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

How the Belgian wind farm business made us discover the challenging environment of marine sand dunes

During the last decade, it has become clear that sand dunes are important features in the Belgian wind farm concession area. Because they influence not only the design seabed levels, but also the hydrodynamic forcings and installation methods for both cable and foundations, the study of the seabed morphodynamics is essential for all wind farm projects. This paper starts with an overview of the geographic and morphological setting of the Belgian wind farm concession areas and presents an overview of the key features of the bedforms in the different concessions. Next the importance and impact of the sand dunes during the design and development of these wind farms is illustrated by exploring the different types of studies and investigations which have been performed in relation to seabed & morphology, the hydrodynamic loadings, the installation methods and the environmental impact assessments

Constraining the fundamental parameters of the O-type binary CPD-41degr7733

Using a set of high-resolution spectra, we studied the physical and orbital properties of the O-type binary CPD-41 7733, located in the core of \ngc. We report the unambiguous detection of the secondary spectral signature and we derive the first SB2 orbital solution of the system. The period is 5.6815 +/- 0.0015 d and the orbit has no significant eccentricity. CPD-41 7733 probably consists of stars of spectral types O8.5 and B3. As for other objects in the cluster, we observe discrepant luminosity classifications while using spectroscopic or brightness criteria. Still, the present analysis suggests that both components display physical parameters close to those of typical O8.5 and B3 dwarfs. We also analyze the X-ray light curves and spectra obtained during six 30 ks XMM-Newton pointings spread over the 5.7 d period. We find no significant variability between the different pointings, nor within the individual observations. The CPD-41 7733 X-ray spectrum is well reproduced by a three-temperature thermal mekal model with temperatures of 0.3, 0.8 and 2.4 keV. No X-ray overluminosity, resulting e.g. from a possible wind interaction, is observed. The emission of CPD-41 7733 is thus very representative of typical O-type star X-ray emission.Comment: Accepted by ApJ, 15 pages, 9 figure

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

CO2 Reduction Measures in the Aviation Industry: Current Measures and Outlook

This article gives a holistic overview of the current CO2 reduction measures and analyses the effectiveness of measures that are feasible for implementation in the future. To achieve the objectives of the Paris Agreement, the aviation industry needs to implement reduction measures because of its forecasted growth and contribution to global warming. The focus is set on CO2 reduction measures, categorized in technology, operations, infrastructure/air traffic management (ATM), and market-based measures. The most promising long-term technologies to reduce CO2 emissions are hydrogen-powered aircrafts and sustainable aviation fuels (SAF). In terms of operations, CO2 emissions can be reduced through weight savings, either from fuel or payload. For every additional ton on board of an aircraft, an extra 3%–25% of fuel is necessary, depending on the route distance. From an infrastructure/ATM perspective, the goal is to decrease flight times and avoid holdings because every kg of fuel burned produces 3.16 kg of CO2 emissions. Market-based measures have a low impact as a reduction measure, but revenues may be used to accelerate the research and development of more promising reduction measures. The implementation of just one reduction measure is not reasonable. A global approach with reasonable incentives to support CO2 reduction measures is preferable

Zeevraag: Waarom staan windturbines op zee soms stil?

Windturbines op zee staan zelden stil, toch denken nogal wat mensen dat dit vaak het geval is. Wat is de verklaring hiervoor? Laten we eerst even naar de cijfers kijken

Pavlovian conditioning-induced hallucinations result from overweighting of perceptual priors

Some people hear voices that others do not, but only some of those people seek treatment. Using a Pavlovian learning task, we induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, we identified processes that differentiated voice-hearers from non-voice-hearers and treatment-seekers from non-treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations. These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without