Stability of planets in triple star systems

Context: Numerous theoretical studies of the stellar dynamics of triple systems have been carried out, but fewer purely empirical studies that have addressed planetary orbits within these systems. Most of these empirical studies have been for coplanar orbits and with a limited number of orbital parameters. Aims: Our objective is to provide a more generalized empirical mapping of the regions of planetary stability in triples by considering both prograde and retrograde motion of planets and the outer star; investigating highly inclined orbits of the outer star; extending the parameters used to all relevant orbital elements of the triple's stars and expanding these elements and mass ratios to wider ranges that will accommodate recent and possibly future observational discoveries. Methods: Using N-body simulations, we integrated numerically the various four-body configurations over the parameter space, using a symplectic integrator designed specifically for the integration of hierarchical multiple stellar systems. The triples were then reduced to binaries and the integrations repeated to highlight the differences between these two types of system. Results: This established the regions of secular stability and resulted in 24 semi-empirical models describing the stability bounds for planets in each type of triple orbital configuration. The results were then compared with the observational extremes discovered to date to identify regions that may contain undiscovered planets.Comment: 12 pages, 8 figures, 14 tables. Accepted for publication in Astronomy & Astrophysic

Comparative population genetics of the German shepherd dog in South Africa

Modern breeding practices strive to achieve distinctive phenotypic uniformity in breeds of dogs, but these strategies are associated with the inevitable loss of genetic diversity. Thus, in parallel with the morphological variation displayed by breeds, purebred dogs commonly express genetic defects as a result of the inbreeding associated with artificial selection and the reduction of selection against disease phenotypes. Microsatellite marker analyses of 15 polymorphic canine loci were used to investigate measures of genetic diversity and population differentiation within and between German-bred and South African-bred German shepherd dogs. These data were quantified by comparison with typically outbred mongrel or crossbred dogs. Both the imported and locally-bred German shepherd dogs exhibited similar levels of genetic diversity. The breed is characterised by only a moderate loss of genetic diversity relative to outbred dogs, despite originating from a single founding sire and experiencing extensive levels of inbreeding throughout the history of the breed. Non-significant population differentiation between the ancestral German and derived South African populations indicates sufficient contemporary gene flow between these populations, suggesting that migration resulting from the importation of breeding stock has mitigated the effects of random genetic drift and a population bottleneck caused by the original founder event in South Africa. Significant differentiation between the combined German shepherd dog population and the outbred dogs illustrates the effects of selection and genetic drift on the breed since its establishment just over 100 years ago

Looking and learning: using participatory video to improve health and safety in the construction industry

Construction health and safety (H&S)is usually managed using a top-down approach of regulating workers' behaviour through the implementation and enforcement of prescriptive rules and procedures. This management approach privileges technical knowledge over knowledge based on workers' tacit and informal ways of knowing about H&S. The aim is to investigate the potential for participatory video to: (1) identify areas in which formal policies and procedures do not reflect as practised by workers; (2) encourage creative thinking and elicit workers' ideas for H&S improvements; and (3) provide an effective mechanism for capturing and sharing tacit H&S knowledge in construction organizations. Interviews were conducted in two case study organizations (CSOs) in the Australian construction industry. The results suggest reflexive participatory video enabled workers and managers to view their work practices from a different perspective. Workers identified new hazards, reflected about the practical difficulties in performing work in accordance with documented procedures and reframed their work practices and developed safer ways of working. Workers described how the participatory video capturing the way they work enabled them to have more meaningful input into H&S decision-making than they had previously experienced. Workers also expressed a strong preference for receiving H&S information in a visual format and commented that video was better suited to communicating H&S 'know how' than written documents. The research is significant in providing initial evidence that participatory video has the potential to improve H&S in construction