The effects of booster breaks during a sedentary night shift on physiological, psychomotor, psycho-physiological, and cognitive performance over a 3 night shift habituation phase
- Authors: Lombard, Wesley Ross
- Date: 2010
- Subjects: Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5116 , http://hdl.handle.net/10962/d1005194 , Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Description: Despite extensive research into shift work, workers working under rotating shift conditions are still plagued by the effects of the desynchronisation resulting from working against their natural circadian rhythms. Additionally, modern industries are shifting towards tasks requiring greater cognitive demand with less manual labour incorporated into the tasks. Research into operator based tasks, and hence those of a sedentary cognitive base both during day and night shifts, has been focusing on the effectiveness of the standard rest/break schedule. Research indicating that the standard rest break schedule is often ineffective in eliminating operator discomfort and performance deterioration, with these affects argued to be more pronounced during a night shift schedule. Therefore current research set out to investigate alternative rest break schedules, incorporating a short bout of physical activity and stretching exercises which are proposed to enhance performance and subjective mood, while eliminating operator discomfort for sedentary based cognitive tasks. Three conditions were tested during a three day habituation shift cycle within a laboratory, incorporating two night shift groups (control and experimental) and a control day shift group. Twelve subjects made up each group, with the two night shift groups completing the shift schedule together. The control groups followed a typical 8 hour shift schedule while the experimental group performed a booster break (exercise and stretches) activity for 7.5 minutes every hour during the night shift schedule. Over the course of the shift, subjects completed a battery of six tests providing data on physiological measurements (heart rate and temperature), performance criteria (reaction time responses, memory and neurobiological) and subjective measures. Responses obtained for all the different parameters measured indicated a strong circadian influence for the majority of the variables, indicating the course of natural down regulation within physiological and performance criteria over the night shift. The booster break significantly improved reaction time performance, subjective ratings and resulted in a high sustainable activity level. Day shift comparisons indicating that within subjective measures and reaction time performance, the booster break resulted in similar responses to those of the day shift workers, while the control night shift groups reported significantly lowers results. Additionally, the booster break had positive influences during the circadian nadir, significantly improving parameters of performance and subjective ratings of sleepiness. The results of this study indicating which variables are strong predictors and indicators of the oscillations in performance and subjective ratings due to the circadian changes. The booster break interventions had positive effects on subjective ratings and reaction time performance, while also being argued to decrease the burden placed on the cardiac system as a result of increased sympathetic tone during the night shift, while additionally resulting in similar responses to those of day shift workers. Further studies are required, however, to provide conclusive evidence particularly within a working situation over a longer shift schedule.
- Full Text:
- Date Issued: 2010
- Authors: Lombard, Wesley Ross
- Date: 2010
- Subjects: Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5116 , http://hdl.handle.net/10962/d1005194 , Night work , Shift systems , Performance , Exercise , Exercise -- Physiological aspects , Exercise -- Psychological aspects , Cognition -- Effect of exercise on , Motor ability
- Description: Despite extensive research into shift work, workers working under rotating shift conditions are still plagued by the effects of the desynchronisation resulting from working against their natural circadian rhythms. Additionally, modern industries are shifting towards tasks requiring greater cognitive demand with less manual labour incorporated into the tasks. Research into operator based tasks, and hence those of a sedentary cognitive base both during day and night shifts, has been focusing on the effectiveness of the standard rest/break schedule. Research indicating that the standard rest break schedule is often ineffective in eliminating operator discomfort and performance deterioration, with these affects argued to be more pronounced during a night shift schedule. Therefore current research set out to investigate alternative rest break schedules, incorporating a short bout of physical activity and stretching exercises which are proposed to enhance performance and subjective mood, while eliminating operator discomfort for sedentary based cognitive tasks. Three conditions were tested during a three day habituation shift cycle within a laboratory, incorporating two night shift groups (control and experimental) and a control day shift group. Twelve subjects made up each group, with the two night shift groups completing the shift schedule together. The control groups followed a typical 8 hour shift schedule while the experimental group performed a booster break (exercise and stretches) activity for 7.5 minutes every hour during the night shift schedule. Over the course of the shift, subjects completed a battery of six tests providing data on physiological measurements (heart rate and temperature), performance criteria (reaction time responses, memory and neurobiological) and subjective measures. Responses obtained for all the different parameters measured indicated a strong circadian influence for the majority of the variables, indicating the course of natural down regulation within physiological and performance criteria over the night shift. The booster break significantly improved reaction time performance, subjective ratings and resulted in a high sustainable activity level. Day shift comparisons indicating that within subjective measures and reaction time performance, the booster break resulted in similar responses to those of the day shift workers, while the control night shift groups reported significantly lowers results. Additionally, the booster break had positive influences during the circadian nadir, significantly improving parameters of performance and subjective ratings of sleepiness. The results of this study indicating which variables are strong predictors and indicators of the oscillations in performance and subjective ratings due to the circadian changes. The booster break interventions had positive effects on subjective ratings and reaction time performance, while also being argued to decrease the burden placed on the cardiac system as a result of increased sympathetic tone during the night shift, while additionally resulting in similar responses to those of day shift workers. Further studies are required, however, to provide conclusive evidence particularly within a working situation over a longer shift schedule.
- Full Text:
- Date Issued: 2010
The effects of glove fit on task performance and on the human operator
- Authors: Stack, Jessica Danielle
- Date: 2010
- Subjects: Hand -- Anatomy , Hand -- Wounds and injuries , Hand -- Care and hygiene , Gloves , Safety education, Industrial , Human-machine systems , Industrial safety , Industrial accidents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5119 , http://hdl.handle.net/10962/d1005197 , Hand -- Anatomy , Hand -- Wounds and injuries , Hand -- Care and hygiene , Gloves , Safety education, Industrial , Human-machine systems , Industrial safety , Industrial accidents
- Description: The hand is one of the most complex of all of the anatomical structures in the human body. It has been found that hand injuries are among the most frequent injuries that occur to the body, predominantly during industrial activities. It has therefore been concluded that more research is needed into protective factors, such as glove use. The design features of a glove emphasise either protection or performance. There is often a trade-off between increased safety and performance capability when donning gloves. It has been determined that gloves which are fitted and comfortable for the worker may provide the best compromise between protective functions and decreased performance. This investigation aimed to assess the influence of glove fit on the performance attributes of industrial tasks, as well as on the responses of the human operator. Glove fit was analysed as 35 male participants donned three different glove sizes during each test, including a best-fitting glove, a glove one size smaller than best-fitting, and a glove one size larger than best-fitting. For each glove size, gloves of two differing materials were tested, namely nitrile and neoprene. A barehanded condition was also tested, totalling seven gloved/barehanded conditions for each test. The seven conditions were assessed in a laboratory setting in a battery of tests. This consisted of components of task performance, including maximum pulling and pushing force, maximum torque, precision of force, tactility, speed and accuracy and dexterity. The performance responses were recorded, as well as participants’ perceptual responses using the Rating of Perceived Exertion scale, and muscle activity. Six muscles were selected: Flexor Digitorum Superficialis, Flexor Pollicus Longus, Extensor Carpi Ulnaris, Extensor Carpi Radialis, Flexor Carpi Ulnaris and Flexor Carpi Radialis. The results revealed that glove fit does affect certain spects of performance, and influences human operator responses for selected task components. Furthermore, discrepancies were distinguished between orking barehanded and working with an optimally fitted glove. There was also a glove material effect established. Overall, it was found that muscle activity when exerting maximum force in a pushing and pulling direction was optimal with the nitrile glove material. Maximum torque performance was enhanced with the use of a best-fitting glove, as compared with an ill-fitting glove or barehanded work. Force precision was preferable when barehanded, as opposed to the tactility task which rendered optimal results with a best-fitting glove. The same was found for speed and accuracy results, as glove fit appeared to have no effect on performance, but performance was improved when participants were barehanded. Dexterity performance was the most conclusively influenced by the conditions, resulting in barehanded performance being optimal. However, should a glove be necessary for a given task, an optimally-fitted glove which is of a thinner material would be recommended. It is necessary to distinguish the performance components of a task within industry and select the most appropriate glove for optimal performance and the least risk of overexertion.
- Full Text:
- Date Issued: 2010
- Authors: Stack, Jessica Danielle
- Date: 2010
- Subjects: Hand -- Anatomy , Hand -- Wounds and injuries , Hand -- Care and hygiene , Gloves , Safety education, Industrial , Human-machine systems , Industrial safety , Industrial accidents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5119 , http://hdl.handle.net/10962/d1005197 , Hand -- Anatomy , Hand -- Wounds and injuries , Hand -- Care and hygiene , Gloves , Safety education, Industrial , Human-machine systems , Industrial safety , Industrial accidents
- Description: The hand is one of the most complex of all of the anatomical structures in the human body. It has been found that hand injuries are among the most frequent injuries that occur to the body, predominantly during industrial activities. It has therefore been concluded that more research is needed into protective factors, such as glove use. The design features of a glove emphasise either protection or performance. There is often a trade-off between increased safety and performance capability when donning gloves. It has been determined that gloves which are fitted and comfortable for the worker may provide the best compromise between protective functions and decreased performance. This investigation aimed to assess the influence of glove fit on the performance attributes of industrial tasks, as well as on the responses of the human operator. Glove fit was analysed as 35 male participants donned three different glove sizes during each test, including a best-fitting glove, a glove one size smaller than best-fitting, and a glove one size larger than best-fitting. For each glove size, gloves of two differing materials were tested, namely nitrile and neoprene. A barehanded condition was also tested, totalling seven gloved/barehanded conditions for each test. The seven conditions were assessed in a laboratory setting in a battery of tests. This consisted of components of task performance, including maximum pulling and pushing force, maximum torque, precision of force, tactility, speed and accuracy and dexterity. The performance responses were recorded, as well as participants’ perceptual responses using the Rating of Perceived Exertion scale, and muscle activity. Six muscles were selected: Flexor Digitorum Superficialis, Flexor Pollicus Longus, Extensor Carpi Ulnaris, Extensor Carpi Radialis, Flexor Carpi Ulnaris and Flexor Carpi Radialis. The results revealed that glove fit does affect certain spects of performance, and influences human operator responses for selected task components. Furthermore, discrepancies were distinguished between orking barehanded and working with an optimally fitted glove. There was also a glove material effect established. Overall, it was found that muscle activity when exerting maximum force in a pushing and pulling direction was optimal with the nitrile glove material. Maximum torque performance was enhanced with the use of a best-fitting glove, as compared with an ill-fitting glove or barehanded work. Force precision was preferable when barehanded, as opposed to the tactility task which rendered optimal results with a best-fitting glove. The same was found for speed and accuracy results, as glove fit appeared to have no effect on performance, but performance was improved when participants were barehanded. Dexterity performance was the most conclusively influenced by the conditions, resulting in barehanded performance being optimal. However, should a glove be necessary for a given task, an optimally-fitted glove which is of a thinner material would be recommended. It is necessary to distinguish the performance components of a task within industry and select the most appropriate glove for optimal performance and the least risk of overexertion.
- Full Text:
- Date Issued: 2010
The geology of the Witteberg group, Cape supergroup, with specific focus on the Perdepoort member as a potential silica source
- Authors: Olivier, Wernich Corné
- Date: 2010
- Subjects: Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10660 , http://hdl.handle.net/10948/1386 , http://hdl.handle.net/10948/d1012889 , Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Description: Selected outcrops of the Upper Devonian to Lower Carboniferous, Witteberg Group, Cape Supergroup were mineralogically and structurally analyzed. The study area is located approximately 30km northwest of Kirkwood and 10km south of Darlington Dam, Eastern Cape, South Africa. Strata predominantly consist of arenaceous Witpoort Formation, which includes the Perdepoort, and Rooirand Members. The Perdepoort Member is a thinly bedded quartzite also known as the "white streak". The Rooirand Member quartzite is a highly iron stained red-brown quartzite. The dark-grey, pyritic rich shales of the Kweekvlei Formation overlie the Witpoort Formation in the southern half of the study site. These shales are highly deformed and display closely spaced thrust faults and close folds. The study area encapsulates a range of folding from tight to open folds. Faulting consists of low angle north verging thrust fault, south verging back thrusts, south and north dipping normal faults, and strike-slip faults. Closely spaced, fore-land verging thrusts faults predominate over hinterland verging back thrusts. Normal faulting post-dates thrust faulting and utilized weaknesses in axial planar cleavage and in certain instances existing thrust fault planes. Strike-slip faulting post-dates thrusting and has in places reactivated pre-existing thrust fault planes. Macro scale folding includes overturned synclines and large anticlines which have been eroded, exposing older strata. Fold axes plunge at low to moderate angles west-southwest. This correlates with tension gashes which indicate north westward directed forces. Eastward directed forces are confirmed by the presence of tension gashes and strike-slip movement. The local geology displays north westward directed compression followed by strike-slip movement. Normal faulting post-dates all other structures and is associated with the Mesozoic break-up of Gondwana. The Perdepoort Member was sampled along strike, at different outcrop latitudes. Seven samples were selected for scanning electron microscope analysis. Samples are composed almost entirely of quartz; accessories include, biotite, muscovite, sericite, baryte, and apatite. Epigenetic hematite is present along cracks within certain samples Epigenetic hematite occur along cracks with oxides and phosphates in the form of rutile, apatite and monazite present in a number of samples. When compared to other silica extraction operations the Perdepoort Member appears viable for explotation. However, for the solar cell industry the purity of this horizon is clearly far below that required for industy.
- Full Text:
- Date Issued: 2010
- Authors: Olivier, Wernich Corné
- Date: 2010
- Subjects: Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10660 , http://hdl.handle.net/10948/1386 , http://hdl.handle.net/10948/d1012889 , Geology -- South Africa -- Witteberg Group , Stratiography -- South Africa -- Witteberg Group , Silicate minerals -- South Africa -- Witteberg Group
- Description: Selected outcrops of the Upper Devonian to Lower Carboniferous, Witteberg Group, Cape Supergroup were mineralogically and structurally analyzed. The study area is located approximately 30km northwest of Kirkwood and 10km south of Darlington Dam, Eastern Cape, South Africa. Strata predominantly consist of arenaceous Witpoort Formation, which includes the Perdepoort, and Rooirand Members. The Perdepoort Member is a thinly bedded quartzite also known as the "white streak". The Rooirand Member quartzite is a highly iron stained red-brown quartzite. The dark-grey, pyritic rich shales of the Kweekvlei Formation overlie the Witpoort Formation in the southern half of the study site. These shales are highly deformed and display closely spaced thrust faults and close folds. The study area encapsulates a range of folding from tight to open folds. Faulting consists of low angle north verging thrust fault, south verging back thrusts, south and north dipping normal faults, and strike-slip faults. Closely spaced, fore-land verging thrusts faults predominate over hinterland verging back thrusts. Normal faulting post-dates thrust faulting and utilized weaknesses in axial planar cleavage and in certain instances existing thrust fault planes. Strike-slip faulting post-dates thrusting and has in places reactivated pre-existing thrust fault planes. Macro scale folding includes overturned synclines and large anticlines which have been eroded, exposing older strata. Fold axes plunge at low to moderate angles west-southwest. This correlates with tension gashes which indicate north westward directed forces. Eastward directed forces are confirmed by the presence of tension gashes and strike-slip movement. The local geology displays north westward directed compression followed by strike-slip movement. Normal faulting post-dates all other structures and is associated with the Mesozoic break-up of Gondwana. The Perdepoort Member was sampled along strike, at different outcrop latitudes. Seven samples were selected for scanning electron microscope analysis. Samples are composed almost entirely of quartz; accessories include, biotite, muscovite, sericite, baryte, and apatite. Epigenetic hematite is present along cracks within certain samples Epigenetic hematite occur along cracks with oxides and phosphates in the form of rutile, apatite and monazite present in a number of samples. When compared to other silica extraction operations the Perdepoort Member appears viable for explotation. However, for the solar cell industry the purity of this horizon is clearly far below that required for industy.
- Full Text:
- Date Issued: 2010
The ichthyofauna and piscivorous avifauna in a small temporarily open/closed Eastern Cape estuary, South Africa
- Authors: Blake, Justin David
- Date: 2010
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Bird populations -- South Africa -- Riet River Estuary , Estuaries -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Riet River Estuary , Estuarine animals -- South Africa -- Riet River Estuary , Birds -- South Africa -- Riet River Estuary , Riet River Estuary (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5709 , http://hdl.handle.net/10962/d1005395 , Estuarine fishes -- South Africa -- Eastern Cape , Bird populations -- South Africa -- Riet River Estuary , Estuaries -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Riet River Estuary , Estuarine animals -- South Africa -- Riet River Estuary , Birds -- South Africa -- Riet River Estuary , Riet River Estuary (South Africa)
- Description: The spatial and temporal patterns in selected components of the ichthyofauna and piscivorous avifauna in the small temporarily open/closed Riet River Estuary located on the eastern seaboard of southern Africa was investigated monthly over the period August 2005 to July 2006. The ichthyofauna within the littoral zone of the estuary was sampled using a 5 m seine net (8 stations) while a 30 m seine net (4 stations) was employed to sample the fish in the channel. Bird counts were made along repeat transects along the length of the estuary. Total ichthyofaunal abundances and biomass ranged between 1.60 and 8.67 individuals m⁻² and 0.45 to 21.76 g wwt m⁻² within the littoral zone, and between 0.08 and 0.44 individuals m⁻² and 0.58 and 36.52 g wwt m⁻² in the channel of the estuary. The highest values were generally recorded during the summer months. Results of the numerical analysis indicated that the breaching events recorded over the study period did not lead to a common trend in the ichthyofaunal community. In the absence of a link to the marine environment, the ichthyofaunal community in the littoral zone was numerically dominated by the estuarine resident species, Gilchristella aestuaria and to a lesser extent by Glossogobius callidus, which collectively accounted for ca. 54% of the total ichthyofauna sampled. The establishment of a link to the marine environment coincided with increased numbers of marine breeding species including Atherina breviceps and Rhabdosargus holubi to total fish counts within the estuary. Hierarchical cluster analysis did not identify any spatial patterns in the community structure of the ichthyofauna in the littoral zone or channel zone of the estuary, which could likely be linked to the absence of any distinct horizontal patterns in salinity and temperature within the system. A total of thirteen piscivorous bird species was recorded over the study period. Of the recorded species, six species were wading piscivores, four species were aerial divers and the remaining three species were pursuit swimmers. There were no significant correlations between the estimates of the ichthyofaunal abundance and biomass and bird numbers evident during the study (P> 0.05 in both cases). The Reed Cormorant (Phalacrocorax africanus) was the dominant species throughout the study, with a mean of 8.25 (SD ± 7.90) individuals per count. Mean values of the Pied Kingfisher (Ceryle rudis) and Giant Kingfisher (Megaceryle maximus) were 3.42 (SD ± 1.20) and 1.17 (SD ± 0.60) individuals per count, respectively. The remaining species revealed mean values < 0.5 individuals per count. The highest bird numbers were recorded in winter reflecting the migration of large numbers of the Reed Cormorant into the system. Breaching events were associated with a decrease in total bird numbers, which was most likely due to loss of potential foraging habitat (littoral zone) for waders resulting from reduced water levels. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 26.35 to 140.58 kg per month. The observed variability could be linked to mouth phase and bird numbers.
- Full Text:
- Date Issued: 2010
- Authors: Blake, Justin David
- Date: 2010
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Bird populations -- South Africa -- Riet River Estuary , Estuaries -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Riet River Estuary , Estuarine animals -- South Africa -- Riet River Estuary , Birds -- South Africa -- Riet River Estuary , Riet River Estuary (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5709 , http://hdl.handle.net/10962/d1005395 , Estuarine fishes -- South Africa -- Eastern Cape , Bird populations -- South Africa -- Riet River Estuary , Estuaries -- South Africa -- Eastern Cape , Fish populations -- South Africa -- Riet River Estuary , Estuarine animals -- South Africa -- Riet River Estuary , Birds -- South Africa -- Riet River Estuary , Riet River Estuary (South Africa)
- Description: The spatial and temporal patterns in selected components of the ichthyofauna and piscivorous avifauna in the small temporarily open/closed Riet River Estuary located on the eastern seaboard of southern Africa was investigated monthly over the period August 2005 to July 2006. The ichthyofauna within the littoral zone of the estuary was sampled using a 5 m seine net (8 stations) while a 30 m seine net (4 stations) was employed to sample the fish in the channel. Bird counts were made along repeat transects along the length of the estuary. Total ichthyofaunal abundances and biomass ranged between 1.60 and 8.67 individuals m⁻² and 0.45 to 21.76 g wwt m⁻² within the littoral zone, and between 0.08 and 0.44 individuals m⁻² and 0.58 and 36.52 g wwt m⁻² in the channel of the estuary. The highest values were generally recorded during the summer months. Results of the numerical analysis indicated that the breaching events recorded over the study period did not lead to a common trend in the ichthyofaunal community. In the absence of a link to the marine environment, the ichthyofaunal community in the littoral zone was numerically dominated by the estuarine resident species, Gilchristella aestuaria and to a lesser extent by Glossogobius callidus, which collectively accounted for ca. 54% of the total ichthyofauna sampled. The establishment of a link to the marine environment coincided with increased numbers of marine breeding species including Atherina breviceps and Rhabdosargus holubi to total fish counts within the estuary. Hierarchical cluster analysis did not identify any spatial patterns in the community structure of the ichthyofauna in the littoral zone or channel zone of the estuary, which could likely be linked to the absence of any distinct horizontal patterns in salinity and temperature within the system. A total of thirteen piscivorous bird species was recorded over the study period. Of the recorded species, six species were wading piscivores, four species were aerial divers and the remaining three species were pursuit swimmers. There were no significant correlations between the estimates of the ichthyofaunal abundance and biomass and bird numbers evident during the study (P> 0.05 in both cases). The Reed Cormorant (Phalacrocorax africanus) was the dominant species throughout the study, with a mean of 8.25 (SD ± 7.90) individuals per count. Mean values of the Pied Kingfisher (Ceryle rudis) and Giant Kingfisher (Megaceryle maximus) were 3.42 (SD ± 1.20) and 1.17 (SD ± 0.60) individuals per count, respectively. The remaining species revealed mean values < 0.5 individuals per count. The highest bird numbers were recorded in winter reflecting the migration of large numbers of the Reed Cormorant into the system. Breaching events were associated with a decrease in total bird numbers, which was most likely due to loss of potential foraging habitat (littoral zone) for waders resulting from reduced water levels. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 26.35 to 140.58 kg per month. The observed variability could be linked to mouth phase and bird numbers.
- Full Text:
- Date Issued: 2010
The impact of a one-hour self-selected nap opportunity on physiological and performance variables during a simulated night shift
- Authors: Davy, Jonathan Patrick
- Date: 2010
- Subjects: Night work , Naps (sleep) in the workplace , Naps (sleep) in the workplace -- Case studies , Shift systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5123 , http://hdl.handle.net/10962/d1005201 , Night work , Naps (sleep) in the workplace , Naps (sleep) in the workplace -- Case studies , Shift systems
- Description: Napping has been explored extensively as a means of counteracting the negative effects associated with shift work. A significant amount of this research has focused on the implementation of scheduled naps, with few studies considering flexible nap schemes. The current study therefore aimed to assess the effects of a flexible nap opportunity on the physiological, cognitive, performance, neurophysiological and subjective responses of a group of non shift workers over the course of a three-day simulated night shift regime. Additional foci were the effects of the nap condition on the extent of the circadian adaptation of the subjects to the irregular work schedule and the circadian-related influences associated with being awake during the night. 36 subjects – 18 males and 18 females – were recruited to participate in the current study. The data collection spanned twelve days, during which four, three-day long shift cycles were set up: three night shift cycles and one day shift cycle. During each night shift cycle, three separate experimental conditions were staggered, namely the nap condition, the no nap condition and a booster break condition (a collaborative study that completed the setup). The day shift served as a further comparison. Each cycle comprised of 12 subjects, which meant there were four subjects per condition during each cycle. The shifts were 8 hours in duration, with the no nap group following a standard break schedule evinced in industry. The three breaks taken during the shifts amounted to a total time of 1 hour. The nap group was afforded a 1 hour flexible nap opportunity between 00h00 and 03h00 with no other breaks. Therefore, both conditions had the same amount of work time. During the shifts, subjects performed two simple, low arousal tasks (beading and packing) and completed a test battery roughly every two hours which was comprised of physiological, performance, neurophysiological and subjective measures. It was found that the inclusion of the nap opportunity significantly improved output performance and response time during a low precision, modified Fitts tapping task over the course of three night shifts, relative to no napping. Physiologically, napping resulted in higher heart rate frequency measures by the end of the shifts, which were also accompanied by significant reductions in subjective sleepiness ratings during all iii the night shifts. The nap group’s responses in this case, did not differ significantly from those of the day shift. Both simple reaction time and memory performances improved as a result of the nap inclusion, but only during the third night shift. The majority of the measures included in the research also depicted the effects of the circadian rhythm, which was indicative of the pronounced effect that this natural biological down regulation has on performance during the night. Napping reduced the severity of these effects during beading performance and measures of subjective sleepiness. With regard to habituation, the nap opportunity also resulted in positive changes in the responses of beading performance, high precision response time, simple reaction time and both subjective sleepiness measures, relative to no napping. Sleep diary responses indicated that although sleep length and quality during the day were significantly reduced for both night-time conditions, recovery sleep (length and quality) for the nap group did not differ significantly from the no nap group. The findings of this research indicate that the inclusion of a flexible napping opportunity during the night shift had positive effects on some physiological, performance and subjective responses, and that this intervention is as beneficial as scheduled napping. Specifically, napping resulted in a significantly higher output during the beading task, relative to the no nap group despite the duration of work time being the same. As such the introduction of a flexible, self-selected nap opportunity is a practical, effective and individual-specific means of alleviating the negative effects of shift work, while improving certain performance parameters. Therefore, industries should consider its inclusion in their fatigue management programs. However, contextspecific considerations must be made, with regard work scheduling, individual differences and task demands when implementing such an intervention. This will ensure that its introduction will be well received and in time, lessen the health and work-related decrements associated with shift work.
- Full Text:
- Date Issued: 2010
- Authors: Davy, Jonathan Patrick
- Date: 2010
- Subjects: Night work , Naps (sleep) in the workplace , Naps (sleep) in the workplace -- Case studies , Shift systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5123 , http://hdl.handle.net/10962/d1005201 , Night work , Naps (sleep) in the workplace , Naps (sleep) in the workplace -- Case studies , Shift systems
- Description: Napping has been explored extensively as a means of counteracting the negative effects associated with shift work. A significant amount of this research has focused on the implementation of scheduled naps, with few studies considering flexible nap schemes. The current study therefore aimed to assess the effects of a flexible nap opportunity on the physiological, cognitive, performance, neurophysiological and subjective responses of a group of non shift workers over the course of a three-day simulated night shift regime. Additional foci were the effects of the nap condition on the extent of the circadian adaptation of the subjects to the irregular work schedule and the circadian-related influences associated with being awake during the night. 36 subjects – 18 males and 18 females – were recruited to participate in the current study. The data collection spanned twelve days, during which four, three-day long shift cycles were set up: three night shift cycles and one day shift cycle. During each night shift cycle, three separate experimental conditions were staggered, namely the nap condition, the no nap condition and a booster break condition (a collaborative study that completed the setup). The day shift served as a further comparison. Each cycle comprised of 12 subjects, which meant there were four subjects per condition during each cycle. The shifts were 8 hours in duration, with the no nap group following a standard break schedule evinced in industry. The three breaks taken during the shifts amounted to a total time of 1 hour. The nap group was afforded a 1 hour flexible nap opportunity between 00h00 and 03h00 with no other breaks. Therefore, both conditions had the same amount of work time. During the shifts, subjects performed two simple, low arousal tasks (beading and packing) and completed a test battery roughly every two hours which was comprised of physiological, performance, neurophysiological and subjective measures. It was found that the inclusion of the nap opportunity significantly improved output performance and response time during a low precision, modified Fitts tapping task over the course of three night shifts, relative to no napping. Physiologically, napping resulted in higher heart rate frequency measures by the end of the shifts, which were also accompanied by significant reductions in subjective sleepiness ratings during all iii the night shifts. The nap group’s responses in this case, did not differ significantly from those of the day shift. Both simple reaction time and memory performances improved as a result of the nap inclusion, but only during the third night shift. The majority of the measures included in the research also depicted the effects of the circadian rhythm, which was indicative of the pronounced effect that this natural biological down regulation has on performance during the night. Napping reduced the severity of these effects during beading performance and measures of subjective sleepiness. With regard to habituation, the nap opportunity also resulted in positive changes in the responses of beading performance, high precision response time, simple reaction time and both subjective sleepiness measures, relative to no napping. Sleep diary responses indicated that although sleep length and quality during the day were significantly reduced for both night-time conditions, recovery sleep (length and quality) for the nap group did not differ significantly from the no nap group. The findings of this research indicate that the inclusion of a flexible napping opportunity during the night shift had positive effects on some physiological, performance and subjective responses, and that this intervention is as beneficial as scheduled napping. Specifically, napping resulted in a significantly higher output during the beading task, relative to the no nap group despite the duration of work time being the same. As such the introduction of a flexible, self-selected nap opportunity is a practical, effective and individual-specific means of alleviating the negative effects of shift work, while improving certain performance parameters. Therefore, industries should consider its inclusion in their fatigue management programs. However, contextspecific considerations must be made, with regard work scheduling, individual differences and task demands when implementing such an intervention. This will ensure that its introduction will be well received and in time, lessen the health and work-related decrements associated with shift work.
- Full Text:
- Date Issued: 2010
The importance of estuarine head waters for fishes in selected Eastern Cape systems, with particular emphasis on the influence of freshwater inflow, migration barriers and non-native predators on the juvenile and small fish component
- Authors: Wasserman, Ryan
- Date: 2010
- Subjects: Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10685 , http://hdl.handle.net/10948/1457 , Estuaries -- South Africa -- Eastern Cape
- Description: The utilisation of estuary headwater environments by young estuary- and marine-spawned fish species was investigated together with the effects of riverflow alteration, in-stream barrier effects and non-native ichthyofauna on the nursery function of these habitats. The distribution and abundance of young estuary- and marine-spawned fish were sampled using seine and fyke nets in the headwater environments of four permanently open Eastern Cape systems, namely the Great Fish, Kowie, Kariega and Sundays Estuaries. Within the suite of study systems, the first of two case studies focussed on barrier effects of in-stream structures on fish migration. This was undertaken in the Sundays River. In the second case study, predation and competition dynamics of the non-native piscivorous Micropterus salmoides on estuary-dependent fish was investigated in the estuary headwater regions of the Kowie River system. In all four estuaries, young estuary-spawned fish species dominated the ichthyofaunal community followed by marine-spawned species, despite varied freshwater inflow resulting in headwaters varying in salinity from fresh to hypersaline. Fish community structure however, differed largely between estuaries, with both freshwater abstraction and unnatural elevation of freshwater into estuaries, as a result of inter-basin transfers, affecting these communities. In-stream structures were found to effect upstream movement of fish in two ways, dependent on the type of barrier. Partial (size-dependent) and complete (species-dependent) restriction to upstream migration of fish by causeway-type instream structures were observed. Weir-type in-stream structures acted as a complete barrier to most species, regardless of fish size. Predation of estuary- and marine-spawned fish species by large sized M. salmoides was recorded, although these fish did not contribute significantly to their diet during this study. However, the main dietary components found in smaller sized M. salmoides stomachs overlap with those of juvenile estuary- and marinespawned fish species, suggesting feeding competition between the juveniles of indigenous and non-native fish species.
- Full Text:
- Date Issued: 2010
- Authors: Wasserman, Ryan
- Date: 2010
- Subjects: Estuaries -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10685 , http://hdl.handle.net/10948/1457 , Estuaries -- South Africa -- Eastern Cape
- Description: The utilisation of estuary headwater environments by young estuary- and marine-spawned fish species was investigated together with the effects of riverflow alteration, in-stream barrier effects and non-native ichthyofauna on the nursery function of these habitats. The distribution and abundance of young estuary- and marine-spawned fish were sampled using seine and fyke nets in the headwater environments of four permanently open Eastern Cape systems, namely the Great Fish, Kowie, Kariega and Sundays Estuaries. Within the suite of study systems, the first of two case studies focussed on barrier effects of in-stream structures on fish migration. This was undertaken in the Sundays River. In the second case study, predation and competition dynamics of the non-native piscivorous Micropterus salmoides on estuary-dependent fish was investigated in the estuary headwater regions of the Kowie River system. In all four estuaries, young estuary-spawned fish species dominated the ichthyofaunal community followed by marine-spawned species, despite varied freshwater inflow resulting in headwaters varying in salinity from fresh to hypersaline. Fish community structure however, differed largely between estuaries, with both freshwater abstraction and unnatural elevation of freshwater into estuaries, as a result of inter-basin transfers, affecting these communities. In-stream structures were found to effect upstream movement of fish in two ways, dependent on the type of barrier. Partial (size-dependent) and complete (species-dependent) restriction to upstream migration of fish by causeway-type instream structures were observed. Weir-type in-stream structures acted as a complete barrier to most species, regardless of fish size. Predation of estuary- and marine-spawned fish species by large sized M. salmoides was recorded, although these fish did not contribute significantly to their diet during this study. However, the main dietary components found in smaller sized M. salmoides stomachs overlap with those of juvenile estuary- and marinespawned fish species, suggesting feeding competition between the juveniles of indigenous and non-native fish species.
- Full Text:
- Date Issued: 2010
The influence of Acacia Mearnsii invasion on soil properties in the Kouga Mountains, Eastern Cape, South Africa
- Van der Waal, Benjamin Wentsel
- Authors: Van der Waal, Benjamin Wentsel
- Date: 2010
- Subjects: Acacia mearnsii -- South Africa , Wattles (Plants) -- South Africa , Soil erosion -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa , Biological invasions -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Biogeography -- South Africa -- Eastern Cape , Soil management -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape , Soils -- Sodium content -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4839 , http://hdl.handle.net/10962/d1005515 , Acacia mearnsii -- South Africa , Wattles (Plants) -- South Africa , Soil erosion -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa , Biological invasions -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Biogeography -- South Africa -- Eastern Cape , Soil management -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape , Soils -- Sodium content -- South Africa -- Eastern Cape
- Description: The invasion of Acacia mearnsii in the Kouga catchment, Eastern Cape, South Africa, has various negative impacts on the ecosystem. These impacts include: reduced species richness, increased water use, increased nutrients and increased N cycling rates. The native shrubby fynbos vegetation has adapted to the acidic nutrient poor soils and Mediterranean climate of the Kouga Mountains. Fynbos, however, is currently being out competed by the much taller Acacia mearnsii trees, due to their competitive nature and ability to fix nitrogen, thereby enriching the soil. The invaded sections of the valley bottoms and lower hill slopes are characterised by an almost complete monoculture of Acacia mearnsii, with very few fynbos species still present. The Department of Water and Environmental Affairs sponsored Working for Water programme started clearing Acacia mearnsii in 1996 in the Kouga Mountains. Cleared sites have remained bare for long periods, indicating that soil properties are not favourable for indigenous propagule re-establishment. The aim of this research was to assess how A. mearnsii invasion and clearing affect fynbos recovery through its impact on soils. This was done by characterising vegetation and soil properties on fynbos, infested and cleared slopes. Vegetation cover for various growth forms was determined and a species list was compiled for each plot. The slope angle, surface hardness, litter cover, bare ground cover and soil depth were measured in the field, whereas water repellency, particle size and the chemical composition were measured in the laboratory. Furthermore, the plant establishment capacity of soils from fynbos, infested and cleared slopes was calculated. This was done by germinating fynbos seeds and growing fynbos plants in soils from the various slopes. The effect that invasion and clearing has on soil erosion was quantified using erosion plots on fynbos, infested and cleared slopes. The invasion and clearing of Acacia mearnsii led to an increase in soil nutrients, especially nitrogen, phosphorus, potassium, carbon and manganese. Furthermore, soils became more acidic, with increased water repellency and reduced surface hardness. The vegetation changed to a tree-dominated structure, replacing the native species. Native plant germination was relatively unaffected by invasion and clearing, with an increase in germination just after clearing. Plant growth of a native grass, Themeda triandra, and herb, Helichrysum umbraculigerum, has increased on soils from cleared slopes. This study showed that soil movement increased on slopes which are invaded and cleared of Acacia mearnsii, with erosion rates doubling on invaded slopes
- Full Text:
- Date Issued: 2010
- Authors: Van der Waal, Benjamin Wentsel
- Date: 2010
- Subjects: Acacia mearnsii -- South Africa , Wattles (Plants) -- South Africa , Soil erosion -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa , Biological invasions -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Biogeography -- South Africa -- Eastern Cape , Soil management -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape , Soils -- Sodium content -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4839 , http://hdl.handle.net/10962/d1005515 , Acacia mearnsii -- South Africa , Wattles (Plants) -- South Africa , Soil erosion -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa , Biological invasions -- South Africa -- Eastern Cape , Alien plants -- South Africa -- Eastern Cape , Invasive plants -- South Africa -- Eastern Cape , Biogeography -- South Africa -- Eastern Cape , Soil management -- South Africa -- Eastern Cape , Soil moisture -- South Africa -- Eastern Cape , Soils -- Sodium content -- South Africa -- Eastern Cape
- Description: The invasion of Acacia mearnsii in the Kouga catchment, Eastern Cape, South Africa, has various negative impacts on the ecosystem. These impacts include: reduced species richness, increased water use, increased nutrients and increased N cycling rates. The native shrubby fynbos vegetation has adapted to the acidic nutrient poor soils and Mediterranean climate of the Kouga Mountains. Fynbos, however, is currently being out competed by the much taller Acacia mearnsii trees, due to their competitive nature and ability to fix nitrogen, thereby enriching the soil. The invaded sections of the valley bottoms and lower hill slopes are characterised by an almost complete monoculture of Acacia mearnsii, with very few fynbos species still present. The Department of Water and Environmental Affairs sponsored Working for Water programme started clearing Acacia mearnsii in 1996 in the Kouga Mountains. Cleared sites have remained bare for long periods, indicating that soil properties are not favourable for indigenous propagule re-establishment. The aim of this research was to assess how A. mearnsii invasion and clearing affect fynbos recovery through its impact on soils. This was done by characterising vegetation and soil properties on fynbos, infested and cleared slopes. Vegetation cover for various growth forms was determined and a species list was compiled for each plot. The slope angle, surface hardness, litter cover, bare ground cover and soil depth were measured in the field, whereas water repellency, particle size and the chemical composition were measured in the laboratory. Furthermore, the plant establishment capacity of soils from fynbos, infested and cleared slopes was calculated. This was done by germinating fynbos seeds and growing fynbos plants in soils from the various slopes. The effect that invasion and clearing has on soil erosion was quantified using erosion plots on fynbos, infested and cleared slopes. The invasion and clearing of Acacia mearnsii led to an increase in soil nutrients, especially nitrogen, phosphorus, potassium, carbon and manganese. Furthermore, soils became more acidic, with increased water repellency and reduced surface hardness. The vegetation changed to a tree-dominated structure, replacing the native species. Native plant germination was relatively unaffected by invasion and clearing, with an increase in germination just after clearing. Plant growth of a native grass, Themeda triandra, and herb, Helichrysum umbraculigerum, has increased on soils from cleared slopes. This study showed that soil movement increased on slopes which are invaded and cleared of Acacia mearnsii, with erosion rates doubling on invaded slopes
- Full Text:
- Date Issued: 2010
The isolation of muscle activity and ground reaction force patterns associated with postural control in four load manipulation tasks
- Authors: Pettengell, Clare Louise
- Date: 2010
- Subjects: Physical fitness , Exercise , Materials handling , Manual work , Lifting and carrying
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5125 , http://hdl.handle.net/10962/d1005203 , Physical fitness , Exercise , Materials handling , Manual work , Lifting and carrying
- Description: Although much effort has been placed into the reduction of risks associated with manual materials handling, risk of musculoskeletal disorder development remains high. This may be due to the additional muscle activity necessary for the maintenance of postural equilibrium during work tasks. This research proposes that postural control and subsequent additional muscle activity is influenced by the magnitude of the external load and the degree of body movement. The objective of this research was to identify whether performing tasks with increased external load and with a greater degree of trunk motion places additional strain on the musculoskeletal system in excess of that imposed by task demands. Twenty-four male and twenty-four female subjects performed four load manipulation tasks under three loading conditions (0.8kg, 1.6kg, and 4kg). Each task comprised of a static and dynamic condition. For the static condition, subjects maintained a stipulated posture for ten seconds. The dynamic condition required subjects to move and replace a box once every three seconds, such that a complete lift and lower cycle was performed in six seconds. Throughout task completion, muscle activity of six pairs of trunk muscles were analysed using surface electromyography. This was accompanied by data regarding ground reaction forces obtained through the use of a force platform. After the completion of each condition subjects were required to identify and rate body discomfort. Differential analysis was used to isolate the muscle activity and ground reaction forces attributed to increased external load and increased trunk movement. It was found that the heaviest loading conditions (4kg) resulted in significantly greater (p<0.05) muscle activation in the majority of muscles during all tasks investigated. The trend of muscle activity attributed to load was similar in all significantly altered muscles and activation was greatest in the heaviest loading condition. A degree of movement efficiency occurred in some muscles when manipulating loads of 0.8kg and 1.6kg. At greater loads, this did not occur suggesting that heavier loading conditions result in additional strain on the body in excess of that imposed by task demands. In manipulated data, trend of vertical ground reaction forces increased with increased load in all tasks. Sagittal movement of the centre of pressure attributed to load was significantly affected in manipulated data in the second movement phase of the “hip shoulder” task and the second movement phase of the “hip twist” task. The “hip reach” task was most affected by increased load magnitude as muscle activity attributed to load was significantly different (p<0.05) under increased loading conditions in both movement phases in all muscles. Further, a significant interactional effect (p<0.05) between condition and data point was found in all muscles with the exception of the right and left lumbar erector spinae during the second movement phase of the “hip reach” task. Muscle activity associated with increased trunk motion resulted in additional strain on the trunk muscles in the “hip shoulder” and “hip reach” tasks as muscle activity associated with the static component of each of the above tasks was greater than that of the dynamic tasks. Trend of ground reaction forces attributed to increased trunk motion generally increased under increased loading conditions. Additionally, a significant interactional effect (p<0.05) between load and muscle activity pattern was found in all muscles during all tasks, with the exception of the right rectus abdominis in the first movement phase of the “hip shoulder’ task, the left rectus abdominis in the second movement phase of the “hip knee” task and the right latissimus dorsi during the first movement phase of the “hip twist” task. This was accompanied by a significant interactional effect (p<0.05) between load and sagittal centre of pressure movement attributed to load, in both movement phases of all tasks investigated. From this research it can be proposed that guidelines may underestimate risk and subsequently under predict the strain in tasks performed with greater external loads as well as tasks which require a greater degree of trunk motion. Therefore, this study illustrates the importance of the consideration of the muscle activity necessary to maintain postural equilibrium in overall load analyses.
- Full Text:
- Date Issued: 2010
- Authors: Pettengell, Clare Louise
- Date: 2010
- Subjects: Physical fitness , Exercise , Materials handling , Manual work , Lifting and carrying
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5125 , http://hdl.handle.net/10962/d1005203 , Physical fitness , Exercise , Materials handling , Manual work , Lifting and carrying
- Description: Although much effort has been placed into the reduction of risks associated with manual materials handling, risk of musculoskeletal disorder development remains high. This may be due to the additional muscle activity necessary for the maintenance of postural equilibrium during work tasks. This research proposes that postural control and subsequent additional muscle activity is influenced by the magnitude of the external load and the degree of body movement. The objective of this research was to identify whether performing tasks with increased external load and with a greater degree of trunk motion places additional strain on the musculoskeletal system in excess of that imposed by task demands. Twenty-four male and twenty-four female subjects performed four load manipulation tasks under three loading conditions (0.8kg, 1.6kg, and 4kg). Each task comprised of a static and dynamic condition. For the static condition, subjects maintained a stipulated posture for ten seconds. The dynamic condition required subjects to move and replace a box once every three seconds, such that a complete lift and lower cycle was performed in six seconds. Throughout task completion, muscle activity of six pairs of trunk muscles were analysed using surface electromyography. This was accompanied by data regarding ground reaction forces obtained through the use of a force platform. After the completion of each condition subjects were required to identify and rate body discomfort. Differential analysis was used to isolate the muscle activity and ground reaction forces attributed to increased external load and increased trunk movement. It was found that the heaviest loading conditions (4kg) resulted in significantly greater (p<0.05) muscle activation in the majority of muscles during all tasks investigated. The trend of muscle activity attributed to load was similar in all significantly altered muscles and activation was greatest in the heaviest loading condition. A degree of movement efficiency occurred in some muscles when manipulating loads of 0.8kg and 1.6kg. At greater loads, this did not occur suggesting that heavier loading conditions result in additional strain on the body in excess of that imposed by task demands. In manipulated data, trend of vertical ground reaction forces increased with increased load in all tasks. Sagittal movement of the centre of pressure attributed to load was significantly affected in manipulated data in the second movement phase of the “hip shoulder” task and the second movement phase of the “hip twist” task. The “hip reach” task was most affected by increased load magnitude as muscle activity attributed to load was significantly different (p<0.05) under increased loading conditions in both movement phases in all muscles. Further, a significant interactional effect (p<0.05) between condition and data point was found in all muscles with the exception of the right and left lumbar erector spinae during the second movement phase of the “hip reach” task. Muscle activity associated with increased trunk motion resulted in additional strain on the trunk muscles in the “hip shoulder” and “hip reach” tasks as muscle activity associated with the static component of each of the above tasks was greater than that of the dynamic tasks. Trend of ground reaction forces attributed to increased trunk motion generally increased under increased loading conditions. Additionally, a significant interactional effect (p<0.05) between load and muscle activity pattern was found in all muscles during all tasks, with the exception of the right rectus abdominis in the first movement phase of the “hip shoulder’ task, the left rectus abdominis in the second movement phase of the “hip knee” task and the right latissimus dorsi during the first movement phase of the “hip twist” task. This was accompanied by a significant interactional effect (p<0.05) between load and sagittal centre of pressure movement attributed to load, in both movement phases of all tasks investigated. From this research it can be proposed that guidelines may underestimate risk and subsequently under predict the strain in tasks performed with greater external loads as well as tasks which require a greater degree of trunk motion. Therefore, this study illustrates the importance of the consideration of the muscle activity necessary to maintain postural equilibrium in overall load analyses.
- Full Text:
- Date Issued: 2010
The relationship between nasal turbinate structure and the ecological attributes of ungulates
- Authors: Kietzmann, Michelle Ann
- Date: 2010
- Subjects: Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10682 , http://hdl.handle.net/10948/1524 , Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Description: The nasal turbinates of ungulates are complex bony scrolls within the nasal cavity. These intricate bony plates, covered by moist epithelium, provide a large surface area that facilitates a countercurrent exchange of both water and heat between turbinal lining and respired air. Given their functional importance, maxilloturbinate size and structural dimensions may vary among species of different body sizes, activity levels and from different habitats, and may also serve as a predictor of the ability of the species to cope with high temperatures or limiting water resources. This is the first study to measure nasal turbinate surface area in ungulates using high-resolution computed tomography (CT) scanning. Heads of eleven South African bovid species and one European bovid species were successfully scanned and surface area measurements made using stereological techniques. These species included Cape grysbok, springbuck, bushbuck, blesbok, impala, mountain reedbuck, fallow deer, kudu, nyala, gemsbok and blue wildebeest; and represent species of different body sizes, from a range of habitats and with different water dependencies and predator avoidance strategies. The total maxilloturbinate surface area increased with body size for all study species. The surface areas of the nasal turbinates varied rostrocaudally, with the highest surface area occurring approximately midway along the length of the maxilloturbinate bones. The Cape grysbok stood out as having a nasal turbinate surface area of 12.77 cm2/kg, which was lower than the observed trend, the reason for this not being clear from these data. Phylogenetic independent analyses showed that log body mass and water dependence had a significant effect on nasal turbinate surface area, with habitat, distributional range and anti-predator behaviour having no effect. Subsequent phylogenetic species comparisons showed that structural variations in nasal turbinate surface area were phylogeny based due to the close genetic relatedness of the study species, and not associated with any environmental factors. The environmentally linked results for water dependency need further investigation in future studies of larger sample sizes and a broader range of species. Changes in climatic conditions may impact on a species‟ activity patterns, with individuals being forced to make behavioural modifications rather than physiological or anatomical adjustments. However, there is no clear evidence to indicate large differences in nasal turbinate surface area in relation to water dependence. This subsequently rules out the use of nasal turbinate surface area as a predictor to which and how ungulate species will respond to increasing global temperatures.
- Full Text:
- Date Issued: 2010
- Authors: Kietzmann, Michelle Ann
- Date: 2010
- Subjects: Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10682 , http://hdl.handle.net/10948/1524 , Ungulates -- Ecology , Nasal fossa , Tomography -- Data processing
- Description: The nasal turbinates of ungulates are complex bony scrolls within the nasal cavity. These intricate bony plates, covered by moist epithelium, provide a large surface area that facilitates a countercurrent exchange of both water and heat between turbinal lining and respired air. Given their functional importance, maxilloturbinate size and structural dimensions may vary among species of different body sizes, activity levels and from different habitats, and may also serve as a predictor of the ability of the species to cope with high temperatures or limiting water resources. This is the first study to measure nasal turbinate surface area in ungulates using high-resolution computed tomography (CT) scanning. Heads of eleven South African bovid species and one European bovid species were successfully scanned and surface area measurements made using stereological techniques. These species included Cape grysbok, springbuck, bushbuck, blesbok, impala, mountain reedbuck, fallow deer, kudu, nyala, gemsbok and blue wildebeest; and represent species of different body sizes, from a range of habitats and with different water dependencies and predator avoidance strategies. The total maxilloturbinate surface area increased with body size for all study species. The surface areas of the nasal turbinates varied rostrocaudally, with the highest surface area occurring approximately midway along the length of the maxilloturbinate bones. The Cape grysbok stood out as having a nasal turbinate surface area of 12.77 cm2/kg, which was lower than the observed trend, the reason for this not being clear from these data. Phylogenetic independent analyses showed that log body mass and water dependence had a significant effect on nasal turbinate surface area, with habitat, distributional range and anti-predator behaviour having no effect. Subsequent phylogenetic species comparisons showed that structural variations in nasal turbinate surface area were phylogeny based due to the close genetic relatedness of the study species, and not associated with any environmental factors. The environmentally linked results for water dependency need further investigation in future studies of larger sample sizes and a broader range of species. Changes in climatic conditions may impact on a species‟ activity patterns, with individuals being forced to make behavioural modifications rather than physiological or anatomical adjustments. However, there is no clear evidence to indicate large differences in nasal turbinate surface area in relation to water dependence. This subsequently rules out the use of nasal turbinate surface area as a predictor to which and how ungulate species will respond to increasing global temperatures.
- Full Text:
- Date Issued: 2010
The taxonomy, life-history and population dynamics of blacktail, Diplodus Capensis (Perciformes: Sparidae), in southern Angola
- Authors: Richardson, Timothy John
- Date: 2010
- Subjects: Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5324 , http://hdl.handle.net/10962/d1005170 , Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Description: The blacktail, Diplodus capensis, is an inshore sparid fish distributed from Mozambique to Angola. This species forms an important component of coastal fisheries within its distribution, one being the subsistence handline fishery in southern Angola. With this fishery being critically important to the livelihoods of local communities, a biological study and stock assessment was conducted to provide information for the management of this species in southern Angola. However, with molecular evidence suggesting that the Benguela current may have separated the southern African populations of many inshore fish species over two million years ago, a morphological, taxonomic analysis was considered necessary to first investigate whether there was evidence for allopatry in this species. A total of 46 morphometric measurements and 18 counts were carried out on specimens collected from various locations in southern Angola and South Africa. Results were analysed using multi-dimensional scaling (MDS) and the significance of clusters was tested using analysis of similarities (ANOSIM). Biological samples of D. capensis were collected monthly from an unexploited area from April 2008 to March 2009. Additional biological samples were collected from the subsistence fishers in an exploited area during May, June and December 2009. Standard biological laboratory techniques were employed for the lifehistory comparison between the exploited and unexploited area. A per-recruit analysis was conducted using the life-history parameters from both areas in order to assess the current status of the subsistence fishery and to investigate the potential short-falls of the per-recruit assessment approach. The morphometric comparison showed that there was not sufficient evidence for speciation between the southern Angolan and South African populations of D. capensis. There was, however, sufficient morphological evidence to suggest that these populations are separate stocks. This indicated that the existing reference points on which the management of the South African population is based are unsuitable for the Angolan population. Diplodus capensis in southern Angola is omnivorous, feeding predominantly on algae, barnacles and mussels. An ontogenetic shift from algae to barnacles and mussels was correlated with allometric growth patterns in their feeding apparatus. This species is a rudimentary hermaphrodite in southern Angola with peak spawning in June and July. The overall sex ratio (M: F) was 1: 4.7 in the unexploited area and 50% maturity was attained at 149.5mm FL and five years. Diplodus capensis in southern Angola exhibits very slow growth with the maximum age observed being 31 years (validated using mark recapture of chemically injected fish). Females [L(t) = 419.5(1-e⁻°·°⁴⁵⁽t⁻³·⁴ ⁾)] grew significantly faster (LRT, p < 0.05) than males [L(t) = 297.4(1-e⁻°·°⁷⁷⁽t⁻²·⁷⁾)], and females dominated the larger size classes and older age classes. In the exploited area, the length and age frequencies were severely truncated, the maximum observed age was greatly reduced (17 years) and the sex ratio was less female biased at 1: 2.2. Although there was no evidence for a physiological response to exploitation through alterations in growth or size/age at sexual maturity between the two areas, there was an increase in the proportion of small females in the exploited area, which may have been a compensatory response for the loss of large females. A combination of an underestimate of longevity, different estimates of the Von Bertalanffy growth parameters and overestimates of the natural mortality rate in the exploited population resulted in a 92% underestimate of the pristine spawner biomass-per-recruit (SBR) value. An assessment based on the actual pristine SBR estimate from the unexploited area revealed that the subsistence fishery had actually reduced D. capensis to 20% of its pristine SBR levels and highlighted the value of pre-exploitation life-history information for the application of per-recruit models. This study has shown that D. capensis in southern Angola displays life-history characteristics that render it susceptible to overexploitation, even at low levels of fishing pressure. The current lack of infrastructure and enforcement capacity in the fisheries department of Angola renders traditional linefish regulatory tools, such as size limits, bag limits and closed seasons, inappropriate. Therefore, suitably designed marine protected areas are recommended as the best management option for this species.
- Full Text:
- Date Issued: 2010
- Authors: Richardson, Timothy John
- Date: 2010
- Subjects: Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5324 , http://hdl.handle.net/10962/d1005170 , Diplodus -- Angola , Perciformes -- Angola , Sparidae -- Angola , Fish populations -- Angola , Fishes -- Classification -- Angola , Fisheries -- Angola
- Description: The blacktail, Diplodus capensis, is an inshore sparid fish distributed from Mozambique to Angola. This species forms an important component of coastal fisheries within its distribution, one being the subsistence handline fishery in southern Angola. With this fishery being critically important to the livelihoods of local communities, a biological study and stock assessment was conducted to provide information for the management of this species in southern Angola. However, with molecular evidence suggesting that the Benguela current may have separated the southern African populations of many inshore fish species over two million years ago, a morphological, taxonomic analysis was considered necessary to first investigate whether there was evidence for allopatry in this species. A total of 46 morphometric measurements and 18 counts were carried out on specimens collected from various locations in southern Angola and South Africa. Results were analysed using multi-dimensional scaling (MDS) and the significance of clusters was tested using analysis of similarities (ANOSIM). Biological samples of D. capensis were collected monthly from an unexploited area from April 2008 to March 2009. Additional biological samples were collected from the subsistence fishers in an exploited area during May, June and December 2009. Standard biological laboratory techniques were employed for the lifehistory comparison between the exploited and unexploited area. A per-recruit analysis was conducted using the life-history parameters from both areas in order to assess the current status of the subsistence fishery and to investigate the potential short-falls of the per-recruit assessment approach. The morphometric comparison showed that there was not sufficient evidence for speciation between the southern Angolan and South African populations of D. capensis. There was, however, sufficient morphological evidence to suggest that these populations are separate stocks. This indicated that the existing reference points on which the management of the South African population is based are unsuitable for the Angolan population. Diplodus capensis in southern Angola is omnivorous, feeding predominantly on algae, barnacles and mussels. An ontogenetic shift from algae to barnacles and mussels was correlated with allometric growth patterns in their feeding apparatus. This species is a rudimentary hermaphrodite in southern Angola with peak spawning in June and July. The overall sex ratio (M: F) was 1: 4.7 in the unexploited area and 50% maturity was attained at 149.5mm FL and five years. Diplodus capensis in southern Angola exhibits very slow growth with the maximum age observed being 31 years (validated using mark recapture of chemically injected fish). Females [L(t) = 419.5(1-e⁻°·°⁴⁵⁽t⁻³·⁴ ⁾)] grew significantly faster (LRT, p < 0.05) than males [L(t) = 297.4(1-e⁻°·°⁷⁷⁽t⁻²·⁷⁾)], and females dominated the larger size classes and older age classes. In the exploited area, the length and age frequencies were severely truncated, the maximum observed age was greatly reduced (17 years) and the sex ratio was less female biased at 1: 2.2. Although there was no evidence for a physiological response to exploitation through alterations in growth or size/age at sexual maturity between the two areas, there was an increase in the proportion of small females in the exploited area, which may have been a compensatory response for the loss of large females. A combination of an underestimate of longevity, different estimates of the Von Bertalanffy growth parameters and overestimates of the natural mortality rate in the exploited population resulted in a 92% underestimate of the pristine spawner biomass-per-recruit (SBR) value. An assessment based on the actual pristine SBR estimate from the unexploited area revealed that the subsistence fishery had actually reduced D. capensis to 20% of its pristine SBR levels and highlighted the value of pre-exploitation life-history information for the application of per-recruit models. This study has shown that D. capensis in southern Angola displays life-history characteristics that render it susceptible to overexploitation, even at low levels of fishing pressure. The current lack of infrastructure and enforcement capacity in the fisheries department of Angola renders traditional linefish regulatory tools, such as size limits, bag limits and closed seasons, inappropriate. Therefore, suitably designed marine protected areas are recommended as the best management option for this species.
- Full Text:
- Date Issued: 2010
The ultrastructure and histology of the defensive epidermal glands of some marine pulmonates
- Authors: Pinchuck, Shirley Clare
- Date: 2010
- Subjects: Snails -- Histology , Snails -- Physiology , Snails -- Cytology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5793 , http://hdl.handle.net/10962/d1005481 , Snails -- Histology , Snails -- Physiology , Snails -- Cytology
- Description: Histology and electron microscopy were used to describe and compare the structure of the dorso-lateral pedal defensive glands of three species of marine Basommatophora, Siphonaria capensis, S. serrata and S. gigas. All three species possessed multi-cellular glands that were larger and most abundant in S. capensis. In S. capensis and S. serrata, defensive glands were composed of two types (type I and II) of large secretory cells filled with product and some irregularly shaped support cells that surrounded a central lumen. The product of both cell types was produced by organelles confined to the bases of the cells. The entire gland was surrounded by a well developed layer of smooth muscle and collagen. Type I cells stained positively for neutral and sulphated mucins, and at the transmission electron microscope level the product had a reticulated appearance. By contrast type II gland cells stained very positively for acidic mucins and the secretory product was formed as large granular vesicles. The product from both types of cell, which appeared to be secreted by holocrine secretion, mixed in the lumen of the duct. Individuals of Siphonaria gigas had two types of lateral pedal glands, a large multi-cellular type and a tubular unicellular gland. The multi-cellular glands, which were surrounded by poorly developed muscle, contained one type of gland cell that stained for neutral and sulphated mucins only, as well as some support cells. The tubular glands contained a heterogeneous product that stained very positively for neutral and sulphated mucins. In addition two species of shell-less marine Systellommatophorans, Onchidella capensis and O. hildae, were examined. Onchidellids also posses large marginal, multi-cellular, epidermal glands that produce a repugnatorial secretion. Like the multi-cellular epidermal glands of siphonariids, those of onchidellids are surrounded by layers of smooth muscle. The muscular capsule was particularly well developed in both species of onchidellid, but more so in O. hildae. In addition, this study has shown that unlike siphonariids, muscle fibres run between the gland cells of O. capensis and O. hildae. Unlike siphonariids, onchidellids have a layer of epithelial cells lining the lumen of the gland. The well developed muscle layer and the strands of muscle running between the different gland cells indicates that the glands can be constricted to forcibly propel their secretions along the length of the duct and away from the body of the animal. Based on their product, glands of O. capensis were comprised of five different types of secretory cell and O. hildae only four. Histological and histochemical staining of the glands of showed that the secretory product is largely made up of acidic mucopolysaccharides and neutral and sulphated mucins. A single species from the order Eupulmonata, Trimusculus costatus, was examined and the glands were very different to the species from the siphonariids and onchidellids. Trimusculus costatus does not have large multi-cellular glands encapsulated in a well developed muscle layer, but based on their cell contents, three different types of large unicellular gland cell can be recognised. The glands of T. costatus gave positive results for acid, neutral and sulphated mucins, but negative results for carboxylated mucin. It is possible that the mucous secreted by T. costatus is also an anti-bacterial agent and whilst not totally eliminating bacteria may prevent the accumulation of epibionts on these sedentary limpets. The acidic or sulphated nature of the secretions may help in this role. The defensive mucous secretions of Siphonaria and Onchidella contain polypropionate derivatives, whilst the active ingredients of Trimusculus mucus have been identified as labdane diterpenes, similar to those produced by opisthobranchs. The structure of the glands thought to produce these repungnatorial secretions is very different, with the glands of T. costatus resembling those of the opisthobranchs.
- Full Text:
- Date Issued: 2010
- Authors: Pinchuck, Shirley Clare
- Date: 2010
- Subjects: Snails -- Histology , Snails -- Physiology , Snails -- Cytology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5793 , http://hdl.handle.net/10962/d1005481 , Snails -- Histology , Snails -- Physiology , Snails -- Cytology
- Description: Histology and electron microscopy were used to describe and compare the structure of the dorso-lateral pedal defensive glands of three species of marine Basommatophora, Siphonaria capensis, S. serrata and S. gigas. All three species possessed multi-cellular glands that were larger and most abundant in S. capensis. In S. capensis and S. serrata, defensive glands were composed of two types (type I and II) of large secretory cells filled with product and some irregularly shaped support cells that surrounded a central lumen. The product of both cell types was produced by organelles confined to the bases of the cells. The entire gland was surrounded by a well developed layer of smooth muscle and collagen. Type I cells stained positively for neutral and sulphated mucins, and at the transmission electron microscope level the product had a reticulated appearance. By contrast type II gland cells stained very positively for acidic mucins and the secretory product was formed as large granular vesicles. The product from both types of cell, which appeared to be secreted by holocrine secretion, mixed in the lumen of the duct. Individuals of Siphonaria gigas had two types of lateral pedal glands, a large multi-cellular type and a tubular unicellular gland. The multi-cellular glands, which were surrounded by poorly developed muscle, contained one type of gland cell that stained for neutral and sulphated mucins only, as well as some support cells. The tubular glands contained a heterogeneous product that stained very positively for neutral and sulphated mucins. In addition two species of shell-less marine Systellommatophorans, Onchidella capensis and O. hildae, were examined. Onchidellids also posses large marginal, multi-cellular, epidermal glands that produce a repugnatorial secretion. Like the multi-cellular epidermal glands of siphonariids, those of onchidellids are surrounded by layers of smooth muscle. The muscular capsule was particularly well developed in both species of onchidellid, but more so in O. hildae. In addition, this study has shown that unlike siphonariids, muscle fibres run between the gland cells of O. capensis and O. hildae. Unlike siphonariids, onchidellids have a layer of epithelial cells lining the lumen of the gland. The well developed muscle layer and the strands of muscle running between the different gland cells indicates that the glands can be constricted to forcibly propel their secretions along the length of the duct and away from the body of the animal. Based on their product, glands of O. capensis were comprised of five different types of secretory cell and O. hildae only four. Histological and histochemical staining of the glands of showed that the secretory product is largely made up of acidic mucopolysaccharides and neutral and sulphated mucins. A single species from the order Eupulmonata, Trimusculus costatus, was examined and the glands were very different to the species from the siphonariids and onchidellids. Trimusculus costatus does not have large multi-cellular glands encapsulated in a well developed muscle layer, but based on their cell contents, three different types of large unicellular gland cell can be recognised. The glands of T. costatus gave positive results for acid, neutral and sulphated mucins, but negative results for carboxylated mucin. It is possible that the mucous secreted by T. costatus is also an anti-bacterial agent and whilst not totally eliminating bacteria may prevent the accumulation of epibionts on these sedentary limpets. The acidic or sulphated nature of the secretions may help in this role. The defensive mucous secretions of Siphonaria and Onchidella contain polypropionate derivatives, whilst the active ingredients of Trimusculus mucus have been identified as labdane diterpenes, similar to those produced by opisthobranchs. The structure of the glands thought to produce these repungnatorial secretions is very different, with the glands of T. costatus resembling those of the opisthobranchs.
- Full Text:
- Date Issued: 2010
Time course of performance changes and fatigue markers during training for the ironman triathlon
- Authors: Joiner, Alexander Jason
- Date: 2010
- Subjects: Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5133 , http://hdl.handle.net/10962/d1005212 , Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Description:
Suboptimal preparation for the Ironman triathlon can have detrimental effects on mental and physical condition. The purpose of this longitudinal investigation was to examine the relationship between a number of performance changes and fatigue markers during training for an Ironman as well as immediately after the event, in an attempt to better understand the effects of ultraendurance training. Eighteen athletes training for the Ironman; South Africa, 2009 were recruited for the study. Over the 6 month data collection period body mass, training load (TRIMP and Session x RPE methods), physiological responses (waking heart rate, postural dizziness, sleep ratings), changes in psychological state (profile of mood states - POMS), reported immunological responses (symptoms of illness), biochemical changes (salivary cortisol and alpha amylase) and performance (8 km submaximal running time trial (TT) and race day performance) were measured. These responses were compared to a control sample (n=15). Results show a significant increase (p<0.05) in training load (3899.4 ± 2517.8) four weeks prior to the event. Fatigue scores significantly increased (p<0.05) concurrently with this significant increase (p<0.05) in training. TT performance did not significantly (p<0.05) alter during the time course of training. It was however strongly correlated to training load (R2=0.85) and modestly related to race performance (R2=0.65). The signs and symptoms of upper respiratory tract infections (URTI) were prevalent during the training period, decreasing during the taper and race period. Large standard deviations were found within the majority of the responses. During the final two weeks of preparation, tension scores were significantly increased (p<0.05) while training load significantly decreased (p<0.05) during the final week of preparation. Cortisol increased significantly (p<0.05) immediately post race (0.507±0.15
- Full Text:
- Date Issued: 2010
- Authors: Joiner, Alexander Jason
- Date: 2010
- Subjects: Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5133 , http://hdl.handle.net/10962/d1005212 , Ironman triathlons -- Training , Physical education and training -- Physiological aspects , Endurance sports -- Training , Sports -- Physiological aspects , Fatigue
- Description:
Suboptimal preparation for the Ironman triathlon can have detrimental effects on mental and physical condition. The purpose of this longitudinal investigation was to examine the relationship between a number of performance changes and fatigue markers during training for an Ironman as well as immediately after the event, in an attempt to better understand the effects of ultraendurance training. Eighteen athletes training for the Ironman; South Africa, 2009 were recruited for the study. Over the 6 month data collection period body mass, training load (TRIMP and Session x RPE methods), physiological responses (waking heart rate, postural dizziness, sleep ratings), changes in psychological state (profile of mood states - POMS), reported immunological responses (symptoms of illness), biochemical changes (salivary cortisol and alpha amylase) and performance (8 km submaximal running time trial (TT) and race day performance) were measured. These responses were compared to a control sample (n=15). Results show a significant increase (p<0.05) in training load (3899.4 ± 2517.8) four weeks prior to the event. Fatigue scores significantly increased (p<0.05) concurrently with this significant increase (p<0.05) in training. TT performance did not significantly (p<0.05) alter during the time course of training. It was however strongly correlated to training load (R2=0.85) and modestly related to race performance (R2=0.65). The signs and symptoms of upper respiratory tract infections (URTI) were prevalent during the training period, decreasing during the taper and race period. Large standard deviations were found within the majority of the responses. During the final two weeks of preparation, tension scores were significantly increased (p<0.05) while training load significantly decreased (p<0.05) during the final week of preparation. Cortisol increased significantly (p<0.05) immediately post race (0.507±0.15
- Full Text:
- Date Issued: 2010
Validation of high frequency propagation prediction models over Africa
- Authors: Tshisaphungo, Mpho
- Date: 2010
- Subjects: Ionospheric radio wave propagation , Ionospheric radio wave propagation -- Forecasting , Radio meteorology , Radio wave propagation -- Africa , Ionosphere -- Africa -- Radio waves , Atmospheric physics -- Africa , Shortwave radio -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5553 , http://hdl.handle.net/10962/d1015239
- Description: The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.
- Full Text:
- Date Issued: 2010
- Authors: Tshisaphungo, Mpho
- Date: 2010
- Subjects: Ionospheric radio wave propagation , Ionospheric radio wave propagation -- Forecasting , Radio meteorology , Radio wave propagation -- Africa , Ionosphere -- Africa -- Radio waves , Atmospheric physics -- Africa , Shortwave radio -- Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5553 , http://hdl.handle.net/10962/d1015239
- Description: The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.
- Full Text:
- Date Issued: 2010
Visual based finger interactions for mobile phones
- Authors: Kerr, Simon
- Date: 2010 , 2010-03-15
- Subjects: User interfaces (Computer systems) , Mobile communication systems -- Design and construction , Cell phones -- Software , Mobile communication systems -- Technological innovations , Information display systems , Cell phones -- Technological innovations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4652 , http://hdl.handle.net/10962/d1006621 , User interfaces (Computer systems) , Mobile communication systems -- Design and construction , Cell phones -- Software , Mobile communication systems -- Technological innovations , Information display systems , Cell phones -- Technological innovations
- Description: Vision based technology such as motion detection has long been limited to the domain of powerful processor intensive systems such as desktop PCs and specialist hardware solutions. With the advent of much faster mobile phone processors and memory, a plethora of feature rich software and hardware is being deployed onto the mobile platform, most notably onto high powered devices called smart phones. Interaction interfaces such as touchscreens allow for improved usability but obscure the phone’s screen. Since the majority of smart phones are equipped with cameras, it has become feasible to combine their powerful processors, large memory capacity and the camera to support new ways of interacting with the phone which do not obscure the screen. However, it is not clear whether or not these processor intensive visual interactions can in fact be run at an acceptable speed on current mobile handsets or whether they will offer the user a better experience than the current number pad and direction keys present on the majority of mobile phones. A vision based finger interaction technique is proposed which uses the back of device camera to track the user’s finger. This allows the user to interact with the mobile phone with mouse based movements, gestures and steering based interactions. A simple colour thresholding algorithm was implemented in Java, Python and C++. Various benchmarks and tests conducted on a Nokia N95 smart phone revealed that on current hardware and with current programming environments only native C++ yields results plausible for real time interactions (a key requirement for vision based interactions). It is also shown that different lighting levels and background environments affects the accuracy of the system with background and finger contrast playing a large role. Finally a user study was conducted to ascertain the overall user’s satisfaction between keypad interactions and the finger interaction techniques concluding that the new finger interaction technique is well suited to steering based interactions and in time, mouse style movements. Simple navigation is better suited to the directional keypad.
- Full Text:
- Date Issued: 2010
- Authors: Kerr, Simon
- Date: 2010 , 2010-03-15
- Subjects: User interfaces (Computer systems) , Mobile communication systems -- Design and construction , Cell phones -- Software , Mobile communication systems -- Technological innovations , Information display systems , Cell phones -- Technological innovations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4652 , http://hdl.handle.net/10962/d1006621 , User interfaces (Computer systems) , Mobile communication systems -- Design and construction , Cell phones -- Software , Mobile communication systems -- Technological innovations , Information display systems , Cell phones -- Technological innovations
- Description: Vision based technology such as motion detection has long been limited to the domain of powerful processor intensive systems such as desktop PCs and specialist hardware solutions. With the advent of much faster mobile phone processors and memory, a plethora of feature rich software and hardware is being deployed onto the mobile platform, most notably onto high powered devices called smart phones. Interaction interfaces such as touchscreens allow for improved usability but obscure the phone’s screen. Since the majority of smart phones are equipped with cameras, it has become feasible to combine their powerful processors, large memory capacity and the camera to support new ways of interacting with the phone which do not obscure the screen. However, it is not clear whether or not these processor intensive visual interactions can in fact be run at an acceptable speed on current mobile handsets or whether they will offer the user a better experience than the current number pad and direction keys present on the majority of mobile phones. A vision based finger interaction technique is proposed which uses the back of device camera to track the user’s finger. This allows the user to interact with the mobile phone with mouse based movements, gestures and steering based interactions. A simple colour thresholding algorithm was implemented in Java, Python and C++. Various benchmarks and tests conducted on a Nokia N95 smart phone revealed that on current hardware and with current programming environments only native C++ yields results plausible for real time interactions (a key requirement for vision based interactions). It is also shown that different lighting levels and background environments affects the accuracy of the system with background and finger contrast playing a large role. Finally a user study was conducted to ascertain the overall user’s satisfaction between keypad interactions and the finger interaction techniques concluding that the new finger interaction technique is well suited to steering based interactions and in time, mouse style movements. Simple navigation is better suited to the directional keypad.
- Full Text:
- Date Issued: 2010
White rhinoceros populations in the Eastern Cape: distribution, performance and diet
- Authors: Kraai, Manqhai
- Date: 2010
- Subjects: Rhinoceroses -- South Africa -- Eastern Cape , Rhinoceroses -- Habitat -- South Africa -- Eastern Cape , Rhinoceroses -- Behavior -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10692 , http://hdl.handle.net/10948/1297 , Rhinoceroses -- South Africa -- Eastern Cape , Rhinoceroses -- Habitat -- South Africa -- Eastern Cape , Rhinoceroses -- Behavior -- South Africa -- Eastern Cape
- Description: White rhino populations did not occur historically in the Eastern Cape, South Africa (Skead 2007). They have, however, been introduced into a number of reserves within the Eastern Cape for reasons such as conservation, ecotourism and hunting. Based on the literature on the species, it was hypothesized that white rhinoceros would have been introduced in grass-rich habitats, as they are bulk grazers. White rhinoceros populations were further assessed in terms of population establishment by outlining their distribution and performance since introductions and this was done by extracting intercalving intervals from the literature of native populations and comparing such to the Eastern Cape intercalving intervals, extracted from data obtained from landowners. Finally, the diet of white rhinoceros was quantified, in order to identify plant species potentially at risk from white rhino herbivory using Shamwari Private Game Reserve as a study site. The distribution of white rhino in the Eastern Cape varies in terms of habitat and vegetation types. The majority (62%) of white rhino are located in grass-poor habitats and are primarily there for ecotourism purposes with only a small percentage kept for conservation purposes in the state reserves. Limited data for intercalving intervals of the white rhino in Eastern Cape are comparable to those of populations in the natural range. The ex situ conservation of white rhino in the Eastern Cape proved to be a success as population numbers have increased markedly since the first survey was conducted (Buijs 1999). The diet section of this study showed that white rhino are highly selective grazers even in a grass-limiting habitat which is dominated by browse. Twenty-five principal dietary items were identified in their diet, with only six being preferred in autumn. These are thus the plant species that could be the most vulnerable to white rhino herbivory. Supplementary food provision plays a big part of the feeding scheme of white rhino in Shamwari Private Game Reserve during the winter season, revealing the little confidence that the management has on natural resource availability to the animals at this time. These findings support the value of the Eastern Cape for ex situ conservation of white rhino, and highlight plant species potentially at risk. There is a need for further research on the population performance of these animals, and the plants identified here need to be monitored to assess white rhino impact on the vegetation
- Full Text:
- Date Issued: 2010
- Authors: Kraai, Manqhai
- Date: 2010
- Subjects: Rhinoceroses -- South Africa -- Eastern Cape , Rhinoceroses -- Habitat -- South Africa -- Eastern Cape , Rhinoceroses -- Behavior -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10692 , http://hdl.handle.net/10948/1297 , Rhinoceroses -- South Africa -- Eastern Cape , Rhinoceroses -- Habitat -- South Africa -- Eastern Cape , Rhinoceroses -- Behavior -- South Africa -- Eastern Cape
- Description: White rhino populations did not occur historically in the Eastern Cape, South Africa (Skead 2007). They have, however, been introduced into a number of reserves within the Eastern Cape for reasons such as conservation, ecotourism and hunting. Based on the literature on the species, it was hypothesized that white rhinoceros would have been introduced in grass-rich habitats, as they are bulk grazers. White rhinoceros populations were further assessed in terms of population establishment by outlining their distribution and performance since introductions and this was done by extracting intercalving intervals from the literature of native populations and comparing such to the Eastern Cape intercalving intervals, extracted from data obtained from landowners. Finally, the diet of white rhinoceros was quantified, in order to identify plant species potentially at risk from white rhino herbivory using Shamwari Private Game Reserve as a study site. The distribution of white rhino in the Eastern Cape varies in terms of habitat and vegetation types. The majority (62%) of white rhino are located in grass-poor habitats and are primarily there for ecotourism purposes with only a small percentage kept for conservation purposes in the state reserves. Limited data for intercalving intervals of the white rhino in Eastern Cape are comparable to those of populations in the natural range. The ex situ conservation of white rhino in the Eastern Cape proved to be a success as population numbers have increased markedly since the first survey was conducted (Buijs 1999). The diet section of this study showed that white rhino are highly selective grazers even in a grass-limiting habitat which is dominated by browse. Twenty-five principal dietary items were identified in their diet, with only six being preferred in autumn. These are thus the plant species that could be the most vulnerable to white rhino herbivory. Supplementary food provision plays a big part of the feeding scheme of white rhino in Shamwari Private Game Reserve during the winter season, revealing the little confidence that the management has on natural resource availability to the animals at this time. These findings support the value of the Eastern Cape for ex situ conservation of white rhino, and highlight plant species potentially at risk. There is a need for further research on the population performance of these animals, and the plants identified here need to be monitored to assess white rhino impact on the vegetation
- Full Text:
- Date Issued: 2010