Two-group randomised, parallel trial of cognitive and exposure therapies for problem gambling: a research protocol

BACKGROUND: Problem gambling is a serious public health concern at an international level where population prevalence rates average 2% or more and occurs more frequently in younger populations. The most empirically established treatments until now are combinations of cognitive and behavioural techniques labelled cognitive behaviour therapy (CBT). However, there is a paucity of high quality evidence for the comparative efficacy of core CBT interventions in treating problem gamblers. This study aims to isolate and compare cognitive and behavioural (exposure-based) techniques to determine their relative efficacy. METHODS: A sample of 130 treatment-seeking problem gamblers will be allocated to either cognitive or exposure therapy in a two-group randomised, parallel design. Repeated measures will be conducted at baseline, mid and end of treatment (12 sessions intervention period), and at 3, 6 and 12 months (maintenance effects). The primary outcome measure is improvement in problem gambling severity symptoms using the Victorian Gambling Screen (VGS) harm to self-subscale. VGS measures gambling severity on an extensive continuum, thereby enhancing sensitivity to change within and between individuals over time. DISCUSSION: This article describes the research methods, treatments and outcome measures used to evaluate gambling behaviours, problems caused by gambling and mechanisms of change. This study will be the first randomised, parallel trial to compare cognitive and exposure therapies in this population. ETHICS AND DISSEMINATION: The study was approved by the Southern Adelaide Health Service/Flinders University Human Research Ethics Committee. Study findings will be disseminated through peer-reviewed publications and conference presentations. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN 12610000828022.David P Smith, Malcolm W Battersby, Peter W Harvey, Rene G Pols, Robert Ladouceu

The occurrence of nitrogen-enhanced metal-poor stars: implications for the initial mass function in the early Galactic halo⋆

Contains fulltext : 103836.pdf (preprint version ) (Open Access

Carbon-enhanced metal-poor stars: effects of binary evolution at low metallicity

Recent spectroscopic surveys have revealed a large number of extremely metal-poor stars in the Galactic halo. Many of these stars are being subjected to detailed spectroscopic analysis, and a surprisingly large fraction, about 25 %, turn out to be carbon-rich stars with enhancements of C by as much as a factor 100. The majority of these carbon-enhanced metal-poor (CEMP) stars also show enhancements of heavy s-process elements, in particular of lead. Many of these stars have been found to be spectroscopic binary systems. Their binarity and abundance patterns strongly suggest that most, possibly all, CEMP stars have been polluted by a companion star while in an advanced stage of evolution, which has long since faded away. They provide strong indications that (1) binary stars were as common among very low-metallicity populations as they are in the Galactic disk and (2) binaries may have played an important role in shaping the abundance patterns of the earliest generations of stars

The elusive origin of Carbon-Enhanced Metal-Poor stars

Contains fulltext : 111272.pdf (publisher's version ) (Open Access)NIC XI

Formation and Evolution of Carbon-Enhanced Metal-Poor Stars

Very metal-poor stars observed in the Galactic halo constitute a window on the primordial conditions under which the Milky Way was formed. A large fraction of these stars show a great enhancement in the abundance of carbon and other heavy elements. One explanation of this observation is that these stars have undergone mass transfer from an AGB binary companion. This scenario is supported by the evidence that these carbon-enhanced metal-poor (CEMP) stars are mostly found in spectroscopic binary systems. We have started a project with the aim to understand several aspects which still need to be clarified: (1) how the abundances of low-mass metal-poor stars evolve after accretion of material from an evolved asymptotic giant branch star, (2) what the consequences of this mass transfer are for the overall population of CEMP stars, and (3) what its implications are for the initial mass function at early epochs

AGB nucleosynthesis at low metallicity: What can we learn from Carbon- and s-elements-enhanced metal-poor stars

CEMP-s stars are very metal-poor stars with enhanced abundances of carbon and s-process elements. They form a significant proportion of the very metal-poor stars in the Galactic halo and are mostly observed in binary systems. This suggests that the observed chemical anomalies are due to mass accretion in the past from an asymptotic giant branch (AGB) star. Because CEMP-s stars have hardly evolved since their formation, the study of their observed abundances provides a way to probe our models of AGB nucleosynthesis at low metallicity. To this end we included in our binary evolution model the results of the latest models of AGB nucleosynthesis and we simulated a grid of 100 000 binary stars at metallicity Z = 0.0001 in a wide range of initial masses and separations. We compared our modelled stars with a sample of 60 CEMP-s stars from the SAGA database of metal-poor stars. For each observed CEMP-s star of the sample we found the modelled star that reproduces best the observed abundances. The result of this comparison is that we are able to reproduce simultaneously the observed abundance of the elements affected by AGB nucleosynthesis (e.g. C, Mg, s-elements) for about 60% of the stars in the sample

Massive Binary Stars and Self-Enrichment of Globular Clusters

Contains fulltext : 111373.pdf (preprint version ) (Open Access)Reading the book of globular clusters with the lens of stellar evolution", Rome, 26-28 November 201

Massive binaries as the source of abundance anomalies in globular clusters

Abundance anomalies observed in globular cluster stars indicate pollution with material processed by hydrogen burning. Two main sources have been suggested: asymptotic giant branch (AGB) stars and massive stars rotating near the break-up limit (spin stars). We propose massive binaries as an alternative source of processed material. We compute the evolution of a 20 M star in a close binary considering the effects of non conservative mass and angular momentum transfer and of rotation and tidal interaction to demonstrate the principle. We find that this system sheds about 10 M of material, nearly the entire envelope of the primary star. The ejecta are enriched in He, N, Na, and Al and depleted in C and O, similar to the abundance patterns observed in gobular cluster stars. However, Mg is not significantly depleted in the ejecta of this model. In contrast to the fast, radiatively driven winds of massive stars, this material is typically ejected with low velocity. We expect that it remains inside the potential well of a globular cluster and becomes available for the formation or pollution of a second generation of stars. We estimate that the amount of processed low-velocity material ejected by massive binaries is greater than the contribution of AGB stars and spin stars combined, assuming that the majority of massive stars in a proto-globular cluster interact with a companion and return their envelope to the interstellar medium. If we take the possible contribution of intermediate mass stars in binaries into account and assume that the ejecta are diluted with an equal amount of unprocessed material, we find that this scenario can potentially provide enough material to form a second generation of low-mass stars, which is as numerous as the first generation of low-mass stars, without the need to make commonly adopted assumptions, such as preferential loss of the first generation of stars, external pollution of the cluster, or an anomalous initial mass function