Dynamical age differences among coeval star clusters as revealed by blue stragglers

Globular star clusters that formed at the same cosmic time may have evolved rather differently from a dynamical point of view (because that evolution depends on the internal environment) through a variety of processes that tend progressively to segregate stars more massive than the average towards the cluster centre. Therefore clusters with the same chronological age may have reached quite different stages of their dynamical history (that is, they may have different dynamical ages). Blue straggler stars have masses greater than those at the turn-off point on the main sequence and therefore must be the result of either a collision or a mass-transfer event. Because they are among the most massive and luminous objects in old clusters, they can be used as test particles with which to probe dynamical evolution. Here we report that globular clusters can be grouped into a few distinct families on the basis of the radial distribution of blue stragglers. This grouping corresponds well to an effective ranking of the dynamical stage reached by stellar systems, thereby permitting a direct measure of the cluster dynamical age purely from observed properties.Comment: Published on the 20 December 2012 issue of Natur

Relativistic Binaries in Globular Clusters

Galactic globular clusters are old, dense star systems typically containing 10\super{4}--10\super{7} stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of hard binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct {\it N}-body integrations and Fokker--Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.Comment: 88 pages, 13 figures. Submitted update of Living Reviews articl

Euclid : I. Overview of the Euclid mission

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015–2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14 000 deg2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance

Longitudinal Antiretroviral Adherence in HIV+ Ugandan Parents and Their Children Initiating HAART in the MTCT-Plus Family Treatment Model: Role of Depression in Declining Adherence Over Time

We conducted a study to assess the effect of family-based treatment on adherence amongst HIV-infected parents and their HIV-infected children attending the Mother-To-Child-Transmission Plus program in Kampala, Uganda. Adherence was assessed using home-based pill counts and self-report. Mean adherence was over 94%. Depression was associated with incomplete adherence on multivariable analysis. Adherence declined over time. Qualitative interviews revealed lack of transportation money, stigma, clinical response to therapy, drug packaging, and cost of therapy may impact adherence. Our results indicate that providing ART to all eligible HIV-infected members in a household is associated with excellent adherence in both parents and children. Adherence to ART among new parents declines over time, even when patients receive treatment at no cost. Depression should be addressed as a potential barrier to adherence. Further study is necessary to assess the long-term impact of this family treatment model on adherence to ART in resource-limited settings

INTESTINAL TRANSPLANTATION - A CLINICAL UPDATE

Background: Until very recently the results of clinical small-bowel transplantation were disappointing. The latest developments indicate, however, that significant improvements have been made towards clinical application of this mode of therapy for patients with short-bowel syndrome. Methods: Because of better immunosuppression and means to treat rejection, morbidity and mortality after small-bowel transplantation have been reduced and patient and graft survival has increased. Results: Septic complications and abnormal intestinal motility with functional problems remain pertinent problems. Nevertheless, a significant number of recipients have been able to stop TPN and resume a normal diet. Conclusions: Although recent results of intestinal transplantation are encouraging, long-term survival is less than with other solid organ transplants. However, continued improvements in immunosuppression and the diagnosis of rejection as well as better management of functional and infectious problems will certainly improve future results