Ecology and breeding biology of Lanner Falcons in the Eastern Cape Province, South Africa
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
- Authors: Stephenson, Alan
- Date: 2001
- Subjects: Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5667 , http://hdl.handle.net/10962/d1005352 , Birds -- Breeding , Birds -- South Africa -- Eastern Cape , Birds -- Ecology , Falcons -- South Africa -- Eastern Cape
- Description: Lanner Falcons Falco biarmicus are the commonest large falcons in Africa and this study in the coastal area of the Eastern Cape Province, South Africa investigated their ecology from 1984 to 2000. Lanners have recently been categorised as near-threatened and this study was initiated to ascertain if the population was stable. Breeding success of a small population, in different habitat types, was monitored intensively from 1997 to 2000, and the factors that inhibited breeding were investigated. The earliest onset of incubation was 17 July and the latest 16 August, with 2.2 young fledged per breeding pair over the four-year period. Incubation lasted 32 days and young fledged after 42-45 days. All nest sites were on cliffs with a mean height of 114 m, a mean vertical face of 53 m; 45% of the nests were in ravens’ nests. The aspect of cliff sites also influenced breeding success. Radio tracking was used to determine home range, habitat use and hunting methods, with prey species identified. Home ranges were between 66 km² and 249 km². Preferred prey was domestic chickens, pigeons and small birds during the breeding season. Foraging ranges were smaller in intensively cultivated areas with seed crops. Data obtained from ringing returns showed that no long distance movements occurred in this region, but two juveniles dispersed 152 km and 127 km. Conservation aspects with possible threats to Lanner Falcons such as poisons, electrocutions and direct persecution are discussed with some recommendations made for future research. Evidence from this study indicates that Lanner breeding success is not limited by nest site availability, but by rainfall timing and prey availability. Lanners foraged more in open areas than areas with tall vegetation, and benefited from intensive agriculture. This population appeared to be healthy and in no danger of declining in the near future.
- Full Text:
- Date Issued: 2001
Economic review 2001
- DITSELA
- Authors: DITSELA
- Date: 2001
- Subjects: Development Institute for Training,Support and Education for Labour (DITSELA)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/178602 , vital:42958
- Description: This volume of Bargaining Indicators for 2002 comes in the context of the September 11 attacks on the World Trade Center in New York, the United States’ war on Afghanistan, the collapse of the economy of Argentina and with it the biggest sovereign bankruptcy in history. All these historic events are unfolding within the first synchronised global recession since the 1970s, and have in turn deepened this recession. Within South Africa, this edition of Bargaining Indicators comes in the context of the first anti-government national strike by organised labour since the 1994 elections, and a deepening of the economic slowdown that we noted in the last edition of Bargaining Indicators. In this review of economic developments during 2001 we shine the spotlight on the global recession and its dynamics, and we look in particular at the slide of the world’s largest economy - that of the United States - into its first serious economic crisis since the end of the cold war, and we take a look at the significance of the attacks of September 11 and their aftermath on the dynamics of the global recession. We conclude our discussion of the global recession by discussing the responses of the Bush government and its allies, and at the meaning of these responses for neoliberal economic orthodoxy. We continue our analysis by looking at developments within the South African economy. In particular, we look at the implications of the global recession on the South African economy, and at how the currency crisis that has unfolded since the last quarter of 2001 forms an important moment in the dynamics of the unfolding global recession. Within this context we look at the main economic indicators (GDP; GDE; fixed capital formation, operating surpluses, wages, employment, savings and so on). Lastly, we look at the year ahead, and in particular at the implications of the global and domestic economic developments for the 2002 bargaining season.
- Full Text:
- Date Issued: 2001
- Authors: DITSELA
- Date: 2001
- Subjects: Development Institute for Training,Support and Education for Labour (DITSELA)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/178602 , vital:42958
- Description: This volume of Bargaining Indicators for 2002 comes in the context of the September 11 attacks on the World Trade Center in New York, the United States’ war on Afghanistan, the collapse of the economy of Argentina and with it the biggest sovereign bankruptcy in history. All these historic events are unfolding within the first synchronised global recession since the 1970s, and have in turn deepened this recession. Within South Africa, this edition of Bargaining Indicators comes in the context of the first anti-government national strike by organised labour since the 1994 elections, and a deepening of the economic slowdown that we noted in the last edition of Bargaining Indicators. In this review of economic developments during 2001 we shine the spotlight on the global recession and its dynamics, and we look in particular at the slide of the world’s largest economy - that of the United States - into its first serious economic crisis since the end of the cold war, and we take a look at the significance of the attacks of September 11 and their aftermath on the dynamics of the global recession. We conclude our discussion of the global recession by discussing the responses of the Bush government and its allies, and at the meaning of these responses for neoliberal economic orthodoxy. We continue our analysis by looking at developments within the South African economy. In particular, we look at the implications of the global recession on the South African economy, and at how the currency crisis that has unfolded since the last quarter of 2001 forms an important moment in the dynamics of the unfolding global recession. Within this context we look at the main economic indicators (GDP; GDE; fixed capital formation, operating surpluses, wages, employment, savings and so on). Lastly, we look at the year ahead, and in particular at the implications of the global and domestic economic developments for the 2002 bargaining season.
- Full Text:
- Date Issued: 2001
Effect of feeding regimen, temperature and stocking density on growth and survival of juvenile clownfish (Amphiprion percula)
- Authors: Johnston, Gavin
- Date: 2001
- Subjects: Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5274 , http://hdl.handle.net/10962/d1005118 , Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Description: In aquaculture, a thorough knowledge of the specific environmental requirements of a species is needed in order to maximize growth rate and survival. There is a paucity of data regarding the fundamental environmental requirements for the ongrowing phase of clownfish juveniles. This prompted the design of three experiments to determine the best feeding regimen, temperature and stocking density that maximize growth and survival of Amphiprion percula. Ration size and feeding frequency are important factors for optimizing fish growth during the juvenile grow-out phase. A factorial growth trial was conducted to determine the effect of feeding frequency and ration size on the growth of juvenile clownfish (Amphiprion percula).Three feeding frequencies (1, 2 and 3 times daily) and six rations (2,4,6,8, 10 and 12 % body weight per day (BW.day⁻¹)) were used to test the growth response over a twelve week period. Non-linear regression analysis on the effect of ration, independent of feeding frequency, on growth resulted in a significant (n = 36; r² = 68.7) parabolic model: In y = -0.0302x² + 0.5159x + -4.4377. Maximum growth corresponded to a ration of 8.5% BW.day⁻¹. Survival as a function of ration was significantly lower at 2% BW.day⁻¹. Data were further examined with Analysis of CoVariance (ANCOVA) to determine the effect of ration on growth at each feeding frequency. The combination revealed a maximum growth rate when the fish were fed a ration of 10% BW.day⁻¹ divided into two equal meals. The required ration per meal to maintain maximum growth was also found to decrease as feeding frequency increased. The determination of the best temperature for growth is of great importance due to the direct relationship between fish metabolism and temperature. The thermal preferendum of A. percula has already been estimated at 26 ± 0.7°C but it is not known whether this closely approximates the temperature for maximum growth. Sixteen tanks were set to different temperatures ranging between 21.5 and 30.2 °C. Ten juvenile A. percula were placed in each tank and growth was measured fortnightly over the course of the 10 week experiment. Non-linear regression analysis resulted in significant models for fish length (y = -0.0005x² + 0.00267x - 0.0338; r² = 56.7, n = 11) and weight (y= -0.00016x² + 0.0084x - 0.1073; r² = 61.6, n = 11). These models predict that maximum growth would be at 27.7 and 27.1 °C for length and weight, respectively. Temperature, over the range tested, had no apparent effect on survival. There was no significant difference between the temperatures for maximum growth and the preferred temperature. The effect of stocking densities ranging from 0.2 fish.L¹ to 4.0 fish.L⁻¹ on growth were used in the third experiment. The fish were fed to satiation twice daily and growth was measured fortnightly throughout the 8 week experiment. No effects on growth, survival or coefficient of variation were found within the range of stocking densities tested.
- Full Text:
- Date Issued: 2001
- Authors: Johnston, Gavin
- Date: 2001
- Subjects: Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5274 , http://hdl.handle.net/10962/d1005118 , Anemonefishes , Fishes -- Feeding and feeds , Fishes -- Growth
- Description: In aquaculture, a thorough knowledge of the specific environmental requirements of a species is needed in order to maximize growth rate and survival. There is a paucity of data regarding the fundamental environmental requirements for the ongrowing phase of clownfish juveniles. This prompted the design of three experiments to determine the best feeding regimen, temperature and stocking density that maximize growth and survival of Amphiprion percula. Ration size and feeding frequency are important factors for optimizing fish growth during the juvenile grow-out phase. A factorial growth trial was conducted to determine the effect of feeding frequency and ration size on the growth of juvenile clownfish (Amphiprion percula).Three feeding frequencies (1, 2 and 3 times daily) and six rations (2,4,6,8, 10 and 12 % body weight per day (BW.day⁻¹)) were used to test the growth response over a twelve week period. Non-linear regression analysis on the effect of ration, independent of feeding frequency, on growth resulted in a significant (n = 36; r² = 68.7) parabolic model: In y = -0.0302x² + 0.5159x + -4.4377. Maximum growth corresponded to a ration of 8.5% BW.day⁻¹. Survival as a function of ration was significantly lower at 2% BW.day⁻¹. Data were further examined with Analysis of CoVariance (ANCOVA) to determine the effect of ration on growth at each feeding frequency. The combination revealed a maximum growth rate when the fish were fed a ration of 10% BW.day⁻¹ divided into two equal meals. The required ration per meal to maintain maximum growth was also found to decrease as feeding frequency increased. The determination of the best temperature for growth is of great importance due to the direct relationship between fish metabolism and temperature. The thermal preferendum of A. percula has already been estimated at 26 ± 0.7°C but it is not known whether this closely approximates the temperature for maximum growth. Sixteen tanks were set to different temperatures ranging between 21.5 and 30.2 °C. Ten juvenile A. percula were placed in each tank and growth was measured fortnightly over the course of the 10 week experiment. Non-linear regression analysis resulted in significant models for fish length (y = -0.0005x² + 0.00267x - 0.0338; r² = 56.7, n = 11) and weight (y= -0.00016x² + 0.0084x - 0.1073; r² = 61.6, n = 11). These models predict that maximum growth would be at 27.7 and 27.1 °C for length and weight, respectively. Temperature, over the range tested, had no apparent effect on survival. There was no significant difference between the temperatures for maximum growth and the preferred temperature. The effect of stocking densities ranging from 0.2 fish.L¹ to 4.0 fish.L⁻¹ on growth were used in the third experiment. The fish were fed to satiation twice daily and growth was measured fortnightly throughout the 8 week experiment. No effects on growth, survival or coefficient of variation were found within the range of stocking densities tested.
- Full Text:
- Date Issued: 2001
Effect of high energy diets on the productive and reproductive characteristics of young Bonsmara bulls
- Labuschagné, Hermanus Stefanus
- Authors: Labuschagné, Hermanus Stefanus
- Date: 2001
- Subjects: Bonsmara cattle
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10956 , http://hdl.handle.net/10948/58 , Bonsmara cattle
- Description: A study to evaluate the effect of feeding a high energy diet on the productive and reproductive characteristics of young bulls was carried out at two different locations in the Free State Province. Two trials were conducted with the aim of evaluating the effect of level of dietary energy and age of the bulls on their productive performance and reproductive characteristics. In the first trial, two levels of energy were fed to two groups of young (343 ± days) Bonsmara bulls. The high energy group HE (n=36) bulls were Phase-C performance tested in an official performance testing center and received a high energy diet for 112 days (28 days adaptation and 84 days testing). The medium energy group ME (n=18) bulls were phase-D performance tested and received a medium-energy diet for 140 days (28 days adaptation and 112 days testing). At the end of both performance testing periods, the productive performances and reproductive characteristics of the two groups were compared. The productive parameters compared included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA) and body condition score (BCS). The reproductive parameters compared between groups included scrotal circumference (SC), semen volume (Vol) and concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), as well as percentage of total abnormalities: major (MD) and minor (MinD). The results of this trial indicated that in general, bulls from the HE group showed a significant (p<0.01) higher FLW, BCS, ADG and ADA, but a significant (p<0.01) lower volume and concentration of the ejaculate, lower mass movement and linear motility, lower percentage of live sperm and higher percentage of major defects and significantly (p<0.05) higher percentage of minor defects than the bulls from the ME group. In the second trial, 36 young Bonsmara bulls were divided into two groups according to their age at the arrival at an official Phase-C performance testing center. Older bulls (OB) (n=19) and younger bulls (YB) (n=17) all received a high energy diet for 112 days (28 days adaptation and 84 days testing). At the end of the Phase-C test the productive performances and reproductive characteristics of the two groups were compared. The animals from both groups that did not pass the Phase-C test, either due to poor performance or not meeting the breed standards, were slaughtered at an official abattoir and their scrotums and carcass characteristics were also compared. The productive parameters compared between the two groups included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA), body condition score (BCS), feed conversion ratio (FCR), carcass weight both warm (CWW) and cold (CWC), as well as dressing percentage (CDP) and fat grade (CFG). The reproductive parameters compared between the two groups included scrotal circumference (SC), total scrotal weight (TSW), scrotal fat (SF), scrotal skin weight (SSW), paired testes weight (PTW), scrotal skin thickness (SST), total testes circumference (TTC), total testicle volume (TTV), weight of epididimis / spermatic cord (WESC), volume of epididymis / spermatic cord (VESC) and the percentage of bulls with depressed spermatogenesis (PBDS), semen concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), percentage of total abnormalities: major (MD) and minor(MinD) as well as the percentage of bulls with depressed spermatogenesis (PBDS). The results of this trial indicated that in general, the younger bulls showed a significant (p<0.05) higher ADG, but a significant (p<0.05) lower ADA than the older bulls. Regarding the reproductive organs compared, the younger bulls showed a significantly (p<0.01) higher total scrotal weight, scrotal fat and scrotal skin weight and thickness. No significant differences were observed on the testicular parameters measured between the two groups. In addition, both weight (WECS) and volume (VECS) of the epididymis / spermatic cord were significantly (P<0.05) higher in the older bulls. In general, the younger group showed poorer semen characteristics. A significantly (p<0.01) lower sperm concentration and linear movement and a significantly (p<0.05) higher percentage of major defects were recorded on the younger bulls, when compared to the older bulls. About half of the bulls in each group showed clear signs of depressed spermatogenesis in their seminiferous tubules, during the histological examination of testicular tissue. The results of this study indicates that high energy diets are beneficial for the productive performance of young bulls (growth rate, BCS and carcass characteristics), but have a detrimental effect on the reproductive characteristics of young bulls. The effect of high energy diets on both the productive and reproductive performances of young beef bulls are more pronounced at a younger age. High energy diets resulted in heavier scrotums in the younger bulls when compared to the older bulls, as a direct result of a higher fat deposition in this region without any relevant effect on testicular size. No intra-testicular fat deposition was observed. The scrotal fat observed in high energy fed young bulls accumulated mainly in the neck of the scrotum, although subcutaneously. These fat deposits may impair testicular thermoregulation and negatively affect the spermatogenesis in the seminiferous tubules, reducing both sperm quantity and quality. Further studies on the effect of high energy diets on bull fertility (as well as on rams and buck) are recommended, to evaluate the extension and duration of its detrimental effects on subsequent fertility.
- Full Text:
- Date Issued: 2001
- Authors: Labuschagné, Hermanus Stefanus
- Date: 2001
- Subjects: Bonsmara cattle
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10956 , http://hdl.handle.net/10948/58 , Bonsmara cattle
- Description: A study to evaluate the effect of feeding a high energy diet on the productive and reproductive characteristics of young bulls was carried out at two different locations in the Free State Province. Two trials were conducted with the aim of evaluating the effect of level of dietary energy and age of the bulls on their productive performance and reproductive characteristics. In the first trial, two levels of energy were fed to two groups of young (343 ± days) Bonsmara bulls. The high energy group HE (n=36) bulls were Phase-C performance tested in an official performance testing center and received a high energy diet for 112 days (28 days adaptation and 84 days testing). The medium energy group ME (n=18) bulls were phase-D performance tested and received a medium-energy diet for 140 days (28 days adaptation and 112 days testing). At the end of both performance testing periods, the productive performances and reproductive characteristics of the two groups were compared. The productive parameters compared included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA) and body condition score (BCS). The reproductive parameters compared between groups included scrotal circumference (SC), semen volume (Vol) and concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), as well as percentage of total abnormalities: major (MD) and minor (MinD). The results of this trial indicated that in general, bulls from the HE group showed a significant (p<0.01) higher FLW, BCS, ADG and ADA, but a significant (p<0.01) lower volume and concentration of the ejaculate, lower mass movement and linear motility, lower percentage of live sperm and higher percentage of major defects and significantly (p<0.05) higher percentage of minor defects than the bulls from the ME group. In the second trial, 36 young Bonsmara bulls were divided into two groups according to their age at the arrival at an official Phase-C performance testing center. Older bulls (OB) (n=19) and younger bulls (YB) (n=17) all received a high energy diet for 112 days (28 days adaptation and 84 days testing). At the end of the Phase-C test the productive performances and reproductive characteristics of the two groups were compared. The animals from both groups that did not pass the Phase-C test, either due to poor performance or not meeting the breed standards, were slaughtered at an official abattoir and their scrotums and carcass characteristics were also compared. The productive parameters compared between the two groups included final live body weight (FLW), average daily gain (ADG), average daily gain per day of age (ADA), body condition score (BCS), feed conversion ratio (FCR), carcass weight both warm (CWW) and cold (CWC), as well as dressing percentage (CDP) and fat grade (CFG). The reproductive parameters compared between the two groups included scrotal circumference (SC), total scrotal weight (TSW), scrotal fat (SF), scrotal skin weight (SSW), paired testes weight (PTW), scrotal skin thickness (SST), total testes circumference (TTC), total testicle volume (TTV), weight of epididimis / spermatic cord (WESC), volume of epididymis / spermatic cord (VESC) and the percentage of bulls with depressed spermatogenesis (PBDS), semen concentration (SConO), mass movement (MV), linear motility (LM), percentage live sperm (LS), percentage of total abnormalities: major (MD) and minor(MinD) as well as the percentage of bulls with depressed spermatogenesis (PBDS). The results of this trial indicated that in general, the younger bulls showed a significant (p<0.05) higher ADG, but a significant (p<0.05) lower ADA than the older bulls. Regarding the reproductive organs compared, the younger bulls showed a significantly (p<0.01) higher total scrotal weight, scrotal fat and scrotal skin weight and thickness. No significant differences were observed on the testicular parameters measured between the two groups. In addition, both weight (WECS) and volume (VECS) of the epididymis / spermatic cord were significantly (P<0.05) higher in the older bulls. In general, the younger group showed poorer semen characteristics. A significantly (p<0.01) lower sperm concentration and linear movement and a significantly (p<0.05) higher percentage of major defects were recorded on the younger bulls, when compared to the older bulls. About half of the bulls in each group showed clear signs of depressed spermatogenesis in their seminiferous tubules, during the histological examination of testicular tissue. The results of this study indicates that high energy diets are beneficial for the productive performance of young bulls (growth rate, BCS and carcass characteristics), but have a detrimental effect on the reproductive characteristics of young bulls. The effect of high energy diets on both the productive and reproductive performances of young beef bulls are more pronounced at a younger age. High energy diets resulted in heavier scrotums in the younger bulls when compared to the older bulls, as a direct result of a higher fat deposition in this region without any relevant effect on testicular size. No intra-testicular fat deposition was observed. The scrotal fat observed in high energy fed young bulls accumulated mainly in the neck of the scrotum, although subcutaneously. These fat deposits may impair testicular thermoregulation and negatively affect the spermatogenesis in the seminiferous tubules, reducing both sperm quantity and quality. Further studies on the effect of high energy diets on bull fertility (as well as on rams and buck) are recommended, to evaluate the extension and duration of its detrimental effects on subsequent fertility.
- Full Text:
- Date Issued: 2001
Effect of oligomerization on the photochemical properties of silicon octaphenoxyphthalocyanine
- Maree, M David, Nyokong, Tebello
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291542 , vital:56885 , xlink:href="https://doi.org/10.1016/S1010-6030(01)00485-3"
- Description: The photochemical properties of silicon octaphenoxyphthalocyanines (SiOPPc) oligomerized were studied in dimethylsulfoxide (DMSO) solutions. Oligomers containing 2–5 and 9 SiOPPc rings linked with terephthalate linkages were synthesized. Singlet oxygen quantum yields were found to be in the range 0.11–0.34, and increased with the number of rings up to five rings, a decrease in the quantum yield was observed for nine rings. This is explained in terms of the high aggregation of the oligomer containing nine rings.
- Full Text:
- Date Issued: 2001
- Authors: Maree, M David , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/291542 , vital:56885 , xlink:href="https://doi.org/10.1016/S1010-6030(01)00485-3"
- Description: The photochemical properties of silicon octaphenoxyphthalocyanines (SiOPPc) oligomerized were studied in dimethylsulfoxide (DMSO) solutions. Oligomers containing 2–5 and 9 SiOPPc rings linked with terephthalate linkages were synthesized. Singlet oxygen quantum yields were found to be in the range 0.11–0.34, and increased with the number of rings up to five rings, a decrease in the quantum yield was observed for nine rings. This is explained in terms of the high aggregation of the oligomer containing nine rings.
- Full Text:
- Date Issued: 2001
Effects of discrimination on promotion of women into top managerial positions in the Eastern Cape
- Yona, Noxolo Nondwe Trewhellah
- Authors: Yona, Noxolo Nondwe Trewhellah
- Date: 2001
- Subjects: Sex discrimination against women , Businesswomen
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10902 , http://hdl.handle.net/10948/57 , Sex discrimination against women , Businesswomen
- Description: The effects of discrimination on promotion of women into top managerial positions is investigated in this study. In order to investigate these effects, the use of a questionnaire for survey was developed. The questionnaire consisted of thirty-one statements in which a response to each question contributed towards the results of this study. The literature study was used as an eye opener to the South African situation with comparison to other countries. The purpose of the empirical study was to determine the effects of discrimination especially in the Eastern Cape. The answers of the respondents were analysed and interpreted with relation to the findings from the literature study. Concluding remarks are provided which could assist firms in the private sector when faced with the challenge of the advancement of women and the implementation of the Labour policies which endorse the equal opportunity programme.
- Full Text:
- Date Issued: 2001
- Authors: Yona, Noxolo Nondwe Trewhellah
- Date: 2001
- Subjects: Sex discrimination against women , Businesswomen
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10902 , http://hdl.handle.net/10948/57 , Sex discrimination against women , Businesswomen
- Description: The effects of discrimination on promotion of women into top managerial positions is investigated in this study. In order to investigate these effects, the use of a questionnaire for survey was developed. The questionnaire consisted of thirty-one statements in which a response to each question contributed towards the results of this study. The literature study was used as an eye opener to the South African situation with comparison to other countries. The purpose of the empirical study was to determine the effects of discrimination especially in the Eastern Cape. The answers of the respondents were analysed and interpreted with relation to the findings from the literature study. Concluding remarks are provided which could assist firms in the private sector when faced with the challenge of the advancement of women and the implementation of the Labour policies which endorse the equal opportunity programme.
- Full Text:
- Date Issued: 2001
Electrooxidation of cresols on carbon electrodes modified with phthalocyaninato and octabutoxyphthalocyaninato cobalt (II) complexes
- Grootboom, Natasha, Nyokong, Tebello
- Authors: Grootboom, Natasha , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293207 , vital:57065 , xlink:href="https://doi.org/10.1016/S0003-2670(00)01351-9"
- Description: Glassy carbon electrodes (GCE) modified with cobalt(II) phthalocyanine (CoPc-GCE) and cobalt(II) octabutoxyphthalocyanine (CoOBuPc-GCE) were employed for the electrochemical analysis of ortho-, meta-, and para-cresols. The oxidation potential of p-cresol was shifted towards less positive values to a larger extent, when compared to m- and o-cresols, on CoOBuPc-GCE. However, the GCE was less stable when modified with CoOBuPc than with CoPc. This is explained using the possible differences in the orientation of the adsorbed phthalocyanine molecules on the electrode. Bulk electrolysis of p-cresol at anodic potentials (1.0 V versus Ag|AgCl) on carbon electrodes modified with CoPc resulted in the formation of radicals which coupled to form trimeric products. On unmodified carbon electrodes, coupling of the radicals resulted in dimeric products following bulk electrolysis. The products formed following bulk electrolysis were characterized by liquid chromatography coupled with mass spectrometry.
- Full Text:
- Date Issued: 2001
- Authors: Grootboom, Natasha , Nyokong, Tebello
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/293207 , vital:57065 , xlink:href="https://doi.org/10.1016/S0003-2670(00)01351-9"
- Description: Glassy carbon electrodes (GCE) modified with cobalt(II) phthalocyanine (CoPc-GCE) and cobalt(II) octabutoxyphthalocyanine (CoOBuPc-GCE) were employed for the electrochemical analysis of ortho-, meta-, and para-cresols. The oxidation potential of p-cresol was shifted towards less positive values to a larger extent, when compared to m- and o-cresols, on CoOBuPc-GCE. However, the GCE was less stable when modified with CoOBuPc than with CoPc. This is explained using the possible differences in the orientation of the adsorbed phthalocyanine molecules on the electrode. Bulk electrolysis of p-cresol at anodic potentials (1.0 V versus Ag|AgCl) on carbon electrodes modified with CoPc resulted in the formation of radicals which coupled to form trimeric products. On unmodified carbon electrodes, coupling of the radicals resulted in dimeric products following bulk electrolysis. The products formed following bulk electrolysis were characterized by liquid chromatography coupled with mass spectrometry.
- Full Text:
- Date Issued: 2001
Elements of dream interpretation: laying the foundation of a basic model for clinical practice
- Authors: Schön, Joan
- Date: 2001
- Subjects: Dream interpretation Dreams
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3050 , http://hdl.handle.net/10962/d1002559
- Description: The study addresses certain paradoxes evident in the theory and practice of dream interpretation. These relate to the considerable value afforded to dreams in psychoanalytic thinking, compared with (1) the surprising dearth of literature, research, and training on dream interpretation in clinical practice, (2) the difficulties voiced by clinicians regarding dream interpretation, and (3) the diversity of keys employed by different schools to unlock the ‘truth’ of dreams. The intention of the study is to examine these paradoxes in order to develop a model fordream interpretation which falls within the ambit of psychodynamic psychotherapy. It is argued that there have been few insights over the century to match the seminal work of Freud (1900/1976), except perhaps the work of Carl Jung. As a result of the 1914 rift between these two, Jung’s insights have been largely ignored in mainstream psychoanalytic thinking and the focus on dreams has given way to other areas of development, such as, unconscious thinking, symbol formation, and interpretation in a general sense. These, it is argued, have contributed to a more comprehensive understanding of dreams and their interpretation. Thus a model would need to consider both Freud and Jung’s work, and later salient developments. It would also need to be informed by local, contemporary practice. The method used in this thesis is one of breaking down the process of dream interpretation into component parts, in order to examine useful contributions from different sources and to compare work with dreams to work with other material. The literature review examines the major theoretical contributions in relation to four elements of dreams interpretation: the nature and function of dreams, methods of dream interpretation, the meaning of dreams, and the goals of dream interpretation. A model which accommodates diverse theories without resorting to eclecticism is then proposed. Dream interpretation is further examined in the light of a multiphase clinical study, designed to provide different perspectives on the topic. The study yielded findingscompatible with the literature reviewed, as well as certain problems in relation to the proposed model. These included shortcomings of the elements used in the literature review, particularly the sequence of these elements, and caveats about affording dreams a special focus in the consulting room. Thus a second configuration was posited, namely the idea of viewing dream-work as a triangular situation, comprising the dream, the dreamer, and the dream interpreter. The final model which is the outcome of the study provides two interrelated methods of addressing dream interpretation which accommodate the theory/practice dichotomy. In the first, the elements of dreams and their interpretation are considered sequentially. This method provides a framework for considering theoretical contributions on dreams, as well as issues of technique, without recourse to the introduction of theory in the consulting room. In the second, dream interpretation is regarded as a triangular situation, comprising the interchange between therapist and patient in relation to the patient’s dream-life. This structure accommodates the alliance which is discernible in practice and draws on Segal’s (1957/1986) notion that the process of symbol formation is a triangular situation. The value of regarding ‘dream-work’ in the consulting room as a triangular situation is threefold: (1) it is akin to symbol formation in terms of the meaning reached; (2) dreams cannot be accurately interpreted in isolation from the contributions of both therapist and patient; and (3) it provides ‘dream-work’ in practice with its own structure, highlighting a perspective that dreams are an element of clinical practice, rather than a focus, a subtext within the broader framework of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2001
- Authors: Schön, Joan
- Date: 2001
- Subjects: Dream interpretation Dreams
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3050 , http://hdl.handle.net/10962/d1002559
- Description: The study addresses certain paradoxes evident in the theory and practice of dream interpretation. These relate to the considerable value afforded to dreams in psychoanalytic thinking, compared with (1) the surprising dearth of literature, research, and training on dream interpretation in clinical practice, (2) the difficulties voiced by clinicians regarding dream interpretation, and (3) the diversity of keys employed by different schools to unlock the ‘truth’ of dreams. The intention of the study is to examine these paradoxes in order to develop a model fordream interpretation which falls within the ambit of psychodynamic psychotherapy. It is argued that there have been few insights over the century to match the seminal work of Freud (1900/1976), except perhaps the work of Carl Jung. As a result of the 1914 rift between these two, Jung’s insights have been largely ignored in mainstream psychoanalytic thinking and the focus on dreams has given way to other areas of development, such as, unconscious thinking, symbol formation, and interpretation in a general sense. These, it is argued, have contributed to a more comprehensive understanding of dreams and their interpretation. Thus a model would need to consider both Freud and Jung’s work, and later salient developments. It would also need to be informed by local, contemporary practice. The method used in this thesis is one of breaking down the process of dream interpretation into component parts, in order to examine useful contributions from different sources and to compare work with dreams to work with other material. The literature review examines the major theoretical contributions in relation to four elements of dreams interpretation: the nature and function of dreams, methods of dream interpretation, the meaning of dreams, and the goals of dream interpretation. A model which accommodates diverse theories without resorting to eclecticism is then proposed. Dream interpretation is further examined in the light of a multiphase clinical study, designed to provide different perspectives on the topic. The study yielded findingscompatible with the literature reviewed, as well as certain problems in relation to the proposed model. These included shortcomings of the elements used in the literature review, particularly the sequence of these elements, and caveats about affording dreams a special focus in the consulting room. Thus a second configuration was posited, namely the idea of viewing dream-work as a triangular situation, comprising the dream, the dreamer, and the dream interpreter. The final model which is the outcome of the study provides two interrelated methods of addressing dream interpretation which accommodate the theory/practice dichotomy. In the first, the elements of dreams and their interpretation are considered sequentially. This method provides a framework for considering theoretical contributions on dreams, as well as issues of technique, without recourse to the introduction of theory in the consulting room. In the second, dream interpretation is regarded as a triangular situation, comprising the interchange between therapist and patient in relation to the patient’s dream-life. This structure accommodates the alliance which is discernible in practice and draws on Segal’s (1957/1986) notion that the process of symbol formation is a triangular situation. The value of regarding ‘dream-work’ in the consulting room as a triangular situation is threefold: (1) it is akin to symbol formation in terms of the meaning reached; (2) dreams cannot be accurately interpreted in isolation from the contributions of both therapist and patient; and (3) it provides ‘dream-work’ in practice with its own structure, highlighting a perspective that dreams are an element of clinical practice, rather than a focus, a subtext within the broader framework of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2001
Enhancing military efficiency : a South African perspective
- Christie, Candice J, Todd, Andrew I
- Authors: Christie, Candice J , Todd, Andrew I
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6749 , http://hdl.handle.net/10962/d1009329
- Description: While extensive military research has been conducted in developed countries, very little work has been done on soldiers in industrially developing countries (IDCs). Although many aspects of marching are similar around the globe, the challenges facing soldiers in IDCs, and in particular South Africa, are unique. Since the 1990’s South Africa has seen a considerable shift in the morphological and cultural make-up of the South African National Defence Force (SANDF). The result is a mix of soldiers from a variety of ethnic backgrounds. Ethnic differences may ultimately impact performance particularly as research has postulated that Blacks and Whites may differ in body composition and body proportions. It is highly probable then that the universal recommendations of optimal marching speeds, load masses and gradients need to be modified to accommodate the diversity of soldiers which currently comprise the SANDF.
- Full Text:
- Date Issued: 2001
- Authors: Christie, Candice J , Todd, Andrew I
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6749 , http://hdl.handle.net/10962/d1009329
- Description: While extensive military research has been conducted in developed countries, very little work has been done on soldiers in industrially developing countries (IDCs). Although many aspects of marching are similar around the globe, the challenges facing soldiers in IDCs, and in particular South Africa, are unique. Since the 1990’s South Africa has seen a considerable shift in the morphological and cultural make-up of the South African National Defence Force (SANDF). The result is a mix of soldiers from a variety of ethnic backgrounds. Ethnic differences may ultimately impact performance particularly as research has postulated that Blacks and Whites may differ in body composition and body proportions. It is highly probable then that the universal recommendations of optimal marching speeds, load masses and gradients need to be modified to accommodate the diversity of soldiers which currently comprise the SANDF.
- Full Text:
- Date Issued: 2001
Environment as integrating organiser: a case study of curriculum 2005 in KwaMhlanga, South Africa
- Authors: Khumalo, Four-Ten Enock
- Date: 2001
- Subjects: Competency-based education -- Research -- South Africa Curriculum planning -- South Africa Environmental education -- Curricula -- South Africa -- Mpumalanga Environmental education -- Curricula
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1511 , http://hdl.handle.net/10962/d1003393
- Description: Curriculum 2005 is an attempt by the South African government to create and implement a strategic plan to change the formal school curriculum. The new curriculum has 'integration' as one of its focal features. This study is an investigation of the use of' environment' as an integrating' organiser' in the senior phase of Curriculum 2005 in a selection of schools in the Mpumalanga province. While the Curriculum 2005 framework encourages curriculum integration, this is an area which might be neglected during implementation, because there is so little experience among teachers of working in an 'integrated' way. Environmental education is an approach to education which requires and facilitates curriculum integration. This study has the potential to contribute to our understanding of the integration of environmental learning across the new curriculum. Questionnaires and vignettes based on document analysis, follow-up interviews and classroom observations, involving a small group of teachers, were used in conducting the study. The investigation has revealed that participating teachers show a limited understanding of the constructs 'environment' and 'phase organiser'. Teachers do not take or introduce a critical perspective on the nature and causes of environmental issues. They treat the construct 'environment' and associated issues quite superficially when working with learners. Participating teachers generally misunderstood the concept 'phase organisers' and tended to interpret it in concepts associated with the curriculum framework they were used to. Curriculum 2005 also requires teachers to take on a more active curriculum development role. This study looked at four teachers' attempts to develop learning programme units, and at the way in which two teachers implement their curriculum plans focussing on 'environment', in the classroom. It was found that participating teachers do not always follow the same sequence or steps when developing a learning programme. Learning programme units were not considered in developmental sequence, they lacked some form of continuity and links between intended learning outcomes and teaching activities were also lacking. There was inadequate integration between learning areas. Furthermore, integration between knowledge, skills, values and attitudes was also not quite clear among the teachers, and they tended to deal with environmental knowledge in a rather limited way, focussing instead on the awareness and attitudes. These findings are of concern, and they are in keeping with the Curriculum 2005 Review Report, which highlighted the danger of inadequate focus on curriculum content. On overall teachers seem to be struggling with the whole notion of 'integration', even though environment as a phase organiser is meant to assist with curriculum integration. The thesis ends with recommendations on how teachers might be assisted to achieve meaningful curriculum integration, through using learning outcomes as well as content knowledge relevant to environmental learning.
- Full Text:
- Date Issued: 2001
- Authors: Khumalo, Four-Ten Enock
- Date: 2001
- Subjects: Competency-based education -- Research -- South Africa Curriculum planning -- South Africa Environmental education -- Curricula -- South Africa -- Mpumalanga Environmental education -- Curricula
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1511 , http://hdl.handle.net/10962/d1003393
- Description: Curriculum 2005 is an attempt by the South African government to create and implement a strategic plan to change the formal school curriculum. The new curriculum has 'integration' as one of its focal features. This study is an investigation of the use of' environment' as an integrating' organiser' in the senior phase of Curriculum 2005 in a selection of schools in the Mpumalanga province. While the Curriculum 2005 framework encourages curriculum integration, this is an area which might be neglected during implementation, because there is so little experience among teachers of working in an 'integrated' way. Environmental education is an approach to education which requires and facilitates curriculum integration. This study has the potential to contribute to our understanding of the integration of environmental learning across the new curriculum. Questionnaires and vignettes based on document analysis, follow-up interviews and classroom observations, involving a small group of teachers, were used in conducting the study. The investigation has revealed that participating teachers show a limited understanding of the constructs 'environment' and 'phase organiser'. Teachers do not take or introduce a critical perspective on the nature and causes of environmental issues. They treat the construct 'environment' and associated issues quite superficially when working with learners. Participating teachers generally misunderstood the concept 'phase organisers' and tended to interpret it in concepts associated with the curriculum framework they were used to. Curriculum 2005 also requires teachers to take on a more active curriculum development role. This study looked at four teachers' attempts to develop learning programme units, and at the way in which two teachers implement their curriculum plans focussing on 'environment', in the classroom. It was found that participating teachers do not always follow the same sequence or steps when developing a learning programme. Learning programme units were not considered in developmental sequence, they lacked some form of continuity and links between intended learning outcomes and teaching activities were also lacking. There was inadequate integration between learning areas. Furthermore, integration between knowledge, skills, values and attitudes was also not quite clear among the teachers, and they tended to deal with environmental knowledge in a rather limited way, focussing instead on the awareness and attitudes. These findings are of concern, and they are in keeping with the Curriculum 2005 Review Report, which highlighted the danger of inadequate focus on curriculum content. On overall teachers seem to be struggling with the whole notion of 'integration', even though environment as a phase organiser is meant to assist with curriculum integration. The thesis ends with recommendations on how teachers might be assisted to achieve meaningful curriculum integration, through using learning outcomes as well as content knowledge relevant to environmental learning.
- Full Text:
- Date Issued: 2001
Enzymology of activated sewage sludge during anaerobic treatment of wastewaters : identification, characterisation, isolation and partial purification of proteases
- Tshivhunge, Azwiedziswi Sylvia
- Authors: Tshivhunge, Azwiedziswi Sylvia
- Date: 2001
- Subjects: Sewage sludge , Sewage sludge -- Environmental aspects , Sewage sludge digestion , Anaerobic bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4012 , http://hdl.handle.net/10962/d1004072 , Sewage sludge , Sewage sludge -- Environmental aspects , Sewage sludge digestion , Anaerobic bacteria
- Description: During anaerobic digestion bacteria inside the digester require a carbon source for their growth and metabolism, sewage sludge was used as a carbon source in this study. The COD content was used to measure the disappearance of the substrate. COD content was reduced by 48.3% and 49% in the methanogenic and sulphidogenic bioreactors, respectively, while sulphate concentration was reduced by 40%, producing 70mg/L of hydrogen sulphide as the end product over the first 5-7 days. Sulphate (which is used as a terminal electron acceptor of sulphur reducing bacteria) has little or no effect on the sulphidogenic and methanogenic proteases. Sulphite and sulphide (the intermediate and end product of sulphate reduction) increased protease activity by 20% and 40%-80%, respectively. Maximum protease activity occurred on day 21 in the methanogenic reactor and on day 9 in the sulphidogenic reactor. The absorbance, which indicates the level of amino acid increased to 2 and 9 for methanogenic and sulphidogenic bioreactors, respectively. Proteases that were active during anaerobic digestion were associated with the pellet (organic particulate matter) of the sewage. These enzymes have an optimum activity at pH 10 and at temperature of 50°C. The proteases that were active at pH 5 and 7, had optimum temperatures at 30°C and 60°C, respectively. Due to their association with organic particulate matter, these enzymes were stable at their optimum temperatures for at least five hours at their respective pH. Inhibition by PMSF, TPCK and 1.10-phenanthroline suggested that proteases inside the anaerobic digester are a mixture of cysteine, serine and metalloproteases. At pH 5, however, EDTA appeared to enhance protease activity by 368% (three-fold). Acetic acid decreased protease activity by 21%, while both propionic and butyric acid at 200 mg/L cause total inhibition of protease activity while these acids at higher pH (where they exist as their corresponding salts) exerted little effect. Copper, iron and zinc inhibited protease activity by 85% at pH 5 with concentrations ranging between 200 and 600 mg/L. On the other hand, nickel, showed an increase in protease activity of nearly 250%. At pH 7 and 10, copper had no effect on protease activity while iron, nickel and zinc inhibited these enzymes by 20-40%. Proteases at pH 7 were extracted from the pellet by sonication, releasing 50% of the total enzymes into the solution. The enzymes were precipitated by ammonium sulphate precipitation, and further purified by ion exchange chromatography and gel filtration. Ion exchange chromatography revealed that most of the enzymes that hydrolyse proteins are negatively charged while gel filtration showed that their molecular weight is approximately 500 kDa.
- Full Text:
- Date Issued: 2001
- Authors: Tshivhunge, Azwiedziswi Sylvia
- Date: 2001
- Subjects: Sewage sludge , Sewage sludge -- Environmental aspects , Sewage sludge digestion , Anaerobic bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4012 , http://hdl.handle.net/10962/d1004072 , Sewage sludge , Sewage sludge -- Environmental aspects , Sewage sludge digestion , Anaerobic bacteria
- Description: During anaerobic digestion bacteria inside the digester require a carbon source for their growth and metabolism, sewage sludge was used as a carbon source in this study. The COD content was used to measure the disappearance of the substrate. COD content was reduced by 48.3% and 49% in the methanogenic and sulphidogenic bioreactors, respectively, while sulphate concentration was reduced by 40%, producing 70mg/L of hydrogen sulphide as the end product over the first 5-7 days. Sulphate (which is used as a terminal electron acceptor of sulphur reducing bacteria) has little or no effect on the sulphidogenic and methanogenic proteases. Sulphite and sulphide (the intermediate and end product of sulphate reduction) increased protease activity by 20% and 40%-80%, respectively. Maximum protease activity occurred on day 21 in the methanogenic reactor and on day 9 in the sulphidogenic reactor. The absorbance, which indicates the level of amino acid increased to 2 and 9 for methanogenic and sulphidogenic bioreactors, respectively. Proteases that were active during anaerobic digestion were associated with the pellet (organic particulate matter) of the sewage. These enzymes have an optimum activity at pH 10 and at temperature of 50°C. The proteases that were active at pH 5 and 7, had optimum temperatures at 30°C and 60°C, respectively. Due to their association with organic particulate matter, these enzymes were stable at their optimum temperatures for at least five hours at their respective pH. Inhibition by PMSF, TPCK and 1.10-phenanthroline suggested that proteases inside the anaerobic digester are a mixture of cysteine, serine and metalloproteases. At pH 5, however, EDTA appeared to enhance protease activity by 368% (three-fold). Acetic acid decreased protease activity by 21%, while both propionic and butyric acid at 200 mg/L cause total inhibition of protease activity while these acids at higher pH (where they exist as their corresponding salts) exerted little effect. Copper, iron and zinc inhibited protease activity by 85% at pH 5 with concentrations ranging between 200 and 600 mg/L. On the other hand, nickel, showed an increase in protease activity of nearly 250%. At pH 7 and 10, copper had no effect on protease activity while iron, nickel and zinc inhibited these enzymes by 20-40%. Proteases at pH 7 were extracted from the pellet by sonication, releasing 50% of the total enzymes into the solution. The enzymes were precipitated by ammonium sulphate precipitation, and further purified by ion exchange chromatography and gel filtration. Ion exchange chromatography revealed that most of the enzymes that hydrolyse proteins are negatively charged while gel filtration showed that their molecular weight is approximately 500 kDa.
- Full Text:
- Date Issued: 2001
Evaluation of Lewis acid catalysed and other nitration strategies for the selective nitration of cresols
- Van Niekerk, Rudolf Jacob Francois
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
Expanding the capabilities of the DPS lonosonde system
- Authors: Magnus, Lindsay Gerald
- Date: 2001
- Subjects: Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5560 , http://hdl.handle.net/10962/d1018243
- Description: The Digisonde Portable Sounder (DPS) is a low power pulse ionosonde capable of recording a wealth of scientific information about the ionosphere. The routine vertical incidence mode, that produces the scaled ionospheric parameters, only records limited Doppler and no precise angle of arrival (AoA) information. The drift mode produces precise scientific information but only limited range information. This thesis explains the operation of the DPS and then examines the drift data by first showing the Doppler velocities (V*) calculated for a fixed frequency ionogram as well as the velocities calculated from an interesting ionospheric disturbance measured with a stepped frequency ionogram and second by illustrating the presence of a variation in the AoA of ionospheric echoes at sunrise. The conclusion of the thesis is that a drift vertical incidence mode be developed to allow the simultaneous measurement of the scaled ionospheric parameters and the precise AoA and full Doppler spectrum information.
- Full Text:
- Date Issued: 2001
- Authors: Magnus, Lindsay Gerald
- Date: 2001
- Subjects: Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5560 , http://hdl.handle.net/10962/d1018243
- Description: The Digisonde Portable Sounder (DPS) is a low power pulse ionosonde capable of recording a wealth of scientific information about the ionosphere. The routine vertical incidence mode, that produces the scaled ionospheric parameters, only records limited Doppler and no precise angle of arrival (AoA) information. The drift mode produces precise scientific information but only limited range information. This thesis explains the operation of the DPS and then examines the drift data by first showing the Doppler velocities (V*) calculated for a fixed frequency ionogram as well as the velocities calculated from an interesting ionospheric disturbance measured with a stepped frequency ionogram and second by illustrating the presence of a variation in the AoA of ionospheric echoes at sunrise. The conclusion of the thesis is that a drift vertical incidence mode be developed to allow the simultaneous measurement of the scaled ionospheric parameters and the precise AoA and full Doppler spectrum information.
- Full Text:
- Date Issued: 2001
Experiences in porting a virtual reality system to Java
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433157 , vital:72947 , https://doi.org/10.1145/513867.513875
- Description: Practical experience in porting a large virtual reality system from C/C++ to Java indicates that porting this type of real-time application is both feasible, and has several merits. The ability to transfer objects in space and time allows useful facilities such as distributed agent support and persistence to be added. Reflection and type comparisons allow flexible manipulations of objects of different types at run-time. Native calls and native code compilation reduce or remove the overhead of interpreting code.Problems encountered include difficulty in achieving cross-platform code portability, limitations of the networking libraries in Java, and clumsy coding practices forced by the language.
- Full Text:
- Date Issued: 2001
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433157 , vital:72947 , https://doi.org/10.1145/513867.513875
- Description: Practical experience in porting a large virtual reality system from C/C++ to Java indicates that porting this type of real-time application is both feasible, and has several merits. The ability to transfer objects in space and time allows useful facilities such as distributed agent support and persistence to be added. Reflection and type comparisons allow flexible manipulations of objects of different types at run-time. Native calls and native code compilation reduce or remove the overhead of interpreting code.Problems encountered include difficulty in achieving cross-platform code portability, limitations of the networking libraries in Java, and clumsy coding practices forced by the language.
- Full Text:
- Date Issued: 2001
Exploring job satisfaction amongst government social workers in East London
- Authors: Sela, Michelle
- Date: 2001
- Subjects: Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:705 , http://hdl.handle.net/10962/d1006499 , Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Description: During this research an attempt was made to gain an understanding of job satisfaction amongst government social workers. To achieve this, twenty social workers employed at the Department of Welfare in East London and Mdantsane were interviewed. South African literature on this topic is limited and it is believed that this study will present a valuable basis to pursue in further research. Literature that was consulted was found to be supportive of the theoretical notion that social work has long been recognised as being a stressful profession and that the nature of social work practice itself can be potentially stressful. The study found that there are many stressors and dissatisfactions which government social workers are currently experiencing. Some of the social workers have indicated a desire to leave the profession as a result of the dissatisfactions. The study findings suggest a need for combining oganisational with individual oriented initiatives to decrease the many stressors the social workers are experiencing. The thesis ends with recommendations of various strategies for addressing the concerns of the social workers in order to increase their job satisfaction
- Full Text:
- Date Issued: 2001
- Authors: Sela, Michelle
- Date: 2001
- Subjects: Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:705 , http://hdl.handle.net/10962/d1006499 , Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Description: During this research an attempt was made to gain an understanding of job satisfaction amongst government social workers. To achieve this, twenty social workers employed at the Department of Welfare in East London and Mdantsane were interviewed. South African literature on this topic is limited and it is believed that this study will present a valuable basis to pursue in further research. Literature that was consulted was found to be supportive of the theoretical notion that social work has long been recognised as being a stressful profession and that the nature of social work practice itself can be potentially stressful. The study found that there are many stressors and dissatisfactions which government social workers are currently experiencing. Some of the social workers have indicated a desire to leave the profession as a result of the dissatisfactions. The study findings suggest a need for combining oganisational with individual oriented initiatives to decrease the many stressors the social workers are experiencing. The thesis ends with recommendations of various strategies for addressing the concerns of the social workers in order to increase their job satisfaction
- Full Text:
- Date Issued: 2001
Extractives from six species of South African Marine Opisthobranch Molluscs
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
Factors Influencing the Entrepreneurial Orientation of Students
- Amos, Trevor L, Louw, L, Baxter, Jeremy
- Authors: Amos, Trevor L , Louw, L , Baxter, Jeremy
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270879 , vital:54488 , xlink:href="https://scialert.net/abstract/?doi=jas.2001.329.334"
- Description: With entrepreneurship being an important catalyst in wealth creation, it is imperative that entrepreneurs be developed. The aim of this exploratory research is to contribute to our understanding of the development of entrepreneurs and to encourage further research in the area. This paper proposes a model of entrepreneurship and tests the influencing factors on this model. Based on the findings of this research, it appears that entrepreneurial activity of family members influences the development of entrepreneurship more than gender, race, age or education. With education being a logical site for the development of entrepreneurship within society, this finding raises more questions than it provides answers, highlighting the need for educators to critically review the educational process if entrepreneurship is to be a realistic outcome.
- Full Text:
- Date Issued: 2001
- Authors: Amos, Trevor L , Louw, L , Baxter, Jeremy
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270879 , vital:54488 , xlink:href="https://scialert.net/abstract/?doi=jas.2001.329.334"
- Description: With entrepreneurship being an important catalyst in wealth creation, it is imperative that entrepreneurs be developed. The aim of this exploratory research is to contribute to our understanding of the development of entrepreneurs and to encourage further research in the area. This paper proposes a model of entrepreneurship and tests the influencing factors on this model. Based on the findings of this research, it appears that entrepreneurial activity of family members influences the development of entrepreneurship more than gender, race, age or education. With education being a logical site for the development of entrepreneurship within society, this finding raises more questions than it provides answers, highlighting the need for educators to critically review the educational process if entrepreneurship is to be a realistic outcome.
- Full Text:
- Date Issued: 2001
Failure rather than success : conflict management and resolution in the Democratic Republic of Congo, 1996-1999
- Authors: Munyae, Isaac Muinde
- Date: 2001
- Subjects: Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2856 , http://hdl.handle.net/10962/d1007427 , Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Description: History has proven time and time again that conflict is an inevitable aspect of any given society. The seemingly long-standing nature of conflicts in Africa has been changing over time and these conflicts have been either inter-state or intra-state. However, sometimes intrastate wars have escalated into regional conflicts. These scenarios can be seen in the Great Lakes region of Africa where you have the civil war of 1996-7 and the rebellion, which began in 1998 in the Democratic Republic of Congo (DRC). In the DRC there have been at least four stages of conflict. The first is against the Belgians and secondly, the civil strife of the early 1960s. Third, is the civil strife against Mobutu and fourthly, currently against Kabila. The expanding nature of conflict is characterised by power struggles, politicisation of ethnicity, and the impact of external forces. It is noted that the expanding nature of conflict calls for a change in the methods of conflict management and resolution. Initially conflicts were resolved through military intervention. but with the complexity of African wars it has become apparent that peaceful methods are more prudent. With reference to Africa it can be assumed that conflicts need to be increasingly resolved through political means, such as the use of the diplomatic process. The conflict in Chad between 1968 and 1984 is a good example in which military intervention was used but failed, giving way to mediation and negotiation through the use of diplomacy. Both the DRC and Chadian conflicts are similar because they witnessed the influence of external forces (neighbouring countries and non-African states such as France and the US) and African states attempting to find solutions to their own problems. The conflict in the DRC provides a unique example of the changing nature of intra-state conflict in Africa. Thus, the study aims to trace the characteristics of conflict in the DRC and attempts made at conflict management and resolution. The study uses the period bet ween 1996 and 1999 because it highlights this change in the nature and character of conflict.
- Full Text:
- Date Issued: 2001
- Authors: Munyae, Isaac Muinde
- Date: 2001
- Subjects: Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2856 , http://hdl.handle.net/10962/d1007427 , Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Description: History has proven time and time again that conflict is an inevitable aspect of any given society. The seemingly long-standing nature of conflicts in Africa has been changing over time and these conflicts have been either inter-state or intra-state. However, sometimes intrastate wars have escalated into regional conflicts. These scenarios can be seen in the Great Lakes region of Africa where you have the civil war of 1996-7 and the rebellion, which began in 1998 in the Democratic Republic of Congo (DRC). In the DRC there have been at least four stages of conflict. The first is against the Belgians and secondly, the civil strife of the early 1960s. Third, is the civil strife against Mobutu and fourthly, currently against Kabila. The expanding nature of conflict is characterised by power struggles, politicisation of ethnicity, and the impact of external forces. It is noted that the expanding nature of conflict calls for a change in the methods of conflict management and resolution. Initially conflicts were resolved through military intervention. but with the complexity of African wars it has become apparent that peaceful methods are more prudent. With reference to Africa it can be assumed that conflicts need to be increasingly resolved through political means, such as the use of the diplomatic process. The conflict in Chad between 1968 and 1984 is a good example in which military intervention was used but failed, giving way to mediation and negotiation through the use of diplomacy. Both the DRC and Chadian conflicts are similar because they witnessed the influence of external forces (neighbouring countries and non-African states such as France and the US) and African states attempting to find solutions to their own problems. The conflict in the DRC provides a unique example of the changing nature of intra-state conflict in Africa. Thus, the study aims to trace the characteristics of conflict in the DRC and attempts made at conflict management and resolution. The study uses the period bet ween 1996 and 1999 because it highlights this change in the nature and character of conflict.
- Full Text:
- Date Issued: 2001
Feeding biology of common and blue duiker
- Authors: Kigozi, Frederick
- Date: 2001
- Subjects: Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5625 , http://hdl.handle.net/10962/d1004725 , Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Description: The blue duiker, Philantomba monticola and common or grey duiker, Sylvicapra grimmia represent two of the three duiker genera as well as two of the three species occurring in Southern Africa. The two species have not been adequately studied in their habitats within the Eastern Cape Province of South Africa, and this thesis centres around their biology with focus on diet and dental microwear. Faecal analysis was used to study the diet of blue duiker at Salem in the Albany district, and of common duiker on two farms, one a predominantly cattle farm at Kasouga and the other a farm for cultivation of chicory at Grants valley, both in the Bathurst district. The validity of faecal analysis was reviewed, and its applicability to blue and common duiker assessed. The method was appropriate for diet analysis of both species, as the common duiker is shy and secretive and the blue duiker is a rare and protected species which does not habituate readily. Results showed that the blue duiker was mainly folivorous with a seasonally stable diet of 79 percent dicot foliage and only 17 percent fruit. Common duiker diet at both study sites comprised mostly dicot foliage, with only two monocotyledonous plant species. Twenty-seven and nineteen plant species were identified in the diets of common duiker at Kasouga and Grants valley respectively and the annual percentage occurrences of dicot foliage in the diets were about 99 percent at both study sites. The predominantly browsing common duiker, therefore offered negligible competition for food resources to the grazing cattle on Kasouga farm. Both blue and common duiker fed selectively, with approximately one third of the total number of plant species identified in their diets providing at least 50 percent of the food eaten annually. Ehretia rigida was the most important plant species in the diets of both duiker species. Chicory, Chichorium intybus provided more than one third (35.6 percent) of the winter diet and a substantial proportion (14.4 percent) of the spring diet of common duiker at Grants valley, thereby confirming earlier reports of this species feeding on chicory and other cultivated crops. The diet of common duiker at Kasouga did not vary seasonally but that of common duiker at Grants valley did vary and this was attributed to utilisation of chicory. Results from the dental microwear analyses did not show any significant differences in dental microwear between blue and common duiker, but supported and confirmed that the two were browsing species, characterised by many pits and few scratches on their dental surfaces. A high incidence of pits was found on the dental surfaces of both duiker species, and was attributed to utilisation of fruit in the diet.
- Full Text:
- Date Issued: 2001
- Authors: Kigozi, Frederick
- Date: 2001
- Subjects: Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5625 , http://hdl.handle.net/10962/d1004725 , Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Description: The blue duiker, Philantomba monticola and common or grey duiker, Sylvicapra grimmia represent two of the three duiker genera as well as two of the three species occurring in Southern Africa. The two species have not been adequately studied in their habitats within the Eastern Cape Province of South Africa, and this thesis centres around their biology with focus on diet and dental microwear. Faecal analysis was used to study the diet of blue duiker at Salem in the Albany district, and of common duiker on two farms, one a predominantly cattle farm at Kasouga and the other a farm for cultivation of chicory at Grants valley, both in the Bathurst district. The validity of faecal analysis was reviewed, and its applicability to blue and common duiker assessed. The method was appropriate for diet analysis of both species, as the common duiker is shy and secretive and the blue duiker is a rare and protected species which does not habituate readily. Results showed that the blue duiker was mainly folivorous with a seasonally stable diet of 79 percent dicot foliage and only 17 percent fruit. Common duiker diet at both study sites comprised mostly dicot foliage, with only two monocotyledonous plant species. Twenty-seven and nineteen plant species were identified in the diets of common duiker at Kasouga and Grants valley respectively and the annual percentage occurrences of dicot foliage in the diets were about 99 percent at both study sites. The predominantly browsing common duiker, therefore offered negligible competition for food resources to the grazing cattle on Kasouga farm. Both blue and common duiker fed selectively, with approximately one third of the total number of plant species identified in their diets providing at least 50 percent of the food eaten annually. Ehretia rigida was the most important plant species in the diets of both duiker species. Chicory, Chichorium intybus provided more than one third (35.6 percent) of the winter diet and a substantial proportion (14.4 percent) of the spring diet of common duiker at Grants valley, thereby confirming earlier reports of this species feeding on chicory and other cultivated crops. The diet of common duiker at Kasouga did not vary seasonally but that of common duiker at Grants valley did vary and this was attributed to utilisation of chicory. Results from the dental microwear analyses did not show any significant differences in dental microwear between blue and common duiker, but supported and confirmed that the two were browsing species, characterised by many pits and few scratches on their dental surfaces. A high incidence of pits was found on the dental surfaces of both duiker species, and was attributed to utilisation of fruit in the diet.
- Full Text:
- Date Issued: 2001
Feeding ecology of Bathyclarias nyasensis (Siluroidei: Claridae) from Lake Malawi
- Kaunda, Emmanuel Kamlipe Watson Hawkins
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
- Full Text:
- Date Issued: 2001
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
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- Date Issued: 2001