An investigation of the security of passwords derived from African languages
- Authors: Sishi, Sibusiso Teboho
- Date: 2019
- Subjects: Computers -- Access control -- Passwords , Computer users -- Attitudes , Internet -- Access control , Internet -- Security measures , Internet -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163273 , vital:41024
- Description: Password authentication has become ubiquitous in the cyber age. To-date, there have been several studies on country based passwords by authors who studied, amongst others, English, Finnish, Italian and Chinese based passwords. However, there has been a lack of focused study on the type of passwords that are being created in Africa and whether there are benefits in creating passwords in an African language. For this research, password databases containing LAN Manager (LM) and NT LAN Manager (NTLM) hashes extracted from South African organisations in a variety of sectors in the economy, were obtained to gain an understanding of user behaviour in creating passwords. Analysis of the passwords obtained from these hashes (using several cracking methods) showed that many organisational passwords are based on the English language. This is understandable considering that the business language in South Africa is English even though South Africa has 11 official languages. African language based passwords were derived from known English weak passwords and some of the passwords were appended with numbers and special characters. The African based passwords created using eight Southern African languages were then uploaded to the Internet to test the security around using passwords based on African languages. Since most of the passwords were able to be cracked by third party researchers, we conclude that any password that is derived from known weak English words marked no improvement in the security of a password written in an African language, especially the more widely spoken languages, namely, isiZulu, isiXhosa and Setswana.
- Full Text:
- Date Issued: 2019
- Authors: Sishi, Sibusiso Teboho
- Date: 2019
- Subjects: Computers -- Access control -- Passwords , Computer users -- Attitudes , Internet -- Access control , Internet -- Security measures , Internet -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163273 , vital:41024
- Description: Password authentication has become ubiquitous in the cyber age. To-date, there have been several studies on country based passwords by authors who studied, amongst others, English, Finnish, Italian and Chinese based passwords. However, there has been a lack of focused study on the type of passwords that are being created in Africa and whether there are benefits in creating passwords in an African language. For this research, password databases containing LAN Manager (LM) and NT LAN Manager (NTLM) hashes extracted from South African organisations in a variety of sectors in the economy, were obtained to gain an understanding of user behaviour in creating passwords. Analysis of the passwords obtained from these hashes (using several cracking methods) showed that many organisational passwords are based on the English language. This is understandable considering that the business language in South Africa is English even though South Africa has 11 official languages. African language based passwords were derived from known English weak passwords and some of the passwords were appended with numbers and special characters. The African based passwords created using eight Southern African languages were then uploaded to the Internet to test the security around using passwords based on African languages. Since most of the passwords were able to be cracked by third party researchers, we conclude that any password that is derived from known weak English words marked no improvement in the security of a password written in an African language, especially the more widely spoken languages, namely, isiZulu, isiXhosa and Setswana.
- Full Text:
- Date Issued: 2019
The contribution of small-scale fisheries to rural livelihoods and food security : evidence from Hamburg, Eastern Cape Province, South Africa
- Authors: Budaza, Nwabisa
- Date: 2018
- Subjects: Small-scale fisheries -- South Africa -- Eastern Cape Food supply -- South Africa -- Eastern Cape Fishery management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10338 , vital:35396
- Description: Small-scale fisheries are known to provide food and income to millions of people around the world, but their role and existence is often ignored in development planning. The growing human demand for animal protein has become one of the foremost world challenges for which aquatic organisms have a significant role to play. In South Africa, small-scale fisheries have been recognized since the end of Apartheid, but the extent of the contribution of the sector to rural livelihoods and food security is not well understood. Using data drawn from a sample of 80 fishers in the coastal community of Hamburg, Eastern Cape, this dissertation presents an assessment of the contribution of small-scale fisheries to rural livelihoods, income and food security. The primary data were collected from the fishers using a structured questionnaire and non-probability sampling. The data were analysed with the assistance of descriptive techniques and a few simply statistical tests. The results of the study indicate that fishers in Hamburg catch a wide range of fish, which include wild kob, octopus, spotted grunter, white/black mussel cracker and white steenbras. Fishers in the study area are not solely dependent on small-scale fisheries for their livelihoods, income and food security, but generally supplement their welfare payments with fishing in order to sustain their livelihoods. About 78percent of the surveyed fishers depend on government grants, including old age grants, child support grants and social care grant. In terms of employment, 15percent of the surveyed fishers are casually employed, while 6percent are formally employed on a contract basis. Although they are not only dependent on fishing, nevertheless fishing is an important source of livelihood, income and food security. About 37percent of the fishers harvest marine resources for home consumption, while 7percent harvest solely for income, and 56percent harvest for both home consumption and income. Income generated from fisheries is approximately R935 per month and is used to buy food, electricity, fishing equipment and other household needs. The findings from this research underline the need for interventions such as coordinated institutions, improved infrastructure, improved monitoring and enforcement systems, as well as improved access to permit/fishing rights for sustainable use of marine resources.
- Full Text:
- Date Issued: 2018
- Authors: Budaza, Nwabisa
- Date: 2018
- Subjects: Small-scale fisheries -- South Africa -- Eastern Cape Food supply -- South Africa -- Eastern Cape Fishery management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10338 , vital:35396
- Description: Small-scale fisheries are known to provide food and income to millions of people around the world, but their role and existence is often ignored in development planning. The growing human demand for animal protein has become one of the foremost world challenges for which aquatic organisms have a significant role to play. In South Africa, small-scale fisheries have been recognized since the end of Apartheid, but the extent of the contribution of the sector to rural livelihoods and food security is not well understood. Using data drawn from a sample of 80 fishers in the coastal community of Hamburg, Eastern Cape, this dissertation presents an assessment of the contribution of small-scale fisheries to rural livelihoods, income and food security. The primary data were collected from the fishers using a structured questionnaire and non-probability sampling. The data were analysed with the assistance of descriptive techniques and a few simply statistical tests. The results of the study indicate that fishers in Hamburg catch a wide range of fish, which include wild kob, octopus, spotted grunter, white/black mussel cracker and white steenbras. Fishers in the study area are not solely dependent on small-scale fisheries for their livelihoods, income and food security, but generally supplement their welfare payments with fishing in order to sustain their livelihoods. About 78percent of the surveyed fishers depend on government grants, including old age grants, child support grants and social care grant. In terms of employment, 15percent of the surveyed fishers are casually employed, while 6percent are formally employed on a contract basis. Although they are not only dependent on fishing, nevertheless fishing is an important source of livelihood, income and food security. About 37percent of the fishers harvest marine resources for home consumption, while 7percent harvest solely for income, and 56percent harvest for both home consumption and income. Income generated from fisheries is approximately R935 per month and is used to buy food, electricity, fishing equipment and other household needs. The findings from this research underline the need for interventions such as coordinated institutions, improved infrastructure, improved monitoring and enforcement systems, as well as improved access to permit/fishing rights for sustainable use of marine resources.
- Full Text:
- Date Issued: 2018
Physiochemical and heavy metals fingerprints of the final effluents of Adelaide and Seymour wastewater treatment facilities in the Eastern Cape, South Africa
- Authors: Mutukwa, Dorcas
- Date: 2017
- Subjects: Water -- Purification Effluent quality -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8089 , vital:31520
- Description: Wastewater contains pathogens, heavy metals, nutrients, organic matter and other toxic chemicals and when discharged into the environment without proper treatment, it may cause adverse health problems and environment degradation. There have been reports in the Eastern Cape Province, South Africa of inadequate treated wastewater effluents being discharged into freshwater environments. This study reports on the physicochemical and heavy metals qualities for two wastewater treatment facilities in the Eastern Cape, South Africa over a six-month sampling period (September 2015 to February 2016). Wastewater effluent samples were collected from the influents, final effluents and receiving waterbodies as well as sludge samples in replicates. The physicochemical parameters were analysed using standard methods (APHA, 2012). The acid digested heavy metals samples were analysed using Atomic Absorption Spectrophotometer (iCE 3500 Thermo Fisher Spectrometer). The concentrations were compared to recommended limits used in South Africa and World Health Organisation (WHO). Physicochemical qualities assessed at Adelaide wastewater treatment plant ranged as follows: temperature (21.6 - 30.5 oC), turbidity (2.1 – 71.3 NTU), electrical conductivity (EC) (743.0 – 898.3 μ/Scm) and dissolved oxygen (DO) (2.11 – 3.50 mg/L) while the ranges of the parameter assessed at Seymour wastewater treatment plant ranged as follows: chemical dissolved oxygen (COD) (41.7 – 115.3 mg/L), EC (628 and 797.7 μ/Scm) and nitrates (4.6 – 11.0 mg/L. The heavy metals concentration for the final effluents at Adelaide wastewater treatment plant ranged as follows: Cd (0 – 0.002 mg/L), Cu (0 – 0.096 mg/L) and Fe (0 – 0.498 mg/L). Cu concentrations in sludge at Seymour wastewater treatment plant ranged between 83.82 and 132.07 mg/L. Reduction efficiencies of Adelaide in removing chlorides and sulphates were 33 and 36 percent respectively. Findings of study revealed negative impacts of inadequately treated effluents on receiving waterbodies and this puts communities which rely on the water as immediate source of fresh water for domestic purposes at health risk.
- Full Text:
- Date Issued: 2017
- Authors: Mutukwa, Dorcas
- Date: 2017
- Subjects: Water -- Purification Effluent quality -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/8089 , vital:31520
- Description: Wastewater contains pathogens, heavy metals, nutrients, organic matter and other toxic chemicals and when discharged into the environment without proper treatment, it may cause adverse health problems and environment degradation. There have been reports in the Eastern Cape Province, South Africa of inadequate treated wastewater effluents being discharged into freshwater environments. This study reports on the physicochemical and heavy metals qualities for two wastewater treatment facilities in the Eastern Cape, South Africa over a six-month sampling period (September 2015 to February 2016). Wastewater effluent samples were collected from the influents, final effluents and receiving waterbodies as well as sludge samples in replicates. The physicochemical parameters were analysed using standard methods (APHA, 2012). The acid digested heavy metals samples were analysed using Atomic Absorption Spectrophotometer (iCE 3500 Thermo Fisher Spectrometer). The concentrations were compared to recommended limits used in South Africa and World Health Organisation (WHO). Physicochemical qualities assessed at Adelaide wastewater treatment plant ranged as follows: temperature (21.6 - 30.5 oC), turbidity (2.1 – 71.3 NTU), electrical conductivity (EC) (743.0 – 898.3 μ/Scm) and dissolved oxygen (DO) (2.11 – 3.50 mg/L) while the ranges of the parameter assessed at Seymour wastewater treatment plant ranged as follows: chemical dissolved oxygen (COD) (41.7 – 115.3 mg/L), EC (628 and 797.7 μ/Scm) and nitrates (4.6 – 11.0 mg/L. The heavy metals concentration for the final effluents at Adelaide wastewater treatment plant ranged as follows: Cd (0 – 0.002 mg/L), Cu (0 – 0.096 mg/L) and Fe (0 – 0.498 mg/L). Cu concentrations in sludge at Seymour wastewater treatment plant ranged between 83.82 and 132.07 mg/L. Reduction efficiencies of Adelaide in removing chlorides and sulphates were 33 and 36 percent respectively. Findings of study revealed negative impacts of inadequately treated effluents on receiving waterbodies and this puts communities which rely on the water as immediate source of fresh water for domestic purposes at health risk.
- Full Text:
- Date Issued: 2017
Development of a stemmer for the isiXhosa language
- Authors: Nogwina, Mnoneleli
- Date: 2016
- Subjects: Computational linguistics Language and languages Xhosa language
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2611 , vital:27938
- Description: IsiXhosa language is one of the eleven official languages and the second most widely spoken language in South Africa. However, in terms of computational linguistics, the language did not get attention and natural language related work is almost non-existent. Document retrieval using unstructured queries requires some kind of language processing, and an efficient retrieval of documents can be achieved if we use a technique called stemming. The area that involves document storage and retrieval is called Information Retrieval (IR). Basically, IR systems make use of a Stemmer to index document representations and also terms in users’ queries to retrieve matching documents. In this dissertation, we present the developed Stemmer that can be used in both conditions. The Stemmer is used in IR systems, like Google to retrieve documents written in isiXhosa. In the Eastern Cape Province of South Africa many public schools take isiXhosa as a subject and also a number of Universities in South Africa teach isiXhosa. Therefore, for a language important such as this, it is important to make valuable information that is available online accessible to users through the use of IR systems. In our efforts to develop a Stemmer for the isiXhosa language, an investigation on how others have developed Stemmers for other languages was carried out. From the investigation we came to realize that the Porter stemming algorithm in particular was the main algorithm that many of other Stemmers make use of as a reference. We found that Porter’s algorithm could not be used in its totality in the development of the isiXhosa Stemmer because of the morphological complexity of the language. We developed an affix removal that is embedded with rules that determine which order should be followed in stripping the affixes. The rule is that, the word under consideration is checked against the exceptions, if it’s not in the exceptions list then the stripping continue in the following order; Prefix removal, Suffix removal and finally save the result as stem. The Stemmer was successfully developed and was tested and evaluated in a sample data that was randomly collected from the isiXhosa text books and isiXhosa dictionary. From the results obtained we concluded that the Stemmer can be used in IR systems as it showed 91 percent accuracy. The errors were 9 percent and therefore these results are within the accepted range and therefore the Stemmer can be used to help in retrieval of isiXhosa documents. This is only a noun Stemmer and in the future it can be extended to also stem verbs as well. The Stemmer can also be used in the development of spell-checkers of isiXhosa.
- Full Text:
- Date Issued: 2016
- Authors: Nogwina, Mnoneleli
- Date: 2016
- Subjects: Computational linguistics Language and languages Xhosa language
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2611 , vital:27938
- Description: IsiXhosa language is one of the eleven official languages and the second most widely spoken language in South Africa. However, in terms of computational linguistics, the language did not get attention and natural language related work is almost non-existent. Document retrieval using unstructured queries requires some kind of language processing, and an efficient retrieval of documents can be achieved if we use a technique called stemming. The area that involves document storage and retrieval is called Information Retrieval (IR). Basically, IR systems make use of a Stemmer to index document representations and also terms in users’ queries to retrieve matching documents. In this dissertation, we present the developed Stemmer that can be used in both conditions. The Stemmer is used in IR systems, like Google to retrieve documents written in isiXhosa. In the Eastern Cape Province of South Africa many public schools take isiXhosa as a subject and also a number of Universities in South Africa teach isiXhosa. Therefore, for a language important such as this, it is important to make valuable information that is available online accessible to users through the use of IR systems. In our efforts to develop a Stemmer for the isiXhosa language, an investigation on how others have developed Stemmers for other languages was carried out. From the investigation we came to realize that the Porter stemming algorithm in particular was the main algorithm that many of other Stemmers make use of as a reference. We found that Porter’s algorithm could not be used in its totality in the development of the isiXhosa Stemmer because of the morphological complexity of the language. We developed an affix removal that is embedded with rules that determine which order should be followed in stripping the affixes. The rule is that, the word under consideration is checked against the exceptions, if it’s not in the exceptions list then the stripping continue in the following order; Prefix removal, Suffix removal and finally save the result as stem. The Stemmer was successfully developed and was tested and evaluated in a sample data that was randomly collected from the isiXhosa text books and isiXhosa dictionary. From the results obtained we concluded that the Stemmer can be used in IR systems as it showed 91 percent accuracy. The errors were 9 percent and therefore these results are within the accepted range and therefore the Stemmer can be used to help in retrieval of isiXhosa documents. This is only a noun Stemmer and in the future it can be extended to also stem verbs as well. The Stemmer can also be used in the development of spell-checkers of isiXhosa.
- Full Text:
- Date Issued: 2016
Monitoring changes in vegetation distribution to ascertain the extent of degradation in the savannas of Nkonkobe Local Municipality, Eastern Cape, South Africa
- Authors: Masiza, Wonga
- Date: 2016
- Subjects: Savanna ecology -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2027 , vital:27598
- Description: Savanna degradation is an environmental problem occurring in most countries around the world and it poses threats to biodiversity conservation, the food industry, and other economic sectors. According to FAO, South Africa’s rangelands exhibit the highest rate of fragmentation in comparison to range ecosystems in neighbouring countries including Lesotho and Swaziland, and consensus among researchers is that communal rangelands are more degraded than commercial rangelands. Although researchers and communities have identified the occurrence of land degradation in communal savannas at a local scale, land degradation has been poorly estimated because little has been done to quantify the extent and dynamics of perceived and observed changes associated with land degradation. The main goal of this study is to provide empirical insights on the direction of changes in the communal savannas of Nkonkobe Local Municipality in order to inform policy formulation and implementation. Additional to the communal sites is a private farm included for comparative analysis of trends in communal and commercial savannas. Landsat imagery was used to map, assess, and quantify the extent of land degradation in Nkonkobe Local Municipality, over a period of 30 years between 1984 and 2014. Field investigations were undertaken in June 2015 to acquire reference data to guide supervised classification of Landsat images. Three algorithms (Mahalanobis-distance, Minimum-distance, and Maximum likelihood classification) were compared to identify a classifier that produced the best results. The maximum likelihood classifier produced the best results with classification accuracy levels of 95.24 percent, 89.66 percent, and 95.65 percent for Honeydale Farm, Thyume, and Sheshegu respectively. Regression analysis revealed that both communal and private lands have experienced statistically significant increases in bush encroachment and decreases in surface water. Communal savannas have been confronted more by expansion of built-up area, decrease in open grassland, abandonment of arable land, soil erosion, and a steady invasion by Acacia Karroo compared to the privately owned commercial farm. The land cover changes measured through this investigation suggest an environmental shift that threatens biodiversity and agricultural activity. The study provides empirically informed insights about the direction to which these savannas are changing with the hope that the findings will prompt formulation and implementation of effective policies.
- Full Text:
- Date Issued: 2016
- Authors: Masiza, Wonga
- Date: 2016
- Subjects: Savanna ecology -- South Africa -- Eastern Cape Land degradation -- South Africa -- Eastern Cape Vegetation management -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2027 , vital:27598
- Description: Savanna degradation is an environmental problem occurring in most countries around the world and it poses threats to biodiversity conservation, the food industry, and other economic sectors. According to FAO, South Africa’s rangelands exhibit the highest rate of fragmentation in comparison to range ecosystems in neighbouring countries including Lesotho and Swaziland, and consensus among researchers is that communal rangelands are more degraded than commercial rangelands. Although researchers and communities have identified the occurrence of land degradation in communal savannas at a local scale, land degradation has been poorly estimated because little has been done to quantify the extent and dynamics of perceived and observed changes associated with land degradation. The main goal of this study is to provide empirical insights on the direction of changes in the communal savannas of Nkonkobe Local Municipality in order to inform policy formulation and implementation. Additional to the communal sites is a private farm included for comparative analysis of trends in communal and commercial savannas. Landsat imagery was used to map, assess, and quantify the extent of land degradation in Nkonkobe Local Municipality, over a period of 30 years between 1984 and 2014. Field investigations were undertaken in June 2015 to acquire reference data to guide supervised classification of Landsat images. Three algorithms (Mahalanobis-distance, Minimum-distance, and Maximum likelihood classification) were compared to identify a classifier that produced the best results. The maximum likelihood classifier produced the best results with classification accuracy levels of 95.24 percent, 89.66 percent, and 95.65 percent for Honeydale Farm, Thyume, and Sheshegu respectively. Regression analysis revealed that both communal and private lands have experienced statistically significant increases in bush encroachment and decreases in surface water. Communal savannas have been confronted more by expansion of built-up area, decrease in open grassland, abandonment of arable land, soil erosion, and a steady invasion by Acacia Karroo compared to the privately owned commercial farm. The land cover changes measured through this investigation suggest an environmental shift that threatens biodiversity and agricultural activity. The study provides empirically informed insights about the direction to which these savannas are changing with the hope that the findings will prompt formulation and implementation of effective policies.
- Full Text:
- Date Issued: 2016
Strategic management of construction companies
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
- Authors: Van Rooyen, Roelof Petrus
- Date: 2013
- Subjects: Construction industry -- Planning , Business planning -- South Africa -- Eastern Cape , Corporate turnarounds -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9712 , http://hdl.handle.net/10948/d1020407
- Description: The research emanated from an investigation of GB7, GB8 and GB9 main contractors in the Eastern Cape Province of South Africa. The study was focussed on the strident economic times in the construction industry following the FIFA Soccer World Cup from August 2010 to December 2012. The research was conducted to identify the key strategy or combination of strategies keeping construction entities in operation. The study further investigates the key elements of a successful turnaround strategy as well as the most effective methods in implementing strategies within construction organizations. The research took the form of an empirical quantitative study where a descriptive survey was used to collect data. Structured interviews were held with the target population to collect data in the field. The study established that geographic diversification was the most effective method utilized by main contractors for survival during the study timeframe. The study also found that lowering of profit margins and preliminary and general amounts were most effective methods in the use of turn around strategies. The study finally concluded that effective steps were taken by main contractors in the Eastern Cape to implement corporate strategies within their organizations. Step by step guidance to all employees on new processes was the key element in successful strategic implementation of a strategy within construction organizations. The research conducted contributes to the strategic management competency within the built environment as well as the existing body of knowledge within the construction industry. All members of the construction industry in South Africa involved with strategic level planning of entities would value the study.
- Full Text:
- Date Issued: 2013
Digestible energy as a criterion for the development of diets for the African sharptooth catfish, Clarias gariepinus (Pisces: Clariidae)
- Authors: Rouhani, Q A
- Date: 1993
- Subjects: Clariidae , Catfishes -- Africa , Catfishes -- Nutrition -- Requirements -- Africa , Catfishes , Clarias
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5259 , http://hdl.handle.net/10962/d1005103
- Description: Based on a number of attributes, the African sharptooth catfish, Clarias gariepinus is an ideal aquaculture species. Much work has been undertaken on developing the technology for the commercial culture of the species inclusive of determining the nutritional requirements for cost effective feed formulation. However, digestible energy (DE) values for specific feed ingredients were unknown. As DE values are not interchangeable between species, this study set out to determine the DE values for conventional and unconventional feed-ingredients for the formulation of an optimal feed. The ultimate goal in feed formulation is to produce a diet that supports the maximum production at the least cost. The indirect method was found to be most suitable in obtaining DE values for the catfish. Feed samples were marked by adding 2% chromic oxide as an inert indicator. The fish were then force-fed and faecal samples were obtained from the hindgut by stripping the fish 10 hours after feeding as this was found to be when the hind-gut was at its fullest and the feed maximally digested. A linear based computer programme was used to formulate experimental diets using the established DE values as an additional variable. The formulated feed was tested and compared to a commercial catfish diet and a standard reference diet (H-440). All of the newly formulated feeds were found to be cheaper to manufacture (by between 5 and 10%). Statistically (ANOVA), all of the experimental diets resulted in higher specific growth rates (SGR) than the standard reference diet. The commercial diet also resulted in a lower SGR than those experimental diets with similar protein levels.
- Full Text:
- Date Issued: 1993
- Authors: Rouhani, Q A
- Date: 1993
- Subjects: Clariidae , Catfishes -- Africa , Catfishes -- Nutrition -- Requirements -- Africa , Catfishes , Clarias
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5259 , http://hdl.handle.net/10962/d1005103
- Description: Based on a number of attributes, the African sharptooth catfish, Clarias gariepinus is an ideal aquaculture species. Much work has been undertaken on developing the technology for the commercial culture of the species inclusive of determining the nutritional requirements for cost effective feed formulation. However, digestible energy (DE) values for specific feed ingredients were unknown. As DE values are not interchangeable between species, this study set out to determine the DE values for conventional and unconventional feed-ingredients for the formulation of an optimal feed. The ultimate goal in feed formulation is to produce a diet that supports the maximum production at the least cost. The indirect method was found to be most suitable in obtaining DE values for the catfish. Feed samples were marked by adding 2% chromic oxide as an inert indicator. The fish were then force-fed and faecal samples were obtained from the hindgut by stripping the fish 10 hours after feeding as this was found to be when the hind-gut was at its fullest and the feed maximally digested. A linear based computer programme was used to formulate experimental diets using the established DE values as an additional variable. The formulated feed was tested and compared to a commercial catfish diet and a standard reference diet (H-440). All of the newly formulated feeds were found to be cheaper to manufacture (by between 5 and 10%). Statistically (ANOVA), all of the experimental diets resulted in higher specific growth rates (SGR) than the standard reference diet. The commercial diet also resulted in a lower SGR than those experimental diets with similar protein levels.
- Full Text:
- Date Issued: 1993
The interactive effects of light, temperature and CO₂/O₂ ratios in photosynthesis of Coix lachryma-jobi L
- Authors: Mjwara, Jabulani Michael
- Date: 1992
- Subjects: Coix , Plants -- Effect of light on , Plants -- Effect of oxygen on , Plants -- Effect of carbon dioxide on , Photosynthesis , Plants -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4216 , http://hdl.handle.net/10962/d1003785
- Description: A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
- Full Text:
- Date Issued: 1992
- Authors: Mjwara, Jabulani Michael
- Date: 1992
- Subjects: Coix , Plants -- Effect of light on , Plants -- Effect of oxygen on , Plants -- Effect of carbon dioxide on , Photosynthesis , Plants -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4216 , http://hdl.handle.net/10962/d1003785
- Description: A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
- Full Text:
- Date Issued: 1992
Guibourtacacidin: a new Leuco-anthocyanidin from Rhodesian copalwood; (Guibourtia coleosperma)
- Authors: De Bruyn, Guustaaf Cornelis
- Date: 1962
- Subjects: Phanerogams , Angiosperms , Flavonoids , Anthocyanidins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4459 , http://hdl.handle.net/10962/d1011043
- Description: A new leuco-anthocyanidin, (+)-7,4'dihydroxyflavan- 3:4-diol has been isolated from the heartwood of Guibourtia coleosperma. The heartwood extractives were fractionated by enrichment procedures involving fractional precipitation and Craig partitioning, to give a high RF (subscript) low molecular weight fraction containing the above leuco -anthocyanidin. This was further fractionated by "preparative" paper chromatography . The leuco-anthocyanidin was amorphous and present in low proportion (0.004%) in the wood. On boiling with alcoholic hydrochloric acid the compound gave an anthocyanidin which was identified as 3,7,4'-trihydroxyflavylium chloride. The degradation products formed by alkali fusion, on a micro-scale, were resorcinol and ♭-resorcylic acid, and also p (underscore)-hydroxybenzoic acid. This indicated resorcinol and phenol A and B nuclei respectively. The formation of amorphous dimethyl ether and tetra-acetoxy derivatives indicated two phenolic and two alcoholic hydroxyl groups. The above indicates that the compound was 7,4'-dihydroxyflavan- 3:4- diol and a molecular weight estimation showed it to be monomeric. Comparison of the infrared absorption spectra of the natural dimethyl ether with synthetic (±) dimethoxyflavan- 3:4-diol, to which a tentative 2:3- trans- 3:4-cis conformation had been assigned (Phatak and Kulkarni 94), showed close identity. Crystalline (±)-7, 4 '-dihydroxyflavan- 3:4 - diol was synthesised by catalytic hydrogenation over platinum oxide of the corresponoing (±) -7,4'-dihydroxyflavanonol. The flavanonol was synthesised by sodium hyposulphite reduction of the 7,4 ' -dihydroxyflavonol. The infrared absorption spectra of the natural and synthetic diols were similar but not identical. Chromatographic evidence showed the apparent identity of the synthetic and natural flavan- 3:4- diols, and two possible configurations were assigned for the natural flavan-3:4-diol. The new leuco-anthocyanidin was observed to form an O(underscore)-ethyl ether derivative on manipulation in ethanol. A monomeric leuco- fisetinidin from the heartwood was identified, by two dimensional paper chromatography, as (+) - mollisacacidin. The condensed tannins found also in the heartwood of G.(underscore)- coleosperma appear to be polymeric forms of leuco - fisetinidin and leuco - guibourtinidin. These polymeric tannins form a large proportion of the heartwood extractives and furnish high yields of fisetinidin and guibourtinidin chlorides on boiling with alcoholic hydrochloric acid. Examination of some other members of the Guibourtia spp . by paper chromatography showed that only G (underscore). coleosperma contained the new leuco - anthocyanidin as well as a leuco - fisetinidin. G. (underscore) tessmannii and G. (underscore) demeusii heartwoods contained only leuco-fisetinidin and the related polymers and a close chemical relationship to G.(underscore) coleosperma is thus apparent. G.(underscore) arnoldiana on the other hand is not chemically interrelated with the above members since it appeared to contain only leuco - cyanidin. (±) - 7,4 ' -Dihydroxyflavan- 4-ol was synthesised by hydrogenation of the corresponding flavanone over platinum oxide. Observations were made regarding its reddenig and ease of condensation.
- Full Text:
- Date Issued: 1962
- Authors: De Bruyn, Guustaaf Cornelis
- Date: 1962
- Subjects: Phanerogams , Angiosperms , Flavonoids , Anthocyanidins
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4459 , http://hdl.handle.net/10962/d1011043
- Description: A new leuco-anthocyanidin, (+)-7,4'dihydroxyflavan- 3:4-diol has been isolated from the heartwood of Guibourtia coleosperma. The heartwood extractives were fractionated by enrichment procedures involving fractional precipitation and Craig partitioning, to give a high RF (subscript) low molecular weight fraction containing the above leuco -anthocyanidin. This was further fractionated by "preparative" paper chromatography . The leuco-anthocyanidin was amorphous and present in low proportion (0.004%) in the wood. On boiling with alcoholic hydrochloric acid the compound gave an anthocyanidin which was identified as 3,7,4'-trihydroxyflavylium chloride. The degradation products formed by alkali fusion, on a micro-scale, were resorcinol and ♭-resorcylic acid, and also p (underscore)-hydroxybenzoic acid. This indicated resorcinol and phenol A and B nuclei respectively. The formation of amorphous dimethyl ether and tetra-acetoxy derivatives indicated two phenolic and two alcoholic hydroxyl groups. The above indicates that the compound was 7,4'-dihydroxyflavan- 3:4- diol and a molecular weight estimation showed it to be monomeric. Comparison of the infrared absorption spectra of the natural dimethyl ether with synthetic (±) dimethoxyflavan- 3:4-diol, to which a tentative 2:3- trans- 3:4-cis conformation had been assigned (Phatak and Kulkarni 94), showed close identity. Crystalline (±)-7, 4 '-dihydroxyflavan- 3:4 - diol was synthesised by catalytic hydrogenation over platinum oxide of the corresponoing (±) -7,4'-dihydroxyflavanonol. The flavanonol was synthesised by sodium hyposulphite reduction of the 7,4 ' -dihydroxyflavonol. The infrared absorption spectra of the natural and synthetic diols were similar but not identical. Chromatographic evidence showed the apparent identity of the synthetic and natural flavan- 3:4- diols, and two possible configurations were assigned for the natural flavan-3:4-diol. The new leuco-anthocyanidin was observed to form an O(underscore)-ethyl ether derivative on manipulation in ethanol. A monomeric leuco- fisetinidin from the heartwood was identified, by two dimensional paper chromatography, as (+) - mollisacacidin. The condensed tannins found also in the heartwood of G.(underscore)- coleosperma appear to be polymeric forms of leuco - fisetinidin and leuco - guibourtinidin. These polymeric tannins form a large proportion of the heartwood extractives and furnish high yields of fisetinidin and guibourtinidin chlorides on boiling with alcoholic hydrochloric acid. Examination of some other members of the Guibourtia spp . by paper chromatography showed that only G (underscore). coleosperma contained the new leuco - anthocyanidin as well as a leuco - fisetinidin. G. (underscore) tessmannii and G. (underscore) demeusii heartwoods contained only leuco-fisetinidin and the related polymers and a close chemical relationship to G.(underscore) coleosperma is thus apparent. G.(underscore) arnoldiana on the other hand is not chemically interrelated with the above members since it appeared to contain only leuco - cyanidin. (±) - 7,4 ' -Dihydroxyflavan- 4-ol was synthesised by hydrogenation of the corresponding flavanone over platinum oxide. Observations were made regarding its reddenig and ease of condensation.
- Full Text:
- Date Issued: 1962
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