Practical and scalable synthesis of N-Alkyl-N,N'Diacylhydrazines
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
- Authors: Gouws, Melissa Claire
- Date: 2008
- Subjects: Chemistry, Organic , Acylation , Insecticides
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10406 , http://hdl.handle.net/10948/696 , Chemistry, Organic , Acylation , Insecticides
- Description: The work presented in this thesis is concerned with the evaluation of potential synthetic routes for the diacylhydrazine group of compounds, and particularly, unsymmetrical diacylhydrazines. Diacylhydrazines form the basis for a relatively new group of insecticides that have molt accelerating properties, and which are considered to offer substantial advantages over other insecticides used for the control of certain insects. The overall objective for this study is to evaluate different potential synthetic routes for a model diacylhydrazine with the view to define potentially scaleable routes. The compound selected for this study was the unsymmetrical diacylhydrazine, N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)-carboxamide since it offers the same range of challenges that would be expected for the synthesis of other similar unsymmetrical diacylhydrazines. Thus, the synthesis of unsymmetrical diacylhydrazines require two reaction steps: The first step is the synthesis of the intermediate mono-acylhydrazine, while the second step is the synthesis of the desired diacylhydrazine from the intermediate mono-acylhydrazine. The most important factor in the two-step reaction sequence is to obtain a high degree of selectivity for the desired mono-acylhydrazine isomer. Acylation of t-butylhydrazine using 4-methylbenzoyl chloride can produce the desired product N-[(tert-butyl)amino](4-methylphenyl)carboxamide in yields above 90 percent, but this reaction produces a variety of by-products, including the “wrong” isomer (N-amino-N- (tert-butyl)(4-methylphenyl)carboximide). Unexpected byproducts for this particular acylation reaction, not previously reported in the literature have also been identified during this investigation. This includes a de-butylated diacylhydrazine, (4-methylphenyl)- N-[(4-methylphenyl)carbonylamino] carboxamide. Although the reaction between tert-butylhydrazine and 4-methylbenzaldehyde is very selective giving near quantitative yields of the desired hydrazone, the subsequent conversion of the hydrazone into the desired mono-acylhydrazine is problematic. The most promising route appears via bromination to form the hydrazidic bromide, followed by hydrolysis of the hydrazidic bromide. Yields for the bromination reaction during this investigation were somewhat higher than that reported previously in literature. Hydrolysis of the hydrazidic bromide, apparently also results in the hydrolysis of the reaction product to give an ester of the free acid (when an ester solvent is used). The synthesis of N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide was only briefly considered to evaluate essentially two approaches, namely: · The conversion of the monoacylhydrazine, N-[(tert-butyl)amino](4- methylphenyl)carboxamide, by acylating with either benzoyl chloride or methylbenzoate (gave 86 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide when benzoyl chloride was used as acylating agent); and · The one-pot conversion of the hydrazone, [(1E)-2-(4-methylphenyl)-1- azavinyl](tert-butyl)]amine, by bromination/hydrolysis and acylation. In this case, benzoyl chloride (2 percent N-[N-(tert-butyl)phenylcarbonylamino](4-methyl phenyl)carboxamide), benzoic acid (80.67 percent N-[N-(tertbutyl) phenylcarbonylamino](4-methylphenyl)carboxamide) were evaluated as potential acylating agents.
- Full Text:
- Date Issued: 2008
Prevalence of Escherichia coli O157:H7 in water and meat and meat products and vegetables sold in the Eastern Cape Province of South Africa and its impact on the diarrhoeic conditions of HIV/AIDS patients
- Authors: Abong'o, Benard Omondi
- Date: 2008
- Subjects: Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Language: English
- Type: Thesis , Doctoral , PhD (Microbiology)
- Identifier: vital:11263 , http://hdl.handle.net/10353/87 , Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Description: Water and food borne Escherichia coli O157:H7 could be one of the pathogens posing high health risk to patients suffering from Acquired Immunodeficiency Syndrome (AIDS) because of its incrimination in diarrhoea cases in AIDS patients. The present study, which was conducted between March 2005 and August 2006, investigated the prevalence of E. coli O157:H7 in water, meat and meat products and vegetables and its impact on diarrhoeic conditions of confirmed and non-confirmed HIV/AIDS patients in the Amathole District in the Eastern Cape Province of South Africa. The water samples used in the study were obtained from stand pipes supplying treated drinking water to communities residing in Fort Beaufort, Alice, Dimbaza and Mdantsane whereas borehole waters were sampled from Ngwenya and Kwasaki. The meat and meat products and vegetable samples were purchased from shops, butcheries, supermarkets and open air markets in Fort Beaufort, Alice and Mdantsane. The stool swabs used in the study were obtained from HIV/AIDS and outpatient clinics at Frere Hospital in East London. A total of 180 each of water, meat and meat products and vegetable samples and another 360 stool samples were analyzed for E. coli O157:H7. Presumptive E. coli O157 was isolated from the samples by culture-based methods and confirmed using Polymerase Chain Reaction techniques. Anti-biogram as well as risk assessment were also carried out using standard methods. The viable counts of presumptive E. coli O157 for water samples ranged between 3.3 × 104 and 1.71 × 105 CFU/ml, and between 1.8 × 104 and 5.04 × 106 CFU/g for meat and meat products, whereas those for vegetables ranged between 1.3 × 103 and 1.6 × 106 CFU/g. The counts of presumptive E. coli O157 for the water and vegetable samples were not significantly different whereas those for meat and meat products were found to be significantly different (P ≤ 0.05). The prevalence rates of presumptive E coli O157 in meat and meat products was 35.55 percent (64/180), and 25.55 percent (46/180) and 21.66 percent (39/180) for water and vegetables respectively. Prevalence of presumptive E. coli O157 in the stool samples of HIV/AIDS patients was 36.39 percent (131/360), of which 56.5 percent (74/131) and 43.5 percent (57/131) were from stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Molecular analysis of representative presumptive E. coli O157 indicated that 10.29 percent (4/39) of vegetables; 14.81 percent (4/27) of water and 38.46 percent (5/13) of meat and meat products carried E. coli O157:H7. Also 36 percent (9/25) and 17.24 percent (5/29) of the stool samples were positive for E. coli O157:H7. Antimicrobial susceptibility profile revealed that all of the E. coli O157:H7 isolated from water, meat and meat products and vegetables as well as those isolated from stools of confirmed and non-confirmed HIV/AIDS patients were resistant (R) to gentamycin and erythromycin. However, 75 percent (20/27) of these isolates were resistant (R) to ampicillin and tetracycline whereas approximately 25 percent (6/27) were resistant (R) to nalidixic acid, ceftriaxone, and chloramphenicol. All the isolates (27/27) were susceptible (S) to amikacin. Probability of risk of E. coli O157:H7 infection was high for confirmed HIV/AIDS patients than for the non-confirmed HIV/AIDS patients. Estimated probability of risk of E. coli O157:H7 due to ingestion of water was 1.00 for 100 confirmed and non-confirmed HIV/AIDS patients. Risk due to meat and meat products was estimated at 0.27 and 0.20 and for vegetables at 0.21 and 0.15 per 100 confirmed and non-confirmed HIV/AIDS patients. The findings of this study predicted a possible link between E. coli O157:H7 isolated from drinking water, meat and meat products and vegetables and diarrhoeic conditions in both confirmed and non-confirmed HIV/AIDS patients, and concludes that confirmed HIV/AIDS patients can be at higher risk of contracting water and food borne E. coli O157:H7 than nonconfirmed HIV/AIDS patients. It is thus recommended that proper water treatment and food handling, maximum food and water safety and sanitation as well as personal body hygiene should be maintained, in order to prevent E. coli O157:H7 infections. Education initiatives and active surveillance of E. coli O157:H7 should be taken by all the stake-holders working directly or indirectly towards ensuring enduring sound public health.
- Full Text:
- Date Issued: 2008
- Authors: Abong'o, Benard Omondi
- Date: 2008
- Subjects: Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Language: English
- Type: Thesis , Doctoral , PhD (Microbiology)
- Identifier: vital:11263 , http://hdl.handle.net/10353/87 , Foodborne diseases , Diarrhea , Escherichia coli , HIV infections , AIDS (Disease) , Bacterial diseases
- Description: Water and food borne Escherichia coli O157:H7 could be one of the pathogens posing high health risk to patients suffering from Acquired Immunodeficiency Syndrome (AIDS) because of its incrimination in diarrhoea cases in AIDS patients. The present study, which was conducted between March 2005 and August 2006, investigated the prevalence of E. coli O157:H7 in water, meat and meat products and vegetables and its impact on diarrhoeic conditions of confirmed and non-confirmed HIV/AIDS patients in the Amathole District in the Eastern Cape Province of South Africa. The water samples used in the study were obtained from stand pipes supplying treated drinking water to communities residing in Fort Beaufort, Alice, Dimbaza and Mdantsane whereas borehole waters were sampled from Ngwenya and Kwasaki. The meat and meat products and vegetable samples were purchased from shops, butcheries, supermarkets and open air markets in Fort Beaufort, Alice and Mdantsane. The stool swabs used in the study were obtained from HIV/AIDS and outpatient clinics at Frere Hospital in East London. A total of 180 each of water, meat and meat products and vegetable samples and another 360 stool samples were analyzed for E. coli O157:H7. Presumptive E. coli O157 was isolated from the samples by culture-based methods and confirmed using Polymerase Chain Reaction techniques. Anti-biogram as well as risk assessment were also carried out using standard methods. The viable counts of presumptive E. coli O157 for water samples ranged between 3.3 × 104 and 1.71 × 105 CFU/ml, and between 1.8 × 104 and 5.04 × 106 CFU/g for meat and meat products, whereas those for vegetables ranged between 1.3 × 103 and 1.6 × 106 CFU/g. The counts of presumptive E. coli O157 for the water and vegetable samples were not significantly different whereas those for meat and meat products were found to be significantly different (P ≤ 0.05). The prevalence rates of presumptive E coli O157 in meat and meat products was 35.55 percent (64/180), and 25.55 percent (46/180) and 21.66 percent (39/180) for water and vegetables respectively. Prevalence of presumptive E. coli O157 in the stool samples of HIV/AIDS patients was 36.39 percent (131/360), of which 56.5 percent (74/131) and 43.5 percent (57/131) were from stools of confirmed and non-confirmed HIV/AIDS patients, respectively. Molecular analysis of representative presumptive E. coli O157 indicated that 10.29 percent (4/39) of vegetables; 14.81 percent (4/27) of water and 38.46 percent (5/13) of meat and meat products carried E. coli O157:H7. Also 36 percent (9/25) and 17.24 percent (5/29) of the stool samples were positive for E. coli O157:H7. Antimicrobial susceptibility profile revealed that all of the E. coli O157:H7 isolated from water, meat and meat products and vegetables as well as those isolated from stools of confirmed and non-confirmed HIV/AIDS patients were resistant (R) to gentamycin and erythromycin. However, 75 percent (20/27) of these isolates were resistant (R) to ampicillin and tetracycline whereas approximately 25 percent (6/27) were resistant (R) to nalidixic acid, ceftriaxone, and chloramphenicol. All the isolates (27/27) were susceptible (S) to amikacin. Probability of risk of E. coli O157:H7 infection was high for confirmed HIV/AIDS patients than for the non-confirmed HIV/AIDS patients. Estimated probability of risk of E. coli O157:H7 due to ingestion of water was 1.00 for 100 confirmed and non-confirmed HIV/AIDS patients. Risk due to meat and meat products was estimated at 0.27 and 0.20 and for vegetables at 0.21 and 0.15 per 100 confirmed and non-confirmed HIV/AIDS patients. The findings of this study predicted a possible link between E. coli O157:H7 isolated from drinking water, meat and meat products and vegetables and diarrhoeic conditions in both confirmed and non-confirmed HIV/AIDS patients, and concludes that confirmed HIV/AIDS patients can be at higher risk of contracting water and food borne E. coli O157:H7 than nonconfirmed HIV/AIDS patients. It is thus recommended that proper water treatment and food handling, maximum food and water safety and sanitation as well as personal body hygiene should be maintained, in order to prevent E. coli O157:H7 infections. Education initiatives and active surveillance of E. coli O157:H7 should be taken by all the stake-holders working directly or indirectly towards ensuring enduring sound public health.
- Full Text:
- Date Issued: 2008
Prevalence of ticks and tick-borne diseases in cattle on communal rangelands in the Highland Areas of the Eastern Cape Province, South Africa
- Marufu, Munyaradzi Christopher
- Authors: Marufu, Munyaradzi Christopher
- Date: 2008
- Subjects: Cattle -- Diseases , Livestock diseases -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Tick-borne diseases -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11814 , http://hdl.handle.net/10353/152 , Cattle -- Diseases , Livestock diseases -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Tick-borne diseases -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape
- Description: Surveys were conducted to compare the seasonal tick prevalence and loads, and sero-prevalence of tick-borne diseases (TBD) in Nguni and non-descript cattle on the sweet and sour communal rangelands of the Eastern Cape Province. The tick species observed on both rangeland types were Rhipicephalus appendiculatus (71.0 %), Rhipicephalus (Boophilus) species (29.2 %) and Rhipicephalus evertsi evertsi (40.2 %). Hyalomma species (19.0 %) occurred only on the sour rangeland. Tick loads were higher (P < 0.05) in the hot-wet season than in the cool-dry season. Cattle in the sweet rangeland had significantly lower (P < 0.05) tick loads than those in the sour rangeland. Rhipicephalus appendiculatus loads were lower (P < 0.05) in the indigenous Nguni than non-descript cattle in the hot-wet and post-rainy season. Hyalomma species were also significantly lower (P < 0.05) in the Nguni than non-descript cattle in all the seasons. Three TBDs were observed, namely Babesia bovis (44.6 %), Babesia bigemina (45.9 %) and Anaplasma marginale (25.6 %). All the animals were sero-negative for Ehrlichia ruminantium. Nguni cattle had lower (P < 0.05) sero-prevalence for A. marginale in the cool-dry season and B. bigemina in the cool-dry and hot-wet seasons. Cattle in the sweet rangeland had significantly lower sero-prevalence of B. bovis and B. bigemina. Infection with B. bovis and A. marginale decreased (P < 0.05) the packed cell volume. Nguni cattle were recommended for use in the integrated control of ticks and TBD in the communal areas of South Africa as they were better able to cope with tick and TBD infestations than non-descript breeds.
- Full Text:
- Date Issued: 2008
- Authors: Marufu, Munyaradzi Christopher
- Date: 2008
- Subjects: Cattle -- Diseases , Livestock diseases -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Tick-borne diseases -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11814 , http://hdl.handle.net/10353/152 , Cattle -- Diseases , Livestock diseases -- South Africa -- Eastern Cape , Rangelands -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape , Tick-borne diseases -- South Africa -- Eastern Cape , Ticks -- South Africa -- Eastern Cape
- Description: Surveys were conducted to compare the seasonal tick prevalence and loads, and sero-prevalence of tick-borne diseases (TBD) in Nguni and non-descript cattle on the sweet and sour communal rangelands of the Eastern Cape Province. The tick species observed on both rangeland types were Rhipicephalus appendiculatus (71.0 %), Rhipicephalus (Boophilus) species (29.2 %) and Rhipicephalus evertsi evertsi (40.2 %). Hyalomma species (19.0 %) occurred only on the sour rangeland. Tick loads were higher (P < 0.05) in the hot-wet season than in the cool-dry season. Cattle in the sweet rangeland had significantly lower (P < 0.05) tick loads than those in the sour rangeland. Rhipicephalus appendiculatus loads were lower (P < 0.05) in the indigenous Nguni than non-descript cattle in the hot-wet and post-rainy season. Hyalomma species were also significantly lower (P < 0.05) in the Nguni than non-descript cattle in all the seasons. Three TBDs were observed, namely Babesia bovis (44.6 %), Babesia bigemina (45.9 %) and Anaplasma marginale (25.6 %). All the animals were sero-negative for Ehrlichia ruminantium. Nguni cattle had lower (P < 0.05) sero-prevalence for A. marginale in the cool-dry season and B. bigemina in the cool-dry and hot-wet seasons. Cattle in the sweet rangeland had significantly lower sero-prevalence of B. bovis and B. bigemina. Infection with B. bovis and A. marginale decreased (P < 0.05) the packed cell volume. Nguni cattle were recommended for use in the integrated control of ticks and TBD in the communal areas of South Africa as they were better able to cope with tick and TBD infestations than non-descript breeds.
- Full Text:
- Date Issued: 2008
Process for the preparation of cis- AND trans-3,7-Dimethyl 2,6-Octadiene-1-OL from crude sulphated turpentine stream
- Sathikge, Ndavheleseni David
- Authors: Sathikge, Ndavheleseni David
- Date: 2008
- Subjects: Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10398 , http://hdl.handle.net/10948/734 , Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
- Description: As part of CSIR Biosciences’ interest in aroma chemicals, the processing of crude sulphated turpentine (CST) into high value aroma products was investigated. The primary target product, linalool, was obtained from a mixture of α- and β-pinene in four steps. It can be transformed into a wide range of high value added aroma chemicals. Isomerisation of linalool in the presence of a transition metal catalyst furnishes geraniol and nerol. The scientific work described in this report was part of a bigger project aimed at developing innovative processes to manufacture aroma, flavour & fragrance chemicals through beneficiation of industrial waste streams and other raw materials, available locally from the Forestry, Paper & Pulp industries. The evaluation of a process for the preparation of precursor aroma, flavour & fragrance compounds, in particular geraniol and nerol, from locally available raw materials and industrial waste streams, was investigated. Preparation of geraniol and nerol from linalool (ex α-pinene stream) was investigated using acids or organometallic complexes as catalysts for the corresponding isomerisation reaction. The investigation was conducted in an effort to find a less costly process utilising milder conditions than via the conventional cleavage of β-pinene to myrcene under extreme pyrolysis conditions (>650°C). The transformation of linalool to geraniol/nerol using mineral acids was found to be dominated by secondary reactions such as dehydration and cyclisation, resulting in poor product selectivities and yields. On the other hand, organometallic complexes, in particular vanadium-based complexes (e.g. (OV(OBu)3) produced satisfactory results in the preliminary assessment (conversion of 79.8 percent and selectivity of 98.3 percent). A set of statistically designed experiments was carried out on the (VO(BuO)3 + [(Bu)4N+]OH¯) catalyst system where three variables were tested, i.e. substrate concentration, temperature, and catalyst loading. The selected model for conversion was significant with the “Probability > F” being < 0.0001. The most important contributing variable to the model for conversion was temperature i.e. 83.9 percent. Temperature was still the most important variable for the selectivity response at 65.0 percent contribution level. The response surface generated for the selectivity response was flat indicating a robust method within the parameter range selected.
- Full Text:
- Date Issued: 2008
- Authors: Sathikge, Ndavheleseni David
- Date: 2008
- Subjects: Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10398 , http://hdl.handle.net/10948/734 , Turpentine , Sulfate waste liquor , Wood-pulp industry -- By-products
- Description: As part of CSIR Biosciences’ interest in aroma chemicals, the processing of crude sulphated turpentine (CST) into high value aroma products was investigated. The primary target product, linalool, was obtained from a mixture of α- and β-pinene in four steps. It can be transformed into a wide range of high value added aroma chemicals. Isomerisation of linalool in the presence of a transition metal catalyst furnishes geraniol and nerol. The scientific work described in this report was part of a bigger project aimed at developing innovative processes to manufacture aroma, flavour & fragrance chemicals through beneficiation of industrial waste streams and other raw materials, available locally from the Forestry, Paper & Pulp industries. The evaluation of a process for the preparation of precursor aroma, flavour & fragrance compounds, in particular geraniol and nerol, from locally available raw materials and industrial waste streams, was investigated. Preparation of geraniol and nerol from linalool (ex α-pinene stream) was investigated using acids or organometallic complexes as catalysts for the corresponding isomerisation reaction. The investigation was conducted in an effort to find a less costly process utilising milder conditions than via the conventional cleavage of β-pinene to myrcene under extreme pyrolysis conditions (>650°C). The transformation of linalool to geraniol/nerol using mineral acids was found to be dominated by secondary reactions such as dehydration and cyclisation, resulting in poor product selectivities and yields. On the other hand, organometallic complexes, in particular vanadium-based complexes (e.g. (OV(OBu)3) produced satisfactory results in the preliminary assessment (conversion of 79.8 percent and selectivity of 98.3 percent). A set of statistically designed experiments was carried out on the (VO(BuO)3 + [(Bu)4N+]OH¯) catalyst system where three variables were tested, i.e. substrate concentration, temperature, and catalyst loading. The selected model for conversion was significant with the “Probability > F” being < 0.0001. The most important contributing variable to the model for conversion was temperature i.e. 83.9 percent. Temperature was still the most important variable for the selectivity response at 65.0 percent contribution level. The response surface generated for the selectivity response was flat indicating a robust method within the parameter range selected.
- Full Text:
- Date Issued: 2008
Prototyping a peer-to-peer session initiation protocol user agent
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2008 , 2008-03-10
- Subjects: Computer networks , Computer network protocols -- Standards , Data transmission systems -- Standards , Peer-to-peer architecture (Computer networks) , Computer network architectures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4646 , http://hdl.handle.net/10962/d1006603 , Computer networks , Computer network protocols -- Standards , Data transmission systems -- Standards , Peer-to-peer architecture (Computer networks) , Computer network architectures
- Description: The Session Initiation Protocol (SIP) has in recent years become a popular protocol for the exchange of text, voice and video over IP networks. This thesis proposes the use of a class of structured peer to peer protocols - commonly known as Distributed Hash Tables (DHTs) - to provide a SIP overlay with services such as end-point location management and message relay, in the absence of traditional, centralised resources such as SIP proxies and registrars. A peer-to-peer layer named OverCord, which allows the interaction with any specific DHT protocol via the use of appropriate plug-ins, was designed, implemented and tested. This layer was then incorporated into a SIP user agent distributed by NIST (National Institute of Standards and Technology, USA). The modified user agent is capable of reliably establishing text, audio and video communication with similarly modified agents (peers) as well as conventional, centralized SIP overlays.
- Full Text:
- Date Issued: 2008
- Authors: Tsietsi, Mosiuoa Jeremia
- Date: 2008 , 2008-03-10
- Subjects: Computer networks , Computer network protocols -- Standards , Data transmission systems -- Standards , Peer-to-peer architecture (Computer networks) , Computer network architectures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4646 , http://hdl.handle.net/10962/d1006603 , Computer networks , Computer network protocols -- Standards , Data transmission systems -- Standards , Peer-to-peer architecture (Computer networks) , Computer network architectures
- Description: The Session Initiation Protocol (SIP) has in recent years become a popular protocol for the exchange of text, voice and video over IP networks. This thesis proposes the use of a class of structured peer to peer protocols - commonly known as Distributed Hash Tables (DHTs) - to provide a SIP overlay with services such as end-point location management and message relay, in the absence of traditional, centralised resources such as SIP proxies and registrars. A peer-to-peer layer named OverCord, which allows the interaction with any specific DHT protocol via the use of appropriate plug-ins, was designed, implemented and tested. This layer was then incorporated into a SIP user agent distributed by NIST (National Institute of Standards and Technology, USA). The modified user agent is capable of reliably establishing text, audio and video communication with similarly modified agents (peers) as well as conventional, centralized SIP overlays.
- Full Text:
- Date Issued: 2008
Purification and partial characterization of a Myofibril-Bound Serine Protease and its endogenous inhibitor from skeletal muscle of the ostrich
- Tshidino, Shonisani Cathphonia
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2008
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10330 , http://hdl.handle.net/10948/703 , Proteolytic enzymes , Ostrich products industry
- Description: The ostrich is becoming an important source of meat for humans in developed and developing countries. This study was conducted to purify and characterize myofibrilbound serine protease (MBSP) and its endogenous inhibitor (MBSPI) from skeletal muscle of the ostrich. It is well documented that MBSP is tightly bound to myofibrils and its endogenous inhibitor has been purified from the same tissue of other studied mammalian species. Literature supports an association of MBSP and its endogenous inhibitor with the degradation of myofribrillar proteins, resulting in the softening of muscle that lead to the conversion of muscle into meat with the control of the inhibitor. MBSP was successfully dissociated from washed myofibrils by 40 percent ethylene glycol at pH 8.5. Following centrifugation, MBSP was partially purified in two chromatographic steps, namely Toyopearl Super Q 650S and p-aminobenzamidine-Agarose. On the other hand, MBSPI was fractionated from the sarcoplasmic fraction using 75 percent ammonium sulfate saturation, followed by centrifugation and partially purified by three chromatographic steps, namely Toyopearl Super Q 650S, Superdex 200 and HiTrap SP HR. Ostrich MBSP was physicochemically and kinetically characterized, while MBSPI was only physicochemically characterized. Ostrich MBSP revealed an Mr of 21 kDa, cleaving synthetic fluorogenic substrates specifically at the carboxyl side of arginine residues. Optimum pH and temperature of ostrich MBSP were 8.0 and 40˚C, respectively. Kinetic parameters (Km and Vmax values) were calculated from Lineweaver-Burk plots. The characteristics of ostrich MBSP were compared to the values obtained for commercial bovine trypsin in this study, as well as that obtained for MBSP from various fish species and mouse. The results suggest that ostrich MBSP is a trypsin-like serine protease, thereby confirming the existence of MBSP in ostrich skeletal muscle. Partially purified ostrich MBSPI (Mr 17 kDa) (one form) shares 100 percent identity to myoglobin from the same species, while 2 other forms of MBSPI (Mr values of 35 and 36 kDa) exhibited high sequence identity to glyceraldehyde 3- phosphate dehydrogenase (GAPDH) (76 percent) from human and rat.
- Full Text:
- Date Issued: 2008
- Authors: Tshidino, Shonisani Cathphonia
- Date: 2008
- Subjects: Proteolytic enzymes , Ostrich products industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10330 , http://hdl.handle.net/10948/703 , Proteolytic enzymes , Ostrich products industry
- Description: The ostrich is becoming an important source of meat for humans in developed and developing countries. This study was conducted to purify and characterize myofibrilbound serine protease (MBSP) and its endogenous inhibitor (MBSPI) from skeletal muscle of the ostrich. It is well documented that MBSP is tightly bound to myofibrils and its endogenous inhibitor has been purified from the same tissue of other studied mammalian species. Literature supports an association of MBSP and its endogenous inhibitor with the degradation of myofribrillar proteins, resulting in the softening of muscle that lead to the conversion of muscle into meat with the control of the inhibitor. MBSP was successfully dissociated from washed myofibrils by 40 percent ethylene glycol at pH 8.5. Following centrifugation, MBSP was partially purified in two chromatographic steps, namely Toyopearl Super Q 650S and p-aminobenzamidine-Agarose. On the other hand, MBSPI was fractionated from the sarcoplasmic fraction using 75 percent ammonium sulfate saturation, followed by centrifugation and partially purified by three chromatographic steps, namely Toyopearl Super Q 650S, Superdex 200 and HiTrap SP HR. Ostrich MBSP was physicochemically and kinetically characterized, while MBSPI was only physicochemically characterized. Ostrich MBSP revealed an Mr of 21 kDa, cleaving synthetic fluorogenic substrates specifically at the carboxyl side of arginine residues. Optimum pH and temperature of ostrich MBSP were 8.0 and 40˚C, respectively. Kinetic parameters (Km and Vmax values) were calculated from Lineweaver-Burk plots. The characteristics of ostrich MBSP were compared to the values obtained for commercial bovine trypsin in this study, as well as that obtained for MBSP from various fish species and mouse. The results suggest that ostrich MBSP is a trypsin-like serine protease, thereby confirming the existence of MBSP in ostrich skeletal muscle. Partially purified ostrich MBSPI (Mr 17 kDa) (one form) shares 100 percent identity to myoglobin from the same species, while 2 other forms of MBSPI (Mr values of 35 and 36 kDa) exhibited high sequence identity to glyceraldehyde 3- phosphate dehydrogenase (GAPDH) (76 percent) from human and rat.
- Full Text:
- Date Issued: 2008
Purification, characterisation and application of inulinase and transferase enzymes in the production of fructose and oligosaccharides
- Authors: Mutanda, Taurai
- Date: 2008
- Subjects: Fructose Transferases Oligosaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4448 , http://hdl.handle.net/10962/d1007734
- Description: Inulin hydrolysis can occur as a result of the action of exoinulinases and endoinulinases acting alone or synergistically. Exoinulinases cleave the non-reducing β-(2, I) end of inulin releasing fructose while endoinulinases act on the internal linkages randomly to release inulotrioses (F₃), inulotetraoses (F₄) and inulopentaoses (F₅) as major products. Fructosyltransferases act by cleaving a sucrose molecule and then transferring the liberated fructose molecule to an acceptor molecule such as sucrose or another oligosaccharide to elongate the short chain fructooligosaccharide. The production of high yields of oligosaccharides of specific chain length from simple raw materials such as inulin and sucrose is a challenge. Oligosaccharides of chain length up to degree of polymerisation (DP) 5 and fructose were produced using preparations of three commercial microbial enzymes. Production of these novel oligosaccharides was achieved by employing response surface methodology (RSM) with central composite experimental design (CCD) for optimising product yield. Using a crude Novozyme 960 endoinulinase preparation isolated from Aspergillus niger, the following conditions gave a high inulooligosaccharide (lOS) yield, temperature (60 ºC), 150 g/L inulin concentration, 48 h incubation; pH 6.0 and enzyme dosage of 60 U/ml. Under these conditions, inulotrioses (70.3 mM), inulotetraoses (38.8 mM), and inulopentaoses, (3.5 mM) were produced. Response surface regression predicted similar product levels under similar conditions. The crude endoinulinase was purified through a three step purification procedure with a yield of 1.11 % and 3.5 fold purification. The molecular weight of this endoinulinase was estimated to be 68 .1 kDa by SDS-PAGE and its endoinulinase nature was confirmed by native PAGE. The purified endoinulinase was more efficient in production of lOS than the crude endoinulinase preparation. The purified endoinulinase demonstrated a high affinity for the inulin substrate (Km[subscript] 3.53 mM, Vmax[subscript] 666.67 μmol/min/ml). Pectinex Ultra SP-L, a commercial crude enzyme preparation isolated from Aspergillus aculeatus is a cocktail of several enzymes including a fructosyltransferase. The crude enzyme showed both transfructosylation and hydrolytic activity in 200 to 600 g/L sucrose. The main fructooligosaccharides produced from sucrose were l-kestose (GF₂), nystose (GF₃) and fructofuranosyl nystose (GF₄). After the first RSM, with the coded independent variables of temperature, incubation time, pH and sucrose concentration, the highest levels of GF₂, was 68.61 mM, under sucrose concentration 600 g/L, temperature 60°C, enzyme dosage 20 U/ml , pH 5.6, after 4 h incubation. A sucrose concentration of 400 g/L favoured the synthesis of high levels of GF₃ and GF₄. In the second RSM the maximal yields of GF₂, GF₃ and GF₄ were 152.07 mM, 131.38 mM and 43.99 mM respectively. A purified fructosyltransferase did not synthesise GF₄. Ammonium ions were demonstrated to enhance the yield of FOS. A mixture of glucose and fructose was used as substrate for FOS synthesis and no FOS were formed. Glucose was shown to be an end product inhibitor of the fructosyltransferase and therefore hinders the formation of high FOS yield. Fructozyme, isolated from Aspergillus ficuum is a mixture of exo and endoinulinases with the former being predominant was used for fructose production from inulin hydrolysis. The exoinulinase was purified to electrophoretic homogeneity by a three step purification procedure. The molecular weight of the enzyme was estimated to be 53 kDa with a 2 I % yield and 4.2-fold. Response surface regression was used to predict the maximum fructose levels achievable under the combinations of temperature, enzyme dosage and incubation time. A reaction time (48 h), enzyme dosage (100 U/ml) and inulin concentration (150 g/l) at pH 5.0 at 50°C gave higher fructose levels (106.6 mg/ml) using crude exoinulinase as compared to 98.43 mg/ml using the purified exoinulinase. These findings indicate that higher levels of fructose require longer incubation periods and higher inulin substrate concentrations with higher enzyme dosage. The crude exoinulinase preparation gave fairly higher levels of fructose than the purified exoinulinase and this is due to the presence of other hydrolytic enzymes in the crude preparation. The conditions established by RSM and CCO were adequate in producing high yield of oligosaccharides and fructose and can therefore be applied for their industrial production since they are in high demand due to their health benefits as prebiotics.
- Full Text:
- Date Issued: 2008
- Authors: Mutanda, Taurai
- Date: 2008
- Subjects: Fructose Transferases Oligosaccharides
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4448 , http://hdl.handle.net/10962/d1007734
- Description: Inulin hydrolysis can occur as a result of the action of exoinulinases and endoinulinases acting alone or synergistically. Exoinulinases cleave the non-reducing β-(2, I) end of inulin releasing fructose while endoinulinases act on the internal linkages randomly to release inulotrioses (F₃), inulotetraoses (F₄) and inulopentaoses (F₅) as major products. Fructosyltransferases act by cleaving a sucrose molecule and then transferring the liberated fructose molecule to an acceptor molecule such as sucrose or another oligosaccharide to elongate the short chain fructooligosaccharide. The production of high yields of oligosaccharides of specific chain length from simple raw materials such as inulin and sucrose is a challenge. Oligosaccharides of chain length up to degree of polymerisation (DP) 5 and fructose were produced using preparations of three commercial microbial enzymes. Production of these novel oligosaccharides was achieved by employing response surface methodology (RSM) with central composite experimental design (CCD) for optimising product yield. Using a crude Novozyme 960 endoinulinase preparation isolated from Aspergillus niger, the following conditions gave a high inulooligosaccharide (lOS) yield, temperature (60 ºC), 150 g/L inulin concentration, 48 h incubation; pH 6.0 and enzyme dosage of 60 U/ml. Under these conditions, inulotrioses (70.3 mM), inulotetraoses (38.8 mM), and inulopentaoses, (3.5 mM) were produced. Response surface regression predicted similar product levels under similar conditions. The crude endoinulinase was purified through a three step purification procedure with a yield of 1.11 % and 3.5 fold purification. The molecular weight of this endoinulinase was estimated to be 68 .1 kDa by SDS-PAGE and its endoinulinase nature was confirmed by native PAGE. The purified endoinulinase was more efficient in production of lOS than the crude endoinulinase preparation. The purified endoinulinase demonstrated a high affinity for the inulin substrate (Km[subscript] 3.53 mM, Vmax[subscript] 666.67 μmol/min/ml). Pectinex Ultra SP-L, a commercial crude enzyme preparation isolated from Aspergillus aculeatus is a cocktail of several enzymes including a fructosyltransferase. The crude enzyme showed both transfructosylation and hydrolytic activity in 200 to 600 g/L sucrose. The main fructooligosaccharides produced from sucrose were l-kestose (GF₂), nystose (GF₃) and fructofuranosyl nystose (GF₄). After the first RSM, with the coded independent variables of temperature, incubation time, pH and sucrose concentration, the highest levels of GF₂, was 68.61 mM, under sucrose concentration 600 g/L, temperature 60°C, enzyme dosage 20 U/ml , pH 5.6, after 4 h incubation. A sucrose concentration of 400 g/L favoured the synthesis of high levels of GF₃ and GF₄. In the second RSM the maximal yields of GF₂, GF₃ and GF₄ were 152.07 mM, 131.38 mM and 43.99 mM respectively. A purified fructosyltransferase did not synthesise GF₄. Ammonium ions were demonstrated to enhance the yield of FOS. A mixture of glucose and fructose was used as substrate for FOS synthesis and no FOS were formed. Glucose was shown to be an end product inhibitor of the fructosyltransferase and therefore hinders the formation of high FOS yield. Fructozyme, isolated from Aspergillus ficuum is a mixture of exo and endoinulinases with the former being predominant was used for fructose production from inulin hydrolysis. The exoinulinase was purified to electrophoretic homogeneity by a three step purification procedure. The molecular weight of the enzyme was estimated to be 53 kDa with a 2 I % yield and 4.2-fold. Response surface regression was used to predict the maximum fructose levels achievable under the combinations of temperature, enzyme dosage and incubation time. A reaction time (48 h), enzyme dosage (100 U/ml) and inulin concentration (150 g/l) at pH 5.0 at 50°C gave higher fructose levels (106.6 mg/ml) using crude exoinulinase as compared to 98.43 mg/ml using the purified exoinulinase. These findings indicate that higher levels of fructose require longer incubation periods and higher inulin substrate concentrations with higher enzyme dosage. The crude exoinulinase preparation gave fairly higher levels of fructose than the purified exoinulinase and this is due to the presence of other hydrolytic enzymes in the crude preparation. The conditions established by RSM and CCO were adequate in producing high yield of oligosaccharides and fructose and can therefore be applied for their industrial production since they are in high demand due to their health benefits as prebiotics.
- Full Text:
- Date Issued: 2008
Queens, pseudoqueens and laying workers reproductive competition in the Cape Honeybee (Apis mellifera capensis Eschscholtz)
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
- Authors: Muerrle, Thomas Martin
- Date: 2008
- Subjects: Honeybee Honeybee -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5750 , http://hdl.handle.net/10962/d1005437
- Description: In honeybees (Apis mellifera L.) the queen monopolises reproduction. However, especially after queen loss, workers can lay eggs, but are unable to mate. They produce haploid male offspring (drones) from unfertilised eggs via arrhenotokous parthenogenesis. In contrast, workers of the honeybee subspecies Apis mellifera capensis Eschscholtz typically produce diploid female offspring from unfertilised eggs thelytokously. After queen loss and without queen-derived brood A. m. capensis colonies can successfully requeen from worker-derived brood. This, however, is a relatively rare event in wild populations. Moreover, workerderived queens were described to be smaller, more worker-like and reproductively inferior. On the other hand, the fixation of the thelytokous trait relies mainly on sufficient numbers of viable drones produced by worker-derived queens. Small numbers of reproductively inferior worker-derived queens in A. m. capensis populations would be clearly counterintuitive. It is therefore necessary to quantify the significance of worker-dependant queen rearing pathways on the individual (queen) and on population level.Reproductive inferiority of worker-derived queens could not be confirmed on the individual (queen) level when comparing parameters indicating potential reproductive success of queen- and worker-derived queens. Queen- and worker-derived queens clearly showed a congruent range of reproductive performance. In queen rearing preference tests, increased acceptance of worker-derived female larvae was exactly counterbalanced by increased mortality, resulting in an equal number of eclosing virgin queens from an equal number of grafts in both test groups. Larval survival and successful eclosion is a prerequisite for a queen’s reproductive success. I found no difference in eclosion success for queen- and worker-derived virgin queens, indicating a similar potential for reproductive success in both queen types. Assessments of the developmental patterns of colonies headed by both queen and worker-derived queens in long-term experiments revealed no significant differences in reproductive success. Colonies headed by queen-derived queens and colonies headed by worker-derived queens could not be separated when comparing the different developmental pathways observed or from differences in worker-force. Reproductive dominance in A. m. capensis appeared tobe determined by a function of relative compositional and absolute quantitative pheromonal patterns, where individuals, which produce compositionally most queen-like blends in highest quantities, occupy top positions. Queen- and worker-derived virgin queens occupied intermediate positions between pseudoqueens and mated queens. However, no significant differences between the pheromonal status of queen- and worker-derived virgin queens were observed, suggesting a similar range of reproductive dominance for both queen types. In behavioural bioassays queen- and worker-derived virgin queens appeared to be similarly attractive to clustering workers and to drones in a drone congregation area, indicating no differences in potential reproductive success for queens from both origins for those parameters. The significant influence of the queen substance 9-ODA on attractiveness to workers and drones was confirmed. Rare requeening events from worker-derived female brood in queenless A.m. capensis do not satisfactorily explain the fixation of the thelytokous trait at a population level. I observed A. m. capensis worker ovipositing into empty artificial queen cell cups in queen-right colonies. The queen was confined behind a queen excluder grid in a separate compartment of the colony, to imitate reduced pheromonal flow, similar to swarming or superseding colonies. Eggs oviposited by workers in artificial queen cell cups were readily accepted for queen rearing and successful eclosion of viable virgin queens was observed. Consequently I suggested an alternative worker-dependant reproductive pathway in A. m. capensis, which was never described before: In swarming or superseding queenright colonies, laying workers may directly compete with the queen for reproductive success by ovipositing (instead of the queen) into natural queen cell cups. At a population level this reproductive tactic may result in large numbers of worker-derived queens of high reproductive quality in natural populations of A. m. capensis.
- Full Text:
- Date Issued: 2008
Radio Frequency Identification (RFID) adoption in the South African retail sector: an investigation of perceptions held by members of the retail sector regarding the adoption constraints
- Authors: Liu, Haidi
- Date: 2008
- Subjects: Radio frequency identification systems , Retail trade -- South Africa , Business logistics -- Management -- South Africa , Retail trade -- Employees -- South Africa , Retail trade -- Technological innovations , Radio waves , Consumer profiling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1144 , http://hdl.handle.net/10962/d1002774 , Radio frequency identification systems , Retail trade -- South Africa , Business logistics -- Management -- South Africa , Retail trade -- Employees -- South Africa , Retail trade -- Technological innovations , Radio waves , Consumer profiling
- Description: Radio Frequency Identification (RFID) technology is a ethod of identifying unique items using radio waves that communicate between RFID tags and readers without line-of-sight readability. RFID technology provides great potential in many industries and a wide spectrum of possible uses. Areas of application include person identification, logistics, pharmaceutical, access control, security guard monitoring and asset management. One of the areas where RFID is being used and where it promises excellent results is the retail industry. While RFID systems have the potential to revolutionise the way products and goods are tracked and traced in the retail supply chain, barriers to its widespread adoption exist: for example; technical constraints, return on investment constraints, a lack of awareness and education and as well as privacy and security issues. The research aims to identify the barriers to the adoption of RFID and to investigate the perceptions of RFID held by members of the retail sector in South Africa (SA). Current research and available literature are used to identify RFID adoption barriers and a conceptual framework on this subject is proposed, which is then verified by SA retailers’ perceptions, established by means of a survey. Initial barriers to widespread adoption include a shortage in skills, a lack of standards, high costs associated with RFID devices, the difficulty of integrating with current legacy systems, and a lack of familiarity with the system. Finally, an enhanced framework is proposed, describing RFID adoption barriers within the South African retail sector. In summary, the framework is an outline of the barriers impacting RFID adoption in the SA retail sector that need to be considered and addressed. The framework identifies six categories of RFID adoption barriers, with each category containing two or more barriers relating to that particular category. These categories are Technological, Cost and return on investment, Privacy and security, Implementation, Organisational factors and People.
- Full Text:
- Date Issued: 2008
- Authors: Liu, Haidi
- Date: 2008
- Subjects: Radio frequency identification systems , Retail trade -- South Africa , Business logistics -- Management -- South Africa , Retail trade -- Employees -- South Africa , Retail trade -- Technological innovations , Radio waves , Consumer profiling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1144 , http://hdl.handle.net/10962/d1002774 , Radio frequency identification systems , Retail trade -- South Africa , Business logistics -- Management -- South Africa , Retail trade -- Employees -- South Africa , Retail trade -- Technological innovations , Radio waves , Consumer profiling
- Description: Radio Frequency Identification (RFID) technology is a ethod of identifying unique items using radio waves that communicate between RFID tags and readers without line-of-sight readability. RFID technology provides great potential in many industries and a wide spectrum of possible uses. Areas of application include person identification, logistics, pharmaceutical, access control, security guard monitoring and asset management. One of the areas where RFID is being used and where it promises excellent results is the retail industry. While RFID systems have the potential to revolutionise the way products and goods are tracked and traced in the retail supply chain, barriers to its widespread adoption exist: for example; technical constraints, return on investment constraints, a lack of awareness and education and as well as privacy and security issues. The research aims to identify the barriers to the adoption of RFID and to investigate the perceptions of RFID held by members of the retail sector in South Africa (SA). Current research and available literature are used to identify RFID adoption barriers and a conceptual framework on this subject is proposed, which is then verified by SA retailers’ perceptions, established by means of a survey. Initial barriers to widespread adoption include a shortage in skills, a lack of standards, high costs associated with RFID devices, the difficulty of integrating with current legacy systems, and a lack of familiarity with the system. Finally, an enhanced framework is proposed, describing RFID adoption barriers within the South African retail sector. In summary, the framework is an outline of the barriers impacting RFID adoption in the SA retail sector that need to be considered and addressed. The framework identifies six categories of RFID adoption barriers, with each category containing two or more barriers relating to that particular category. These categories are Technological, Cost and return on investment, Privacy and security, Implementation, Organisational factors and People.
- Full Text:
- Date Issued: 2008
Ray Charles: a psychobiographical study
- Authors: Biggs, Ilze
- Date: 2008
- Subjects: Charles, Ray, 1930-2004 Psychology -- Biographical methods -- Case studies Jazz singers -- Biography Blind entertainers -- Psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2933 , http://hdl.handle.net/10962/d1002442
- Description: Psychobiography is the formulation of an individual's narrative according to a psychological theory. Psychobiographical researchers face a number of challenges. One pertinent challenge is the limited amount of psychobiographical research conducted at academic institutions, including South Africa. Although a number of studies had been completed in the past decade, the impact of psychobiographical research remains negligible. Although much has been written about Ray Charles, none of the existing literature adopted a specific psychological focus. Charles developed from a young boy in a poverty stricken, racially segregated society into an exceptionally successful musician who worked productively until he died at the age of 73. He was selected as the subject on the basis of interest value, uniqueness and significance of life achievements. The primary aim of this study was to explore and describe the development of Charles according to Levinson's (Levinson, et. ai, 1978) theoretical framework. Levinson's theory of adult development identifies and describes the important changes that occur throughout the lifespan of an individual. A secondary aim was to provide an understanding of Charles within the social, economic and historical context in which he lived. The data collection and analysis was conducted according to Yin's (2003) 'analytic generalization'. The data was analysed according to three linked sub-processes proposed by Huberman and Miles (1994).
- Full Text:
- Date Issued: 2008
- Authors: Biggs, Ilze
- Date: 2008
- Subjects: Charles, Ray, 1930-2004 Psychology -- Biographical methods -- Case studies Jazz singers -- Biography Blind entertainers -- Psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2933 , http://hdl.handle.net/10962/d1002442
- Description: Psychobiography is the formulation of an individual's narrative according to a psychological theory. Psychobiographical researchers face a number of challenges. One pertinent challenge is the limited amount of psychobiographical research conducted at academic institutions, including South Africa. Although a number of studies had been completed in the past decade, the impact of psychobiographical research remains negligible. Although much has been written about Ray Charles, none of the existing literature adopted a specific psychological focus. Charles developed from a young boy in a poverty stricken, racially segregated society into an exceptionally successful musician who worked productively until he died at the age of 73. He was selected as the subject on the basis of interest value, uniqueness and significance of life achievements. The primary aim of this study was to explore and describe the development of Charles according to Levinson's (Levinson, et. ai, 1978) theoretical framework. Levinson's theory of adult development identifies and describes the important changes that occur throughout the lifespan of an individual. A secondary aim was to provide an understanding of Charles within the social, economic and historical context in which he lived. The data collection and analysis was conducted according to Yin's (2003) 'analytic generalization'. The data was analysed according to three linked sub-processes proposed by Huberman and Miles (1994).
- Full Text:
- Date Issued: 2008
Re-evaluating the law of vicarious liability in South Africa
- Authors: Small, Jonathan Noel
- Date: 2008
- Subjects: Independent contractors -- South Africa Law -- South Africa Torts -- South Africa Courts -- South Africa Jurisdiction -- South Africa International law -- South Africa Roman law Roman-Dutch law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3704 , http://hdl.handle.net/10962/d1004771
- Description: This thesis is an analysis of the law of vicarious liability and its application within the legal framework of delict in South Africa. A brief overview of the historical development of this branch of law is given, with reference to the influences of Roman, Roman-Dutch and English law. That is followed by an exposition of the 'modem' interpretation of vicarious liability as applied in South African courts, highlighting apparent inconsistencies and the need for reform in what has become a persistently controversial area of law. Specific attention is paid to the so-called 'course and scope enquiry' and to the enduring difficulties associated with attributing liability to employers for the deliberate wrongful conduct of their employees. It is argued that the courts have yet to reach consensus on a general principle capable of being applied to the facts of so-called 'deviation cases', and that consequently the legal divergence on these matters gives rise to uncertainty and concern. It is submitted that the way in which the traditional test for vicarious liability is currently applied fails to give true effect to the policy considerations upon which this branch of law is founded. By way of comparison with the South African position, a detailed account of the law of vicarious liability in comparable foreign jurisdictions is given, with emphasis placed on recent developments in England and the British Commonwealth. The study then moves to an analysis of the various policy considerations behind vicarious liability, with particular attention being paid to the role of risk-related liability and the role of risk-assumption in the 'course and scope' enquiry. A comparative analysis follows, highlighting differences between the approaches of the foreign jurisdictions and that taken by the South African courts. The work concludes with a proposal that the South African courts should broaden the scope of vicarious liability and opt for a model similar to that which has recently been adopted in Canada.
- Full Text:
- Date Issued: 2008
- Authors: Small, Jonathan Noel
- Date: 2008
- Subjects: Independent contractors -- South Africa Law -- South Africa Torts -- South Africa Courts -- South Africa Jurisdiction -- South Africa International law -- South Africa Roman law Roman-Dutch law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3704 , http://hdl.handle.net/10962/d1004771
- Description: This thesis is an analysis of the law of vicarious liability and its application within the legal framework of delict in South Africa. A brief overview of the historical development of this branch of law is given, with reference to the influences of Roman, Roman-Dutch and English law. That is followed by an exposition of the 'modem' interpretation of vicarious liability as applied in South African courts, highlighting apparent inconsistencies and the need for reform in what has become a persistently controversial area of law. Specific attention is paid to the so-called 'course and scope enquiry' and to the enduring difficulties associated with attributing liability to employers for the deliberate wrongful conduct of their employees. It is argued that the courts have yet to reach consensus on a general principle capable of being applied to the facts of so-called 'deviation cases', and that consequently the legal divergence on these matters gives rise to uncertainty and concern. It is submitted that the way in which the traditional test for vicarious liability is currently applied fails to give true effect to the policy considerations upon which this branch of law is founded. By way of comparison with the South African position, a detailed account of the law of vicarious liability in comparable foreign jurisdictions is given, with emphasis placed on recent developments in England and the British Commonwealth. The study then moves to an analysis of the various policy considerations behind vicarious liability, with particular attention being paid to the role of risk-related liability and the role of risk-assumption in the 'course and scope' enquiry. A comparative analysis follows, highlighting differences between the approaches of the foreign jurisdictions and that taken by the South African courts. The work concludes with a proposal that the South African courts should broaden the scope of vicarious liability and opt for a model similar to that which has recently been adopted in Canada.
- Full Text:
- Date Issued: 2008
Reading nonsense : a journey through the writing of Edward Lear
- Authors: Pendlebury, Kathleen Sarah
- Date: 2008
- Subjects: Lear, Edward, 1812-1888 Lear, Edward, 1812-1888 Criticism and interpretation English poetry -- 19th century -- Criticism and interpretation
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2206 , http://hdl.handle.net/10962/d1002249
- Description: In this thesis I have addressed some of the problems that have arisen in critical approaches to the nonsense works of Edward Lear from the late nineteenth century. I have entitled it “Reading Nonsense” because my central concern is with how best to apprehend the paradoxes inherent in literary nonsense, which inevitably raises interpretative questions. Because nonsense is a “basic type of communication” whose essence is “unresolved tension between [the] presence and absence of meaning” (Tigges, Anatomy 51), we are called upon either to “make sense of” that which claims to offer up no meaning or to surrender ourselves to meaninglessness. Broadly, critical approaches to nonsense fall into two classes: those that maintain that nonsense is not, in fact, “not sense”, but rather a kind of symbolic language that can be reconciled into meaning; and those which uphold the nonsensicality of nonsense, maintaining that certain ambiguities and paradoxes cannot be accounted for, and it is inappropriate to try to do so. In addition, Lear’s texts are situated in various traditions of writing for children and adults and in the distinctive setting of the Victorian era; and these cultural and literary influences play an important role in the interpretation and misinterpretation of nonsense. My first chapter comprises a mise en scène of the genre of literary nonsense; while in Chapter 2 I turn to the cultural backdrop of Lear’s nonsense in particular, and examine one of the claims frequently made in nonsense criticism: that Lear’s literary nonsense is distinctively “Victorian”. Chapter 3, “How to Read a Learian Limerick”, rests on the exegesis of nonsense that appears in Chapter 1, for here I propose a technique for reading Lear’s limericks that preserves both their “sensical” and nonsensical elements in contrast to critical analyses that attempt to reconcile the nonsense into a code. In Chapter 4 I examine Lear’s songs from the critical perspectives of nonsense and of romanticism. Finally, in conclusion, I consider the role and significance of humour in nonsense, and gesture towards further possible explorations, including in the appendix my essay on the nonsense poetry of South African writer Philip de Vos.
- Full Text:
- Date Issued: 2008
- Authors: Pendlebury, Kathleen Sarah
- Date: 2008
- Subjects: Lear, Edward, 1812-1888 Lear, Edward, 1812-1888 Criticism and interpretation English poetry -- 19th century -- Criticism and interpretation
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2206 , http://hdl.handle.net/10962/d1002249
- Description: In this thesis I have addressed some of the problems that have arisen in critical approaches to the nonsense works of Edward Lear from the late nineteenth century. I have entitled it “Reading Nonsense” because my central concern is with how best to apprehend the paradoxes inherent in literary nonsense, which inevitably raises interpretative questions. Because nonsense is a “basic type of communication” whose essence is “unresolved tension between [the] presence and absence of meaning” (Tigges, Anatomy 51), we are called upon either to “make sense of” that which claims to offer up no meaning or to surrender ourselves to meaninglessness. Broadly, critical approaches to nonsense fall into two classes: those that maintain that nonsense is not, in fact, “not sense”, but rather a kind of symbolic language that can be reconciled into meaning; and those which uphold the nonsensicality of nonsense, maintaining that certain ambiguities and paradoxes cannot be accounted for, and it is inappropriate to try to do so. In addition, Lear’s texts are situated in various traditions of writing for children and adults and in the distinctive setting of the Victorian era; and these cultural and literary influences play an important role in the interpretation and misinterpretation of nonsense. My first chapter comprises a mise en scène of the genre of literary nonsense; while in Chapter 2 I turn to the cultural backdrop of Lear’s nonsense in particular, and examine one of the claims frequently made in nonsense criticism: that Lear’s literary nonsense is distinctively “Victorian”. Chapter 3, “How to Read a Learian Limerick”, rests on the exegesis of nonsense that appears in Chapter 1, for here I propose a technique for reading Lear’s limericks that preserves both their “sensical” and nonsensical elements in contrast to critical analyses that attempt to reconcile the nonsense into a code. In Chapter 4 I examine Lear’s songs from the critical perspectives of nonsense and of romanticism. Finally, in conclusion, I consider the role and significance of humour in nonsense, and gesture towards further possible explorations, including in the appendix my essay on the nonsense poetry of South African writer Philip de Vos.
- Full Text:
- Date Issued: 2008
Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network
- Authors: Opperman, B D L
- Date: 2008
- Subjects: Global Positioning System Global Positioning System -- Data processing Electrons -- South Africa Ionosphere -- South Africa Ionospheric radio wave propagation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5487 , http://hdl.handle.net/10962/d1005273
- Description: Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.
- Full Text:
- Date Issued: 2008
- Authors: Opperman, B D L
- Date: 2008
- Subjects: Global Positioning System Global Positioning System -- Data processing Electrons -- South Africa Ionosphere -- South Africa Ionospheric radio wave propagation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5487 , http://hdl.handle.net/10962/d1005273
- Description: Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.
- Full Text:
- Date Issued: 2008
Reflective accounts of childhood inter-species experiences in a Southern-African context: a phenomenological-hermeneutic exploration
- Authors: Rump, Samantha
- Date: 2008
- Subjects: Child psychology -- South Africa Child development -- South Africa Human-animal relationships -- South Africa Children and animals -- South Africa Animal psychology -- South Africa Hermeneutics Phenomenology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3045 , http://hdl.handle.net/10962/d1002554
- Description: The aims of this research were to describe in rich phenomenological detail the recollected childhood experiences described by three South African adults of growing up with animals in the context of a traditionally African cultural perspective in South Africa; as well as to document the emotional, physical and social effects of inter-species relationships as described by these participants, in order to explore and situate these experiences in relation to broad international perspectives on the contribution of animals to human development. The question of how these described experiences correlate with broad international perspectives on the contribution of animals to human development comprised the hermeneutic of the study. Here it was found that the experiences of these South African individuals were generally in keeping with the trends found in the literature. Participants attributed to their childhood relationships with animals a variety of benefits. These benefits occur on a range of levels, from the physical to the cognitive, and the psychosocial. The emotional attachment of the participants to animals with whom they had interacted in childhood correlated with the nature of interspecies relationships as anticipated by the literature. Cultural differences in the conceptualisation of inter-species relationships, between western and traditionally African ideologies, appeared to influence the moral and ethical positions assumed by the participants, while the subjective nature of the described attachment between participants and animals remains qualitatively similar across cultures, when explored in relation to international research. The similarities between the experiences of the participants and international research findings lend credence to Wilson’s hypothesis that all human beings are potentially able to connect in deep and profound ways with their natural environment, and that this connection contributes to the development of social and cognitive skills, as well as constituting emotional support and stability. The research concludes with an examination of its own limitations and suggestions are made for further research.
- Full Text:
- Date Issued: 2008
- Authors: Rump, Samantha
- Date: 2008
- Subjects: Child psychology -- South Africa Child development -- South Africa Human-animal relationships -- South Africa Children and animals -- South Africa Animal psychology -- South Africa Hermeneutics Phenomenology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3045 , http://hdl.handle.net/10962/d1002554
- Description: The aims of this research were to describe in rich phenomenological detail the recollected childhood experiences described by three South African adults of growing up with animals in the context of a traditionally African cultural perspective in South Africa; as well as to document the emotional, physical and social effects of inter-species relationships as described by these participants, in order to explore and situate these experiences in relation to broad international perspectives on the contribution of animals to human development. The question of how these described experiences correlate with broad international perspectives on the contribution of animals to human development comprised the hermeneutic of the study. Here it was found that the experiences of these South African individuals were generally in keeping with the trends found in the literature. Participants attributed to their childhood relationships with animals a variety of benefits. These benefits occur on a range of levels, from the physical to the cognitive, and the psychosocial. The emotional attachment of the participants to animals with whom they had interacted in childhood correlated with the nature of interspecies relationships as anticipated by the literature. Cultural differences in the conceptualisation of inter-species relationships, between western and traditionally African ideologies, appeared to influence the moral and ethical positions assumed by the participants, while the subjective nature of the described attachment between participants and animals remains qualitatively similar across cultures, when explored in relation to international research. The similarities between the experiences of the participants and international research findings lend credence to Wilson’s hypothesis that all human beings are potentially able to connect in deep and profound ways with their natural environment, and that this connection contributes to the development of social and cognitive skills, as well as constituting emotional support and stability. The research concludes with an examination of its own limitations and suggestions are made for further research.
- Full Text:
- Date Issued: 2008
Removal and photocatalysis of 4-Nitrophenol using metallophthalocyanines
- Authors: Marais, Eloise Ann
- Date: 2008
- Subjects: Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4343 , http://hdl.handle.net/10962/d1005005 , Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Description: Photodegradation of 4-nitrophenol (4-Np) in the presence of water-soluble zinc phthalocyanines and water-insoluble metallophthalocyanines is reported. The water-soluble phthalocyanines employed include zinc tetrasulphophthalocyanine (ZnPcS[subscript 4]), zinc octacarboxyphthalocyanine (ZnPc(COOH)[subscript 8]) and a sulphonated ZnPc containing a mixture of differently sulphonated derivatives (ZnPcS[subscript mix]), while the water-insoluble phthalocyanines used include unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring-substituted zinc tetranitro (ZnPc(NO[subscript 2])[subscript 4]), zinc tetraamino (ZnPc(NH[subscript 2])[subscript 4]), zinc hexadecafluoro (ZnPcF[subscript 16]) and zinc hexadecachloro (ZnPcCl[subscript 16]) phthalocyanines. The most effective water-soluble photocatalyst is ZnPcS[subscript mix] in terms of the high quantum yield obtained for 4-Np degradation (Φ[subscript 4-Np]) as well as its photostability. While ZnPc(COOH)[subscript 8] has the highest Φ[subscript 4-Np] value relative to the other water-soluble complexes, it degrades readily during photocatalysis. The Φ[subscript 4-Np] values were closely related to the singlet oxygen quantum yields Φ[subscript Δ] and hence aggregation. The rate constants for the reaction with 4-Np were kr = 0.67 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPcS[subscript mix] and 7.7 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPc(COOH)[subscript 8]. ClAlPc is the most effective photocatalyst relative to the other heterogeneous photocatalysts for the phototransformation of 4-Np, with 89 ± 8.4 % degradation of 4-Np achieved after 100 min. The least effective catalysts were ZnPcCl[subscript 16] and MgPc. The final products of the photocatalysis of 4-Np in the presence of the homogeneous photocatalysts include 4-nitrocatechol and hydroquinone, while degradation of 4-Np in the presence of the heterogeneous photocatalysts resulted in fumaric acid and 4-nitrocatechol. ClAlPc was employed for the heterogeneous photocatalysis of the non-systemic insecticide, methyl paraoxon. Complete degradation of the pesticide was confirmed by the disappearance of the HPLC trace for methyl paraoxon after 100 min of irradiation with visible light. The removal of 4-Np from an aqueous medium using commercially available Amberlite[superscript ®] IRA-900 modified with metal phthalocyanines was also investigated. The metallophthalocyanines immobilised onto the surface of Amberlite[superscript ®] IRA-900 include Fe (FePcS[subscript 4]), Co (CoPcS[subscript 4]) and Ni (NiPcS[subscript 4]) tetrasulphophthalocyanines, and differently sulphonated phthalocyanine mixtures of Fe (FePcS[subscript mix]), Co (CoPcS[subscript mix]) and Ni (NiPcS[subscript mix]). Adsorption rates were fastest for the modified adsorbents at pH 9. Using the Langmuir-Hinshelwood kinetic model, the complexes showed the following order of 4-Np adsorption: CoPcS[subscript mix] > NiPcS[subscript 4] > NiPcS[subscript mix] > FePcS[subscript 4] > FePcS[subscript mix] > CoPcS[subscript 4]. The adsorbents were regenerated using dilute HNO[subscript 3], with 76 % (7.6 x 10[superscript -5] mol) of 4-Np recovered within 150 min.
- Full Text:
- Date Issued: 2008
- Authors: Marais, Eloise Ann
- Date: 2008
- Subjects: Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4343 , http://hdl.handle.net/10962/d1005005 , Photocatalysis , Catalysis , Electrochemistry , Nitrophenols , Phthalocyanines
- Description: Photodegradation of 4-nitrophenol (4-Np) in the presence of water-soluble zinc phthalocyanines and water-insoluble metallophthalocyanines is reported. The water-soluble phthalocyanines employed include zinc tetrasulphophthalocyanine (ZnPcS[subscript 4]), zinc octacarboxyphthalocyanine (ZnPc(COOH)[subscript 8]) and a sulphonated ZnPc containing a mixture of differently sulphonated derivatives (ZnPcS[subscript mix]), while the water-insoluble phthalocyanines used include unsubstituted magnesium (MgPc), zinc (ZnPc) and chloroaluminium (ClAlPc) phthalocyanine complexes and the ring-substituted zinc tetranitro (ZnPc(NO[subscript 2])[subscript 4]), zinc tetraamino (ZnPc(NH[subscript 2])[subscript 4]), zinc hexadecafluoro (ZnPcF[subscript 16]) and zinc hexadecachloro (ZnPcCl[subscript 16]) phthalocyanines. The most effective water-soluble photocatalyst is ZnPcS[subscript mix] in terms of the high quantum yield obtained for 4-Np degradation (Φ[subscript 4-Np]) as well as its photostability. While ZnPc(COOH)[subscript 8] has the highest Φ[subscript 4-Np] value relative to the other water-soluble complexes, it degrades readily during photocatalysis. The Φ[subscript 4-Np] values were closely related to the singlet oxygen quantum yields Φ[subscript Δ] and hence aggregation. The rate constants for the reaction with 4-Np were kr = 0.67 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPcS[subscript mix] and 7.7 x 10[superscript 6] mol[superscript -1] dm[superscript 3] s[superscript -1] for ZnPc(COOH)[subscript 8]. ClAlPc is the most effective photocatalyst relative to the other heterogeneous photocatalysts for the phototransformation of 4-Np, with 89 ± 8.4 % degradation of 4-Np achieved after 100 min. The least effective catalysts were ZnPcCl[subscript 16] and MgPc. The final products of the photocatalysis of 4-Np in the presence of the homogeneous photocatalysts include 4-nitrocatechol and hydroquinone, while degradation of 4-Np in the presence of the heterogeneous photocatalysts resulted in fumaric acid and 4-nitrocatechol. ClAlPc was employed for the heterogeneous photocatalysis of the non-systemic insecticide, methyl paraoxon. Complete degradation of the pesticide was confirmed by the disappearance of the HPLC trace for methyl paraoxon after 100 min of irradiation with visible light. The removal of 4-Np from an aqueous medium using commercially available Amberlite[superscript ®] IRA-900 modified with metal phthalocyanines was also investigated. The metallophthalocyanines immobilised onto the surface of Amberlite[superscript ®] IRA-900 include Fe (FePcS[subscript 4]), Co (CoPcS[subscript 4]) and Ni (NiPcS[subscript 4]) tetrasulphophthalocyanines, and differently sulphonated phthalocyanine mixtures of Fe (FePcS[subscript mix]), Co (CoPcS[subscript mix]) and Ni (NiPcS[subscript mix]). Adsorption rates were fastest for the modified adsorbents at pH 9. Using the Langmuir-Hinshelwood kinetic model, the complexes showed the following order of 4-Np adsorption: CoPcS[subscript mix] > NiPcS[subscript 4] > NiPcS[subscript mix] > FePcS[subscript 4] > FePcS[subscript mix] > CoPcS[subscript 4]. The adsorbents were regenerated using dilute HNO[subscript 3], with 76 % (7.6 x 10[superscript -5] mol) of 4-Np recovered within 150 min.
- Full Text:
- Date Issued: 2008
Reproductive performance of cows in sweet and sour veld types under communal production systems in the Eastern Cape Province of South Africa
- Authors: Nqeno, Noluvuyo
- Date: 2008
- Subjects: Pastoral systems -- Economic aspects -- South Africa -- Eastern Cape , Commons -- South Africa -- Eastern Cape , Beef cattle -- Breeding , Beef cattle -- Reproduction , Grazing -- South Africa -- Eastern Cape , Dairy cattle , Cows
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11815 , http://hdl.handle.net/10353/141 , Pastoral systems -- Economic aspects -- South Africa -- Eastern Cape , Commons -- South Africa -- Eastern Cape , Beef cattle -- Breeding , Beef cattle -- Reproduction , Grazing -- South Africa -- Eastern Cape , Dairy cattle , Cows
- Description: The objective of the study was to evaluate cow reproductive performance in the sweetveld and sourveld communal grazing areas of the Eastern Cape Province, South Africa. In the first experiment, farmer perceptions were obtained using participatory rural appraisals. Farmers ranked lack of fences, tick-borne diseases, poor animal condition during winter and poor breeding practices, respectively as major constraints limiting cattle production in the Eastern Cape. Cattle, sheep and goats, in that order, were ranked as the most important livestock species and were mainly kept for meat, cash and ceremonies, respectively. The non-descript cattle breed was the most common breed found in the smallholder areas. Most farmers preferred Nguni breed because of its adaptive attributes. In the second experiment, structured questionnaires were administered, between June and August 2006, to a total of 551 farmers from 10 communities of the Eastern Cape. There was a significant association (P<0.05) between the use of pregnancy diagnoses and community. About 87 and 77 % of the interviewed farmers did not respond on the extent of pregnancy and calving rates in their herds. A higher proportion of farmers from Hekele (51%) and from Upper Mnxe (45.3%) communities reported low number of bulls as a major constraint to cow reproductive performance. Body condition and ovarian activity were measured in the sweet and sour veld types. Body condition score of animals was measured from March iii 2007 until January 2008 and ovarian activity of cows was performed by a veterinarian through rectal palpation in June, August and October 2007 and January 2008. From March to July, there was a marked decline in body condition on both veld types. In the sweetveld, body condition improved from September until January, whereas in the sourveld the improvement in body condition started in October. The cows in both veld types conceived throughout the year. Most cows in the sweetveld were cycling in January and August (P<0.05) whereas in the sourveld there was no distinct period when the animals were cycling. Overall, there were no differences in the proportion of cows that were cycling between the sour and sweet veldts (P>0.05). There were more cows cycling in sourveld in October than in the sweetveld. Reproductive performance of cows in communal areas could, therefore, be determined by levels and quality of nutrition. Keywords: Participatory rural appraisals; Structured questionnaires; Farmer participation; Farmer perceptions; Body condition scoring; Ovarian activity; Pregnancy diagnoses.
- Full Text:
- Date Issued: 2008
- Authors: Nqeno, Noluvuyo
- Date: 2008
- Subjects: Pastoral systems -- Economic aspects -- South Africa -- Eastern Cape , Commons -- South Africa -- Eastern Cape , Beef cattle -- Breeding , Beef cattle -- Reproduction , Grazing -- South Africa -- Eastern Cape , Dairy cattle , Cows
- Language: English
- Type: Thesis , Masters , MSc Agric (Animal Science)
- Identifier: vital:11815 , http://hdl.handle.net/10353/141 , Pastoral systems -- Economic aspects -- South Africa -- Eastern Cape , Commons -- South Africa -- Eastern Cape , Beef cattle -- Breeding , Beef cattle -- Reproduction , Grazing -- South Africa -- Eastern Cape , Dairy cattle , Cows
- Description: The objective of the study was to evaluate cow reproductive performance in the sweetveld and sourveld communal grazing areas of the Eastern Cape Province, South Africa. In the first experiment, farmer perceptions were obtained using participatory rural appraisals. Farmers ranked lack of fences, tick-borne diseases, poor animal condition during winter and poor breeding practices, respectively as major constraints limiting cattle production in the Eastern Cape. Cattle, sheep and goats, in that order, were ranked as the most important livestock species and were mainly kept for meat, cash and ceremonies, respectively. The non-descript cattle breed was the most common breed found in the smallholder areas. Most farmers preferred Nguni breed because of its adaptive attributes. In the second experiment, structured questionnaires were administered, between June and August 2006, to a total of 551 farmers from 10 communities of the Eastern Cape. There was a significant association (P<0.05) between the use of pregnancy diagnoses and community. About 87 and 77 % of the interviewed farmers did not respond on the extent of pregnancy and calving rates in their herds. A higher proportion of farmers from Hekele (51%) and from Upper Mnxe (45.3%) communities reported low number of bulls as a major constraint to cow reproductive performance. Body condition and ovarian activity were measured in the sweet and sour veld types. Body condition score of animals was measured from March iii 2007 until January 2008 and ovarian activity of cows was performed by a veterinarian through rectal palpation in June, August and October 2007 and January 2008. From March to July, there was a marked decline in body condition on both veld types. In the sweetveld, body condition improved from September until January, whereas in the sourveld the improvement in body condition started in October. The cows in both veld types conceived throughout the year. Most cows in the sweetveld were cycling in January and August (P<0.05) whereas in the sourveld there was no distinct period when the animals were cycling. Overall, there were no differences in the proportion of cows that were cycling between the sour and sweet veldts (P>0.05). There were more cows cycling in sourveld in October than in the sweetveld. Reproductive performance of cows in communal areas could, therefore, be determined by levels and quality of nutrition. Keywords: Participatory rural appraisals; Structured questionnaires; Farmer participation; Farmer perceptions; Body condition scoring; Ovarian activity; Pregnancy diagnoses.
- Full Text:
- Date Issued: 2008
Resilience in families living with a child diagnosed with attention deficit/hyperactivity disorder
- Authors: Theron, Tania
- Date: 2008
- Subjects: Hyperactive children -- Psychological testing , Attention-deficit hyperactivity disorder -- Diagnosis , Attention-deficit-disordered children
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9927 , http://hdl.handle.net/10948/655 , Hyperactive children -- Psychological testing , Attention-deficit hyperactivity disorder -- Diagnosis , Attention-deficit-disordered children
- Description: Attention Deficit/Hyperactivity Disorder (AD/HD) is not a new phenomenon. Researchers have studied children with restless, inattentive and impulsive types of behaviours for over one hundred years. Although the primary distress of AD/HD falls mainly on the child’s shoulders, all family members experience the disorder’s negative effects. While the challenges that families have to face are many, families seem to have the ability to “bounce back” (i.e., they have resilience). There has been limited research to date focusing on the resiliency of families living with children diagnosed with AD/HD. Research on the construct of resilience, and more specifically, family resilience has surged in recent times. However, South African research on family resilience is limited. This study aimed to explore and describe the factors that facilitate adjustment and adaptation in families after a child has been clinically diagnosed with AD/HD. The Resiliency Model of Family Stress, Adjustment and Adaptation, developed by McCubbin and McCubbin (2001) served as a framework to conceptualize the families’ adjustment and adaptation processes. Non-probability purposive sampling was used in order to gain participants for the study. Twenty-two families participated in this study, providing a total of 44 participants. Participants consisted of the caregivers of a family living with a child diagnosed with AD/HD, between the ages of seven and 12. The study was triangular in nature, with an exploratory, descriptive approach. A biographical questionnaire with an open-ended question was used in conjunction with seven other questionnaires to gather data. Descriptive statistics were used to describe the biographical information. Quantitative data were analyzed by means of correlation and regression analysis, and content analysis was used to analyze the qualitative data obtained from the biographical questionnaire. The results of the quantitative analysis indicated six significant positive correlations with the FACI8. These variables were relative and friend support, social support, problem solving and behavioural strategies, family hardiness, family problem-solving communication and family time and routines. The results of the qualitative analysis revealed that social support, adherence to a treatment regime, information and knowledge about AD/HD, a supportive family unit, the caregiver’s acceptance of the disorder as well as communication were the most important strength factors identified. The findings of the research could assist parents in managing their children diagnosed with AD/HD more effectively and has helped create further insight into what resiliency areas they could improve upon. Furthermore, this study could be used as a stepping stone for future research on resilience in families living with a pervasive psychological disorder and will contribute to the broader context of family resilience research in the South African context.
- Full Text:
- Date Issued: 2008
- Authors: Theron, Tania
- Date: 2008
- Subjects: Hyperactive children -- Psychological testing , Attention-deficit hyperactivity disorder -- Diagnosis , Attention-deficit-disordered children
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9927 , http://hdl.handle.net/10948/655 , Hyperactive children -- Psychological testing , Attention-deficit hyperactivity disorder -- Diagnosis , Attention-deficit-disordered children
- Description: Attention Deficit/Hyperactivity Disorder (AD/HD) is not a new phenomenon. Researchers have studied children with restless, inattentive and impulsive types of behaviours for over one hundred years. Although the primary distress of AD/HD falls mainly on the child’s shoulders, all family members experience the disorder’s negative effects. While the challenges that families have to face are many, families seem to have the ability to “bounce back” (i.e., they have resilience). There has been limited research to date focusing on the resiliency of families living with children diagnosed with AD/HD. Research on the construct of resilience, and more specifically, family resilience has surged in recent times. However, South African research on family resilience is limited. This study aimed to explore and describe the factors that facilitate adjustment and adaptation in families after a child has been clinically diagnosed with AD/HD. The Resiliency Model of Family Stress, Adjustment and Adaptation, developed by McCubbin and McCubbin (2001) served as a framework to conceptualize the families’ adjustment and adaptation processes. Non-probability purposive sampling was used in order to gain participants for the study. Twenty-two families participated in this study, providing a total of 44 participants. Participants consisted of the caregivers of a family living with a child diagnosed with AD/HD, between the ages of seven and 12. The study was triangular in nature, with an exploratory, descriptive approach. A biographical questionnaire with an open-ended question was used in conjunction with seven other questionnaires to gather data. Descriptive statistics were used to describe the biographical information. Quantitative data were analyzed by means of correlation and regression analysis, and content analysis was used to analyze the qualitative data obtained from the biographical questionnaire. The results of the quantitative analysis indicated six significant positive correlations with the FACI8. These variables were relative and friend support, social support, problem solving and behavioural strategies, family hardiness, family problem-solving communication and family time and routines. The results of the qualitative analysis revealed that social support, adherence to a treatment regime, information and knowledge about AD/HD, a supportive family unit, the caregiver’s acceptance of the disorder as well as communication were the most important strength factors identified. The findings of the research could assist parents in managing their children diagnosed with AD/HD more effectively and has helped create further insight into what resiliency areas they could improve upon. Furthermore, this study could be used as a stepping stone for future research on resilience in families living with a pervasive psychological disorder and will contribute to the broader context of family resilience research in the South African context.
- Full Text:
- Date Issued: 2008
Resilience in families with a child living with Autism Spectrum Disorder
- Authors: Hanekom, Leché
- Date: 2008
- Subjects: Autism in children , Parents of autistic children , Autistic children -- Family relationships
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9905 , http://hdl.handle.net/10948/973 , Autism in children , Parents of autistic children , Autistic children -- Family relationships
- Description: In recent years the number of studies on resilience emerging within the field of positive psychology has increased. However, such studies are limited within the South African context and so the proposed study aims to explore and describe the factors that facilitate adjustment and adaptation in South African families living with Autism Spectrum Disorder. McCubbin, McCubbin and Thompson (2001) developed the Resiliency Model of Family Stress, Adjustment and Adaptation which were used to conceptualise the family’s adaptation. Mothers (n = 19) from 19 families participated in the study. The families consisted of at least three members, of which two are parents and one a child younger than 18 years of age that has been diagnosed with Autistic Spectrum Disorder. A combination of non-probability purposive sampling and snowball sampling was used to select participants. The study had an exploratory and descriptive aim and employed triangulation of method, including both qualitative and quantitative data collection procedures. A biographical questionnaire and the following seven structured paper-and-pencil questionnaires were used: the Family Attachment and Changeability Index 8 (FACI8), the Family Crisis-oriented Personal Evaluation Scales (F-COPES), the Family Hardiness Index (FHI), the Family Problem-solving Communication (FPSC), the Family Time and Routine Index (FTRI), the Relative and Friend Support (RFS), and the Social Support Index (SSI). Descriptive statistics were used to describe the biographical information. Qualitative data were analysed by means of content analysis. Quantitative data were manipulated by means of correlation and regression analysis. The results from the quantitative analysis indicate three significant positive correlations with the FACI8. These variables were the family hardiness (measured by FHI), family problem-solving communication (measured by the FPSC), and family time and routines (measured by the FTRI). The findings from the qualitative analysis point out that social support, the spousal relationship and family time, togetherness and routines are the most important strength factors that contribute to the family’s adjustment and adaptation. Even though this study had a small sample size and several other limitations, the findings of this study could still assist in guiding specialised institutions toward providing more comprehensive information and support to families living with a child diagnosed with Autism Spectrum Disorder. This study also contributes to the studies on family resilience within a South African context.
- Full Text:
- Date Issued: 2008
- Authors: Hanekom, Leché
- Date: 2008
- Subjects: Autism in children , Parents of autistic children , Autistic children -- Family relationships
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9905 , http://hdl.handle.net/10948/973 , Autism in children , Parents of autistic children , Autistic children -- Family relationships
- Description: In recent years the number of studies on resilience emerging within the field of positive psychology has increased. However, such studies are limited within the South African context and so the proposed study aims to explore and describe the factors that facilitate adjustment and adaptation in South African families living with Autism Spectrum Disorder. McCubbin, McCubbin and Thompson (2001) developed the Resiliency Model of Family Stress, Adjustment and Adaptation which were used to conceptualise the family’s adaptation. Mothers (n = 19) from 19 families participated in the study. The families consisted of at least three members, of which two are parents and one a child younger than 18 years of age that has been diagnosed with Autistic Spectrum Disorder. A combination of non-probability purposive sampling and snowball sampling was used to select participants. The study had an exploratory and descriptive aim and employed triangulation of method, including both qualitative and quantitative data collection procedures. A biographical questionnaire and the following seven structured paper-and-pencil questionnaires were used: the Family Attachment and Changeability Index 8 (FACI8), the Family Crisis-oriented Personal Evaluation Scales (F-COPES), the Family Hardiness Index (FHI), the Family Problem-solving Communication (FPSC), the Family Time and Routine Index (FTRI), the Relative and Friend Support (RFS), and the Social Support Index (SSI). Descriptive statistics were used to describe the biographical information. Qualitative data were analysed by means of content analysis. Quantitative data were manipulated by means of correlation and regression analysis. The results from the quantitative analysis indicate three significant positive correlations with the FACI8. These variables were the family hardiness (measured by FHI), family problem-solving communication (measured by the FPSC), and family time and routines (measured by the FTRI). The findings from the qualitative analysis point out that social support, the spousal relationship and family time, togetherness and routines are the most important strength factors that contribute to the family’s adjustment and adaptation. Even though this study had a small sample size and several other limitations, the findings of this study could still assist in guiding specialised institutions toward providing more comprehensive information and support to families living with a child diagnosed with Autism Spectrum Disorder. This study also contributes to the studies on family resilience within a South African context.
- Full Text:
- Date Issued: 2008
Resilience in HIV/AIDS' adolescent headed families
- Authors: Beeka, Hershilla A
- Date: 2008
- Subjects: Resilience (Personality trait) in adolescence -- South Africa -- Port Elizabeth , Children of AIDS patients -- South Africa -- Family relationships , Families, Black -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9911 , http://hdl.handle.net/10948/922 , Resilience (Personality trait) in adolescence -- South Africa -- Port Elizabeth , Children of AIDS patients -- South Africa -- Family relationships , Families, Black -- Research -- South Africa
- Description: HIV/AIDS has presented humanity with various challenges, one of which is the manner in which it has affected family structure and patterns. Parental illness and eventual death due to the HIV/AIDS pandemic is escalating. One of the major challenges of HIV/AIDS in southern Africa is the increase in the number of orphaned and vulnerable children. As a result new family forms are emerging such as the "skip-generation" family in which children or adolescent siblings head the family. It is anticipated that HIV/AIDS in South Africa will progressively increase the number of such families. During this time of profound family change, the family as an institution has remained remarkably resilient. The present study utilised the Family Resilience Framework and the Resiliency Model of Family Stress, Adjustment and Adaptation to explore and describe the resilience of HIV/AIDS’ adolescent headed families. A qualitative, exploratory-descriptive research design, which was assessed against Guba’s (1985) model of trustworthiness, was employed and the participants were sampled using non-probability purposive sampling. The Masizakhe Community Project volunteers (an AIDS Community Project in Kwazakhele, Port Elizabeth receiving support from the iThemba AIDS Foundation) assisted in identifying participants according to the predetermined inclusion criteria. The sample consisted of four female, adolescent heads of HIV/AIDS’ affected households, who volunteered at the Masizakhe Community Project and resided in Kwazakhele. The data that was collected via audio-recorded semi structured interviews were transcribed verbatim and subjected to Interpretive Phenomenological Analysis. Family resilience factors that emerged included intrafamilial strengths (family cohesion, organisation, hardiness, and adaptability); social support resources (especially from the community project, friends, and community members); family appraisal processes; and problem solving and coping strategies. Extended family support was partial and largely financial. The findings from this study provided insights into the resilience of adolescent-headed families; provided guidance for the development of intervention programmes to assist these families; and affirmed the existing strengths of the families. Furthermore, it has contributed to the research and literature on family resilience and formed the foundation for future research projects.
- Full Text:
- Date Issued: 2008
- Authors: Beeka, Hershilla A
- Date: 2008
- Subjects: Resilience (Personality trait) in adolescence -- South Africa -- Port Elizabeth , Children of AIDS patients -- South Africa -- Family relationships , Families, Black -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9911 , http://hdl.handle.net/10948/922 , Resilience (Personality trait) in adolescence -- South Africa -- Port Elizabeth , Children of AIDS patients -- South Africa -- Family relationships , Families, Black -- Research -- South Africa
- Description: HIV/AIDS has presented humanity with various challenges, one of which is the manner in which it has affected family structure and patterns. Parental illness and eventual death due to the HIV/AIDS pandemic is escalating. One of the major challenges of HIV/AIDS in southern Africa is the increase in the number of orphaned and vulnerable children. As a result new family forms are emerging such as the "skip-generation" family in which children or adolescent siblings head the family. It is anticipated that HIV/AIDS in South Africa will progressively increase the number of such families. During this time of profound family change, the family as an institution has remained remarkably resilient. The present study utilised the Family Resilience Framework and the Resiliency Model of Family Stress, Adjustment and Adaptation to explore and describe the resilience of HIV/AIDS’ adolescent headed families. A qualitative, exploratory-descriptive research design, which was assessed against Guba’s (1985) model of trustworthiness, was employed and the participants were sampled using non-probability purposive sampling. The Masizakhe Community Project volunteers (an AIDS Community Project in Kwazakhele, Port Elizabeth receiving support from the iThemba AIDS Foundation) assisted in identifying participants according to the predetermined inclusion criteria. The sample consisted of four female, adolescent heads of HIV/AIDS’ affected households, who volunteered at the Masizakhe Community Project and resided in Kwazakhele. The data that was collected via audio-recorded semi structured interviews were transcribed verbatim and subjected to Interpretive Phenomenological Analysis. Family resilience factors that emerged included intrafamilial strengths (family cohesion, organisation, hardiness, and adaptability); social support resources (especially from the community project, friends, and community members); family appraisal processes; and problem solving and coping strategies. Extended family support was partial and largely financial. The findings from this study provided insights into the resilience of adolescent-headed families; provided guidance for the development of intervention programmes to assist these families; and affirmed the existing strengths of the families. Furthermore, it has contributed to the research and literature on family resilience and formed the foundation for future research projects.
- Full Text:
- Date Issued: 2008
Resilience in remarried families
- Authors: Robinson, Julie
- Date: 2008
- Subjects: Remarried people -- Family relationships , Adjustment (Psychology) , Stepfamilies -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9924 , http://hdl.handle.net/10948/659 , Remarried people -- Family relationships , Adjustment (Psychology) , Stepfamilies -- Psychological aspects
- Description: Remarried families are no longer the exception in society. Statistics reveal that this type of family structure is increasing. The need for family resilience research in varying family forms has been highlighted. Given the distinctive structure of the remarried family, there are specific dilemmas and challenges that need to be resolved on the journey towards family integration. Despite these challenges, many families benefit from their new family structure and show marked resiliency and ability to adapt. South African family resilience research is scarce. This study aimed to identify, explore and describe the resiliency factors that enable families to adjust and adapt as a result of being a stepfamily. The Resiliency Model of Family Stress, Adjustment and Adaptation (McCubbin, Thompson, & McCubbin, 2001) was used to conceptualize level of adaptation. Participants consisted of both adults and adolescents, in order to gain perspectives of adapting to a remarried family from differing individual family members’ stages of development. Participants consisted of 19 parents and 16 adolescents, equaling a total of 35 participants. Triangulation was employed, with an exploratory, descriptive approach. A biographical questionnaire with an open-ended question, in conjunction with a number of structured questionnaires were used to gather the data. These questionnaires were: The Family Hardiness Index (FHI), the Family Time and Routine Index (FTRI), the Social Support Index (SSI), the Family Problem-Solving Communication (FPSC) Index, the Family Crisis-Oriented Personal Evaluation Scales (F-COPES), the Relative and Friend Support Index (RFS), and the Family Attachment and Changeability Index 8 (FACI8). In this study the FACI8 was used as a measure to determine the level of family adaptation. Non-probability purposive and snowball sampling techniques were used. Descriptive statistics were used to analyze the biographical information. Correlation and regression analysis was used to analyze the quantitative data, and content analysis was used to analyze the qualitative data. The results of the quantitative component of the study indicated that there were three significant positive correlations with the FACI8 for both adults and adolescents. These variables were family hardiness (measured by the FHI), family problem solving communication (measured by the FPSC), and family time together and routines (measured by the FTRI). The Social Support subscale of the F-COPES showed a positive correlation with the FACI8 for the adults. The results of the qualitative component of the study revealed that various common themes emerged between the adult and adolescent participants’ responses. These common themes were spirituality; boundaries; respect, love, understanding, compassion and acceptance; communication; flexibility and tolerance; time together, bonding, and routines; and social support. There were four remaining themes that the adults identified as important factors helping them manage being part of a stepfamily. These four remaining themes were equality; forgiveness and acceptance of the past; commitment and being positive; and financial support. The value of the research was discussed. Finally, limitations of the study were discussed, and suggestions were made for future research involving remarried families.
- Full Text:
- Date Issued: 2008
- Authors: Robinson, Julie
- Date: 2008
- Subjects: Remarried people -- Family relationships , Adjustment (Psychology) , Stepfamilies -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9924 , http://hdl.handle.net/10948/659 , Remarried people -- Family relationships , Adjustment (Psychology) , Stepfamilies -- Psychological aspects
- Description: Remarried families are no longer the exception in society. Statistics reveal that this type of family structure is increasing. The need for family resilience research in varying family forms has been highlighted. Given the distinctive structure of the remarried family, there are specific dilemmas and challenges that need to be resolved on the journey towards family integration. Despite these challenges, many families benefit from their new family structure and show marked resiliency and ability to adapt. South African family resilience research is scarce. This study aimed to identify, explore and describe the resiliency factors that enable families to adjust and adapt as a result of being a stepfamily. The Resiliency Model of Family Stress, Adjustment and Adaptation (McCubbin, Thompson, & McCubbin, 2001) was used to conceptualize level of adaptation. Participants consisted of both adults and adolescents, in order to gain perspectives of adapting to a remarried family from differing individual family members’ stages of development. Participants consisted of 19 parents and 16 adolescents, equaling a total of 35 participants. Triangulation was employed, with an exploratory, descriptive approach. A biographical questionnaire with an open-ended question, in conjunction with a number of structured questionnaires were used to gather the data. These questionnaires were: The Family Hardiness Index (FHI), the Family Time and Routine Index (FTRI), the Social Support Index (SSI), the Family Problem-Solving Communication (FPSC) Index, the Family Crisis-Oriented Personal Evaluation Scales (F-COPES), the Relative and Friend Support Index (RFS), and the Family Attachment and Changeability Index 8 (FACI8). In this study the FACI8 was used as a measure to determine the level of family adaptation. Non-probability purposive and snowball sampling techniques were used. Descriptive statistics were used to analyze the biographical information. Correlation and regression analysis was used to analyze the quantitative data, and content analysis was used to analyze the qualitative data. The results of the quantitative component of the study indicated that there were three significant positive correlations with the FACI8 for both adults and adolescents. These variables were family hardiness (measured by the FHI), family problem solving communication (measured by the FPSC), and family time together and routines (measured by the FTRI). The Social Support subscale of the F-COPES showed a positive correlation with the FACI8 for the adults. The results of the qualitative component of the study revealed that various common themes emerged between the adult and adolescent participants’ responses. These common themes were spirituality; boundaries; respect, love, understanding, compassion and acceptance; communication; flexibility and tolerance; time together, bonding, and routines; and social support. There were four remaining themes that the adults identified as important factors helping them manage being part of a stepfamily. These four remaining themes were equality; forgiveness and acceptance of the past; commitment and being positive; and financial support. The value of the research was discussed. Finally, limitations of the study were discussed, and suggestions were made for future research involving remarried families.
- Full Text:
- Date Issued: 2008