Effect of pre-slaughter stress of pigs on the levels of cortisol, creatine kinase and their subsequent relationship with pork quality
- Authors: Nzolo, Jama
- Date: 2014
- Subjects: Slaughtering and slaughter-houses , Pork -- Quality , Swine -- Handling , Livestock -- Handling , Creatine kinase
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11837 , http://hdl.handle.net/10353/d1021287 , Slaughtering and slaughter-houses , Pork -- Quality , Swine -- Handling , Livestock -- Handling , Creatine kinase
- Description: The study was conducted to determine the effect of pre-slaughter stress of pigs on the levels of cortisol, creatine kinase (CK) and their subsequent relationship with pork quality. From our knowledge, there is paucity of information on transportation, lairage duration and sex effects on saliva cortisol and its relation with serum cortisol, urine cortisol and other meat quality traits. Stage one of the study assessed the effect of sex and time to slaughter (transport and lairage duration) on the levels of cortisol and CK in crossbred pigs. The second stage of the study evaluated the effect of sex and lairage duration on pork quality. The trials comprised of 60 22-weeks old commercial crossbred pigs [(30 boars vs. 30 gilts) with an average body weight of 76.9kg for gilts and 78.3kg for boars. Thirty pigs (15 Boars vs. 15 Gilts) were slaughtered on arrival after a 120km road journey and the other 30, after travelling the same road and distance, were slaughtered after having been in the lairage for 20 hours. Saliva samples were obtained during three time periods: between 07:00-10:00 on the day before the journey, on arrival at the abattoir and after lairage. Levels of cortisol in serum and urine and CK in serum samples collected at slaughter were determined. The samples (saliva and serum) were centrifuged at 20oC for 10 min at 3550 x g and stored at -20oC in separate vials until analysis. Pork quality was assessed using muscle pH, colour, thawing and cooking losses and Warner-Bratzler Shear Force. Correlations between cortisol levels in saliva, serum and urine and meat quality were assessed. The effect of sex and time to slaughter on saliva cortisol was significant. Statistical analysis showed significant interaction of sex by time to slaughter on serum cortisol. It was only the effect of sex that demonstrated higher (P <0.05) serum creatine kinase levels in gilts. Likewise, urine cortisol was influenced (P <0.05) only by time to slaughter. Saliva cortisol after transportation (r = 0.52) was correlated (P <0.05) with urine cortisol. The study suggests that there are greater responses of the Hypothalamic-pituitary-adrenal axis following time to slaughter (transport and lairage duration) between gilts and boars. This can be used in measuring cortisol in saliva, serum and urine, and serum creatine kinase to determine stress levels in pigs. Besides the lightness (L*) colour value which was significantly lower (P <0.05) in meat from gilts than from boars, the results of this study showed no interaction or individual effect (sex or lairage duration) on pH and other colour measurements. Meat cooking loss was affected (P <0.05) by gender x lairage interaction. Effect of lairage duration (as an individual effect) on the measured meat quality traits was not significant (P <0.05). Correlation analysis showed significant (P <0.05) negative relation between baseline saliva cortisol (r = -0.40) and the pork L* value. Saliva cortisol after lairage duration (r = -0.38 and r = 0.38) was correlated (P <0.05) with pH45 and pork a* value, respectively. Serum cortisol (r = -0.35) was negatively correlated (P <0.05) with pH45. Moreover, there were negative correlations (P <0.05) between saliva cortisol after transportation (r = -0.35), saliva cortisol after lairage duration (r = -0.44), serum cortisol (r = -0.40) and meat cooking loss. The study suggests that cortisol in saliva and serum can be used to determine effect of time to slaughter (transport and lairage duration) on meat quality traits from gilts and boars. Keywords: Boars; gilts; saliva cortisol; serum cortisol; serum creatine kinase; urine cortisol.
- Full Text:
- Date Issued: 2014
- Authors: Nzolo, Jama
- Date: 2014
- Subjects: Slaughtering and slaughter-houses , Pork -- Quality , Swine -- Handling , Livestock -- Handling , Creatine kinase
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11837 , http://hdl.handle.net/10353/d1021287 , Slaughtering and slaughter-houses , Pork -- Quality , Swine -- Handling , Livestock -- Handling , Creatine kinase
- Description: The study was conducted to determine the effect of pre-slaughter stress of pigs on the levels of cortisol, creatine kinase (CK) and their subsequent relationship with pork quality. From our knowledge, there is paucity of information on transportation, lairage duration and sex effects on saliva cortisol and its relation with serum cortisol, urine cortisol and other meat quality traits. Stage one of the study assessed the effect of sex and time to slaughter (transport and lairage duration) on the levels of cortisol and CK in crossbred pigs. The second stage of the study evaluated the effect of sex and lairage duration on pork quality. The trials comprised of 60 22-weeks old commercial crossbred pigs [(30 boars vs. 30 gilts) with an average body weight of 76.9kg for gilts and 78.3kg for boars. Thirty pigs (15 Boars vs. 15 Gilts) were slaughtered on arrival after a 120km road journey and the other 30, after travelling the same road and distance, were slaughtered after having been in the lairage for 20 hours. Saliva samples were obtained during three time periods: between 07:00-10:00 on the day before the journey, on arrival at the abattoir and after lairage. Levels of cortisol in serum and urine and CK in serum samples collected at slaughter were determined. The samples (saliva and serum) were centrifuged at 20oC for 10 min at 3550 x g and stored at -20oC in separate vials until analysis. Pork quality was assessed using muscle pH, colour, thawing and cooking losses and Warner-Bratzler Shear Force. Correlations between cortisol levels in saliva, serum and urine and meat quality were assessed. The effect of sex and time to slaughter on saliva cortisol was significant. Statistical analysis showed significant interaction of sex by time to slaughter on serum cortisol. It was only the effect of sex that demonstrated higher (P <0.05) serum creatine kinase levels in gilts. Likewise, urine cortisol was influenced (P <0.05) only by time to slaughter. Saliva cortisol after transportation (r = 0.52) was correlated (P <0.05) with urine cortisol. The study suggests that there are greater responses of the Hypothalamic-pituitary-adrenal axis following time to slaughter (transport and lairage duration) between gilts and boars. This can be used in measuring cortisol in saliva, serum and urine, and serum creatine kinase to determine stress levels in pigs. Besides the lightness (L*) colour value which was significantly lower (P <0.05) in meat from gilts than from boars, the results of this study showed no interaction or individual effect (sex or lairage duration) on pH and other colour measurements. Meat cooking loss was affected (P <0.05) by gender x lairage interaction. Effect of lairage duration (as an individual effect) on the measured meat quality traits was not significant (P <0.05). Correlation analysis showed significant (P <0.05) negative relation between baseline saliva cortisol (r = -0.40) and the pork L* value. Saliva cortisol after lairage duration (r = -0.38 and r = 0.38) was correlated (P <0.05) with pH45 and pork a* value, respectively. Serum cortisol (r = -0.35) was negatively correlated (P <0.05) with pH45. Moreover, there were negative correlations (P <0.05) between saliva cortisol after transportation (r = -0.35), saliva cortisol after lairage duration (r = -0.44), serum cortisol (r = -0.40) and meat cooking loss. The study suggests that cortisol in saliva and serum can be used to determine effect of time to slaughter (transport and lairage duration) on meat quality traits from gilts and boars. Keywords: Boars; gilts; saliva cortisol; serum cortisol; serum creatine kinase; urine cortisol.
- Full Text:
- Date Issued: 2014
Effect of water trophic level on the impact of the water hyacinth moth Niphograpta albiguttalis on Eichhornia crassipes
- Canavan, Kim N, Coetzee, Julie A, Hill, Martin P, Paterson, Iain D
- Authors: Canavan, Kim N , Coetzee, Julie A , Hill, Martin P , Paterson, Iain D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423740 , vital:72090 , xlink:href="https://doi.org/10.2989/16085914.2014.893225"
- Description: Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.
- Full Text:
- Date Issued: 2014
- Authors: Canavan, Kim N , Coetzee, Julie A , Hill, Martin P , Paterson, Iain D
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423740 , vital:72090 , xlink:href="https://doi.org/10.2989/16085914.2014.893225"
- Description: Eutrophication contributes to the proliferation of alien invasive weed species such as water hyacinth Eichhornia crassipes. Although the South American moth Niphograpta albiguttalis was released in South Africa in 1990 as a biological control agent against water hyacinth, no post-release evaluations have yet been conducted here. The impact of N. albiguttalis on water hyacinth growth was quantified under low-, medium- and high-nutrient concentrations in a greenhouse experiment. Niphograpta albiguttalis was damaging to water hyacinth in all three nutrient treatments, but significant damage in most plant parameters was found only under high-nutrient treatments. However, E. crassipes plants grown in high-nutrient water were healthier, and presumably had higher fitness, than plants not exposed to herbivory at lower-nutrient levels. Niphograpta albiguttalis is likely to be most damaging to water hyacinth in eutrophic water systems, but the damage will not result in acceptable levels of control because of the plant's high productivity under these conditions. Niphograpta albiguttalis is a suitable agent for controlling water hyacinth infestations in eutrophic water systems, but should be used in combination with other biological control agents and included in an integrated management plan also involving herbicidal control and water quality management.
- Full Text:
- Date Issued: 2014
Effectiveness of the project management profession in the Ugandan oil industry : performance, benefits and challenges
- Authors: Kiggundu, Kamulegeya John
- Date: 2014
- Subjects: Project Mangement -- Uganda , Oil industry workers -- Uganda , Benchmarking (Management) -- Uganda
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9707 , http://hdl.handle.net/10948/d1020059
- Description: Oil is one of the most valuable resources. For a country like Uganda, which is one of the least developed countries in the world with more than one third of the population still living below the poverty line; the discovery of this valuable resource has the capacity to radically alter the economy of the country. But on the other hand, oil exploration, mining and refining are complex, costly, long duration projects with many challenges that require sophisticated financial management, planning, scheduling and cost control. The project management profession is charged as a single point of responsibility for initiating, planning, executing, monitoring and controlling projects in order to meet stakeholder’s needs and expectations. The research objectives were: 1. To identify and examine the challenges and risks associated with the oil industry in Uganda. 2. To investigate the effectiveness of project management practices in the Ugandan oil industry in terms 1 above. 3. Identify how project success can be measured in the Ugandan oil industry. A case study was the research technique adopted and interviews were conducted with the major stakeholders in the Ugandan oil industry. The research findings reveal the challenges and risks that continue to plague the Ugandan oil industry and the role of project management in the exploration phase of the project. The research findings were used to evaluate the role, responsibility and service that project management professionals are expected to render and the actual role, responsibility and service that the professionals have been rendering to the stakeholders in the Ugandan oil industry. The research then concludes by proposing ways of improving the chances of project success in the Ugandan oil industry.
- Full Text:
- Date Issued: 2014
- Authors: Kiggundu, Kamulegeya John
- Date: 2014
- Subjects: Project Mangement -- Uganda , Oil industry workers -- Uganda , Benchmarking (Management) -- Uganda
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9707 , http://hdl.handle.net/10948/d1020059
- Description: Oil is one of the most valuable resources. For a country like Uganda, which is one of the least developed countries in the world with more than one third of the population still living below the poverty line; the discovery of this valuable resource has the capacity to radically alter the economy of the country. But on the other hand, oil exploration, mining and refining are complex, costly, long duration projects with many challenges that require sophisticated financial management, planning, scheduling and cost control. The project management profession is charged as a single point of responsibility for initiating, planning, executing, monitoring and controlling projects in order to meet stakeholder’s needs and expectations. The research objectives were: 1. To identify and examine the challenges and risks associated with the oil industry in Uganda. 2. To investigate the effectiveness of project management practices in the Ugandan oil industry in terms 1 above. 3. Identify how project success can be measured in the Ugandan oil industry. A case study was the research technique adopted and interviews were conducted with the major stakeholders in the Ugandan oil industry. The research findings reveal the challenges and risks that continue to plague the Ugandan oil industry and the role of project management in the exploration phase of the project. The research findings were used to evaluate the role, responsibility and service that project management professionals are expected to render and the actual role, responsibility and service that the professionals have been rendering to the stakeholders in the Ugandan oil industry. The research then concludes by proposing ways of improving the chances of project success in the Ugandan oil industry.
- Full Text:
- Date Issued: 2014
Effects of analytes on the fluorescence properties of CdTe@ ZnS quantum dots decorated with cobalt tetraamino-phthalocyanine
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189829 , vital:44935 , xlink:href="https://doi.org/10.1016/j.jlumin.2013.09.079"
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189829 , vital:44935 , xlink:href="https://doi.org/10.1016/j.jlumin.2013.09.079"
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe.
- Full Text:
- Date Issued: 2014
Effects of dietary inclusion of Moringa oleifera leaf meal on growth performance, physico-chemical attributes, oxidative stability and sensory quality of pork
- Authors: Nduku, Xola Pauline
- Date: 2014
- Subjects: Pork -- Quality , Food -- Sensory evaluation , Fatty acids , Moringa , Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11836 , http://hdl.handle.net/10353/d1021281 , Pork -- Quality , Food -- Sensory evaluation , Fatty acids , Moringa , Meat -- Quality
- Description: The objective of the study was to determine growth performance, physico-chemical attributes, oxidative stability and sensory quality of pork from pigs fed one of three dietary treatments, eac containing 0%, 2.5% or 5% (T1, T2 and T3, respectively) Moringa oleifera leaf meal (MOLM). Dietary treatments were formulated to be isonitrogenous and isoenergetic for weaner (6 – 8 weeks) and grower (9 – 13 weeks) phases. Twelve Large White (LW) and 12 Kolbroek (KB) male pigs at 6 weeks of age, initially weighing an average 10 kg, were randomly allocated to one of the dietary treatments, each with four replicates, in individual pens. Feed and water were offered ad libitum. The Longissimus thoracis et lumborum (LTL) muscle of each carcass (n = 24) was sampled for meat quality and fatty acid analyses. Breed differences in measured parameters were observed. In pigs receiving 5% MOLM, the LW had significantly the highest ADFI (P<0.05) than KB pigs. In pigs receiving 2.5% and 5% MOLM, backfat thickness was significantly highest (P<0.05) compared to those receiving 0% MOML. Dietary inclusion of MOLM had no significant effects (P>0.05) on the physico-chemical quality of pork from LW pigs; although it significantly (P<0.05) increased a* and reduced WBSF values in pork from KB pigs. Pork from LW pigs receiving 5% MOLM had significantly increased (P<0.05) n-3 content of the subcutaneous tissue of LW pigs compared to KB, and also when compread to other treatment groups. In both breeds, the composition of PUFA: SFA and n-6: n-3 in the subcutaneous adipose tissue was significantly (P<0.05) lower in T2 and T3 than in T1. The n-3 levels for pork muscle from LW pigs receiving 2.5% and 5% MOLM, and from KB pigs receiving 5% MOLM, were significantly (P<0.05) lower. Inclusions of MOLM significantly (P<0.05) reduced the n-6: n-3 fatty acids in pork from both LW pigs and KB pigs. Consumer scores on sensory attributes (aroma intensity, initial impression of juiciness, first bite, sustained impression of juiciness, muscle fibre and overall tenderness and overall flavor intensity) significantly (P<0.05) increased as the level of MOLM inclusion in the diet increased; and higher scores were observed in fried meat than in boiled for most sensory attributes. It may be concluded that inclusion of MOLM in pig diets up to 5% improved the ADFI, a*, tenderness of pork without adversely affecting the FCR and other physico-chemical quality attributes; and resulted in desired increase in levels of n-3 and reduced the n-6: n-3 fatty acid ratio.
- Full Text:
- Date Issued: 2014
- Authors: Nduku, Xola Pauline
- Date: 2014
- Subjects: Pork -- Quality , Food -- Sensory evaluation , Fatty acids , Moringa , Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11836 , http://hdl.handle.net/10353/d1021281 , Pork -- Quality , Food -- Sensory evaluation , Fatty acids , Moringa , Meat -- Quality
- Description: The objective of the study was to determine growth performance, physico-chemical attributes, oxidative stability and sensory quality of pork from pigs fed one of three dietary treatments, eac containing 0%, 2.5% or 5% (T1, T2 and T3, respectively) Moringa oleifera leaf meal (MOLM). Dietary treatments were formulated to be isonitrogenous and isoenergetic for weaner (6 – 8 weeks) and grower (9 – 13 weeks) phases. Twelve Large White (LW) and 12 Kolbroek (KB) male pigs at 6 weeks of age, initially weighing an average 10 kg, were randomly allocated to one of the dietary treatments, each with four replicates, in individual pens. Feed and water were offered ad libitum. The Longissimus thoracis et lumborum (LTL) muscle of each carcass (n = 24) was sampled for meat quality and fatty acid analyses. Breed differences in measured parameters were observed. In pigs receiving 5% MOLM, the LW had significantly the highest ADFI (P<0.05) than KB pigs. In pigs receiving 2.5% and 5% MOLM, backfat thickness was significantly highest (P<0.05) compared to those receiving 0% MOML. Dietary inclusion of MOLM had no significant effects (P>0.05) on the physico-chemical quality of pork from LW pigs; although it significantly (P<0.05) increased a* and reduced WBSF values in pork from KB pigs. Pork from LW pigs receiving 5% MOLM had significantly increased (P<0.05) n-3 content of the subcutaneous tissue of LW pigs compared to KB, and also when compread to other treatment groups. In both breeds, the composition of PUFA: SFA and n-6: n-3 in the subcutaneous adipose tissue was significantly (P<0.05) lower in T2 and T3 than in T1. The n-3 levels for pork muscle from LW pigs receiving 2.5% and 5% MOLM, and from KB pigs receiving 5% MOLM, were significantly (P<0.05) lower. Inclusions of MOLM significantly (P<0.05) reduced the n-6: n-3 fatty acids in pork from both LW pigs and KB pigs. Consumer scores on sensory attributes (aroma intensity, initial impression of juiciness, first bite, sustained impression of juiciness, muscle fibre and overall tenderness and overall flavor intensity) significantly (P<0.05) increased as the level of MOLM inclusion in the diet increased; and higher scores were observed in fried meat than in boiled for most sensory attributes. It may be concluded that inclusion of MOLM in pig diets up to 5% improved the ADFI, a*, tenderness of pork without adversely affecting the FCR and other physico-chemical quality attributes; and resulted in desired increase in levels of n-3 and reduced the n-6: n-3 fatty acid ratio.
- Full Text:
- Date Issued: 2014
Effects of number of ring substituents on the physicochemical properties of zinc aminophenoxy phthalocyanine-single walled carbon nanotube conjugate
- Ogbodu, Rachael O, Nyokong, Tebello
- Authors: Ogbodu, Rachael O , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190356 , vital:44987 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.09.015"
- Description: This work reports on the linking of zinc monoaminophenoxy (ZnMAPPc) or zinc tetraaminophenoxy phthalocyanine (ZnTAPPc) complexes to single walled carbon nanotubes (SWCNTs) through either covalent or non-covalent (adsorption) bonding. The functionalized complexes showed better thermal stability when compared to the SWCNT-COOH, ZnMAPPc and ZnTAPPc alone as confirmed by thermogravimetric analyses. The covalently linked ZnMAPc-SWCNT showed higher electron transfer rate constant and photoinduced electron efficiency when compared to adsorbed complexes. ZnMAPPc-SWCNT complexes (linked and adsorbed) showed better photophysical and photochemical properties when compared to ZnTAPPc-SWCNT complexes. The triplet, singlet oxygen and florescence quantum yields of ZnMAPPc (or ZnTAPPc) decrease upon linking or adsorption onto SWCNTs.
- Full Text:
- Date Issued: 2014
- Authors: Ogbodu, Rachael O , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190356 , vital:44987 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.09.015"
- Description: This work reports on the linking of zinc monoaminophenoxy (ZnMAPPc) or zinc tetraaminophenoxy phthalocyanine (ZnTAPPc) complexes to single walled carbon nanotubes (SWCNTs) through either covalent or non-covalent (adsorption) bonding. The functionalized complexes showed better thermal stability when compared to the SWCNT-COOH, ZnMAPPc and ZnTAPPc alone as confirmed by thermogravimetric analyses. The covalently linked ZnMAPc-SWCNT showed higher electron transfer rate constant and photoinduced electron efficiency when compared to adsorbed complexes. ZnMAPPc-SWCNT complexes (linked and adsorbed) showed better photophysical and photochemical properties when compared to ZnTAPPc-SWCNT complexes. The triplet, singlet oxygen and florescence quantum yields of ZnMAPPc (or ZnTAPPc) decrease upon linking or adsorption onto SWCNTs.
- Full Text:
- Date Issued: 2014
Effects of oats and vetch cover crops on light organic matter fractions and activities of selected enzymes in an irrigated maize based conservation agriculture system on Alice Jozini Ecotope in the Eastern Cape, South Africa
- Authors: Mukumbareza, Caroline
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc Agric (Crop Science)
- Identifier: vital:11872 , http://hdl.handle.net/10353/d1019815
- Description: Low soil fertility in the Eastern Cape Province (EC) is attributed to poor agricultural management, which reduces organic matter, among other factors. Conservation agriculture (CA), consisting of no-till, soil cover and rotations, is being promoted to improve soil quality and productivity. Soil biological parameters respond to the overall effects of management on the physical and chemical components of soil. This study was conducted to evaluate the effects of oat (Avena sativa) and grazing vetch (Vicia dasycarpa) cover crops on soil biological activity after five years under CA and evaluate light organic matter fractions, MBC and activities of selected enzymes as early indicators of organic matter build up under in no-till maize based CA system. The study was based on soil samples collected from a five year trial with rotations of maize and sole covercrops and two younger trials (4 and 28 months) with oat and grazing vetch bicultures. In the five year old trial, oat and grazing vetch were planted at four fertiliser regimes (i) Fertilizer applied to cover crops and maize (F1), (ii) fertilizer applied to cover crops only (F2), (iii) fertilizer applied to maize only (F3) and (iv) no fertilizer applied (F4)) to give a 2 × 4 factorial plus control laid out in a randomized complete block design (RCBD) with three replications. Fertilizer was applied at 10 kg P ha-1, as a compound (6.7% N; 10% P; 13.3% K) at planting and grazing vetch was inoculated with Rhizobium legunominosarium biovar viciae. Oat was top dressed using limestone ammonium nitrate (LAN – 28% N) at 7 weeks after planting (WAP) to make a total of 45 kg N ha-1. Three weeks after termination of the cover crops, all plots were split in half and maize was planted and fertilizer applied at 0 and 60 N kg ha-1. A third of the N was applied at planting (6.7% N; 10% P; 13.3% K). In the biculture trials, the treatments were 90% oat + 10% vetch, 70% oat + 30% vetch, 50% oat+ 50% vetch, 100% vetch and 100% oat and laid out in a RCBD with three replicates. Only basal fertilizer was applied to the cover crop at planting at 13.34 kg N ha-1, 20 kg P ha-1 and 26.66 kg K ha-1 using 2:3:4 (30 + 0.5% Zn) compound fertiliser. After cover crop termination, SC701 maize variety was planted, and fertilised at 60 kg N ha-1 with a third of the N applied as a basal. In the five year old trial, oat and vetch gave significantly (P < 0.05) higher MBC and activities of all soil enzymes measured than the weedy fallow at 0-5 and 5-20 cm depths. Fertilization of cover crop (F2) and maize (F3) gave similar MBC. The F4 in cover crops gave similar dehydrogenase activity with F3 under weedy fallow and that for vetch rotation was the same for F3 in oat. The F4 for grazing vetch had similar β-glucosidase activity as F1 and similar urease activity as F1, F2 and F3 of oat rotations. Acid and alkaline activity in F1 had similar results to F2. In the younger trials, biculture treatments did not improve total C, and N when compared with the weedy fallow. Dehydrogenase, β-glucosidase, arylsulphatase and alkaline phosphatase activities were higher in the 28 month trial compared to the 4 month one while urease was higher in the 4-month old trial. Treatments with more than 50% oat content had higher acid phosphatase activity in the 4- than 28 month old trial. Effects of cover crop, as the main factor, was significant in all enzymes (P < 0.05), with 70% oat + 30% vetch treatment having the highest dehydrogenase and arylsulphatase while for alkaline phosphatase it had similar results to 90% oat + 10% vetch. For β-glucosidase and urease, effects of cover crop as the main factor were also significant with sole vetch giving the highest activity for both enzymes. Acid phosphatase activity was highest in sole oat. Particulate OM was highest in the 100% oat treatment and declined with decrease in the proportion of oat in the biculture. The 50% oat + 50% vetch treatment had similar POM to the 70% oat +30% vetch in the 4 month old trial and to the 90% oat + 10% vetch in the 28 months old trial in the 0-5 cm depth (P < 0.05). In the 5-20 cm depth, the 70% oat +30% vetch treatment had similar POM to the 90% oat + 10% vetch in the 28 month old trial. The 70% oat+30% vetch had greatest WSC and MBC followed by the 90% oat +10% vetch, with the 50% oat + 50% vetch being similar to 100% vetch and 100% oat (MBC only). The 28 months old trial had greater POM and WSC than the 4 months trial. The findings of this study imply that the use of grazing vetch and fertilization of cover crops only improves soil biological activity, represented by MBC and enzyme activities, after 5 years of maize-cover crop rotations in low input conservation agriculture system. Bicultures, particularly the 70% oat + 30% vetch, work better than their sole crops in improving organic matter fractions, MBC and enzyme activities and that POM, WSC, MBC, enzyme activities are useful early indicators of soil organic matter build-up of CA systems.
- Full Text:
- Date Issued: 2014
- Authors: Mukumbareza, Caroline
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc Agric (Crop Science)
- Identifier: vital:11872 , http://hdl.handle.net/10353/d1019815
- Description: Low soil fertility in the Eastern Cape Province (EC) is attributed to poor agricultural management, which reduces organic matter, among other factors. Conservation agriculture (CA), consisting of no-till, soil cover and rotations, is being promoted to improve soil quality and productivity. Soil biological parameters respond to the overall effects of management on the physical and chemical components of soil. This study was conducted to evaluate the effects of oat (Avena sativa) and grazing vetch (Vicia dasycarpa) cover crops on soil biological activity after five years under CA and evaluate light organic matter fractions, MBC and activities of selected enzymes as early indicators of organic matter build up under in no-till maize based CA system. The study was based on soil samples collected from a five year trial with rotations of maize and sole covercrops and two younger trials (4 and 28 months) with oat and grazing vetch bicultures. In the five year old trial, oat and grazing vetch were planted at four fertiliser regimes (i) Fertilizer applied to cover crops and maize (F1), (ii) fertilizer applied to cover crops only (F2), (iii) fertilizer applied to maize only (F3) and (iv) no fertilizer applied (F4)) to give a 2 × 4 factorial plus control laid out in a randomized complete block design (RCBD) with three replications. Fertilizer was applied at 10 kg P ha-1, as a compound (6.7% N; 10% P; 13.3% K) at planting and grazing vetch was inoculated with Rhizobium legunominosarium biovar viciae. Oat was top dressed using limestone ammonium nitrate (LAN – 28% N) at 7 weeks after planting (WAP) to make a total of 45 kg N ha-1. Three weeks after termination of the cover crops, all plots were split in half and maize was planted and fertilizer applied at 0 and 60 N kg ha-1. A third of the N was applied at planting (6.7% N; 10% P; 13.3% K). In the biculture trials, the treatments were 90% oat + 10% vetch, 70% oat + 30% vetch, 50% oat+ 50% vetch, 100% vetch and 100% oat and laid out in a RCBD with three replicates. Only basal fertilizer was applied to the cover crop at planting at 13.34 kg N ha-1, 20 kg P ha-1 and 26.66 kg K ha-1 using 2:3:4 (30 + 0.5% Zn) compound fertiliser. After cover crop termination, SC701 maize variety was planted, and fertilised at 60 kg N ha-1 with a third of the N applied as a basal. In the five year old trial, oat and vetch gave significantly (P < 0.05) higher MBC and activities of all soil enzymes measured than the weedy fallow at 0-5 and 5-20 cm depths. Fertilization of cover crop (F2) and maize (F3) gave similar MBC. The F4 in cover crops gave similar dehydrogenase activity with F3 under weedy fallow and that for vetch rotation was the same for F3 in oat. The F4 for grazing vetch had similar β-glucosidase activity as F1 and similar urease activity as F1, F2 and F3 of oat rotations. Acid and alkaline activity in F1 had similar results to F2. In the younger trials, biculture treatments did not improve total C, and N when compared with the weedy fallow. Dehydrogenase, β-glucosidase, arylsulphatase and alkaline phosphatase activities were higher in the 28 month trial compared to the 4 month one while urease was higher in the 4-month old trial. Treatments with more than 50% oat content had higher acid phosphatase activity in the 4- than 28 month old trial. Effects of cover crop, as the main factor, was significant in all enzymes (P < 0.05), with 70% oat + 30% vetch treatment having the highest dehydrogenase and arylsulphatase while for alkaline phosphatase it had similar results to 90% oat + 10% vetch. For β-glucosidase and urease, effects of cover crop as the main factor were also significant with sole vetch giving the highest activity for both enzymes. Acid phosphatase activity was highest in sole oat. Particulate OM was highest in the 100% oat treatment and declined with decrease in the proportion of oat in the biculture. The 50% oat + 50% vetch treatment had similar POM to the 70% oat +30% vetch in the 4 month old trial and to the 90% oat + 10% vetch in the 28 months old trial in the 0-5 cm depth (P < 0.05). In the 5-20 cm depth, the 70% oat +30% vetch treatment had similar POM to the 90% oat + 10% vetch in the 28 month old trial. The 70% oat+30% vetch had greatest WSC and MBC followed by the 90% oat +10% vetch, with the 50% oat + 50% vetch being similar to 100% vetch and 100% oat (MBC only). The 28 months old trial had greater POM and WSC than the 4 months trial. The findings of this study imply that the use of grazing vetch and fertilization of cover crops only improves soil biological activity, represented by MBC and enzyme activities, after 5 years of maize-cover crop rotations in low input conservation agriculture system. Bicultures, particularly the 70% oat + 30% vetch, work better than their sole crops in improving organic matter fractions, MBC and enzyme activities and that POM, WSC, MBC, enzyme activities are useful early indicators of soil organic matter build-up of CA systems.
- Full Text:
- Date Issued: 2014
Effects of pyrene on the photophysical and two-photon absorption-based nonlinear optical properties of indium (III) phthalocyanines
- Sanusi, Kayode, Nyokong, Tebello
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189957 , vital:44951 , xlink:href="https://doi.org/10.1080/00958972.2014.959509"
- Description: Photophysical and two-photon-dependent nonlinear absorption properties of two chloroindium(III) phthalocyanines bearing pyrene units have been investigated. The tetra- (3) and the tri- (4) pyrene-substituted phthalocyanines exhibit strong triplet absorption with high triplet yields ( ) of 0.79 and 0.83, respectively. The measured nonlinear optical data, such as the two photon absorption cross-sections, the third- and second-order nonlinearities were found to be comparable with those of literature, thus, making the compounds promising candidates for a broad range of nonlinear optical applications.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189957 , vital:44951 , xlink:href="https://doi.org/10.1080/00958972.2014.959509"
- Description: Photophysical and two-photon-dependent nonlinear absorption properties of two chloroindium(III) phthalocyanines bearing pyrene units have been investigated. The tetra- (3) and the tri- (4) pyrene-substituted phthalocyanines exhibit strong triplet absorption with high triplet yields ( ) of 0.79 and 0.83, respectively. The measured nonlinear optical data, such as the two photon absorption cross-sections, the third- and second-order nonlinearities were found to be comparable with those of literature, thus, making the compounds promising candidates for a broad range of nonlinear optical applications.
- Full Text:
- Date Issued: 2014
Effects of pyrene on the photophysical and two-photon absorption-based nonlinear optical properties of indium(III) phthalocyanines
- Sanusi, Kayode, Nyokong, Tebello
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Language: English
- Type: Article
- Identifier: vital:7314 , http://hdl.handle.net/10962/d1020540
- Description: Photophysical and two-photon-dependent nonlinear absorption properties of two chloroindium(III) phthalocyanines bearing pyrene units have been investigated. The tetra- (3) and the tri- (4) pyrene-substituted phthalocyanines exhibit strong triplet absorption with high triplet yields () of 0.79 and 0.83, respectively. The measured nonlinear optical data, such as the two photon absorption cross-sections, the third- and second-order nonlinearities were found to be comparable with those of literature, thus, making the compounds promising candidates for a broad range of nonlinear optical applications. , Original publication is available at http://dx.doi.org/10.1080/00958972.2014.959509
- Full Text: false
- Date Issued: 2014
- Authors: Sanusi, Kayode , Nyokong, Tebello
- Date: 2014
- Language: English
- Type: Article
- Identifier: vital:7314 , http://hdl.handle.net/10962/d1020540
- Description: Photophysical and two-photon-dependent nonlinear absorption properties of two chloroindium(III) phthalocyanines bearing pyrene units have been investigated. The tetra- (3) and the tri- (4) pyrene-substituted phthalocyanines exhibit strong triplet absorption with high triplet yields () of 0.79 and 0.83, respectively. The measured nonlinear optical data, such as the two photon absorption cross-sections, the third- and second-order nonlinearities were found to be comparable with those of literature, thus, making the compounds promising candidates for a broad range of nonlinear optical applications. , Original publication is available at http://dx.doi.org/10.1080/00958972.2014.959509
- Full Text: false
- Date Issued: 2014
Effects of redox mediators on the catalytic activity of iron porphyrins towards oxygen reduction in acidic media
- He, Qinggang, Wu, Gang, Liu, Ke, Khene, Samson M, Li, Qing, Mugadza, Tawanda, Deunf, Elise, Nyokong, Tebello, Chen, Shaowei W
- Authors: He, Qinggang , Wu, Gang , Liu, Ke , Khene, Samson M , Li, Qing , Mugadza, Tawanda , Deunf, Elise , Nyokong, Tebello , Chen, Shaowei W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241472 , vital:50942 , xlink:href="https://doi.org/10.1002/celc.201402054"
- Description: The effects of different redox mediators on the oxygen reduction reaction (ORR) catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], in 0.1 M triflic acid were investigated by cyclic voltammetry (CV) and spectroelectrochemistry in conjunction with density functional theory (DFT) calculations. The formal potentials of the FeIIITMPyP catalyst and the redox mediators, as well as the half-wave potentials for the ORR, were determined by CV in the absence and presence of oxygen in acidic solutions. UV/Vis spectroscopic and spectroelectrochemical studies confirmed that only the 2,2′-azino-bis(3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR. DFT calculations suggested strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator. The redox mediator caused lengthening of the dioxygen iron bond, which thus suggested easier dioxygen reduction. Consistent results were observed in electrochemical impedance spectroscopic measurements for which the electron-transfer kinetics were also evaluated.
- Full Text:
- Date Issued: 2014
- Authors: He, Qinggang , Wu, Gang , Liu, Ke , Khene, Samson M , Li, Qing , Mugadza, Tawanda , Deunf, Elise , Nyokong, Tebello , Chen, Shaowei W
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241472 , vital:50942 , xlink:href="https://doi.org/10.1002/celc.201402054"
- Description: The effects of different redox mediators on the oxygen reduction reaction (ORR) catalyzed by an iron porphyrin complex, iron(III) meso-tetra(N-methyl-4-pyridyl)porphine chloride [FeIIITMPyP], in 0.1 M triflic acid were investigated by cyclic voltammetry (CV) and spectroelectrochemistry in conjunction with density functional theory (DFT) calculations. The formal potentials of the FeIIITMPyP catalyst and the redox mediators, as well as the half-wave potentials for the ORR, were determined by CV in the absence and presence of oxygen in acidic solutions. UV/Vis spectroscopic and spectroelectrochemical studies confirmed that only the 2,2′-azino-bis(3-ethylbenzothiazioline-6-sulfonic acid)diammonium salt (C18H24N6O6S4) showed effective interactions with FeIIITMPyP during the ORR. DFT calculations suggested strong interaction between FeIIITMPyP and the C18H24N6O6S4 redox mediator. The redox mediator caused lengthening of the dioxygen iron bond, which thus suggested easier dioxygen reduction. Consistent results were observed in electrochemical impedance spectroscopic measurements for which the electron-transfer kinetics were also evaluated.
- Full Text:
- Date Issued: 2014
Efficacy of two medical plant extracts and metformin in the prevention of diet induced fatty liver
- Tshidino, Shonisani Cathphonia
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2014
- Subjects: Plant Extracts -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/9066 , vital:26461
- Description: Non‐alcoholic fatty liver diseases (NAFLD) is manifested in the absent of alcohol abuse. This disease is the major cause of liver failure and death among adults and children worldwide, including South Africa. Its increasing prevalence urges the need of therapeutic intervention. The main objectives of this study were to investigate the following: (1) The effect of 38.9% high fat diet (HFD)‐induced insulin resistance and fatty liver in male Wistar rats, (2) The efficacy of aqueous extracts from Sutherlandia frutescens leaves and Prunus africana bark and metformin in the treatment of HFDinduced insulin resistance and fatty liver. Male Wistar rats were fed on HFD (the HF group) or normal rat chow (the LF group) for 12 weeks. Even though the HFD‐fed rats had developed insulin resistance by week 12, fatty liver developed by week 16. After week 12, the HF group was divided into four groups of 6‐7 rats each and three of those groups were gavaged with either 0.125 mg P. africana extract/kg bwt/day (the HF+Pa group) or 50 mg S. frutescens extract kg bwt/day (the HF+Sf group) or 16 mg metformin/ kg bwt/day (HF+Met group), while kept on the same diet for an additional of 4 weeks, to investigate whether two medicinal plant extracts and metformin can prevent HFD to induce fatty liver or not. After 16 weeks, the liver histological images revealed that the HF group developed fatty liver in the form of both microsteatosis and macrosteatosis. Fatty liver was confirmed by significant increased liver total lipid (TL) and activities of glucose‐6‐phosphate dehydrogenase (cG6PD) and xanthine oxidase (XO), mitochondrial NADH oxidase (mNOX) and by a decrease (P<0.05) in the activities of the homogenate superoxide dismutase (hSOD) and mitochondrial complex II in the HF group, when compared to the LF group. Since the activities of mCS and cACL enzymes were not changed in the HF group, hence increased cG6PD activity in the HF group indicates that there was increased NADPH demand for lipid accumulation from activated NEFAs taken up by the liver from circulation and for maintenance of the NADPH‐dependent antioxidants and oxidants, respectively. The obtained data also show that mitochondria of the HFD‐fed rats adapted to an increase in energy availability, thereby compensation through decreasing complex II activity, to allow electron flux from β‐oxidation to respiratory chain in the HF group. Liver TL content was significantly decreased in the rats treated with metformin and P. africana extract, but not in the rats treated with S. frutescens when compared to the HF group (P < 0.05). However, the TL content remained >5% per liver weight in all treated groups. The present study demonstrates that these two plant extracts and metformin have different glucogenic and lipogenic effects from that presented by HFD alone when compared to the LFD alone. In conclusion, metformin and P. africana extract can attenuate HFD‐induced fatty liver without changing the dietary habits. Hence S. frutescens extract is less effective in the prevention of HFD‐induced fatty liver. A change in the dietary habits is recommended to be considered during the use of these three remedies in the treatment of HFD‐induced insulin resistance and fatty liver. All three treatments enhanced antioxidant capacity, and may improve insulin resistance and fatty liver mediated by the present HFD through different mechanism of actions in the liver.
- Full Text:
- Date Issued: 2014
Electing high-order modes in solid state laser resonators
- Authors: Iheanetu, Kelachukwu
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc (Physics)
- Identifier: http://hdl.handle.net/10353/995 , vital:26516
- Description: The first chapter considered the fundamental processes of laser operation: photon absorption, spontaneous and stimulated emissions. These processes are considered when designing a laser gain medium. A four-level laser scheme was also illustrated. Then, the basic components and operating principle of a simple laser system was presented using a diode end-pumped Nd:YAG solid state laser resonator. The second chapter considered laser light as light rays propagating in the resonator and extensively discussed the oscillating field in the laser resonators. It examined the characteristics of the fundamental Gaussian mode and the same theory was applied to higher-order modes. Chapter three started with an introduction to beam shaping and proceeded to present a review of some intra-cavity beam shaping techniques, the use of; graded phase mirrors, difractive elements { binary phase elements and spiral phase elements. Also, a brief discussion was given on the concept of conventional holography and digital holography. The phase-only spatial light modulator (SLM) was presented, which by default is used to perform (only) phase modulation of optical fields and how it can be use to perform amplitude modulation also. Finally, a detailed discussion of the digital laser which uses the intracavity SLM as a mode selection element was presented, since it was the technique used in the experiment. The elegance of dynamic on-demand mode selection that required only a change of the grey-scale hologram on the SLM was one quality that was exploited in using the digital laser. The next two chapters presented the experiments and results. The concept of the digital laser was first used in the experiment in chapter four, to assemble a stable diode endpumped Nd:YAG solid state laser resonator. Basically, the cavity was of hemispherical configuration using an intra-cavity SLM (virtual concave mirror) as a back re ector and a at mirror output coupler. A virtual concave mirror was achieve on the SLM by using phase modulation to generate the hologram of a lens, which when displayed on the SLM made it to mimic a concave mirror. Then the next phase was using symmetric Laguerre-Gaussian mode function, of zero azimuthal order to generate digital holograms that correspond to amplitude absorbing concentric rings. These holograms, combined with the hologram that iv mimics a concave mirror were used on the SLM to perform high-order Laguerre-Gaussian modes selection in the cavity. The fifth chapter presented the results of the mode selection and considered the purity of the beam at the output coupler by comparing measured modal properties with the theoretical prediction. The outcome confirmed that the modes were of high purity and quality which further implied that the cavity was indeed selecting single pure high-order modes. The results also demonstrated that forcing the cavity to oscillate at higher-order modes (p = 3) extracted 74% more power from the gain medium compared to the fundamental mode (p = 0), but this extra power is only accessible beyond a critical pump input power of 38.8 W. Laser brightness describes the potential of a laser beam to achieve high intensities while still maintaining a large Rayleigh range. It is a property that is dependent on beam power and its quality factor. To achieve high brightness one needs to generate a beam that extracts maximum power from the gain with good beam quality. Building on the experiments demonstrated in this study, one can make the correct choices of output coupler's re ectivity, the laser gain medium's length and doping concentration and the pump mode overlap for a particular mode to further enhance energy extraction from the cavity, and then using well known extra-cavity techniques to improve the output beams quality factor by transforming the high-order mode back to the fundamental mode. This will electively achieve higher laser brightness.
- Full Text:
- Date Issued: 2014
- Authors: Iheanetu, Kelachukwu
- Date: 2014
- Language: English
- Type: Thesis , Masters , MSc (Physics)
- Identifier: http://hdl.handle.net/10353/995 , vital:26516
- Description: The first chapter considered the fundamental processes of laser operation: photon absorption, spontaneous and stimulated emissions. These processes are considered when designing a laser gain medium. A four-level laser scheme was also illustrated. Then, the basic components and operating principle of a simple laser system was presented using a diode end-pumped Nd:YAG solid state laser resonator. The second chapter considered laser light as light rays propagating in the resonator and extensively discussed the oscillating field in the laser resonators. It examined the characteristics of the fundamental Gaussian mode and the same theory was applied to higher-order modes. Chapter three started with an introduction to beam shaping and proceeded to present a review of some intra-cavity beam shaping techniques, the use of; graded phase mirrors, difractive elements { binary phase elements and spiral phase elements. Also, a brief discussion was given on the concept of conventional holography and digital holography. The phase-only spatial light modulator (SLM) was presented, which by default is used to perform (only) phase modulation of optical fields and how it can be use to perform amplitude modulation also. Finally, a detailed discussion of the digital laser which uses the intracavity SLM as a mode selection element was presented, since it was the technique used in the experiment. The elegance of dynamic on-demand mode selection that required only a change of the grey-scale hologram on the SLM was one quality that was exploited in using the digital laser. The next two chapters presented the experiments and results. The concept of the digital laser was first used in the experiment in chapter four, to assemble a stable diode endpumped Nd:YAG solid state laser resonator. Basically, the cavity was of hemispherical configuration using an intra-cavity SLM (virtual concave mirror) as a back re ector and a at mirror output coupler. A virtual concave mirror was achieve on the SLM by using phase modulation to generate the hologram of a lens, which when displayed on the SLM made it to mimic a concave mirror. Then the next phase was using symmetric Laguerre-Gaussian mode function, of zero azimuthal order to generate digital holograms that correspond to amplitude absorbing concentric rings. These holograms, combined with the hologram that iv mimics a concave mirror were used on the SLM to perform high-order Laguerre-Gaussian modes selection in the cavity. The fifth chapter presented the results of the mode selection and considered the purity of the beam at the output coupler by comparing measured modal properties with the theoretical prediction. The outcome confirmed that the modes were of high purity and quality which further implied that the cavity was indeed selecting single pure high-order modes. The results also demonstrated that forcing the cavity to oscillate at higher-order modes (p = 3) extracted 74% more power from the gain medium compared to the fundamental mode (p = 0), but this extra power is only accessible beyond a critical pump input power of 38.8 W. Laser brightness describes the potential of a laser beam to achieve high intensities while still maintaining a large Rayleigh range. It is a property that is dependent on beam power and its quality factor. To achieve high brightness one needs to generate a beam that extracts maximum power from the gain with good beam quality. Building on the experiments demonstrated in this study, one can make the correct choices of output coupler's re ectivity, the laser gain medium's length and doping concentration and the pump mode overlap for a particular mode to further enhance energy extraction from the cavity, and then using well known extra-cavity techniques to improve the output beams quality factor by transforming the high-order mode back to the fundamental mode. This will electively achieve higher laser brightness.
- Full Text:
- Date Issued: 2014
Electrical conductivity experiments on carbon-rich Karoo shales and forward modelling of aeromagnetic data across the Beattie Anomaly
- Authors: Branch, Thomas Cameron
- Date: 2014
- Subjects: Earth sciences -- South Africa -- Karoo , Geology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10662 , http://hdl.handle.net/10948/d1014544
- Description: The Beattie Magnetic Anomaly is the world’s longest terrestrial magnetic anomaly with a strike length of over 1000 km and a wavelength in excess of 100 km. Collinear with this is a large belt of elevated crustal conductivities called the Southern Cape Conductive Belt. Historical crustal interpretations proposed a common source of serpentinized ophiolite as an explanation for both the anomalous crustal magnetic susceptibility and electrical conductivities. Spreading between the Western and Eastern Cape of South Africa the mid- to lower crust that hosts these anomalies is obscured by the overlying Cape and Karoo Supergroups. Between 2003 and 2006, three high resolution geophysical experiments were completed across the surface maximum of the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB). These included a magnetotelluric (MT) survey and near vertical reflection and wide angle refraction seismic profiles. Within the MT inversion model the SCCB appeared as a composite anomaly, which included a mid-crustal conductor which is spatially associated with the BMA and a laterally continuous upper crustal conductor which is located at depths equivalent to the lower Karoo Supergroup. Subsequently; the upper crustal conductor was identified in northern and eastern extensions of the magnetotelluric profile; a distance in excess of 400 km. Historical magnetometer and Schlumberger Sounding experiments have previously identified elevated conductivities in the Karoo sequences which were attributed to the Whitehill and Prince Albert formations. These carboniferous, transgressive sediments are known to be conductive from borehole conductivity surveys and direct measurements at surface. In order to constrain the conductive properties of these sediments, impedance spectroscopy (IS) experiments were completed on core samples collected from a historical borehole drilled near to the MT profile. Part One of this thesis presents the results of these experiments, which support the proposition that the Whitehill and Prince Albert Formations are responsible for the laterally continuous, sub-horizontal, upper crustal conductor visible in the MT inversion model. Vitrinite reflectance studies were performed on the same samples by the Montanuniversität, in Leoben, these results corroborate the proposition that elevated organic carbon, of meta-anthracite rank, is the primary conductive phase for the Whitehill and Prince Albert formations. Part two of this thesis completed forward modelling exercises using historical aeromagnetic data previously collected across the Beattie Magnetic Anomaly. Preliminary models were unable to fit the geometry of any single magnetic model with conductors present in the MT inversion model discounting the proposition that the SCCB and BMA arise from a single crustal unit. Two constrained models were arrived at through an iterative process that sought a best fit between the measured data and the NVR crustal interpretations. The first model, proposes a largely resistive unit which incorporates portions of elevated crustal conductivity; these conductors are spatially correlated to crustal portions also characterised by high seismic reflectivity. The size of this modelled body suggest the likely host of the BMA is an intermediate plutonic terrane, analogous with the Natal sector of the Namaqua Natal Mobile Belt as well as the Heimefrontfjella in Dronning Maud Land, Antarctica, with magnetite hosted within shear zones. This is in agreement with previous studies. The second model proposes a lower crustal sliver imaged in the NVR data at depths proximal to the Curie Isotherm for magnetite and hematite as the source of the BMA. At these depths geomagnetic properties such as burial magnetisation or thermo-viscous remanent magnetism (TVRM) can potentially be linked to regional scale tectonic processes and can theoretically elevate a body’s net magnetic susceptibility. TVRM has been proposed for long wavelength crustal anomalies elsewhere.
- Full Text:
- Date Issued: 2014
- Authors: Branch, Thomas Cameron
- Date: 2014
- Subjects: Earth sciences -- South Africa -- Karoo , Geology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10662 , http://hdl.handle.net/10948/d1014544
- Description: The Beattie Magnetic Anomaly is the world’s longest terrestrial magnetic anomaly with a strike length of over 1000 km and a wavelength in excess of 100 km. Collinear with this is a large belt of elevated crustal conductivities called the Southern Cape Conductive Belt. Historical crustal interpretations proposed a common source of serpentinized ophiolite as an explanation for both the anomalous crustal magnetic susceptibility and electrical conductivities. Spreading between the Western and Eastern Cape of South Africa the mid- to lower crust that hosts these anomalies is obscured by the overlying Cape and Karoo Supergroups. Between 2003 and 2006, three high resolution geophysical experiments were completed across the surface maximum of the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB). These included a magnetotelluric (MT) survey and near vertical reflection and wide angle refraction seismic profiles. Within the MT inversion model the SCCB appeared as a composite anomaly, which included a mid-crustal conductor which is spatially associated with the BMA and a laterally continuous upper crustal conductor which is located at depths equivalent to the lower Karoo Supergroup. Subsequently; the upper crustal conductor was identified in northern and eastern extensions of the magnetotelluric profile; a distance in excess of 400 km. Historical magnetometer and Schlumberger Sounding experiments have previously identified elevated conductivities in the Karoo sequences which were attributed to the Whitehill and Prince Albert formations. These carboniferous, transgressive sediments are known to be conductive from borehole conductivity surveys and direct measurements at surface. In order to constrain the conductive properties of these sediments, impedance spectroscopy (IS) experiments were completed on core samples collected from a historical borehole drilled near to the MT profile. Part One of this thesis presents the results of these experiments, which support the proposition that the Whitehill and Prince Albert Formations are responsible for the laterally continuous, sub-horizontal, upper crustal conductor visible in the MT inversion model. Vitrinite reflectance studies were performed on the same samples by the Montanuniversität, in Leoben, these results corroborate the proposition that elevated organic carbon, of meta-anthracite rank, is the primary conductive phase for the Whitehill and Prince Albert formations. Part two of this thesis completed forward modelling exercises using historical aeromagnetic data previously collected across the Beattie Magnetic Anomaly. Preliminary models were unable to fit the geometry of any single magnetic model with conductors present in the MT inversion model discounting the proposition that the SCCB and BMA arise from a single crustal unit. Two constrained models were arrived at through an iterative process that sought a best fit between the measured data and the NVR crustal interpretations. The first model, proposes a largely resistive unit which incorporates portions of elevated crustal conductivity; these conductors are spatially correlated to crustal portions also characterised by high seismic reflectivity. The size of this modelled body suggest the likely host of the BMA is an intermediate plutonic terrane, analogous with the Natal sector of the Namaqua Natal Mobile Belt as well as the Heimefrontfjella in Dronning Maud Land, Antarctica, with magnetite hosted within shear zones. This is in agreement with previous studies. The second model proposes a lower crustal sliver imaged in the NVR data at depths proximal to the Curie Isotherm for magnetite and hematite as the source of the BMA. At these depths geomagnetic properties such as burial magnetisation or thermo-viscous remanent magnetism (TVRM) can potentially be linked to regional scale tectonic processes and can theoretically elevate a body’s net magnetic susceptibility. TVRM has been proposed for long wavelength crustal anomalies elsewhere.
- Full Text:
- Date Issued: 2014
Electrocatalytic behahiour of cobalt tetraamino-phthalocyanine in the presence of a composite of reduced graphene nanosheets and of multi-walled carbon nanotubes
- Nyoni, Stephen, Nyokong, Tebello
- Authors: Nyoni, Stephen , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189784 , vital:44931 , xlink:href="https://doi.org/10.1016/j.electacta.2014.05.093"
- Description: A composite of multi-walled carbon nanotubes (MWCNT) with reduced graphene nanosheets (rGNS-2) was developed in order to minimize the restacking of the latter. The composite was used to modify a glassy carbon electrode (GCE). GCE was further modified with cobalt tetraamino phthalocyanine (CoTAPc). The modified electrode is represented as rGNS-2-MWCNT-CoTAPc-GCE. X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electrochemical microscopy and Raman spectroscopy were used to explore into surface functionalities, morphology and topography of the nanocomposite. The rGNS-2-MWCNT-CoTAPc-GCE had a low limit of detection of 3.32 × 10−8 M towards the detection of paraguat as a test analyte. A mechanism for paraquat detection using an rGNS-2-MWCNT-CoTAPc-GCE is also proposed in this work.
- Full Text:
- Date Issued: 2014
- Authors: Nyoni, Stephen , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189784 , vital:44931 , xlink:href="https://doi.org/10.1016/j.electacta.2014.05.093"
- Description: A composite of multi-walled carbon nanotubes (MWCNT) with reduced graphene nanosheets (rGNS-2) was developed in order to minimize the restacking of the latter. The composite was used to modify a glassy carbon electrode (GCE). GCE was further modified with cobalt tetraamino phthalocyanine (CoTAPc). The modified electrode is represented as rGNS-2-MWCNT-CoTAPc-GCE. X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electrochemical microscopy and Raman spectroscopy were used to explore into surface functionalities, morphology and topography of the nanocomposite. The rGNS-2-MWCNT-CoTAPc-GCE had a low limit of detection of 3.32 × 10−8 M towards the detection of paraguat as a test analyte. A mechanism for paraquat detection using an rGNS-2-MWCNT-CoTAPc-GCE is also proposed in this work.
- Full Text:
- Date Issued: 2014
Electrochemical behaviour of gold nanoparticles and Co tetraaminophthalocyanine on glassy carbon electrode
- Maringa, Audacity, Antunes, Edith M, Nyokong, Tebello
- Authors: Maringa, Audacity , Antunes, Edith M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241573 , vital:50951 , xlink:href="https://doi.org/10.1016/j.electacta.2013.12.132"
- Description: We report on the electrodeposition of gold nanoparticles (AuNPs) onto the glassy carbon electrode (GCE) followed by polymerization of cobalt tetraamino phthalocyanine (CoPc(NH2)4) on top (represented as poly-CoPc(NH2)4-/AuNPs-GCE). The modified electrode where CoPc(NH2)4 is polymerized first followed by deposition of AuNPs is represented as AuNPs/poly-CoPc(NH2)4-GCE. In the absence of AuNPs, the electrode is represented as poly-CoPc(NH2)4-GCE or for AuNPs alone (AuNPs-GCE). The surface coverage was 1.5 × 10−9 mol cm−2 for AuNPs-GCE and 3.0 × 10−9 mol cm−2 for the rest of the modified electrodes. AuNPs/CoPc(NH2)4-GCE exhibited high electrocatalytic activity towards the oxidation of nitrite, with detection potential of 0.76 V. The catalytic rate constant of 3.96 × 107 cm3 mol−1 s−1 was obtained for nitrite oxidation.
- Full Text:
- Date Issued: 2014
- Authors: Maringa, Audacity , Antunes, Edith M , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241573 , vital:50951 , xlink:href="https://doi.org/10.1016/j.electacta.2013.12.132"
- Description: We report on the electrodeposition of gold nanoparticles (AuNPs) onto the glassy carbon electrode (GCE) followed by polymerization of cobalt tetraamino phthalocyanine (CoPc(NH2)4) on top (represented as poly-CoPc(NH2)4-/AuNPs-GCE). The modified electrode where CoPc(NH2)4 is polymerized first followed by deposition of AuNPs is represented as AuNPs/poly-CoPc(NH2)4-GCE. In the absence of AuNPs, the electrode is represented as poly-CoPc(NH2)4-GCE or for AuNPs alone (AuNPs-GCE). The surface coverage was 1.5 × 10−9 mol cm−2 for AuNPs-GCE and 3.0 × 10−9 mol cm−2 for the rest of the modified electrodes. AuNPs/CoPc(NH2)4-GCE exhibited high electrocatalytic activity towards the oxidation of nitrite, with detection potential of 0.76 V. The catalytic rate constant of 3.96 × 107 cm3 mol−1 s−1 was obtained for nitrite oxidation.
- Full Text:
- Date Issued: 2014
Electrochemical inclusion of catechol into singlewalled carbon nanotubes: application for sensors
- Authors: Oni, Joshua , Limson, Janice
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431090 , vital:72743 , xlink:href="10.1109/BioCAS.2014.6981727"
- Description: We report on the use of catechol for the electrochemical activation of acid-functionalised single-walled carbon nanotubes immobilised on glassy carbon electrodes. Following well-published methods for catechol activation of bare glassy carbon electrodes, these studies show the efficacy of extending the method to activation of carbon nanotubes. Voltammetric scans in catechol show an increase in current response of 37 μA for the catechol redox pair over a maximum of three cycles during the catechol activation step. An increase in the ease of electron flow is indicated by a larger value for K app , which corresponds to a decrease in R ct obtained during impedance measurements. Catechol activation enhanced electron transfer, potentially afforded by an ease of electron passage due to a decrease in the resistance of the layer.
- Full Text:
- Date Issued: 2014
- Authors: Oni, Joshua , Limson, Janice
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431090 , vital:72743 , xlink:href="10.1109/BioCAS.2014.6981727"
- Description: We report on the use of catechol for the electrochemical activation of acid-functionalised single-walled carbon nanotubes immobilised on glassy carbon electrodes. Following well-published methods for catechol activation of bare glassy carbon electrodes, these studies show the efficacy of extending the method to activation of carbon nanotubes. Voltammetric scans in catechol show an increase in current response of 37 μA for the catechol redox pair over a maximum of three cycles during the catechol activation step. An increase in the ease of electron flow is indicated by a larger value for K app , which corresponds to a decrease in R ct obtained during impedance measurements. Catechol activation enhanced electron transfer, potentially afforded by an ease of electron passage due to a decrease in the resistance of the layer.
- Full Text:
- Date Issued: 2014
Electron microscopy characterisation of polycrystalline silicon carbide
- Authors: Ndzane, Nolufefe Muriel
- Date: 2014
- Subjects: Electron microscopy , Silicon carbide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10553 , http://hdl.handle.net/10948/d1020634
- Description: This dissertation focuses on an electron microscopy investigation of the microstructure of SiC layers in TRISO coated particles deposited by chemical vapour deposition under different experimental conditions, which include temperature, concentration of gases and deposition time. The polycrystalline β-SiC was deposited from the decomposition of methyl trichlorosilane MTS in the presence of hydrogen (H2) as carrier gas. Scanning electron microscopy (SEM), using the backscattered electron (BSE) mode, was used to image the microstructure of and defects in the SiC layers of TRISO particles. Electron backscatter diffraction (EBSD) in the SEM was used to determine the SiC grain sizes and distribution thereof in TRISO particles deposited under different conditions. For samples with a poor EBSD indexing rate, transmission Kikuchi diffraction and transmission electron microscopy (TEM) investigations were also carried out. From the results, the effects of growth temperature on the SiC microstructure, specifically on the grain size and shape and the porosity were determined. The effects of cooling or non-cooling of the gas inlet nozzle on the SiC microstructure were also investigated. TEM and scanning TEM (STEM) analyses of the SiC layers in TRISO particles were performed to image the defects and reveal the crystallinity of SiC layers. The microstructure and composition of SiC tubes fabricated by reaction bonding (RB) was also investigated by using electron microscopy and Raman spectroscopy. SEM-BSE imaging of RBSiC samples allowed the identification of impurities and free silicon in the RBSiC. Finally, the penetration of the metallic fission product, palladium, in reaction bonded SiC at a temperature of a 1000ºC is determined. A brief comment on the suitability of RBSiC as candidate for fuel cladding in a PWR is made. A short discussion of the suitability of the characterisation techniques used is included at the end.
- Full Text:
- Date Issued: 2014
- Authors: Ndzane, Nolufefe Muriel
- Date: 2014
- Subjects: Electron microscopy , Silicon carbide
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10553 , http://hdl.handle.net/10948/d1020634
- Description: This dissertation focuses on an electron microscopy investigation of the microstructure of SiC layers in TRISO coated particles deposited by chemical vapour deposition under different experimental conditions, which include temperature, concentration of gases and deposition time. The polycrystalline β-SiC was deposited from the decomposition of methyl trichlorosilane MTS in the presence of hydrogen (H2) as carrier gas. Scanning electron microscopy (SEM), using the backscattered electron (BSE) mode, was used to image the microstructure of and defects in the SiC layers of TRISO particles. Electron backscatter diffraction (EBSD) in the SEM was used to determine the SiC grain sizes and distribution thereof in TRISO particles deposited under different conditions. For samples with a poor EBSD indexing rate, transmission Kikuchi diffraction and transmission electron microscopy (TEM) investigations were also carried out. From the results, the effects of growth temperature on the SiC microstructure, specifically on the grain size and shape and the porosity were determined. The effects of cooling or non-cooling of the gas inlet nozzle on the SiC microstructure were also investigated. TEM and scanning TEM (STEM) analyses of the SiC layers in TRISO particles were performed to image the defects and reveal the crystallinity of SiC layers. The microstructure and composition of SiC tubes fabricated by reaction bonding (RB) was also investigated by using electron microscopy and Raman spectroscopy. SEM-BSE imaging of RBSiC samples allowed the identification of impurities and free silicon in the RBSiC. Finally, the penetration of the metallic fission product, palladium, in reaction bonded SiC at a temperature of a 1000ºC is determined. A brief comment on the suitability of RBSiC as candidate for fuel cladding in a PWR is made. A short discussion of the suitability of the characterisation techniques used is included at the end.
- Full Text:
- Date Issued: 2014
Electronic Governance (E-Governance) as a Public Sector Management Tool for service provision in Buffalo City Metropolitan Municipality
- Authors: Moyo, Thokozani P
- Date: 2014
- Language: English
- Type: Thesis , Masters , MPA
- Identifier: vital:11714 , http://hdl.handle.net/10353/d1015268
- Description: The study explores the use of Electronic governance (E-governance) as a Public Sector management tool for service provision in the Buffalo City Metropolitan Municipality. The main research question being pursued sought to find out the extent to which E-governance can be an effective tool for public sector management and service provision in the municipality. The study used both quantitative data (obtained through questionnaire survey) and qualitative data (through in-depth responses from municipality employees). The findings of the study seem to indicate that electronic governance is being utilised by a lesser percentage of citizens although it seems to be slowly gaining popularity with the highly educated and younger members of the public. Some members of the communities were still adamant to using online resources for different reasons. The study also reveals some challenges such as poverty, inequality and illiteracy as some of the hindrances to e-government. However, there is a degree of success of electronic governance in the municipality as evidenced by the percentage of the population now using the online transactions. A lot needs to be done in order to view e-governance as a true success in this municipality of Buffalo City Metropolitan if services are to be delivered effectively and efficiently to the people. It is therefore strongly recommended that there is a need to put in place good educational measures to ensure that the citizens are informed about various ways of doing online transactions with the municipality other than physically going there.
- Full Text:
- Date Issued: 2014
- Authors: Moyo, Thokozani P
- Date: 2014
- Language: English
- Type: Thesis , Masters , MPA
- Identifier: vital:11714 , http://hdl.handle.net/10353/d1015268
- Description: The study explores the use of Electronic governance (E-governance) as a Public Sector management tool for service provision in the Buffalo City Metropolitan Municipality. The main research question being pursued sought to find out the extent to which E-governance can be an effective tool for public sector management and service provision in the municipality. The study used both quantitative data (obtained through questionnaire survey) and qualitative data (through in-depth responses from municipality employees). The findings of the study seem to indicate that electronic governance is being utilised by a lesser percentage of citizens although it seems to be slowly gaining popularity with the highly educated and younger members of the public. Some members of the communities were still adamant to using online resources for different reasons. The study also reveals some challenges such as poverty, inequality and illiteracy as some of the hindrances to e-government. However, there is a degree of success of electronic governance in the municipality as evidenced by the percentage of the population now using the online transactions. A lot needs to be done in order to view e-governance as a true success in this municipality of Buffalo City Metropolitan if services are to be delivered effectively and efficiently to the people. It is therefore strongly recommended that there is a need to put in place good educational measures to ensure that the citizens are informed about various ways of doing online transactions with the municipality other than physically going there.
- Full Text:
- Date Issued: 2014
Electropolymerized Fluorinated Aniline-Based Fiber for Headspace Solid-Phase Microextraction and Gas Chromatographic Determination of Benzaldehyde in Injectable Pharmaceutical Formulations
- Mohammadi, Ali, Mohammadi, Somayeh, Moghaddam, Bayandori A, Masoumi, Vahideh, Walker, Roderick B
- Authors: Mohammadi, Ali , Mohammadi, Somayeh , Moghaddam, Bayandori A , Masoumi, Vahideh , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184120 , vital:44175 , xlink:href="https://doi.org/10.1093/chromsci/bmt152"
- Description: In this study, a simple method was developed and validated to detect trace levels of benzaldehyde in injectable pharmaceutical formulations by solid-phase microextraction coupled with gas chromatography–flame ionization detector. Polyaniline was electrodeposited on a platinum wire in trifluoroacetic acid solvent by cyclic voltammetry technique. This fiber shows high thermal and mechanical stability and high performance in extraction of benzaldehyde. Extraction and desorption time and temperature, salt effect and gas chromatography parameters were optimized as key parameters. At the optimum conditions, the fiber shows good linearity between peak area ratio of benzaldehyde/3-chlorobenzaldehyde and benzaldehyde concentration in the range of 50–800 ng/mL with percent relative standard deviation values ranging from 0.75 to 8.64% (n 5 3). The limits of quantitation and detection were 50 and 16 ng/mL, respectively. The method has the requisite selectivity, sensitivity, accuracy and precision to assay benzaldehyde in injectable pharmaceutical dosage forms.
- Full Text:
- Date Issued: 2014
- Authors: Mohammadi, Ali , Mohammadi, Somayeh , Moghaddam, Bayandori A , Masoumi, Vahideh , Walker, Roderick B
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184120 , vital:44175 , xlink:href="https://doi.org/10.1093/chromsci/bmt152"
- Description: In this study, a simple method was developed and validated to detect trace levels of benzaldehyde in injectable pharmaceutical formulations by solid-phase microextraction coupled with gas chromatography–flame ionization detector. Polyaniline was electrodeposited on a platinum wire in trifluoroacetic acid solvent by cyclic voltammetry technique. This fiber shows high thermal and mechanical stability and high performance in extraction of benzaldehyde. Extraction and desorption time and temperature, salt effect and gas chromatography parameters were optimized as key parameters. At the optimum conditions, the fiber shows good linearity between peak area ratio of benzaldehyde/3-chlorobenzaldehyde and benzaldehyde concentration in the range of 50–800 ng/mL with percent relative standard deviation values ranging from 0.75 to 8.64% (n 5 3). The limits of quantitation and detection were 50 and 16 ng/mL, respectively. The method has the requisite selectivity, sensitivity, accuracy and precision to assay benzaldehyde in injectable pharmaceutical dosage forms.
- Full Text:
- Date Issued: 2014
Electrospun fiber based colorimetric probes for aspartate aminotransferase and I7ß-estradiol
- Authors: Pule, Bellah Oreeditse
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54869 , vital:26623
- Description: Fabrication, characterization and application of electrospun polymer composite based colorimetric probes are presented in this thesis. The first part of the thesis involved the development of a protocol for in situ reduction of gold trication (Au³+) into metallic gold atoms with sodium borohydride. The prepared PS-Au NPs showed an SPR band at 542 nm. Furthermore the absorbance of the colloidal Au NPs in polystyrene exhibited a good linear correlation (r2 = 0.9934) to E2 concentration in the range 5 to 50 ppb. The lowest naked eye detection limit was found to be 0.5 ppb and could further be easily monitored by UV-vis spectrophotometer. Upon interaction with E2 Au NPs aggregated to give nanoparticle clusters, confirmed through TEM analysis. Different concentrations of Au NPs were found to have a significant effect on the conductivity of the PS-Au NPs solution. At low concentrations of Au NPs (0.002, 0.015 and 0.025% w/v) PS-Au NPs solution could be electrospun without clogging. The FE-SEM images showed a non-beaded morphology of PS-Au NPs composite fibers. Upon interaction of the colorimetric probe strips with various E2 concentrations it was observed that with increasing E2 concentrations (50 ng/ml to 1000 µg/ml) the colour of the probe changed gradually from white to shades of pink and eventually to shades of blue at higher E2 concentrations. The visible cut-off concentration was 100 ng/ml. The second component of the thesis focussed on the development of diazonium dye-nylon 6 colorimetric probe for aspartate aminotransferase. At optimal pH 7.4 the enzyme was stable, highly active and catalyzed a reaction that was susceptible to detailed kinetic analysis by continuous optical methods. The KM values for L-aspartate, a- ketoglutarate and oxaloacetate were 2.60, 0.59 and 0.066 mM, respectively. On the basis of these KM values the solid-state colorimetric probe was developed. A colour change occurred when an electrospun dye-N 6 probes were exposed to visibly detectable concentrations of oxaloacetate, an AST-catalyzed reaction product. While monitoring AST activity at 530 run, a linear relation was obtained between oxaloacetate concentrations ranging from 0.4 - 7.4 µg/ml. Naked eye detection limit of 2.4 µg/ml oxalaoacetate equivalence of 10 times the normal AST activity was attained. The colorimetric probe was in addition, tested against co-substrates aspartate, ketoglutarate and a variety of other compounds such as alanine, pryruvate, as well as glutamic, malaic and succinic acids known to interfere with AST activity. Each compound elicited a distinct and unambiguous colour change upon interaction with the colorimetric probe. Further X-ray powder diffraction (XRD), duNouy ring tensiometer, Brunauer- Emmett- Teller (BET) and energy dispersive X-ray spectroscopy (EDS/EDX) characterization confirmed composition and stability of the colorimetric probes. Colorimetric probes developed in this thesis are relatively cost effective, simple and "rugged" for measurement of analytes with visual detection without sample pretreatment in matrices, such as plasma and dairy effluents. The probes warrant further investigation as they have shown potential and offer a promising solid-state platform for both clinical diagnostics and environmental monitoring.
- Full Text:
- Date Issued: 2014
- Authors: Pule, Bellah Oreeditse
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54869 , vital:26623
- Description: Fabrication, characterization and application of electrospun polymer composite based colorimetric probes are presented in this thesis. The first part of the thesis involved the development of a protocol for in situ reduction of gold trication (Au³+) into metallic gold atoms with sodium borohydride. The prepared PS-Au NPs showed an SPR band at 542 nm. Furthermore the absorbance of the colloidal Au NPs in polystyrene exhibited a good linear correlation (r2 = 0.9934) to E2 concentration in the range 5 to 50 ppb. The lowest naked eye detection limit was found to be 0.5 ppb and could further be easily monitored by UV-vis spectrophotometer. Upon interaction with E2 Au NPs aggregated to give nanoparticle clusters, confirmed through TEM analysis. Different concentrations of Au NPs were found to have a significant effect on the conductivity of the PS-Au NPs solution. At low concentrations of Au NPs (0.002, 0.015 and 0.025% w/v) PS-Au NPs solution could be electrospun without clogging. The FE-SEM images showed a non-beaded morphology of PS-Au NPs composite fibers. Upon interaction of the colorimetric probe strips with various E2 concentrations it was observed that with increasing E2 concentrations (50 ng/ml to 1000 µg/ml) the colour of the probe changed gradually from white to shades of pink and eventually to shades of blue at higher E2 concentrations. The visible cut-off concentration was 100 ng/ml. The second component of the thesis focussed on the development of diazonium dye-nylon 6 colorimetric probe for aspartate aminotransferase. At optimal pH 7.4 the enzyme was stable, highly active and catalyzed a reaction that was susceptible to detailed kinetic analysis by continuous optical methods. The KM values for L-aspartate, a- ketoglutarate and oxaloacetate were 2.60, 0.59 and 0.066 mM, respectively. On the basis of these KM values the solid-state colorimetric probe was developed. A colour change occurred when an electrospun dye-N 6 probes were exposed to visibly detectable concentrations of oxaloacetate, an AST-catalyzed reaction product. While monitoring AST activity at 530 run, a linear relation was obtained between oxaloacetate concentrations ranging from 0.4 - 7.4 µg/ml. Naked eye detection limit of 2.4 µg/ml oxalaoacetate equivalence of 10 times the normal AST activity was attained. The colorimetric probe was in addition, tested against co-substrates aspartate, ketoglutarate and a variety of other compounds such as alanine, pryruvate, as well as glutamic, malaic and succinic acids known to interfere with AST activity. Each compound elicited a distinct and unambiguous colour change upon interaction with the colorimetric probe. Further X-ray powder diffraction (XRD), duNouy ring tensiometer, Brunauer- Emmett- Teller (BET) and energy dispersive X-ray spectroscopy (EDS/EDX) characterization confirmed composition and stability of the colorimetric probes. Colorimetric probes developed in this thesis are relatively cost effective, simple and "rugged" for measurement of analytes with visual detection without sample pretreatment in matrices, such as plasma and dairy effluents. The probes warrant further investigation as they have shown potential and offer a promising solid-state platform for both clinical diagnostics and environmental monitoring.
- Full Text:
- Date Issued: 2014