Exploring the origin of magnetic fields in massive stars: II. New magnetic field measurements in cluster and field stars

in Astronomy and Astrophysics (2013), 551

Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. To ... [more ▼]

Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, roughly one third of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association. Spectropolarimetric observations were obtained during four different nights using the low-resolution spectropolarimetric mode of FORS2 (FOcal Reducer low dispersion Spectrograph) mounted on the 8-m Antu telescope of the VLT. Furthermore, we present a number of follow-up observations carried out with the high-resolution spectropolarimeters SOFIN mounted at the Nordic Optical Telescope (NOT) and HARPS mounted at the ESO 3.6m between 2008 and 2011. To assess the membership in open clusters and associations, we used astrometric catalogues with the highest quality kinematic and photometric data currently available. The presence of a magnetic field is confirmed in nine stars previously observed with FORS1/2: HD36879, HD47839, CPD-282561, CPD-472963, HD93843, HD148937, HD149757, HD328856, and HD164794. New magnetic field detections at a significance level of at least 3sigma were achieved in five stars: HD92206c, HD93521, HD93632, CPD-468221, and HD157857. Among the stars with a detected magnetic field, five stars belong to open clusters with high membership probability. According to previous kinematic studies, five magnetic O-type stars in our sample are candidate runaway stars. [less ▲]

Kein Ey gleicht dem anderen. Rezension zu "Im Bergwerk der Sprache"

in ReLü: Rezensionszeitschrift zur Literaturübersetzung (2013)

Opérations arithmétiques et symbolisations variées. Partir des démarches informelles des élèves pour donner du sens aux apprentissages

in Education et Formation (2013), e-298(01), 23-38

Tout en s’appuyant sur certains apports de la psychologie cognitive, le présent article se situe dans la lignée des courants socioculturels qui défendent l’idée d’une co-construction des concepts et des ... [more ▼]

Tout en s’appuyant sur certains apports de la psychologie cognitive, le présent article se situe dans la lignée des courants socioculturels qui défendent l’idée d’une co-construction des concepts et des symboles. Il s’intéresse à différents types de symbolisations informelles (comme l’utilisation de matériel manipulable, des doigts ou de représentations dessinées) ou plus formelles (comme le diagramme de Venn, le graphe fléché ou les calculs). Les résultats de deux études empiriques menées en 1ère primaire en Communauté française de Belgique montrent que l’utilisation de matériel manipulable permet aux élèves de résoudre une variété de problèmes mais qu’ils éprouvent d’importantes difficultés à utiliser un symbolisme mathématique conventionnel et à produire un calcul en lien avec les démarches de résolution développées ; l’utilisation de ces symbolisations « mal comprises » pouvant conduire au développement de stratégies superficielles de résolution de problèmes. Par ailleurs, une étude exploratoire indique qu’il est possible de travailler au départ des symbolisations informelles produites par les élèves pour les aider à développer une meilleure compréhension des concepts impliqués et pour tendre progressivement vers des symbolisations mathématiques plus conventionnelles qu’ils devraient ainsi mieux intégrer. [less ▲]

Health Technology Assessment in Osteoporosis.

in Calcified Tissue International (2013)

We review the various aspects of health technology assessment in osteoporosis, including epidemiology and burden of disease, and assessment of the cost-effectiveness of recent advances in the treatment of ... [more ▼]

We review the various aspects of health technology assessment in osteoporosis, including epidemiology and burden of disease, and assessment of the cost-effectiveness of recent advances in the treatment of osteoporosis and the prevention of fracture, in the context of the allocation of health-care resources by decision makers in osteoporosis. This article was prepared on the basis of a symposium held by the Belgian Bone Club and the discussions surrounding that meeting and is based on a review and critical appraisal of the literature. Epidemiological studies confirm the immense burden of osteoporotic fractures for patients and society, with lifetime risks of any fracture of the hip, spine, and forearm of around 40 % for women and 13 % for men. The economic impact is also large; for example, Europe's six largest countries spent <euro>31 billion on osteoporotic fractures in 2010. Moreover, the burden is expected to increase in the future with demographic changes and increasing life expectancy. Recent advances in the management of osteoporosis include novel treatments, better fracture-risk assessment notably via fracture risk algorithms, and improved adherence to medication. Economic evaluation can inform decision makers in health care on the cost-effectiveness of the various interventions. Cost-effectiveness analyses suggest that the recent advances in the prevention and treatment of osteoporosis may constitute an efficient basis for the allocation of scarce health-care resources. In summary, health technology assessment is increasingly used in the field of osteoporosis and could be very useful to help decision makers efficiently allocate health-care resources. [less ▲]

Evaluation of a Model-Based Hemodynamic Monitoring Method in a Porcine Study of Septic Shock

in Computational and Mathematical Methods in Medicine (2013)

La pile à combustible: du marché de niche au marché de masse

Conference given outside the academic context (2013)

New pro-death function of NIK downstream of TNFR1

Doctoral thesis (2013)

Controlled and automatic memory retrieval in Alzheimer's disease

Conference (2013, February 28)

5. Les régulateurs de croissance

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc - Céréales (2013, February 27)

Effect of uncertainty in surface mass balance–elevation feedback on projections of the future sea level contribution of the Greenland ice sheet – Part 1: Parameterisation

in Cryosphere Discussions (The) (2013), 7

We present a new parameterisation that relates surface mass balance (SMB: the sum of surface accumulation and surface ablation) to changes in surface elevation of the Greenland ice sheet (GrIS) for the ... [more ▼]

We present a new parameterisation that relates surface mass balance (SMB: the sum of surface accumulation and surface ablation) to changes in surface elevation of the Greenland ice sheet (GrIS) for the MAR regional climate model. The motivation is to dynamically adjust SMB as the GrIS evolves, allowing us to force ice sheet models with SMB simulated by MAR while incorporating the SMB–elevation feedback, without the substantial technical challenges of coupling the two models. This also allows us to assess the effect of elevation feedback uncertainty on the GrIS contribution to sea level, using multiple global climate and ice sheet models, without the need for additional, expensive MAR simulations. We estimate this relationship separately below and above the equilibrium line altitude (ELA, separating negative and positive SMB) and for regions north and south of 77° N, from a set of MAR simulations in which we alter the ice sheet surface elevation. These give four "SMB lapse rates", gradients that relate SMB changes to elevation changes. We assess uncertainties within a Bayesian framework, estimating probability distributions for each gradient from which we present best estimates and credibility intervals (CIs) that bound 95% of the probability. Below the ELA our gradient estimates are mostly positive, because SMB usually increases with elevation: 0.54 (95% CI: −0.22 to 1.34) kg m−3 a−1 for the north, and 1.89 (1.03 to 2.61) kg m−3 a−1 for the south. Above the ELA the gradients are much smaller: 0.09 (−0.03 to 0.22) kg m−3 a−1 in the north, and 0.06 (−0.07 to 0.56) kg m−3 a−1 in the south, because SMB can either increase or decrease in response to increased elevation. Our statistically based approach allows us to make probabilistic assessments for the effect of elevation feedback uncertainty on sea level projections. In a companion paper we use the best estimates and upper and lower CI bounds in five ice sheet models, and the full probability distributions in another, to adjust simulated SMB from MAR forced by two global climate models for the SRES A1B scenario (Edwards et al., 2013). [less ▲]