The effects of graphene and other nanomaterials on the electrocatalytic behaviour of phthalocyanines
- Authors: Shumba, Munyaradzi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/37952 , vital:24712
- Description: Carbon based nanomaterials, gold nanorods and metallophthalocyanine nanoconjugates have been developed for electrocatalysis. Carbon based nanomaterials used are multiwalled carbon nanotubes, pristine graphene oxide nanosheets, nitrogen, boron, sulphur, phosphorus doped graphene oxide nanosheets. Cobalt phthalocyanine (CoPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPhPc), cobalt mono carboxyphenoxy phthalocyanine (CoMCPhPc) and cobalt tetra carboxyphenoxy phthalocyanine (CoTCPhPc) are the phthalocyanines employed in this work. Metallophthalocyanines were employed either in their bulk form or in their nanosized form. Electrode modification by these nanomaterials was either done sequentially, premixed or linked nanoconjugates. In all sequential modification, phthalocyanines were employed on top of other nanomaterials. Sequentially modified electrodes gave higher detection currents than both premixed and covalently bonded nanoconjugates. The nanomaterials reported here were characterised by transmission electron microscopy, Raman spectroscopy, time of flight secondary ion mass spectrometry, and X-ray diffraction among other techniques. The modified electrodes were further characterised by scanning electron microscopy, scanning electrochemical microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry, while square wave, linear scan and cyclic voltammetry, rotating disc electrode and chronoamperometry have been used to evaluate the electrocatalytic behaviour of the previously mentioned towards either oxidation or reduction of L-cysteine and/or hydrogen peroxide respectively. Generally, the nanoconjugates resulted in superior catalytic performance compared to the performance of individual nanomaterials. Zinc octacarboxy phthalocyanine (ZnOCPc) conjugated to either GONS or rGONS were employed to compare electrocatalytic detection of hydrogen peroxide to its luminescence sensing.
- Full Text:
- Date Issued: 2017
The effects of graphene and other nanomaterials on the electrocatalytic behaviour of phthalocyanines
- Authors: Shumba, Munyaradzi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/37952 , vital:24712
- Description: Carbon based nanomaterials, gold nanorods and metallophthalocyanine nanoconjugates have been developed for electrocatalysis. Carbon based nanomaterials used are multiwalled carbon nanotubes, pristine graphene oxide nanosheets, nitrogen, boron, sulphur, phosphorus doped graphene oxide nanosheets. Cobalt phthalocyanine (CoPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPc), cobalt tetra aminophenoxy phthalocyanine (CoTAPhPc), cobalt mono carboxyphenoxy phthalocyanine (CoMCPhPc) and cobalt tetra carboxyphenoxy phthalocyanine (CoTCPhPc) are the phthalocyanines employed in this work. Metallophthalocyanines were employed either in their bulk form or in their nanosized form. Electrode modification by these nanomaterials was either done sequentially, premixed or linked nanoconjugates. In all sequential modification, phthalocyanines were employed on top of other nanomaterials. Sequentially modified electrodes gave higher detection currents than both premixed and covalently bonded nanoconjugates. The nanomaterials reported here were characterised by transmission electron microscopy, Raman spectroscopy, time of flight secondary ion mass spectrometry, and X-ray diffraction among other techniques. The modified electrodes were further characterised by scanning electron microscopy, scanning electrochemical microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry, while square wave, linear scan and cyclic voltammetry, rotating disc electrode and chronoamperometry have been used to evaluate the electrocatalytic behaviour of the previously mentioned towards either oxidation or reduction of L-cysteine and/or hydrogen peroxide respectively. Generally, the nanoconjugates resulted in superior catalytic performance compared to the performance of individual nanomaterials. Zinc octacarboxy phthalocyanine (ZnOCPc) conjugated to either GONS or rGONS were employed to compare electrocatalytic detection of hydrogen peroxide to its luminescence sensing.
- Full Text:
- Date Issued: 2017
Effects of grazing and housing management systems on greenhouse gas emissions, blood profiles and meat quality of Nguni goats
- Authors: Tapiwa, Chikwanda Allen
- Date: 2016
- Subjects: Goats Goats -- Feeding and feeds Greenhouse gas mitigation , Grazing -- Environmental aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2314 , vital:27752
- Description: The broad objective of this study was to evaluate the effects of grazing and housing management systems on greenhouse gas emissions, blood profiles and meat quality of Nguni goats. A total of 64 castrated Nguni goats were used and a housing structure was designed to accommodate the goats as well as evaluate effects of type of floor on greenhouse gases, meat quality, blood metabolites and fatty acid profiles. In the first experiment: Forty-eight castrated Nguni goats, at 6-7 months old were used for herding (H) or tethering (T) management systems and randomly allocated to pens with earth (E) or slatted (S) floors. Gas sampling was done using static chambers and analysed using a SRI 8610C gas chromatography machine. The highest CH4 fluxes were from the manure of herded goats on earth floors (HE). The highest CO2 fluxes were from manure of herded goats that were housed on slatted floors (HS): The highest N2O fluxes were from the manure of tethered goats that were sheltered on slatted floors (TS). It was concluded from the first experiment that goat manure is an important source of GHG that is influenced by grazing and floor type management systems. The second experiment was done to evaluate greenhouse gas (GHG) emission from disused (DP) vs occupied goat pens (OP) with earth (EF) or slatted (SF) floors. Eight previously occupied pens were used in this study. Sixteen goats were randomly put in the pens labelled occupied pens with earth floors (OPEF) and occupied pens with slatted floors (OPSF) resulting in four goats per OP. There were month by pen use; month by floor type; and use by floor type interaction effects (P < 0.05) on CH4 production. Floor type, use (DP vs OP) and month affected (P < 0.05) CH4 production. Manure on earth floors of occupied pens (OPEF) emitted the highest (P < 0.05) methane followed by earth floors of disused pens (DPEF). The least CH4 was emitted from DPSF. There was pen use (DP vs OP) by floor type interaction effect (P < 0.05) on CO2 emission. Floor type and pen use affected (P < 0.05) CO2 production. Manure in occupied pens with slatted floors (OPSF) produced the highest CO2 and the least CO2 was from disused pens with slatted floors (DPSF). Floor type and month influenced (P < 0.05) N2O production. It was concluded that continued use of goat pens increased GHG emissions. However, disused goat pens with manure remain an important source of GHG as they continued to emit quantifiable levels of CH4, CO2 and N2O. The third experiment was done to determine the effects of grazing and housing management systems on the concentrations of blood metabolites, activity of creatine kinase, body weight (BW), body condition score (BCS) and carcass characteristics using 48 castrated Nguni goats. Tethered goats had higher (P<0.05): urea, creatinine, total protein, globulin concentrations and more activity of CK than herded goats. On the other hand, herded goats had higher (P<0.05) plasma glucose (H: 3.39±0.020 vs T: 3.23±0.020 mmol/L), serum albumin (H: 15.30±0.147 vs T: 14.82±0.144 g/L) concentration. It was concluded that serum concentrations of all the metabolites and the activity of CK were sensitive to grazing system. Herding of goats promoted more glucose concentration and preservation of muscle protein and hence superior body weights and BCS than tethered goats. The fourth experiment was done to determine the effects of grazing and housing management systems on the activity of creatine kinase (CK) and cortisol concentration, and chevon quality. Further, the effect of muscle type [Muscularis longissimus thoracis et. Lumborum (LTL) and triceps brachii (TB)] on chevon quality was also investigated. Forty eight castrated Nguni goats aged 6- 7 months were randomly allocated to tethering (n=24) and herding (n=24) treatments. Floor type affected meat (P<0.05) pH24. Tethered goats had higher (P < 0.05) L* and CL percent than herded goats. Muscle type had a significant influence (P < 0.05) on a*, WBSF and pH. It was observed and concluded that T resulted in higher L* and more CL percent whilst SF lowered the pH24 of chevon; at the same time meat from the TB muscle was more tender, despite having a higher pH24 and more CL percent relative to LTH cuts. The fifth experiment was done to determine the effect of grazing and floor type on fatty acid composition of chevon from tethered and herded Nguni goats. Floor type had no effect on fatty acid composition. Oleic, stearic, palmitic and linoleic were the major fatty acids. Chevon from tethered goats had higher (P < 0.05) proportions of long chain polyunsaturated fatty acids (PUFAs): eicosapentaenoic, docosapentaenoic, docosahexaenoic, conjugated linoleic acid (CLA) and more total SFA, total PUFA, total Omega- 6 and total omega 3 fatty acids than herded goats. On the other hand, chevon from herded goats had more (P < 0.05) C18:1c9, C18:2t9, 12 (n-6), C20:3c11, 14, 17 (n-3) and total MUFA than tethered goats. However, there was no difference (P > 0.05) in the PUFA: SFA and n-6/n-3 fatty acid ratios between the herded and tethered goats. It was concluded that tethering promoted higher proportions of beneficial PUFAs which were more in TB than LTH muscle. The overall conclusions from the whole study were that goat manure is an important source of GHG with high CH4 being emitted from earth floors of herded goats. High CO2 and N2O are emitted from SF of herded and tethered goats, respectively. There were no major differences in meat quality between herded and tethered goats. However, herding promoted more live weight gain than tethering. On the other hand, tethering promoted more beneficial fatty acids. Therefore depending on the objective of the enterprise, smallholder farmers can safely tether or herd their goats. Further, there is need to develop technologies to harness CH4 from goat manure.
- Full Text:
- Date Issued: 2016
- Authors: Tapiwa, Chikwanda Allen
- Date: 2016
- Subjects: Goats Goats -- Feeding and feeds Greenhouse gas mitigation , Grazing -- Environmental aspects
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2314 , vital:27752
- Description: The broad objective of this study was to evaluate the effects of grazing and housing management systems on greenhouse gas emissions, blood profiles and meat quality of Nguni goats. A total of 64 castrated Nguni goats were used and a housing structure was designed to accommodate the goats as well as evaluate effects of type of floor on greenhouse gases, meat quality, blood metabolites and fatty acid profiles. In the first experiment: Forty-eight castrated Nguni goats, at 6-7 months old were used for herding (H) or tethering (T) management systems and randomly allocated to pens with earth (E) or slatted (S) floors. Gas sampling was done using static chambers and analysed using a SRI 8610C gas chromatography machine. The highest CH4 fluxes were from the manure of herded goats on earth floors (HE). The highest CO2 fluxes were from manure of herded goats that were housed on slatted floors (HS): The highest N2O fluxes were from the manure of tethered goats that were sheltered on slatted floors (TS). It was concluded from the first experiment that goat manure is an important source of GHG that is influenced by grazing and floor type management systems. The second experiment was done to evaluate greenhouse gas (GHG) emission from disused (DP) vs occupied goat pens (OP) with earth (EF) or slatted (SF) floors. Eight previously occupied pens were used in this study. Sixteen goats were randomly put in the pens labelled occupied pens with earth floors (OPEF) and occupied pens with slatted floors (OPSF) resulting in four goats per OP. There were month by pen use; month by floor type; and use by floor type interaction effects (P < 0.05) on CH4 production. Floor type, use (DP vs OP) and month affected (P < 0.05) CH4 production. Manure on earth floors of occupied pens (OPEF) emitted the highest (P < 0.05) methane followed by earth floors of disused pens (DPEF). The least CH4 was emitted from DPSF. There was pen use (DP vs OP) by floor type interaction effect (P < 0.05) on CO2 emission. Floor type and pen use affected (P < 0.05) CO2 production. Manure in occupied pens with slatted floors (OPSF) produced the highest CO2 and the least CO2 was from disused pens with slatted floors (DPSF). Floor type and month influenced (P < 0.05) N2O production. It was concluded that continued use of goat pens increased GHG emissions. However, disused goat pens with manure remain an important source of GHG as they continued to emit quantifiable levels of CH4, CO2 and N2O. The third experiment was done to determine the effects of grazing and housing management systems on the concentrations of blood metabolites, activity of creatine kinase, body weight (BW), body condition score (BCS) and carcass characteristics using 48 castrated Nguni goats. Tethered goats had higher (P<0.05): urea, creatinine, total protein, globulin concentrations and more activity of CK than herded goats. On the other hand, herded goats had higher (P<0.05) plasma glucose (H: 3.39±0.020 vs T: 3.23±0.020 mmol/L), serum albumin (H: 15.30±0.147 vs T: 14.82±0.144 g/L) concentration. It was concluded that serum concentrations of all the metabolites and the activity of CK were sensitive to grazing system. Herding of goats promoted more glucose concentration and preservation of muscle protein and hence superior body weights and BCS than tethered goats. The fourth experiment was done to determine the effects of grazing and housing management systems on the activity of creatine kinase (CK) and cortisol concentration, and chevon quality. Further, the effect of muscle type [Muscularis longissimus thoracis et. Lumborum (LTL) and triceps brachii (TB)] on chevon quality was also investigated. Forty eight castrated Nguni goats aged 6- 7 months were randomly allocated to tethering (n=24) and herding (n=24) treatments. Floor type affected meat (P<0.05) pH24. Tethered goats had higher (P < 0.05) L* and CL percent than herded goats. Muscle type had a significant influence (P < 0.05) on a*, WBSF and pH. It was observed and concluded that T resulted in higher L* and more CL percent whilst SF lowered the pH24 of chevon; at the same time meat from the TB muscle was more tender, despite having a higher pH24 and more CL percent relative to LTH cuts. The fifth experiment was done to determine the effect of grazing and floor type on fatty acid composition of chevon from tethered and herded Nguni goats. Floor type had no effect on fatty acid composition. Oleic, stearic, palmitic and linoleic were the major fatty acids. Chevon from tethered goats had higher (P < 0.05) proportions of long chain polyunsaturated fatty acids (PUFAs): eicosapentaenoic, docosapentaenoic, docosahexaenoic, conjugated linoleic acid (CLA) and more total SFA, total PUFA, total Omega- 6 and total omega 3 fatty acids than herded goats. On the other hand, chevon from herded goats had more (P < 0.05) C18:1c9, C18:2t9, 12 (n-6), C20:3c11, 14, 17 (n-3) and total MUFA than tethered goats. However, there was no difference (P > 0.05) in the PUFA: SFA and n-6/n-3 fatty acid ratios between the herded and tethered goats. It was concluded that tethering promoted higher proportions of beneficial PUFAs which were more in TB than LTH muscle. The overall conclusions from the whole study were that goat manure is an important source of GHG with high CH4 being emitted from earth floors of herded goats. High CO2 and N2O are emitted from SF of herded and tethered goats, respectively. There were no major differences in meat quality between herded and tethered goats. However, herding promoted more live weight gain than tethering. On the other hand, tethering promoted more beneficial fatty acids. Therefore depending on the objective of the enterprise, smallholder farmers can safely tether or herd their goats. Further, there is need to develop technologies to harness CH4 from goat manure.
- Full Text:
- Date Issued: 2016
Production of Cydia pomonella granulovirus (CpGV) in a heteralogous host, Thaumatotibia Leucotreta (Meyrick) (False codling moth)
- Authors: Chambers, Craig Brian
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Codling moth -- South Africa , Apples -- Diseases and pests -- South Africa , Codling moth -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Biological pest control agents -- South Africa , Baculoviruses -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5935 , http://hdl.handle.net/10962/d1017906
- Description: Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.
- Full Text:
- Date Issued: 2015
- Authors: Chambers, Craig Brian
- Date: 2015
- Subjects: Cryptophlebia leucotreta -- South Africa , Codling moth -- South Africa , Apples -- Diseases and pests -- South Africa , Codling moth -- Biological control -- South Africa , Insect pests -- Biological control -- South Africa , Biological pest control agents -- South Africa , Baculoviruses -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5935 , http://hdl.handle.net/10962/d1017906
- Description: Cydia pomonella (Linnaeus) (Family: Tortricidae), the codling moth, is considered one of the most significant pests of apples and pears worldwide, causing up to 80% crop loss in orchards if no control measures are applied. Cydia pomonella is oligophagous feeding on a number of alternate hosts including quince, walnuts, apricots, peaches, plums and nectarines. Historically the control of this pest has been achieved with the use of various chemical control strategies which have maintained pest levels below the economic threshold at a relatively low cost to the grower. However, there are serious concerns surrounding the use of chemical insecticides including the development of resistance in insect populations, the banning of various insecticides, regulations for lowering of the maximum residue level and employee and consumer safety. For this reason, alternate measures of control are slowly being adopted by growers such as mating disruption, cultural methods and the use of baculovirus biopesticides as part of integrated pest management programmes. The reluctance of growers to accept baculovirus or other biological control products in the past has been due to questionable product quality and inconsistencies in their field performance. Moreover, the development and application of biological control products is more costly than the use of chemical alternatives. Baculoviruses are arthropod specific viruses that are highly virulent to a number of lepidopteran species. Due to the virulence and host specificity of baculoviruses, Cydia pomonella granulovirus has been extensively and successfully used as part of integrated pest management systems for the control of C. pomonella in Europe and around the world, including South Africa. Commercial formulations have been typically based on the Mexican strain of CpGV. However due to long-term multiple applications of CpGV and the reliance on CpGV in organic farming practices in Europe, resistance to the CpGV-M strain has developed in a number of field populations of C. pomonella. This study aimed to identify and characterize novel isolates of CpGV in South Africa and compare their virulence with the commercial standard CpGV-M. Secondly, since C. pomonella is difficult to culture on a large scale, an alternate method of CpGV production was investigated in order to determine if CpGV could be produced more efficiently and at a reduced cost without negatively impacting the quality of the product. Several isolates of CpGV were recovered either from field collected larvae or from a laboratory-reared C. pomonella colony. Characterisation of DNA profiles using a variety of restriction enzymes revealed that only a single isolate, CpGV-SA, was genetically different from the Mexican strain of the virus used in the commercially available CpGV based products in South Africa. In dose-response bioassays using CpGV-SA, LC₅₀ and LC₉₀ values for neonate C. pomonella larvae were 3.18 x 10³ OBs/ml and 7.33 x 10⁴ respectively. A comparison of these values with those of CpGV-M indicated no significant difference in the virulence of the two isolates under laboratory conditions. This is a first report of a genetically distinct CpGV isolate in South Africa. The biological activity and novelty of CpGV-SA makes this isolate a potentially important tool for CpGV resistance management in South Africa. In order to justify production of CpGV in an alternative host, studies on the comparative biological performance of C. pomonella and T. leucotreta based on oviposition, time to hatch, larval developmental times and rearing efficiency as well as production costs were performed. Thaumatotibia leucotreta was found to be more fecund and to have significantly shorter egg and larval developmental times. In addition, larval production per unit of artificial diet was significantly higher than for C. pomonella. This resulted in T. leucotreta being more cost effective to produce with implications for reduced insectary space, sanitation practices as well as the labour component of production. Virus yield data generated by inoculation both C. pomonella and T. leucotreta with nine concentrations of CpGV resulted in comparable virus yields, justifying the continuation of the research into production of CpGV in T. leucotreta. It was important to determine the LC and LT values required for mass production of CpGV in late instar T. leucotreta larvae. Dose- and time-response bioassays with CpGV-M were conducted on artificial diet to determine these values. Fourth instar LC₅₀ and LC₉₀ values were 5.96 x 10³ OBs/ml and 1.64 x 10⁵ OBs/ml respectively. LT50 and LT90 values were 81.10 hours and 88.58 hours respectively. Fifth instar LC₅₀ and LC₉₀ values were 6.88 x 10⁴ OBs/ml and 9.78 x 10⁶ OBs/ml respectively. LT₅₀ and LT₉₀ values were 111.56 hours and 137.57 hours respectively. Virus produced in fourth instar T. leucotreta larvae was bioassayed against C. pomonella neonate larvae and compared to CpGV-M to establish if production in the heterologous host negatively affected the virulence of the isolate. No significant difference in virulence was observed between virus produced in T. leucotreta and that produced in C. pomonella. The data generated in the bioassays was used in CpGV mass production trials to evaluate production. All production methods tested produced acceptable virus yields. To examine the quality of the virus product, genomic DNA was extracted from larval cadavers and subjected to REN analysis with HindIII. The resulting DNA profiles indicated that the virus product was contaminated with the homologous virus, CrleGV. Based on the above results, the use of T. leucotreta as an alternate host for the in vivo production of CpGV on a commercial basis is not at this stage viable and requires further investigation before this production methodology can be reliable used to produce CpGV. However, this study has shown that CpGV can be produced in a homologous host, T. leucotreta and significant strides have been made towards developing a set of quality control standards that are essential for further development of successful production methodology. Finally a novel isolate of CpGV has been identified with comparable virulence to the CpGV-M. This is an important finding as it has broad reaching implications for resistance management of CpGV products in South Africa.
- Full Text:
- Date Issued: 2015
A study of maximum and minimum operators with applications to piecewise linear payoff functions
- Authors: Seedat, Ebrahim
- Date: 2013
- Subjects: Options (Finance) Piecewise linear topology Geometry, Affine Riesz spaces Lattice theory Algebra, Boolean Pricing , Max and min operators
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:931 , http://hdl.handle.net/10962/d1001457
- Description: The payoff functions of contingent claims (options) of one variable are prominent in Financial Economics and thus assume a fundamental role in option pricing theory. Some of these payoff functions are continuous, piecewise-defined and linear or affine. Such option payoff functions can be analysed in a useful way when they are represented in additive, Boolean normal, graphical and linear form. The issue of converting such payoff functions expressed in the additive, linear or graphical form into an equivalent Boolean normal form, has been considered by several authors for more than half-a-century to better-understand the role of such functions. One aspect of our study is to unify the foregoing different forms of representation, by creating algorithms that convert a payoff function expressed in graphical form into Boolean normal form and then into the additive form and vice versa. Applications of these algorithms are considered in a general theoretical sense and also in the context of specific option contracts wherever relevant. The use of these algorithms have yielded easy computation of the area enclosed by the graph of various functions using min and max operators in several ways, which, in our opinion, are important in option pricing. To summarise, this study effectively dealt with maximum and minimum operators from several perspectives
- Full Text:
- Date Issued: 2013
- Authors: Seedat, Ebrahim
- Date: 2013
- Subjects: Options (Finance) Piecewise linear topology Geometry, Affine Riesz spaces Lattice theory Algebra, Boolean Pricing , Max and min operators
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:931 , http://hdl.handle.net/10962/d1001457
- Description: The payoff functions of contingent claims (options) of one variable are prominent in Financial Economics and thus assume a fundamental role in option pricing theory. Some of these payoff functions are continuous, piecewise-defined and linear or affine. Such option payoff functions can be analysed in a useful way when they are represented in additive, Boolean normal, graphical and linear form. The issue of converting such payoff functions expressed in the additive, linear or graphical form into an equivalent Boolean normal form, has been considered by several authors for more than half-a-century to better-understand the role of such functions. One aspect of our study is to unify the foregoing different forms of representation, by creating algorithms that convert a payoff function expressed in graphical form into Boolean normal form and then into the additive form and vice versa. Applications of these algorithms are considered in a general theoretical sense and also in the context of specific option contracts wherever relevant. The use of these algorithms have yielded easy computation of the area enclosed by the graph of various functions using min and max operators in several ways, which, in our opinion, are important in option pricing. To summarise, this study effectively dealt with maximum and minimum operators from several perspectives
- Full Text:
- Date Issued: 2013
Identifying expansive learning opportunities to foster a more sustainable food economy: a case study of Rhodes University dining halls
- Authors: Agbedahin, Adesuwa Vanessa
- Date: 2012
- Subjects: Food supply -- Education (Higher) -- South Africa -- Case studies Food industry and trade -- Education (Higher) -- Standards -- South Africa -- Case studies Food service employees -- Education (Higher) -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1560 , http://hdl.handle.net/10962/d1003442
- Description: This is a one year half thesis. This research was conducted within the context of the food services sector of Higher Education Institution dining halls and in the midst of the rising global call for food resource management and food waste reduction. The main aim of this research therefore was to identify opportunities for learning and change for a more sustainable food economy, contributing to Education for Sustainable Production and Consumption, and by further implication, Education for Sustainable Development. To achieve this aim, I used Cultural Historical Activity Theory as theoretical and methodological framework; drawing on the second and the third generations of this theory. Implicated in the above research approach is the identification of expansive learning opportunities from the surfacing of ‘tensions’ and ‘contradictions’. In this case study of the Rhodes University Campus Food Services, such tensions and contradictions inhibiting a more sustainable food economy, involving food waste production were identified. To narrow the scope of the study, one dining hall formed the focus of the case, with a two phased research approach whereby one research question and three goals were developed for each phase. The former being the exploration phase and the latter being the initial stages of the expansive phase. Methods used in line with the methodological framework included ten individual interviews with food producers (staff members), nine focus group discussions with food consumers (students), observations of the dining hall activities which lasted for over a month and two ‘Change Laboratory Workshops’. Some of the findings of this research are that food wastage cannot be addressed and appropriately curtailed without an intensive consideration of all the stages of food economy. Multiple contradictions and sources of tensions embedded in the Food Services Sector constituted major causes of food waste. Additionally, the lack of substantial food waste related teaching and learning activities, the presence of disputed rules, institutional structure and traditional practices within the Food Services all exacerbated the tensions and contradictions. More so, prioritizing some of this identified contradictions and tensions hindering a more sustainable food economy and relegating some as unimportant or nonurgent is unproductive. Finally, the non-existence of facilitated deliberation, consultation, dialogue, collaboration between food producers and food consumers has been identified as an obstacle to learning and institutional change. Recommendations abound in re-orienting, re-educating, and re-informing the constituents of the food economy. Re-visiting and revising of rules and regulations guiding conduct of students and kitchen staff members in the RU dining halls, as well as revision of existing learning support materials and mediating tools in use is needed. Recognition and consideration of the concerns and interests of students and kitchen staff members are also needed. Finally, there is a need to continue to address the tensions and contradictions identified in this case study, to further the Expansive Learning Process if a more sustainable food economy at Rhodes University is to be established.
- Full Text:
- Date Issued: 2012
- Authors: Agbedahin, Adesuwa Vanessa
- Date: 2012
- Subjects: Food supply -- Education (Higher) -- South Africa -- Case studies Food industry and trade -- Education (Higher) -- Standards -- South Africa -- Case studies Food service employees -- Education (Higher) -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1560 , http://hdl.handle.net/10962/d1003442
- Description: This is a one year half thesis. This research was conducted within the context of the food services sector of Higher Education Institution dining halls and in the midst of the rising global call for food resource management and food waste reduction. The main aim of this research therefore was to identify opportunities for learning and change for a more sustainable food economy, contributing to Education for Sustainable Production and Consumption, and by further implication, Education for Sustainable Development. To achieve this aim, I used Cultural Historical Activity Theory as theoretical and methodological framework; drawing on the second and the third generations of this theory. Implicated in the above research approach is the identification of expansive learning opportunities from the surfacing of ‘tensions’ and ‘contradictions’. In this case study of the Rhodes University Campus Food Services, such tensions and contradictions inhibiting a more sustainable food economy, involving food waste production were identified. To narrow the scope of the study, one dining hall formed the focus of the case, with a two phased research approach whereby one research question and three goals were developed for each phase. The former being the exploration phase and the latter being the initial stages of the expansive phase. Methods used in line with the methodological framework included ten individual interviews with food producers (staff members), nine focus group discussions with food consumers (students), observations of the dining hall activities which lasted for over a month and two ‘Change Laboratory Workshops’. Some of the findings of this research are that food wastage cannot be addressed and appropriately curtailed without an intensive consideration of all the stages of food economy. Multiple contradictions and sources of tensions embedded in the Food Services Sector constituted major causes of food waste. Additionally, the lack of substantial food waste related teaching and learning activities, the presence of disputed rules, institutional structure and traditional practices within the Food Services all exacerbated the tensions and contradictions. More so, prioritizing some of this identified contradictions and tensions hindering a more sustainable food economy and relegating some as unimportant or nonurgent is unproductive. Finally, the non-existence of facilitated deliberation, consultation, dialogue, collaboration between food producers and food consumers has been identified as an obstacle to learning and institutional change. Recommendations abound in re-orienting, re-educating, and re-informing the constituents of the food economy. Re-visiting and revising of rules and regulations guiding conduct of students and kitchen staff members in the RU dining halls, as well as revision of existing learning support materials and mediating tools in use is needed. Recognition and consideration of the concerns and interests of students and kitchen staff members are also needed. Finally, there is a need to continue to address the tensions and contradictions identified in this case study, to further the Expansive Learning Process if a more sustainable food economy at Rhodes University is to be established.
- Full Text:
- Date Issued: 2012
Regional application of the Pitman monthly rainfall-runoff model in Southern Africa incorporating uncertainty
- Authors: Kapangaziwiri, Evison
- Date: 2011
- Subjects: Water supply -- Africa, Southern Water supply -- Measurement -- Africa, Southern Hydrology -- Mathematical models -- Africa, Southern Hydrologic models Rain and rainfall -- Mathematical models -- Africa, Southern Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6037 , http://hdl.handle.net/10962/d1006178
- Description: Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework. , iText 1.4.6 (by lowagie.com)
- Full Text:
- Date Issued: 2011
- Authors: Kapangaziwiri, Evison
- Date: 2011
- Subjects: Water supply -- Africa, Southern Water supply -- Measurement -- Africa, Southern Hydrology -- Mathematical models -- Africa, Southern Hydrologic models Rain and rainfall -- Mathematical models -- Africa, Southern Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6037 , http://hdl.handle.net/10962/d1006178
- Description: Climate change and a growing demand for freshwater resources due to population increases and socio-economic changes will make water a limiting factor (in terms of both quantity and quality) in development. The need for reliable quantitative estimates of water availability cannot be over-emphasised. However, there is frequently a paucity of the data required for this quantification as many basins, especially in the developing world, are inadequately equipped with monitoring networks. Existing networks are also shrinking due mainly to shortages in human and financial resources. Over the past few decades mathematical models have been used to bridge the data gap by generating datasets for use in management and policy making. In southern Africa, the Pitman monthly rainfall-runoff model has enjoyed relatively popular use as a water resources estimation tool. However, it is acknowledged that models are abstractions of reality and the data used to drive them is imperfect, making the model outputs uncertain. While there is acknowledgement of the limitations of modelled data in the southern African region among water practitioners, there has been little effort to explicitly quantify and account for this uncertainty in water resources estimation tools and explore how it affects the decision making process. Uncertainty manifests itself in three major areas of the modelling chain; the input data used to force the model, the parameter estimation process and the model structural errors. A previous study concluded that the parameter estimation process for the Pitman model contributed more to the global uncertainty of the model than other sources. While the literature abounds with uncertainty estimation techniques, many of these are dependent on observations and are therefore unlikely to be easily applicable to the southern African region where there is an acute shortage of such data. This study focuses on two aspects of making hydrologic predictions in ungauged basins. Firstly, the study advocates the development of an a priori parameter estimation process for the Pitman model and secondly, uses indices of hydrological functional behaviour to condition and reduce predictive uncertainty in both gauged and ungauged basins. In this approach all the basins are treated as ungauged, while the historical records in the gauged basins are used to develop regional indices of expected hydrological behaviour and assess the applicability of these methods. Incorporating uncertainty into the hydrologic estimation tools used in southern Africa entails rethinking the way the uncertain results can be used in further analysis and how they will be interpreted by stakeholders. An uncertainty framework is proposed. The framework is made up of a number of components related to the estimation of the prior distribution of the parameters, used to generate output ensembles which are then assessed and constrained using regionalised indices of basin behavioural responses. This is premised on such indices being based on the best available knowledge covering different regions. This framework is flexible enough to be used with any model structure to ensure consistent and comparable results. While the aim is to eventually apply the uncertainty framework in the southern African region, this study reports on the preliminary work on the development and testing of the framework components based on South African basins. This is necessitated by the variations in the availability and quality of the data across the region. Uncertainty in the parameter estimation process was incorporated by assuming uncertainty in the physical and hydro-meteorological data used to directly quantify the parameter. This uncertainty was represented by the range of variability of these basin characteristics and probability distribution functions were developed to account for this uncertainty and propagate it through the estimation process to generate posterior distributions for the parameters. The results show that the framework has a great deal of potential but can still be improved. In general, the estimated uncertain parameters managed to produce hydrologically realistic model outputs capturing the expected regimes across the different hydro-climatic and geo-physical gradients examined. The regional relationships for the three indices developed and tested in this study were in general agreement with existing knowledge and managed to successfully provide a multi-criteria conditioning of the model output ensembles. The feedback loop included in the framework enabled a systematic re-examination of the estimation procedures for both the parameters and the indices when inconsistencies in the results were identified. This improved results. However, there is need to carefully examine the issues and problems that may arise within other basins outside South Africa and develop guidelines for the use of the framework. , iText 1.4.6 (by lowagie.com)
- Full Text:
- Date Issued: 2011
The role of APPRAISAL in the National Research Foundation (NRF) rating system evaluation and instruction in peer reviewer reports
- Authors: Marshall, Christine Louise
- Date: 2010
- Subjects: Veterinary medicine -- Research -- Evaluation Discourse analysis Politeness (Linguistics) Accreditation (Education) -- South Africa Quality assurance -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2356 , http://hdl.handle.net/10962/d1002638
- Description: This thesis reports on two aspects of interpersonal meaning in peer reviewer reports for eleven researchers in the Animal and Veterinary Sciences awarded NRF ratings in A1, B1, C1 and Y1 rating categories. These aspects are the evaluation of the researcher applying for a rating, and the instruction to the NRF as to the rating the researcher ought to receive. A full APPRAISAL Analysis (Martin & White 2005) complemented by an investigation of politeness strategies (Myers 1989) is used to analyse the reports and show how the various systems of interpersonal meaning co-function and to what effect. The analysis reveals that there are clear differences between the evaluative and instructive language used in the reports. Those for the A1 rated researchers are characterised by only positive evaluations of the applicant, frequently strengthened in terms of Graduation and contracted in terms of Engagement. Overall there is less Engagement and politeness in these reports rendering them more ‘factual’ than the reports for the other rating categories. The A1 rated researcher is therefore construed as being, incontestably, a leader in his/her field of research, worthy of a top rating. The reports for the B1 and C1 rated researchers are characterised by the increasing presence of negative evaluations. In addition, there are more instances of softened/downscaled Graduation, dialogic expansion and deference politeness, showing that there is more perceived contention about the evaluations made. The reports for the Y1 rated researchers (a category for young researchers) focus on the applicant’s demonstrated potential to become a leader in the field. In addition to a high incidence of negative evaluations, downscaled Graduation, dialogic expansion and deference politeness, the Y1 reports are also characterised by a high incidence of advice and suggestions from the reviewers concerning the applicant’s work and standing. At a broader level, the analysis reveals that the language used in the reports has a profound influence on the outcome of the rating process. The reports are crucial, not only for evaluating the applicant but, also, more subtly, in directing the NRF towards a specific rating category. It offers insights into what is valued in the scientific community, what is considered quality research, and what leads to international recognition. The research also adds uniquely to current thinking about the language of science and, more particularly, highlights the nuanced understanding of evaluative and instructive language in the reports that is possible if one draws on the full APPRAISAL framework, and insights into politeness behaviour.
- Full Text:
- Date Issued: 2010
- Authors: Marshall, Christine Louise
- Date: 2010
- Subjects: Veterinary medicine -- Research -- Evaluation Discourse analysis Politeness (Linguistics) Accreditation (Education) -- South Africa Quality assurance -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2356 , http://hdl.handle.net/10962/d1002638
- Description: This thesis reports on two aspects of interpersonal meaning in peer reviewer reports for eleven researchers in the Animal and Veterinary Sciences awarded NRF ratings in A1, B1, C1 and Y1 rating categories. These aspects are the evaluation of the researcher applying for a rating, and the instruction to the NRF as to the rating the researcher ought to receive. A full APPRAISAL Analysis (Martin & White 2005) complemented by an investigation of politeness strategies (Myers 1989) is used to analyse the reports and show how the various systems of interpersonal meaning co-function and to what effect. The analysis reveals that there are clear differences between the evaluative and instructive language used in the reports. Those for the A1 rated researchers are characterised by only positive evaluations of the applicant, frequently strengthened in terms of Graduation and contracted in terms of Engagement. Overall there is less Engagement and politeness in these reports rendering them more ‘factual’ than the reports for the other rating categories. The A1 rated researcher is therefore construed as being, incontestably, a leader in his/her field of research, worthy of a top rating. The reports for the B1 and C1 rated researchers are characterised by the increasing presence of negative evaluations. In addition, there are more instances of softened/downscaled Graduation, dialogic expansion and deference politeness, showing that there is more perceived contention about the evaluations made. The reports for the Y1 rated researchers (a category for young researchers) focus on the applicant’s demonstrated potential to become a leader in the field. In addition to a high incidence of negative evaluations, downscaled Graduation, dialogic expansion and deference politeness, the Y1 reports are also characterised by a high incidence of advice and suggestions from the reviewers concerning the applicant’s work and standing. At a broader level, the analysis reveals that the language used in the reports has a profound influence on the outcome of the rating process. The reports are crucial, not only for evaluating the applicant but, also, more subtly, in directing the NRF towards a specific rating category. It offers insights into what is valued in the scientific community, what is considered quality research, and what leads to international recognition. The research also adds uniquely to current thinking about the language of science and, more particularly, highlights the nuanced understanding of evaluative and instructive language in the reports that is possible if one draws on the full APPRAISAL framework, and insights into politeness behaviour.
- Full Text:
- Date Issued: 2010
Contributions to the use of microalgae in estuarine freshwater reserve determinations
- Authors: Snow, Gavin Charles
- Date: 2007
- Subjects: Microalgae -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10620 , http://hdl.handle.net/10948/709 , Microalgae -- South Africa , Estuarine ecology -- South Africa
- Description: The ecologist Garrett Hardin (1968) introduced a useful concept called the tragedy of the commons, which describes how ecological resources become threatened or lost. The term “commons” is based on the commons of old English villages and is symbolic of a resource that is shared by a group of people. If every person were to use each resource in a sustainable fashion it would be available in perpetuity. However, if people use more than their share they would only increase their personal wealth to the detriment of others. In addition, an increase in the population would mean that the size of each share would have to decrease to accommodate the larger number of people. As a result, resources are threatened by personal greed and uncontrolled population growth. Freshwater is an example of a common resource that is under threat in South Africa where the average annual rainfall is less than 60 percent of the global average (Mukheibir & Sparks 2006). The increasing demands for freshwater as well as its eutrophication are major concerns with regards to estuarine health, environmental resource management and human health. The correct management of water is necessary to ensure that it is utilised in a sustainable manner. The National Water Act (No. 36 of 1998) has provided the rights to water for basic human needs and for sustainable ecological function; the Basic Human Needs Reserve and Ecological Reserve are both provided as a right in law. The amount of water necessary for an estuary to retain an acceptable ecological status, known as the Estuarine Ecological Reserve, is determined through the implementation of procedures (rapid, intermediate or comprehensive) compiled by the Department of Water Affairs and Forestry (1999) in its Resource Directed Measures (RDM) for the Protection of Water Resources. The impact of restricted flow on estuaries can be reduced by manipulating the water released from impoundments, the regulation of water abstractions within the river catchment or both (Hirji et al. 2002). The reserve assessment method is designed to evaluate ecosystem requirements by employing groups of specialists from different disciplines. In South Africa, this includes hydrologists, sedimentologists, water chemists and biologists (including microalgae specialists). The use of microalgae in ecological assessments has largely been based on research that was initiated at the Nelson Mandela Metropolitan University (formerly University of Port Elizabeth) and subsequently at Rhodes University (Grahamstown) and the University of KwaZulu Natal (Durban). The microalgal research can be divided into two main focus areas; phytoplankton and benthic microalgae
- Full Text:
- Date Issued: 2007
- Authors: Snow, Gavin Charles
- Date: 2007
- Subjects: Microalgae -- South Africa , Estuarine ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10620 , http://hdl.handle.net/10948/709 , Microalgae -- South Africa , Estuarine ecology -- South Africa
- Description: The ecologist Garrett Hardin (1968) introduced a useful concept called the tragedy of the commons, which describes how ecological resources become threatened or lost. The term “commons” is based on the commons of old English villages and is symbolic of a resource that is shared by a group of people. If every person were to use each resource in a sustainable fashion it would be available in perpetuity. However, if people use more than their share they would only increase their personal wealth to the detriment of others. In addition, an increase in the population would mean that the size of each share would have to decrease to accommodate the larger number of people. As a result, resources are threatened by personal greed and uncontrolled population growth. Freshwater is an example of a common resource that is under threat in South Africa where the average annual rainfall is less than 60 percent of the global average (Mukheibir & Sparks 2006). The increasing demands for freshwater as well as its eutrophication are major concerns with regards to estuarine health, environmental resource management and human health. The correct management of water is necessary to ensure that it is utilised in a sustainable manner. The National Water Act (No. 36 of 1998) has provided the rights to water for basic human needs and for sustainable ecological function; the Basic Human Needs Reserve and Ecological Reserve are both provided as a right in law. The amount of water necessary for an estuary to retain an acceptable ecological status, known as the Estuarine Ecological Reserve, is determined through the implementation of procedures (rapid, intermediate or comprehensive) compiled by the Department of Water Affairs and Forestry (1999) in its Resource Directed Measures (RDM) for the Protection of Water Resources. The impact of restricted flow on estuaries can be reduced by manipulating the water released from impoundments, the regulation of water abstractions within the river catchment or both (Hirji et al. 2002). The reserve assessment method is designed to evaluate ecosystem requirements by employing groups of specialists from different disciplines. In South Africa, this includes hydrologists, sedimentologists, water chemists and biologists (including microalgae specialists). The use of microalgae in ecological assessments has largely been based on research that was initiated at the Nelson Mandela Metropolitan University (formerly University of Port Elizabeth) and subsequently at Rhodes University (Grahamstown) and the University of KwaZulu Natal (Durban). The microalgal research can be divided into two main focus areas; phytoplankton and benthic microalgae
- Full Text:
- Date Issued: 2007
The development of a self-disintegrating core-body for use in an art bronze-casting foundry which employs the ceramic-shell investment technique
- Authors: Lomax, Lawrence Talbot
- Date: 2004
- Subjects: Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8499 , http://hdl.handle.net/10948/219 , Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Description: The development of a disintegrating core-body for use in an art bronze foundry, which employs the ceramic shell investment process, begins with an investigation of four principal materials that will constitute the core formula. The specifications for the disintegration of the designed core-body formula fall within the parameters that are normally set and used in the ceramic shell art bronze casting process. The raison d’ être for the disintegrating formula is based on the premise that cement breaks down (spalling) after being subjected to heat above a certain temperature. It was shown that pure cement in the form of naked test bars 100 mm x 20 mm x 20 mm does indeed break down into separate pieces when fired to and above 9000C; where 9000C is the lowest recommended temperature required for sintering the ceramic shell investment mould. The addition of calcium carbonate to pure cement in the form of naked test bars, produced a more unified formula that did not break into separate pieces when fired to 9450C. However this combination of cement and calcium carbonate had a slow setting time of 12 hours and a shrinkage value of 2,3%, which were both above the parameters being sought for a quick-setting formula with a shrinkage value of below 1%. The combination of cement, plaster of paris and silica produced formulae that set within six hours and had shrinkage values of less than 1% but did not disintegrate within 72 hours. It was only after the addition of calcium carbonate to the these mixes that formulae resulted that set within six hours, had relatively low shrinkage values and showed signs of breaking up after 60 hours. It was further shown that by altering the ratios of cement, plaster of paris, calcium carbonate and silica, that the parameters for quick-setting formulae with shrinkage values of 1% and below, that also disintegrated within 55 hours, could be achieved. xvi It was also proved by subjecting these formulae to higher relative humidity conditions that the disintegrating times could be reduced and brought to below 48 hours. Selected formulae were then subjected to temperatures of between 9000C and 10000C. It was found that as the temperatures were increased so the disintegration times were reduced and were even further reduced under higher relative humidity conditions. It was found from the above experiments that the selected formula determined to be suitable in all respects as a disintegrating core-body was too difficult to remove from the hollow bronze cast when subjected to an actual bronze pour. Further experimentation using increased proportions of silica in the formula resulted in a final core-body that could be quickly and easily removed from its bronze cast as soon as the core-body had cooled to room temperature. The selected core-body formula (F21D) that was used in the final set of bronze casting procedures was found to function optimally when fired to a temperature of 9000C and could be quickly and easily removed from the bronze casts leaving a clean inner bronze surface, free from any remnants of the fired core. The document concludes by recording the delimitations and advantages of the final core-body formula F21D, as well as making recommendations based on these parameters for further study relating to disintegrating core-body formulations.
- Full Text:
- Date Issued: 2004
- Authors: Lomax, Lawrence Talbot
- Date: 2004
- Subjects: Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:8499 , http://hdl.handle.net/10948/219 , Sculpture -- Technique , Bronze founding , Precision casting , Shell molding (Founding)
- Description: The development of a disintegrating core-body for use in an art bronze foundry, which employs the ceramic shell investment process, begins with an investigation of four principal materials that will constitute the core formula. The specifications for the disintegration of the designed core-body formula fall within the parameters that are normally set and used in the ceramic shell art bronze casting process. The raison d’ être for the disintegrating formula is based on the premise that cement breaks down (spalling) after being subjected to heat above a certain temperature. It was shown that pure cement in the form of naked test bars 100 mm x 20 mm x 20 mm does indeed break down into separate pieces when fired to and above 9000C; where 9000C is the lowest recommended temperature required for sintering the ceramic shell investment mould. The addition of calcium carbonate to pure cement in the form of naked test bars, produced a more unified formula that did not break into separate pieces when fired to 9450C. However this combination of cement and calcium carbonate had a slow setting time of 12 hours and a shrinkage value of 2,3%, which were both above the parameters being sought for a quick-setting formula with a shrinkage value of below 1%. The combination of cement, plaster of paris and silica produced formulae that set within six hours and had shrinkage values of less than 1% but did not disintegrate within 72 hours. It was only after the addition of calcium carbonate to the these mixes that formulae resulted that set within six hours, had relatively low shrinkage values and showed signs of breaking up after 60 hours. It was further shown that by altering the ratios of cement, plaster of paris, calcium carbonate and silica, that the parameters for quick-setting formulae with shrinkage values of 1% and below, that also disintegrated within 55 hours, could be achieved. xvi It was also proved by subjecting these formulae to higher relative humidity conditions that the disintegrating times could be reduced and brought to below 48 hours. Selected formulae were then subjected to temperatures of between 9000C and 10000C. It was found that as the temperatures were increased so the disintegration times were reduced and were even further reduced under higher relative humidity conditions. It was found from the above experiments that the selected formula determined to be suitable in all respects as a disintegrating core-body was too difficult to remove from the hollow bronze cast when subjected to an actual bronze pour. Further experimentation using increased proportions of silica in the formula resulted in a final core-body that could be quickly and easily removed from its bronze cast as soon as the core-body had cooled to room temperature. The selected core-body formula (F21D) that was used in the final set of bronze casting procedures was found to function optimally when fired to a temperature of 9000C and could be quickly and easily removed from the bronze casts leaving a clean inner bronze surface, free from any remnants of the fired core. The document concludes by recording the delimitations and advantages of the final core-body formula F21D, as well as making recommendations based on these parameters for further study relating to disintegrating core-body formulations.
- Full Text:
- Date Issued: 2004
An inquiry into the incorporation of a multicultural approach in contemporary textbooks in South Africa
- Authors: Sharma, Anjali
- Date: 2001
- Subjects: Multicultural education -- South Africa Multicultural education -- Curricula Textbooks -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1579 , http://hdl.handle.net/10962/d1003461
- Description: During the past few decades a substantial body of research has emerged in western as well as the developing nations studying the racial bias in children's texts. However, it is only recently in South Africa, with the ascendance of the ANC government, that interest has been focused on eliminating apartheid values and on promoting multicultural tenets in the school curriculum. It is undeniable that the concept of multiculturalism has been severely stigmatised in the South African educational context. Anxieties have been expressed about embracing the discourse of multicultural education within the educational system based on fears that, like the previous educational system, it too will perpetuate group differences. Nevertheless, in recent years, a clear consensus view has emerged that the implementation of multicultural education is imperative if the goal of a rainbow South Africa is to be realised. Against this background, the present study attempts to study the incorporation of a multicultural approach into contemporary textbooks. To realise this aim I selected a sample of four textbooks, one from each of the major disciplines (science, English, geography and history), and SUbjected the texts and pictures from each to content analysis. The findings of this study suggest that a multicultural approach shall at least for the foreseeable future remain a central feature of learning materials produced for the new South African curricula. The findings indicate that multicultural aspects predominate in the texts as compared to other ideologies. This applies to both text content and illustrations. Contrary to the researcher's initial expectation, however, the texts also reveal a strong tendency towards Eurocentric and patriarchal approaches. This research does not conform to traditional, 'scientific' criteria of validity and reliability; it seeks only to investigate textbook material in more depth and thereby contribute to a more comprehensive understanding of the extent to which the texts subscribe to a multicultural approach. Such understanding may help both educationalists and authors in their evaluation of existing textbook material, and in the production of new texts which reflect the reality of South Africa as a multicultural society.
- Full Text:
- Date Issued: 2001
- Authors: Sharma, Anjali
- Date: 2001
- Subjects: Multicultural education -- South Africa Multicultural education -- Curricula Textbooks -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1579 , http://hdl.handle.net/10962/d1003461
- Description: During the past few decades a substantial body of research has emerged in western as well as the developing nations studying the racial bias in children's texts. However, it is only recently in South Africa, with the ascendance of the ANC government, that interest has been focused on eliminating apartheid values and on promoting multicultural tenets in the school curriculum. It is undeniable that the concept of multiculturalism has been severely stigmatised in the South African educational context. Anxieties have been expressed about embracing the discourse of multicultural education within the educational system based on fears that, like the previous educational system, it too will perpetuate group differences. Nevertheless, in recent years, a clear consensus view has emerged that the implementation of multicultural education is imperative if the goal of a rainbow South Africa is to be realised. Against this background, the present study attempts to study the incorporation of a multicultural approach into contemporary textbooks. To realise this aim I selected a sample of four textbooks, one from each of the major disciplines (science, English, geography and history), and SUbjected the texts and pictures from each to content analysis. The findings of this study suggest that a multicultural approach shall at least for the foreseeable future remain a central feature of learning materials produced for the new South African curricula. The findings indicate that multicultural aspects predominate in the texts as compared to other ideologies. This applies to both text content and illustrations. Contrary to the researcher's initial expectation, however, the texts also reveal a strong tendency towards Eurocentric and patriarchal approaches. This research does not conform to traditional, 'scientific' criteria of validity and reliability; it seeks only to investigate textbook material in more depth and thereby contribute to a more comprehensive understanding of the extent to which the texts subscribe to a multicultural approach. Such understanding may help both educationalists and authors in their evaluation of existing textbook material, and in the production of new texts which reflect the reality of South Africa as a multicultural society.
- Full Text:
- Date Issued: 2001
Metabolic responses in melanoma cells to combined nutrient supplementation
- Authors: Midgley, Nicola-Ann
- Date: 1997
- Subjects: Melanoma Tumors -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4036 , http://hdl.handle.net/10962/d1004096
- Description: This thesis examined the effect and biochemical mechanism by which combined vitamin E and C supplementation may influence tumour cell growth. The study initially addressed the effect of combined vitamin E succinate and Asc supplementation over a nutritional concentration range (5- 20μg/ml) and (25-50μg/ml) respectively, on the in vitro growth of non-malignant LLCMK and malignant BL6 cells. Supplementation of BL6 and LLCMK cells with combined vitamin E succinate and ascorbic acid, resulted in no significant increasing or decreasing trend in LLCMK cell growth, while in BL6 cells a significant decrease in cell growth was observed at all combined vitamin concentrations. It has been suggested that these vitamins may act synergistically to inhibit tumour cell growth through their antioxidant properties in quenching free radicals and lipid peroxidation and furthermore through their modulation of the activities of various enzymes and metabolites in the eicosanoid pathway. This study consequently investigated the effects of combined vitamin E succinate and ascorbic acid supplementation on these parameters. Throughout this study, emphasis was placed on the BL6 melanoma cells, as combined vitamin E succinate and ascorbic acid supplementation did not significantly affect growth or levels of secondary metabolites in the non-malignant LLCMK cells. Combined vitamin E succinate and ascorbic acid supplementation of BL6 cells resulted in a marked but non significant increase in free radical and a significant increase in lipid peroxidation levels. This prooxidant effect was accompanied by a significant decrease in BL6 cell growth, suggesting that the growth inhibitory effects of combined vitainin E succinate and ascorbic acid on BL6 cells in vitro was not mediated through their synergistic antioxidant properties. Vitamin E succinate is a nonphysiological antioxidant in its esterified form, hence cleavage of the succinate group must occur in order for ascorbic acid to interact with the free alcohol, vitamin E. The inability of combined vitamin E succinate and ascorbic acid to reduce free radicals and lipid peroxidation levels within BL6 cells may not be due to their ineffectiveness as antioxidants but rather the presence of other contributing factors which influence the oxidation state within the BL6 cells. Vitamin E is believed to modulate membrane-bound enzymes through membrane stabilization. Furthermore, the stabilizing effect of vitamin E may be enhanced by the ascorbic acid-sparing effect of vitamin E. Hence, this study investigated the effect of combined vitamin E succinate and ascorbic acid in modulating the activity of various enzymes and secondary messengers in the eicosanoid pathway. Supplementation with combined vitamin E succinate (5-20μg/ml) and ascorbic acid (25-50μg/ml) resulted in significant increases in phospholipase A₂, 5-lipoxygenase, cyclooxygenase and adenyl ate cyclase activity, with a significant decrease in BL6 cell growth. The possible synergistic action of these vitamins in terms of modulating membrane-bound enzymes was further substantiated by uptake and cellular distribution studies. Vitamin E succinate and vitamin E in the membrane fraction increased significantly compared to control cultures, while ascorbic acid levels were significantly higher in the stroma fraction when compared to membrane fractions. Consequently, another factor accounting for increased activities of phospholipase A2, 5-lipoxygenase and adenylate cyclase activities as a result of vitamin supplementation in BL6 cells may be an increased availability of Ca²+. Supplementation of BL6 cells with combined vitamin E succinate and ascorbic acid resulted in significant increases in intracellular Ca²+ levels at all combined vitamin groups. Furthermore, this increase in intracellular Ca²+ was positively correlated with cl1anges of the above-mentioned enzyme activities. Within the eicosanoid pathway, the rate of prostaglandin synthesis is regulated by phospholipase A₂ activity and arachidonic acid release, and the net prostaglandin production is dependent on cyclooxygenase activity, hence the effects of combined vitamin E succinate and ascorbic acid on arachidonic acid composition and prostaglandin production within BL6 cells was determined. The percentage arachidonic acid composition of the BL6 cells was elevated and inversely related to cell growth following combined vitamin E succinate and ascorbic acid supplementation. Prostaglandin E₂ and prostaglandin I₂ levels increased significantly, while those of prostaglandin D2 and prostaglandin F₂α increased markedly following supplementation of combined vitamin E succinate and ascorbic acid. These increases in prostaglandin levels were inversely related to BL6 cell growth, suggesting that the prostaglandins were involved in negative regulation of BL6 cell growth. When comparing the levels of prostaglandins, prostaglandin E2 levels were significantly higher when compared to prostaglandin D₂, prostaglandin F₂α and prostaglandin I₂ suggesting that vitamin E₂ succinate and ascorbic acid effects were mediated primarily through an increase in prostaglandin E2. Hence, prostaglandin E2 levels in combined vitamin E succinate and ascorbic acid appeared to be dependent on the amount of precursor present and the activity of its synthetic enzymes. This was confirmed when BL6 cells were supplemented with arachidonic acid. Arachidonic acid had an inhibitory effect on BL6 cell growth and also stimulated prostaglandin E₂ production. Prostaglandin E₂ levels are in turn believed to modulate adenylate cyclase activity in BL6 cells, hence it is reasonable to conclude that adenylate cyclase activity is dependent on prostaglandin E₂ levels. Combined vitamin E succinate and Asc supplementation to BL6 cells resulted in significant increases in adenyl ate cyclase and cyclic adenosine monophosphate, which again correlated with a significant decrease in cell growth. As cyclic adenosine monophosphate has a regulatory role in the cell cycle this study suggested that the effect of combined vitamin E succinate and ascorbic acid supplementation was mediated through the final effect provided by the second messenger, cyclic adenosine monophosphate. This was confirmed when BL6 cells were supplemented with dexamethasone, a phospholipase A₂ inhibitor. This treatment rsulted in combined vitamin E succinate and ascorbic acid having no inhibitory effect on BL6 cell growth. Cyclooxygenase activity, prostaglandin E₂ levels, adenylate cyclase activity and cyclic adenosine monophosphate levels were significantly lower in dexamethasone-treated cells compared to non-treated dexamethasone cultures. The reason for the increased free radical and lipid peroxidation levels in BL6 cells was further investigated. Cyclooxygenase enzymes are believed to generate free radical species during catalytic activity. Analysis of free radical and lipid peroxidation levels following supplementation with dexamethasone revealed markedly lower free radical and significantly lower lipid peroxidation levels in comparison with control cultures and non dexamethasone-treated cultures. These results suggest that the observed increases in free radical and lipid peroxidation levels in BL6 cells supplemented with combined vitamin E succinate and ascorbic acid were indirectly due to the increase in cyclooxygenase activity in these cells.
- Full Text:
- Date Issued: 1997
- Authors: Midgley, Nicola-Ann
- Date: 1997
- Subjects: Melanoma Tumors -- Growth
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4036 , http://hdl.handle.net/10962/d1004096
- Description: This thesis examined the effect and biochemical mechanism by which combined vitamin E and C supplementation may influence tumour cell growth. The study initially addressed the effect of combined vitamin E succinate and Asc supplementation over a nutritional concentration range (5- 20μg/ml) and (25-50μg/ml) respectively, on the in vitro growth of non-malignant LLCMK and malignant BL6 cells. Supplementation of BL6 and LLCMK cells with combined vitamin E succinate and ascorbic acid, resulted in no significant increasing or decreasing trend in LLCMK cell growth, while in BL6 cells a significant decrease in cell growth was observed at all combined vitamin concentrations. It has been suggested that these vitamins may act synergistically to inhibit tumour cell growth through their antioxidant properties in quenching free radicals and lipid peroxidation and furthermore through their modulation of the activities of various enzymes and metabolites in the eicosanoid pathway. This study consequently investigated the effects of combined vitamin E succinate and ascorbic acid supplementation on these parameters. Throughout this study, emphasis was placed on the BL6 melanoma cells, as combined vitamin E succinate and ascorbic acid supplementation did not significantly affect growth or levels of secondary metabolites in the non-malignant LLCMK cells. Combined vitamin E succinate and ascorbic acid supplementation of BL6 cells resulted in a marked but non significant increase in free radical and a significant increase in lipid peroxidation levels. This prooxidant effect was accompanied by a significant decrease in BL6 cell growth, suggesting that the growth inhibitory effects of combined vitainin E succinate and ascorbic acid on BL6 cells in vitro was not mediated through their synergistic antioxidant properties. Vitamin E succinate is a nonphysiological antioxidant in its esterified form, hence cleavage of the succinate group must occur in order for ascorbic acid to interact with the free alcohol, vitamin E. The inability of combined vitamin E succinate and ascorbic acid to reduce free radicals and lipid peroxidation levels within BL6 cells may not be due to their ineffectiveness as antioxidants but rather the presence of other contributing factors which influence the oxidation state within the BL6 cells. Vitamin E is believed to modulate membrane-bound enzymes through membrane stabilization. Furthermore, the stabilizing effect of vitamin E may be enhanced by the ascorbic acid-sparing effect of vitamin E. Hence, this study investigated the effect of combined vitamin E succinate and ascorbic acid in modulating the activity of various enzymes and secondary messengers in the eicosanoid pathway. Supplementation with combined vitamin E succinate (5-20μg/ml) and ascorbic acid (25-50μg/ml) resulted in significant increases in phospholipase A₂, 5-lipoxygenase, cyclooxygenase and adenyl ate cyclase activity, with a significant decrease in BL6 cell growth. The possible synergistic action of these vitamins in terms of modulating membrane-bound enzymes was further substantiated by uptake and cellular distribution studies. Vitamin E succinate and vitamin E in the membrane fraction increased significantly compared to control cultures, while ascorbic acid levels were significantly higher in the stroma fraction when compared to membrane fractions. Consequently, another factor accounting for increased activities of phospholipase A2, 5-lipoxygenase and adenylate cyclase activities as a result of vitamin supplementation in BL6 cells may be an increased availability of Ca²+. Supplementation of BL6 cells with combined vitamin E succinate and ascorbic acid resulted in significant increases in intracellular Ca²+ levels at all combined vitamin groups. Furthermore, this increase in intracellular Ca²+ was positively correlated with cl1anges of the above-mentioned enzyme activities. Within the eicosanoid pathway, the rate of prostaglandin synthesis is regulated by phospholipase A₂ activity and arachidonic acid release, and the net prostaglandin production is dependent on cyclooxygenase activity, hence the effects of combined vitamin E succinate and ascorbic acid on arachidonic acid composition and prostaglandin production within BL6 cells was determined. The percentage arachidonic acid composition of the BL6 cells was elevated and inversely related to cell growth following combined vitamin E succinate and ascorbic acid supplementation. Prostaglandin E₂ and prostaglandin I₂ levels increased significantly, while those of prostaglandin D2 and prostaglandin F₂α increased markedly following supplementation of combined vitamin E succinate and ascorbic acid. These increases in prostaglandin levels were inversely related to BL6 cell growth, suggesting that the prostaglandins were involved in negative regulation of BL6 cell growth. When comparing the levels of prostaglandins, prostaglandin E2 levels were significantly higher when compared to prostaglandin D₂, prostaglandin F₂α and prostaglandin I₂ suggesting that vitamin E₂ succinate and ascorbic acid effects were mediated primarily through an increase in prostaglandin E2. Hence, prostaglandin E2 levels in combined vitamin E succinate and ascorbic acid appeared to be dependent on the amount of precursor present and the activity of its synthetic enzymes. This was confirmed when BL6 cells were supplemented with arachidonic acid. Arachidonic acid had an inhibitory effect on BL6 cell growth and also stimulated prostaglandin E₂ production. Prostaglandin E₂ levels are in turn believed to modulate adenylate cyclase activity in BL6 cells, hence it is reasonable to conclude that adenylate cyclase activity is dependent on prostaglandin E₂ levels. Combined vitamin E succinate and Asc supplementation to BL6 cells resulted in significant increases in adenyl ate cyclase and cyclic adenosine monophosphate, which again correlated with a significant decrease in cell growth. As cyclic adenosine monophosphate has a regulatory role in the cell cycle this study suggested that the effect of combined vitamin E succinate and ascorbic acid supplementation was mediated through the final effect provided by the second messenger, cyclic adenosine monophosphate. This was confirmed when BL6 cells were supplemented with dexamethasone, a phospholipase A₂ inhibitor. This treatment rsulted in combined vitamin E succinate and ascorbic acid having no inhibitory effect on BL6 cell growth. Cyclooxygenase activity, prostaglandin E₂ levels, adenylate cyclase activity and cyclic adenosine monophosphate levels were significantly lower in dexamethasone-treated cells compared to non-treated dexamethasone cultures. The reason for the increased free radical and lipid peroxidation levels in BL6 cells was further investigated. Cyclooxygenase enzymes are believed to generate free radical species during catalytic activity. Analysis of free radical and lipid peroxidation levels following supplementation with dexamethasone revealed markedly lower free radical and significantly lower lipid peroxidation levels in comparison with control cultures and non dexamethasone-treated cultures. These results suggest that the observed increases in free radical and lipid peroxidation levels in BL6 cells supplemented with combined vitamin E succinate and ascorbic acid were indirectly due to the increase in cyclooxygenase activity in these cells.
- Full Text:
- Date Issued: 1997
The promotion of a racially integrated Catholic community at King William's Town : challenges and opportunities
- Authors: Fahy, Paul
- Date: 1988
- Subjects: Apartheid -- South Africa -- Religious aspects -- Catholic Church
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:1218 , http://hdl.handle.net/10962/d1001548
- Description: Taking as its point of departure the model of the Church as a sacrament of unity, this study explores its implications for the fostering of a racially integrated Catholic community within an apartheid society. The particular context within which the investigation is conducted is the Sacred Heart Church, King William's Town, where the writer is pastor to a multiracial congregation. A dialogical approach is adopted between theology and praxis, in terms of which the data from a social analysis of the community are brought into a creative dialogue with the Vatican II vision of the Church. Findings from the analysis show that the attitudes of congregants to a racially integrated community are generally ambivalent. Historical, theological, psychosocial and political factors are seen to play an important role in shaping these attitudes. Arising from the dialogue between theology and praxis, the model of a pilgrim Church suggests itself as more relevant and realistic. This model constitutes a proximate goal. The sacrament model of the Church provides direction and focus for the pilgrim Church and is viewed as the ultimate goal. These models must be seen as complementary. The study concludes with a pastoral plan aimed at attaining the goals described. The main thrust of this plan is directed at changing congregants' attitudes to a racially integrated community. The strategies suggested involve the motivation of congregants to become actively involved, the transformation of congregants' attitudes, the promotion of a positive attitude to conflict and the challenging of apartheid structures. A differential approach is suggested in the pursuit of these objectives. A final conclusion to be drawn from this study is that the search for community is never-ending and that the fostering of a racially integrated Catholic community is a slow and painful process.
- Full Text:
- Date Issued: 1988
- Authors: Fahy, Paul
- Date: 1988
- Subjects: Apartheid -- South Africa -- Religious aspects -- Catholic Church
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:1218 , http://hdl.handle.net/10962/d1001548
- Description: Taking as its point of departure the model of the Church as a sacrament of unity, this study explores its implications for the fostering of a racially integrated Catholic community within an apartheid society. The particular context within which the investigation is conducted is the Sacred Heart Church, King William's Town, where the writer is pastor to a multiracial congregation. A dialogical approach is adopted between theology and praxis, in terms of which the data from a social analysis of the community are brought into a creative dialogue with the Vatican II vision of the Church. Findings from the analysis show that the attitudes of congregants to a racially integrated community are generally ambivalent. Historical, theological, psychosocial and political factors are seen to play an important role in shaping these attitudes. Arising from the dialogue between theology and praxis, the model of a pilgrim Church suggests itself as more relevant and realistic. This model constitutes a proximate goal. The sacrament model of the Church provides direction and focus for the pilgrim Church and is viewed as the ultimate goal. These models must be seen as complementary. The study concludes with a pastoral plan aimed at attaining the goals described. The main thrust of this plan is directed at changing congregants' attitudes to a racially integrated community. The strategies suggested involve the motivation of congregants to become actively involved, the transformation of congregants' attitudes, the promotion of a positive attitude to conflict and the challenging of apartheid structures. A differential approach is suggested in the pursuit of these objectives. A final conclusion to be drawn from this study is that the search for community is never-ending and that the fostering of a racially integrated Catholic community is a slow and painful process.
- Full Text:
- Date Issued: 1988
A geographical analysis of nutrition in the Eastern Cape and Ciskei
- Authors: Fincham, Robert John
- Date: 1985
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4812 , http://hdl.handle.net/10962/d1004905
- Description: From preface: The primary aim of the thesis is to make an anthropometric assessment of levels of nutrition of black pre-school children in selected communities of the Eastern Cape and Ciskei. The communities are those of black labourers and their families on white-owned commercial farms in the Dias Divisional Council area of the Eastern Cape; a rural community of an area of Ciskei known as the Amatola Basin; and Tsweletsl'lele, a 'closer settlement' or resettlement area in Ciskei. A pilot survey of school entrants in the Albany magisterial district also sheds light on the nutrition of children in the small towns, such as Grahamstown, of the Eastern Cape. Through an analysis of nutritional conditions in these disparate communities, it should be possible to begin to establish the geographical variation of nutrition in the region. Black communities in the metropolitan area of Port Elizabeth are not considered in the thesis, but on-going surveillance in the city, by the author, will elucidate nutritional conditions there. In achieving the primary aim of the thesis, attention will be focussed on inter-community rather than intra-community variation in nutrition. Nutrition may vary within communities (intra-community variation), for example, within different parts of the Dias Divisional Council area. While such variation is 1 ikely to be minimal, as will be discussed in the presentation of results in chapter 6, section A(l), it is in itself important, and present research endeavours within the surveillance programme are being geared to explore this dimension of nutritional variation more fully. Inter-community variation in nutrition provides, however, a more than sufficient focus for the thesis. A secondary aim of the thesis is to explore the relationship between nutritional status and socio-economic conditions prevailing in the surveyed communities. The secondary aim makes it possible to obtain a better understanding of the processes whi ch infl uence the geographical pattern of nutrition. A consideration of socio-economic conditions, both within the communities and within the Eastern Cape and Ciskei as a whole, also provides a context in which the nutrition results can be assessed. The third aim of the thesis is to assess possible applications of the survey results to policy formulation, thereby providing an applied dimension to the work.
- Full Text:
- Date Issued: 1985
- Authors: Fincham, Robert John
- Date: 1985
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4812 , http://hdl.handle.net/10962/d1004905
- Description: From preface: The primary aim of the thesis is to make an anthropometric assessment of levels of nutrition of black pre-school children in selected communities of the Eastern Cape and Ciskei. The communities are those of black labourers and their families on white-owned commercial farms in the Dias Divisional Council area of the Eastern Cape; a rural community of an area of Ciskei known as the Amatola Basin; and Tsweletsl'lele, a 'closer settlement' or resettlement area in Ciskei. A pilot survey of school entrants in the Albany magisterial district also sheds light on the nutrition of children in the small towns, such as Grahamstown, of the Eastern Cape. Through an analysis of nutritional conditions in these disparate communities, it should be possible to begin to establish the geographical variation of nutrition in the region. Black communities in the metropolitan area of Port Elizabeth are not considered in the thesis, but on-going surveillance in the city, by the author, will elucidate nutritional conditions there. In achieving the primary aim of the thesis, attention will be focussed on inter-community rather than intra-community variation in nutrition. Nutrition may vary within communities (intra-community variation), for example, within different parts of the Dias Divisional Council area. While such variation is 1 ikely to be minimal, as will be discussed in the presentation of results in chapter 6, section A(l), it is in itself important, and present research endeavours within the surveillance programme are being geared to explore this dimension of nutritional variation more fully. Inter-community variation in nutrition provides, however, a more than sufficient focus for the thesis. A secondary aim of the thesis is to explore the relationship between nutritional status and socio-economic conditions prevailing in the surveyed communities. The secondary aim makes it possible to obtain a better understanding of the processes whi ch infl uence the geographical pattern of nutrition. A consideration of socio-economic conditions, both within the communities and within the Eastern Cape and Ciskei as a whole, also provides a context in which the nutrition results can be assessed. The third aim of the thesis is to assess possible applications of the survey results to policy formulation, thereby providing an applied dimension to the work.
- Full Text:
- Date Issued: 1985
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