Magnetic chemically peculiar stars

Chemically peculiar (CP) stars are main-sequence A and B stars with abnormally strong or weak lines for certain elements. They generally have magnetic fields and all observables tend to vary with the same period. Chemically peculiar stars provide a wealth of information; they are natural atomic and magnetic laboratories. After a brief historical overview, we discuss the general properties of the magnetic fields in CP stars, describe the oblique rotator model, explain the dependence of the magnetic field strength on the rotation, and concentrate at the end on HgMn stars.Comment: 9 pages, 4 figures, 2 tables, chapter in "Determination of Atmospheric Parameters of B-, A-, F- and G-Type Stars", Springer (2014), eds. E. Niemczura, B. Smalley, W. Pyc

Magnetic field topology and chemical spot distributions of the Ap star HD119419

Analysis of high-resolution spectropolarimetric observations of early-type magnetic stars is currently the most advanced method of obtaining detailed information on their surface magnetic field topologies and horizontal spot distributions. In this study we analyse a new set of high-quality four Stokes parameter observations of the magnetic Ap star HD119419 - a member of the 14 Myr old Lower Cen-Cru association - for the purpose of studying the surface field topology and mapping the chemical abundance spots. We made use of the circular and linear polarisation data collected for HD119419 with the HARPSpol instrument at the ESO 3.6-m telescope. These observations were analysed with a multi-line magnetic diagnostic technique and modelled in detail with a Magnetic Doppler imaging code. We present a new set of mean longitudinal magnetic field measurements and derive a revised stellar rotational period. We also redetermine the basic stellar atmospheric parameters. Our four Stokes parameter magnetic inversions reveal a moderately complex surface field topology with a mean field strength of 18 kG and a maximum local strength of 24 kG. A poloidal dipolar component dominates the magnetic energy spectrum of the surface field in HD119419. However, significant contributions of the higher-order spherical harmonic components are also present. We show that the dipole plus quadrupole part of the reconstructed field geometry is incapable of reproducing the observed amplitudes and shapes of the Stokes Q and U profiles. The chemical abundance distributions of Fe, Cr, Ti, and Nd, derived self-consistently with the magnetic field geometry, are characterised by large abundance gradients and a lack of clear correlation with the magnetic field structure. This full Stokes vector analysis of HD119419 extends the modern hot-star magnetic mapping investigations to an open cluster Ap star with a well-determined age.Comment: 15 pages, 11 figures; accepted for publication in A&

The Core-Wing Anomaly of Cool Ap Stars: Abnormal Balmer Profiles

Paper by Cowley et al. The Core-Wing Anomaly Etc. The profiles of H$\alpha$ in a number of cool Ap stars are anomalous. Broad wings, indicative of temperatures in the range 7000-8000K end abruptly in narrow cores. The widths of these cores are compatible with those of dwarfs with temperatures of 6000K or lower. This profile has been known for Przybylski's star, but it is seen in other cool Ap's. The H$\beta$ profile in several of these stars shows a similar core-wing anomaly (CWA). In Przybylski's star, the CWA is probably present at higher Balmer members. We are unable to account for these profiles within the context of LTE and normal dwarf atmospheres. We conclude that the atmospheres of these stars are not ``normal.'' This is contrary to a notion that has long been held.Comment: 4 Pages 5 Figures. Submitted to Astronomy and Astrophysics 4 Dec. 200

Haematology outreach clinics in the Free State and Northern Cape

Objective. Evaluation of haematology outreach clinics in the Northern Cape and Free State.Design. Retrospective analysis of records from March 1994 to February 1996.Setting. Central South Africa is sparsely populated. Consultants from Bloemfontein held outpatient clinics in hospitals (with laboratories) in Bethlehem, Kimberley and Kroonstad.SUbjects. 117 patients with suspected haematological disease.Main outcome measures. Input measures (population, number of clinics and costs), process measures (patient numbers, patients per clinic, new consultations per clinic, patients' domicile, how they were referred, types of diagnoses and number of patients with nonhaematologicaldisorders) and output measures (attrition, changes in attendance and savings).Main results. The 84 clinics that were held, with 636 consultations, did not cost the State anything. Only 6% of the 117 patients had no haematological problem. Sixtyeight per cent had chronic haematological neoplasms. In Kimberley most of the patients came from Kimberley Hospital, while most of the patients at the other clinics were referred via Bloemfontein. There was only a 10% attrition rate and only one-third of patients were referred to Bloemfontein. We saved paying patients an estimated R21 260 in transport costs, while saving the State R172 992 by seeing patients at secondary, instead of tertiary, hospitals.Conclusions. It is cheaper to send a doctor to an outreach clinic than to refer patients to a central facility, provided there is enough work for a doctor at the clinic. It costs the State much less for patients to be seen at a secondary than a tertiary hospital. Positive spin-offs include academic stimulation of doctors and laboratories in the periphery, with more appropriate referrals to teaching hospitals. Weaknesses include poor availability of expensive drugs at the clinics and lack of standardised records. By commuting to outreach clinics, specialists can greatly reduce health expenditure and spread it from tertiary to lower levels. At the same time more patients have access to their services

Annual fossil organic carbon delivery due to mechanical and chemical weathering of marly badlands areas

International audienceA key issue in the study of the carbon cycle is constraining the stocks and fluxes in and between C-reservoirs. Among these, the role and importance of fossil organic carbon (FOC) release by weathering of outcropping sedimentary rocks on continental surfaces is still debated and remains poorly constrained. Our work focuses on FOC fluxes due to chemical and mechanical weathering of marls in two experimental watersheds with typical badlands geomorphology (Draix watersheds, Laval and Moulin, Alpes de Haute Provence, France). Organic matter from bedrock, soil litter and riverine particles are characterized by Rock-Eval 6 pyrolysis. FOC fluxes due to mechanical weathering are then estimated by monitoring the annual particulate solid exports at the outlets of the watersheds (1985-2005 period). FOC fluxes from chemical weathering were calculated using Ca2+ concentrations in dissolved loads (year 2002) to assess the amount of FOC released by the dissolution of the carbonate matrix. Results show that FOC delivery is mainly driven by mechanical weathering, with a yield ranging from 30 to 59 t km-2 yr-1 in the Moulin (0.08 km2) and Laval (0.86 km2) catchments, respectively, (1985-2005 average). The release of FOC attributed to chemical weathering was 2.2 to 4.2 t km-2 for the year 2002. These high FOC fluxes from badlands are similar to those observed in tectonically active mountain catchments. At a regional scale, badland outcropping within the Durance watershed does not exceed 0.25% in area of the Rhone catchment, but could annually deliver 12 000 t yr-1 of FOC. This flux could correspond to 27% of the total particulate organic carbon (POC) load exported by the Rhone River to the Mediterranean Sea. At a global scale, our findings suggest that erosion of badlands may contribute significantly to the transfer of FOC from continental surfaces to depositional environments

Geospatial resources for supporting data standards, guidance and best practice in health informatics

<p>Abstract</p> <p>Background</p> <p>The 1980s marked the occasion when Geographical Information System (GIS) technology was broadly introduced into the geo-spatial community through the establishment of a strong GIS industry. This technology quickly disseminated across many countries, and has now become established as an important research, planning and commercial tool for a wider community that includes organisations in the public and private health sectors.</p> <p>The broad acceptance of GIS technology and the nature of its functionality have meant that numerous datasets have been created over the past three decades. Most of these datasets have been created independently, and without any structured documentation systems in place. However, search and retrieval systems can only work if there is a mechanism for datasets existence to be discovered and this is where proper metadata creation and management can greatly help.</p> <p>This situation must be addressed through support mechanisms such as Web-based portal technologies, metadata editor tools, automation, metadata standards and guidelines and collaborative efforts with relevant individuals and organisations. Engagement with data developers or administrators should also include a strategy of identifying the benefits associated with metadata creation and publication.</p> <p>Findings</p> <p>The establishment of numerous Spatial Data Infrastructures (SDIs), and other Internet resources, is a testament to the recognition of the importance of supporting good data management and sharing practices across the geographic information community. These resources extend to health informatics in support of research, public services and teaching and learning.</p> <p>This paper identifies many of these resources available to the UK academic health informatics community. It also reveals the reluctance of many spatial data creators across the wider UK academic community to use these resources to create and publish metadata, or deposit their data in repositories for sharing.</p> <p>The Go-Geo! service is introduced as an SDI developed to provide UK academia with the necessary resources to address the concerns surrounding metadata creation and data sharing. The Go-Geo! portal, Geodoc metadata editor tool, ShareGeo spatial data repository, and a range of other support resources, are described in detail.</p> <p>Conclusions</p> <p>This paper describes a variety of resources available for the health research and public health sector to use for managing and sharing their data. The Go-Geo! service is one resource which offers an SDI for the eclectic range of disciplines using GIS in UK academia, including health informatics.</p> <p>The benefits of data management and sharing are immense, and in these times of cost restraints, these resources can be seen as solutions to find cost savings which can be reinvested in more research.</p

Modeling subjective relevance in schizophrenia and its relation to aberrant salience

In schizophrenia, increased aberrant salience to irrelevant events and reduced learning of relevant information may relate to an underlying deficit in relevance detection. So far, subjective estimates of relevance have not been probed in schizophrenia patients. The mechanisms underlying belief formation about relevance and their translation into decisions are unclear. Using novel computational methods, we investigated relevance detection during implicit learning in 42 schizophrenia patients and 42 healthy individuals. Participants underwent functional magnetic resonance imaging while detecting the outcomes in a learning task. These were preceded by cues differing in color and shape, which were either relevant or irrelevant for outcome prediction. We provided a novel definition of relevance based on Bayesian precision and modeled reaction times as a function of relevance weighted unsigned prediction errors (UPE). For aberrant salience, we assessed responses to subjectively irrelevant cue manifestations. Participants learned the contingencies and slowed down their responses following unexpected events. Model selection revealed that individuals inferred the relevance of cue features and used it for behavioral adaption to the relevant cue feature. Relevance weighted UPEs correlated with dorsal anterior cingulate cortex activation and hippocampus deactivation. In patients, the aberrant salience bias to subjectively task-irrelevant information was increased and correlated with decreased striatal UPE activation and increased negative symptoms. This study shows that relevance estimates based on Bayesian precision can be inferred from observed behavior. This underscores the importance of relevance detection as an underlying mechanism for behavioral adaptation in complex environments and enhances the understanding of aberrant salience in schizophrenia