1834 research outputs found
Sort by
Development of bio-based composite products from agricultural wastes/crops residues for applications in automotive sector, green packaging and green buildings in South Africa
No full textDesign an energy efficient heat transfer system by optimising the nanofluids thermal-fluid properties by Constructal theory and modified NSGA-II multi-objective optimisation
No full textThe production of nanocrystalline cellulose from wood using ionic liquids for use as a green filler for polymer composites
No full textDSpace - CRIS: one stop solution for the research ecosysytem
No full textDSpace - CRIS workshop, 4 - 5 December 2016, iThembaLabs NRF, Cape Town
Mathematical epidemiological models with finite time extinction: the case of African swine fever virus in wildlife areas
No full textIn Mathematical Epidemiology disease free states are commonly represented as equilibria of dynamical systems which model the respective epidemiological processes. However, in cases when the equilibrium is zero and is related to extinction (of the population), due to the uniqueness property of a complete dynamical system, solutions may converge to an equilibrium but never reach it. This may give rise to qualitatively unrealistic behaviour such as a population that is practically extinct but is able to grow. An example of a case when this problem may arise is when modelling the dynamics of African Swine Fever (ASF), a contagious disease a ecting both domestic and wild pigs, in the Mkuze Game Reserve. In the paper by Arnot et. al.[3] it was established that although an increase in burrow infestation rates was observed, the disease was not detected within the game reserve. This situation cannot be captured using a model with exponential decay. In the following research project, we study various ODE and PDE models with the property that solutions approaching the disease free equilibrium 0, will reach it within nite time and remain at 0 thereafter. These include basic population models and epidemiological models with age and state structure. We then construct a model for ASF in order to accurately illustrate the phenomenon observed at the game reserve.National Research Foundatio
Bioprospecting for bioactive polysaccharides from marine algae endemic to South Africa
No full textFucoidan is a marine-derived sulphated polysaccharide with bioactive properties ideal for the food, chemical and pharmaceutical industries. The polysaccharide consists largely of L-fucose, has a highly heterogeneous structure and is of diverse origin. Fucoidan was extracted from Ecklonia maxima, Laminaria pallida and Splachnidium rugosum and the effect of different extraction methods on fucoidan heterogeneity was assessed. Extraction methods employed hot water, hydrochloric acid or calcium chloride salt. Fucoidan yield and purity were determined by various colorimetric assays. Highest fucoidan yield was obtained with the hot water extraction method as seen by highest L-fucose content. Splachnidium rugosum extracts contained ~5 times more L-fucose than Ecklonia maxima and Laminaria pallida extracts. The salt extraction method yielded extracts free of contaminants, however L-fucose content in all extracts was >20 times lower. Acid extraction yielded highest levels of uronic acid contamination and liberated sulphate from the fucoidan polysaccharide. The fucose-to-sulphate ratio for Ecklonia maxima was approximately 1:5, whilst the ratios for Splachnidium rugosum and Laminaria pallida were approximately 1:1 and 1:2, respectively. The acid and salt extraction methods removed all traces of protein contaminants, while the hot water method retained very low levels of protein. The extraction method used to isolate fucoidan was a determining factor in yield and purity. Chemical compositional analyses of hot water extracts were assessed by gas chromatography mass spectroscopy. Splachnidium rugosum and Laminaria pallida extracts consisted largely of L-fucose, while Ecklonia maxima fucoidan was characterized with high glucose abundance. Crude hot water and acid extracts from Splachnidium rugosum tissue were fractionated and purified by (anionic) ion exchange chromatography as bioactivity has been correlated to lower molecular weight forms. In water extracts, ion exchange chromatography resulted in close to 90% decrease in L-fucose, sulphate and uronic acid, while protein content increased by 57%. Similar results were reported for acid extracts; however protein content did not change significantly. These results show that method of extraction may affect the composition of fucoidan post-purification. Hot water extraction is recommended due to higher fucoidan yield, as reflected by L-fucose content, and higher sulphate-to-fucose ratio. High protein content after ion exchange chromatography was however of concern. Since mucilage in Splachnidium rugosum thallus was free of protein, fucoidan was precipitated from mucilage with ethanol. Fucoidan yield of mucilage was >15-fold higher than content in purified hot water extracts with a sulphate-to-fucose ratio of ~1:1. The average molecular weight of native fucoidan in mucilage was estimated at 2367 kDa. The polysaccharide was hydrolysed by gamma-irradiation levels of 10-50 kGy to fractions ranging between 60 and 15.5 kDa. Hot water crude fucoidan extracts from Ecklonia maxima, Laminaria pallida, and Splachnidium rugosum were assessed for anti-oxidant activity by measuring the ability to scavenge free radicals and the capacity to reduce copper ions with 2,2-Diphenyl-1-picrylhydrazyl and Cupric Reducing Anti-oxidant Capacity assays, respectively. Ecklonia maxima crude fucoidan displayed highest anti-oxidant activity and capacity, having the potential to scavenge reactive oxygen species as well as the capacity to reduce copper to less toxic forms in mammalian systems. Splachnidium rugosum showed weakest anti-oxidant activity and lowest reducing capacity. The anti-cancer activity of crude and purified hot water Splachnidium rugosum extracts, as well as non-irradiated (native) and gamma-irradiated fucoidan, and commercially procured fucoidan were assessed for anti-cancer activity against MCF-7 breast cancer cells. Splachnidium rugosum crude and purified fucoidan displayed a half maximal inhibitory concentration of 0.7 mg/mL and 0.029 mg/mL, respectively. Low cytotoxicity of crude and purified Splachnidium rugosum fucoidan against non-cancerous breast epithelial cell line MCF-12A was observed, as seen by half maximal inhibitory concentration values of 2 mg/mL and 0.663 mg/mL, respectively. The cancer specific selectivity of purified Splachnidium rugosum fucoidan was therefore much higher as reflected by 10-fold higher selectivity index than that of crude fucoidan. Native and low molecular weight gamma-irradiated fucoidan also showed bioactive properties including anti-cancer activity as seen by the reduction of cell proliferation in vitro, whereas crude fucoidan showed the ability to scavenge free radicals, and the capacity to reduce copper ions.National Research Foundatio
Assessing the vulnerability of resource-poor households to disasters associated with climate variability using remote sensing and GIS techniques in the Nkonkobe Local Municipality, Eastern Cape Province, South Africa
No full textThe main objective of the study was to assess the extent to which resource-poor households in
selected villages of Nkonkobe Local Municipality in the Eastern Cape Province of South Africa
are vulnerable to drought by using an improvised remote sensing and Geographic Information
System (GIS)-based mapping approach. The research methodology was comprised of 1)
assessment of vulnerability levels and 2) the calculation of established drought assessment
indices comprising the Normalized Difference Vegetation Index (NDVI) and the Normalized
Difference Water Index (NDWI) from wet-season Landsat images covering a period of 29 years
from 1985 to 2014 in order to objectively determine the temporal recurrence of drought in
Nkonkobe Local Municipality. Vulnerability of households to drought was determined by using
a multi-step GIS-based mapping approach in which 3 components comprising exposure,
sensitivity and adaptive capacity were simultaneously analysed and averaged to determine the
magnitude of vulnerability. Thereafter, the Analytical Hierarchy Process (AHP) was used to
establish weighted contributions of these components to vulnerability. The weights applied to the
AHP were obtained from the 2012 - 2017 Nkonkobe Integrated Development Plan (IDP) and
perceptions that were solicited from key informants who were judged to be knowledgeable about
the subject. A Kruskal-Wallis H test on demographic data for water access revealed that the
demographic results are independent of choice of data acquired from different data providers
(χ
2
(2) = 1.26, p = 0.533, with a mean ranked population scores of 7.4 for ECSECC, 6.8 for
Quantec and 9.8 for StatsSA). Simple linear regression analysis revealed strong positive
correlations between NDWI and NDVI ((r = 0.99609375, R
2 = 1, for 1985), 1995 (r =
0.99609375, R
2 = 1 for 1995), (r = 0.99609375, R
2 = 1 for 2005) and (r = 0.99609375, R
2 = 1 for
2014). The regression analysis proved that vegetation condition depends on surface water arising
from rainfall. The results indicate that the whole of Nkonkobe Local Municipality is susceptible
to drought with villages in south eastern part being most vulnerable to droughts due to high
sensitivity and low adaptive capacity.National Research Foundation (NRF) of South Afric
Hadronic matter: from vacuum to extreme temperature in the presence of magnetic fields
No full textThis work consists of two themes. First, we work with Finite Energy QCD Sum Rules (FESR) approach in the vacuum. We tackle the problem of quark-hadron duality violation (DV), using the vector and axial-vector hadronic spectral function from tau-decay. A pinched integration kernel is introduce in the FESR in order to quench potential duality violations on the real axis in the complex squared energy plane and effectively extend the analysis well beyond the kinematical Ƭ-decay end-point. As the sum rules are well satisfied, we conclude that possible DV must be buried under the experimental uncertainties. Also, using the latest updated ALEPH data on hadron decays, we use FESR to determine the vacuum condensates of dimension d = 2 and d = 4, to check the validity of the Weinberg sum rules, and to determine the chiral condensates of dimension d = 6 and d = 8, and values of the chiral perturbation theory L10 and C87.National Research Foundatio
The development and demonstration of a practical methodology for fine particle shape characterisation in minerals processing
No full textDue to continually declining ore grades, increasing mineralogical complexity, and increasing metal demand, models for the design and optimisation of minerals processing operations are of critical importance. These models do not currently incorporate particle shape, which, although rarely quantified, is known to affect numerous unit operations. Automated Scanning Electron Microscopy (Auto-SEM-EDS) is a widely used tool for mineralogical analysis. It also provides an opportunity for simple, quantitative and mineral-specific shape characterisation. Existing mineralogical databases could therefore become useful resources to facilitate the incorporation of shape effects in minerals processing models. A robust Auto-SEM-EDS shape characterisation methodology is required to ensure that the particle shape information in these databases is interpreted appropriately. For this work, a novel methodology for Auto-SEM-EDS shape characterisation was developed that is suitable for the analysis of fine particles (<75 μm). This involved testing the response of various shape descriptors to image resolution, and measurement with different devices and image processing routines. The most widely used shape descriptor in minerals processing, circularity, was found to be highly dependent on both image resolution and image processing settings, making it a poor choice for shape characterisation of fine particles. Roundness and aspect ratio were found to be more robust descriptors. However, in the interest of being able to compare particulate shape measurements across different studies, the precise definition of aspect ratio is important as variation in 'length' and 'width' definitions can significantly impact aspect ratio measurements. The possibility that preferential orientation of particles would introduce bias to the 2-D cross-sectional measurements was also addressed through comparison of roundness distributions measured from orthogonal cross-sections of a particulate sample mounted within a block of resin. The excellent repeatability of these measurements indicated that the particles were randomly orientated, and thus it can be inferred that 2-D measurements of a sufficient number of particles will be directly related to the particulate sample's 3-D properties. Roundness and aspect ratio were then used in conjunction to produce surface frequency distributions that allow for distinction between non-rounded particles that were smooth and elongated and non-rounded particles that were neither elongated nor smooth. Three applications of the shape characterisation methodology developed were then demonstrated, which highlighted some of the potential contributions that this methodology can make towards minerals processing. The applications were all based on a case study of the Upper Group 2 (UG2) Chromitite, a platinum group mineral (PGM) ore of key economic significance to South Africa.National Research Foundatio
The impact of play-informed caregiver-implemented home-based intervention on the academic learning outcomes for HIV positive children (aged 5 years to 8 years) on Antiretroviral Therapy (ART) living in low income conditions: a randomized control trial
No full textThe academic learning of HIV positive children is often negatively impacted by cognitive and learning deficits associated with HIV, and usually leads to poor performance at school. Occupational therapy, a profession that promotes and enhances participation in meaningful occupations, has yet to demonstrate its impact in promoting the occupation of academic learning in HIV positive children on ART. OBJECTIVES: This study investigates and compares the impact of two occupational therapy interventions; conventional one-on-one occupational therapy (control group) and play-informed caregiver-implemented home-based intervention (PICHIBI) (experimental group), in promoting academic learning for HIV positive children aged 5 to 8 year olds on ART. METHODS: The research project followed a pragmatic, single-blinded, randomised baseline, mid and post-test control-group design. From a possible population of 60 dyads who attend the Groote Schuur Hospital (Cape Town, South Africa) ARV clinic, 27 child-caregiver dyads (n=27) were recruited. One dyad was excluded from the study, due to home circumstances, leaving 26 dyads that went through the randomisation and allocation process into the two intervention groups. Randomisation was carried out by a central computer system, before the start of the intervention period. The final total sample (n=23) completed the intervention, a slight decrease from the recruited sample size. Four dyads were lost to follow up after the baseline test. This resulted in 12 dyads in the control group and 11 dyads in the experimental group. Baseline, mid (after 5 months of the intervention) and post (after 10 months of intervention) test data was collected using the Griffiths Mental Developmental Scales-Extended Revised (GMDS-ER) and the short form Beery-Buktenica Visual Motor Integration test , 5th edition (Beery-VMI) as outcome measures. RESULTS: Following randomisation there were minimal variations in the baseline demographics and measurements for the two groups, with the exception of a significant difference in time on ART (p=.021). The majority of each group had suppressed viral loads. The total sample showed delays in all the performance components linked to academic learning at baseline, that is, low for visual motor integration and visual perception, below average for motor coordination, borderline delay in language, and practical reasoning, and low average in eye hand co-ordination, performance and the overall level of functioning (general quotient). Severe delays (<70) were detected in the control group at baseline for visual perception, and at post test for language. Average scores (90-109) at post test for visual perception and motor co-ordination were only seen in the experimental group. No statistical significance was noted for between-group differences at baseline, mid and post test. For within-group changes, statistically significant improvements were observed in the following performance components linked to academic learning: in the experimental group, visual motor integration from baseline to mid test (p=.019); in the control group, visual perception from baseline to post test (p=.009) and visual perception baseline to mid test (p=.001), and in performance from baseline to mid test (p=.027). Following interventions the overall GMDS-ER quotient scores for both groups improved with 70% of the experimental group and 58.3% of the control group scoring more than -2 z-score. In the total sample, the level of severe delay at baseline (68.2%) improved to only 8 out of the 23 (36.4%) of the total sample showing a severe overall delay post intervention. These scores still classified the groups as below average (90-109) under the GMDS-ER UK classifications. Despite these scores, 95.7% of the total sample progressed to the next grade during intervention, with only one child repeating a grade. CONCLUSION: Improvements were seen in both groups from baseline to post test. The advantage of PICHIBI however is that it is better suited for expanding access to occupational therapy services in a context where the occupational therapist/patient ratio in the public health sector is low. The continued underperformance of both groups in academic learning outcomes post intervention, displays the need for ongoing intervention for HIV-infected school going children. This information will inform occupational therapy practice, guide policies and legislations relating to academic learning for children with HIV on ART, in South Africa. It is recommended that future research look into using a larger sample size for generalisability of findings, consider conducting a longitudinal study linking results with school report outcomes and comparing the effects of the intervention at various levels of health care.National Research Foundatio