Stratification of the elements in the atmospheres of blue horizontal-branch stars

Blue horizontal-branch (BHB) stars with $T_{\rm eff}$ approximately larger than 11500 K show several observational anomalies. In globular clusters, they exhibit low rotational velocities, abundance anomalies (as compared to cluster abundances), photometric jumps and gaps and spectroscopic gravities lower than predicted by canonical models. It is commonly believed that the low rotational velocities of these stars permit atomic diffusion to be efficient in their atmosphere thereby causing the observed anomalies. Recent detections of vertical stratification of iron (and some other chemical elements) in several BHB stars concur with this framework. In this paper, improved model atmospheres that include the vertical stratification of the elements are applied to BHB stars to verify if they can explain their observational anomalies. The results from theoretical model atmospheres are consistent with the photometric jumps and gaps observed for BHB stars in globular clusters. It is found that iron stratification in the theoretical models and that obtained from observations have similar tendancies. Our results also show that the spectroscopic gravities obtained while using chemically homogeneous model atmospheres to fit observations are underestimated. These results significantly strengthen the belief that atomic diffusion is responsible for these BHB-star anomalies.Comment: 6 pages, 6 figure

CP and related phenomena in the context of Stellar Evolution

We review the interaction in intermediate and high mass stars between their evolution and magnetic and chemical properties. We describe the theory of Ap-star `fossil' fields, before touching on the expected secular diffusive processes which give rise to evolution of the field. We then present recent results from a spectropolarimetric survey of Herbig Ae/Be stars, showing that magnetic fields of the kind seen on the main-sequence already exist during the pre-main sequence phase, in agreement with fossil field theory, and that the origin of the slow rotation of Ap/Bp stars also lies early in the pre-main sequence evolution; we also present results confirming a lack of stars with fields below a few hundred gauss. We then seek which macroscopic motions compete with atomic diffusion in determining the surface abundances of AmFm stars. While turbulent transport and mass loss, in competition with atomic diffusion, are both able to explain observed surface abundances, the interior abundance distribution is different enough to potentially lead to a test using asterosismology. Finally we review progress on the turbulence-driving and mixing processes in stellar radiative zones.Comment: Proceedings of IAU GA in Rio, JD4 on Ap stars; 10 pages, 7 figure

Blue Straggler Stars in Globular Clusters: a powerful tool to probe the internal dynamical evolution of stellar systems

This chapter presents an overview of the main observational results obtained to date about Blue Straggler Stars (BSSs) in Galactic Globular Clusters (GCs). The BSS specific frequency, radial distribution, chemical composition and rotational properties are presented and discussed in the framework of using this stellar population as probe of GC internal dynamics. In particular, the shape of the BSS radial distribution has been found to be a powerful tracer of the dynamical age of stellar systems, thus allowing the definition of the first empirical "dynamical clock".Comment: Chapter 5, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe

Suburethral slingplasty evaluation study in North Queensland,\ud Australia: the SUSPEND trial

Objective:\ud To compare the safety and efficacy of three types of suburethral slings for the treatment of urodynamic stress incontinence.\ud \ud Methods:\ud Following ethics approval, 195 (3 × 65) patients with urodynamic stress incontinence were randomly assigned to undergo suburethral slingplasty with the Tension-free Vaginal Tape (TVT; Gynecare, Ethicon, Somerville, NJ, USA), Intravaginal Sling (IVS; Tyco Healthcare, Mansfield, MA, USA), or Suprapubic Arc Sling (SPARC; American Medical Systems, Minnetonka, MN, USA). The patients were blinded to the type of sling implanted.\ud \ud Main outcome measures were:\ud (1) operative and short-term complications; (2) pre- and postoperative symptomatology; and (3) pre- and postoperative urodynamic findings.\ud \ud Results:\ud There was a statistically significant increased rate of sling protrusion (13.1% vs. 3.3% and 1.7%; P = 0.04) in the SPARC group when compared to TVT and IVS. Otherwise, there were no significant differences between the groups with respect to the incidences of other operative complications, patients' main subjective outcomes, satisfaction rates, or postoperative urodynamic findings. The overall objective stress incontinence cure rates were 87.9%, 81.5% and 72.4% for the TVT, IVS, SPARC groups respectively (P = 0.11).\ud \ud Conclusions:\ud All three slings appear quite successful for the treatment of stress incontinence. The SPARC tapes showed more sling protrusion complications and a trend towards lower objective cure rates; probably as a result of the insertion method used in this study which favoured a loose SPARC sling placement. The authors recommend that the SPARC slings be left tighter than TVT, or for the cough test to be carried out

Old star clusters: Bench tests of low mass stellar models

Old star clusters in the Milky Way and external galaxies have been (and still are) traditionally used to constrain the age of the universe and the timescales of galaxy formation. A parallel avenue of old star cluster research considers these objects as bench tests of low-mass stellar models. This short review will highlight some recent tests of stellar evolution models that make use of photometric and spectroscopic observations of resolved old star clusters. In some cases these tests have pointed to additional physical processes efficient in low-mass stars, that are not routinely included in model computations. Moreover, recent results from the Kepler mission about the old open cluster NGC6791 are adding new tight constraints to the models