Krypton Ion Thruster Performance

Preliminary data were obtained from a 30 cm ion thruster operating on krypton propellant over the input power range of 0.4 to 5.5 kW. The data presented are compared and contrasted to the data obtained with xenon propellant over the same input power envelope. Typical krypton thruster efficiency was 70 percent at a specific impulse of approximately 5000 s, with a maximum demonstrated thrust to power ratio of approximately 42 mN/kW at 2090 s specific impulse and 1580 watts input power. Critical thruster performance and component lifetime issues were evaluated. Order of magnitude power throttling was demonstrated using a simplified power-throttling strategy

Secular evolution in action: central values and radial trends in the stellar populations of boxy bulges

We determine central values and radial trends in the stellar populations of the bulges of a sample of 28 edge-on S0-Sb disk galaxies, 22 of which are boxy/peanut-shaped (and therefore barred). Our principal findings are the following. (1) At a given velocity dispersion, the central stellar populations of galaxies with boxy/peanut-shaped bulges are indistinguishable from those of early-type (elliptical and S0) galaxies. Either secular evolution affects stellar populations no differently to monolithic collapse or mergers, or secular evolution is not important in the central regions of these galaxies, despite the fact that they are barred. (2) The radial metallicity gradients of boxy/peanut-shaped bulges are uncorrelated with velocity dispersion and are, on average, shallower than those of unbarred early-type galaxies. This is qualitatively consistent with chemodynamical models of bar formation, in which radial inflow and outflow smears out pre-existing gradients.Comment: MNRAS Letters accepted. 5 page

Temporal and spatial evolution of a waxing then waning catastrophic density current revealed by chemical mapping

We reconstruct the behavior of a catastrophic sustained radial pyroclastic density current as it waxed then waned during its brief lifespan. By subdividing the deposit into 8 time slices using a chemical tracer, we show that the sustained current initially was topographically restricted, but that its leading edge advanced in all directions, encroaching upon and gradually ascending hills. During peak flow the current reached its maximum extent and overtopped all topographic highs. After this, and while the current direction from source was maintained, the leading edge gradually retreated sourceward. High-resolution analysis of the depositional architecture reveals how the flow dynamics evolved and runout distance of the sustained density current rapidly increased then decreased, reflecting the dominant influence of changing mass flux, as demonstrated in numerical models but not previously distinguished in a natural deposit

Venturing into schools : locating mental health initiatives in complex environments

Schools provide viable settings for mental health promotion initiatives, such as programs to develop students’ social and emotional capabilities (SEC). Complexity in the school environments into which initiatives are introduced, such as diverse student capabilities, school structures, and teachers’ knowledge and confidence, will play an integral role in the success of those initiatives. This paper investigates the environments of schools about to receive the KidsMatter mental heath promotion, prevention and early intervention initiative in Australia, using information sourced from questionnaires about 2598 students and their teachers in 50 Australian primary schools. The focus of the report is on the status of the schools’ work in one of the key focus areas for the intervention, namely students’ SEC. Analysis showed relatively high levels of students’ SEC across the whole sample, but with sub-group differences. Teachers’ attitudes towards SEC learning were highly positive. Teachers’ self-rated knowledge and approaches in dealing with SEC were moderate, and point to requirements for additional pre-service and professional development. The extent of regular and sustained delivery of SEC programs and mental health initiatives in general showed variability, suggesting the need to attend to school systems and structural supports. Implications of these areas of diversity in school environments on the selection and methods of delivery of mental health promotion programs in schools are discussed.peer-reviewe