1834 research outputs found
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Distribution and establishment of the alien Australian redclaw crayfish, Cherax quadricarinatus, in South Africa and Swaziland
No full textThe Australian redclaw crayfish (Cherax quadricarinatus, von Martens),
is native to Australasia, but has been widely translocated around the world due to
aquaculture and aquarium trade. Mostly as a result of escape from aquaculture facilities,
this species has established extralimital populations in Australia and alien populations
in Europe, Asia, Central America and Africa. In South Africa, C. quadricarinatus was
first sampled from the wild in 2002 in the Komati River, following its escape from an
aquaculture facility in Swaziland, but data on the current status of its populations are
not available
The effect of terpenoids on the expression and function of cytokines and adipokines in pre-adipocytes and differentiated adipocytes
No full textType 2 diabetes is a metabolic disorder characterised by inflammation, insulin resistance and the inability of pancreatic β-cells to secrete enough insulin to produce a physiological effect. Obesity and high levels of triacylglycerol’s are associated with the development of Type 2 diabetes. Adipose tissue is an active endocrine organ that secretes various protein and peptide hormones, known as adipokines, which mediate important metabolic functions. In an insulin resistant and hyperglycaemic state, levels of anti-inflammatory adipokines, adiponectin, are reduced, whereas levels of pro-inflammatory cytokines, interleukin-6 and interleukin-1β, are elevated; this results in a shift from an anti- to a pro-inflammatory state that is accompanied by dysfunction and apoptosis of the pancreatic β-cells. Cannabis sativa L. has been traditionally used as an anti-inflammatory agent in Southern Africa, specifically treating snakebites, fever and malaria. Δ9-tetrahydrocannabinol is the main psychoactive compound derived from C. sativa, whereas the other major cannabinoids, cannabinol and cannabidiol, have shown anti-inflammatory and sedative properties respectively. Marrubiin is a compound derived from the plant Leonotis leonurus L. and has been traditionally used as an anti-inflammatory and anti-diabetic agent. To determine the effects of these compounds in a hyperglycaemic state, pre- and differentiated mouse adipocytes (3T3-L1 cells) were exposed for seven and fourteen days to the following treatments: Δ9-tetrahydrocannabinol, cannabidiol, cannabinol, marrubiin, anandamide (an endogenous endocannabinoid) and cannabis extract, individually and in combination, under normal glucose and hyperglycaemic conditions. Levels of adiponectin, interleukin-6, leptin, tumour-necrosis factor-α and interleukin-1β were quantified using mouse enzyme-linked immunosorbent assay kits and Oil Red O staining was carried out to determine lipid distribution and lipid droplet characteristics. Results indicate that various cannabinoids, in combination, mediate an anti-inflammatory effect by decreasing the expression of various pro-inflammatory cytokines, which may have allowed for a shift from a pro- to an anti-inflammatory state by these compounds, and may also contribute to the reduction of lipid, which may be used as a supplementary option to current diabetic treatment regimes.National Research Foundatio
NRF Key Performance Indicators
No full textThe Grants Management and Systems Administration (GMSA) Directorate hosted its 8th annual Research Administrators Workshop (RAW) from 9 to 11 October 2017 in the Western Cape. The workshop aimed to bring together key stakeholders from universities and science councils across South Africa, including international delegates, to share experiences and best practices in research administration and management
The association between sedentary behaviour, physical activity and coronary artery disease risk factors in employees at tertiary institute in South Africa
No full textBackground Sedentary behaviour has incrementally increased over the past few years. The scientific community recognises this behaviour as a twenty first century disease which reflects the detrimental effects of excessive sitting on several adverse functional and clinical health outcomes, such as chronic disease, in the general adult population. Many evolving contemporary occupations require that employees sit an average of eight hours per day at work stations or office desks, especially when using communication technology. Even after accounting for the self-reported time spent in recommended physical activity, the negative dose-response relationship between time spent in sedentary behaviour and the all-cause and cardiovascular disease mortality still remain. Aim: To establish a profile of sedentary behaviour as well as levels of physical activity and coronary artery disease risk factors in employees at a tertiary institute in the Eastern Cape Province of South Africa. Another aim is to determine whether an association exists between the aforementioned variables.National Research Foundation (South Africa
The retirement funding adequacy of black South Africans
No full textDespite the importance of retirement planning, many South Africans have been documented as reaching retirement age without adequate retirement funding. A vast amount of research has been conducted on how proper retirement planning can be beneficial for individuals; however, there has been a lack of attention given to researching the retirement planning of black individuals in South Africa. Thus, the primary objective of this study was to identify, investigate and empirically test which factors influence retirement planning, and which aspects of retirement planning influence the retirement funding adequacy of black individuals. After a comprehensive literature review was undertaken on the factors influencing the retirement planning and retirement funding adequacy of individuals, the following independent variables were identified as influencing the mediating variable (Aspects of retirement planning) and the dependent variable (Retirement funding adequacy) in this study: • Financial literacy; • The role of the financial planner; • Family support structure; and • Health status. These independent variables were selected to construct a hypothesised model and research hypotheses, as they have been identified as the prominent factors that influence the retirement planning of black South Africans. Furthermore, these independent variables were used in determining whether they have an influence on the Aspects of retirement planning (incorporating Retirement provisions, Retirement attitudes and Retirement intentions) and, ultimately, improve the Retirement funding adequacy of individuals. In order to establish the influence of the aspects of retirement planning on the retirement funding adequacy of individuals, an empirical investigation was undertaken. A measuring instrument, in the form of a questionnaire, was compiled from secondary literature sources. The respondents were identified though a mixed sampling approach, whereby stratified sampling and convenience sampling were used to attain 441 usable questionnaires that were subjected to statistical analyses. Descriptive statistics, in the form of frequency distributions, were used to summarise Section A and Section B of the measuring instrument. The validity and reliability of the measuring instrument were confirmed by means of exploratory factor analyses (EFA), and Cronbach’s alpha coefficients were also calculated for this purpose. As a result of conducting the EFA, two independent variables (Family support structure and Health status) loaded together, and the factor was renamed accordingly. From the EFA, the independent variables that emerged were The role of the financial planner, Family, health, and financial well-being, and Financial literacy. Furthermore, the EFA revealed that three mediating variables emerged from the mediating variable Aspects of retirement planning. These three mediating variables were consequently named Retirement intentions, Retirement attitudes, and Retirement provisions. There were no eliminated variables in this study. Based on the results of the EFA, some of the definitions of the variables were adapted. Consequently, the hypothesised model and its research hypotheses were adapted to reflect the results of the EFA. The results of the Cronbach’s alphas calculated reported that all the measuring scales used in the questionnaire of the study were reliable. Furthermore, descriptive statistics were also calculated to summarise the sample data, and Pearson’s product moment correlations were calculated to establish the correlations between all the variables used in this study. A multiple regression analysis was used to investigate the influence of the various independent variables on the mediating variables and the dependent variable. Furthermore, structural equation modelling (SEM) was used as the main statistical procedure to test for mediation in the study. SEM was also used to assess and confirm the results of the multiple regression analyses. Based on the results of the multiple regression analyses and SEM, the hypothesised relationships of the study were accepted or rejected. Additionally, the results of SEM revealed that the revised model of the study displayed acceptable model fit. To conclude the empirical investigation, t-tests and an analysis of variance (ANOVA) tests were performed to assess whether the respondents’ perceptions of the variables used in the study differed as a result of the respondents’ demographic information. Furthermore, to establish significant differences between individual mean scores, post-hoc Tukey tests were calculated, and practical significance was assessed by calculating Cohen’s d values. The main empirical results of the study found that statistically significant relationships exist between the independent variables The role of the financial planner and Family, health, and financial well-being, and the mediating variable Retirement intentions. Furthermore, a significant relationship was found between the independent variable Financial literacy and the mediating variable Retirement attitudes. Other significant relationships were present between all the independent variables The role of the financial planner, Family, health, and financial well-being and Financial literacy, and the mediating variable Retirement provisions. The study also established statistically significant relationships between the mediating variables Retirement attitudes and Retirement provisions and the dependent variable Retirement funding adequacy. Statistically significant relationships were also present between the independent variables Family, health, and financial well-being and Financial literacy and the dependent variable Retirement funding adequacy. This study has added to the limited amount of academic literature in the field of retirement planning in South Africa. Through the hypothesised model developed in this study, a significant contribution has been made towards investigating the factors that influence the retirement planning and retirement funding adequacy of black individuals residing in South Africa. This study presents recommendations to black individuals on practical strategies that could help to improve their retirement planning and retirement funding adequacy. Furthermore, suggestions are presented to financial planners and financial institutions, in order to assist black individuals or potential clients to improve their retirement planning and to help ensure that individuals are financially independent when they reach retirement age. It is recommended that financial institutions provide financial products/services that will cater to black South Africans.National Research Foundation (South Africa
Determination of bioavailability and bioactivity of enzymatically hydrolysed fish protein and phosphates in the African catfish Clarias gariepinus
No full textNational Research Foundatio
Investigating polyol and acetic acid metabolism in wine related non-Saccharomyces yeasts
No full textGlycerol is the main polyol produced in Saccharomyces cerevisiae not only to counterbalance osmotic pressure but also to adjust redox balance. Incidentally, it may also contribute to the smooth mouthfeel of wine. Whereas glycerol is closely linked to acetic acid production in S. cerevisiae, this correlation is not as clear in non-Saccharomyces yeasts (particularly Torulaspora delbrueckii).
Additional polyols - which function as stress protectants and could potentially influence wine mouthfeel - have been reported in wine but the producing yeasts were never isolated. Lachancea thermotolerans, Starmerella bacillaris and T. debrueckii have been recently described as producing other polyols in addition to glycerol with the latter producing the highest amounts. However, the enzyme assays used were limited to polyol detection in combination.
Thus, the aim of this study was to optimize chromatography-based methods for the separation of polyols and to investigate the production of these compounds in non-Saccharomyces yeasts under a variety of environmental conditions.
Gas Chromatography-Mass Spectrophotometry was successful for the separation of polyols but only in fermentation samples with no residual sugars. Since non-Saccharomyces yeasts do not ferment to completion, other methods are required for the individual detection of polyols in order to follow production throughout fermentation.
Our data show that in addition to glycerol, three T. delbrueckii strains increasingly produced similar amounts of D-sorbitol, D-arabitol and D-mannitol throughout fermentation. Furthermore with the exception of glycerol, T. delbrueckii produced higher amounts of polyols in grape must when compared to synthetic must. Whereas glycerol is limited to NADH recycling, these additional polyols may increase the co-factor recycling pool in T. delbrueckii.
Our data also show that D-sorbitol, D-mannitol and D-arabitol production was influenced by initial sugar concentration with the highest amounts detected for D-arabitol in T. delbrueckii. In contrast to D-arabitol which was produced at the highest amounts, D-mannitol and D-sorbitol were not induced by NaCl. It is possible that these compounds may have accumulated within the cell as a consequence of the osmotic gradients or mechanisms related to the prevention of ion toxicity as observed in literature.
Polyol production was repressed in acetic acid media in this study and induced in ethanol supplemented media. The intake of acetic acid could have resulted in a change in redox balance and a reduced need for polyols as reported in literature. The presence of ethanol could have resulted in readjustment of polyol retention within the cell and release of polyols.
Overall this study shows that non-Saccharomyces yeasts (particularly T. delbrueckii) are capable of polyol production. The amounts of polyols produced in some non-Saccharomyces yeasts may have a direct impact on wine but further investigations are required on this.National Research Foundatio
Extreme value-based novelty detection
No full textThis dissertation investigates extreme value-based novelty detection. An in-depth review of the theoretical proofs and an analytical investigation of current novelty detection methods are given.
It is concluded that the use of extreme value theory for novelty detection leads to superior results.
The first part of this dissertation provides an overview of novelty detection and the various methods available to construct a novelty detection algorithm. Four broad approaches are discussed, with this dissertation focusing on probabilistic novelty detection. A summary of the
applications of novelty detection and the properties of an efficient novelty detection algorithm are also provided.
The theory of extremes plays a vital role in this work. Therefore, a comprehensive description of the main theorems and modelling approaches of extreme value theory is given. These results are used to construct various novelty detection algorithms based on extreme value theory.
The first extreme value-based novelty detection algorithm is termed the Winner-Takes-All method. The model’s strong theoretical underpinning as well as its disadvantages are discussed.
The second method reformulates extreme value theory in terms of extreme probability density.
This definition is utilised to derive a closed-form expression of the probability distribution of a
Gaussian probability density. It is shown that this distribution is in the minimum domain of attraction of the extremal Weibull distribution.
Two other methods to perform novelty detection with extreme value theory are explored, namely the numerical approach and the approach based on modern extreme value theory. Both these methods approximate the distribution of the extreme probability density values under the assumption of a Gaussian mixture model. In turn, novelty detection can be performed in complex settings using extreme value theory. To demonstrate an application of the discussed methods a banknote authentication dataset is analysed. It is clearly shown that extreme value-based novelty detection methods are extremely efficient in detecting forged banknotes. This demonstrates the practicality of the different approaches.
The concluding chapter compares the theoretical justification, predictive power and efficiency of the different approaches. Proposals for future research are also discussed.National Research Foundatio
The investigation of chemical variation in the stems and rhizomes of cissampelos capensis l. F. (menispermaceae) the eastern cape medicinal plant.
No full textCissampelos capensis L. f. (Menispermaceae) commonly known as “Mayisake” (Xhosa) and “Dawidjieswortel” (Afrikaans) is the most commonly used medicinal plant of the Menispermaceae family in South Africa. The rhizomes of Cissampelos capensis are the most used part of the plant to treat illnesses. This poses a threat to the ongoing conservation of this valuable endemic species. Thus, we studied the chemical variation and subsequently the bioactivity in the stems and rhizomes of Cissampelos capensis, the Eastern Cape medicinal plant, to suggest the possible use of the stems for medicinal purposes. We studied the variation in the chemical composition in the stems and the rhizomes by employing four different extraction methods; the methanolic-, non-polar-, alkaloidal- and Total Tertiary Alkaloidal (TTA) to extract compounds from Cissampelos capensis. Employing various chromatographic techniques, HPLC, NMR and LC/MS to investigate the chemical variation and the in vitro assays for the crude materials of the stems and rhizomes of Cissampelos capensis. We successfully documented a library of the phytochemicals content in Cissampelos capensis from three different regions in the Eastern Cape. We could profile different extraction methods, with the TTA extraction delivering the best comparative profile. Employing LC/MS and HPLC we identified eleven known alkaloidal compounds in the stems and rhizomes. We also isolated a known alkaloid, pronuciferine, from the TTA extract and a crystal structure of proto-quericitol from the methanolic extract, which was isolated for the first time from Cissampelos capensis. Preliminary in vitro results suggested anti-inflammatory activity in the methanolic extracts of the stems and rhizomes, while the TTA extracts showed some cytotoxicity. Finally, through analytical HPLC analysis this study found as high as 31% similarity between the chemical variation of the stems and rhizomes, but key alkaloids were not always present, indicating more work is needed before the stems can be recommended as a replacement for the rhizomes.National Research Foundation (South Africa
Design, development and testing of an adjustable above-knee prosthetic leg for toddlers.
No full textNational Research Foundatio