project was to add to the knowledge about the nature of industrial social work practice in South Africa, and to contribute to an understanding of the forces influencing its development. In order to achieve this overall purpose, an extensive review of the existing literature was done with the aim of identifying and describing the present trends and issues in industrial social work thinking. This was combined with an empirical investigation into the practice of social workers presently employed in industry in South Africa. In addition to this, the attitude of industries not employing social workers was established with a view of determining factors influencing the further development of industrial social work. A third component of the empirical investigation consisted of a survey of the attitudes and knowledge of community welfare organisations regarding industrial social work practice. This was done in an effort to establish the amount of support for industrial social work from the rest of the profession. The findings of the empirical investigation indicated an emphasis on the individual employee as far as the practice of industrial social work is concerned - an EAP model thus. Industries not employing social workers still seem to need more education as far as the true nature of social work practice is concerned, and there seem to be a reserved acceptance of industrial social work practice amongst community welfare organisations, as well as a lack of knowledge. In conclusion it can be stated that the social work fraternity in South Africa should take more serious notice of occupational social work practice in South Africa in general, and of industrial social work practice in particular, mainly because of its importance to the worker.
- Full Text:
- Authors: Rankin, Pedro
- Date: 1992
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3279 , http://hdl.handle.net/10962/d1006474
- Description: Industries in South Africa have been employing social workers in increasing numbers during the last decade, and in several of the bigger industries social work seem to have succeeded in establishing itself over the course of time. Certain forces seem to be operating in both industry and social work which could facilitate the introduction and development of industrial social work as a specialised field of practice in South Africa. Very significant variables in this regard are a rapidly changing labour force, and certain socio-political developments in South Africa, that took place especially during the last decade, and in particular during the past two years. A lack of knowledge about the practice of social work in industry exists in South Africa, mainly as a result of a general lack of empirical research into this field. The main purpose of this research project was to add to the knowledge about the nature of industrial social work practice in South Africa, and to contribute to an understanding of the forces influencing its development. In order to achieve this overall purpose, an extensive review of the existing literature was done with the aim of identifying and describing the present trends and issues in industrial social work thinking. This was combined with an empirical investigation into the practice of social workers presently employed in industry in South Africa. In addition to this, the attitude of industries not employing social workers was established with a view of determining factors influencing the further development of industrial social work. A third component of the empirical investigation consisted of a survey of the attitudes and knowledge of community welfare organisations regarding industrial social work practice. This was done in an effort to establish the amount of support for industrial social work from the rest of the profession. The findings of the empirical investigation indicated an emphasis on the individual employee as far as the practice of industrial social work is concerned - an EAP model thus. Industries not employing social workers still seem to need more education as far as the true nature of social work practice is concerned, and there seem to be a reserved acceptance of industrial social work practice amongst community welfare organisations, as well as a lack of knowledge. In conclusion it can be stated that the social work fraternity in South Africa should take more serious notice of occupational social work practice in South Africa in general, and of industrial social work practice in particular, mainly because of its importance to the worker.
- Full Text:
Influence of the oil phase dispersion in a cream base on the in vivo release of betamethasone 17-valerate
- Haigh, J M, Smith, E W, Meyer, E, Fassihi, A R
- Authors: Haigh, J M , Smith, E W , Meyer, E , Fassihi, A R
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6365 , http://hdl.handle.net/10962/d1006065
- Description: Release of betamethasone valerate (betamethasone 17-valerate) from 3 extemporaneous cream formulations (1 control, 1 containing propylene glycol, and 1 containing \b/-cyclodextrin) and a commercial cream formulation (Betnovate) was compared using the human skin blanching assay in 12 healthy male volunteers. All 3 extemporaneous formulations showed similar drug release rates, equivalent to or better than the commercial preparation containing betamethasone in a 10 fold higher concentration. Electron microscopic examination showed considerably finer dispersion of the oil phase in the extemporaneous formulations. It was concluded that the increased surface area available for partitioning of betamethasone between the cream and the skin is responsible for the improved topical availability of the drug from the extemporaneous formulations.
- Full Text: false
- Authors: Haigh, J M , Smith, E W , Meyer, E , Fassihi, A R
- Date: 1992
- Language: English
- Type: Article
- Identifier: vital:6365 , http://hdl.handle.net/10962/d1006065
- Description: Release of betamethasone valerate (betamethasone 17-valerate) from 3 extemporaneous cream formulations (1 control, 1 containing propylene glycol, and 1 containing \b/-cyclodextrin) and a commercial cream formulation (Betnovate) was compared using the human skin blanching assay in 12 healthy male volunteers. All 3 extemporaneous formulations showed similar drug release rates, equivalent to or better than the commercial preparation containing betamethasone in a 10 fold higher concentration. Electron microscopic examination showed considerably finer dispersion of the oil phase in the extemporaneous formulations. It was concluded that the increased surface area available for partitioning of betamethasone between the cream and the skin is responsible for the improved topical availability of the drug from the extemporaneous formulations.
- Full Text: false
Interaction of selected fungicides with insoluble bovine skin collagen in the presence of the non ionic surfactant Triton X-100
- Authors: Fowler, William Mackenzie
- Date: 1992
- Subjects: Collagenases -- Research Fungicides -- Research Hides and skins -- Preservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4318 , http://hdl.handle.net/10962/d1004976
- Description: In the leather industry fungicides are often used for the protection of wet-blue leather. These fungicides are usually only sparingly soluble and are therefore formulated together with surfactants in order to increase their solubility and to ensure an even distribution over the surface of the hide after treatment. Solutions containing both fungicides and surfactant are complex. The nature of these solutions was investigated. By means of UV/Vis spectroscopy and viscometry it was shown that the surfactant and fungicides form micelles and mixed micelles in solution. The nature of these micelles and mixed micelles was dependent on the solution temperature as well as on the concentrations of the surfactant and fungicides. At the higher temperatures and concentrations transition to large, possibly rod-shaped, mixed micelles occurred. The interaction between the selected fungicides 2-(thiocyanomethylthio)benzothiazole and n-octyl-4-isothiazol-3-one with bovine skin collagen in the form of both limed and lightly chromed hide powder in the presence of the non ionic surfactant Triton X -100 was investigated. Fungicide uptake was determined by difference measurements on the float solutions at regular intervals during treatment. Binding was rapid with equilibrium being established within the first six hours even for the solutions with the highest surfactant concentration. Binding failed to follow a normal mass-action binding-type isotherm approaching a saturation limit, but increased continuously indicating a co-operative effect whereby binding site affinity actually increased with the amount of ligand bound. Binding was accompanied by a drop in the free surfactant in the solution at the higher biocide levels indicating the formation of complex mixed micelles which bind to the collagen fibres. The uptake and antifungal activity of commercial fomulations of the fungicides on chrome-tanned wet-blue leather was investigated at various treatment temperatures. At lower fungicide treatment concentrations, binding tended to follow a typical mass-action type binding isotherm, increasing slightly with temperature. At higher float concentrations, an inflexion point was apparent beyond which uptake showed a marked increase with concentration. This inflexion point, signifying a change in binding characteristics, occurred at progressively lower concentrations with increasing temperature. Antifungal activity in terms of storage periods to onset of fungal growth was determined on the wet-blue leather cuttings immediately after treatment and drainage and also on sample discs after exhaustive extraction of free fungicide using dichloromethane. Storage performance testing of the various treated wet-blue leathers was carried out by different methods. Residual protective periods showed a curvilinear increase with dosage offer and surface uptake. In the low dosage range treatment temperature had only a relatively slight effect in promoting uptake and improving storage protection. At higher dosages, the influence of temperature on uptake and storage protection was greater due to the increase in surface binding of the fungicides at the elevated temperatures. Only a portion of the fungicide uptake was recovered by direct solvent extraction of the treated wet-blue leather. Solvent extraction reduced storage margins. The storage response in relation to fungicide content was, however comparable after extraction, indicating that both irreversibly bound and physically associated fungicide offered effective protection. Results of the study provide further insight into the mode of interaction of fungicide emulsion dispersion with bovine skin collagen, and the importance of the emulsion dispersions and its stability in determining the uptake of fungicide.
- Full Text:
- Authors: Fowler, William Mackenzie
- Date: 1992
- Subjects: Collagenases -- Research Fungicides -- Research Hides and skins -- Preservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4318 , http://hdl.handle.net/10962/d1004976
- Description: In the leather industry fungicides are often used for the protection of wet-blue leather. These fungicides are usually only sparingly soluble and are therefore formulated together with surfactants in order to increase their solubility and to ensure an even distribution over the surface of the hide after treatment. Solutions containing both fungicides and surfactant are complex. The nature of these solutions was investigated. By means of UV/Vis spectroscopy and viscometry it was shown that the surfactant and fungicides form micelles and mixed micelles in solution. The nature of these micelles and mixed micelles was dependent on the solution temperature as well as on the concentrations of the surfactant and fungicides. At the higher temperatures and concentrations transition to large, possibly rod-shaped, mixed micelles occurred. The interaction between the selected fungicides 2-(thiocyanomethylthio)benzothiazole and n-octyl-4-isothiazol-3-one with bovine skin collagen in the form of both limed and lightly chromed hide powder in the presence of the non ionic surfactant Triton X -100 was investigated. Fungicide uptake was determined by difference measurements on the float solutions at regular intervals during treatment. Binding was rapid with equilibrium being established within the first six hours even for the solutions with the highest surfactant concentration. Binding failed to follow a normal mass-action binding-type isotherm approaching a saturation limit, but increased continuously indicating a co-operative effect whereby binding site affinity actually increased with the amount of ligand bound. Binding was accompanied by a drop in the free surfactant in the solution at the higher biocide levels indicating the formation of complex mixed micelles which bind to the collagen fibres. The uptake and antifungal activity of commercial fomulations of the fungicides on chrome-tanned wet-blue leather was investigated at various treatment temperatures. At lower fungicide treatment concentrations, binding tended to follow a typical mass-action type binding isotherm, increasing slightly with temperature. At higher float concentrations, an inflexion point was apparent beyond which uptake showed a marked increase with concentration. This inflexion point, signifying a change in binding characteristics, occurred at progressively lower concentrations with increasing temperature. Antifungal activity in terms of storage periods to onset of fungal growth was determined on the wet-blue leather cuttings immediately after treatment and drainage and also on sample discs after exhaustive extraction of free fungicide using dichloromethane. Storage performance testing of the various treated wet-blue leathers was carried out by different methods. Residual protective periods showed a curvilinear increase with dosage offer and surface uptake. In the low dosage range treatment temperature had only a relatively slight effect in promoting uptake and improving storage protection. At higher dosages, the influence of temperature on uptake and storage protection was greater due to the increase in surface binding of the fungicides at the elevated temperatures. Only a portion of the fungicide uptake was recovered by direct solvent extraction of the treated wet-blue leather. Solvent extraction reduced storage margins. The storage response in relation to fungicide content was, however comparable after extraction, indicating that both irreversibly bound and physically associated fungicide offered effective protection. Results of the study provide further insight into the mode of interaction of fungicide emulsion dispersion with bovine skin collagen, and the importance of the emulsion dispersions and its stability in determining the uptake of fungicide.
- Full Text:
Intersolid pyrotechnic reactions of silicon
- Authors: Rugunanan, Rajan Anil
- Date: 1992
- Subjects: Thermochemistry , Thermal analysis , Chemistry, Analytic , Chemistry, Organic , Silicon
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4527 , http://hdl.handle.net/10962/d1015571
- Description: A study of the role of different oxidants with silicon as the fuel in simple binary pyrotechnic compositions is reported. Several oxidants were examined, but only three (Sb₂0₃, Fe₂0₃ and Sn0₂) satisfied the restrictions that the combustion temperatures should be below the melting point of platinum/rhodium thermocouples (1760°C), that burning rates should not exceed the response of the thermocouples, and that burning should occur without significant mass-transport. A fourth oxidant, KN0₃, was selected on account of its low melting point and general importance as a pyrotechnic oxidant. The oxidation of silicon in the presence of either Sb₂0₃ or KN0₃ could be identified from thermal analysis curves. No thermal events were noted when Si/Sn0₂ and SiFe₂0₃ compositions were heated under similar conditions. The oxidation of Si powder in oxygen was also studied. All four binary systems sustained burning over a reasonably wide range of compositions. The range of burning rates measured (2 to 35 mm s⁻¹) depended on the oxidant used. Fe₂0₃ and Sb₂0₃ gave slow burning mixtures compared to Sn0₂ and to KN0₃ compositions with a high Si content. Burning rates generally increased with increasing specific surface area of silicon, but decreased in the presence of inert diluents and moisture. The burning rates of the Si/Fe₂0₃ and Si/Sn0₂ systems increased with increasing compaction of the samples. Kinetic parameters derived from the temperature proftles recorded during combustion were generally low (6 to 37 kJ mol⁻¹). This is in keeping with proposals that burning is diffusion controlled. The values of kinetic parameters derived from thermal analysis curves were considerably greater ( > 250 kJ mol⁻¹). Two other fuels, FeSi₇ and CaSi₂, gave similar thermal analysis curves when used instead of silicon. There were considerable differences in the burning rates for binary mixtures of these fuels compared to silicon. Ternary systems with two fuels or two oxidants showed that only limited interaction occurs during thermal analysis. The use of a second fuel or oxidant did, however, modify the burning behaviour considerably. Other techniques used in this study to probe the details of the reaction processes included bomb calorimetry, measurement of thermal conductivities, infrared spectroscopy, X-ray diffraction and scanning electron micoscropy.
- Full Text:
- Authors: Rugunanan, Rajan Anil
- Date: 1992
- Subjects: Thermochemistry , Thermal analysis , Chemistry, Analytic , Chemistry, Organic , Silicon
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4527 , http://hdl.handle.net/10962/d1015571
- Description: A study of the role of different oxidants with silicon as the fuel in simple binary pyrotechnic compositions is reported. Several oxidants were examined, but only three (Sb₂0₃, Fe₂0₃ and Sn0₂) satisfied the restrictions that the combustion temperatures should be below the melting point of platinum/rhodium thermocouples (1760°C), that burning rates should not exceed the response of the thermocouples, and that burning should occur without significant mass-transport. A fourth oxidant, KN0₃, was selected on account of its low melting point and general importance as a pyrotechnic oxidant. The oxidation of silicon in the presence of either Sb₂0₃ or KN0₃ could be identified from thermal analysis curves. No thermal events were noted when Si/Sn0₂ and SiFe₂0₃ compositions were heated under similar conditions. The oxidation of Si powder in oxygen was also studied. All four binary systems sustained burning over a reasonably wide range of compositions. The range of burning rates measured (2 to 35 mm s⁻¹) depended on the oxidant used. Fe₂0₃ and Sb₂0₃ gave slow burning mixtures compared to Sn0₂ and to KN0₃ compositions with a high Si content. Burning rates generally increased with increasing specific surface area of silicon, but decreased in the presence of inert diluents and moisture. The burning rates of the Si/Fe₂0₃ and Si/Sn0₂ systems increased with increasing compaction of the samples. Kinetic parameters derived from the temperature proftles recorded during combustion were generally low (6 to 37 kJ mol⁻¹). This is in keeping with proposals that burning is diffusion controlled. The values of kinetic parameters derived from thermal analysis curves were considerably greater ( > 250 kJ mol⁻¹). Two other fuels, FeSi₇ and CaSi₂, gave similar thermal analysis curves when used instead of silicon. There were considerable differences in the burning rates for binary mixtures of these fuels compared to silicon. Ternary systems with two fuels or two oxidants showed that only limited interaction occurs during thermal analysis. The use of a second fuel or oxidant did, however, modify the burning behaviour considerably. Other techniques used in this study to probe the details of the reaction processes included bomb calorimetry, measurement of thermal conductivities, infrared spectroscopy, X-ray diffraction and scanning electron micoscropy.
- Full Text:
Introduction and extinction of brown trout (Salmo trutta L.) in an impoverished subantarctic stream
- Cooper, J, Crafford, J E, Hecht, Thomas
- Authors: Cooper, J , Crafford, J E , Hecht, Thomas
- Date: 1992
- Subjects: Anadromous fishes -- Marion Island
- Language: English
- Type: Article
- Identifier: vital:6767 , http://hdl.handle.net/10962/d1008044
- Description: Brown trout were introduced to the Van den Boogaard River on subantarctic Marion Island in 1964, and a small population became established. The last individual was seen in 1984, and the species is now considered to be extinct on the island. Their diet was exclusively allochthonous, with snails and spiders predominating. Ages estimated at six to eleven years showed that spawning must have occurred since the original introduction. Since the Van den Boogaard River enters the sea via a waterfall, it is postulated that trout were not able to practice an anadromous life-style, and that this, as well as other factors connected with the impoverished nature of the stream, led to dwarfing of the resident population. No further introductions of alien fish to Marion Island should be contemplated.
- Full Text:
- Authors: Cooper, J , Crafford, J E , Hecht, Thomas
- Date: 1992
- Subjects: Anadromous fishes -- Marion Island
- Language: English
- Type: Article
- Identifier: vital:6767 , http://hdl.handle.net/10962/d1008044
- Description: Brown trout were introduced to the Van den Boogaard River on subantarctic Marion Island in 1964, and a small population became established. The last individual was seen in 1984, and the species is now considered to be extinct on the island. Their diet was exclusively allochthonous, with snails and spiders predominating. Ages estimated at six to eleven years showed that spawning must have occurred since the original introduction. Since the Van den Boogaard River enters the sea via a waterfall, it is postulated that trout were not able to practice an anadromous life-style, and that this, as well as other factors connected with the impoverished nature of the stream, led to dwarfing of the resident population. No further introductions of alien fish to Marion Island should be contemplated.
- Full Text:
Local responses to political policies and socio-economic change in the Keiskammahoek district, Ciskei: anthropological perspectives
- de Wet, Christopher J, Manona, Cecil W, Palmer, Robin C G
- Authors: de Wet, Christopher J , Manona, Cecil W , Palmer, Robin C G
- Date: 1992
- Subjects: Burnshill -- Economic conditions Burnshill -- Social conditions Gymnothorax -- Economic conditions Gymnothorax -- Social conditions Land tenure -- South Africa -- Ciskei Keiskammahoek (South Africa) -- Economic conditions Keiskammahoek (South Africa) -- Social conditions
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/1810 , vital:20229 , ISBN 086810230x
- Description: This report relates to research done in the Keiskammahoek district of the Ciskei (see Map No. l) during 1989 and early 1990, with the financial support of the Programme for Development Research (PRODDER) of the Human Sciences Research Council (HSRC) of South Africa. The project was designed and conducted against the background of previous research, and has served as a pilot project for a larger project, entitled "Socio- Economic Change and Development Planning in the Keiskammahoek District of the Ciskei". This larger project which is currently in progress, (and which has been funded by the Institute for Research Development of the HSRC, by the Chairman's Fund of Anglo-American and De Beers, and by Johannesburg Consolidated Investments Co Ltd), is intended to give rise to a process of consultation and planning, leading to various local-level development initiatives in the District. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Authors: de Wet, Christopher J , Manona, Cecil W , Palmer, Robin C G
- Date: 1992
- Subjects: Burnshill -- Economic conditions Burnshill -- Social conditions Gymnothorax -- Economic conditions Gymnothorax -- Social conditions Land tenure -- South Africa -- Ciskei Keiskammahoek (South Africa) -- Economic conditions Keiskammahoek (South Africa) -- Social conditions
- Language: English
- Type: book , text
- Identifier: http://hdl.handle.net/10962/1810 , vital:20229 , ISBN 086810230x
- Description: This report relates to research done in the Keiskammahoek district of the Ciskei (see Map No. l) during 1989 and early 1990, with the financial support of the Programme for Development Research (PRODDER) of the Human Sciences Research Council (HSRC) of South Africa. The project was designed and conducted against the background of previous research, and has served as a pilot project for a larger project, entitled "Socio- Economic Change and Development Planning in the Keiskammahoek District of the Ciskei". This larger project which is currently in progress, (and which has been funded by the Institute for Research Development of the HSRC, by the Chairman's Fund of Anglo-American and De Beers, and by Johannesburg Consolidated Investments Co Ltd), is intended to give rise to a process of consultation and planning, leading to various local-level development initiatives in the District. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
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Making pupils think: the development of a microcomputer-inspired adaptation of the Standard 7 mathematics curriculum
- Authors: Norman, Maxie
- Date: 1992
- Subjects: Mathematics -- Study and teaching (Secondary) -- Data processing Computer-assisted instruction
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1667 , http://hdl.handle.net/10962/d1003550
- Description: This half-thesis gives an overview of the influence of the microcomputer on the way in which mathematics is done, taught and learnt. The nature of mathematics and the nature of the tutor, tool and tutee modes of microcomputer usage are discussed as background. A case is made for the use of action research methods and a classroom-based curriculum development model to facilitate innovation and the integration of the microcomputer into the mathematics classroom. A curriculum development cycle of situation analysis. planning, trial and evaluation is advocated. This approach is used to develop a microcomputer-based course aimed at enhancing the reasoning skills of standard 7 pupils. Pupils, working in groups of three, interact with the PROLOG system to build up databases of facts and rules. The microcomputer is used in tutee mode. In "teaching" this tutee, pupils discover the need for formal language and logical reasoning. Active learning is promoted by pupils' interaction with the PROLOG system and by discussions within groups. In this environment the teacher becomes a consultant and constructive critic rather than a lecturer. Findings suggest that the microcomputer plays an important role in terms of pupil motivation and that the microcomputer-based course enables pupils to experience formal language usage and logical reasoning·as relevant activities. Pupil databases provide evidence of the pupils' ability to make appropriate use of rules and to distinguish between and-conditions and or-conditions. The objective of making pupils think was largely achieved. It is recommended that the course be incorporated in the standard 1 or standard 8 curriculum to complement or replace parts of the Euclidean geometry sections as a vehicle for developing logical reasoning skills. Suggestions for the further use of the microcomputer as an investigative tool in mathematics classes and for further microcomputer-inspired courses are also made. The provision of appropriate training to enable teachers to make effective and innovative use of the microcomputer in mathematics lessons is advocated.
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- Authors: Norman, Maxie
- Date: 1992
- Subjects: Mathematics -- Study and teaching (Secondary) -- Data processing Computer-assisted instruction
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1667 , http://hdl.handle.net/10962/d1003550
- Description: This half-thesis gives an overview of the influence of the microcomputer on the way in which mathematics is done, taught and learnt. The nature of mathematics and the nature of the tutor, tool and tutee modes of microcomputer usage are discussed as background. A case is made for the use of action research methods and a classroom-based curriculum development model to facilitate innovation and the integration of the microcomputer into the mathematics classroom. A curriculum development cycle of situation analysis. planning, trial and evaluation is advocated. This approach is used to develop a microcomputer-based course aimed at enhancing the reasoning skills of standard 7 pupils. Pupils, working in groups of three, interact with the PROLOG system to build up databases of facts and rules. The microcomputer is used in tutee mode. In "teaching" this tutee, pupils discover the need for formal language and logical reasoning. Active learning is promoted by pupils' interaction with the PROLOG system and by discussions within groups. In this environment the teacher becomes a consultant and constructive critic rather than a lecturer. Findings suggest that the microcomputer plays an important role in terms of pupil motivation and that the microcomputer-based course enables pupils to experience formal language usage and logical reasoning·as relevant activities. Pupil databases provide evidence of the pupils' ability to make appropriate use of rules and to distinguish between and-conditions and or-conditions. The objective of making pupils think was largely achieved. It is recommended that the course be incorporated in the standard 1 or standard 8 curriculum to complement or replace parts of the Euclidean geometry sections as a vehicle for developing logical reasoning skills. Suggestions for the further use of the microcomputer as an investigative tool in mathematics classes and for further microcomputer-inspired courses are also made. The provision of appropriate training to enable teachers to make effective and innovative use of the microcomputer in mathematics lessons is advocated.
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Managing historical primary and secondary sources : a study of the efficacy of a teaching handbook prepared for first-year Vista University students
- Authors: Watson, Kelvin Innes
- Date: 1992
- Subjects: History -- Study and teaching (Secondary) -- South Africa History -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1670 , http://hdl.handle.net/10962/d1003553
- Description: This study examines the teaching of primary and secondary sources in history at secondary and tertiary level. The various methods used to teach these aspects of the nature of history are compared to the Vista University teaching model. To establish the effectiveness of the vista Block A module for HIS100 students, two test instruments were devised to assess their skills in handling primary and secondary sources. Their skills in identifying relevant points from a passage of historical prose were also tested. A number of statistical techniques were applied to the data from the test instruments. This data was analysed in qualitative and quantitative terms. The results of this analysis suggested that students would probably benefit from a skills-orientated approach to studying history. On the basis of this study, it is recommended that the existing Vista teaching model be revised or amended so that a more effective method of teaching students about the nature of historical sources can be introduced.
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- Authors: Watson, Kelvin Innes
- Date: 1992
- Subjects: History -- Study and teaching (Secondary) -- South Africa History -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1670 , http://hdl.handle.net/10962/d1003553
- Description: This study examines the teaching of primary and secondary sources in history at secondary and tertiary level. The various methods used to teach these aspects of the nature of history are compared to the Vista University teaching model. To establish the effectiveness of the vista Block A module for HIS100 students, two test instruments were devised to assess their skills in handling primary and secondary sources. Their skills in identifying relevant points from a passage of historical prose were also tested. A number of statistical techniques were applied to the data from the test instruments. This data was analysed in qualitative and quantitative terms. The results of this analysis suggested that students would probably benefit from a skills-orientated approach to studying history. On the basis of this study, it is recommended that the existing Vista teaching model be revised or amended so that a more effective method of teaching students about the nature of historical sources can be introduced.
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Namibia's long road to independence : the Botha era
- Authors: Ruiters, Michele René
- Date: 1992
- Subjects: United Nations -- Namibia , Namibia -- History -- 1946-1990 , Namibia -- Politics and government -- 1946-1990
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:2754 , http://hdl.handle.net/10962/d1002001
- Description: This thesis deals with the ten years preceding Namibia's independence in March 1990. It examines the various characters and groups in this process, and how their roles delayed or promoted it. The era of Pieter W. Botha is very significant in that his rule brought many changes to the decision-making process and content of South African foreign policy. This period, 1978 - 1989, marked the formulation of the Total National Strategy in response to the Total Onslaught being waged on South Africa by perceived hostile external forces. Namibia's transition to independence suffered under this military-oriented policy as did the rest of the region. Never before in South Africa's policy-making history had the security sector played such a major role. Regional relations changed subsequent to the policy changes because of the distorted vision the Botha regime had of black-ruled states. Namibia was seen as an important pawn in the Total National Strategy as the last buffer state in Southern Africa protecting South Africa's white minority regime
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- Authors: Ruiters, Michele René
- Date: 1992
- Subjects: United Nations -- Namibia , Namibia -- History -- 1946-1990 , Namibia -- Politics and government -- 1946-1990
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:2754 , http://hdl.handle.net/10962/d1002001
- Description: This thesis deals with the ten years preceding Namibia's independence in March 1990. It examines the various characters and groups in this process, and how their roles delayed or promoted it. The era of Pieter W. Botha is very significant in that his rule brought many changes to the decision-making process and content of South African foreign policy. This period, 1978 - 1989, marked the formulation of the Total National Strategy in response to the Total Onslaught being waged on South Africa by perceived hostile external forces. Namibia's transition to independence suffered under this military-oriented policy as did the rest of the region. Never before in South Africa's policy-making history had the security sector played such a major role. Regional relations changed subsequent to the policy changes because of the distorted vision the Botha regime had of black-ruled states. Namibia was seen as an important pawn in the Total National Strategy as the last buffer state in Southern Africa protecting South Africa's white minority regime
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Neuropharmacological interactions in the rat pineal gland a study of antidepressant drugs
- Authors: Banoo, Shabir
- Date: 1992
- Subjects: Antidepressants -- Research , Pineal gland -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3744 , http://hdl.handle.net/10962/d1003222 , Antidepressants -- Research , Pineal gland -- Research
- Description: The rat pineal gland provides a convenient model for investigating nor adrenergic receptor neurotransmission and the effects of various drugs on these processes in health and disease. The effect of a variety of antidepressant drugs on rat pineal gland function following acute and chronic administration is described. Antidepressants from several different classes increase melatonin synthesis in rat pineal gland cultures when administered acutely. This effect appears to be mediated by noradrenaline acting on postsynaptic β-adrenoceptors. Activation of these receptors, in turn, activates the enzyme serotonin N-acetyltransferase via a cyclic adenosine monophosphate (cAMP) second messenger system. Serotonin N-acetyltransferase catalyses the rate-limiting conversion of serotonin to melatonin. Blockade of postsynaptic β-adrenoceptors prevents the antidepressant-induced increase in melatonin synthesis. The possibility that atypical antidepressants as well as those that selectively inhibit serotonin reuptake may increase melatonin synthesis via a β-adrenoceptor mechanism is discussed. In contrast, however, antidepressants from different classes have variable effects on rat pineal gland function when administered repeatedly. Chronic treatment with antidepressants that selectively inhibit noradrenaline reuptake appear to down-regulate the β-adrenoceptor system while, simultaneously, increasing melatonin output. Atypical antidepressants and those that selectively inhibit serotonin reuptake appear to be without these effects when administered repeatedly. The pineal gland of normal rats may therefore not represent a suitable model for evaluating the biochemical effects of chronic antidepressant treatment. In an attempt to investigatc pineal gland function in rats with "model depression" , antidepressants were administered to chronically reserpinized rats. Treatment with reserpine produced an increase in the density of pineal β-adrenoceptors. In addition, pineal cyclic AMP accumulation and N-acetyltransferase activity were increased in reserpinized rats following exogenous catecholamine stimulation. Reserpine, by depleting intraneuronal catecholamine stores, prevented the nocturnal induction of N-acetyltransferase activity and reduced the synthesis of melatonin in pineal gland cultures. A variety of antidepressants, irrespective of their acute pharmacological actions, reversed these effects when administered chronically to resepinized rats. Acute antidepressant administration was not associated with a reversal of the reserpine-induced effects. These findings provide additional evidence against the hypothesis that antidepressant drugs act by reducing noradrenergic neurotransmission and casts doubt on the importance of β-adrenoceptor down-regulation in the mechanism of antidepressant action. The possibility that the pineal gland of the reserpinized rat may represent an alternative model for evaluating antidepressant therapies is discussed.
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- Authors: Banoo, Shabir
- Date: 1992
- Subjects: Antidepressants -- Research , Pineal gland -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3744 , http://hdl.handle.net/10962/d1003222 , Antidepressants -- Research , Pineal gland -- Research
- Description: The rat pineal gland provides a convenient model for investigating nor adrenergic receptor neurotransmission and the effects of various drugs on these processes in health and disease. The effect of a variety of antidepressant drugs on rat pineal gland function following acute and chronic administration is described. Antidepressants from several different classes increase melatonin synthesis in rat pineal gland cultures when administered acutely. This effect appears to be mediated by noradrenaline acting on postsynaptic β-adrenoceptors. Activation of these receptors, in turn, activates the enzyme serotonin N-acetyltransferase via a cyclic adenosine monophosphate (cAMP) second messenger system. Serotonin N-acetyltransferase catalyses the rate-limiting conversion of serotonin to melatonin. Blockade of postsynaptic β-adrenoceptors prevents the antidepressant-induced increase in melatonin synthesis. The possibility that atypical antidepressants as well as those that selectively inhibit serotonin reuptake may increase melatonin synthesis via a β-adrenoceptor mechanism is discussed. In contrast, however, antidepressants from different classes have variable effects on rat pineal gland function when administered repeatedly. Chronic treatment with antidepressants that selectively inhibit noradrenaline reuptake appear to down-regulate the β-adrenoceptor system while, simultaneously, increasing melatonin output. Atypical antidepressants and those that selectively inhibit serotonin reuptake appear to be without these effects when administered repeatedly. The pineal gland of normal rats may therefore not represent a suitable model for evaluating the biochemical effects of chronic antidepressant treatment. In an attempt to investigatc pineal gland function in rats with "model depression" , antidepressants were administered to chronically reserpinized rats. Treatment with reserpine produced an increase in the density of pineal β-adrenoceptors. In addition, pineal cyclic AMP accumulation and N-acetyltransferase activity were increased in reserpinized rats following exogenous catecholamine stimulation. Reserpine, by depleting intraneuronal catecholamine stores, prevented the nocturnal induction of N-acetyltransferase activity and reduced the synthesis of melatonin in pineal gland cultures. A variety of antidepressants, irrespective of their acute pharmacological actions, reversed these effects when administered chronically to resepinized rats. Acute antidepressant administration was not associated with a reversal of the reserpine-induced effects. These findings provide additional evidence against the hypothesis that antidepressant drugs act by reducing noradrenergic neurotransmission and casts doubt on the importance of β-adrenoceptor down-regulation in the mechanism of antidepressant action. The possibility that the pineal gland of the reserpinized rat may represent an alternative model for evaluating antidepressant therapies is discussed.
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Nickel sulphide mineralization associated with Archean komatiites
- Authors: Lane, Monica Leonie
- Date: 1992
- Subjects: Nickel sulfide , Geology, Stratigraphic -- Archaean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4982 , http://hdl.handle.net/10962/d1005594 , Nickel sulfide , Geology, Stratigraphic -- Archaean
- Description: The distribution of Archean Nickel sulphide deposits reflects tectonic controls operating during the evolution of the granitoid greenstone terrains. Important deposits of komatiitic-affinity are concentrated within, and adjacent to, younger (∼2.7 Ga), rift-related greenstone belts (e.g. Canada, Western Australia and Zimababwe). Two important classes of Archean Nickel sulphide deposits exist, formerly known as "Dunitic" and "Peridotitic", these are now referred to as Group I and Group II deposits, based on their characteristic structure and composition. Mineralization varies from massive and matrix to disseminated, and is nearly always concentrated at the base of the host unit. Primary ores have a relatively simple mineralogy, dominated by pyrrhotite-pentlandite-pyrite, and to a lesser degree millerite. Metamorphic grades tend to range from prehnite-pumpellyite facies through to lower and upper amphibolite facies. Genesis of Group I and II deposits is explained by the eruption of komatiites into rift-phase greenstone belts, as channelized flows, which assimilated variable amounts of footwall rocks during emplacement. Sulphide saturation was dependent on the mode of emplacement and, the amount of sulphidic sediments that became assimilated prior to crystallization. This possibly accounts for variations in ore tenor. The Six Mile Deposit (SMD) in Western Australia, is an adcumulate body of the Group IIB-type, exhibiting disseminated mineralization. The ore has been "upgraded" due to hydration and serpentinization. A profound weathering sequence exists, which was subsequently utilized during initial exploration. Exploration techniques has been focused on Western Australia, as it is here that the most innovative ideas have emerged.
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- Authors: Lane, Monica Leonie
- Date: 1992
- Subjects: Nickel sulfide , Geology, Stratigraphic -- Archaean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4982 , http://hdl.handle.net/10962/d1005594 , Nickel sulfide , Geology, Stratigraphic -- Archaean
- Description: The distribution of Archean Nickel sulphide deposits reflects tectonic controls operating during the evolution of the granitoid greenstone terrains. Important deposits of komatiitic-affinity are concentrated within, and adjacent to, younger (∼2.7 Ga), rift-related greenstone belts (e.g. Canada, Western Australia and Zimababwe). Two important classes of Archean Nickel sulphide deposits exist, formerly known as "Dunitic" and "Peridotitic", these are now referred to as Group I and Group II deposits, based on their characteristic structure and composition. Mineralization varies from massive and matrix to disseminated, and is nearly always concentrated at the base of the host unit. Primary ores have a relatively simple mineralogy, dominated by pyrrhotite-pentlandite-pyrite, and to a lesser degree millerite. Metamorphic grades tend to range from prehnite-pumpellyite facies through to lower and upper amphibolite facies. Genesis of Group I and II deposits is explained by the eruption of komatiites into rift-phase greenstone belts, as channelized flows, which assimilated variable amounts of footwall rocks during emplacement. Sulphide saturation was dependent on the mode of emplacement and, the amount of sulphidic sediments that became assimilated prior to crystallization. This possibly accounts for variations in ore tenor. The Six Mile Deposit (SMD) in Western Australia, is an adcumulate body of the Group IIB-type, exhibiting disseminated mineralization. The ore has been "upgraded" due to hydration and serpentinization. A profound weathering sequence exists, which was subsequently utilized during initial exploration. Exploration techniques has been focused on Western Australia, as it is here that the most innovative ideas have emerged.
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