Deriving the Metallicity Distribution Function of Galactic Systems

The chemical evolution of the Milky Way is investigated using a dual-phase metal-enriched infall model in which primordial gas fuels the earliest epoch of star formation, followed by the ongoing formation of stars from newly accreted gas. The latest metallicity distribution of local K-dwarfs is reproduced by this model, which allows the Galactic thin disk to form from slightly metal-enriched gas with alpha-element enhancement. Our model predicts ages for the stellar halo and thin disk of 12.5 and 7.4 Gyr, respectively, in agreement with empirically determined values. The model presented in this paper is compared with a similar dual-phase infall model from Chiappini et al. (2001). We discuss a degeneracy that enables both models to recover the K-dwarf metallicity distribution while yielding different star formation histories. The metallicity distribution function (MDF) of K-dwarfs is proposed to be more directly comparable to chemical evolution model results than the G-dwarf distribution because lower mass K-dwarfs are less susceptible to stellar evolutionary effects. The K-dwarf MDF should consequently be a better probe of star formation history and provide a stronger constraint to chemical evolution models than the widely used G-dwarf MDF. The corrections that should be applied to a G-dwarf MDF are quantified for the case of the outer halo of NGC 5128.Comment: 16 pages, 5 figures, accepted for publication in PASA (Publications of the Astronomical Society of Australia

Faecal sludge simulants to aid the development of desludging technologies

This paper presents a review of currently available data from the literature on the undrained shear strength, bulk density, stickiness and debris content of faecal sludge. Those data have been used to develop two different simulants that replicate the full range of shear strengths and densities reported for faecal sludge. Comprehensive specifications are also presented for the debris or solid waste found in latrines to more closely replicate the challenge of pumping faecal sludge. Finally, a design guide has been produced to capture these results and support quantitative performance testing of desludging pumps. The simulants have already been used as part of the Bill &amp; Melinda Gates Foundation's Faecal Sludge Omni-Ingestor project and by Water for People's SaniHub in developing improved desludging pumps. The wider use of these simulants could accelerate the development of pit emptying technologies and help standardize the quantitative evaluation of their performance.</jats:p

Cosmological implications of dwarf spheroidal chemical evolution

The chemical properties of dwarf spheroidals in the local group are shown to be inconsistent with star formation being truncated after the reionization epoch (z~8). Enhanced levels of [Ba/Y] in stars in dwarf spheroidals like Sculptor indicate strong s-process production from low-mass stars whose lifetimes are comparable with the duration of the pre-reionization epoch. The chemical evolution of Sculptor is followed using a model with SNeII and SNeIa feedback and mass- and metallicity-dependent nucleosynthetic yields for elements from H to Pb. We are unable to reproduce the Ba/Y ratio unless stars formed over an interval long enough for the low-mass stars to pollute the interstellar medium with s-elements. This robust result challenges the suggestion that most of the local group dwarf spheroidals are fossils of reionization and supports the case for large initial dark matter halos.Comment: 7 pages, 4 figures. Accepted for publication in ApJ. Minor changes following referee repor

Lebensqualität von Brustkrebspatientinnen bei offener und verschlossener Reaktion auf ein Gesprächs- und Informationsangebot

Da sich die Voraussetzungen in der Nachsorge von Patientinnen mit Brustkrebs im letzten Jahrzehnt verändert haben, wird im Theorieteil der Arbeit auf das Konzept Lebensqualität, die Krankheit Brustkrebs selbst, die aktuellen Nachsorgebedingungen und auf Coping eingegangen. Im Anschluß erfolgt die Darstellung der Ergebnisse von 204 Patientinnen, die zwischen 1996 und 1998 an einem neu diagnostizierten Mammakarzinom erkrankt und operiert worden sind. Die Daten wurden bezüglich der Lebensqualität in der Nachsorgeperiode von einem Jahr ausgewertet. Als Meßinstrument wurde der Quality of Life Questionnaire der EORTC benutzt. Es zeigt sich, daß sich für alle Patientinnen die Lebensqualität im Verlauf von einem Jahr signifikant erhöht. Die Patientinnen, die eine offene Haltung bezüglich eines Informations- und Gesprächsangebots zeigen (n=43), haben zum Zeitpunkt der Klinikentlassung und nach 12 Monaten eine signifikant schlechtere globale Lebensqualität als die verschlossenen Patientinnen (n=12). Die bezüglich des Gesprächs- und Informationsangebots indifferenten Patientinnen (n=149) nehmen einen Mittelplatz ein. Als weiteres Ergebnis zeigt sich ein signifikanter Unterschied zwischen der Selbsteinschätzung der Lebensqualität durch die Patientinnen und der Fremdeinschätzung der Lebensqualität durch die Interviewführenden. Die Patientinnen schätzen ihre globale Lebensqualität signifikant schlechter ein (Mittelwert: 58), als dies in der Fremdeinschätzung durch die Interviewführenden der Fall ist (Mittelwert: 63,2).Die Ergebnisse könnten darauf hindeuten, daß die Offenheit der Patientinnen aus einer inneren Not heraus besteht, während die verschlossenen Patientinnen durch die größere Distanz zum Thema Brustkrebs von einer höheren Lebensqualität profitieren. Die in der Literatur referierten Ergebnisse bezüglich der Selbst- und Fremdeinschätzung der Lebensqualität finden in dieser Studie keine Bestätigung. Es wird deutlich, daß es in der Nachsorge unterschiedliche Reaktionen mit Auswirkung auf die Lebensqualität der Patientinnen gibt; eine Forschungsvertiefung wäre für die bessere Kenntnis der psychosozialen Situation der Patientinnen und nachfolgend für eine Verbesserung der Nachsorge im Sinne der aktuellen Leitlinien wünschenswert

Constraints on Early Nucleosynthesis from the Abundance Pattern of a Damped Ly-alpha System at z = 2.626

We have investigated chemical evolution in the young universe by analysing the detailed chemical enrichment pattern of a metal-rich galaxy at high redshift. The recent detection of over 20 elements in the gas-phase of a damped Lyman-alpha absorber (DLA) at z = 2.626 represents an exciting new avenue for exploring early nucleosynthesis. Given a strict upper age of ~2.5 Gyr and a gas-phase metallicity about one third solar, we have shown the DLA abundance pattern to be consistent with the predictions of a chemical evolution model in which the interstellar enrichment is dominated by massive stars with a small contribution from Type Ia supernovae. Discrepancies between the empirical data and the models are used to highlight outstanding issues in nucleosynthesis theory, including a tendency for Type II supernovae models to overestimate the magnitude of the "odd-even" effect at subsolar metallicities. Our results suggest a possible need for supplemental sources of magnesium and zinc, beyond that provided by massive stars.Comment: 12 pages, 7 figs. Accepted for publication in ApJ (The Astrophysical Journal

Dynamics of a temperate grassland reptile community in the mid-north of South Australia

Published version of the paper reproduced here with permission from the Royal Society of South Australia.Temperate native grasslands are listed as a critically endangered ecological community in South Australia, yet very little is known about the associated faunal communities. This study aims to provide information on the temporal dynamics of a native grassland reptile community in the mid-north of South Australia. During the study we made 335 reptile captures in pitfall traps, of 248 different individuals, from 13 species, representing five families. These data were used to investigate seasonal trends in trapping rate, age demographics and movement of individuals from marked recaptures. The results of the study provide baseline information on species assemblages that might be used in the recovery and management of the remaining fragments of temperate native grasslands and the endangered pygmy bluetongue lizard that relies on those fragments for its persistence.This research was supported by funds from the Australian Research Council

On the origin of fluorine in the Milky Way

The main astrophysical factories of fluorine (19F) are thought to be Type II supernovae, Wolf-Rayet stars, and the asymptotic giant branch (AGB) of intermediate mass stars. We present a model for the chemical evolution of fluorine in the Milky Way using a semi-analytic multi-zone chemical evolution model. For the first time, we demonstrate quantitatively the impact of fluorine nucleosynthesis in Wolf-Rayet and AGB stars. The inclusion of these latter two fluorine production sites provides a possible solution to the long-standing discrepancy between model predictions and the fluorine abundances observed in Milky Way giants. Finally, fluorine is discussed as a possible probe of the role of supernovae and intermediate mass stars in the chemical evolution history of the globular cluster omega Centauri.Comment: 7 pages, 4 figures. MNRAS in pres