The absence of diffusion in the South African short rate

In the field of Financial Mathematics, stochastic differential equations are used to describe the dynamics of interest rates. An example is a model for the short rate, which is a mathematically defined rate not directly observable in any market. However, observable rates such as short dated Treasury rates or the Johannesburg Interbank Agreement Rate (JIBAR) can be used as proxies for the short rate.The short rate dynamics are traditionally modelled by one-factor diffusion processes. These type of models remain popular due to the analytical tractability of the pricing formulae of interest rate derivatives under these models. To capture the leptokurtic nature of interest rate returns in the South African market, two types of models can be used: a pure jump model or a jump diffusion model. In this paper we investigate whether jumps are present and whether a diffusion component is evident. Our initial investigation showed that jumps were present in the South African market, and that no diffusion component was evident at low interest rate levels. This result was found using a Monte Carlo method to test for jumps. We therefore conclude that a pure jump process is an appropriate model for the South African short rate

Multidisciplinary Training to Undergraduate Students in the Faculty of Health Sciences: Hypertension as a Case Study

Background: Healthcare students should be aware of the specific skills, knowledge and management options of other disciplines in order to achieve an effective and cohesive working relationship. Aim: The aim of this study was to expose healthcare students at the University of the Free State to one another\'s domains, as related to hypertension management, during a formal didactic lecture attended by medical, physiotherapy and dietetic students, and to determine whether they could apply in practice the theoretical knowledge regarding blood pressure measurement and exercise, obtained during a multidisciplinary session. The perceptions of students regarding multidisciplinary sessions were also to be obtained. Method: Students received a formal lecture on hypertension from a medical doctor, a dietitian, a physiotherapist and an occupational therapist and they then worked in multidisciplinary groups to demonstrate the physiological effect of exercise on blood pressure and pulse rate. Students had to report their findings and perceptions of the session by completing data forms. Results: A total of 125 medical, physiotherapy and human nutrition students participated in the session. The students were able to demonstrate the influence of exercise on blood pressure and pulse measurements. They reported that they enjoyed the multidisciplinary session and gained information on the scope of practice of the domains of the other disciplines. Negative feedback was received on the size of the groups and lack of equipment. Conclusion: The students could apply theoretical knowledge in practice and all gave positive feedback. The sessions will continue in the current format but attention will be given to smaller groups and the availability of more equipment. South African Journal of Family Practice Vol. 50 (4) 2008: pp. 70a-70

Conceptualizing human resilience in the face of the global epidemiology of cyber attacks

Computer security is a complex global phenomenon where different populations interact, and the infection of one person creates risk for another. Given the dynamics and scope of cyber campaigns, studies of local resilience without reference to global populations are inadequate. In this paper we describe a set of minimal requirements for implementing a global epidemiological infrastructure to understand and respond to large-scale computer security outbreaks. We enumerate the relevant dimensions, the applicable measurement tools, and define a systematic approach to evaluate cyber security resilience. From the experience in conceptualizing and designing a cross-national coordinated phishing resilience evaluation we describe the cultural, logistic, and regulatory challenges to this proposed public health approach to global computer assault resilience. We conclude that mechanisms for systematic evaluations of global attacks and the resilience against those attacks exist. Coordinated global science is needed to address organised global ecrime

Ethnic differences in age of onset and prevalence of disordered eating attitudes and behaviours: a school-based South African study

Objectives: To determine the age of onset and prevalence figures for disordered eating for diverse ethnic groups among a sample of South African schoolgirls. Method: A cross-sectional design was implemented. Two questionnaires were used to elicit prevalence figures and attitudes towards eating. Results: The study population (n = 418) consisted of black and white schoolgirls in various educational phases. Black students were found to experience a significant increase in reported bulimia-associated behaviours in grades seven to nine (mean age 13.7 years) but did not report any significant increases in drive for thinness, body dissatisfaction or poor eating attitudes across the different phases. White students reported significant increases in all measured disordered eating attitudes and behaviours in grades 10-12 (mean age 16.7 years). In grades four to six, black and white students did not differ with respect to their reported disordered eating attitudes and behaviours. However, in grades seven to nine, black students were more likely to report bulimia-associated behaviours than their white counterparts. The most apparent differences emerged in grades 10-12. White students reported significantly higher drive for thinness, greater body dissatisfaction and poorer eating attitudes than their black counterparts. Furthermore, the ethnic differences that emerged during grades seven to nine with respect to bulimia disappeared in grades 10–12. Conclusion: This study fills the hiatus in the existing South African literature with respect to age of onset and prevalence of disordered eating attitudes and behaviours across ethnic boundaries. Furthermore, it creates a foundation for developing appropriate strategies to address eating disorders in the multicultural South African context.Keywords: disordered eating, onset, ethnic groups, EDI, EAT-2

Lexicographic cones and the ordered projective tensor product

We introduce lexicographic cones, a method of assigning an ordered vector space \Lex(S) to a poset $S$, generalising the standard lexicographic cone. These lexicographic cones are then used to prove that the projective tensor cone of two arbitrary cones is a cone, and to find a new characterisation of finite-dimensional vector lattices.Comment: 8 page

The static allometry of sexual and non-sexual traits in vervet monkeys

Sexual traits vary tremendously in static allometry. This variation may be explained in part by body size-related differences in the strength of selection. We tested this hypothesis in two populations of vervet monkeys, using estimates of the level of condition dependence for different morphological traits as a proxy for body size-related variation in the strength of selection. In support of the hypothesis, we found that the steepness of allometric slopes increased with the level of condition dependence. One trait of particular interest, the penis, had shallow allometric slopes and low levels of condition dependence, in agreement with one of the most consistent patterns yet detected in the study of allometry, namely that of genitalia exhibiting shallow allometries.This research was supported by NIH grant R01RR0163009

Effect of controlled breeding on performance of beef cattle in Central Bushveld bioregion

In most extensive beef production systems in South Africa, calves are weaned at specific dates. This implies that cows that calve late in the season wean younger and lighter calves. In the current study, Bonsmara cows were mated naturally after synchronization over six years (2009 - 2014) in an extensive production system on natural veld in the Central Bushveld bioregion. Within the herd, 50% of cows were synchronized prior to the commencement of the summer breeding season and they were mated naturally for 90 days. The results indicated that calving rate did not differ significantly between cows that were synchronized and non- synchronized. However, there was a significant difference between years in calving rate. Oestrous synchronization prior to natural breeding influenced the average days to conception. The difference in percentage of cows that calved within 293 days of the onset of the breeding season between those that were oestrous synchronized and non-synchronized was 15% in favour of the synchronized cows. Although calves from synchronized cows achieved higher average weaning weights, the cost implications of synchronization offset the benefit of higher calf weights. Keywords: calving rate, oestrous synchronization, natural breedin

Identifying sequence variation in cation channel sperm associated genes in Cape mountain zebra (Equus zebra zebra)

The Cape mountain zebra (Equus zebra zebra) has recovered from near extinction over more than eight decades. While their numbers have increased, populations remain isolated with low genetic diversity. With more than 75 new populations being founded and more than 4800 extant animals, conservation management strategies are being implemented to mitigate risk of losses in genetic diversity and reproductive fitness. One objective is to identify reproductive characteristics that may improve population growth. Cation channel sperm (CatSper) genes play an important role in hyperactivation of sperm during fertilization. Mutations in these genes lead to reduced fertility and even infertility. Ten male zebras were sampled from a group that were translocated in 2016 in order to found a new population. Single nucleotide polymorphisms (SNPs) were identified in three of the CatSper genes (1 - 3). Lack of variation was observed in all exons, with only four SNPs being identified in the intronic regions in close proximity to exons 1, 2, 7, 8, and 9 of CatSper 1. These results may contribute to the pre-identification of males for new founder populations to ensure population growth and viability, and may be a useful tool for selection against low-producing individuals