An historical study of channel change in the Bell river, north eastern Cape
- Authors: Dollar, E S J
- Date: 1993
- Subjects: River channels -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Bell river
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4837 , http://hdl.handle.net/10962/d1005513 , River channels -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Bell river
- Description: Channel instability has occurred in the Bell river, north eastern Cape, in the form of meander cutoffs, incipient meander cutoffs, channel straightening and general channel instability. Recent cutoffs occurred in 1974 and 1988. The study examines the spatial and temporal controls of channel form and pattern in the Bell river in order to assess the causes of channel instability. From the 17 km surveyed stretch, it was found that the main spatial controls of channel form were riparian vegetation density and channel bed material. Discharge as estimated in the field was not the main controlling variable of channel form. Two distinct groups of stream beds were identified from the survey; an upper gravel-bed stream and a lower sand-bed stream. These sites displayed distinct form ratios, channel gradients and bed material characteristics. The incidences of major channel instability were identified as being the transitional zone between the two reaches. Examination of temporal controls of channel form included climatic trend analysis and catchment sediment production analysis. Rainfall analysis indicated that no long term progressive trends in the annual or seasonal data existed. Distinct wet and dry cycles occur with peaks every 16 to 19 years. Wet cycles are the result of an increase in the frequency of daily events rather than in the magnitude of events. Flow record analysis demonstrated the relationship between regional discharge and upper catchment rainfall. Coincidence of peak flows and channel straightening were also noted. Soil erosion surveys showed that erosion had increased in the catchment and that accelerated erosion were probably the result of overstocking and poor veld management. It was concluded that channel changes in the Bell river are possibly the result of anthropogenic influence in catchment and channel processes. Increased sediment production to the channel resulted in channel aggradation with attendant instability. The plantation of riparian vegetation led to perimeter stability in the short term at flows less than bankfull discharge, but served to reduce cross-sectional area in the long term, thereby increasing the potential for flooding, meander cutoffs and channel change
- Full Text:
- Date Issued: 1993
- Authors: Dollar, E S J
- Date: 1993
- Subjects: River channels -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Bell river
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4837 , http://hdl.handle.net/10962/d1005513 , River channels -- South Africa -- Eastern Cape , Sedimentation and deposition -- South Africa -- Eastern Cape , Bell river
- Description: Channel instability has occurred in the Bell river, north eastern Cape, in the form of meander cutoffs, incipient meander cutoffs, channel straightening and general channel instability. Recent cutoffs occurred in 1974 and 1988. The study examines the spatial and temporal controls of channel form and pattern in the Bell river in order to assess the causes of channel instability. From the 17 km surveyed stretch, it was found that the main spatial controls of channel form were riparian vegetation density and channel bed material. Discharge as estimated in the field was not the main controlling variable of channel form. Two distinct groups of stream beds were identified from the survey; an upper gravel-bed stream and a lower sand-bed stream. These sites displayed distinct form ratios, channel gradients and bed material characteristics. The incidences of major channel instability were identified as being the transitional zone between the two reaches. Examination of temporal controls of channel form included climatic trend analysis and catchment sediment production analysis. Rainfall analysis indicated that no long term progressive trends in the annual or seasonal data existed. Distinct wet and dry cycles occur with peaks every 16 to 19 years. Wet cycles are the result of an increase in the frequency of daily events rather than in the magnitude of events. Flow record analysis demonstrated the relationship between regional discharge and upper catchment rainfall. Coincidence of peak flows and channel straightening were also noted. Soil erosion surveys showed that erosion had increased in the catchment and that accelerated erosion were probably the result of overstocking and poor veld management. It was concluded that channel changes in the Bell river are possibly the result of anthropogenic influence in catchment and channel processes. Increased sediment production to the channel resulted in channel aggradation with attendant instability. The plantation of riparian vegetation led to perimeter stability in the short term at flows less than bankfull discharge, but served to reduce cross-sectional area in the long term, thereby increasing the potential for flooding, meander cutoffs and channel change
- Full Text:
- Date Issued: 1993
An investigation into cholinergic interactions in the rat pineal gland
- Authors: Eason, Jason Shane
- Date: 1993
- Subjects: Pineal gland -- Research , Acetylcholine -- Receptors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4048 , http://hdl.handle.net/10962/d1004109 , Pineal gland -- Research , Acetylcholine -- Receptors
- Description: The mammalian pineal gland is mainly innervated by the sympathetic nervous system which modulates the activity of indole pathway enzymes and the secretion of pineal hormones. Recently researchers have demonstrated and characterized the presence of muscarinic cholinergic receptors in the pineal gland. However the role of these receptors remains unclear. In an attempt to investigate the role of cholinergic receptors in the pineal gland, a number of studies were carried out on the various steps in the indole metabolic pathway, using various agents which act on the cholinergic system. Investigations using pineal organ cultures showed that stimulation of these muscarinic cholinergic receptor sites with a parasympathomimetic agent, a rise in levels of aHT occurred without a concomitant increase in aMT levels. Further organ culture experiments using the cholinergic agonist acetylcholine and anticholinesterase agent physostigmine, produced a similar rise in aHT without altering aMT levels. This acetylcholine-induced rise in aHT levels were not altered by the ganglion blocking agent hexamethonium whilst the antimuscarinic agent atropine prevented the acetylcholine-induced rise in aHT levels. Thesefindings suggest that cholinergic agents may play a role in regulating indoleamine synthesis in the pineal gland. Cyclic-AMP assay studies showed that acetylcholine increases pineal cAMP levels significantly and does not influence the isoproterenol-induced cAMP rise in the pineal gland. The cAMP regulator cAMP-phosphodiesterase (cAMP-PDE) was found to increase significantly in the presence of the anticholinesterase agent physostigmine. NAT enzyme studies revealed that physostigmine does not affect NAT enzyme levels significantly and HIOMT studies showed that this agent does not inhibit HIOMT activity. The mechanism by which acetylcholine and physostigmine are able to cause a increase in aHT and not aMT levels needs to be researched further. Acetylcholinesterase enzyme assay studies revealed that the AChE enzyme undergoes a diurnal rhythm in the pineal gland with activity being higher during the day and lower at night. Investigations using the drug reserpine showed that this rhythm is not under the control of the sympathetic nervous system. Further research needs to be done however, in determining whether or not this enzyme is present in the pineal gland to regulate the levels of acetylcholine interacting with muscarinic receptors in the gland, or for some other reason. Choline acetyltransferase studies demonstrate the presence of the enzyme in the rat brain cerebral cortex as well as showing that melatonin increases ChAT enzyme activity in this tissue. This suggests that melatonin plays a role in cholinergic transmission there. ChAT activity could not be measured in the pineal gland however. Muscarinic receptor binding studies also carried out on rat brain cerebral cortex show that melatonin enhances cholinergic receptor affinity and receptor number in this tissue. In summary, data presented herein concur with proposals that: i) the cholinergic system affects the indole metabolic pathway by causing a rise in aRT but not aMT levels. ii) cholinergic agonist acetylcholine causes cAMP levels to rise with a concomitant increase in cAMP-PDE levels. iii) the enzyme acetylcholinesterase undergoes a diurnal rhythm in the pineal gland which is not under the control of the sympathetic nervous system. iv) the activity of the enzyme choline acetyltransferase is increased by melatonin in the rat brain cerebral cortex suggesting that melatonin facilitates cholinergic transmission in this tissue. v) melatonin enhances cholinergic receptor affinity and receptor number in the cerebral cortex of rat brain.
- Full Text:
- Date Issued: 1993
- Authors: Eason, Jason Shane
- Date: 1993
- Subjects: Pineal gland -- Research , Acetylcholine -- Receptors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4048 , http://hdl.handle.net/10962/d1004109 , Pineal gland -- Research , Acetylcholine -- Receptors
- Description: The mammalian pineal gland is mainly innervated by the sympathetic nervous system which modulates the activity of indole pathway enzymes and the secretion of pineal hormones. Recently researchers have demonstrated and characterized the presence of muscarinic cholinergic receptors in the pineal gland. However the role of these receptors remains unclear. In an attempt to investigate the role of cholinergic receptors in the pineal gland, a number of studies were carried out on the various steps in the indole metabolic pathway, using various agents which act on the cholinergic system. Investigations using pineal organ cultures showed that stimulation of these muscarinic cholinergic receptor sites with a parasympathomimetic agent, a rise in levels of aHT occurred without a concomitant increase in aMT levels. Further organ culture experiments using the cholinergic agonist acetylcholine and anticholinesterase agent physostigmine, produced a similar rise in aHT without altering aMT levels. This acetylcholine-induced rise in aHT levels were not altered by the ganglion blocking agent hexamethonium whilst the antimuscarinic agent atropine prevented the acetylcholine-induced rise in aHT levels. Thesefindings suggest that cholinergic agents may play a role in regulating indoleamine synthesis in the pineal gland. Cyclic-AMP assay studies showed that acetylcholine increases pineal cAMP levels significantly and does not influence the isoproterenol-induced cAMP rise in the pineal gland. The cAMP regulator cAMP-phosphodiesterase (cAMP-PDE) was found to increase significantly in the presence of the anticholinesterase agent physostigmine. NAT enzyme studies revealed that physostigmine does not affect NAT enzyme levels significantly and HIOMT studies showed that this agent does not inhibit HIOMT activity. The mechanism by which acetylcholine and physostigmine are able to cause a increase in aHT and not aMT levels needs to be researched further. Acetylcholinesterase enzyme assay studies revealed that the AChE enzyme undergoes a diurnal rhythm in the pineal gland with activity being higher during the day and lower at night. Investigations using the drug reserpine showed that this rhythm is not under the control of the sympathetic nervous system. Further research needs to be done however, in determining whether or not this enzyme is present in the pineal gland to regulate the levels of acetylcholine interacting with muscarinic receptors in the gland, or for some other reason. Choline acetyltransferase studies demonstrate the presence of the enzyme in the rat brain cerebral cortex as well as showing that melatonin increases ChAT enzyme activity in this tissue. This suggests that melatonin plays a role in cholinergic transmission there. ChAT activity could not be measured in the pineal gland however. Muscarinic receptor binding studies also carried out on rat brain cerebral cortex show that melatonin enhances cholinergic receptor affinity and receptor number in this tissue. In summary, data presented herein concur with proposals that: i) the cholinergic system affects the indole metabolic pathway by causing a rise in aRT but not aMT levels. ii) cholinergic agonist acetylcholine causes cAMP levels to rise with a concomitant increase in cAMP-PDE levels. iii) the enzyme acetylcholinesterase undergoes a diurnal rhythm in the pineal gland which is not under the control of the sympathetic nervous system. iv) the activity of the enzyme choline acetyltransferase is increased by melatonin in the rat brain cerebral cortex suggesting that melatonin facilitates cholinergic transmission in this tissue. v) melatonin enhances cholinergic receptor affinity and receptor number in the cerebral cortex of rat brain.
- Full Text:
- Date Issued: 1993
An investigation into the potential immunogenicity of various extracts of the South African bont tick Amblyomma hebraeum
- Authors: Adamson, Deborah Jane
- Date: 1993
- Subjects: Amblyomma -- South Africa , Ticks -- South Africa , Ticks -- Control -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4127 , http://hdl.handle.net/10962/d1015640
- Description: Rabbits and goats were inoculated with crude, membrane-associated and soluble components extracted from unengorged adult females and nymphs of the bont tick Amblyomma hebraeum. Inoculation provided some protection against nymphal infestation, however it had little effect on adult feeding. Histological examination of adults fed on inoculated hosts showed evidence of gut damage. Skin provocation testing with tick extracts elicited a Type I immediate hypersensitivity which was influenced by antihistamine. A delayed skin reaction was also evident. Whether this was attributable to Type III Arthus reaction or Type IV cell-mediated hypersensitivity was not determined. A comparative histological study of sites of tick extract injection, on inoculated and naive hosts, demonstrated the role of eosinophils in the hosts response to tick feeding. Serological examination revealed elevated anti-A hebraeum lgG titres following inoculation. These titres were found to decrease in the ten weeks after inoculation, despite the hosts being repeatedly infested with A hebraeum. Although the IgG titres of naive control hosts increased after each tick infestation, they failed to reach the titres achieved through inoculation. Western blot analysis of serum from inoculated hosts recognized most of the A. hebraeum proteins against which it was screened.
- Full Text:
- Date Issued: 1993
- Authors: Adamson, Deborah Jane
- Date: 1993
- Subjects: Amblyomma -- South Africa , Ticks -- South Africa , Ticks -- Control -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4127 , http://hdl.handle.net/10962/d1015640
- Description: Rabbits and goats were inoculated with crude, membrane-associated and soluble components extracted from unengorged adult females and nymphs of the bont tick Amblyomma hebraeum. Inoculation provided some protection against nymphal infestation, however it had little effect on adult feeding. Histological examination of adults fed on inoculated hosts showed evidence of gut damage. Skin provocation testing with tick extracts elicited a Type I immediate hypersensitivity which was influenced by antihistamine. A delayed skin reaction was also evident. Whether this was attributable to Type III Arthus reaction or Type IV cell-mediated hypersensitivity was not determined. A comparative histological study of sites of tick extract injection, on inoculated and naive hosts, demonstrated the role of eosinophils in the hosts response to tick feeding. Serological examination revealed elevated anti-A hebraeum lgG titres following inoculation. These titres were found to decrease in the ten weeks after inoculation, despite the hosts being repeatedly infested with A hebraeum. Although the IgG titres of naive control hosts increased after each tick infestation, they failed to reach the titres achieved through inoculation. Western blot analysis of serum from inoculated hosts recognized most of the A. hebraeum proteins against which it was screened.
- Full Text:
- Date Issued: 1993
An investigation of Borrelia burgdorferi in South Africa
- Authors: Nurton, Jane Patricia
- Date: 1993
- Subjects: Ticks , Ticks as carriers of disease , Borrelia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5722 , http://hdl.handle.net/10962/d1005408 , Ticks , Ticks as carriers of disease , Borrelia
- Description: Four commonly occurring genera of ticks in South Africa were tested for their capacity to acquire and transmit Borrelia burgdoiferi, the causative agent of Lyme disease. Attempts were made to infect rabbits with a culture of B. burgdoiferi, and tick transmission experiments were carried out using the rabbits as the host of infection. Only one rabbit was successfully infected. Histological changes associated with a B. burgdoiferi infection were noted in this rabbit, but no spirochaetes were isolated. All other host animals failed to become infected with the B. burgdoiferi. As a consequence transmission experiments with the local ticks failed. Serological surveys conducted on rodents, horses and cattle using immunofluorescent and haemagglutination tests indicated that there is evidence that Borrelia species occur widely and that there is a possibility of B. burgdoiferi occurring in South Africa. Studies conducted on ticks from suspected endemic areas revealed the presence, in Ixodes bakeri only, of a spirochaete-like organism that reacted with monoclonal antibody H5332. Shortcomings of the study are highlighted and proposals are presented to address the problem of identifying specific B. burgdoiferi infections.
- Full Text:
- Date Issued: 1993
- Authors: Nurton, Jane Patricia
- Date: 1993
- Subjects: Ticks , Ticks as carriers of disease , Borrelia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5722 , http://hdl.handle.net/10962/d1005408 , Ticks , Ticks as carriers of disease , Borrelia
- Description: Four commonly occurring genera of ticks in South Africa were tested for their capacity to acquire and transmit Borrelia burgdoiferi, the causative agent of Lyme disease. Attempts were made to infect rabbits with a culture of B. burgdoiferi, and tick transmission experiments were carried out using the rabbits as the host of infection. Only one rabbit was successfully infected. Histological changes associated with a B. burgdoiferi infection were noted in this rabbit, but no spirochaetes were isolated. All other host animals failed to become infected with the B. burgdoiferi. As a consequence transmission experiments with the local ticks failed. Serological surveys conducted on rodents, horses and cattle using immunofluorescent and haemagglutination tests indicated that there is evidence that Borrelia species occur widely and that there is a possibility of B. burgdoiferi occurring in South Africa. Studies conducted on ticks from suspected endemic areas revealed the presence, in Ixodes bakeri only, of a spirochaete-like organism that reacted with monoclonal antibody H5332. Shortcomings of the study are highlighted and proposals are presented to address the problem of identifying specific B. burgdoiferi infections.
- Full Text:
- Date Issued: 1993
Anniversary Bulletin: 50th year of struggle... and the sgtruggle continues
- Date: 1993
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/34038 , vital:33178 , Bulk File 7
- Description: This is the 50th Anniversary Bulletin of the Unity Movement.
- Full Text: false
- Date Issued: 1993
- Date: 1993
- Subjects: Government, Resistance to -- South Africa , South Africa -- History -- 20th century , South Africa -- Politics and government
- Language: English
- Type: text , Article
- Identifier: http://hdl.handle.net/10948/34038 , vital:33178 , Bulk File 7
- Description: This is the 50th Anniversary Bulletin of the Unity Movement.
- Full Text: false
- Date Issued: 1993
Annotated checklist of the epipelagic and shore fishes of the Maldive Islands
- Randall, John E, 1924-, Anderson, R Charles
- Authors: Randall, John E, 1924- , Anderson, R Charles
- Date: 1993
- Language: English
- Type: Text
- Identifier: vital:15035 , http://hdl.handle.net/10962/d1019913 , ISSN 0073-4381 , ISBN 0-86810-261-X , Ichthyological Bulletin of the J.L.B. Smith Insitute of Ichthyology; No. 59
- Description: A historical resume of fish collecting in the Maldive Islands is presented, beginning with the collection o f J. Stanley Gardiner in 1899-1900. Specimens of Maldives fishes have been examined at the Marine Research Section of the Ministry of Fisheries and Agriculture, Republic of Maldives and the five museums which house most of the fishes that have been collected in the islands: the Natural History Museum, London; Bernice P. Bishop Museum, Honolulu; California Academy of Sciences, San Francisco; Field Museum of Natural History, Chicago; and the Senckenberg Museum, Frankfurt. A total of 899 species of epipelagic and shore fishes are recorded from the Maldives; 201 of these are new records for the islands. Thirty-two of the 899 are recorded by generic name only. Some of these could not be identified to species due to poor condition or to their being juveniles, but most appear to be undescribed. , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1993
- Authors: Randall, John E, 1924- , Anderson, R Charles
- Date: 1993
- Language: English
- Type: Text
- Identifier: vital:15035 , http://hdl.handle.net/10962/d1019913 , ISSN 0073-4381 , ISBN 0-86810-261-X , Ichthyological Bulletin of the J.L.B. Smith Insitute of Ichthyology; No. 59
- Description: A historical resume of fish collecting in the Maldive Islands is presented, beginning with the collection o f J. Stanley Gardiner in 1899-1900. Specimens of Maldives fishes have been examined at the Marine Research Section of the Ministry of Fisheries and Agriculture, Republic of Maldives and the five museums which house most of the fishes that have been collected in the islands: the Natural History Museum, London; Bernice P. Bishop Museum, Honolulu; California Academy of Sciences, San Francisco; Field Museum of Natural History, Chicago; and the Senckenberg Museum, Frankfurt. A total of 899 species of epipelagic and shore fishes are recorded from the Maldives; 201 of these are new records for the islands. Thirty-two of the 899 are recorded by generic name only. Some of these could not be identified to species due to poor condition or to their being juveniles, but most appear to be undescribed. , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1993
Antimicrobial resistance patterns in a Port Elizabeth hospital
- Authors: Meiring, Jillian A
- Date: 1993
- Subjects: Antibiotics , Drug resistance in microorganisms , Hospitals -- Drug distribution systems -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4043 , http://hdl.handle.net/10962/d1004104 , Antibiotics , Drug resistance in microorganisms , Hospitals -- Drug distribution systems -- South Africa -- Port Elizabeth
- Description: Antibiotic resistance in clinical bacterial isolates remains an ongoing problem requiring continuous monitoring to effect some form of control. Comparative studies have not been previously reported for the Eastern Cape Region, South Africa and this study was undertaken to monitor resistance patterns in clinical isolates from Provincial Hospital, Port Elizabeth. Over the three year period 1989 to 1991, 9888 susceptibility results from isolates examined in the SAIMR pathology laboratory were analysed and collated using a stand-alone computer program. Resistance patterns for a range of nineteen antibiotics were collated for isolates from various sampling points within the hospital. Results were reported as resistance patterns in individually isolated species. Levels of resistance in each species were compared to those reported from South Africa and abroad, and changing patterns of resistance were noted within the three year period at the Provincial Hospital, Port Elizabeth.
- Full Text:
- Date Issued: 1993
- Authors: Meiring, Jillian A
- Date: 1993
- Subjects: Antibiotics , Drug resistance in microorganisms , Hospitals -- Drug distribution systems -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4043 , http://hdl.handle.net/10962/d1004104 , Antibiotics , Drug resistance in microorganisms , Hospitals -- Drug distribution systems -- South Africa -- Port Elizabeth
- Description: Antibiotic resistance in clinical bacterial isolates remains an ongoing problem requiring continuous monitoring to effect some form of control. Comparative studies have not been previously reported for the Eastern Cape Region, South Africa and this study was undertaken to monitor resistance patterns in clinical isolates from Provincial Hospital, Port Elizabeth. Over the three year period 1989 to 1991, 9888 susceptibility results from isolates examined in the SAIMR pathology laboratory were analysed and collated using a stand-alone computer program. Resistance patterns for a range of nineteen antibiotics were collated for isolates from various sampling points within the hospital. Results were reported as resistance patterns in individually isolated species. Levels of resistance in each species were compared to those reported from South Africa and abroad, and changing patterns of resistance were noted within the three year period at the Provincial Hospital, Port Elizabeth.
- Full Text:
- Date Issued: 1993
Aspects of the biology and ecology of the South African abalone Haliotis midae Linnaeus, 1758 (Mollusca Gastropoda) along the eastern Cape and Ciskei coast
- Authors: Wood, A D (Aidan David)
- Date: 1993
- Subjects: Abalones -- South Africa , Abalones -- Ecology , Abalones -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5220 , http://hdl.handle.net/10962/d1005063
- Description: The South African abalone Haliotis midae Linnaeus, 1758, is an important commercial, recreational and aquaculture mollusc species. It is the largest of the six haliotid species found in South African waters and has the second largest distributional range aside from Haliotis spadicea which is widely exploited by rock and surf anglers as bait. Analysis of population structure at Great Fish Point revealed that H. midae exhibited a high degree of microhabitat specificity, and that while dietary habits played a role in habitat selection, it was ultimately the activities of predators which confined size classes to particular niches and restricted all animals to nocturnal activities. Large (> 100 mm SL) exposed animals relied on shell thickness and adhesion to combat predators, while small (> 45 mm SL) sub-boulder animals and medium sized (50 - 95 mm SL) animals relied on their cryptic microhabitats and the protective spine canopies of co-resident urchins (Parechinus angulosus) for daytime protection. Populations of H. midae were discontinuously distributed along the coast, occupying small isolated reefs which offered a suitable array of microhabitats and a good food supply. They mostly inhabited shallow intertidal and subtidal reefs, but were occasionally encountered on deeper subtidal reefs at 4 - 5 meters. Mean length- and width-at-age were determined from growth rings composed of alternate conchiolin (dark) and aragonite (white) bands in the internal nacreous shell layer. Growth was described by the Special Von Bertalanffy growth equation: Lt(mm) = 176.998918 (1 - e⁻°·²⁴²⁴¹⁹⁽t ⁺ °·⁴⁹⁵⁴⁹⁴⁾) Wt(mm) = 159.705689 (1 - e⁻°·¹⁹⁵⁴³⁹⁽t ⁺ °·²¹¹⁶⁾) The ageing technique used was validated for animals from Great Fish Point and Mgwalana using independent tag-return data. The same data provided evidence that growth rates varied between animals from Great Fish Point and Bird Island. The growth data also showed that H. midae exhibited a high degree of individual variation in growth rate. Males and females exhibited similar growth rates. Exposed large animals showed a preference for red seaweeds, in particular Plocamium corallorhiza and Hypnea spicifera, while small sub-boulder cryptic animals included larger proportions of brown (Ralfsia expansa) and green (VIva spp.) algae in their diets. Exposed individuals also exhibited a higher degree of selectivity towards prey items, but in general, stomach contents reflected the most abundant seaweed types. Both drift and attached algal species were utilized by H. midae which was a nocturnal feeder. Pigments from red algae were incorporated into the shell layers giving the shells a pink or brick red colour. Haliotis midae is a dioecious broadcast spawner. Gonad Bulk Indices in combination with detailed histological examination of gonads showed that individuals were iteroparous, asynchronous spawners and that the breeding season extended from March through to October, although the peak spawning activity was between April and June. Males and females can spawn partially, totally or not at all, with atresia of residual gametes occurring after spawning. There is no resting stage, and gametogenesis is initiated directly after spawning. The structure of the ovary and testis and the process of gametogenesis is typical of haliotid species. AI: 1 sex ratio was observed from all populations studied. Sexual maturity was first attained in the 40 - 59 mm SL size class, although evidence for the smallest size at first spawning was recorded at 54.6 mm SL for females and 69 mm SL for males. Sizes at 50% sexual maturity were 72.5 mm SL (52.8 mm SW) at Great Fish Point, 72.5 mm SL (57.4 mm SW) at Mgwalana, 73.7 mm SL (51.2 mm SW) at Cape Recife, and 73.5 mm SL (53.8 mm SW) at Kelly's Beach. Haliotis midae was typically highly fecund, although a high degree of variation resulting in poor relationships between fecundity/shell length and gonad weight/shell length. The relationship between fecundity and gonad weight was linear. In the Eastern Cape, H. midae possessed a faster growth rate, smaller size at sexual maturity, smaller maximum size and lower longevity when compared to con specifics in Western Cape waters. A smaller minimum legal size of 93 mm SW is proposed for Eastern Cape animals and it is suggested that the closed season be moved to the peak spawning period between April and June. The benefit of a closed season during the spawning period is questioned, and the feasibility of closed areas as a management option for H. midae in the Eastern Cape is discussed.
- Full Text:
- Date Issued: 1993
- Authors: Wood, A D (Aidan David)
- Date: 1993
- Subjects: Abalones -- South Africa , Abalones -- Ecology , Abalones -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5220 , http://hdl.handle.net/10962/d1005063
- Description: The South African abalone Haliotis midae Linnaeus, 1758, is an important commercial, recreational and aquaculture mollusc species. It is the largest of the six haliotid species found in South African waters and has the second largest distributional range aside from Haliotis spadicea which is widely exploited by rock and surf anglers as bait. Analysis of population structure at Great Fish Point revealed that H. midae exhibited a high degree of microhabitat specificity, and that while dietary habits played a role in habitat selection, it was ultimately the activities of predators which confined size classes to particular niches and restricted all animals to nocturnal activities. Large (> 100 mm SL) exposed animals relied on shell thickness and adhesion to combat predators, while small (> 45 mm SL) sub-boulder animals and medium sized (50 - 95 mm SL) animals relied on their cryptic microhabitats and the protective spine canopies of co-resident urchins (Parechinus angulosus) for daytime protection. Populations of H. midae were discontinuously distributed along the coast, occupying small isolated reefs which offered a suitable array of microhabitats and a good food supply. They mostly inhabited shallow intertidal and subtidal reefs, but were occasionally encountered on deeper subtidal reefs at 4 - 5 meters. Mean length- and width-at-age were determined from growth rings composed of alternate conchiolin (dark) and aragonite (white) bands in the internal nacreous shell layer. Growth was described by the Special Von Bertalanffy growth equation: Lt(mm) = 176.998918 (1 - e⁻°·²⁴²⁴¹⁹⁽t ⁺ °·⁴⁹⁵⁴⁹⁴⁾) Wt(mm) = 159.705689 (1 - e⁻°·¹⁹⁵⁴³⁹⁽t ⁺ °·²¹¹⁶⁾) The ageing technique used was validated for animals from Great Fish Point and Mgwalana using independent tag-return data. The same data provided evidence that growth rates varied between animals from Great Fish Point and Bird Island. The growth data also showed that H. midae exhibited a high degree of individual variation in growth rate. Males and females exhibited similar growth rates. Exposed large animals showed a preference for red seaweeds, in particular Plocamium corallorhiza and Hypnea spicifera, while small sub-boulder cryptic animals included larger proportions of brown (Ralfsia expansa) and green (VIva spp.) algae in their diets. Exposed individuals also exhibited a higher degree of selectivity towards prey items, but in general, stomach contents reflected the most abundant seaweed types. Both drift and attached algal species were utilized by H. midae which was a nocturnal feeder. Pigments from red algae were incorporated into the shell layers giving the shells a pink or brick red colour. Haliotis midae is a dioecious broadcast spawner. Gonad Bulk Indices in combination with detailed histological examination of gonads showed that individuals were iteroparous, asynchronous spawners and that the breeding season extended from March through to October, although the peak spawning activity was between April and June. Males and females can spawn partially, totally or not at all, with atresia of residual gametes occurring after spawning. There is no resting stage, and gametogenesis is initiated directly after spawning. The structure of the ovary and testis and the process of gametogenesis is typical of haliotid species. AI: 1 sex ratio was observed from all populations studied. Sexual maturity was first attained in the 40 - 59 mm SL size class, although evidence for the smallest size at first spawning was recorded at 54.6 mm SL for females and 69 mm SL for males. Sizes at 50% sexual maturity were 72.5 mm SL (52.8 mm SW) at Great Fish Point, 72.5 mm SL (57.4 mm SW) at Mgwalana, 73.7 mm SL (51.2 mm SW) at Cape Recife, and 73.5 mm SL (53.8 mm SW) at Kelly's Beach. Haliotis midae was typically highly fecund, although a high degree of variation resulting in poor relationships between fecundity/shell length and gonad weight/shell length. The relationship between fecundity and gonad weight was linear. In the Eastern Cape, H. midae possessed a faster growth rate, smaller size at sexual maturity, smaller maximum size and lower longevity when compared to con specifics in Western Cape waters. A smaller minimum legal size of 93 mm SW is proposed for Eastern Cape animals and it is suggested that the closed season be moved to the peak spawning period between April and June. The benefit of a closed season during the spawning period is questioned, and the feasibility of closed areas as a management option for H. midae in the Eastern Cape is discussed.
- Full Text:
- Date Issued: 1993
Aspects of the symplectic and metric geometry of classical and quantum physics
- Authors: Russell, Neil Eric
- Date: 1993
- Subjects: Symplectic manifolds Geometry, Differential Geometric quantization Quantum theory Clifford algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5452 , http://hdl.handle.net/10962/d1005237
- Description: I investigate some algebras and calculi naturally associated with the symplectic and metric Clifford algebras. In particular, I reformulate the well known Lepage decomposition for the symplectic exterior algebra in geometrical form and present some new results relating to the simple subspaces of the decomposition. I then present an analogous decomposition for the symmetric exterior algebra with a metric. Finally, I extend this symmetric exterior algebra into a new calculus for the symmetric differential forms on a pseudo-Riemannian manifold. The importance of this calculus lies in its potential for the description of bosonic systems in Quantum Theory.
- Full Text:
- Date Issued: 1993
- Authors: Russell, Neil Eric
- Date: 1993
- Subjects: Symplectic manifolds Geometry, Differential Geometric quantization Quantum theory Clifford algebras
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5452 , http://hdl.handle.net/10962/d1005237
- Description: I investigate some algebras and calculi naturally associated with the symplectic and metric Clifford algebras. In particular, I reformulate the well known Lepage decomposition for the symplectic exterior algebra in geometrical form and present some new results relating to the simple subspaces of the decomposition. I then present an analogous decomposition for the symmetric exterior algebra with a metric. Finally, I extend this symmetric exterior algebra into a new calculus for the symmetric differential forms on a pseudo-Riemannian manifold. The importance of this calculus lies in its potential for the description of bosonic systems in Quantum Theory.
- Full Text:
- Date Issued: 1993
Bioaccumulation of metal cations by yeast and yeast cell components
- Authors: Brady, Dean
- Date: 1993
- Subjects: Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4046 , http://hdl.handle.net/10962/d1004107 , Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Description: The aim of the project was to determine whether a by-product of industrial fermentations, Saccharomyces cerevisiae, could be utilized to bioaccumulate heavy metal cations and to partially define the mechanism of accumulation. S. cerevisiae cells were found to be capable of accumulating Cu²⁺in a manner that was proportional to the external Cu²⁺ concentration and inversely proportional to the concentration of biomass. The accumulation process was only minimally affected by temperature variations between 5 and 40°C or high ambient concentrations of sodium chloride. The accumulation process was however considerably affected by variations in pH, bioaccumulation being most efficient at pH 5 - 9 but becoming rapidly less so at either extreme of pH. Selection for copper resistant or tolerant yeast diminished the yeast's capacity for Cu²⁺ accumulation. For this and other reasons the development of heavy metal tolerance in yeasts was deemed to be generally counterproductive to heavy metal bioaccumulation. The yeast biomass was also capable of accumulating other heavy metal cations such as c0²⁺ or Cd²⁺. The yeast biomass could be harvested after bioaccumulation by tangential filtration methods, or alternatively could be packed into hollow fibre microfilter membrane cartridges and used as a fixed-bed bioaccumulator. By immobilizing the yeast in polyacrylamide gel and packing this material into columns, cu²⁺, C0²⁺ or Cd²⁺ could be removed from influent aqueous solutions yielding effluents with no detectable heavy metal, until breakthrough point was reached. This capacity was hypothesized to be a function of numerous "theoretical plates of equilibrium" within the column. The immobilized biomass could be eluted with EDTA and recycled for further bioaccumulation processes with minor loss of bioaccumulation capacity. Yeast cells were fractionated to permit identification of the major cell fractions and molecular components responsible for metal binding. Isolation of the yeast cell walls permitted investigation of their role in heavy metal accumulation. Although the amino groups of chitosan and proteins, the carboxyl groups of proteins, and the phosphate groups of phosphomannans were found to be efficient groups for the accumulation of copper, the less effective hydroxyl groups of the carbohydrate polymers (glucans and mannans) had a similar overall capacity for copper accumulation owing to their predominance in the yeast cell wall. The outer (protein-mannan) layer of the yeast cell wall was found to be a better Cu²⁺ chelator than the inner (chitinglucan) layer. It appeared that the physical condition of the cell wall may be more important than the individual macromolecular components of the cell wall in metal accumulation. It was apparent that the cell wall was the major, if not the sole contributor to heavy metal accumulation at low ambient heavy metal concentrations. At higher ambient metal concentrations the cytosol and vacuole become involved in bioaccumulation. Copper and other metals caused rapid loss of 70% of the intracellular potassium, implying permeation of the plasma membrane. This was followed by a slower "leakage" of magnesium from the vacuole which paralleled Cu²⁺ accumulation, suggesting that it may represent some form of ion-exchange. An intracellular copper chelating agent of approximately 2 kDalton molecular mass was isolated from copper tolerant yeast. This chelator was not a metallothionein and bound relatively low molar equivalents of copper compared to those reported for metallothionein. Treatment of the biomass with hot alkali yielded two biosorbents, one soluble (which could be used as a heavy metal flocculent), and an insoluble biosorbent which could be formed into a granular product to be used in fixed-bed biosorption columns. The granular biosorbent could accumulate a wide range of heavy metal cations in a semispecific manner and could be stored in a dehydrated form indefinitely, and rehydrated when required. Bioaccumulation by live algae was investigated as an alternative to yeast based processes. Various strains of algae, of which Scenedesmus and Selenastrum were the most effective, were found to be capable of accumulating heavy metals such as Cu²⁺, Pb²⁺ and Cr³⁺.
- Full Text:
- Date Issued: 1993
- Authors: Brady, Dean
- Date: 1993
- Subjects: Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4046 , http://hdl.handle.net/10962/d1004107 , Yeast , Yeast fungi -- Biotechnology , Cations , Metal ions
- Description: The aim of the project was to determine whether a by-product of industrial fermentations, Saccharomyces cerevisiae, could be utilized to bioaccumulate heavy metal cations and to partially define the mechanism of accumulation. S. cerevisiae cells were found to be capable of accumulating Cu²⁺in a manner that was proportional to the external Cu²⁺ concentration and inversely proportional to the concentration of biomass. The accumulation process was only minimally affected by temperature variations between 5 and 40°C or high ambient concentrations of sodium chloride. The accumulation process was however considerably affected by variations in pH, bioaccumulation being most efficient at pH 5 - 9 but becoming rapidly less so at either extreme of pH. Selection for copper resistant or tolerant yeast diminished the yeast's capacity for Cu²⁺ accumulation. For this and other reasons the development of heavy metal tolerance in yeasts was deemed to be generally counterproductive to heavy metal bioaccumulation. The yeast biomass was also capable of accumulating other heavy metal cations such as c0²⁺ or Cd²⁺. The yeast biomass could be harvested after bioaccumulation by tangential filtration methods, or alternatively could be packed into hollow fibre microfilter membrane cartridges and used as a fixed-bed bioaccumulator. By immobilizing the yeast in polyacrylamide gel and packing this material into columns, cu²⁺, C0²⁺ or Cd²⁺ could be removed from influent aqueous solutions yielding effluents with no detectable heavy metal, until breakthrough point was reached. This capacity was hypothesized to be a function of numerous "theoretical plates of equilibrium" within the column. The immobilized biomass could be eluted with EDTA and recycled for further bioaccumulation processes with minor loss of bioaccumulation capacity. Yeast cells were fractionated to permit identification of the major cell fractions and molecular components responsible for metal binding. Isolation of the yeast cell walls permitted investigation of their role in heavy metal accumulation. Although the amino groups of chitosan and proteins, the carboxyl groups of proteins, and the phosphate groups of phosphomannans were found to be efficient groups for the accumulation of copper, the less effective hydroxyl groups of the carbohydrate polymers (glucans and mannans) had a similar overall capacity for copper accumulation owing to their predominance in the yeast cell wall. The outer (protein-mannan) layer of the yeast cell wall was found to be a better Cu²⁺ chelator than the inner (chitinglucan) layer. It appeared that the physical condition of the cell wall may be more important than the individual macromolecular components of the cell wall in metal accumulation. It was apparent that the cell wall was the major, if not the sole contributor to heavy metal accumulation at low ambient heavy metal concentrations. At higher ambient metal concentrations the cytosol and vacuole become involved in bioaccumulation. Copper and other metals caused rapid loss of 70% of the intracellular potassium, implying permeation of the plasma membrane. This was followed by a slower "leakage" of magnesium from the vacuole which paralleled Cu²⁺ accumulation, suggesting that it may represent some form of ion-exchange. An intracellular copper chelating agent of approximately 2 kDalton molecular mass was isolated from copper tolerant yeast. This chelator was not a metallothionein and bound relatively low molar equivalents of copper compared to those reported for metallothionein. Treatment of the biomass with hot alkali yielded two biosorbents, one soluble (which could be used as a heavy metal flocculent), and an insoluble biosorbent which could be formed into a granular product to be used in fixed-bed biosorption columns. The granular biosorbent could accumulate a wide range of heavy metal cations in a semispecific manner and could be stored in a dehydrated form indefinitely, and rehydrated when required. Bioaccumulation by live algae was investigated as an alternative to yeast based processes. Various strains of algae, of which Scenedesmus and Selenastrum were the most effective, were found to be capable of accumulating heavy metals such as Cu²⁺, Pb²⁺ and Cr³⁺.
- Full Text:
- Date Issued: 1993
Central committee - Save Jobs - Protect standards
- NUM
- Authors: NUM
- Date: Feb 1993
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149528 , vital:38861
- Description: It is one year since our last Central Committee.During this period much has happened on the international and domestic front. Yugoslavia remains at war, the United States of America has the first democratic President since Carter and millions of people are starving. It is not only in Somalia that people are starving.Right here at home over two million people are fed by poverty relief programmes. Although we thought that democracy was at hand, it has still eluded us in 1992. The Apartheid government still remains firmly entrenched although the negotiations with the African National Congress show some glimmer that the multilateral negotiations will resume shortly, the establishmant of a transitional government and the holding of the first non-racial national democratic elections by the end of 1993 or early 1994. With the violence still not under control we continue to see our people under siege, families broken up and property destroyed. For peace there must be democracy. Apartheid has left incalculable damage and a legacy that will have to be addressed. As the National Union of Mineworkers we have made and will have to continue to make many sacrifices. 1993 heralds important challenges for our union and the democratic movement as a whole. Central Committee will have to deliberate on these matters and decide the way forward for the coming months.
- Full Text:
- Date Issued: Feb 1993
- Authors: NUM
- Date: Feb 1993
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149528 , vital:38861
- Description: It is one year since our last Central Committee.During this period much has happened on the international and domestic front. Yugoslavia remains at war, the United States of America has the first democratic President since Carter and millions of people are starving. It is not only in Somalia that people are starving.Right here at home over two million people are fed by poverty relief programmes. Although we thought that democracy was at hand, it has still eluded us in 1992. The Apartheid government still remains firmly entrenched although the negotiations with the African National Congress show some glimmer that the multilateral negotiations will resume shortly, the establishmant of a transitional government and the holding of the first non-racial national democratic elections by the end of 1993 or early 1994. With the violence still not under control we continue to see our people under siege, families broken up and property destroyed. For peace there must be democracy. Apartheid has left incalculable damage and a legacy that will have to be addressed. As the National Union of Mineworkers we have made and will have to continue to make many sacrifices. 1993 heralds important challenges for our union and the democratic movement as a whole. Central Committee will have to deliberate on these matters and decide the way forward for the coming months.
- Full Text:
- Date Issued: Feb 1993
Central committee report
- NUM
- Authors: NUM
- Date: Feb 1993
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149576 , vital:38865
- Description: The National Union of Mineworkers (NUM) held a successful 1993 Central Committee (CC) meeting from 11-13 February at CSIR Centre in Pretoria. The CC attended by 300 delegates from the 16 regions of the union representing 280 000 members deliberated key issues affecting workers in mining and energy sectors. With the opening session, the 11th, being the third anniversary of the release of NUM honorary president, Nelson Mandela, the stage was set for tough decisions to be taken on the current political developments in South Africa. NUM president, James Motlatsi outlined general guidelines on major issues affecting workers in his keynote address. Major issues for discussion were: Retrenchments, NUM’s role in the forthcoming national democratic elections, Wages and conditions of employment demands for 1993, Assessment of the state of the NUM. It took delegates three days of serious discussions to come out with decisions which will guide the union in this dynamic period in the history of our country. NUM was honoured to have ANC secretary general, Cyril Ramaphosa as a guest speaker on the current political developments. COSATU general secretary, Jay Naidoo also gave us the honour by giving an invaluable input on the challenges faced by the labour movement today. The CC culminated with a mass rally in Klerksdorp on the 14th February for report back. The CC was held under the theme: Save jobs and protect standards. Forward to democratic elections. Details of CC decisions are given in this report. Please note that this report is not the official record of the CC proceedings but is a summary guide prepared by the NUM media department for the information of members. We suggest you keep it for future reference.
- Full Text:
- Date Issued: Feb 1993
- Authors: NUM
- Date: Feb 1993
- Subjects: NUM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149576 , vital:38865
- Description: The National Union of Mineworkers (NUM) held a successful 1993 Central Committee (CC) meeting from 11-13 February at CSIR Centre in Pretoria. The CC attended by 300 delegates from the 16 regions of the union representing 280 000 members deliberated key issues affecting workers in mining and energy sectors. With the opening session, the 11th, being the third anniversary of the release of NUM honorary president, Nelson Mandela, the stage was set for tough decisions to be taken on the current political developments in South Africa. NUM president, James Motlatsi outlined general guidelines on major issues affecting workers in his keynote address. Major issues for discussion were: Retrenchments, NUM’s role in the forthcoming national democratic elections, Wages and conditions of employment demands for 1993, Assessment of the state of the NUM. It took delegates three days of serious discussions to come out with decisions which will guide the union in this dynamic period in the history of our country. NUM was honoured to have ANC secretary general, Cyril Ramaphosa as a guest speaker on the current political developments. COSATU general secretary, Jay Naidoo also gave us the honour by giving an invaluable input on the challenges faced by the labour movement today. The CC culminated with a mass rally in Klerksdorp on the 14th February for report back. The CC was held under the theme: Save jobs and protect standards. Forward to democratic elections. Details of CC decisions are given in this report. Please note that this report is not the official record of the CC proceedings but is a summary guide prepared by the NUM media department for the information of members. We suggest you keep it for future reference.
- Full Text:
- Date Issued: Feb 1993
Chemical and spectroscopic studies of chromone derivatives
- Ramaite, Ipfani David Isaiah
- Authors: Ramaite, Ipfani David Isaiah
- Date: 1993 , 2012-11-16
- Subjects: Heterocyclic compounds -- Derivatives -- Research , Benzopyrans -- Research , Coumarins -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4422 , http://hdl.handle.net/10962/d1006888 , Heterocyclic compounds -- Derivatives -- Research , Benzopyrans -- Research , Coumarins -- Research
- Description: A number of biologically active chromones occur in plants (eg. Khellin) and research in this field has eventually led to the discovery of chromoglycic acid, which is widely used as a sodium salt in asthma therapy. Since biological activity may be related to acidity, a range of chromone-2-carboxylic acids have been prepared via Claisen acylation of substituted o- hydroxyacetophenones and their acid dissociation constants determined potentiometrically to explore substituent effects. From this study it has been found that introduction of certain groups does have a marked effect on acidity. A variety of acrylamide derivatives have been prepared via the dimethylamine-mediated ring opening of chromone-2-carboxamides which, in turn, were prepared from the chromone-2- carboxylic acids via the corresponding acid chlorides. Variable temperature NMR spectroscopy was employed to examine the effect of substituents on the rotational barriers and it has been found that for the acrylamides examined, ring substituents have little effect on the rotational barriers. A combination of low resolution, high resolution and meta-stable peak analysis has been used to study mass fragmentation patterns for a series of acrylamide derivatives. The proposed fragmentation pathways for selected peaks have been found to be common to all the spectra examined when differences in the atomic masses of substituents were taken into account.
- Full Text:
- Date Issued: 1993
- Authors: Ramaite, Ipfani David Isaiah
- Date: 1993 , 2012-11-16
- Subjects: Heterocyclic compounds -- Derivatives -- Research , Benzopyrans -- Research , Coumarins -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4422 , http://hdl.handle.net/10962/d1006888 , Heterocyclic compounds -- Derivatives -- Research , Benzopyrans -- Research , Coumarins -- Research
- Description: A number of biologically active chromones occur in plants (eg. Khellin) and research in this field has eventually led to the discovery of chromoglycic acid, which is widely used as a sodium salt in asthma therapy. Since biological activity may be related to acidity, a range of chromone-2-carboxylic acids have been prepared via Claisen acylation of substituted o- hydroxyacetophenones and their acid dissociation constants determined potentiometrically to explore substituent effects. From this study it has been found that introduction of certain groups does have a marked effect on acidity. A variety of acrylamide derivatives have been prepared via the dimethylamine-mediated ring opening of chromone-2-carboxamides which, in turn, were prepared from the chromone-2- carboxylic acids via the corresponding acid chlorides. Variable temperature NMR spectroscopy was employed to examine the effect of substituents on the rotational barriers and it has been found that for the acrylamides examined, ring substituents have little effect on the rotational barriers. A combination of low resolution, high resolution and meta-stable peak analysis has been used to study mass fragmentation patterns for a series of acrylamide derivatives. The proposed fragmentation pathways for selected peaks have been found to be common to all the spectra examined when differences in the atomic masses of substituents were taken into account.
- Full Text:
- Date Issued: 1993
Coastal dune ecology and management in the Eastern Cape
- Authors: Avis, Anthony Mark
- Date: 1993
- Subjects: Sand dune ecology -- South Africa Shore protection -- South Africa Coastal zone management -- South Africa Sand dunes -- South Africa Sand dune plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4185 , http://hdl.handle.net/10962/d1003753
- Description: The importance of understanding the ecological functioning of coastal dune systems is emphasized as being fundamental to the correct management of the dune landscape. Dune vegetation along the Eastern Cape coastline, from Cape St Francis in the west to Kei Mouth in the east was described in terms of the distribution and phytochorological affinities of the taxa. At a regional scale species distribution was strongly influenced by both the climate, particularly rainfall, and the phytochorological affinities of the taxa. Seven communities were defined using TWINSPAN, and the interrelationships between these communities in anyone area appeared to be linked to a successional gradient. Dune Slacks are thought to play a key role in this successional sequence, and a temporal study of this community led to a conceptual model of plant succession in these dunefields. Climate, particularly rainfall and wind, are major factors influencing plant succession. Wind-borne sand causes the slacks to migrate in an easterly direction under the influence of the predominantly westerly winds, although easterly winds, mainly in summer months may reverse these trends. Autogenic changes appeared to be important in this succession, and a comparative study of a good example of a primary succession at Mtunzini in Natal was undertaken to elucidate the main mechanism of change. Eight communities that were identified here were concluded to be distnbuted along a gradient of increasing age, with successional changes predictable, linear and directional. Species were grouped in distinct zones along the continuum and edaphic changes (decrease in soil pH, increase in organic matter and exchangeable bases) were related to the community based changes in species composition. The mechanism of change supported the facilitation model of plant succession which is a modification of the original Clementsian concept. Similar results were found in the Eastern Cape, but due to the harsh environment, multiple pathways of succession exist. Data from this study lent support to the model of plant succession developed earlier, and confinned that the dune slacks played an important role in this facilitation by acting as centres of diversity. The foredunes were found to have an indirect role in protecting these slacks from salt spray and sand movement. The central theme of the management studies was to investigate the ecological consequences of recreational pressure within the dune environment. Current levels of beach utilization at East London were lower than other beaches in South Africa, but a general trend of increasing utilization due to sociopolitical changes can be expected. The suitability of questionnaire surveys to assess aspects such as the adequacy of facilities, perceptual carrying capacity and the beach users opinion of natural vegetation and preference for particular beaches was demonstrated. The dune vegetation was found to be sensitive to human trampling, but at current levels, the ecological carrying capacity will not be exceeded since results of the aerial census counts and questionnaire survey revealed that few people entered sensitive zones such as the coastal forest. More detailed long term studies on the susceptibility of dune vegetation to both trampling and off-road vehicle impacts revealed a low resilience of dune plant communities to these effects. Although susceptibility differed between the three communities tested, generally the greatest amount of damage occurred after the first few passages, and vehicles caused a more significant decrease in height when compared to trampling. Recovery rates were slow and low levels of repeated damage were sufficient to retard or prevent the recovery of the plants. Stricter control of vehicle use on beaches is therefore required, and in high use zones the ecological carrying capacity should be increased by providing access tracks if possible, or if not possible, by restricting access. A historical account of the process of dune stabilization showed that although first initiated in 1845, indigenous species were only used in the past three decades. The use of alien species has resulted in problems such as a reduction in the ecological integrity and aesthetic appeal of coastal systems. The techniques applied in the stabilization of drift sands with indigenous vegetation have been successful, as revealed by a quantitative survey of 17 sites in the Eastern Cape. Sites were grouped by multivariate analysis on the basis of their species composition, and variability between sites was dependent on the types of species planted. Selection of suitable species is therefore important and is discussed with respect to their natural distribution along the coast. The long term objective of stabilization should be the creation of functional, diverse, aesthetic ecosystems, since the intrinsic and economic value of the dune landscape for tourism lies therein. However, detailed studies should be undertaken prior to implementing a manipulative process such as dune stabilization, since ecological processes may be disrupted. An understanding of such processes is therefore important if one wishes to effectively manage the dune landscape.
- Full Text:
- Date Issued: 1993
- Authors: Avis, Anthony Mark
- Date: 1993
- Subjects: Sand dune ecology -- South Africa Shore protection -- South Africa Coastal zone management -- South Africa Sand dunes -- South Africa Sand dune plants -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4185 , http://hdl.handle.net/10962/d1003753
- Description: The importance of understanding the ecological functioning of coastal dune systems is emphasized as being fundamental to the correct management of the dune landscape. Dune vegetation along the Eastern Cape coastline, from Cape St Francis in the west to Kei Mouth in the east was described in terms of the distribution and phytochorological affinities of the taxa. At a regional scale species distribution was strongly influenced by both the climate, particularly rainfall, and the phytochorological affinities of the taxa. Seven communities were defined using TWINSPAN, and the interrelationships between these communities in anyone area appeared to be linked to a successional gradient. Dune Slacks are thought to play a key role in this successional sequence, and a temporal study of this community led to a conceptual model of plant succession in these dunefields. Climate, particularly rainfall and wind, are major factors influencing plant succession. Wind-borne sand causes the slacks to migrate in an easterly direction under the influence of the predominantly westerly winds, although easterly winds, mainly in summer months may reverse these trends. Autogenic changes appeared to be important in this succession, and a comparative study of a good example of a primary succession at Mtunzini in Natal was undertaken to elucidate the main mechanism of change. Eight communities that were identified here were concluded to be distnbuted along a gradient of increasing age, with successional changes predictable, linear and directional. Species were grouped in distinct zones along the continuum and edaphic changes (decrease in soil pH, increase in organic matter and exchangeable bases) were related to the community based changes in species composition. The mechanism of change supported the facilitation model of plant succession which is a modification of the original Clementsian concept. Similar results were found in the Eastern Cape, but due to the harsh environment, multiple pathways of succession exist. Data from this study lent support to the model of plant succession developed earlier, and confinned that the dune slacks played an important role in this facilitation by acting as centres of diversity. The foredunes were found to have an indirect role in protecting these slacks from salt spray and sand movement. The central theme of the management studies was to investigate the ecological consequences of recreational pressure within the dune environment. Current levels of beach utilization at East London were lower than other beaches in South Africa, but a general trend of increasing utilization due to sociopolitical changes can be expected. The suitability of questionnaire surveys to assess aspects such as the adequacy of facilities, perceptual carrying capacity and the beach users opinion of natural vegetation and preference for particular beaches was demonstrated. The dune vegetation was found to be sensitive to human trampling, but at current levels, the ecological carrying capacity will not be exceeded since results of the aerial census counts and questionnaire survey revealed that few people entered sensitive zones such as the coastal forest. More detailed long term studies on the susceptibility of dune vegetation to both trampling and off-road vehicle impacts revealed a low resilience of dune plant communities to these effects. Although susceptibility differed between the three communities tested, generally the greatest amount of damage occurred after the first few passages, and vehicles caused a more significant decrease in height when compared to trampling. Recovery rates were slow and low levels of repeated damage were sufficient to retard or prevent the recovery of the plants. Stricter control of vehicle use on beaches is therefore required, and in high use zones the ecological carrying capacity should be increased by providing access tracks if possible, or if not possible, by restricting access. A historical account of the process of dune stabilization showed that although first initiated in 1845, indigenous species were only used in the past three decades. The use of alien species has resulted in problems such as a reduction in the ecological integrity and aesthetic appeal of coastal systems. The techniques applied in the stabilization of drift sands with indigenous vegetation have been successful, as revealed by a quantitative survey of 17 sites in the Eastern Cape. Sites were grouped by multivariate analysis on the basis of their species composition, and variability between sites was dependent on the types of species planted. Selection of suitable species is therefore important and is discussed with respect to their natural distribution along the coast. The long term objective of stabilization should be the creation of functional, diverse, aesthetic ecosystems, since the intrinsic and economic value of the dune landscape for tourism lies therein. However, detailed studies should be undertaken prior to implementing a manipulative process such as dune stabilization, since ecological processes may be disrupted. An understanding of such processes is therefore important if one wishes to effectively manage the dune landscape.
- Full Text:
- Date Issued: 1993
Collaborative teacher participation in curriculum development : a case study in junior secondary general science (January 1991-November 1991)
- Authors: Naidoo, Premnandh
- Date: 1993
- Subjects: Science -- Study and teaching (Secondary) -- South Africa Curriculum planning -- South Africa Environmental education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1451 , http://hdl.handle.net/10962/d1003332
- Description: This research report describes an investigation that involved the collaborative participation of teachers in the redevelopment of parts of the Junior Secondary General Science syllabus. The redevelopment tried to implement environmental education as an innovation. There are two central assumptions that the investigation has made. The first assumption is that the the present Junior Secondary General Science syllabus lacks environmental relevance and therefore the pupils are inadequately prepared to deal with environmental problems. The introduction of a curriculum innovation like environmental education has the potential to bring greater environmental relevance to the syllabus. The second is that such an innovation can be more successfully implemented at schools if it involves the collaborative participation of teachers in the redevelopment of the syllabus. This assumption is made since evidence suggests that curriculum change can be a process of social reconstructive process when it takes place in situ and where teachers and pupils reshape the curriculum in the classroom as the teaching and learning progresses. An action research approach was selected since it is compatible with collaborative teacher, participation in curriculum development. The research design involved three parallel case studies: 1. Clermont Zone, 2. Durban Teachers Centre, 3. Edgewood College. The research confirmed that the Junior Secondary General Science syllabus is perceived by teachers to lack environmental relevance; that teachers, while initially resisting participation in the curriculum development process, were willing to participate if it revolved around their curriculum problems. Significant features of collaborative teacher participation in curriculum development seem to be the co-creation of context by the teachers, the need for institutional support, the production of curriculum materials and the need for networking and intercontextual dialogue. Teachers initially had limited curriculum development skills which needed to be developed. This research process has implications for practical actions 'to enable' the transformation of existing curriculums, and assisting the development of a more democratic and effective education system.
- Full Text:
- Date Issued: 1993
- Authors: Naidoo, Premnandh
- Date: 1993
- Subjects: Science -- Study and teaching (Secondary) -- South Africa Curriculum planning -- South Africa Environmental education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1451 , http://hdl.handle.net/10962/d1003332
- Description: This research report describes an investigation that involved the collaborative participation of teachers in the redevelopment of parts of the Junior Secondary General Science syllabus. The redevelopment tried to implement environmental education as an innovation. There are two central assumptions that the investigation has made. The first assumption is that the the present Junior Secondary General Science syllabus lacks environmental relevance and therefore the pupils are inadequately prepared to deal with environmental problems. The introduction of a curriculum innovation like environmental education has the potential to bring greater environmental relevance to the syllabus. The second is that such an innovation can be more successfully implemented at schools if it involves the collaborative participation of teachers in the redevelopment of the syllabus. This assumption is made since evidence suggests that curriculum change can be a process of social reconstructive process when it takes place in situ and where teachers and pupils reshape the curriculum in the classroom as the teaching and learning progresses. An action research approach was selected since it is compatible with collaborative teacher, participation in curriculum development. The research design involved three parallel case studies: 1. Clermont Zone, 2. Durban Teachers Centre, 3. Edgewood College. The research confirmed that the Junior Secondary General Science syllabus is perceived by teachers to lack environmental relevance; that teachers, while initially resisting participation in the curriculum development process, were willing to participate if it revolved around their curriculum problems. Significant features of collaborative teacher participation in curriculum development seem to be the co-creation of context by the teachers, the need for institutional support, the production of curriculum materials and the need for networking and intercontextual dialogue. Teachers initially had limited curriculum development skills which needed to be developed. This research process has implications for practical actions 'to enable' the transformation of existing curriculums, and assisting the development of a more democratic and effective education system.
- Full Text:
- Date Issued: 1993
Community-based development organisations in the Eastern Cape: towards survival and sustainability
- Davies, Bill, Madlavu, Mzukisi
- Authors: Davies, Bill , Madlavu, Mzukisi
- Date: 1993
- Subjects: Community development corporations -- South Africa Community development -- Eastern Cape Community development -- Finance Community development -- Research -- South Africa Community development -- South Africa
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/1708 , vital:20218 , ISBN 0868102520
- Description: Community-Based Development Organisations (CBDOs) appear in many shapes and sizes, and a variety of (often confusing) terminology is used to describe them. The term CBDO is a generic one which refers to a broad class of organisations that are involved in one form or another of "community development" activities. Probably all CBDOs would describe themselves as non-governmental organisations (NGOs); and they could be service organisations, resource organisations (or both), or even welfare organisations. Some would see themselves as development agencies or as performing an advocacy/lobbying function on behalf of a more or less clearly defined constituency. Many CBDOs have a relatively narrow focus (for example, on some particular aspect of education or training - like literacy, teacher upgrading or technical skills)- whilst others pursue a broader range of activities associated with a spectrum of "community development" initiatives, projects or programmes. Much depends on the motivation for establishing a particular CBDO and its access to human and financial resources. They are part of the burgeoning Non- Profit Voluntary Sector in South Africa whose worth, in 1987, was estimated at a minimum of R2 billion - "and probably much more than that" , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1993
- Authors: Davies, Bill , Madlavu, Mzukisi
- Date: 1993
- Subjects: Community development corporations -- South Africa Community development -- Eastern Cape Community development -- Finance Community development -- Research -- South Africa Community development -- South Africa
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/1708 , vital:20218 , ISBN 0868102520
- Description: Community-Based Development Organisations (CBDOs) appear in many shapes and sizes, and a variety of (often confusing) terminology is used to describe them. The term CBDO is a generic one which refers to a broad class of organisations that are involved in one form or another of "community development" activities. Probably all CBDOs would describe themselves as non-governmental organisations (NGOs); and they could be service organisations, resource organisations (or both), or even welfare organisations. Some would see themselves as development agencies or as performing an advocacy/lobbying function on behalf of a more or less clearly defined constituency. Many CBDOs have a relatively narrow focus (for example, on some particular aspect of education or training - like literacy, teacher upgrading or technical skills)- whilst others pursue a broader range of activities associated with a spectrum of "community development" initiatives, projects or programmes. Much depends on the motivation for establishing a particular CBDO and its access to human and financial resources. They are part of the burgeoning Non- Profit Voluntary Sector in South Africa whose worth, in 1987, was estimated at a minimum of R2 billion - "and probably much more than that" , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1993
Conference on foreign portfolio investment - attendance list
- ANC
- Authors: ANC
- Date: July 1993
- Subjects: African National Congress (ANC)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149087 , vital:38803
- Full Text:
- Date Issued: July 1993
- Authors: ANC
- Date: July 1993
- Subjects: African National Congress (ANC)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/149087 , vital:38803
- Full Text:
- Date Issued: July 1993
Contemporary pollen spectra from the Natal Drakensberg and their relation to associated vegetation communities
- Authors: Hill, Trevor Raymond
- Date: 1993
- Subjects: Pollen -- South Africa -- KwaZulu-Natal Palynology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4199 , http://hdl.handle.net/10962/d1003768
- Description: The research focuses on the contemporary pollen rain-vegetation relationship for vegetation communities within the Natal Drakensberg, a region which is recognized as having the potential for extensive palynological investigations. The objective was to investigate the fundamental assumption underlying palynology, viz: that the pollen rain of a particular region is indicative or representative of the existing vegetation of that region. If the modern pollen rain is indicative of and/or distinctive for a particular vegetation community then the principle of methodological uniformitarianism can be applied, which states that the present day patterns and relationships can provide a factual basis for the reconstruction of the past through the extrapolation of modern analogues backwards in time. A vegetation survey was conducted in thirteen communities identified as pertinent to the research and a two-year modern pollen rain sampling programme was carried out, using both surface soil and pollen trap samples as a means of recording and quantifying the pollen rain. Once the necessary sample preparation and pollen counts had been performed, descriptive and numerical/statistical methods were employed to determine and describe the existing pollen-vegetation relationship. Descriptive analysis of the data sets was carried out with the aid of spectra depicted as rotated bar graphs and representing the relative percentage frequencies of the collected/counted taxa. Annual and seasonal pollen influx values were calculated and presented. Analysis of variance was applied to test various hypotheses related to sampling strategy and pollen influx variation. Statistical methods employed were two-way indicator species analysis (a classification analysis technique), detrended correspondence analysis and principal components analysis (ordination techniques), canonical correlation analysis (for data set association) and multiple discriminant analysis (for determination of vegetation zonal indices). The latter technique allowed for the probability of modern analogues to be assessed which are necessary for accurate interpretation of fossil pollen assemblages if the assumption under investigation is correct. The findings of the study were that the modern pollen rain-vegetation assumption holds true. Recommendations are put forward regarding future contemporary pollen studies with regards to the number of soil and pollen trap samples required, the magnitude of the pollen count and the numerical/statistical techniques most appropriate to clearly interpret the results. The conclusions are that future fossil pollen spectra can be expected to provide a good indication of former regional vegetation patterns for the study region. The study has extended the limited understanding of the contemporary pollen rain-vegetation relationship in South Africa and enables the interpretation of fossil pollen spectra to be carried out with greater confidence. This in turn lends greater credibility to possible Quaternary environmental change models required to help understand present and possible future environmental change.
- Full Text:
- Date Issued: 1993
- Authors: Hill, Trevor Raymond
- Date: 1993
- Subjects: Pollen -- South Africa -- KwaZulu-Natal Palynology -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4199 , http://hdl.handle.net/10962/d1003768
- Description: The research focuses on the contemporary pollen rain-vegetation relationship for vegetation communities within the Natal Drakensberg, a region which is recognized as having the potential for extensive palynological investigations. The objective was to investigate the fundamental assumption underlying palynology, viz: that the pollen rain of a particular region is indicative or representative of the existing vegetation of that region. If the modern pollen rain is indicative of and/or distinctive for a particular vegetation community then the principle of methodological uniformitarianism can be applied, which states that the present day patterns and relationships can provide a factual basis for the reconstruction of the past through the extrapolation of modern analogues backwards in time. A vegetation survey was conducted in thirteen communities identified as pertinent to the research and a two-year modern pollen rain sampling programme was carried out, using both surface soil and pollen trap samples as a means of recording and quantifying the pollen rain. Once the necessary sample preparation and pollen counts had been performed, descriptive and numerical/statistical methods were employed to determine and describe the existing pollen-vegetation relationship. Descriptive analysis of the data sets was carried out with the aid of spectra depicted as rotated bar graphs and representing the relative percentage frequencies of the collected/counted taxa. Annual and seasonal pollen influx values were calculated and presented. Analysis of variance was applied to test various hypotheses related to sampling strategy and pollen influx variation. Statistical methods employed were two-way indicator species analysis (a classification analysis technique), detrended correspondence analysis and principal components analysis (ordination techniques), canonical correlation analysis (for data set association) and multiple discriminant analysis (for determination of vegetation zonal indices). The latter technique allowed for the probability of modern analogues to be assessed which are necessary for accurate interpretation of fossil pollen assemblages if the assumption under investigation is correct. The findings of the study were that the modern pollen rain-vegetation assumption holds true. Recommendations are put forward regarding future contemporary pollen studies with regards to the number of soil and pollen trap samples required, the magnitude of the pollen count and the numerical/statistical techniques most appropriate to clearly interpret the results. The conclusions are that future fossil pollen spectra can be expected to provide a good indication of former regional vegetation patterns for the study region. The study has extended the limited understanding of the contemporary pollen rain-vegetation relationship in South Africa and enables the interpretation of fossil pollen spectra to be carried out with greater confidence. This in turn lends greater credibility to possible Quaternary environmental change models required to help understand present and possible future environmental change.
- Full Text:
- Date Issued: 1993
CWIU Congress resolutions 1993 - Draft
- Chemical Workers Industrial Union (CWIU)
- Authors: Chemical Workers Industrial Union (CWIU)
- Date: 1993
- Subjects: CWIU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/170159 , vital:41863
- Description: The CWIU recognises the need to develop a long term organisational vision, develop and implement creative and effective strategies, prioritise campaigns/activities in order to be able to sustain these, adapt and change by a process of restructuring, deal effectively with political and economic issues. Development of a long term Vision Congress reaffirms our objective of a socialist future Our programmes must therefore reflect this vision. The trade union movement as a working class organisation has a major role in any socialist programme. The labour movement must remain independent. This independence must not be compromised. Overall strategy for trade union movement The current direction of Cosatu towards so called "Strategic Unionism" must be thoroughly discussed. A progamme of discussion on this must be implemented in the Union. We confirm our belief in the following principles and any strategy must be based on these: worker control, accountability of leadership a combination of negotiations,mass action and struggle as the means to achieve our goals/demands.
- Full Text:
- Date Issued: 1993
- Authors: Chemical Workers Industrial Union (CWIU)
- Date: 1993
- Subjects: CWIU
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/170159 , vital:41863
- Description: The CWIU recognises the need to develop a long term organisational vision, develop and implement creative and effective strategies, prioritise campaigns/activities in order to be able to sustain these, adapt and change by a process of restructuring, deal effectively with political and economic issues. Development of a long term Vision Congress reaffirms our objective of a socialist future Our programmes must therefore reflect this vision. The trade union movement as a working class organisation has a major role in any socialist programme. The labour movement must remain independent. This independence must not be compromised. Overall strategy for trade union movement The current direction of Cosatu towards so called "Strategic Unionism" must be thoroughly discussed. A progamme of discussion on this must be implemented in the Union. We confirm our belief in the following principles and any strategy must be based on these: worker control, accountability of leadership a combination of negotiations,mass action and struggle as the means to achieve our goals/demands.
- Full Text:
- Date Issued: 1993
Data reduction techniques for Very Long Baseline Interferometric spectropolarimetry
- Authors: Kemball, Athol James
- Date: 1993
- Subjects: Very long baseline interferometry Radio interferometers Data reduction -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5457 , http://hdl.handle.net/10962/d1005242
- Description: This thesis reports the results of an investigation into techniques for the calibration and imaging of spectral line polarization observations in Very Long Baseline Interferometry (VLBI). A review is given of the instrumental and propagation effects which need to be removed in the course of calibrating such obervations, with particular reference to their polarization dependence. The removal of amplitude and phase errors and the determination of the instrumental feed response is described. The polarization imaging of such data is discussed with particular reference to the case of poorly sampled cross-polarization data. The software implementation of the algorithms within the Astronomical Image Processing System (AlPS) is discussed and the specific case of spectral line polarization reduction for data observed using the MK3 VLBI system is considered in detail. VLBI observations at two separate epochs of the 1612 MHz OH masers towards the source IRC+ 10420 are reduced as part of this work. Spectral line polarization maps of the source structure are presented, including a discussion of source morphology and variability. The source is sigmficantly circularly polarized at VLBI resolution, but does not display appreciable linear polarization. A proper motion study of the circumstellar envelope is presented, which supports an ellipsoidal kinematic model with anisotropic radial outflow. Kinematic modelling of the measured proper motions suggests a distance to the source of ~ 3 kpc. The cirumstellar magnetic field strength in the masing regions is determined as 1-3 mG, assuming Zeeman splitting as the polarization mechanism.
- Full Text:
- Date Issued: 1993
- Authors: Kemball, Athol James
- Date: 1993
- Subjects: Very long baseline interferometry Radio interferometers Data reduction -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5457 , http://hdl.handle.net/10962/d1005242
- Description: This thesis reports the results of an investigation into techniques for the calibration and imaging of spectral line polarization observations in Very Long Baseline Interferometry (VLBI). A review is given of the instrumental and propagation effects which need to be removed in the course of calibrating such obervations, with particular reference to their polarization dependence. The removal of amplitude and phase errors and the determination of the instrumental feed response is described. The polarization imaging of such data is discussed with particular reference to the case of poorly sampled cross-polarization data. The software implementation of the algorithms within the Astronomical Image Processing System (AlPS) is discussed and the specific case of spectral line polarization reduction for data observed using the MK3 VLBI system is considered in detail. VLBI observations at two separate epochs of the 1612 MHz OH masers towards the source IRC+ 10420 are reduced as part of this work. Spectral line polarization maps of the source structure are presented, including a discussion of source morphology and variability. The source is sigmficantly circularly polarized at VLBI resolution, but does not display appreciable linear polarization. A proper motion study of the circumstellar envelope is presented, which supports an ellipsoidal kinematic model with anisotropic radial outflow. Kinematic modelling of the measured proper motions suggests a distance to the source of ~ 3 kpc. The cirumstellar magnetic field strength in the masing regions is determined as 1-3 mG, assuming Zeeman splitting as the polarization mechanism.
- Full Text:
- Date Issued: 1993