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See detailPolarization properties of a sample of broad absorption line and gravitationally lensed quasars
Hutsemekers, Damien ULg; Lamy, H.; Remy, M.

in Astronomy and Astrophysics (1998), 340

New broad-band linear polarization measurements have been obtained for a sample of 42 optically selected QSOs including 29 broad absorption line (BAL) QSOs. The polarization properties of different sub ... [more ▼]

New broad-band linear polarization measurements have been obtained for a sample of 42 optically selected QSOs including 29 broad absorption line (BAL) QSOs. The polarization properties of different sub-classes have been compared, and possible correlations with various spectral indices searched for. The main results of our study are: (1) Nearly all highly polarized QSOs of our sample belong to the sub-class of BAL QSOs with low-ionization absorption features (LIBAL QSOs). (2) The range of polarization is significantly larger for LIBAL QSOs than for high-ionization (HI) BAL QSOs and non-BAL QSOs. (3) There is some indication that HIBAL QSOs as a class may be more polarized than non-BAL QSOs and therefore intermediate between LIBAL and non-BAL QSOs, but the statistics are not compelling from the sample surveyed thus far. (4) For LIBAL QSOs, the continuum polarization appears significantly correlated with the line profile detachment index, in the sense that LIBAL QSOs with P Cygni-type profiles are more polarized. No correlation was found with the strength of the low- or the high-ionization absorption features, nor with the strength or the width of the emission lines. These results are consistent with a scenario in which LIBAL QSOs constitute a different class of radio-quiet QSOs with more absorbing material and more dust. Higher maximum polarization can therefore be reached, while the actually measured polarization depends on the geometry and orientation of the system as do the line profiles. The observed correlation is interpreted within the framework of recent ``wind-from-disk'' models. Tables~2 and 3 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html}\fnmsep\thanks{Based on observations collected at the European Southern Observatory (ESO, La Silla) [less ▲]

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See detailPolarization properties of broad absorption line QSOs: New statistical clues
Lamy, H.; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (2004), 427

We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations ... [more ▼]

We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations between ten optical indices and the polarization degree p[SUB]0[/SUB] are systematically searched for. We find six significant non-trivial correlations. In order to identify the most important correlations, we perform a principal component analysis with a sample of 30 BAL QSOs and eight quantities (including p[SUB]0[/SUB]). Most of the variance (Ë 57%) in the data is contained in two principal components called PC1 and PC2. PC1 is mainly dominated by the correlation between the balnicity index BI and the strength of the Fe II emission; it may be driven by the accretion rate of matter onto the central compact object. The variance in PC2 is essentially due to the anti-correlation between p[SUB]0[/SUB] and the detachment index DI, indicating that BAL QSOs with P Cygni profiles (DIâ ª) are usually more polarized than those objects with C IV absorption troughs well detached from the corresponding emission lines (DIâ «). We show that PC2 may be related to the orientation of the BAL QSOs with respect to the line of sight. We also present new spectropolarimetric observations of six BAL QSOs. By adding spectropolarimetric data from the literature, we build a sample of 21 BAL QSOs for which we define four spectropolarimetric indices describing the polarization properties of the absorption and emission lines. We find that the polarization of the C III]] emission line is systematically higher than the polarization of the C IV emission line, and that the highest polarization in the troughs is correlated to the balnicity index. Another important result emerging from the statistical tests performed on this spectropolarimetric sample is a possible anti-correlation between the detachment index and a quantity SI which measures the ratio of the depths of the C IV absorption in the polarized flux and in the total flux. This correlation indicates that in BAL QSOs with P cygni profiles, the BAL troughs in the polarized flux are nearly as deep as in the total flux while, in BAL QSOs with detached absorptions, the BAL troughs in the polarized flux are much weaker than in the total flux. We show that our main results may be explained in the framework of a ``two-component'' wind model which is a natural extension of the classical wind-from-disk models. In this model, the broad absorption occurs in a dense equatorial wind emerging from the accretion disk, while scattering and polarization mainly take place in a polar region. The orientation relative to the observer drives the correlations p[SUB]0[/SUB] - DI and DI - SI. While most of our observations can be explained within this framework, there are also several indications that other polarization mechanisms, and more particularly resonance scattering, may also be at work. Based on observations collected at the European Southern Observatory (ESO, La Silla). Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http: / / cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/427/107 [less ▲]

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See detailThe Polarization Properties of Broad Absorption Line QSOs: Observational Results
Hutsemekers, Damien ULg; Lamy, H.

in Mass Outflow in Active Galactic Nuclei: New Perspectives. ASPC 255 (2002)

Correlations between BAL QSO intrinsic properties and polarization have been searched for. Some results are summarized here, providing possible constraints on BAL outflow models.

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See detailPolarization radiation of vortex electrons with large orbital angular momentum
Ivanov, Igor ULg; Karlovets, Dmitry

in Physical Review. A (2013), 88(4), 043840

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital ... [more ▼]

Vortex electrons—freely propagating electrons whose wave functions have helical wave fronts—could become a novel tool in the physics of electromagnetic radiation. They carry a nonzero intrinsic orbital angular momentum (OAM) ℓ with respect to the propagation axis and, for ℓ≫1, a large OAM-induced magnetic moment μ≈ℓμB (μB is the Bohr magneton), which influences the radiation of electromagnetic waves. Here, we consider in detail the OAM-induced effects caused by such electrons in two forms of polarization radiation, namely, in Cherenkov radiation and transition radiation. Thanks to the large ℓ, we can neglect quantum or spin-induced effects, which are of the order of ℏω/Ee≪1, but retain the magnetic moment contribution ℓℏω/Ee≲1, which makes the quasiclassical approach to polarization radiation applicable. We discuss the magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on the kinematical parameters and the medium permittivity. In particular, it is shown that this contribution can, in principle, be detected in azimuthally nonsymmetrical problems, for example when vortex electrons obliquely cross a metallic screen (transition radiation) or move near it (diffraction radiation). We predict a left-right angular asymmetry of the transition radiation (in the plane where the charge radiation distributions would stay symmetric), which appears due to an effective interference between the charge radiation field and the magnetic moment contribution. Numerical values of this asymmetry for vortex electrons with Ee=300 keV and ℓ=100–1000 are 0.1%–1%, and we argue that this effect could be detected with existing technology. The finite conductivity of the target and frequency dispersion play crucial roles in these predictions. [less ▲]

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See detailPolarization vortices in germanium telluride nanoplatelets: A theoretical study
Durgun, Engin ULg; Ghosez, Philippe ULg; Shaltaf, R. et al

in Physical Review Letters (2009), 103

Using first-principles calculations based on density functional theory, we study the properties of germanium telluride crystalline nanoplatelets and nanoparticles. Above a diameter of 2.7 nm, we predict ... [more ▼]

Using first-principles calculations based on density functional theory, we study the properties of germanium telluride crystalline nanoplatelets and nanoparticles. Above a diameter of 2.7 nm, we predict the appearance of polarization vortices giving rise to an unusual ferrotoroidic ground state with a spontaneous and reversible toroidal moment of polarization. We highlight the crucial role of inhomogeneous strain in stabilizing polarization vortices. Combined with the phase-change properties of germanium telluride, the ferrotoroidic properties could be of practical interest for ternary logic applications. [less ▲]

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See detailPolarization-corrected electrostatic potentials of aromatic compounds
Dehareng, Dominique ULg; Dive, Georges ULg; Ghuysen, Jean-Marie ULg

in Journal of the American Chemical Society (1993), 115(15), 6877-6882

The electrostatic potentials (EPS) corrected for polarization (TPS) of the aromatic compounds benzene, aniline, chlorobenzene, nitrobenzene, phenol, benzamide, and N-phenylacetamide have been calculated ... [more ▼]

The electrostatic potentials (EPS) corrected for polarization (TPS) of the aromatic compounds benzene, aniline, chlorobenzene, nitrobenzene, phenol, benzamide, and N-phenylacetamide have been calculated at the ab initio SCF level within three basis sets: 6-31G**, MINI-1, and STO-3G. For chlorobenzene in its MINI-1-optimized geometry, the calculation was also performed within MINI-1**. By reference to 6-31G**, the MINI-1-computed EP is much more satisfactory than the STO-3G-computed EP, whereas the MINI-I and STO-3G basis sets give very similar total potentials corrected for polarization (TPs). The MINI-1** basis set appears to be miscalibrated for computing EPs. It provides qualitative results that differ from those obtained with the 6-31G** basis set. The EP has a negative well above the middle of the benzene ring, while the TP exhibits a negative crown just above the benzene carbon atoms, where electrophilic attack takes place. The TP calculated for the interaction of nitrobenzene with a hydride ion instead of a proton allowed analyzation of the effects of polarization on the positive EP above the N-C bond. [less ▲]

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See detailUn pôle d'excellence wallon en santé articulaire.
Henrotin, Yves ULg

Article for general public (2012)

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See detailPole, albedo and shape of the minor planets 624 Hektor and 43 Ariadne: Two tests for comparing four different pole determination methods
Detal, Alain ULg; Hainaut, O.; Pospieszalska-Surdej, A. et al

in Astronomy and Astrophysics (1994), 281

Asteroids 624 Hektor and 43 Ariadne have been observed photometrically at the European Southern Observatory (La Silla, Chile) in order to determine their pole orientation. The lightcurves (1984 and 1991 ... [more ▼]

Asteroids 624 Hektor and 43 Ariadne have been observed photometrically at the European Southern Observatory (La Silla, Chile) in order to determine their pole orientation. The lightcurves (1984 and 1991 oppositions for Hektor, and 1985 for Ariadne) are presented. Some of the traditional pole determination methods have been improved, and completely original ones have been developed. They are described and applied to the newly recorded and previously published light curves. The results are commented and compared with previous ones. In addition to the pole orientation, we also derive some information on the shape or the albedo distribtuion of the objects. With the aim of optimizing future observations of these asteroids, we present some graphs showing the best longitudes where they should be measured. Finally, we suggest some improvements in the pole determination and modeling methods based upon photometric data. [less ▲]

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See detailPolemik und Ostalgie. Zu Günter Grass’ Tagebuch 1990 mit Seitenblick auf Peter Rühmkorfs TABU
Pontzen, Alexandra ULg

in Gegenwartsliteratur : ein germanistisches Jahrbuch = a German studies yearbook (2011), 10

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See detailPolémique autour de l'huile de palme: Instantanés d'un secteur en crise
Delacharlerie, Sophie ULg; Poncelet, Céline ULg; Chèné, Christine et al

in Industries Alimentaires et Agricoles (2012), 2012(Mai-Juin), 42-47

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See detailPolémique sur le port du voile à l’école en Belgique : le voile comme argument "épiphénoménal"?
Piet, Grégory ULg

in Grandjean, Geoffrey; Piet, Grégory (Eds.) Polémiques à l'école. Perspectives internationales sur le lien social (2012)

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See detailPolémiques à l'école. Perspectives internationales sur le lien social
Grandjean, Geoffrey ULg; Piet, Grégory ULg

Book published by Armand Colin - Armand Colin Éditeur • 21, rue du Montparnasse • 75006 Paris (2012)

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See detailLes polémiques autour de la littérature jeunesse, ou la quête sans cesse rejouée de la légitimité
Barnabé, Fanny ULg

in COnTEXTES : Revue de Sociologie de la Littérature (2012), (10),

Cet article analyse les enjeux dissimulés derrière une polémique qui a débuté suite à un article de François Busnel, publié le 24 novembre 2010 dans l’Express-Lire, dans lequel ce dernier dénigre la ... [more ▼]

Cet article analyse les enjeux dissimulés derrière une polémique qui a débuté suite à un article de François Busnel, publié le 24 novembre 2010 dans l’Express-Lire, dans lequel ce dernier dénigre la littérature jeunesse et l’accuse de n’être qu’un "coup marketing". Cette publication a déclenché de nombreuses réactions chez les représentants de ce secteur. L'analyse proposée ici tâche de rendre compte, en confrontant les deux types de prises de parole, de l’impact que peut avoir l’objet d'une polémique (la littérature jeunesse, dans ce cas-ci) sur le déroulement de celle-ci. [less ▲]

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See detailLes pôles de compétitivités : une réponse pragmatique permettant d’intégrer le concept d’Open Innovation dans les relations entre universités et entreprises
Morant, Michel ULg

Conference (2009, March 02)

The paper describe how the Walloon Region applies the open innovation concept for supporting innovative actors, in accordance with the open innovation model.

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See detailPôles périphériques et hiérarchies intra-urbaines en Belgique : vers une nouvelle mobilité commerciale
Halleux, Jean-Marie ULg

in Metton, A.; Desse, R.-P. (Eds.) Les nouveaux acteurs du commerce et leurs stratégies spatiales. Actes du colloque européen (Brest 1995) (1997)

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See detailPoleward front of upwelling filaments generates subsurface anticyclonic eddies (FEDDY): a CAIBEX Project contribution
Sangrà, Pablo; Arístegui, Javier; Troupin, Charles ULg et al

Poster (2010, February 25)

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See detailPolice administrative et sanction administrative
Pâques, Michel ULg

in Andersen, Robert; Déom, D.; Renders, D. (Eds.) Les sanctions administratives (2007)

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See detailPolice de proximité. Un modèle belge entre questions et pratiques
Seron, Vincent ULg; Smeets, Sybille; Smits, Marcel et al

Book published by Politeia (2004)

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See detailPolice et immigrés
Gailly, Philippe; Gavray, Claire ULg; Robert, Jocelyne ULg

Report (1991)

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