Identification of differentially expressed proteins involved in wheat (Triticum aestivum) resistance against Russian Wheat Aphid (Diuraphis noxia) SA2 using SWATH-MS analysis
- Authors: Ntlokwana, Sitha Emmanuel
- Date: 2020
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18872 , vital:42888
- Description: Wheat (Triticum aestivum) is the second most-consumed cereal crop in the world, second only to maize. In South Africa it is mainly produced in three provinces; the Free State, Western Cape, and the Northen Cape. The average total land area used for wheat cultivation in these three Provinces, is 533 000 hectares, with a resultant annual production of between 1.3 to 2 million tons. The total wheat requirement in South Africa is currently 2.7 million tons according to the production of wheat guidelines published by the Department of Agriculture, Forestry and Fisheries, which is higher than the total annual production. One of the primary reasons that contribute to the lower production levels is insect and pest infestation, in particular, the Russian wheat aphid (Diurophis noxis), which can result in crop loss of up to sixty percent. Russian wheat aphids (RWA) are invasive insects that feed on the phloem of the plant through their specialised thin stylet-like mouthparts and release toxic agents contained in their saliva during feeding, which disrupt cellular functions inside the host plant. This damage leads to symptoms like; chlorosis, necrosis, wilting, stunting and curling of leaves, also known as leaf rolling. This study aimed to identify differentially expressed proteins in resistant and susceptible wheat (Triticum aestivum) cultivars during Russian wheat aphid Biotype South African 2 (RWA-SA2) infestation, in order to identify proteins involved in the wheat resistant mechanism against RWA-SA2. Two wheat cultivars SST398 (resistant to RWA-SA2) and SST356 (susceptible to RWA-SA2) were used, and a total number of 126 plants were planted and divided according to four different harvest times (Control day 0; day 5; day 7 and day 12). The wheat plants were infested with approximately 10 aphids per plant at the three-leaf stage, and placed within an insect cage inside a growth chamber (Conviron, Winnipeg, Canada) set at 24ºC, light intensity of 352 µmol.m-2.sec-1, ambient CO2 levels (410 ppm) and humidity of 60% with a 16h/8h day/night cycle. Wheat leaves were harvested at various time frames, and total protein extraction was performed. The protein samples were reduced with 10 mM dithiothreitol (DTT) and alkylated with 30 mM iodoacetamide (IAA). Sample clean-up and on-bead trypsin digest were performed on megReSyn Hilic columns, over four hours. The resultant peptides were vacuum dried and resuspended in 2% acetonitrile (ACN) before submitting them to LC-MS/MS (SWATH) for analysis. A total number of 611 proteins were differentially expressed, of which 19 were identified to be involved in the resistance response of wheat, and an additional 20 involved in biotic stress responses. This study showed that reactive oxidative species (ROS) such as hydrogen peroxide and hydroxyl radicals (OH-) play a significant role in the early stages of wheat resistance against RWA-SA2 infestation. They are involved in cell wall strengthening, activation of defence genes, involvement of phytohormone signals such as salicylic and jasmonic acid, which also mediates the systemic defences such as, systemic acquired resistance (SAR), leading to the expression of pathogen-related proteins such as (thaumatin-like proteins, oxalate oxidase, defensin, chitinase, and thionins). Although up-regulation of photosynthesis proteins such as (chlorophyll a/b binding protein, photosystem I and II, rubisco and divinyl chlorophyllide a, and 8 vinyl-reductase) were seen on both infested cultivars (susceptible and resistance), higher numbers of these classes of proteins were identified in the resistance cultivar, suggesting that they also play a critical role in resistance. In conclusion, the SWATH analysis used in this study was able to identify numerous proteins involved in the wheat resistance mechanism against RWA-SA2, most of which have not yet been reported to be involved in either biotic stress or RWA-SA2 resistance responses. Future studies are required to biochemically confirm the involvement of these enzymes and proteins the specific metabolic pathways where they are found, in the wheat resistance mechanism against Russian wheat aphid Biotype 2
- Full Text:
- Date Issued: 2020
- Authors: Ntlokwana, Sitha Emmanuel
- Date: 2020
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18872 , vital:42888
- Description: Wheat (Triticum aestivum) is the second most-consumed cereal crop in the world, second only to maize. In South Africa it is mainly produced in three provinces; the Free State, Western Cape, and the Northen Cape. The average total land area used for wheat cultivation in these three Provinces, is 533 000 hectares, with a resultant annual production of between 1.3 to 2 million tons. The total wheat requirement in South Africa is currently 2.7 million tons according to the production of wheat guidelines published by the Department of Agriculture, Forestry and Fisheries, which is higher than the total annual production. One of the primary reasons that contribute to the lower production levels is insect and pest infestation, in particular, the Russian wheat aphid (Diurophis noxis), which can result in crop loss of up to sixty percent. Russian wheat aphids (RWA) are invasive insects that feed on the phloem of the plant through their specialised thin stylet-like mouthparts and release toxic agents contained in their saliva during feeding, which disrupt cellular functions inside the host plant. This damage leads to symptoms like; chlorosis, necrosis, wilting, stunting and curling of leaves, also known as leaf rolling. This study aimed to identify differentially expressed proteins in resistant and susceptible wheat (Triticum aestivum) cultivars during Russian wheat aphid Biotype South African 2 (RWA-SA2) infestation, in order to identify proteins involved in the wheat resistant mechanism against RWA-SA2. Two wheat cultivars SST398 (resistant to RWA-SA2) and SST356 (susceptible to RWA-SA2) were used, and a total number of 126 plants were planted and divided according to four different harvest times (Control day 0; day 5; day 7 and day 12). The wheat plants were infested with approximately 10 aphids per plant at the three-leaf stage, and placed within an insect cage inside a growth chamber (Conviron, Winnipeg, Canada) set at 24ºC, light intensity of 352 µmol.m-2.sec-1, ambient CO2 levels (410 ppm) and humidity of 60% with a 16h/8h day/night cycle. Wheat leaves were harvested at various time frames, and total protein extraction was performed. The protein samples were reduced with 10 mM dithiothreitol (DTT) and alkylated with 30 mM iodoacetamide (IAA). Sample clean-up and on-bead trypsin digest were performed on megReSyn Hilic columns, over four hours. The resultant peptides were vacuum dried and resuspended in 2% acetonitrile (ACN) before submitting them to LC-MS/MS (SWATH) for analysis. A total number of 611 proteins were differentially expressed, of which 19 were identified to be involved in the resistance response of wheat, and an additional 20 involved in biotic stress responses. This study showed that reactive oxidative species (ROS) such as hydrogen peroxide and hydroxyl radicals (OH-) play a significant role in the early stages of wheat resistance against RWA-SA2 infestation. They are involved in cell wall strengthening, activation of defence genes, involvement of phytohormone signals such as salicylic and jasmonic acid, which also mediates the systemic defences such as, systemic acquired resistance (SAR), leading to the expression of pathogen-related proteins such as (thaumatin-like proteins, oxalate oxidase, defensin, chitinase, and thionins). Although up-regulation of photosynthesis proteins such as (chlorophyll a/b binding protein, photosystem I and II, rubisco and divinyl chlorophyllide a, and 8 vinyl-reductase) were seen on both infested cultivars (susceptible and resistance), higher numbers of these classes of proteins were identified in the resistance cultivar, suggesting that they also play a critical role in resistance. In conclusion, the SWATH analysis used in this study was able to identify numerous proteins involved in the wheat resistance mechanism against RWA-SA2, most of which have not yet been reported to be involved in either biotic stress or RWA-SA2 resistance responses. Future studies are required to biochemically confirm the involvement of these enzymes and proteins the specific metabolic pathways where they are found, in the wheat resistance mechanism against Russian wheat aphid Biotype 2
- Full Text:
- Date Issued: 2020
Porphyrin dimers with a bridging chiral amide-bonded benzo-moiety
- Liang, Xu, Qin, Mingfeng, Zhou, Lin, Liu, Tingting, Li, Minzhi, Mack, John, Ndebele, Nobuhle, Nyokong, Tebello, Zhu, Weihua
- Authors: Liang, Xu , Qin, Mingfeng , Zhou, Lin , Liu, Tingting , Li, Minzhi , Mack, John , Ndebele, Nobuhle , Nyokong, Tebello , Zhu, Weihua
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233433 , vital:50090 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.02.043"
- Description: The facile synthesis and characterization of four porphyrin dimers which introduced stereomeric centers with chiral amide-bonded para- and meta-disubstituted benzo-moiety is reported. Trends in the electronic structures and optical and redox properties are analyzed through a comparison with theoretical calculations to explore the effect of positional isomerism of the bridging benzene rings.
- Full Text:
- Date Issued: 2018
- Authors: Liang, Xu , Qin, Mingfeng , Zhou, Lin , Liu, Tingting , Li, Minzhi , Mack, John , Ndebele, Nobuhle , Nyokong, Tebello , Zhu, Weihua
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233433 , vital:50090 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.02.043"
- Description: The facile synthesis and characterization of four porphyrin dimers which introduced stereomeric centers with chiral amide-bonded para- and meta-disubstituted benzo-moiety is reported. Trends in the electronic structures and optical and redox properties are analyzed through a comparison with theoretical calculations to explore the effect of positional isomerism of the bridging benzene rings.
- Full Text:
- Date Issued: 2018
A taxonomic revision of the southern African endemic genus Gazania (Asteraceae) based on morphometric, genetic and phylogeographic data
- Authors: Howis, Seranne
- Date: 2007
- Subjects: Compositae Plant genetics DNA Endemic plants -- South Africa Plant ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4200 , http://hdl.handle.net/10962/d1003769
- Description: Gazania is a small genus of the subtribe Gorteriinae, tribe Arctoteae, that is endemic to southern Africa. The genus was last revised in 1959 by Roessler, who noted that delimitation of the species of Gazania can be “extraordinarily difficult”. Morphometric data was collected to test the reality of the 16 species as delimited by Roessler, who based species boundaries on morphological characters. Only six taxa were found to be morphologically distinct, while the remaining samples showed no species cohesion. DNA sequence data from two nuclear spacer regions (ITS and ETS) and four chloroplast noncoding regions (the trnL and rpS16 introns, and the psbA-trnH and trnL-F spacers) of 43 samples were utilised to create a species level phylogeny and to investigate correlations between genetically delimited units and morphologically defined taxa. DNA sequence data reveal that seven species (as delimited by Roessler) are morphologically and genetically distinct. The remaining nine of Roessler’s species fall into a morphologically and genetically overlapping continuum that forms an ochlospecies. Phylogeographic methods (based on an expanded ITS and ETS DNA sequence data set from 169 samples) were employed to further resolve the limits of species, with special focus on the clades within the ochlospecies. These genetically defined clades were correlated with their geographical distributions, and in combination with molecular dating techniques, used to elucidate the recent climatic or environmental factors that may have shaped the phylogeographic structure of the genus. Phylogeographic patterns and molecular dating reveals that the genus Gazania is an example of a South African endemic clade that has undergone episodic cladogenesis in response to fluctuating climatic conditions over the last seven million years. The ochlospecies within Gazania is a result of repeated cycles of climate driven isolation in refugia and subsequent expansion and hybridization events during the Pliocene and Pleistocene. Comparisons with phylogeographic studies on other organisms reveal a common pattern indicative of the presence and evolutionary importance of an ancestral refugium in the arid Richtersveld / Namib region of southern Africa.
- Full Text:
- Date Issued: 2007
- Authors: Howis, Seranne
- Date: 2007
- Subjects: Compositae Plant genetics DNA Endemic plants -- South Africa Plant ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4200 , http://hdl.handle.net/10962/d1003769
- Description: Gazania is a small genus of the subtribe Gorteriinae, tribe Arctoteae, that is endemic to southern Africa. The genus was last revised in 1959 by Roessler, who noted that delimitation of the species of Gazania can be “extraordinarily difficult”. Morphometric data was collected to test the reality of the 16 species as delimited by Roessler, who based species boundaries on morphological characters. Only six taxa were found to be morphologically distinct, while the remaining samples showed no species cohesion. DNA sequence data from two nuclear spacer regions (ITS and ETS) and four chloroplast noncoding regions (the trnL and rpS16 introns, and the psbA-trnH and trnL-F spacers) of 43 samples were utilised to create a species level phylogeny and to investigate correlations between genetically delimited units and morphologically defined taxa. DNA sequence data reveal that seven species (as delimited by Roessler) are morphologically and genetically distinct. The remaining nine of Roessler’s species fall into a morphologically and genetically overlapping continuum that forms an ochlospecies. Phylogeographic methods (based on an expanded ITS and ETS DNA sequence data set from 169 samples) were employed to further resolve the limits of species, with special focus on the clades within the ochlospecies. These genetically defined clades were correlated with their geographical distributions, and in combination with molecular dating techniques, used to elucidate the recent climatic or environmental factors that may have shaped the phylogeographic structure of the genus. Phylogeographic patterns and molecular dating reveals that the genus Gazania is an example of a South African endemic clade that has undergone episodic cladogenesis in response to fluctuating climatic conditions over the last seven million years. The ochlospecies within Gazania is a result of repeated cycles of climate driven isolation in refugia and subsequent expansion and hybridization events during the Pliocene and Pleistocene. Comparisons with phylogeographic studies on other organisms reveal a common pattern indicative of the presence and evolutionary importance of an ancestral refugium in the arid Richtersveld / Namib region of southern Africa.
- Full Text:
- Date Issued: 2007
The design of a building linking central and the Baakens river mouth
- Authors: De Klerk, Paul
- Date: 2019
- Subjects: Architecture -- South Africa -- Port Elizabeth -- 21st century , Urban renewal -- South Africa -- Port Elizabeth , Architecture -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MArch
- Identifier: http://hdl.handle.net/10948/43138 , vital:36746
- Description: This treatsie focuses around the reationship of the Baakens Valley and the historical core and their respective declined states that has been affected through shifts in urban development and urban sprawl. Urban centres are moving away from the core decentralizing activity affecting the central areas allowing people-orientated environments to decline as an outcome of urbanism. Settlement expansion was forced along the coast due to topography Decentralised city growth with urban sprawl far from the historical core. New centres developed within residential realms detracted from people returning to the historical core Increased major arterial routes diminished density through vehicular orientated living spaces vs the density of the historical core orientated to the pedestian and mixed use activity City centre deteriorated due to Urban expansion and activity centres leaving the CBD resulting in a dilapidated city core.
- Full Text:
- Date Issued: 2019
- Authors: De Klerk, Paul
- Date: 2019
- Subjects: Architecture -- South Africa -- Port Elizabeth -- 21st century , Urban renewal -- South Africa -- Port Elizabeth , Architecture -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MArch
- Identifier: http://hdl.handle.net/10948/43138 , vital:36746
- Description: This treatsie focuses around the reationship of the Baakens Valley and the historical core and their respective declined states that has been affected through shifts in urban development and urban sprawl. Urban centres are moving away from the core decentralizing activity affecting the central areas allowing people-orientated environments to decline as an outcome of urbanism. Settlement expansion was forced along the coast due to topography Decentralised city growth with urban sprawl far from the historical core. New centres developed within residential realms detracted from people returning to the historical core Increased major arterial routes diminished density through vehicular orientated living spaces vs the density of the historical core orientated to the pedestian and mixed use activity City centre deteriorated due to Urban expansion and activity centres leaving the CBD resulting in a dilapidated city core.
- Full Text:
- Date Issued: 2019
Effect of a low density dust shell on the propagation of gravitational waves:
- Bishop, Nigel T, van der Walt, Petrus J, Naidoo, Monos
- Authors: Bishop, Nigel T , van der Walt, Petrus J , Naidoo, Monos
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159935 , vital:40357 , https://0-doi.org.wam.seals.ac.za/10.1007/s10714-020-02740-9
- Description: Using the Bondi-Sachs formalism, the problem of a gravitational wave source surrounded by a spherical dust shell is considered. Using linearized perturbation theory, the geometry is found in the regions: in the shell, exterior to the shell, and interior to the shell. It is found that the dust shell causes the gravitational wave to be modified both in magnitude and phase, but without any energy being transferred to or from the dust.
- Full Text:
- Date Issued: 2020
- Authors: Bishop, Nigel T , van der Walt, Petrus J , Naidoo, Monos
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/159935 , vital:40357 , https://0-doi.org.wam.seals.ac.za/10.1007/s10714-020-02740-9
- Description: Using the Bondi-Sachs formalism, the problem of a gravitational wave source surrounded by a spherical dust shell is considered. Using linearized perturbation theory, the geometry is found in the regions: in the shell, exterior to the shell, and interior to the shell. It is found that the dust shell causes the gravitational wave to be modified both in magnitude and phase, but without any energy being transferred to or from the dust.
- Full Text:
- Date Issued: 2020
Passive acoustic monitoring of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay: temporal patterns and group dynamics
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
Apneic Bradycardia : terrestrial and aquatic responses in man under working conditions
- Authors: Manley, Elizabeth
- Date: 1989
- Subjects: Apnea Respiration -- Measurement Heart rate monitoring Work -- Physiological aspects Underwater -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5098 , http://hdl.handle.net/10962/d1001838
- Description: The focus of this research was the reappraisal in physiological and psychophysical terms of current equivocal theories regarding the onset, course and termination of apneic bradycardia. Sixteen healthy male subjects participated in four separate testing sessions . Maximal oxygen consumption (VO₂ max) was measured on land and underwater using an identical direct, continuous progressive cycle ergometer test. On each of two other occasions subjects exercised in either environment at 50, 70 and 90% of the appropriate VO₂ max, during which time heart rate was continuously recorded. An initial apneic bout at each exercise intensity was followed by performance of the same workload without apnea for an equivalent period of time. Ratings of perceived exertion (RPE) were also monitored. While apneic bradycardia occurred at each exercise intensity studied underwater, it was apparent only at 50% VO₂ max on land. With the exception of between 50 and 90% VO₂ max on land, the mean apneic heart rates did not differ with varying exercise intensity (p<0.05); nor did the lowest heart rate recorded, although this was lower underwater than on land. Apart from 70% VO₂ max on land, apneic heart rates were lower than the equivalent values measured during exercise without apnea. Land and underwater heart rates during apneic and non-apneic conditions did not differ until 90% VO₂ max. The effects of increasing exercise intensity upon the onset of bradycardia were evident in that it occurred earlier at 50% VO₂ max underwater than at the heavier workloads, and only at 50% VO₂ max on land. The mean breath-hold duration did not differ between the land and underwater environments, nor was it affected by increasing exercise intensity. The order in which breath-holds was performed did not alter the length of apnea. Land and underwater RPE did not differ and increased with increasing exercise intensity in both environments. During apneic exercise RPE was greater than the equivalent exercise without apnea. Twelve of the original 16 subjects were divided equally into two groups on the basis of vital capacity expressed relative to body surface area. Vital capacity was measured during the first laboratory session. Neither the mean heart rate response to apneic exercise at 50% V0₂ max in both environments, nor the lowest heart rates recorded differed between groups, prompting the conclusion that lung volume did not affect apneic bradycardia. Despite a longer breath-hold duration for Group A (large relative lung volume) than Group B (small relative lung volume), the onset point of bradycardia was the same for either group when expressed relative to total breath-hold duration
- Full Text:
- Date Issued: 1989
- Authors: Manley, Elizabeth
- Date: 1989
- Subjects: Apnea Respiration -- Measurement Heart rate monitoring Work -- Physiological aspects Underwater -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5098 , http://hdl.handle.net/10962/d1001838
- Description: The focus of this research was the reappraisal in physiological and psychophysical terms of current equivocal theories regarding the onset, course and termination of apneic bradycardia. Sixteen healthy male subjects participated in four separate testing sessions . Maximal oxygen consumption (VO₂ max) was measured on land and underwater using an identical direct, continuous progressive cycle ergometer test. On each of two other occasions subjects exercised in either environment at 50, 70 and 90% of the appropriate VO₂ max, during which time heart rate was continuously recorded. An initial apneic bout at each exercise intensity was followed by performance of the same workload without apnea for an equivalent period of time. Ratings of perceived exertion (RPE) were also monitored. While apneic bradycardia occurred at each exercise intensity studied underwater, it was apparent only at 50% VO₂ max on land. With the exception of between 50 and 90% VO₂ max on land, the mean apneic heart rates did not differ with varying exercise intensity (p<0.05); nor did the lowest heart rate recorded, although this was lower underwater than on land. Apart from 70% VO₂ max on land, apneic heart rates were lower than the equivalent values measured during exercise without apnea. Land and underwater heart rates during apneic and non-apneic conditions did not differ until 90% VO₂ max. The effects of increasing exercise intensity upon the onset of bradycardia were evident in that it occurred earlier at 50% VO₂ max underwater than at the heavier workloads, and only at 50% VO₂ max on land. The mean breath-hold duration did not differ between the land and underwater environments, nor was it affected by increasing exercise intensity. The order in which breath-holds was performed did not alter the length of apnea. Land and underwater RPE did not differ and increased with increasing exercise intensity in both environments. During apneic exercise RPE was greater than the equivalent exercise without apnea. Twelve of the original 16 subjects were divided equally into two groups on the basis of vital capacity expressed relative to body surface area. Vital capacity was measured during the first laboratory session. Neither the mean heart rate response to apneic exercise at 50% V0₂ max in both environments, nor the lowest heart rates recorded differed between groups, prompting the conclusion that lung volume did not affect apneic bradycardia. Despite a longer breath-hold duration for Group A (large relative lung volume) than Group B (small relative lung volume), the onset point of bradycardia was the same for either group when expressed relative to total breath-hold duration
- Full Text:
- Date Issued: 1989
Code-switching as a pedagogical strategy in classroom settings: the case of township schools in a South African Metropolitan Municipality
- Authors: Marawu, Sithembele
- Date: 2018
- Subjects: Code switching (Linguistics) , Multilingual education -- South Africa , Education, Bilingual -- South Africa , Language and languages -- Study and teaching -- Bilingual method , English language -- Social aspects -- South Africa , Language and education -- South Africa , Language and education -- Social aspects -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62406 , vital:28173
- Description: The purpose of this study was to explore the use of code-switching as a pedagogical strategy in bi/multilingual classroom settings. It was prompted by the widespread use of codeswitching (CS) in classrooms, particularly in South African rural and township schools. This study highlighted that learners from disadvantaged backgrounds struggle to learn through the medium of English but aspire to acquire it because of its association with socio-economic advancement. However, poor proficiency in English excludes them from being part of the country's economy. Research studies show that there is a shift from the old orthodoxy which perceived CS as undesirable in classrooms to a new orthodoxy that acknowledges its academic contribution in classrooms. Although more research on classroom CS has been done, this study identified the need for development of new strategies on how to use CS effectively in classrooms as a linguistic and pedagogical resource. In line with critical classroom ethnography, qualitative interpretation of data was used to understand the teachers' discourse behaviour. Additionally, non-probability sampling - specifically purposive sampling - was used to collect data. These methods and approaches assisted in the analysis of the discourse of the three teachers who served as units of analysis in this study. These teachers relied on CS to impart the content of their subjects to the learners. It transpired from data analysis that teachers use CS in classrooms to achieve various functions like social and pedagogical functions. Another finding is that the switches teachers make do not affect the syntactic structure of the matrix language. Moreover, CS enhances understanding of the subject matter. This study concludes by stating that as learners are emergent bilinguals, additive bilingualism would be more ideal in the South African situation than subtractive bilingualism which parents and learners seem to prefer. Lastly, there is a need to harness CS as a communicative and pedagogical resource in classrooms.
- Full Text:
- Date Issued: 2018
- Authors: Marawu, Sithembele
- Date: 2018
- Subjects: Code switching (Linguistics) , Multilingual education -- South Africa , Education, Bilingual -- South Africa , Language and languages -- Study and teaching -- Bilingual method , English language -- Social aspects -- South Africa , Language and education -- South Africa , Language and education -- Social aspects -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62406 , vital:28173
- Description: The purpose of this study was to explore the use of code-switching as a pedagogical strategy in bi/multilingual classroom settings. It was prompted by the widespread use of codeswitching (CS) in classrooms, particularly in South African rural and township schools. This study highlighted that learners from disadvantaged backgrounds struggle to learn through the medium of English but aspire to acquire it because of its association with socio-economic advancement. However, poor proficiency in English excludes them from being part of the country's economy. Research studies show that there is a shift from the old orthodoxy which perceived CS as undesirable in classrooms to a new orthodoxy that acknowledges its academic contribution in classrooms. Although more research on classroom CS has been done, this study identified the need for development of new strategies on how to use CS effectively in classrooms as a linguistic and pedagogical resource. In line with critical classroom ethnography, qualitative interpretation of data was used to understand the teachers' discourse behaviour. Additionally, non-probability sampling - specifically purposive sampling - was used to collect data. These methods and approaches assisted in the analysis of the discourse of the three teachers who served as units of analysis in this study. These teachers relied on CS to impart the content of their subjects to the learners. It transpired from data analysis that teachers use CS in classrooms to achieve various functions like social and pedagogical functions. Another finding is that the switches teachers make do not affect the syntactic structure of the matrix language. Moreover, CS enhances understanding of the subject matter. This study concludes by stating that as learners are emergent bilinguals, additive bilingualism would be more ideal in the South African situation than subtractive bilingualism which parents and learners seem to prefer. Lastly, there is a need to harness CS as a communicative and pedagogical resource in classrooms.
- Full Text:
- Date Issued: 2018
Borneol-triarylcorrole hybrids with chiral-optical response and anticancer behaviours
- Fu, Bo, Wang, Lin, Yu, Xiaoxiao, Fang, Xianying, Mack, John, Dingiswayo, Somila, Nyokong, Tebello, Liang, Xu, Xu, Haijun
- Authors: Fu, Bo , Wang, Lin , Yu, Xiaoxiao , Fang, Xianying , Mack, John , Dingiswayo, Somila , Nyokong, Tebello , Liang, Xu , Xu, Haijun
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185294 , vital:44362 , xlink:href="https://doi.org/10.1016/j.dyepig.2021.109699"
- Description: A series of four multifunctional A2B type H3corroles with meso-borneol substituents at the B position have been synthesized and characterized. A detailed analysis of the optical properties was carried out, and a comparison was made with theoretical calculations to identify the key trends in the structure-property relationships. The meso-borneol substituent couples with the corrole core leading to clear CD signals in the B band region. Enhanced anti-cancer properties are observed in vitro relative to (−)-borneol with cell inhibition rates of up to 94%.
- Full Text:
- Date Issued: 2021
- Authors: Fu, Bo , Wang, Lin , Yu, Xiaoxiao , Fang, Xianying , Mack, John , Dingiswayo, Somila , Nyokong, Tebello , Liang, Xu , Xu, Haijun
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/185294 , vital:44362 , xlink:href="https://doi.org/10.1016/j.dyepig.2021.109699"
- Description: A series of four multifunctional A2B type H3corroles with meso-borneol substituents at the B position have been synthesized and characterized. A detailed analysis of the optical properties was carried out, and a comparison was made with theoretical calculations to identify the key trends in the structure-property relationships. The meso-borneol substituent couples with the corrole core leading to clear CD signals in the B band region. Enhanced anti-cancer properties are observed in vitro relative to (−)-borneol with cell inhibition rates of up to 94%.
- Full Text:
- Date Issued: 2021
Developing a citizen technician based approach to suspended sediment monitoring in the Tsitsa River catchment, Eastern Cape, South Africa
- Authors: Bannatyne, Laura Joan
- Date: 2018
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Suspended sediments -- South Africa -- Eastern Cape , Suspended sediments -- Monitoring -- Citizen participation , Tsitsa River
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62593 , vital:28211
- Description: Suspended sediment (SS) in channels is spatiotemporally heterogeneous and, over the long term, is known to be moved predominantly by flood flows with return periods of ~1 - 1.5 years. Flood flows in the Tsitsa catchment (Eastern Cape Province, South Africa) are unpredictable, and display a wide range of discharges. Direct, flood-focused SS sampling at sub-catchment scale was required to provide a SS baseline against which to monitor the impact on SS of catchment rehabilitation interventions, to determine the relative contributions of sub-catchments to SS loads and yields at the site of the proposed Ntabelanga Dam wall, and to verify modelled SS baselines, loads and yields. Approaches to SS sampling relying on researcher presence and/or installed equipment to adequately monitor SS through flood flows were precluded by cost, and the physical and socioeconomic conditions in the project area. A citizen technician (CT)-based flood-focused approach to direct SS sampling was developed and implemented. It was assessed in terms of its efficiency and effectiveness, the proficiency of the laboratory analysis methods, and the accuracy of the resulting SS data. A basic laboratory protocol for SSC analysis was developed, but is not the focus of this thesis. Using basic sampling equipment and smartphone-based reporting protocols, local residents at eleven points on the Tsitsa River and its major tributaries were employed as CTs. They were paid to take water samples during daylight hours at sub-daily timestep, with the emphasis on sampling through flood flows. The method was innovative in that it opted for manual sampling against a global trend towards instrumentation. Whilst the management of CTs formed a significant project component, the CTs benefitted directly through remuneration and work experience opportunities. The sampling method was evaluated at four sites from December 2015 - May 2016. The CTs were found to have efficiently and effectively sampled SS through a range of water levels, particularly in the main Tsitsa channel. An acceptable level of proficiency and accuracy was achieved, and many flood events were successfully defined by multiple data points. The method was chiefly limited by the inability of CTs to sample overnight rises and peaks occurring as a result of afternoon thunderstorms, particularly in small tributaries. The laboratory process was responsible for some losses in proficiency and accuracy. Improved laboratory quality control was therefore recommended. The CT-based approach can be adapted to other spatial and temporal scales in other areas, and to other environmental monitoring applications.
- Full Text:
- Date Issued: 2018
- Authors: Bannatyne, Laura Joan
- Date: 2018
- Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Suspended sediments -- South Africa -- Eastern Cape , Suspended sediments -- Monitoring -- Citizen participation , Tsitsa River
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62593 , vital:28211
- Description: Suspended sediment (SS) in channels is spatiotemporally heterogeneous and, over the long term, is known to be moved predominantly by flood flows with return periods of ~1 - 1.5 years. Flood flows in the Tsitsa catchment (Eastern Cape Province, South Africa) are unpredictable, and display a wide range of discharges. Direct, flood-focused SS sampling at sub-catchment scale was required to provide a SS baseline against which to monitor the impact on SS of catchment rehabilitation interventions, to determine the relative contributions of sub-catchments to SS loads and yields at the site of the proposed Ntabelanga Dam wall, and to verify modelled SS baselines, loads and yields. Approaches to SS sampling relying on researcher presence and/or installed equipment to adequately monitor SS through flood flows were precluded by cost, and the physical and socioeconomic conditions in the project area. A citizen technician (CT)-based flood-focused approach to direct SS sampling was developed and implemented. It was assessed in terms of its efficiency and effectiveness, the proficiency of the laboratory analysis methods, and the accuracy of the resulting SS data. A basic laboratory protocol for SSC analysis was developed, but is not the focus of this thesis. Using basic sampling equipment and smartphone-based reporting protocols, local residents at eleven points on the Tsitsa River and its major tributaries were employed as CTs. They were paid to take water samples during daylight hours at sub-daily timestep, with the emphasis on sampling through flood flows. The method was innovative in that it opted for manual sampling against a global trend towards instrumentation. Whilst the management of CTs formed a significant project component, the CTs benefitted directly through remuneration and work experience opportunities. The sampling method was evaluated at four sites from December 2015 - May 2016. The CTs were found to have efficiently and effectively sampled SS through a range of water levels, particularly in the main Tsitsa channel. An acceptable level of proficiency and accuracy was achieved, and many flood events were successfully defined by multiple data points. The method was chiefly limited by the inability of CTs to sample overnight rises and peaks occurring as a result of afternoon thunderstorms, particularly in small tributaries. The laboratory process was responsible for some losses in proficiency and accuracy. Improved laboratory quality control was therefore recommended. The CT-based approach can be adapted to other spatial and temporal scales in other areas, and to other environmental monitoring applications.
- Full Text:
- Date Issued: 2018
Modelling and intelligent control of vehicle climatronic systems
- Sun, Jie
- Authors: Sun, Jie
- Date: 2009
- Subjects: Automobiles -- Air conditioning , Automobiles -- Motors -- Cooling systems , Automobiles -- Heating and ventilation
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9600 , http://hdl.handle.net/10948/1118 , Automobiles -- Air conditioning , Automobiles -- Motors -- Cooling systems , Automobiles -- Heating and ventilation
- Description: The modelling and control method of a vehicle climatronic system, based on MATLAB/SIMULINK, is presented. In order to achieve high modelling accuracy, a developed simulation model library is introduced. The modelling approach is described and the developed models are validated with some of experimental data obtained. The models are nonlinear, independent of fluid type and based on thermo-dynamic principles. Analysis of the cooling circuit modelling and empirical real-time control models are created by using Fuzzy logic controller and Stateflow. Both of control input and output are implemented essentially at original vehicle CAN-Bus system. Feasible digital automatic control strategy basic to fuzzy theory, hardware and software solution are given. The simulation experiment is achieved with the Hardware-in-Loop technology. This control methodology is easily operated and worth applying for any further studies or methods.
- Full Text:
- Date Issued: 2009
- Authors: Sun, Jie
- Date: 2009
- Subjects: Automobiles -- Air conditioning , Automobiles -- Motors -- Cooling systems , Automobiles -- Heating and ventilation
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9600 , http://hdl.handle.net/10948/1118 , Automobiles -- Air conditioning , Automobiles -- Motors -- Cooling systems , Automobiles -- Heating and ventilation
- Description: The modelling and control method of a vehicle climatronic system, based on MATLAB/SIMULINK, is presented. In order to achieve high modelling accuracy, a developed simulation model library is introduced. The modelling approach is described and the developed models are validated with some of experimental data obtained. The models are nonlinear, independent of fluid type and based on thermo-dynamic principles. Analysis of the cooling circuit modelling and empirical real-time control models are created by using Fuzzy logic controller and Stateflow. Both of control input and output are implemented essentially at original vehicle CAN-Bus system. Feasible digital automatic control strategy basic to fuzzy theory, hardware and software solution are given. The simulation experiment is achieved with the Hardware-in-Loop technology. This control methodology is easily operated and worth applying for any further studies or methods.
- Full Text:
- Date Issued: 2009
Perceptions of social media as a tool for research: a study of postgraduate students, University of Fort Hare, Alice campus
- Authors: Abolanle, Ogunnubi Adeyemi
- Date: 2014-10
- Subjects: University of Fort Hare , Media literacy , Internet research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/26381 , vital:65299
- Description: The study aimed at examining the perceptions of social media as a tool for research among postgraduate students at the University of Fort Hare, Alice campus. Data were collected using a quantitative research approach by administering structured questionnaires to 310 postgraduate students under the cluster sampling across different faculties and departments, and analysed by SPSS Statistical software and Chi-square test. 264 questionnaires were returned for analysis and these respondents maintained that they utilized social media platforms for their academic research. The findings further revealed that social media has to a large extent improved students‟ research activities as they frequently seek practical knowledge for demonstration and tutorship. Furthermore, the respondents regard social media as a good platform for research topics in audio and video formats, scholarly articles, journals and books. This study concluded that since students explore the social media platforms and search engines for various reasons, academic research inclusive, it therefore becomes imperative to create more links within the social media for students to explore books, scholarly journals and articles necessary for research and academic purposes. , Thesis (MSoc) -- Faculty of Social Sciences and Humanities, 2014
- Full Text:
- Date Issued: 2014-10
- Authors: Abolanle, Ogunnubi Adeyemi
- Date: 2014-10
- Subjects: University of Fort Hare , Media literacy , Internet research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/26381 , vital:65299
- Description: The study aimed at examining the perceptions of social media as a tool for research among postgraduate students at the University of Fort Hare, Alice campus. Data were collected using a quantitative research approach by administering structured questionnaires to 310 postgraduate students under the cluster sampling across different faculties and departments, and analysed by SPSS Statistical software and Chi-square test. 264 questionnaires were returned for analysis and these respondents maintained that they utilized social media platforms for their academic research. The findings further revealed that social media has to a large extent improved students‟ research activities as they frequently seek practical knowledge for demonstration and tutorship. Furthermore, the respondents regard social media as a good platform for research topics in audio and video formats, scholarly articles, journals and books. This study concluded that since students explore the social media platforms and search engines for various reasons, academic research inclusive, it therefore becomes imperative to create more links within the social media for students to explore books, scholarly journals and articles necessary for research and academic purposes. , Thesis (MSoc) -- Faculty of Social Sciences and Humanities, 2014
- Full Text:
- Date Issued: 2014-10
The intention of third party logistics service providers to adopt environmentally sustainable practices
- Authors: Jappie, Abdul-Gasiep
- Date: 2018
- Subjects: Business logistics -- South Africa , Physical distribution of goods -- South Africa -- Management Industrial procurement -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/30605 , vital:30975
- Description: With the increase in global trade, an escalation of industry competition, greater customer expectations and increasingly larger and more complex supply chains, third-party logistics (3PL) providers play an increasingly important role in international trade. Driven by globalisation and the advances in information technology, 3PL services have experienced unprecedented growth around the world. Given its prominence in global trade, 3PL service providers have, since the late 1980’s, attracted increased scholarly attention and as such, many practitioners regard 3PL providers as integral to external parties that may be consulted for any and all matters related to logistics service, and that are often engaged in the strategic coordination of businesses supply chain activities. Although the body of literature concerned with environmental issues in disciplines such as production and marketing have grown, similar literature involving logistics has been scarce, but expanding. Notwithstanding this growing literature, more research on environmental issues within the logistics industry is required, since the logistics service industry may have a greater negative environmental impact than other service sectors. Despite extensive scientific literature on the outsourcing of logistics functions and 3PL strategy, comparatively fewer studies on environmental sustainability exist in the 3PL industry. It is against this background that the main research question to be addressed in this study is which factors influence the intentions of 3PL service providers to adopt environmentally sustainable practices. A quantitative research methodology was adopted in this study to empirically test the proposed hypothetical model. By means of non-probability sampling, namely convenience sampling, a total of 122 3PL service providers were targeted within Nelson Mandela Bay during the empirical study. This was done by means of a survey using a self-administered structured questionnaire. Descriptive statistics and frequency distributions were utilised to summarise the data collected from the sample. To test the hypothesised relationships in the theoretical model, multiple regression analyses were used. The influence of three internal factors (management support, organisational culture and availability of resources) three external factors (competitive pressure, customer pressure and government influences) on the intention of 3PL service providers to adopt environmentally sustainable practices xii were assessed. The findings of this analysis showed that management and organisational support, customer pressures and government influences and have a significant influence on the intention to adopt environmentally sustainable practices for these businesses. The findings of this study have contributed to the body of knowledge regarding the intentions of 3PL service providers to adopt environmentally sustainable practices. The study used a sound and well-developed research design and methodology which have been justified and applied. This can be utilised by other similar studies to conduct empirical research in the field of adopting sustainable business practices. The measuring instrument and hypothetical model developed can also be used by organisations in other industries to investigate intentions to adopt sustainable practices. This study also provided useful and very practical guidelines to 3PL service providers as to ensure effective adoption of sustainable business practices.
- Full Text:
- Date Issued: 2018
- Authors: Jappie, Abdul-Gasiep
- Date: 2018
- Subjects: Business logistics -- South Africa , Physical distribution of goods -- South Africa -- Management Industrial procurement -- Environmental aspects
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/30605 , vital:30975
- Description: With the increase in global trade, an escalation of industry competition, greater customer expectations and increasingly larger and more complex supply chains, third-party logistics (3PL) providers play an increasingly important role in international trade. Driven by globalisation and the advances in information technology, 3PL services have experienced unprecedented growth around the world. Given its prominence in global trade, 3PL service providers have, since the late 1980’s, attracted increased scholarly attention and as such, many practitioners regard 3PL providers as integral to external parties that may be consulted for any and all matters related to logistics service, and that are often engaged in the strategic coordination of businesses supply chain activities. Although the body of literature concerned with environmental issues in disciplines such as production and marketing have grown, similar literature involving logistics has been scarce, but expanding. Notwithstanding this growing literature, more research on environmental issues within the logistics industry is required, since the logistics service industry may have a greater negative environmental impact than other service sectors. Despite extensive scientific literature on the outsourcing of logistics functions and 3PL strategy, comparatively fewer studies on environmental sustainability exist in the 3PL industry. It is against this background that the main research question to be addressed in this study is which factors influence the intentions of 3PL service providers to adopt environmentally sustainable practices. A quantitative research methodology was adopted in this study to empirically test the proposed hypothetical model. By means of non-probability sampling, namely convenience sampling, a total of 122 3PL service providers were targeted within Nelson Mandela Bay during the empirical study. This was done by means of a survey using a self-administered structured questionnaire. Descriptive statistics and frequency distributions were utilised to summarise the data collected from the sample. To test the hypothesised relationships in the theoretical model, multiple regression analyses were used. The influence of three internal factors (management support, organisational culture and availability of resources) three external factors (competitive pressure, customer pressure and government influences) on the intention of 3PL service providers to adopt environmentally sustainable practices xii were assessed. The findings of this analysis showed that management and organisational support, customer pressures and government influences and have a significant influence on the intention to adopt environmentally sustainable practices for these businesses. The findings of this study have contributed to the body of knowledge regarding the intentions of 3PL service providers to adopt environmentally sustainable practices. The study used a sound and well-developed research design and methodology which have been justified and applied. This can be utilised by other similar studies to conduct empirical research in the field of adopting sustainable business practices. The measuring instrument and hypothetical model developed can also be used by organisations in other industries to investigate intentions to adopt sustainable practices. This study also provided useful and very practical guidelines to 3PL service providers as to ensure effective adoption of sustainable business practices.
- Full Text:
- Date Issued: 2018
Regional Financial Integration and Financial Sector Development in the Southern African Development Community
- Authors: Ntlemeza, Lwando
- Date: 2019
- Subjects: Integrating national economies
- Language: English
- Type: Thesis , Masters , MCom (Economics)
- Identifier: http://hdl.handle.net/10353/13870 , vital:39720
- Description: Regional financial integration (RFI) is perceived as the other avenue through which the financial sector of member countries can develop given the vast benefits which associated with it. These benefits include mobilization and allocation of efficient resources to productive sectors within the region which plays a very important role in the development process. Given this background, the study examines how regional financial integration promotes financial sector development in the SADC region utilizing the panel data model for the period 1996 to 2015. The empirical results revealed that regional financial integration does have an impact on the financial sector development in the member countries in the region. Furthermore, the results showed that regional financial integration require a certain degree of institutional quality for RFI benefits to accrue. The empirical results imply that the countries in the SADC region should pursue regional financial integration. This can be achieved through commitment by all authorities in the region. There should be a firm commitment to broader economic integration and building on existing networks and build the necessary infrastructure.
- Full Text:
- Date Issued: 2019
- Authors: Ntlemeza, Lwando
- Date: 2019
- Subjects: Integrating national economies
- Language: English
- Type: Thesis , Masters , MCom (Economics)
- Identifier: http://hdl.handle.net/10353/13870 , vital:39720
- Description: Regional financial integration (RFI) is perceived as the other avenue through which the financial sector of member countries can develop given the vast benefits which associated with it. These benefits include mobilization and allocation of efficient resources to productive sectors within the region which plays a very important role in the development process. Given this background, the study examines how regional financial integration promotes financial sector development in the SADC region utilizing the panel data model for the period 1996 to 2015. The empirical results revealed that regional financial integration does have an impact on the financial sector development in the member countries in the region. Furthermore, the results showed that regional financial integration require a certain degree of institutional quality for RFI benefits to accrue. The empirical results imply that the countries in the SADC region should pursue regional financial integration. This can be achieved through commitment by all authorities in the region. There should be a firm commitment to broader economic integration and building on existing networks and build the necessary infrastructure.
- Full Text:
- Date Issued: 2019
Determination of erythromycin in serum and urine by high performance liquid chromatography with ultraviolet detection
- Stubbs, Christopher, Haigh, John M, Kanfer, Isadore
- Authors: Stubbs, Christopher , Haigh, John M , Kanfer, Isadore
- Date: 1985
- Language: English
- Type: text , Article
- Identifier: vital:6428 , http://hdl.handle.net/10962/d1006576
- Description: A high-performance liquid chromatographic analysis of erythromycin in human serum and urine with UV detection at 200 nm is presented. The method involves a solid-phase extraction procedure followed by a simple phase separation step and chromatography on a reversed-phase column. The method has sensitivity limits of 0.25 and 1.0 g/mL in serum and urine, respectively, and is sufficiently sensitive to monitor concentrations of erythromycin in human serum and urine after the administration of a single 500-mg erythromycin stearate tablet.
- Full Text:
- Date Issued: 1985
- Authors: Stubbs, Christopher , Haigh, John M , Kanfer, Isadore
- Date: 1985
- Language: English
- Type: text , Article
- Identifier: vital:6428 , http://hdl.handle.net/10962/d1006576
- Description: A high-performance liquid chromatographic analysis of erythromycin in human serum and urine with UV detection at 200 nm is presented. The method involves a solid-phase extraction procedure followed by a simple phase separation step and chromatography on a reversed-phase column. The method has sensitivity limits of 0.25 and 1.0 g/mL in serum and urine, respectively, and is sufficiently sensitive to monitor concentrations of erythromycin in human serum and urine after the administration of a single 500-mg erythromycin stearate tablet.
- Full Text:
- Date Issued: 1985
What literature? : inaugural lecture delivered at Rhodes University
- Authors: Van Wyk Smith, Malvern
- Date: 1981
- Language: English
- Type: Text
- Identifier: vital:676 , http://hdl.handle.net/10962/d1020745 , ISBN 0868100692
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1981
- Authors: Van Wyk Smith, Malvern
- Date: 1981
- Language: English
- Type: Text
- Identifier: vital:676 , http://hdl.handle.net/10962/d1020745 , ISBN 0868100692
- Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 1981
Revising the distribution of mangrove forests in South Africa and changes in growth of mangrove species along a latitudinal gradient
- Authors: Bolosha, Uviwe
- Date: 2017
- Subjects: Mangrove ecology -- South Africa , Mangrove forests -- South Africa , Mangrove plants -- South Africa -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7544 , vital:21271
- Description: Mangrove forests are a diverse assemblage of trees and shrubs that are adapted to a saline and tidally inundated environment. The global spread of mangrove species is affected by climate, with most confined to areas that are warmer and moist. At a global scale, temperature limits the distribution of mangrove forests but on a regional scale and local scale, rainfall, river flow and tidal exchange have a strong effect on the distribution and biomass of mangrove forests. Other factors that play a role in limiting growth and distribution of mangroves include accessibility of suitable habitats for growth and also conditions that are suitable for propagule dispersal. The objectives of this study were to review the distribution of mangroves in South Africa and determine the number of extreme temperature events that may limit further distribution and secondly to measure growth rates of mangrove species at Mngazana and Nahoon Estuary and the nutrient pools in the sediment of these forests. In 1982, Ward and Steinke published a list of estuaries where mangroves were present. The current study sampled the population structure, microclimate and level of expansion in two estuaries within and outside of the published range. The minimum, maximum temperature and number of extreme temperature events were measured using iButtons. Mangrove expansion will be limited by minimum temperatures (1.1 ° C) and an increase in extreme temperature events (830) (<5 ° C and 5- 10 ° C) at the latitudinal limits. Expansion of A. marina at Kwelera and Tyolomnqa Estuary was evident but sapling survival was low. Mangroves have expanded within and outside the range proposed by Ward and Steinke (1982), but are limited by physical factors, restricted by the presence of saltmarsh and other estuarine macrophytes and natural disturbance regimes. An increase in population growth was recorded over the years at both Mngazana and Nahoon Estuary. Nutrients, (ammonium, nitrates + nitrites and soluble reactive phosphorus) varied amongst sites and were related to seasonality. Nitrogen in both estuaries was available in the form of ammonium (NH4) and its concentration was generally higher (1.3-76.2 pm) than other forms of nitrogen (0.07-6.3 µm). Soluble reactive phosphorus (SRP) was higher during the wet seasons in both estuaries. An increase in porewater salinity since 2007 (41.3 practical salinity unit (PSU)) was measured at Mngazana and this is a result of freshwater abstraction and low rainfall. A. marina saplings and adults grew significantly faster at Nahoon Estuary (the distributional limit) (11.1 ± 1.1 cm year-¹) compared to Mngazana Estuary (5.3 ± 1.8 cm year-¹). Different mangrove species and forests respond differently to environmental factors and changes in mangrove distribution is expected in South Africa but changes are expected to happen slowly and opportunistically.
- Full Text:
- Date Issued: 2017
- Authors: Bolosha, Uviwe
- Date: 2017
- Subjects: Mangrove ecology -- South Africa , Mangrove forests -- South Africa , Mangrove plants -- South Africa -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7544 , vital:21271
- Description: Mangrove forests are a diverse assemblage of trees and shrubs that are adapted to a saline and tidally inundated environment. The global spread of mangrove species is affected by climate, with most confined to areas that are warmer and moist. At a global scale, temperature limits the distribution of mangrove forests but on a regional scale and local scale, rainfall, river flow and tidal exchange have a strong effect on the distribution and biomass of mangrove forests. Other factors that play a role in limiting growth and distribution of mangroves include accessibility of suitable habitats for growth and also conditions that are suitable for propagule dispersal. The objectives of this study were to review the distribution of mangroves in South Africa and determine the number of extreme temperature events that may limit further distribution and secondly to measure growth rates of mangrove species at Mngazana and Nahoon Estuary and the nutrient pools in the sediment of these forests. In 1982, Ward and Steinke published a list of estuaries where mangroves were present. The current study sampled the population structure, microclimate and level of expansion in two estuaries within and outside of the published range. The minimum, maximum temperature and number of extreme temperature events were measured using iButtons. Mangrove expansion will be limited by minimum temperatures (1.1 ° C) and an increase in extreme temperature events (830) (<5 ° C and 5- 10 ° C) at the latitudinal limits. Expansion of A. marina at Kwelera and Tyolomnqa Estuary was evident but sapling survival was low. Mangroves have expanded within and outside the range proposed by Ward and Steinke (1982), but are limited by physical factors, restricted by the presence of saltmarsh and other estuarine macrophytes and natural disturbance regimes. An increase in population growth was recorded over the years at both Mngazana and Nahoon Estuary. Nutrients, (ammonium, nitrates + nitrites and soluble reactive phosphorus) varied amongst sites and were related to seasonality. Nitrogen in both estuaries was available in the form of ammonium (NH4) and its concentration was generally higher (1.3-76.2 pm) than other forms of nitrogen (0.07-6.3 µm). Soluble reactive phosphorus (SRP) was higher during the wet seasons in both estuaries. An increase in porewater salinity since 2007 (41.3 practical salinity unit (PSU)) was measured at Mngazana and this is a result of freshwater abstraction and low rainfall. A. marina saplings and adults grew significantly faster at Nahoon Estuary (the distributional limit) (11.1 ± 1.1 cm year-¹) compared to Mngazana Estuary (5.3 ± 1.8 cm year-¹). Different mangrove species and forests respond differently to environmental factors and changes in mangrove distribution is expected in South Africa but changes are expected to happen slowly and opportunistically.
- Full Text:
- Date Issued: 2017
An analysis of technical efficiency and service effectiveness for freight railways in African and European countries
- Mfiyo, Azania https://orcid.org/0000-0002-0967-9756
- Authors: Mfiyo, Azania https://orcid.org/0000-0002-0967-9756
- Date: 2021-03
- Subjects: Freight and freightage , Railroads -- Freight
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20186 , vital:45406
- Description: For the past decades, technical efficiency and service effectiveness have become topical as performance measures in various sectors. However, a comparison of technical efficiency and service effectiveness for freight rail transport has received less attention in African and European countries. To address this challenge the current study seeks to analyse technical efficiency and service effectiveness of rail freight in African and European countries. Due to data unavailability in other countries, this study selected four African countries (South Africa, Morocco, Democratic Republic of Congo and Algeria) and four European countries (Lithuania, Austria, France and Germany). The data has been collected from the World Bank, International Union of Railway Statistics and Knoema for the period 2017. Input oriented and output oriented data envelope analysis (DEA) were used to analyze technical efficiency and service effectiveness, respectively. The application of DEA requires the selection of appropriate inputs, production and output variables. This study selected a number of employees and length of rail lines as input variables, gross train tonne kilometres (km) as production variable, tonnes carried and tonne kilometres (km) as output variables. The result shows that five out of eight countries were technical efficient and their services effective with values equal to 1.00. The Pearson correlation coefficient was used to analyse the relationship between technical efficiency and service effectiveness. The results indicate that there is a statistically significant positive correlation between technical efficiency and service effectiveness. To determine the impact exogenous variables on technical efficiency and service effectiveness, a Tobit regression analysis was conducted. The results show that technical efficiency and service effectiveness are not significantly affected by exogenous variables. On the other hand, technical efficiency is significantly affected by the number of employees while service effectiveness is significantly affected by gross train tonne km. This study recommends the use of less labour intensive assets and monitoring of gross train tonne km should be viewed as important strategies to improve technical efficiency and service effectiveness, respectively. , Thesis (MCom) -- Faculty of Management and Commerce, 2021
- Full Text:
- Date Issued: 2021-03
- Authors: Mfiyo, Azania https://orcid.org/0000-0002-0967-9756
- Date: 2021-03
- Subjects: Freight and freightage , Railroads -- Freight
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20186 , vital:45406
- Description: For the past decades, technical efficiency and service effectiveness have become topical as performance measures in various sectors. However, a comparison of technical efficiency and service effectiveness for freight rail transport has received less attention in African and European countries. To address this challenge the current study seeks to analyse technical efficiency and service effectiveness of rail freight in African and European countries. Due to data unavailability in other countries, this study selected four African countries (South Africa, Morocco, Democratic Republic of Congo and Algeria) and four European countries (Lithuania, Austria, France and Germany). The data has been collected from the World Bank, International Union of Railway Statistics and Knoema for the period 2017. Input oriented and output oriented data envelope analysis (DEA) were used to analyze technical efficiency and service effectiveness, respectively. The application of DEA requires the selection of appropriate inputs, production and output variables. This study selected a number of employees and length of rail lines as input variables, gross train tonne kilometres (km) as production variable, tonnes carried and tonne kilometres (km) as output variables. The result shows that five out of eight countries were technical efficient and their services effective with values equal to 1.00. The Pearson correlation coefficient was used to analyse the relationship between technical efficiency and service effectiveness. The results indicate that there is a statistically significant positive correlation between technical efficiency and service effectiveness. To determine the impact exogenous variables on technical efficiency and service effectiveness, a Tobit regression analysis was conducted. The results show that technical efficiency and service effectiveness are not significantly affected by exogenous variables. On the other hand, technical efficiency is significantly affected by the number of employees while service effectiveness is significantly affected by gross train tonne km. This study recommends the use of less labour intensive assets and monitoring of gross train tonne km should be viewed as important strategies to improve technical efficiency and service effectiveness, respectively. , Thesis (MCom) -- Faculty of Management and Commerce, 2021
- Full Text:
- Date Issued: 2021-03
Aggregation control of robust water-soluble zinc (II) phthalocyanine-based photosensitizers
- Ikeuchi, Takuro, Mack, John, Nyokong, Tebello, Kobayashi, Nagao, Kimura, Mutsumi
- Authors: Ikeuchi, Takuro , Mack, John , Nyokong, Tebello , Kobayashi, Nagao , Kimura, Mutsumi
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239709 , vital:50757 , xlink:href="https://doi.org/10.1021/acs.langmuir.6b03552"
- Description: A water-soluble zinc phthalocyanine (ZnPc) complex with four negatively charged electron-withdrawing sulfonic acid substituents at the nonperipheral positions (α-ZnTSPc) is found to have a high singlet oxygen (1O2) quantum yield and exhibits high photostability. The formation of aggregates is hindered and the highest occupied molecular orbital is significantly stabilized, making α-ZnTSPc potentially suitable for its use as a photosensitizer for photodynamic therapy and photoimmunotherapy. Atomic force microscopy (AFM) reveals that mixtures of the negatively charged α-ZnTSPc complex with a similar positively charged ZnPc were found to result in the self-assembly of one-dimensional accordion-like fibers. Supramolecular fibers can be formed in aqueous solutions through intermolecular electrostatic and donor–acceptor interactions between the two water-soluble ZnPcs.
- Full Text:
- Date Issued: 2016
- Authors: Ikeuchi, Takuro , Mack, John , Nyokong, Tebello , Kobayashi, Nagao , Kimura, Mutsumi
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239709 , vital:50757 , xlink:href="https://doi.org/10.1021/acs.langmuir.6b03552"
- Description: A water-soluble zinc phthalocyanine (ZnPc) complex with four negatively charged electron-withdrawing sulfonic acid substituents at the nonperipheral positions (α-ZnTSPc) is found to have a high singlet oxygen (1O2) quantum yield and exhibits high photostability. The formation of aggregates is hindered and the highest occupied molecular orbital is significantly stabilized, making α-ZnTSPc potentially suitable for its use as a photosensitizer for photodynamic therapy and photoimmunotherapy. Atomic force microscopy (AFM) reveals that mixtures of the negatively charged α-ZnTSPc complex with a similar positively charged ZnPc were found to result in the self-assembly of one-dimensional accordion-like fibers. Supramolecular fibers can be formed in aqueous solutions through intermolecular electrostatic and donor–acceptor interactions between the two water-soluble ZnPcs.
- Full Text:
- Date Issued: 2016
Enhanced Optical Limiting Behavior of an Indium Phthalocyanine–Single-Walled Carbon Nanotube Composite
- Sanusi, Kayode, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014
- Authors: Sanusi, Kayode , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193871 , vital:45401 , xlink:href="https://doi.org/10.1021/jp501469e "
- Description: The nonlinear optical behavior of 2(3),9(10),16(17),23(24)-tetrakis-(4-aminophenoxy) phthalocyaninato indium (III) chloride (2) and its carbon nanotube composite in dimethylsulfoxide (DMSO) and dimethylformamide (DMF) solutions is described. The nonlinear third-order susceptibility and second-order hyperpolarizability values are also reported. A large nonlinear absorption that increased on covalent linking with single-walled carbon nanotubes (SWCNTs) was observed for the compound in DMSO. The nanosecond nonlinear absorption and the optical limiting behavior of this complex are shown to be dominated by a strong excited state absorption from a two-photon pumped state. The optical limiter using the new nanocomposite material (SWCNT-2) in the appropriate solvent showed a much lower threshold for optical limiting together with a much lower transmission at high fluences than previously reported nanocomposite limiters. The optical properties of the phthalocyanine and its conjugate were found to show high sensitivity toward the change of solvent matrix.
- Full Text:
- Date Issued: 2014