Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailAn XMM-Newton view of the young open cluster NGC 6231 - II. The OB star population
Sana, H.; Rauw, Grégor ULiege; Nazé, Yaël ULiege et al

in Monthly Notices of the Royal Astronomical Society (2006), 372(2), 661-678

In this second paper of the series, we pursue the analysis of the 180-ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature ... [more ▼]

In this second paper of the series, we pursue the analysis of the 180-ks XMM-Newton campaign towards the young open cluster NGC 6231 and we focus on its rich OB star population. We present a literature-based census of the OB stars in the field of view with more than one hundred objects, among which 30 per cent can be associated with an X-ray source. All the O-type stars are detected in the X-ray domain as soft and reasonably strong emitters. In the 0.5-10.0 keV band, their X-ray luminosities scale with their bolometric luminosities as log L-X - log L-bol = -6.912 +/- 0.153. Such a scaling law holds in the soft (0.5-1.0 keV) and intermediate (1.0-2.5 keV) bands but breaks down in the hard band. While the two colliding wind binaries in our sample clearly deviate from this scheme, the remaining O-type objects show a very limited dispersion (40 or 20 per cent according to whether 'cool' dwarfs are included or not), much smaller than that obtained from previous studies. At our detection threshold and with our sample, the sole identified mechanism that produces significant modulations in the O star X-ray emission is related to wind interaction. We thus propose that the intrinsic X-ray emission of non-peculiar O-type stars can be considered as constant for a given star. In addition, the level of X-ray emission is accurately related to the star luminosity or, equivalently, to its wind properties. Among B-type stars, the detection rate is only about 25 per cent in the subtype range B0-B4 and remains mostly uniform throughout the different subpopulations while it drops significantly at later subtypes. The associated X-ray spectra are harder than those of O-type stars. Our analysis points towards the detected emission being associated with a physical (in a multiple system) PMS companion. However, we still observe a correlation between the bolometric luminosity of the B stars and the measured X-ray luminosity. The best-fitting power law in the 0.5-10.0 keV band yields log L-X = 0.22(+/- 0.06) log L-bol + 22.8(+/- 2.4). [less ▲]

Detailed reference viewed: 31 (3 ULiège)
Full Text
Peer Reviewed
See detailAn XMM-Newton view of the young open cluster NGC 6231-III. Optically faint X-ray sources
Sana, H.; Rauw, Grégor ULiege; Sung, H. et al

in Monthly Notices of the Royal Astronomical Society (2007), 377(3), 945-956

We discuss the properties of the X-ray sources with faint optical counterparts in the very young open cluster NGC 6231. From their positions in the Hertzsprung-Russell diagram, we find that the bulk of ... [more ▼]

We discuss the properties of the X-ray sources with faint optical counterparts in the very young open cluster NGC 6231. From their positions in the Hertzsprung-Russell diagram, we find that the bulk of these objects probably consists of low-mass pre-main-sequence (PMS) stars with masses in the range 0.3-3.0 M-circle dot. The age distribution of these objects indicates that low-mass star formation in NGC 6231 started more than 10 Myr ago and culminated in a starburst-like event about 1-4 Myr ago when the bulk of the low-mass PMS stars as well as the massive cluster members formed. We find no evidence for a spatial age gradient that could point towards a sequential star formation process. Only a few X-ray sources have counterparts with a reddening exceeding the average value of the cluster or with infrared colours indicating the presence of a moderate near-IR excess. The X-ray spectra of the brightest PMS sources are best fitted by rather hard thermal plasma models and a significant fraction of these sources display flares in their light curve. The X-ray brightest flaring sources have decay times between 2 and 16 ks. The X-ray selected PMS stars in NGC 6231 have log L-X/L-bol values that increase strongly with decreasing bolometric luminosity and can reach a saturation level (log L-X/L-bol similar to -2.4) for non-flaring sources and even more extreme values during flares. [less ▲]

Detailed reference viewed: 26 (0 ULiège)
Full Text
Peer Reviewed
See detailXMM-Newton X-ray study of early type stars in the Carina OB1 association
Antokhin, I. I.; Rauw, Grégor ULiege; Vreux, Jean-Marie ULiege et al

in Astronomy and Astrophysics (2008), 477(2), 593-609

Aims. X-ray properties of the stellar population in the Carina OB I association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding ... [more ▼]

Aims. X-ray properties of the stellar population in the Carina OB I association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars. Methods. A timing and spectral analysis of five observations with XMM-Newton is performed using various statistical tests and thermal spectral models. Results. 235 point sources have been detected within the field of view. Several of these sources are probably pre-main sequence stars with characteristic short-term variability. Seven sources are possible background AGNs. Spectral analysis of twenty four sources of type OB and WR 25 was performed. We derived spectral parameters of the sources and their fluxes in three energy bands. Estimating the interstellar absorption for every source and the distance to the nebula, we derived X-ray luminosities of these stars and compared them to their bolometric luminosities. We discuss possible reasons for the fact that, on average, the observed X-ray properties of binary and single early type stars are not very different, and give several possible explanations. [less ▲]

Detailed reference viewed: 23 (0 ULiège)
Full Text
Peer Reviewed
See detailXPS analysis of chemical functions at the surface of Bacillus subtilis
Ahimou, François; Boonaert, Christophe; Adriaensen, Yasmine et al

in Journal of Colloid and Interface Science (2007), 309(1), 49-55

The surface chemical composition of nine strains of Bacillus subtilis was determined by X-ray photoelectron spectroscopy. Regressions between elemental concentrations and concentrations associated with ... [more ▼]

The surface chemical composition of nine strains of Bacillus subtilis was determined by X-ray photoelectron spectroscopy. Regressions between elemental concentrations and concentrations associated with different components of C1s, N1s, and O1s peaks provided a more precise validation of the procedure used for peak decomposition and allowed the assignment of the peak components to be completed or strengthened. The component of the O1s peak appearing around 531.2 eV was shown to contain a contribution of oxygen from phosphate groups (P=O, P–O−), the other contribution being due to oxygen involved in amide functions. The surface negative charge may be fully attributed to phosphate groups, despite the observation of two types of zeta potential vs pH curves. The strains exhibiting a sharp variation of the zeta potential (range of −35 to −55 mV) between pH 2 and 4.7 were characterized by a high phosphate surface concentration and by an excess (about 25%) of phosphate with respect to the sum of potassium, an exchangeable cation, and protonated nitrogen, attributed to protein or to alanine involved in teichoic acids. [less ▲]

Detailed reference viewed: 127 (31 ULiège)
Full Text
Peer Reviewed
See detailXPS analysis of the PC/PVDF interface modified by PMMA. Location of the PMMA at the interface
Moussaif, Noureddine; Pagnoulle, Christophe; Riga, Joseph et al

in Polymer (2000), 41(9), 3391-3394

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be ... [more ▼]

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be changed by the addition of polymethylmethacrylate (PMMA), which is miscible with PVDF and concentrates at the PVDF/PC interface. Location of PMMA at the PC/PVDF interface has been confirmed by XPS analysis, which shows that the interface enrichment in PMMA already takes place when only 10 wt% PMMA is premixed with PVDF. [less ▲]

Detailed reference viewed: 135 (12 ULiège)
See detailXPS and Raman study of spray-dried Na3V2(PO4)2F3/C as cathode material for sodium ion batteries
Eshraghi, Nicolas ULiege; Bodart, Jérôme ULiege; Mahmoud, Abdelfattah ULiege et al

Poster (2019, May 28)

Na3V2(PO4)2F3 (NVPF) has attracted much attention as cathode material for Na-ion batteries thanks to the inductive effects allowing for a high working potential combined with a high theoretical specific ... [more ▼]

Na3V2(PO4)2F3 (NVPF) has attracted much attention as cathode material for Na-ion batteries thanks to the inductive effects allowing for a high working potential combined with a high theoretical specific capacity due to the multiple oxidation states of vanadium [1-2]. One of the limitations of NVPF electrodes is their low intrinsic electronic conductivity; therefore, we have prepared composites of NVPF with conductive carbon sources to ensure higher electronic conductivity of the electrodes. NVPF and NVPF/carbon composite materials were prepared by spray-drying as in our previous work [2]. Spray drying is a cost-effective and up-scalable route to prepare homogeneous multi-component powders, thus making it a suitable method to incorporate carbon in the composite powder [4]. The influence of different carbon sources on structural and morphological properties of NVPF and NVPF/carbon composite was investigated by combining several characterization techniques (XRD, SEM and TEM). The chemical composition at the surface of the powders were studied using XPS. Raman spectroscopy was used to evaluate the quality in disordered carbon materials and its electronic conductivity [3] and compare the results with the results from EIS and cycling performance of different samples. References: [1] Shakoor et al., Chem. 22,2012, 20535. [2] Eshraghi et al., Electrochimica Acta, 228, 2017, 319. [3] Mahmoud et al., J Solid State Electrochem. 22, 2018,103. [4] Vertruyen et al., Materials 2018, 11, 1076. [less ▲]

Detailed reference viewed: 313 (19 ULiège)
Full Text
Peer Reviewed
See detailXPS data analysis via Wavelets and Fourier Transform.
Charles, Catherine ULiege; Rasson, Jean-Paul; Leclerc, Gervais

in Surface and Interface Analysis (2004), 36

Detailed reference viewed: 58 (7 ULiège)
Full Text
Peer Reviewed
See detailXPS structural characterization of Pd/SiO2 catalysts prepared by cogelation
Beketov, Gennadiy; Heinrichs, Benoît ULiege; Pirard, Jean-Paul ULiege et al

in Applied Surface Science (2013), 287

Nanostructured Pd/SiO2xerogel catalysts prepared via cogelation were characterized by X-ray photo-electron spectroscopy. The preparation route allowed highly porous silica particles to be formed alongwith ... [more ▼]

Nanostructured Pd/SiO2xerogel catalysts prepared via cogelation were characterized by X-ray photo-electron spectroscopy. The preparation route allowed highly porous silica particles to be formed alongwith embedded Pd nanocrystals. After heat-treating the catalysts in vacuum, Pd was found to be in themetallic state. To obtain information on the xerogel catalyst texture and, in particular, on the size of thesilica particles, a theoretical formalism was developed based on measuring the relative intensities of Pd 3ddoublet and the associated background tail due to inelastically scattered photoelectrons. The suggestedprocedure also involved the measurement of the background tails accompanying Si 2p and O 1s spectrallines as internal standards. Using the developed formalism, the size of the silica particles in the catalystsafter different treatments was evaluated and compared with TEM data. The results obtained indicate thatthe textural properties of the sol–gel catalysts start to develop already at the level of co-condensation ofalkoxides with the network-forming reagent. Calcination causes these properties to run to completion. [less ▲]

Detailed reference viewed: 55 (8 ULiège)
Full Text
Peer Reviewed
See detailXRD and NMR characterization of synthetic hectorites and the corresponding surfactant-exchanged clays
Gertsmans, André; Urbanczyk, Laetitia ULiege; Jérôme, Robert ULiege et al

in Clay Minerals (2008), 43

Detailed reference viewed: 90 (40 ULiège)
Full Text
Peer Reviewed
See detailXRF major and trace element determination in Fe-Ti oxide minerals
Duchesne, Jean-Clair ULiege; Bologne, Guy

in Geologica Belgica (2009), 12(3-4), 205-212

Detailed reference viewed: 46 (5 ULiège)
Peer Reviewed
See detailThe XSTAR atomic database
Mendoza, C.; Bautista, M.A.; Deprince, J. et al

Poster (2020, June)

Detailed reference viewed: 19 (1 ULiège)
Full Text
Peer Reviewed
See detailThe XSTAR atomic database
Mendoza, C.; Bautista, M.A.; Deprince, J. et al

in Atoms (2021), 9

Detailed reference viewed: 21 (1 ULiège)
Full Text
See detailXVI.C. - Le droit de propriété
Pâques, Michel ULiege; Vercheval, Cécile ULiege

in Bonbled, Nicolas; Verdussen, Marc (Eds.) Les droits constitutionnels en Belgique - Les enseignements jurisprudentiels de la Cour constitutionnelle, du Conseil d’état et de la Cour de cassation (2011)

Les droits fondamentaux reconnus par la Constitution belge sont une dimension toujours plus importante de la jurisprudence des plus hautes juridictions de notre pays. L’ouvrage collectif sur Les droits ... [more ▼]

Les droits fondamentaux reconnus par la Constitution belge sont une dimension toujours plus importante de la jurisprudence des plus hautes juridictions de notre pays. L’ouvrage collectif sur Les droits constitutionnels en Belgique entend éclairer les chercheurs, les enseignants, les étudiants et les praticiens sur la lecture qu’ont la Cour constitutionnelle, le Conseil d’Etat et la Cour de cassation, voire plus largement tous les cours et tribunaux de l’ordre judiciaire, des dispositions du Titre II de la Constitution et des autres dispositions qui y sont liées. L’ouvrage est divisé en deux parties principales. La première partie aborde les questions plus transversales (« Théorie générale des droits constitutionnels »), tandis que la seconde partie s’intéresse aux différents droits garantis par le texte constitutionnel (« Analyse particulière des droits constitutionnels »). Dans le respect d’une forme de subsidiarité, les auteurs se sont attachés à mettre en valeur les spécificités du catalogue belge des droits fondamentaux, du contentieux qu’il suscite, et des interprétations qui en sont donné. L’objectif consiste donc à apporter une contribution substantielle à l’édification du « droit belge des droits de l’Homme ». Le matériau principal est la jurisprudence nationale, passée et présente, même si, selon les droits concernés, certaines décisions des juges internationaux et européens peuvent apparaître incontournables, par le lien étroit qu’elles entretiennent avec la jurisprudence belge. [less ▲]

Detailed reference viewed: 126 (14 ULiège)
Full Text
See detailXVII Encuentro de Geógrafos de América Latina
Chiriboga Gavidia, Washington Gonzalo ULiege

Scientific conference (2019, April 17)

The Intergovernmental Panel on Climate Change indicates that the sources of anthropogenic CO2 emitted into the atmosphere are: fossil combustion 9.1 ± 0.5 Pg C y-1 and deforestation 0.9 ± 0.7 Pg C y-1 ... [more ▼]

The Intergovernmental Panel on Climate Change indicates that the sources of anthropogenic CO2 emitted into the atmosphere are: fossil combustion 9.1 ± 0.5 Pg C y-1 and deforestation 0.9 ± 0.7 Pg C y-1. These emissions are deposited in two sinks: the atmosphere 5.0 ± 0.2 Pg C y-1 and the ocean of 2.4 ± 0.5 Pg C y-1. Therefore, the 2.6 ± 1.0 Pg C y-1 remnant must be fixed in the terrestrial biosphere, including inland waters (rivers, lakes, floodplains, etc.). In tropical latitudes, inland waters constitute an essential source of gases. Greenhouse effect that, later, evacuate into the atmosphere; For this reason, the research focuses on the Spatio-temporal quantification of the flows of these gases, with particular attention to the highest areas of two principal tributaries of the Amazon River, such as the Coca-Napo and the Pastaza. Currently available georeferencing and geostatistics tools allow quantification to be characterized vertically and horizontally. The vertical quantification indicates the fluxes of CO2, CH4, and N2O towards the atmosphere. In contrast, the horizontal quantification allows studying the drag of organic and inorganic carbon downstream, by the current of rivers. The first results of the field missions allow us to georeference 30 sampling stations distributed in the watersheds of the Coca and Napo rivers, which cover a distance of 225 and 164 km, respectively. These stations were selected based on the presence of tributary rivers and an altitude gradient of 250 m.a.s.l., both criteria were met with the use of a geographic information system. The statistical treatment of the data indicates that CO2 fixed in the high areas or mountains is discharged in the foothills, below 500 m.a.s.l., mainly at the junction of the Coca and Napo rivers. Furthermore, it was found that the concentration gradient between water and air is always positive, which indicates that the river is continuously emitting greenhouse gases into the atmosphere. The quantification of carbon and its subsequent discrimination, based on its organic or inorganic origin, will allow a better understanding of the real impact of anthropogenic processes on global warming. [less ▲]

Detailed reference viewed: 56 (3 ULiège)
Peer Reviewed
See detailLe XVIIIe siècle culinaire : vers l’art et la science du goût
Von Hoffmann, Viktoria ULiege

Conference (2011, October 01)

Detailed reference viewed: 19 (2 ULiège)
Full Text
See detailXX European Congress of Herpetology, Milan, 2-6 September 2019. Program and Abstracts
Ficetola, Gentile Francesco; Sacchi, Roberto; Scali, Stefano et al

Book published by S.E.H. (2019)

Detailed reference viewed: 57 (4 ULiège)
Full Text
Peer Reviewed
See detailXX. CoRoT-20b: A very high density, high eccentricity transiting giant planet
Deleuil, M.; Bonomo, A. S.; Ferraz-Mello, S. et al

in Astronomy and Astrophysics (2012), 538

We report the discovery by the CoRoT space mission of a new giant planet, CoRoT-20b. The planet has a mass of 4.24 +/- 0.23 MJ and a radius of 0.84 +/- 0.04 RJ. With a mean density of 8.87 +/- 1.10 g/cm^3 ... [more ▼]

We report the discovery by the CoRoT space mission of a new giant planet, CoRoT-20b. The planet has a mass of 4.24 +/- 0.23 MJ and a radius of 0.84 +/- 0.04 RJ. With a mean density of 8.87 +/- 1.10 g/cm^3, it is among the most compact planets known so far. Evolution models for the planet suggest a mass of heavy elements of the order of 800 ME if embedded in a central core, requiring a revision either of the planet formation models or of planet evolution and structure models. We note however that smaller amounts of heavy elements are expected from more realistic models in which they are mixed throughout the envelope. The planet orbits a G-type star with an orbital period of 9.24 days and an eccentricity of 0.56. The star's projected rotational velocity is vsini = 4.5 +/- 1.0 km/s, corresponding to a spin period of 11.5 +/- 3.1 days if its axis of rotation is perpendicular to the orbital plane. In the framework of Darwinian theories and neglecting stellar magnetic breaking, we calculate the tidal evolution of the system and show that CoRoT-20b is presently one of the very few Darwin-stable planets that is evolving towards a triple synchronous state with equality of the orbital, planetary and stellar spin periods. [less ▲]

Detailed reference viewed: 26 (5 ULiège)
Full Text
Peer Reviewed
See detailThe XXL Survey XIV. AAOmega Redshifts for the Southern XXL Field
Lidman, C.; Ardila, F.; Owers, M. et al

in Publications of the Astronomical Society of Australia (2016), 33

We present a catalogue containing the redshifts of 3 660 X-ray selected targets in the XXL southern field. The redshifts were obtained with the AAOmega spectrograph and 2dF fibre positioner on the Anglo ... [more ▼]

We present a catalogue containing the redshifts of 3 660 X-ray selected targets in the XXL southern field. The redshifts were obtained with the AAOmega spectrograph and 2dF fibre positioner on the Anglo-Australian Telescope. The catalogue contains 1 515 broad line AGN, 528 stars, and redshifts for 41 out of the 49 brightest X-ray selected clusters in the XXL southern field. Copyright © Astronomical Society of Australia 2016. [less ▲]

Detailed reference viewed: 25 (1 ULiège)