Publications

Bulk properties and stability of the entire series of group 4d transition metal carbides and nitrides are reported in this work. The theoretical calculations were carried out within Local Density Approximation and Generalized Gradient Approximation using the Perdew, Burke and Ernzerhof exchange correlation functional. The generalized gradient approximation predictions were found to be closer to experimental values than the local density approximation predictions. In particular, LDA predictions were found to overestimate bulk moduli properties by as much as 5.6–11.5% while equilibrium lattice constants were found to be underestimated by as much as 0.2–5% compared to experimental values. On the other hand, GGA calculations were found to overestimate the lattice parameters by 0.2–6.9%, while underestimating the bulk moduli by as much as 0.07–5%. Out of the carbides considered, TcC and RuC were found to have the highest values of bulk moduli while YC and CdC had the lowest. Similarly, out of the nitrides, MoN and TcN were found to exhibit the largest bulk moduli, indicating that they were the hardest, while CdN had the lowest value and hence relatively softer. Overall, the nitrides presented higher values of bulk moduli than the carbides, an observation that is well supported by their correspondingly shorter bondlengths. The cohesive and structural properties of the 4d transition metal carbides and nitrides are also reported.

The relative rarity of hypertrophic pyloric stenosis (HPS) in the developing world makes its diagnosis a challenge to many physicians. This study audits the management of HPS at a tertiary hospital in South Africa, with a view to defining its regional pattern. This is a retrospective review of records of all patients (n = 63) managed for HPS over an eight-year period (2002–2010). The mean age at presentation was 6.2 weeks and the male/female ratio was 6:1. The majority of patients presented with non-bilious vomiting. Abdominal ultrasound had a sensitivity of 65% and 81.3% when the criteria of pyloric muscle thickness >4 mm and pyloric channel length >16 mm were used, respectively. The overall complication rate was 14.3% and the mortality rate was 0%. Despite the rarity of HPS in the Third World, the outcome of its management is favourable. However, the sensitivity of abdominal ultrasound for diagnosing HPS is low.