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See detailPréface
Marganne, Marie-Hélène ULg

in de Haro Sanchez, Magali (Ed.) Ecrire la magie dans l'antiquité. Actes du colloque international (Liège, 13-15 octobre 2011) (2015)

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See detailBaccio Bandinelli théoricien. Réflexions sur le "Libro del Disegno"
Marique, Charlotte ULg

Conference (2015, October 02)

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See detailSpectral Variations of Of?p Oblique Magnetic Rotator Candidates in the Magellanic Clouds
Walborn, Nolan R.; Morrell, Nidia I.; Nazé, Yaël ULg et al

in Astronomical Journal (The) (2015), 150

Optical spectroscopic monitoring has been conducted of two O stars in the SMC and one in the LMC, the spectral characteristics of which place them in the Of?p category, which has been established in the ... [more ▼]

Optical spectroscopic monitoring has been conducted of two O stars in the SMC and one in the LMC, the spectral characteristics of which place them in the Of?p category, which has been established in the Galaxy to consist of oblique magnetic rotators. All of these Magellanic stars show systematic spectral variations typical of the Of?p class, further strengthening their magnetic candidacy to the point of virtual certainty. The spectral variations are related to photometric variations derived from Optical Gravitational Lensing Experiment data by Nazé et al. in a parallel study, which yields rotational periods for two of them. Now circular spectropolarimetry is required to measure their fields, and ultraviolet spectroscopy to further characterize their low-metallicity, magnetically confined winds, in support of hydrodynamical analyses. [less ▲]

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See detailLe droit de vote à distance: Emergence d'un objet de recherche et apport au champ de la sociologie électorale
Lafleur, Jean-Michel ULg

Conference (2015, October 01)

Dans cet article, nous présentons tout d’abord l’émergence du droit de vote à distance comme objet de recherche dans le champ la théorie politique et des études migratoires. Ces travaux caractérisés par ... [more ▼]

Dans cet article, nous présentons tout d’abord l’émergence du droit de vote à distance comme objet de recherche dans le champ la théorie politique et des études migratoires. Ces travaux caractérisés par leur dimension exploratoire, nous permettent toutefois de définir le droit de vote à distance et d’identifier les caractéristiques essentielles qui le différencie aujourd’hui des pratiques antérieures. Nous présentons ensuite les travaux sur la diffusion de la norme qui depuis moins d’une décennie ont constitué le principal angle d’entrée de la science politique sur le droit de vote à distance. Dans la troisième et dernière partie de l’article, nous défendons enfin l’intérêt d’une approche transnationale des questions électorales dans les études électorales. Cette approche, comme nous le défendons, permet d’éclairer non seulement le comportement des expatriés mais plus largement la transformation des pratiques électorales ici et là-bas. [less ▲]

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See detailBuilding a bridge between Liege and Asturias : the case of zinc
Peters, Arnaud ULg

Conference (2015, October 01)

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See detailCoherence and many-body effects in the transport of Bose–Einstein condensates
Dujardin, Julien ULg

Doctoral thesis (2015)

This thesis presents investigations on the interplay of coherence and many-body effects in the quasi one-dimensional transport of Bose-Einstein condensates (BEC) through scattering potentials. Such ... [more ▼]

This thesis presents investigations on the interplay of coherence and many-body effects in the quasi one-dimensional transport of Bose-Einstein condensates (BEC) through scattering potentials. Such configurations can be realized with guided atom lasers that provide a coherent atomic beam. An exact theoretical description of the dynamics is out of reach due to the presence atom-atom interactions. Different levels of approximations are nevertheless possible with their strengths and weaknesses. The mean-field approximation, where the dynamics of the BEC is governed by the Gross-Pitaevskii equation, is most commonly used in the field of ultracold atoms. In this thesis the truncated Wigner method is used to go beyond the standard Gross-Pitaevskii description. This method is adapted in order to study the scattering of Bose-Einstein condensates in one-dimensional waveguides where atom-atom interactions and external potentials are nonvanishing only in a finite region of space. In this case, the truncated Wigner method is combined with the smooth exterior complex scaling method and incorporates quantum noise that originate from the vacuum fluctuations in the waveguide. Inelastic scattering is shown to play a major role in the resonant transport of BEC through a symmetric double potential barrier effectively forming an atomic quantum dot. Indeed, fully resonant transmission is prohibited and incoherent atoms as well as collective oscillations are detected in the transmitted beam. It is also shown that inelastic scattering destroys Anderson localization in the case of transport through disordered potentials. The classical (incoherent) ohmic transmission is recovered for finite atom-atom interactions. The validity of the truncated Wigner method is then assessed using the semiclassical van Vleck-Gutzwiller propagator in the Fock space of the many-body system. It is shown that the truncated Wigner method corresponds to the so-called diagonal approximation, and it is possible to identify the leading correction to the truncated Wigner results, which is provided by the so-called coherent backscattering (CBS) contribution. Coherent basckattering in Fock space is a genuine quantum many-body effect that lies beyond the reach of any mean-field approach. For the case of closed Bose-Hubbard models, the relevance of CBS is confirmed by numerically comparing the (classical) truncated Wigner evolution probabilities to the exact quantum probabilities in Bose-Hubbard models: While a CBS-induced enhancement of the return probability to the initial state is clearly seen in the exact quantum simulations of the bosonic many-body system, this enhancement is absent in the classical calculations. The magnitude and dependence of the CBS contribution on gauge fields, which break time-reversal invariance, is numerically confirmed. For the case of disordered open systems, it can be shown that this contribution as well as next-to leading order contributions vanish thereby confirming the validity of the truncated Wigner method. [less ▲]

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See detailStroboscopic phenomena in superconductors with dynamic pinning landscape
Jelic, Zeljko ULg; Milosevic, Milorad; Van de Vondel, Joris et al

in Scientific Reports (2015), 5

Introducing artificial pinning centers is a well established strategy to trap quantum vortices and increase the maximal magnetic field and applied electric current that a superconductor can sustain ... [more ▼]

Introducing artificial pinning centers is a well established strategy to trap quantum vortices and increase the maximal magnetic field and applied electric current that a superconductor can sustain without dissipation. In case of spatially periodic pinning, a clear enhancement of the superconducting critical current arises when commensurability between the vortex configurations and the pinning landscape occurs. With recent achievements in (ultrafast) optics and nanoengineered plasmonics it has become possible to exploit the interaction of light with superconductivity, and create not only spatially periodic imprints on the superconducting condensate, but also temporally periodic ones. Here we show that in the latter case, temporal matching phenomena develop, caused by stroboscopic commensurability between the characteristic frequency of the vortex motion under applied current and the frequency of the dynamic pinning. The matching resonances persist in a broad parameter space, including magnetic field, driving current, or material purity, giving rise to unusual features such as externally variable resistance/impedance and Shapiro steps in current-voltage characteristics. All features are tunable by the frequency of the dynamic pinning landscape. These findings open further exploration avenues for using flashing, spatially engineered, and/or mobile excitations on superconductors, permitting us to achieve advanced functionalities. [less ▲]

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See detailZigzag antiferromagnetic quantum ground state in monoclinic honeycomb lattice antimonates A3Ni2SbO6 (A=Li, Na)
Zvereva, E.A.; Stratan, M.I.; Ovchenkov, Y.A. et al

in Physical Review. B: Condensed Matter and Materials Physics (2015), 92

We present a comprehensive experimental and theoretical study of the electronic and magnetic properties of two quasi-two-dimensional (2D) honeycomb-lattice monoclinic compounds A3Ni2SbO6 (A=Li, Na ... [more ▼]

We present a comprehensive experimental and theoretical study of the electronic and magnetic properties of two quasi-two-dimensional (2D) honeycomb-lattice monoclinic compounds A3Ni2SbO6 (A=Li, Na). Magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic (AFM) long range order at low temperatures with Néel temperatures ~ 14 and 16 K for Li3Ni2SbO6 and Na3Ni2SbO6, respectively. The effective magnetic moments of 4.3 Bohr magnetons/f.u. (Li3Ni2SbO6) and 4.4 Bohr magnetons/f.u. (Na3Ni2SbO6) indicate that Ni2+ is in a high-spin configuration (S=1). The temperature dependence of the inverse magnetic susceptibility follows the Curie-Weiss law in the high-temperature region and shows positive values of the Weiss temperature ~ 8 K (Li3Ni2SbO6) and ~12 K (Na3Ni2SbO6) pointing to the presence of non-negligible ferromagnetic interactions, although the system orders AFM at low temperatures. In addition, the magnetization curves reveal a field-induced (spin-flop type) transition below TN that can be related to the magnetocrystalline anisotropy in these systems. These observations are in agreement with density functional theory calculations, which show that both antiferromagnetic and ferromagnetic intralayer spin exchange couplings between Ni2+ ions are present in the honeycomb planes supporting a zigzag antiferromagnetic ground state. Based on our experimental measurements and theoretical calculations we propose magnetic phase diagrams for the two compounds. [less ▲]

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See detailComment décrire la musique expérimentale ? Le cas de Vital Weekly
Claisse, Frédéric ULg

Conference (2015, October 01)

Publiée de manière interrompue sous forme de courrier hebdomadaire depuis 1995, le magazine Vital Weekly est un observateur privilégié de vingt ans d’évolution dans le domaine des musiques expérimentales ... [more ▼]

Publiée de manière interrompue sous forme de courrier hebdomadaire depuis 1995, le magazine Vital Weekly est un observateur privilégié de vingt ans d’évolution dans le domaine des musiques expérimentales. La communication revient sur ce corpus de 1001 numéros, qui voit les chroniqueurs progressivement inventer une forme de critique musicale radicale, gratuite et libre d’accès, sans prétention stylistique ou journalistique, visant l’informativité avant tout, à destination d’une communauté de lecteurs dont beaucoup sont eux-mêmes producteurs ou musiciens. Le magazine illustre la situation hybride des musiques expérimentales, appellation commode et fourre-tout pour des pratiques musicales extrêmement diversifiées, qui doivent autant aux traditions « savantes » du XXe siècle (field recordings, musique concrète, musiques électro-acoustiques, poésie sonore, …) qu’à l’esprit Do-It-Yourself et à l’esthétique industrielle de la cassette culture ayant émergé au tournant des années 1970-1980. D’inspiration pragmatique, l’analyse sociologique présentée ici prend au sérieux l’épreuve perceptive que représente pour le chroniqueur la rencontre avec un matériau sonore qui défie le jugement esthétique. Exemples à l’appui, il s’agit d’expliciter les « prises » de la critique sous contrainte de descriptivité : quels sont les repères conventionnels sur lesquels s’appuyer pour situer l’objet musical dans un espace structuré (paratexte, épitexte, descripteurs de genre, références intertextuelles) ? quels sont les registres (étrangeté, malaise, onirisme, puissance, intimité, présence à soi, matérialité et textures) qui permettent de transmettre au lecteur l’expérience sensible d’un face-à-face avec un objet sonore bouleversant ? [less ▲]

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See detailThe far-ultraviolet main auroral emission at Jupiter – Part 2: Vertical emission profile
Bonfond, Bertrand ULg; Gustin, Jacques ULg; Gérard, Jean-Claude ULg et al

in Annales Geophysicae (2015), 33

The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as ... [more ▼]

The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as it accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range. The energy of the precipitating electrons is a crucial parameter to characterize the processes at play which give rise to these auroral emissions, and the altitude of the emissions directly depends on this energy. Here we make use of far-UV (FUV) images acquired with the Advanced Camera for Surveys on board the Hubble Space Telescope and spectra acquired with the Space Telescope Imaging Spectrograph to measure the vertical profile of the main emissions. The altitude of the brightness peak as seen above the limb is ~ 400 km, which is significantly higher than the 250 km measured in the post-dusk sector by Galileo in the visible domain. However, a detailed analysis of the effect of hydrocarbon absorption, including both simulations and FUV spectral observations, indicates that FUV apparent vertical profiles should be considered with caution, as these observations are not incompatible with an emission peak located at 250 km. The analysis also calls for spectral observations to be carried out with an optimized geometry in order to remove observational ambiguities. [less ▲]

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See detailThe far-ultraviolet main auroral emission at Jupiter – Part 1: Dawn–dusk brightness asymmetries
Bonfond, Bertrand ULg; Gustin, Jacques ULg; Gérard, Jean-Claude ULg et al

in Annales Geophysicae (2015), 33

The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted ... [more ▼]

The main auroral emission at Jupiter generally appears as a quasi-closed curtain centered around the magnetic pole. This auroral feature, which accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range, is related to corotation enforcement currents in the middle magnetosphere. Early models for these currents assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ~ 3 times brighter than the dawn side in the southern hemisphere and ~ 1.1 brighter in the northern hemisphere, where the magnetic anomaly complicates the interpretation of the measurements. We suggest that such an asymmetry between the dawn and the dusk sectors could be the result of a partial ring current in the nightside magnetosphere. [less ▲]

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See detailKepler's first view of O-star variability: K2 data of five O stars in Campaign 0 as a proof of concept for O-star asteroseismology
Buysschaert, B.; Aerts, C.; Bloemen, S. et al

in Monthly Notices of the Royal Astronomical Society (2015), 453

We present high-precision photometric light curves of five O-type stars observed with the refurbished Kepler satellite during its Campaign 0. For one of the stars, we also assembled high-resolution ground ... [more ▼]

We present high-precision photometric light curves of five O-type stars observed with the refurbished Kepler satellite during its Campaign 0. For one of the stars, we also assembled high-resolution ground-based spectroscopy with the HERMES spectrograph attached to the 1.2 m Mercator telescope. The stars EPIC 202060097 (O9.5V) and EPIC 202060098 (O7V) exhibit monoperiodic variability due to rotational modulation with an amplitude of 5.6 and 9.3 mmag and a rotation period of 2.63 and 5.03 d, respectively. EPIC 202060091 (O9V) and EPIC 202060093 (O9V:pe) reveal variability at low frequency but the cause is unclear. EPIC 202060092 (O9V:p) is discovered to be a spectroscopic binary with at least one multiperiodic β Cep-type pulsator whose detected mode frequencies occur in the range [0.11, 6.99] d[SUP]-1[/SUP] and have amplitudes between 0.8 and 2.0 mmag. Its pulsation spectrum is shown to be fully compatible with the ones predicted by core-hydrogen burning O-star models. Despite the short duration of some 33 d and the limited data quality with a precision near 100 μmag of these first K2 data, the diversity of possible causes for O-star variability already revealed from campaigns of similar duration by the MOST and CoRoT satellites is confirmed with Kepler. We provide an overview of O-star space photometry and give arguments why future K2 monitoring during Campaigns 11 and 13 at short cadence, accompanied by time-resolved high-precision high-resolution spectroscopy, opens up the possibility of in-depth O-star seismology. [less ▲]

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See detailKIC 4768731: a bright long-period roAp star in the Kepler field
Smalley, B.; Niemczura, E.; Murphy, S. J. et al

in Monthly Notices of the Royal Astronomical Society (2015), 452

We report the identification of 61.45 d[SUP]-1[/SUP] (711.2 μHz) oscillations, with amplitudes of 62.6 μmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17 ... [more ▼]

We report the identification of 61.45 d[SUP]-1[/SUP] (711.2 μHz) oscillations, with amplitudes of 62.6 μmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21 d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of T[SUB]eff[/SUB] = 8100 ± 200 K, log g = 4.0 ± 0.2, [Fe/H] = +0.31 ± 0.24 and v sin i = 14.8 ± 1.6 km s[SUP]-1[/SUP]. Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar T[SUB]eff[/SUB] and log g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr. [less ▲]

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See detailPrediction of Allogeneic Hematopoietic Stem-Cell Transplantation Mortality 100 Days After Transplantation Using a Machine Learning Algorithm: A European Group for Blood and Marrow Transplantation Acute Leukemia Working Party Retrospective Data Mining Study
SHOUVAL, Roni; LABOPIN, Myriam; BONDI, Ori et al

in Journal of Clinical Oncology (2015), 33(28), 3144-3152

Purpose: Allogeneic hematopoietic stem-cell transplantation (HSCT) is potentiallu curative for acute leukemia (AL), but carries considerable risk. Machine learning algorithms, which are part of the data ... [more ▼]

Purpose: Allogeneic hematopoietic stem-cell transplantation (HSCT) is potentiallu curative for acute leukemia (AL), but carries considerable risk. Machine learning algorithms, which are part of the data mining (DM) approach, may serve for transplantation-related mortality risk prediction. Patients and Methods: This work is a retrospective DM study on a cohort of 28,236 adult HSCT recipients from the AL registry of the European Group for Blood and Marrow Transplantation. The primary objective was prediction of overall mortality (OM) at 100 days after HSCT. Secondary objectives were estimation of nonrelapse mortality, leukemia-free survival, and overall survival at 2 years. Donor, recipient, and procedural characteristics were alalyzed. The alternating decision tree machine learning algorithm was applied for model development on 70 % of the data set and validated on the remaining data. [less ▲]

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See detailDGTs, a complementary tool towards more efficient biomonitoring practices
Richir, Jonathan ULg; Lepoint, Gilles ULg; Donnay, Annick et al

Conference (2015, October 01)

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved ... [more ▼]

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved concentrations only gives punctual and fluctuating information, and often remains below detection limits of analytical methods. The more appropriate use of sentinel organisms, or bioindicators, to monitor TEs has thus often been preferred in environmental surveys. The introduction of the diffusive gradients in thin films (DGTs) technique has however participated to progressively change this binary view - bioindicator vs water - of the coastal monitoring of TEs, and DGTs rapidly became a relevant complementary tool to bioindicators, has illustrated below. In the framework of the STARECAPMED project, the ecology and the ecotoxicology of TEs were studied in the seagrass Posidonia oceanica (L.) Delile and the mussel Mytilus galloprovincialis Lamarck, 1819. DGTs (free- and pore-water probes) were deployed before sampling of organisms. TEs were also analyzed in suspended matter (dissolved and suspended-particulate TE speciation). Studies were performed in the Calvi Bay (Corsica, France), northwestern Mediterranean. TE concentrations in organisms and suspended matter or in DGT resins were measured by DRC-ICP-MS after HNO3/H202 mineralization or after a 24h elution in HNO3 1M, respectively. (1) TE bioaccumulation was first seasonally studied in P. oceanica over 3 years. Dissolved TE concentrations monitored with DGTs were low to very low. TE bioaccumulation dynamics in P. oceanica could thus be linked to the natural physiological cycle of the plant, in clean environmental conditions. (2) To complement that field survey, isolated seagrasses were in situ contaminated with TEs at environmental relevant concentrations. Through the use of DGTs, TE uptake kinetics were modelled for seagrasses exposed to know bioavailable concentrations of contaminants, as were loss kinetics during the following depuration phase. The TE sequestration ability of a healthy P. oceanica meadow facing sudden trace metal contamination events could also be quantified. (3) The deployment of pore-water DGT probes in bare-sand or seagrass colonized sediments further showed that, through its stabilizing function of the seabed, P. oceanica maintained higher TE levels in the pore-water. P. oceanica meadows thus offer a significant “depuration-filtering” ecological service along highly anthropized Mediterranean coasts. M. galloprovincialis are widely used in large spatial scale coastal monitoring surveys. (4) The deployment of caged mussels together with DGTs showed that the little contaminated water body of the Calvi Bay was relatively homogenous. It also allowed to calculate TE bioaccumulation towards mussels in reference conditions, and to compare it to native mussel populations. (5) Finally, during a 5 months mussel caging survey, mussels and suspended matter were collected weekly to monthly, such as were deployed DGTs. The physiological status of mussels, the speciation of TEs between their dissolved and suspended-particulate phases, and their relative influence on TE bioaccumulation dynamics in mussels were investigated. In conclusion, these case studies properly demonstrate how DGT probes can be used as a relevant and complementary tool to bioindicators. Their concomitant use should therefore be privileged in monitoring surveys. [less ▲]

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See detailL'année européenne du patrimoine architectural et ses répercussions au Grand-Duché de Luxembourg: une "procession d'Echternach" ?
Desseilles, François ULg; Langini, Alex

in Falser, Michael; Lipp, Wilfried (Eds.) Eine Zukunft für unsere Vergangenheit. Zum 40. Jubiläum des Europäischen Denkmalschutzjahres (1975–2015) (2015)

The contribution deals, mainly from parliamentary documents and legislation, with the encountering and embracing of the EAHY in the Grand Duchy of Luxembourg. The analysis concerns the preparation of ... [more ▼]

The contribution deals, mainly from parliamentary documents and legislation, with the encountering and embracing of the EAHY in the Grand Duchy of Luxembourg. The analysis concerns the preparation of activities and their achievement as well as the parliamentary discussions and the legal consequences of the EAHY. A positive effect of the campaign was the creation of a distinct built heritage service within the Ministry of Culture and the evolution of the legislation. Another positive effect was the advocacy work and the awareness of the people, a.o. thanks to a traveling exhibition on architecture in the Grand Duchy of Luxembourg. [less ▲]

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See detailGeometrical validity of curvilinear pyramidal finite elements
Johnen, Amaury ULg; Geuzaine, Christophe ULg

in Journal of Computational Physics (2015), 299

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