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

Paediatric cardiac anaesthesia in sickle cell disease : a case series

Sickle cell disease (SCD) is the most common inherited haematological disorder, producing a mutation of the haemoglobin molecule known as haemoglobin S (HbS). The presence of HbS in the erythrocyte makes it prone to sickling - a process which may lead to vaso-occlusive injury, haemolysis and a hypercoagulable state. Sickling is precipitated by dehydration, hypoxia, hypothermia, acidosis and low flow states. Over time, multi-organ damage develops with significant morbidity and mortality. Paediatric patients with SCD and congenital heart defects may require anaesthesia for corrective cardiac surgery on cardiopulmonary bypass (CPB). During the perioperative period these high-risk patients may suffer significant complications when exposed to the conditions that favour erythrocyte sickling. This case series details our experience of four paediatric patients with SCD patients who underwent corrective cardiac surgery at Red Cross War Memorial Children’s Hospital. The pathophysiology is discussed and the perioperative management of transfusion, cardiopulmonary bypass and temperature regulation is highlighted

Evidence-based prescription for cyclo-oxygenase-2 inhibitors in sports injuries

Healthcare professionals are increasingly under pressure to return athletes to play in the shortest possible time. There is limited choice in providing treatment that speeds up tissue repair, while simultaneously maintaining good quality of healing. Inflammation forms a fundamental part in the process of tissue repair. However, excessive inflammation may cause more pain, and limit functional restoration. Although the use of anti-inflammatory treatment in the form of a cyclo-oxygenase-2 inhibitor (coxibs) has been widely recognised as being effective, the potential detrimental effect on tissue repair, as described mainly in animal model studies, needs to be taken into account. The side-effects profile on the gastrointestinal tract favour coxibs over non-traditional NSAIDs. The possible effects on the renal and cardiovascular systems also need to be considered. The prescription of coxibs should be pathology and situation specific. There are no clear guidelines on the correct time of administration and the duration of the course, but it seems that the literature is in agreement that they should be administered for a limited time at the lowest effective dose possible.Keywords: cyclo-oxygenase-2 inhibitors (coxibs), sports injuries, treatmen

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

Lifeview and perception of message in drama

The age-old controversy between church and the arts has not been resolved by a long shot. The ethically repellent in modern art is definitely over-emphasized at the cost of the ethically acceptable. This leads to the question about the Chri­stian response to a play with a non-Christian lifeview, one in which the charac­ters use crude language and in which vulgar actions are indulged in

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

Glioblastoma multiforme has many faces

Glioblastoma multiforme (GBM) is a class of devastating, highly aggressive central nervous system tumours. While the classical appearance is easily recognisable, several variations occur. We present 6 cases of confirmed GBM that illustrate the unusual findings in histological subtypes, early presentation and spread on MRI imaging.http://www.journals.co.za/sama/m_sajr.htm