An ergonomics intervention study into the physiological, perceptual and productivity effects of three citrus harvesting bag designs in the Eastern Cape of South Africa : a combined laboratory and field approach
- Bassey-Duke, Elizabeth Misan
- Authors: Bassey-Duke, Elizabeth Misan
- Date: 2015
- Subjects: Citrus -- Harvesting -- South Africa -- Eastern Cape , Lifting and carrying -- South Africa -- Eastern Cape , Manual work -- South Africa -- Eastern Cape , Blue collar workers -- South Africa -- Eastern Cape , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5176 , http://hdl.handle.net/10962/d1018908
- Description: Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. , Name on Graduation Programme: Bassey-Duke, Elizabeth Missan
- Full Text:
- Date Issued: 2015
- Authors: Bassey-Duke, Elizabeth Misan
- Date: 2015
- Subjects: Citrus -- Harvesting -- South Africa -- Eastern Cape , Lifting and carrying -- South Africa -- Eastern Cape , Manual work -- South Africa -- Eastern Cape , Blue collar workers -- South Africa -- Eastern Cape , Work -- Physiological aspects , Human mechanics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5176 , http://hdl.handle.net/10962/d1018908
- Description: Background: Agriculture plays a vital role in the economy of any industrially developing country, including South Africa. In the Eastern Cape of South Africa citrus farming is a significant contributor to the local economy (Johnson et al., 2005). The harvesting phase of citrus farming is performed manually and exposes workers to physical risks, which can lead to the development of musculoskeletal disorders. In particular, the standard harvesting bag comprises of a single shoulder strap and promotes asymmetrical load carriage which results in shoulder and lower back pain complaints. The current study compared the physiological (EMG), perceptual (RPE), usability (PUEU) and productivity effects of two new harvesting bag designs (a hip belt and a backpack bag design) to the standard harvesting bag design. This was performed in a laboratory as well as a field setting. Methods (Laboratory phase): 36 participants (12 males and 24 females) were assigned to one worker group. The “tall ladder worker” group was comprised of only males and the “step ladder worker” and “ground worker” group of females. Each participant was required to simulate a citrus harvesting task while utilizing each of the bag designs on different days. On each day/test session, participants performed three harvesting cycles. Muscle activity was measured throughout the entire testing session and RPE were recorded at the end of each cycle. Results (Laboratory phase): The EMG and RPE results indicate that the backpack design was the most ideal design to reduce asymmetry, while the standard harvesting bag design was the worst. Although not significant, there was greater muscle asymmetry (p=0.109) and a significantly higher perceived exertion when using the standard bag (p=0.0004), in comparison to using the backpack. Methods (Field phase): 17 Xhosa-speaking citrus harvesters (6 females and 11 males) participated in this study. Each harvester worked with one of the three bag designs on a different day. Productivity of each worker was assessed every hour by recording the number of bags filled with fruit and at the end of the shift. A Perceived Usefulness & Ease of Use questionnaire was presented to each participant to obtain feedback on worker acceptance to the new bag designs. Results (Field phase): A general trend in support of the hip belt bag design over the other two bag designs were found, even within the different worker demographic groups (age, sex and worker experience). The workers perceived less exertion (7.98 ± 1.86) and were more productive (9.90 ± 2.11 bags/hour) when using the hip belt design; they also found this bag the most useful (1.02 ± 0.09) and easy to use (1.07 ± 0.25). In contrast, the backpack bag design had significantly poorer responses when compared to the other two bag designs and this was evident in all the dependent variables assessed (RPE, productivity and PUEU). Conclusion: The results from the laboratory phase supported the expectation that the backpack bag design reduces asymmetry and hence, is more suitable than the standard harvesting bag. However, results from the field show that the hip belt bag design was the most preferred and the backpack was the least preferred. Bao & Shahnavaz (1989) highlight the need for ergonomics researcher to convey laboratory findings into the field context. However, as shown by the current study, there are numerous challenges associated with field work, making it difficult for laboratory findings to be successfully conveyed to the field. Limitations and Recommendations: For the laboratory phase of the project, no biomechanical and cardiovascular responses were assessed. However, for a holistic approach, these variables should be considered in future studies. Due to high variability from one harvesting cycle to another, more than three harvesting cycles should also be performed to accurately replicate the harvesting process as done in the field over extended durations of time. For the field phase, data should be collected from more than one citrus farm and thus a larger sample size could be obtained. This would improve the validity of the study. In addition to this, data should be collected for a full working day, especially if environmental conditions are not a hindrance, as well as for a whole season, since workloads vary, depending on the time of the harvesting season. , Name on Graduation Programme: Bassey-Duke, Elizabeth Missan
- Full Text:
- Date Issued: 2015
Forage production, nutritive value and intake rates by goats of pigeon pea (Cajanus cajan (L.) forages grown in the subtropical region of South Africa
- Authors: Buthelezi, Lindokuhle Sizwe
- Date: 2017
- Subjects: Forage Pigeon pea Forage plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/7852 , vital:30773
- Description: Different growth stages and drying methods were used to assess forage production, nutritive value and intake of leaves from three Cajanus cajan varieties (ICEAP 00557, ICEAP 01514 and CIMMYT 100/01). In the 2016/17 growing season, three complete randomized block designs (CRBD’s) were conducted. Regrowth parameters were measured during both the both vegetative and flowering stages. The plots were harvested at the flowering stage. Biomass yields were measured at the flowering stage. The harvested leaves were then dried under the two different drying methods. The methods used were shade- and oven-drying at 60 oC. This was used to determine dry matter (DM), crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and total non-structural carbohydrates (TNC) for the C. cajan varieties. Minerals Ca, Mg, K, Na, K/(Ca+Mg), P and Zn, Cu, Mn and Fe and phytochemicals condensed tannins, phenolic compounds and saponins were also analyzed. The intake rates and in vitro and in sacco ruminal degradabilities were also determined. The survival percentage was significantly different (P<0.05) only across the means of varieties. There was no significant difference (P>0.05) in the number of shoots per plant, stems per shoot and coppice stems produced by the three C. cajan varieties at vegetative and flowering stage. There was a significant difference (P<0.05) in the heights of plants recorded by the varieties only at flowering stage. The yields of fresh biomass in C. cajan was significantly different (P<0.05) across all the varieties harvested in 2016. In all the varieties there was a significant difference (P<0.05) in dry matter yield in both seasons of 2016 and 2017. The effect of browse varieties and drying methods showed a significant effect (P<0.05) on DM, CP, fat, NDIN, ADIN and hemicellulose content of varieties. There was little impact by varieties and drying methods (P<0.05) on ash, NDF, ADF, ADL, TNC and cellulose content of varieties. Varieties and drying method had no effect (P>0.05) on Ca, Mg and K except for Na and P. There was no effect caused by varieties and drying methods (P>0.05) on Zn and Mn with Cu and Fe being the exceptions. Oven drying showed an overall reduction in the tannin concentration on leaves while there was an increase in saponins. The different varieties had no effect (P>0.05) on the IIR, 0.0275±0.0089, 0.0275±0.0077 and 0.0409±0.0109 for Cv1, Cv2 and Cv3, respectively. The day of the trial and browse variety had an effect (P<0.05) on bite rate. However, the day of trial had no significant effect (P>0.05) on both bite size and the instantaneous intake rate. Individual goat had a significant effect (P<0.05) on bite rate. There was a significant difference (P<0.05) in the in vitro and in sacco rapidly degradable fractions (a) of all the three varieties but the drying method had no effect (P>0.05). The slowly degradable fraction (b) and degradation rate constant (c) of all varieties was not significantly different (P>0.05) on both drying methods during IV DaisyII procedure. However, b and c, in all the varieties was significantly different (P<0.05) in both drying methods during the in sacco procedure. There was no significant difference (P>0.05) in the mean potentially degradable fraction (a+b) across all C. cajan varieties during IV DaisyII procedure, however a+c of all varieties was significantly different (P<0.05) in both the drying methods during the in sacco procedure. The effective in vitro and in sacco degradability of the varieties was significantly different (P<0.05) with a rumen outflow rate of 2, 5 and 8 percent per hour. The shade-dried varieties had a higher (P<0.05) ED than the oven-dried materials during IV DaisyII and the in sacco procedures. It was concluded that the decline in yield of C. cajan during the study is a reflection of poor survival, the insufficient regeneration from seed, nutrient depletion over time and the extended dry seasons. Therefore, shade drying is commended method of drying forages.
- Full Text:
- Date Issued: 2017
- Authors: Buthelezi, Lindokuhle Sizwe
- Date: 2017
- Subjects: Forage Pigeon pea Forage plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/7852 , vital:30773
- Description: Different growth stages and drying methods were used to assess forage production, nutritive value and intake of leaves from three Cajanus cajan varieties (ICEAP 00557, ICEAP 01514 and CIMMYT 100/01). In the 2016/17 growing season, three complete randomized block designs (CRBD’s) were conducted. Regrowth parameters were measured during both the both vegetative and flowering stages. The plots were harvested at the flowering stage. Biomass yields were measured at the flowering stage. The harvested leaves were then dried under the two different drying methods. The methods used were shade- and oven-drying at 60 oC. This was used to determine dry matter (DM), crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) and total non-structural carbohydrates (TNC) for the C. cajan varieties. Minerals Ca, Mg, K, Na, K/(Ca+Mg), P and Zn, Cu, Mn and Fe and phytochemicals condensed tannins, phenolic compounds and saponins were also analyzed. The intake rates and in vitro and in sacco ruminal degradabilities were also determined. The survival percentage was significantly different (P<0.05) only across the means of varieties. There was no significant difference (P>0.05) in the number of shoots per plant, stems per shoot and coppice stems produced by the three C. cajan varieties at vegetative and flowering stage. There was a significant difference (P<0.05) in the heights of plants recorded by the varieties only at flowering stage. The yields of fresh biomass in C. cajan was significantly different (P<0.05) across all the varieties harvested in 2016. In all the varieties there was a significant difference (P<0.05) in dry matter yield in both seasons of 2016 and 2017. The effect of browse varieties and drying methods showed a significant effect (P<0.05) on DM, CP, fat, NDIN, ADIN and hemicellulose content of varieties. There was little impact by varieties and drying methods (P<0.05) on ash, NDF, ADF, ADL, TNC and cellulose content of varieties. Varieties and drying method had no effect (P>0.05) on Ca, Mg and K except for Na and P. There was no effect caused by varieties and drying methods (P>0.05) on Zn and Mn with Cu and Fe being the exceptions. Oven drying showed an overall reduction in the tannin concentration on leaves while there was an increase in saponins. The different varieties had no effect (P>0.05) on the IIR, 0.0275±0.0089, 0.0275±0.0077 and 0.0409±0.0109 for Cv1, Cv2 and Cv3, respectively. The day of the trial and browse variety had an effect (P<0.05) on bite rate. However, the day of trial had no significant effect (P>0.05) on both bite size and the instantaneous intake rate. Individual goat had a significant effect (P<0.05) on bite rate. There was a significant difference (P<0.05) in the in vitro and in sacco rapidly degradable fractions (a) of all the three varieties but the drying method had no effect (P>0.05). The slowly degradable fraction (b) and degradation rate constant (c) of all varieties was not significantly different (P>0.05) on both drying methods during IV DaisyII procedure. However, b and c, in all the varieties was significantly different (P<0.05) in both drying methods during the in sacco procedure. There was no significant difference (P>0.05) in the mean potentially degradable fraction (a+b) across all C. cajan varieties during IV DaisyII procedure, however a+c of all varieties was significantly different (P<0.05) in both the drying methods during the in sacco procedure. The effective in vitro and in sacco degradability of the varieties was significantly different (P<0.05) with a rumen outflow rate of 2, 5 and 8 percent per hour. The shade-dried varieties had a higher (P<0.05) ED than the oven-dried materials during IV DaisyII and the in sacco procedures. It was concluded that the decline in yield of C. cajan during the study is a reflection of poor survival, the insufficient regeneration from seed, nutrient depletion over time and the extended dry seasons. Therefore, shade drying is commended method of drying forages.
- Full Text:
- Date Issued: 2017
Anorogenic alkaline ring-type complexes of the Damaraland Province, Namibia, and their economic potential
- Authors: Potgieter, J E
- Date: 1987
- Subjects: Alkalic igneous rocks -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4907 , http://hdl.handle.net/10962/d1001567
- Description: Anorogenic alkaline ring-type complexes form within continental plate settings. Alkaline magmatism is derived from the upper mantle, in which mantle metasomatism plays an important part, as well as from partial melting of the lower crust. Radial and concentric fractures develop during the ascent of alkaline magma. Extrusion of basic and felsic magma takes place along these fractures with felsic volcanics building-up central volcanoes. As a result of emptying of the magma chamber, the superstructure of the volcano collapses and a caldera is formed. During the caldera stage syenitic and granitic material are intruded into ring fractures. Alkaline ring-type complexes may be classified as (i) alkaline qranite and syenite-type and (ii) carbonatite and undersaturated-type. These ring-type complexes occur as distinct igneous provinces. Some major provinces occur in Brazil, Corsica, Namibia, Nigeria, Norway, Saudi-Arabia and Sudan. In Namibia the Damaraland igneous province is of Mesozoic aqe and it contains 15 alkaline ring-type complexes . These complexes are situated along north-eastern trends which correspond to transform directions of the South Atlantic. During the opening of the South Atlantic (Gondwana breakup) Pan-African age lineaments were reactivated which allowed emplacement of anorogenic alkaline magmatism. A zonation of alkaline granite and syenitetype in the west and carbonatite and undersaturated-type ring-complexes in the east correlates with down- and upwarp axes parallel to the line of Gondwana fragmentation. Alkali- and H⁺-metasomatism is related to the alkaline and syenite-type whereas alkali metasomatism (fenitization) is associated with carbonatite and undersaturated-type ring-complexes. Sn, W and Ta mineralization is associated with alkaline granites of some of the alkaline granite and syenite-type ring-complexes. Fe, F, PO₄ , Nb, Th, REE, Sr, Zn and Pb mineralization is associated with carbonatite complexes. Potential exists for: (i) porphyry Cu-Mo and epithermal-type (Au, Ag, Pt-metals, base metals) mineralization in the alkaline granite and syenite-type ring-complexes and (ii) disseminated Cu, Au, Aq and Pt-metals in carbonatite and undersaturated-type ring-complexes
- Full Text:
- Date Issued: 1987
- Authors: Potgieter, J E
- Date: 1987
- Subjects: Alkalic igneous rocks -- Namibia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4907 , http://hdl.handle.net/10962/d1001567
- Description: Anorogenic alkaline ring-type complexes form within continental plate settings. Alkaline magmatism is derived from the upper mantle, in which mantle metasomatism plays an important part, as well as from partial melting of the lower crust. Radial and concentric fractures develop during the ascent of alkaline magma. Extrusion of basic and felsic magma takes place along these fractures with felsic volcanics building-up central volcanoes. As a result of emptying of the magma chamber, the superstructure of the volcano collapses and a caldera is formed. During the caldera stage syenitic and granitic material are intruded into ring fractures. Alkaline ring-type complexes may be classified as (i) alkaline qranite and syenite-type and (ii) carbonatite and undersaturated-type. These ring-type complexes occur as distinct igneous provinces. Some major provinces occur in Brazil, Corsica, Namibia, Nigeria, Norway, Saudi-Arabia and Sudan. In Namibia the Damaraland igneous province is of Mesozoic aqe and it contains 15 alkaline ring-type complexes . These complexes are situated along north-eastern trends which correspond to transform directions of the South Atlantic. During the opening of the South Atlantic (Gondwana breakup) Pan-African age lineaments were reactivated which allowed emplacement of anorogenic alkaline magmatism. A zonation of alkaline granite and syenitetype in the west and carbonatite and undersaturated-type ring-complexes in the east correlates with down- and upwarp axes parallel to the line of Gondwana fragmentation. Alkali- and H⁺-metasomatism is related to the alkaline and syenite-type whereas alkali metasomatism (fenitization) is associated with carbonatite and undersaturated-type ring-complexes. Sn, W and Ta mineralization is associated with alkaline granites of some of the alkaline granite and syenite-type ring-complexes. Fe, F, PO₄ , Nb, Th, REE, Sr, Zn and Pb mineralization is associated with carbonatite complexes. Potential exists for: (i) porphyry Cu-Mo and epithermal-type (Au, Ag, Pt-metals, base metals) mineralization in the alkaline granite and syenite-type ring-complexes and (ii) disseminated Cu, Au, Aq and Pt-metals in carbonatite and undersaturated-type ring-complexes
- Full Text:
- Date Issued: 1987
Studies on Paragus (Diptera, Syrphidae)
- Authors: Stuckenberg, B R
- Date: 1953
- Subjects: Syrphidae , Diptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5887 , http://hdl.handle.net/10962/d1013321
- Description: As several new species are described in this thesis its full value can only be realised by its publication, and it has therefore been prepared with that end in view. The subject matter is divided into two parts, each of which has been treated quite independently of the other. Both parts are presented here in the form in which they have been offered for publication. The first paper consists of a systematic study of a complex of species within the genus Paragus. It includes descriptions of four new species, a new subspecies, an allotype, and redescriptions of two incompletely defined species. This paper has been offered for publication in the Transactions of the Royal Entomological Society of London. The second part consists of a study of all the Ethiopian species of Paragus except those covered by the first paper. It includes the definition of a new subgenus, and descriptions of two new species and three allotypes. It has been sent for publication in the "Revue Zoologie et Botanique de Africaine" at the invitation of Dr. P. Basilewsky of the Musee du Congo Belge, Tervuren.
- Full Text:
- Date Issued: 1953
- Authors: Stuckenberg, B R
- Date: 1953
- Subjects: Syrphidae , Diptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5887 , http://hdl.handle.net/10962/d1013321
- Description: As several new species are described in this thesis its full value can only be realised by its publication, and it has therefore been prepared with that end in view. The subject matter is divided into two parts, each of which has been treated quite independently of the other. Both parts are presented here in the form in which they have been offered for publication. The first paper consists of a systematic study of a complex of species within the genus Paragus. It includes descriptions of four new species, a new subspecies, an allotype, and redescriptions of two incompletely defined species. This paper has been offered for publication in the Transactions of the Royal Entomological Society of London. The second part consists of a study of all the Ethiopian species of Paragus except those covered by the first paper. It includes the definition of a new subgenus, and descriptions of two new species and three allotypes. It has been sent for publication in the "Revue Zoologie et Botanique de Africaine" at the invitation of Dr. P. Basilewsky of the Musee du Congo Belge, Tervuren.
- Full Text:
- Date Issued: 1953
Electron precipitation and ionospheric disturbance
- Authors: Torr, Marsha R
- Date: 1966
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5509 , http://hdl.handle.net/10962/d1007691
- Description: From Introduction: The minimum in the scalar magnitude of the geographic total field, which lies off the coast of Brazil, allows the mirror points of trapped particles to dip low into the atmosphere over the South Atlantic Ocean, resulting in two regions of maximum intensity of preciptated particles in that region, one from the inner belt and one from the outer. High charged particle fluxes have been observed at low altitudes over these regions by satellites Sputnik 5 and 6 (Ginsburg et al, 1961) and Discoverer 31 (Seward and Kornblum, 1963) amongst others. The more southerly of these two regions acts as a sink for electrons from the outer radiation belt and will be referred to in what follows as the Southern Radiation Anomaly. Gladhill and van Rooyen (1963) predicted that the energy deposited in the upper atmosphere by these charged particles would be sufficient to give rise to enhanced geophysical effects such as auroral emission, X-rays and ionization and heating of the upper atmosphere in this region. Although some of these effects have been correlated with precipitated electrons, no definite relation had until now been established between ionospheric effects and precipitated particles. The aim of this thesis was to investigate such a relationship and the results were extremely successful. It will be shown conclusively in what follows, that the precipitation of electrons can account for the ionospheric disturbances defined by a disturbance criterion at all stations around L=4. Part I describes the exploration of the radiation belts and the magnetosphere with rockets and satellites. The resulting theoretical models based on the observations are discussed. A brief review is given of the work that has been done to date to derive equations for the loss and replenishment of particles in the belts. Because of the complexity of these and the number of doubtful factors involved, a simple model of injection of electrons into the outer belt is devised, giving average values of trapped and precipitated electron fluxes at any point around L=4. In Part II, this model is employed together with the disturbance criterion of Gledhill and Torr (1965) to examine the relationship between ionospheric disturbances and electron fluxes. Also the energy range of the precipitated particles is examined.
- Full Text:
- Date Issued: 1966
- Authors: Torr, Marsha R
- Date: 1966
- Subjects: Electrons , Electron precipitation , Ionosphere , Ionospheric electron density
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5509 , http://hdl.handle.net/10962/d1007691
- Description: From Introduction: The minimum in the scalar magnitude of the geographic total field, which lies off the coast of Brazil, allows the mirror points of trapped particles to dip low into the atmosphere over the South Atlantic Ocean, resulting in two regions of maximum intensity of preciptated particles in that region, one from the inner belt and one from the outer. High charged particle fluxes have been observed at low altitudes over these regions by satellites Sputnik 5 and 6 (Ginsburg et al, 1961) and Discoverer 31 (Seward and Kornblum, 1963) amongst others. The more southerly of these two regions acts as a sink for electrons from the outer radiation belt and will be referred to in what follows as the Southern Radiation Anomaly. Gladhill and van Rooyen (1963) predicted that the energy deposited in the upper atmosphere by these charged particles would be sufficient to give rise to enhanced geophysical effects such as auroral emission, X-rays and ionization and heating of the upper atmosphere in this region. Although some of these effects have been correlated with precipitated electrons, no definite relation had until now been established between ionospheric effects and precipitated particles. The aim of this thesis was to investigate such a relationship and the results were extremely successful. It will be shown conclusively in what follows, that the precipitation of electrons can account for the ionospheric disturbances defined by a disturbance criterion at all stations around L=4. Part I describes the exploration of the radiation belts and the magnetosphere with rockets and satellites. The resulting theoretical models based on the observations are discussed. A brief review is given of the work that has been done to date to derive equations for the loss and replenishment of particles in the belts. Because of the complexity of these and the number of doubtful factors involved, a simple model of injection of electrons into the outer belt is devised, giving average values of trapped and precipitated electron fluxes at any point around L=4. In Part II, this model is employed together with the disturbance criterion of Gledhill and Torr (1965) to examine the relationship between ionospheric disturbances and electron fluxes. Also the energy range of the precipitated particles is examined.
- Full Text:
- Date Issued: 1966
Nutritional and pharmacological profile of moringa oleifera lam. Leaves cultivated in the South African ecotype
- Authors: Yako, Zomsa
- Date: 2019
- Subjects: Moringa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14605 , vital:40021
- Description: Moringa oleifera Lam. is native to the Indian ecotype, which has become naturalized in many tropic and subtropic regions worldwide, thus a great variation in the bioactive compounds of the plant is recorded. The introduction of Moringa oleifera to South Africa occurred in the turn of the twentieth century with the aim of combating malnourishment, aiding health and fostering economic development. Therefore, this study was conducted with the aim of evaluating and authenticating the nutritional parameters, essential oil and bioactive components found in the various solvent extracts of Moringa oleifera leaves cultivated in the South African ecotype. It also elucidated some of the plants medicinal properties by investigating the antioxidant and antibacterial properties of the plant. The essential oil of the leaves was extracted using two methods (solvent free microwave extraction and hydrodistillation) and analysed using Gas Chromotography/Mass Spectrometer. The safety profile of the leaves was investigated using brine shrimp model. The results from the study revealed that Moringa oleifera leaves cultivated in South Africa were rich in crude protein levels (28.72%) and carbohydrate (28.84%). Among the minerals tested for, the leaves contained high content of calcium (1603.33 mg/100 g), potassium (1690 mg/100 g), zinc (13.03 mg/100 g) and iron (21.13 mg/100 g). The vitamin E content had the highest concentration (89.43 mg/100 g) among the vitamins evaluated. The leaves of Moringa oleifera had low quantities of antinutrients in relation to minerals, thus ensuring nutrients availability. This study identified 15 fatty acids in the dried leaves of Moringa. The highest fatty acid detected were polyunsaturated fatty acids, linoleic acid (56.36) and alpha-linolenic acid (687.58), 7 of the fatty acids were saturated fatty acids, though relatively low besides stearic acid. 15 amino acids were present, 7 of which were essential amino acids, namely; threonine, tyrosine, methionine, valine, phenylalanine, isoleucine and leucine. vi Among the phytochemicals evaluated, the aqueous extract gave the highest total phenolic content (21.01 ± 2.315 mg GAE/g), the acetone extract gave the highest proanthocyanidin (15.33 3.5 mg CE/g) and flavonoid contents (25.04±3.28 mg QE/g), while saponin and alkaloid contents were 27.73 ± 9.97% and 7.32 ± 2.73 % respectively. All the extracts exhibited high radical scavenging power against the 2,2- diphenyl-1-picrylhydrazyl radical with an IC50 less than 0.025 mg/mL. Aqueous extract gave the highest capacity based on ABTS and TAC assays with IC50 of 0.074 mg/ mL and 0.055 mg/mL respectively. Ethanol extract exhibited the least antioxidant capacity among the extracts, as well as the least antimicrobial activity on both Gram −ve and Gram +ve bacteria with all its minimum inhibitory concentration values greater than 5 mg/mL. The acetone extract exhibited the strongest antimicrobial activity among the extracts. A total of 8 and 24 chemical compounds were found from the solvent-free microwave extracted and hydrodistilled oils, respectively. The major components found from hydrodistillation were 2-Hexanal (16.37%), Nonanal (6.09%), 5 9-undecadien-2-one 6, 10 dimethyl- (e) - (8.01%), trans-beta-Ionone (8.02%) and octadecane (9.67%). For the solvent free microwave extracted oil, Benzene acetaldehyde (5.68%), Octadecane, Pentacosane and Eicosane which were 11.03%, were the major components. Toxicity evaluation revealed that mortality was time dependent. As the exposure period increased, mortality kept increasing. The hatching success of the cysts in acetone, aqueous and ethanol extracts were 35.7, 33.6 and 35.2% respectively. Acetone extract showed the most prominent hatching success. Hatchability and lethality were in a concentration dependent fashion. Among the extracts, acetone extract exhibited the highest lethality (12.3%) to the nauplii, followed by ethanol (10.9%), then aqueous (5.6%) extracts. All the results obtained from this study suggest that Moringa has the potential of eradicating malnutrition and aid health. It contains the necessary nutritional and bioactive compounds and the leaves proved not to be toxic at the levels (0.0625 – 1 mg/mL) tested.
- Full Text:
- Date Issued: 2019
- Authors: Yako, Zomsa
- Date: 2019
- Subjects: Moringa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14605 , vital:40021
- Description: Moringa oleifera Lam. is native to the Indian ecotype, which has become naturalized in many tropic and subtropic regions worldwide, thus a great variation in the bioactive compounds of the plant is recorded. The introduction of Moringa oleifera to South Africa occurred in the turn of the twentieth century with the aim of combating malnourishment, aiding health and fostering economic development. Therefore, this study was conducted with the aim of evaluating and authenticating the nutritional parameters, essential oil and bioactive components found in the various solvent extracts of Moringa oleifera leaves cultivated in the South African ecotype. It also elucidated some of the plants medicinal properties by investigating the antioxidant and antibacterial properties of the plant. The essential oil of the leaves was extracted using two methods (solvent free microwave extraction and hydrodistillation) and analysed using Gas Chromotography/Mass Spectrometer. The safety profile of the leaves was investigated using brine shrimp model. The results from the study revealed that Moringa oleifera leaves cultivated in South Africa were rich in crude protein levels (28.72%) and carbohydrate (28.84%). Among the minerals tested for, the leaves contained high content of calcium (1603.33 mg/100 g), potassium (1690 mg/100 g), zinc (13.03 mg/100 g) and iron (21.13 mg/100 g). The vitamin E content had the highest concentration (89.43 mg/100 g) among the vitamins evaluated. The leaves of Moringa oleifera had low quantities of antinutrients in relation to minerals, thus ensuring nutrients availability. This study identified 15 fatty acids in the dried leaves of Moringa. The highest fatty acid detected were polyunsaturated fatty acids, linoleic acid (56.36) and alpha-linolenic acid (687.58), 7 of the fatty acids were saturated fatty acids, though relatively low besides stearic acid. 15 amino acids were present, 7 of which were essential amino acids, namely; threonine, tyrosine, methionine, valine, phenylalanine, isoleucine and leucine. vi Among the phytochemicals evaluated, the aqueous extract gave the highest total phenolic content (21.01 ± 2.315 mg GAE/g), the acetone extract gave the highest proanthocyanidin (15.33 3.5 mg CE/g) and flavonoid contents (25.04±3.28 mg QE/g), while saponin and alkaloid contents were 27.73 ± 9.97% and 7.32 ± 2.73 % respectively. All the extracts exhibited high radical scavenging power against the 2,2- diphenyl-1-picrylhydrazyl radical with an IC50 less than 0.025 mg/mL. Aqueous extract gave the highest capacity based on ABTS and TAC assays with IC50 of 0.074 mg/ mL and 0.055 mg/mL respectively. Ethanol extract exhibited the least antioxidant capacity among the extracts, as well as the least antimicrobial activity on both Gram −ve and Gram +ve bacteria with all its minimum inhibitory concentration values greater than 5 mg/mL. The acetone extract exhibited the strongest antimicrobial activity among the extracts. A total of 8 and 24 chemical compounds were found from the solvent-free microwave extracted and hydrodistilled oils, respectively. The major components found from hydrodistillation were 2-Hexanal (16.37%), Nonanal (6.09%), 5 9-undecadien-2-one 6, 10 dimethyl- (e) - (8.01%), trans-beta-Ionone (8.02%) and octadecane (9.67%). For the solvent free microwave extracted oil, Benzene acetaldehyde (5.68%), Octadecane, Pentacosane and Eicosane which were 11.03%, were the major components. Toxicity evaluation revealed that mortality was time dependent. As the exposure period increased, mortality kept increasing. The hatching success of the cysts in acetone, aqueous and ethanol extracts were 35.7, 33.6 and 35.2% respectively. Acetone extract showed the most prominent hatching success. Hatchability and lethality were in a concentration dependent fashion. Among the extracts, acetone extract exhibited the highest lethality (12.3%) to the nauplii, followed by ethanol (10.9%), then aqueous (5.6%) extracts. All the results obtained from this study suggest that Moringa has the potential of eradicating malnutrition and aid health. It contains the necessary nutritional and bioactive compounds and the leaves proved not to be toxic at the levels (0.0625 – 1 mg/mL) tested.
- Full Text:
- Date Issued: 2019
- «
- ‹
- 1
- ›
- »