Histamine and Tyramine Content of South African Wine

The histamine content of 184 wines and tyramine content of 156 wines, produced in South Africa was measured. The histamine and tyramine content of the wine was found to be similar to those of wines produced in other countries. The average histamine content of South African red wines that had undergone malo-lactic fermentation was more than double that of red wines that had not undergone malo-lactic fermentation. All the red wines containing relatively large amounts of histamine had pH's above 3, 7. Six selected strains of malo-lactic bacteria were tested for their ability to form histamine and tyramine in white and red wine. No histamine or tyramine was formed

Quantifying Long-Term Urban Grassland Dynamics: Biotic Homogenization and Extinction Debts

Sustainable urban nature conservation calls for a rethinking of conventional approaches. Traditionally, conservationists have not incorporated the history of the landscape in management strategies. This study shows that extant vegetation patterns are correlated to past landscapes indicating potential extinction debts. We calculated urban landscape measures for seven time periods (1938–2019) and correlated it to three vegetation sampling events (1995, 2012, 2019) using GLM models. We also tested whether urban vegetation was homogenizing. Our results indicated that urban vegetation in our study area is not currently homogenizing but that indigenous forb species richness is declining significantly. Furthermore, long-term studies are essential as the time lags identified for different vegetation sampling periods changed as well as the drivers best predicting these changes. Understanding these dynamics are critical to ensuring sustainable conservation of urban vegetation for future citizens

Developing an ionospheric map for South Africa

The development of a map of the ionosphere over South Africa is presented in this paper. The International Reference Ionosphere (IRI) model, South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were combined within their own limitations to develop an accurate representation of the South African ionosphere. The map is essentially in the form of a computer program that shows spatial and temporal representations of the South African ionosphere for a given set of geophysical parameters. A validation of the map is attempted using a comparison of Total Electron Content (TEC) values derived from the map, from the IRI model, and from Global Positioning System (GPS) measurements. It is foreseen that the final South African ionospheric map will be implemented as a Space Weather product of the African Space Weather Regional Warning Centre

Application of neural networks to South African GPS TEC modelling

The propagation of radio signals in the Earth’s atmosphere is dominantly affected by the ionosphere due to its dispersive nature. Global Positioning System (GPS) data provides relevant information that leads to the derivation of total electron content (TEC) which can be considered as the ionosphere’s measure of ionisation. This paper presents part of a feasibility study for the development of a Neural Network (NN) based model for the prediction of South African GPS derived TEC. The South African GPS receiver network is operated and maintained by the Chief Directorate Surveys and Mapping (CDSM) in Cape Town, South Africa. Vertical total electron content (VTEC) was calculated for four GPS receiver stations using the Adjusted Spherical Harmonic (ASHA) model. Factors that influence TEC were then identified and used to derive input parameters for the NN. The well established factors used are seasonal variation, diurnal variation, solar activity and magnetic activity. Comparison of diurnal predicted TEC values from both the NN model and the International Reference Ionosphere (IRI-2001) with GPS TEC revealed that the IRI provides more accurate predictions than the NN model during the spring equinoxes. However, on average the NN model predicts GPS TEC more accurately than the IRI model over the GPS locations considered within South Africa

Development of a regional GPS-based ionospheric TEC model for South Africa

Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data

From representation to emergence: complexity's challenge to the epistemology of schooling

In modern,Western societies the purpose of schooling is to ensure that school-goers acquire knowledge of pre-existing practices, events, entities and so on.The knowledge that is learned is then tested to see if the learner has acquired a correct or adequate understanding of it. For this reason, it can be argued that schooling is organised around a representational epistemology: one which holds that knowledge is an accurate representation of something that is separate from knowledge itself. Since the object of knowledge is assumed to exist separately from the knowledge itself, this epistemology can also be considered ‘spatial.’ In this paper we show how ideas from complexity have challenged the ‘spatial epistemology’ of representation and we explore possibilities for an alternative ‘temporal’ understanding of knowledge in its relationship to reality. In addition to complexity, our alternative takes its inspiration from Deweyan ‘transactional realism’ and deconstruction. We suggest that ‘knowledge’ and ‘reality’ should not be understood as separate systems which somehow have to be brought into alignment with each other, but that they are part of the same emerging complex system which is never fully ‘present’ in any (discrete) moment in time. This not only introduces the notion of time into our understanding of the relationship between knowledge and reality, but also points to the importance of acknowledging the role of the ‘unrepresentable’ or ‘incalculable’. With this understanding knowledge reaches us not as something we receive but as a response, which brings forth new worlds because it necessarily adds something (which was not present anywhere before it appeared) to what came before. This understanding of knowledge suggests that the acquisition of curricular content should not be considered an end in itself. Rather, curricular content should be used to bring forth that which is incalculable from the perspective of the present. The epistemology of emergence therefore calls for a switch in focus for curricular thinking, away from questions about presentation and representation and towards questions about engagement and response

Electrical conductivity of dispersions: from dry foams to dilute suspensions

We present new data for the electrical conductivity of foams in which the liquid fraction ranges from two to eighty percent. We compare with a comprehensive collection of prior data, and we model all results with simple empirical formul\ae. We achieve a unified description that applies equally to dry foams and emulsions, where the droplets are highly compressed, as well as to dilute suspensions of spherical particles, where the particle separation is large. In the former limit, Lemlich's result is recovered; in the latter limit, Maxwell's result is recovered

EIA decision-making and administrative justice:An empirical analysis

Environmental impact assessment (EIA) is implemented in most countries as an administrative procedure. In this context, it is subject to the principles of administrative justice. However, to date, no empirical research has been conducted to determine the extent to which EIA decisions comply with the principles of administrative justice. In this paper, empirical data from 42 EIA cases in South Africa are used to establish EIA compliance with the administrative justice principles of lawfulness, procedural fairness and reasonableness. This is achieved by measuring EIA decisions against specially developed key performance indicators (KPIs). Overall, decisions were found to mostly comply with the principles of administrative justice. However, questions arise with regards to the quality and substance of the information feeding into the decision-making process and on which decisions are ultimately based

A universal framework for Space Resource Utilisation (SRU)

Space Resource Utilisation (SRU) or In Situ Resource Utilisation (ISRU) is the use of natural resources from the Moon, Mars and other bodies for use in situ or elsewhere in the Solar System. The implementation of SRU technologies will provide the breakthrough for humankind to explore further into space. A range of extraction processes to produce usable resources have been proposed, such as oxygen production from lunar regolith, extraction of lunar ice and construction of habitation by 3D printing. Practical and successful implementation of SRU requires that all the stages of the process flowsheet (excavation, beneficiation and extraction) are considered. This requires a complete ‘mine-to-market’ type approach, analogous to that of terrestrial mineral extraction. One of the key challenges is the unique cross-disciplinary nature of SRU; it integrates space systems, robotics, materials handling and beneficiation, and chemical process engineering. This is underpinned by knowledge of the lunar or planetary geology, including mineralogy, physical characteristics, and the variability in local materials. Combining such diverse fields in a coordinated way requires the use of a universal framework. The framework will enable integration of operations and comparison of technologies, and will define a global terminology to be used across all fields. In this paper, a universal SRU flowsheet and terminology are described, and a matrix approach to describing regolith characteristics specifically for SRU is proposed. This is the first time that such an approach has been taken to unify this rapidly-developing sector