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NRF open access statement : implications for grantees’ research output submissions and dissemination
No full textCentres of Excellence Managers’ Workshop took place at theDepartment of Science Technology (DST), Bunga Auditorium, 21 July 2016
NRF open access statement : workflow implementation, repository systems, and technical alignment to the global networked infrastructure for scholarly communication
No full textWhat is Open Science: Open Access, Open Data – Open Scholarship?
NRF Strategy 2020
OA Mandate - Catalysing Knowledge Production for Societal Benefit
Funded Research Outputs
Open Access Repositories
Technical requirements - Cornerstones for Repositories
Repositories Harvesting: Workflows
NRF’s Research Support and Knowledge Networking Databases
The Impact of Open Science-Open Access, Open Data etc…
Readiness and Conclusio
RESEARCH DEVELOPMENT GRANTS FOR Y-RATED RESEARCHERS: Framework Document
No full textThe Research Development grants for Y-Rated Researchers is a ring-fenced, once-off grants
and competitive discipline-based funding instrument aimed at enhancing the efficiency of the
NRF to drive our transformation consistently and strategically through supporting primarily
basic research as the foundation of knowledge production in the disciplines of the Humanities,
Social and Natural sciences.KNOWLEDGE FIELDS DEVELOPMEN
Modelling antenna responses
No full textThis dissertation presents surrogate modelling techniques for the radiation patterns
and scattering parameters of antennas. The models are developed in the context of
calibration of re ector antennas as well as antenna design activities such as design
space exploration, optimisation and sensitivity analysis.
On the calibration front, a method is proposed to recover the radiation pattern,
resulting from some physical deformation of an o set Gregorian re ector antenna,
over a wide frequency bandwidth by taking a few directional measurements at a
single frequency. The proposed technique combines characteristic basis function
patterns (CBFPs) with the linear algebraic notion of subspace projection and is
shown to achieve pattern recovery with better than -40 dB accuracy over a bandwidth
of up to a decade.
Concerning surrogate models for antenna design, models based on the parametrisation
of CBFPs are presented at three levels: (i) CBFPs are parametrised on a
xed grid of EM simulated samples to yield multivariate models of the full radiation
pattern. The associated S-parameters are modelled through an indirect parametrisation
of the poles and residues obtained by tting S-parameter data with rational
functions. (ii) A univariate adaptive sampling algorithm is devised to model the
frequency dependence of the full radiation pattern by judiciously selecting the frequency
samples at which the antenna is simulated. The proposed algorithm is
guaranteed to converge to an accurate model in a modest number of iterations,
thereby improving the e ciency of frequency domain antenna simulations. (iii)
A multivariate adaptive sampling algorithm is devised to model the full radiation
pattern as well as S-parameters as a function of multiple design variables (including
frequency). The proposed adaptive sampling techniques have the additional feature of approximation error control. The proposed surrogate modelling techniques can be used to improve the calibration
e ciency of re ector antennas (since fewer measurements are required for
wideband systems), as well as to improve the design work flow of antennas by
reducing the computational cost of the associated design activities.National Research Foundatio
Evaluation of the effect of low and intermediate frequency electromagnetic waves on radiosensitivity
No full textThe incidence of epidemic Kaposi’s sarcoma in HIV/AIDS patients is high due to their compromised immune system. HIV-positive individuals presenting with cancer tend to be more sensitive to ionizing radiation and are at a higher risk of developing severe side effects during radiotherapy, and there is a need to develop non-invasive methods to preferentially sensitize cancer cells and reduce therapeutic doses.
Here, the effects of 100 and 1000 Hz electromagnetic fields (EMF) broadcast via an argon plasma ray tube at 50 W on the radio sensitivity of apparently normal Chinese hamster lung fibroblasts (V79) and human malignant melanoma cells (MeWo) were evaluated using the colony forming assay. Pre-exposure of the fibroblasts to both fields had no effect on their radio sensitivity, if X-ray irradiation followed within 2 h or at 6 h. Significant radio sensitization was observed when X-rays were administered 4 h after EMF exposure. For the MeWo cells, pre-exposure to 100 Hz resulted in a significant radioprotection when irradiation followed within 6 h. However, treatment of these cells with a 1000 Hz field significantly potentiated the effect of X-rays. When cells were irradiated prior to EMF exposure, the V79 cells were marginally protected by the 100 Hz field and sensitized by the 1000 Hz field. In contrast, the melanoma
cells were slightly protected by the 1000 Hz field and sensitized by the 100 Hz field.
The survival rate of the normal fibroblasts when treated with 2 Gy, in two fractions of 1 Gy 6 h apart, was similar to those obtained when cells received an acute dose of 2 Gy 6 h prior to or after exposure to both EMF frequencies. On the other hand, the melanoma cells were significantly sensitized when they were either treated with a combination of X-rays and then 100 Hz EMF 6 h later or with a combination of either of the EMF frequencies and then X-rays 6 h later. These data suggest that use of electromagnetic fields may sensitize tumours to radiation therapy and reduce normal tissue toxicity. Informed and well-designed combinations of low-medium frequency electromagnetic fields and radiation therapy might be beneficial in the management of cancers, especially epidemic Kaposi’s sarcoma.National Research Foundatio
Immunological tools for the characterization of the humoral immune response to Mycobacterium bovis infection in African buffaloes (Syncerus caffer)
No full textNational Research Foundatio
Steady-state analysis of continuous succinic acid fermentations by actinobacillus succinogenes
No full textSuccinic acid (SA) is poised to become a significant building-block or platform chemical in the bio-based economy. Of the microbial strains that show promise for biological SA production, the wild-type bacterium Actinobacillus succinogenes is one of the top-contenders. While strides have been made towards understanding the behaviour of the organism and developing the fundamentals for an industrial process based on the organism, there is still a large scope of research required and a multitude of challenges to be addressed. In particular, an improved understanding of the metabolism of the organism under favourable biofilm conditions is required and its potential as a microbial host in a biorefinery setting needs to be established. Therefore, the aim of this thesis is to develop a fundamental understanding of the central metabolism of the organism under biofilm conditions on relevant substrates, and to determine its performance as a SA producer on scalable biorefinery streams. Continuous operation is chosen as the processing mode as it allows for both reactor and metabolic steady-state conditions which facilitates more accurate analysis of fermentation data through metabolic flux balancing, and resembles the foreseeable mode of industrial operation. In addition, fermentations are conducted under biofilm conditions in custom reactors since the organism naturally and unavoidably produces biofilm, and unique and process-favourable metabolic behaviour has been observed in biofilms of A. succinogenes.
The thesis firstly assesses the performance of the organism on xylose in relation to the model substrate glucose, since both these carbohydrates constitute major fractions of renewable feedstocks, especially lignocellulosic biomass. Continuous biofilm fermentations reveal that A. succinogenes is able to effectively ferment xylose to SA. However, although xylose consumption rates are similar to those of glucose at dilution rates of 0.05, 0.10 and 0.30 h-1, lower yields (0.55 – 0.68 g g-1) and SA productivities (1.5 – 3.4 g L-1 h-1) are achieved. SA titres of between 10.9 and 29.4 g L-1 are attained with SA-to-acetic acid ratios between 3.0 and 5.0 g g-1. In addition, pyruvic acid formation is found to be substantially greater in xylose fermentations (1.2 – 1.9 g L-1) as detected by means of a modified HPLC method. In agreement with glucose fermentations, increased SA yields on xylose are observed at increasing SA tires indicating increased carbon flux to SA. Mass balance closures on xylose (80.6 to 85.3%) are shown to be lower than those on glucose, and are incomplete for both substrates. Furthermore, redox balances suggest that the central metabolic network, based on measurements of excreted metabolites, is unable to produce the required reduction power (as NADH) to account for the measured SA concentration. A possible source of the reduction power is the oxidative pentose phosphate pathway (OPPP).
Following the findings of the first portion of the thesis, the second section further investigates the metabolic behaviour of A. succinogenes. To probe the metabolic flux distributions beyond the limitations of metabolite-based flux balancing and to explore the hypothesis of the OPPP serving as the source of additional reduction power, assays of glucose-6-phosphate dehydrogenase (G6PDH) are performed on cell extracts of biofilm removed in situ during fermentations. A kinetic model of the assay data, based on Michaelis-Menten kinetics, is developed in vitro to estimate flux into the OPPP from glycolysis at the glucose-6-phosphate node. From the kinetic model it is found that G6PDH rates, normalised to cell concentration and substrate uptake rate, increase with increasing SA titre, corresponding to increasing deviations in the redox balance. Furthermore, metabolic flux models that include OPPP flux show similar trends to those observed through the kinetic models. Therefore, evidence of the OPPP leading to increased SA yields is provided. The OPPP generates reduction power as NADPH which can be converted to NADH by transhydrogenase, thereby facilitating additional flux through the reductive branch of the TCA cycle, wherein SA is produced, and closing the redox balance.
The final portion of the thesis explores the applied potential of A. succinogenes as a microbial platform for SA production in a biorefinery context. Fermentations of non-detoxified, deacetylated, dilute acid pretreated, corn stover hydrolysate (DDAP-H) are performed in a continuous reactor fitted with a novel agitator fixture capable of supporting biofilm to increase cell density. A. succinogenes is found to achieve competitive yields (0.78 g g-1), titres (39.6 g L-1) and productivities (1.8 g L-1h-1) on DDAP-H at dilution rates of 0.02, 0.03, 0.04 and 0.05 h-1. Furthermore, the organism is able to handle putative microbial inhibitors such as furfural and hydroxymethyfurfural (HMF) through conversion to less inhibitory compounds, likely the alcohol counterparts. However, it is found that continuous operation at reasonable productivities is only possible by starting at low dilution rates (~0.01 h-1) after initial batch operation, then gradually increasing the throughput to allow the culture to adapt – even under complete conversion of furfural and HMF. Various lignin-derived, low molecular weight phenolic compounds are shown to be present in the feed and increase during fermentation suggesting a possible link to the observed inhibition and the need for an acclimatisation phase.
Overall this thesis demonstrates that biofilms of A. succinogenes have the potential to produce SA at enhanced yields and productivities on glucose, xylose and process-relevant biorefinery streams under continuous operation. Furthermore, insight is provided into the unique metabolic behaviour of the organism under non-growth conditions where increased OPPP flux generates reduction power capable of sustaining increased flux to SA. In future work, this advantageous behaviour should be leveraged to develop a process capable of homosuccinate production with A. succinogenes, particularly employing a biorefinery stream as feedstock.National Research Foundatio
SAASTA science engagement highlights report 2015/2016
No full textThe National Research Foundation (NRF) acknowledges
the role of science engagement in the achievement of
its strategic goals.
To fully realise the social, economic and environmental
benefits of the significant investment in science,
research and innovation, the NRF endeavours to
engage the wider community more fully in science and
in an understanding of the knowledge economy.
One of its business units, the South African Agency
for Science and Technology Advancement (SAASTA)
is tasked with facilitating the communication and
advancement of science. SAASTA and the NRF’s
national research facilities interact closely with a network
of science centres, higher education institutions,
science councils, professional science associations
and a host of other science-based entities at national
and international levels to engage the public in science,
engineering and technology.
All science promotion or awareness programmes within
the NRF reside under three key strategic areas that
combine to form an integrated and seamless approach.
The three areas are interdependent, each enhancing
the effectiveness of the other – often an educational
event will also enhance science awareness or a science
communication intervention in the media will add to
readers’ education
Expectations: PhD examination meeting the expectations of examiners
No full textPresentations SA PhD Project Conference: Gauteng Province 11 Otober 2016