MODELLING LONG-TERM COMMODITIES: THE DEVELOPMENT OF A SIMULATION MODEL FOR THE SOUTH AFRICAN WINE INDUSTRY WITHIN A PARTIAL EQUILIBRIUM FRAMEWORK

Econometric demand and supply models of agricultural commodities and crops have been around for a long time with extensive research and adaptations being made in the grain and livestock sectors. This much attention has, however, not been afforded to long term commodities. This paper presents a partial equilibrium framework for modelling long term commodities using the South African wine industry as an example. The model structure and important assumptions are presented, after which the usefulness of the model is tested in the form of baseline projections and the analysis of a typical “what if” question. The wine model presented in this paper is housed and maintained in the Bureau for Food and Agricultural Policy (BFAP) at the Department of Agriculture, Western Cape and the Universities of Pretoria and Stellenbosch.wine market, South Africa, partial equilibrium model, Crop Production/Industries, Demand and Price Analysis,

Electronic friction coefficients from the atom-in-jellium model for Z=1−92Z=1-92

The break-down of the Born-Oppenheimer approximation is an important topic in chemical dynamics on metal surfaces. In this context, the most frequently used "work-horse" is electronic friction theory, commonly relying on friction coefficients obtained from density functional theory (DFT) calculations from the early 80s based on the atom-in-jellium model. However, results are only available for a limited set of jellium densities and elements ($Z=1-18$). In this work, these calculations are revisited by investigating the corresponding friction coefficients for the entire periodic table ($Z=1-92$). Furthermore, friction coefficients obtained by including the electron density gradient on the Generalized Gradient Approximation (GGA) level are presented. Finally, we show that spin polarization and relativistic effects can have sizeable effects on these friction coefficients for some elements.Comment: 30 pages, 10 figues, accepted at Physical Review

THE POLITICAL ECONOMY OF FOOD PRICE INFLATION IN SOUTH AFRICA

This paper reports on a study that investigated the increase in food prices in South Africa. It is set against the scenario of an increasing inflation rate since September 2001. The June 2002 STATSSA figures estimated the annual inflation rate (CPIX) at 8.8% with food inflation being the major contributor with an annual increase of 14%. The high unemployment and poverty rate in South Africa has already lead to concerns about the negative impact of these increases on the cost of living for the poorest. In this paper we show that the sharp depreciation of the exchange rate towards the end of 2001 had a major impact on the producer price of maize one of the key agricultural commodities because of its role as a staple food and as an input in the production of white and red meat and other animal products.Demand and Price Analysis, Political Economy,

Development and evaluation of Research-driven Information Systems

We propose to create a methodological framework that can be applied to evaluate Research-driven Information Systems (RdIS) in aconsistent way. This is done by picking those examples of RdISs that have been evaluatedproperly and making those evaluation processes standard. Our proposed methodologicalframework for the evaluation of RdISs can assist IS researchers in selecting the appropriateevaluation methods. Further exploration of the characteristics of RdISs has led to a betterunderstanding on suitable methods to evaluate the potential applicability of RdISs in practice.A study of IS literature revealed that the evaluation of RdISs should be interpretive andmulti-method of nature. An RdIS that was developed in our research group is evaluatedusing a method that was designed with the new methodological knowledge

Give CRISPR a chance : the GeneSprout Initiative

Did you know that a group of early-career researchers launched an initiative enabling open dialog on new plant breeding techniques, such as genome editing? We developed a wide-ranging initiative that aims to facilitate public engagement and provide a platform for young plant scientists to encourage participation in science communication

Star Formation History of a Young Super-Star Cluster in NGC 4038/39: Direct Detection of Low Mass Pre-Main Sequence Stars

We present an analysis of the near-infrared spectrum of a young massive star cluster in the overlap region of the interacting galaxies NGC 4038/39 using population synthesis models. Our goal is to model the cluster population as well as provide rough constraints on its initial mass function (IMF). The cluster shows signs of youth such as thermal radio emission and strong hydrogen emission lines in the near-infrared. Late-type absorption lines are also present which are indicative of late-type stars in the cluster. The strength and ratio of these absorption lines cannot be reproduced through either late-type pre-main sequence (PMS) stars or red supergiants alone. Thus we interpret the spectrum as a superposition of two star clusters of different ages, which is feasible since the 1" spectrum encompasses a physical region of ~90 pc and radii of super-star clusters are generally measured to be a few parsecs. One cluster is young (<= 3 Myr) and is responsible for part of the late-type absorption features, which are due to PMS stars in the cluster, and the hydrogen emission lines. The second cluster is older (6 Myr - 18 Myr) and is needed to reproduce the overall depth of the late-type absorption features in the spectrum. Both are required to accurately reproduce the near-infrared spectrum of the object. Thus we have directly detected PMS objects in an unresolved super-star cluster for the first time using a combination of population synthesis models and pre-main sequence tracks. This analysis serves as a testbed of our technique to constrain the low-mass IMF in young super-star clusters as well as an exploration of the star formation history of young UC HII regions.Comment: 26 pages, 5 figures, accepted for publication in the Astrophysical Journa