Minimal knotted polygons in cubic lattices

An implementation of BFACF-style algorithms on knotted polygons in the simple cubic, face centered cubic and body centered cubic lattice is used to estimate the statistics and writhe of minimal length knotted polygons in each of the lattices. Data are collected and analysed on minimal length knotted polygons, their entropy, and their lattice curvature and writhe

The Compressibility of Minimal Lattice Knots

The (isothermic) compressibility of lattice knots can be examined as a model of the effects of topology and geometry on the compressibility of ring polymers. In this paper, the compressibility of minimal length lattice knots in the simple cubic, face centered cubic and body centered cubic lattices are determined. Our results show that the compressibility is generally not monotonic, but in some cases increases with pressure. Differences of the compressibility for different knot types show that topology is a factor determining the compressibility of a lattice knot, and differences between the three lattices show that compressibility is also a function of geometry.Comment: Submitted to J. Stat. Mec

Adsorbed self-avoiding walks subject to a force

We consider a self-avoiding walk model of polymer adsorption where the adsorbed polymer can be desorbed by the application of a force. In this paper the force is applied normal to the surface at the last vertex of the walk. We prove that the appropriate limiting free energy exists where there is an applied force and a surface potential term, and prove that this free energy is convex in appropriate variables. We then derive an expression for the limiting free energy in terms of the free energy without a force and the free energy with no surface interaction. Finally we show that there is a phase boundary between the adsorbed phase and the desorbed phase in the presence of a force, prove some qualitative properties of this boundary and derive bounds on the location of the boundary

Preventative foot care in people with diabetes: Quality patient education

Foot ulceration and amputation cause extensive burden on individuals and health care systems. One of the reasons for the poor outcome offoot complications in developing countries is the lack of patient education. Due to the multi-factorial pathology of diabetic foot ulceration, the person with diabetes should receive health education which is tailored to the individual’s risk status, promote self care and address misconceptions. It is therefore recommended that providers of foot care should participate in ongoing professional education development programmes to obtain skills to assist people in adopting positive self-care behaviour.Keywords: preventative foot care; diabetes; risk stratification: self car

A simple model of a vesicle drop in a confined geometry

We present the exact solution of a two-dimensional directed walk model of a drop, or half vesicle, confined between two walls, and attached to one wall. This model is also a generalisation of a polymer model of steric stabilisation recently investigated. We explore the competition between a sticky potential on the two walls and the effect of a pressure-like term in the system. We show that a negative pressure ensures the drop/polymer is unaffected by confinement when the walls are a macroscopic distance apart

Manufacturing challenges for custom made solar vehicles in South Africa

Solar challenges are designed to test the reliability and efficiency of solar powered vehicles in endurance races. In the past these manufactured vehicles were technology drivers and led to advances in electric motors and solar cell efficiency. The speed in relation to power consumption is one of the main design considerations, with the only energy source being solar power. In the design and manufacturing of these vehicles a number of requirements need to be met in order to pass the safety standards. The Sasol Solar Challenge (SSC) created an opportunity for South African universities to design and manufacture custom made solar powered vehicles. This paper explores and discusses the challenges for manufacturing solar vehicles in South Africa. Key elements like the communication gap between design and manufacturing, the cost of lightweight solar encapsulation, the shortage of local suppliers and expertise in composite manufacturing are evaluated. These insights can be used as foundation for strategic decisions by future stakeholders

The perceptions of employment equity and black economic empowerment as predictors of union commitment.

The purpose of the study was to test whether the perceptions of employment equity (EE) and black economic empowerment (BEE) are related to union commitment and whether the perceptions about the mentor’s role significantly mediate this said relationship. The sampling frame for the study constituted 1200 employees of a division of a large public transport organisation and a convenience sample including all 1200 employees yielded 637 fully completed records (a 53% response rate). The results of the study indicate that the perceptions of EE and BEE are significantly related to union commitment, but that perceptions of the mentor’s role do not mediate this relationship. More detailed findings on the study are reported

Vegetation Dynamics in Relation to Land Use within the High Altitude Alpine Grasslands of Lesotho, Southern Africa

The Kingdom of Lesotho is characterized by its unique geographical feature of being dominated by rugged mountainous terrain. It is also the only true alpine region in southern Africa that supports high plant species diversity. Large areas suffer from overgrazing and erosion, as well as over exploitation of its natural resources. The livestock industry in Lesotho has long been a vital component of the economic and social structure of the country and the alpine region is considered as an important grazing resource by local Basotho herdsmen. Consequently, a study was conducted with the two objectives: to determine the phytomass, grazing capacity and crude protein of the vegetation in two areas of the Lesotho alpine grassland with different grazing histories, and to assess the vegetation dynamics in relation to land use with specific reference to productivity, degradation and sustainability