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See detailClose pairs of quasars with different redshifts: New observations and results
Sluse, Dominique ULg; Surdej, Jean ULg; Claeskens, Jean-François ULg et al

in Astronomy and Astrophysics (2003), 397

Burbidge et al. (\cite {burbidge}) argue that the observed number of quasar pairs with small angular separations and different redshifts (typically Delta theta <= 5 arcsec and Delta z > 0.1 ) is not ... [more ▼]

Burbidge et al. (\cite {burbidge}) argue that the observed number of quasar pairs with small angular separations and different redshifts (typically Delta theta <= 5 arcsec and Delta z > 0.1 ) is not compatible with a random distribution of quasars over the sky. After a brief review of all known quasar pairs with different redshifts, we show by means of very simple calculations that the probability of finding the three accepted pairs accidentally is of the order of 10%. We conclude that, under realistic hypotheses, the observed number of quasar pairs with different redshifts is not unlikely. We also present arguments showing that gravitational lensing biases are probably not strong enough to significantly increase the expected number of quasar pairs. The failure to detect with HST a secondary lensed image of the background quasar near the foreground one in these three pairs supports this view. [less ▲]

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See detailClose projected QSO-Galaxy associations: are they real?
Claeskens, Jean-François ULg; Surdej, Jean ULg

in Astronomy and Astrophysics (1998), 335

The present status of close projected associations between high redshift quasars and foreground galaxies is reviewed in the framework of gravitational lensing, adopting both an observational and a ... [more ▼]

The present status of close projected associations between high redshift quasars and foreground galaxies is reviewed in the framework of gravitational lensing, adopting both an observational and a theoretical approach. The Non Singular Isothermal Spherical lens model (Hinshaw & Krauss 1987) is used. We confirm that a stronger overdensity q of bright galaxies is expected at small projected angular separations (<= 3arcsec ) from high redshift and bright (thus highly luminous) quasars (HLQs). The effects of a non singular galactic core radius and/or microlensing only slightly enhance this expected overdensity. The predictions reproduce pretty well the scarce observations which are presently available, with the exception of two rather high overdensities previously claimed in the literature (e.g. q=2.9 for theta <= 6arcsec , Webster & Hewett 1990). Uncontrolled morphological selections may affect these controversial results so that additional unbiased observations are badly needed before rejecting gravitational lensing as the mechanism to produce the observed close angular QSO-galaxy associations. We describe three new selected and bias-free samples consisting of a total of 219 different HLQs. Although an apparent overdensity is detected in two of them, these galaxy excesses are found to be statistically not significant. Firm confirmation of the reality of close projected QSO-Galaxy associations is hampered by small number statistics: the expected and observed absolute numbers of such QSO-galaxy associations are still presently found to be very small. Therefore, the corresponding error bars are quite large. We conclude that the best observational strategy to significantly detect (at 3sigma ) an overdensity of galaxies near HLQs is to observe about 1500 HLQs (M_V ~ -29) down to a limiting magnitude Rlim ~ 23. Future automated surveys may provide us with such a large and unbiased database. In conclusions, we find that the lensing-induced correlation between galaxies and HLQs at small angular separations consists of a very interesting but weak effect, much less sensitive to cosmological or astrophysical parameters than the number of multiply imaged sources expected within a sample of HLQs. Based on data collected at the European Southern Observatory, La Silla, Chile [less ▲]

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See detailClose-packed array of gold nanoparticles and Sum Frequency Generation spectroscopy in total internal reflection: A platform for studying biomolecules and biosensors
Tourillon, Gérard; Dreesen, Laurent ULg; Volcke, Cédric et al

in Journal of Materials Science (2009), 44(24), 6805-6810

An approach is introduced for studying the adsorption and recognition mechanisms of biomolecules, without using any markers. We show for the first time, that the Sum Frequency Generation spectroscopy ... [more ▼]

An approach is introduced for studying the adsorption and recognition mechanisms of biomolecules, without using any markers. We show for the first time, that the Sum Frequency Generation spectroscopy performed in the Total Internal Reflection (TIR-SFG) geometry, combined with a regular close-packed array of gold nanoparticles allows to probe with a high sensitivity the changes in conformation and orientation induced by the recognition process of avidin by biocytin. This approach represents a new platform with potential use in biosensors, diagnostics and bioactive layers. [less ▲]

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See detailClose-up of primary and secondary asteroseismic CoRoT targets and the ground-based follow-up observations
Uytterhoeven, K.; Poretti, E.; Rainer, M. et al

in Journal of Physics Conference Series (2008), 118

To optimise the science results of the asteroseismic part of the CoRoT satellite mission a complementary simultaneous ground-based observational campaign is organised for selected CoRoT targets. The ... [more ▼]

To optimise the science results of the asteroseismic part of the CoRoT satellite mission a complementary simultaneous ground-based observational campaign is organised for selected CoRoT targets. The observations include both high-resolution spectroscopic and multicolour photometric data. We present the preliminary results of the analysis of the ground-based observations of three targets. A line-profile analysis of 216 high-resolution FEROS spectra of the δ Sct star HD 50844 reveals more than ten pulsation frequencies in the frequency range 5-18 d[SUP]-1[/SUP], including possibly one radial fundamental mode (6.92 d[SUP]-1[/SUP]). Based on more than 600 multi-colour photometric datapoints of the β Cep star HD 180642, spanning about three years and obtained with different telescopes and different instruments, we confirm the presence of a dominant radial mode ν[SUB]1[/SUB] = 5.48695 d[SUP]-1[/SUP], and detect also its first two harmonics. We find evidence for a second mode ν[SUB]2[/SUB] = 0.3017 d[SUP]-1[/SUP], possibly a g-mode, and indications for two more frequencies in the 7-8 d[SUP]-1[/SUP] domain. From Stromgren photometry we find evidence for the hybrid 5 Sct/γ Dor character of the F0 star HD 44195, as frequencies near 3 d[SUP]-1[/SUP] and 21 d[SUP]-1[/SUP] are detected simultaneously in the different filters. [less ▲]

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See detailClosed and Open Bodies: The Political Arts of Hunger and Disgust
Delville, Michel ULg

Conference (2014, May 28)

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See detailA closed form solution of the two body problem in non-inertial reference frames
Condurache, Daniel; Martinusi, Vladimir ULg

in Advances in the Astronautical Sciences (2012), 143

A comprehensive analysis, together with the derivation of a closed form solution to the two-body problem in arbitrary non-inertial reference frames are made within the present work. By using an efficient ... [more ▼]

A comprehensive analysis, together with the derivation of a closed form solution to the two-body problem in arbitrary non-inertial reference frames are made within the present work. By using an efficient mathematical instrument, which is closely related to the attitude kinematics methods, the motion in the non-inertial reference frame is completely solved. The closed form solutions for the motion in the non-inertial frame, the motion of the mass center, and the relative motion are presented in the paper. Dynamical characteristics analogue to the linear momentum, angular momentum and total energy are introduced. In the general situation, these quantities may be determined as functions of time, and their derivation is presented within the paper. In the situation where the non-inertial frame has only a rotation motion, these quantities become first integrals in a larger sense, with respect to an adequately defined differentiation rule. [less ▲]

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See detailA closed form technique to predict springback in creep age-forming
Jeunechamps, Pierre-Paul ULg; Ho, K. C.; Lin, J. et al

in International Journal of Mechanical Sciences (2006), 48(6), 621-629

An efficient numerical method has been developed and programmed to predict springback in creep age-forming (CAF) of alummium shell components. Physically based unified creep-ageing constitutive equations ... [more ▼]

An efficient numerical method has been developed and programmed to predict springback in creep age-forming (CAF) of alummium shell components. Physically based unified creep-ageing constitutive equations determined for AA7010 at 150 degrees C are used to evaluate age-hardening and creep deformation in CAF processes. The studies are mainly concentrated on the pure bending of aluminium plates. Effects of plate thickness, single and double curvature bending, ageing time and stress relaxation features on springback are investigated. It is shown that the proposed algorithm can predict springback accurately and gives a relationship between geometrical data and springback. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailA Closed Form Vectorial Solution to the Relative Orbital Motion
Condurache, Daniel; Martinusi, Vladimir ULg

in Publications of the Astronomy Department of the Eotvos Lorand University (2007), 19

Time-explicit solutions for relative Keplerian dynamics are presented for the general case in which the reference trajectory is elliptic, parabolic or hyperbolic. The non-linear differential equation ... [more ▼]

Time-explicit solutions for relative Keplerian dynamics are presented for the general case in which the reference trajectory is elliptic, parabolic or hyperbolic. The non-linear differential equation modeling the motion is solved by means of tensorial and vectorial regularization methods. This regularizing procedure extends the approaches of Levi-Civita and Kustaanheimo-Stiefel in the case of Kepler problem in rotating reference frames. The solution generalizes the approximate results obtained from Hill-Clohessy-Wiltshire, Lawden and Tschauner-Hempel equations. The approximate solutions derived from the liniarized models are in fact the first linear approximation of the exact solution the authors have found. [less ▲]

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See detailClosed-form dual perturb and combine for tree-based models
Geurts, Pierre ULg; Wehenkel, Louis ULg

in Proceedings of the International Conference on Machine Learning (ICML 2005) (2005)

This paper studies the aggregation of predictions made by tree-based models for several perturbed versions of the attribute vector of a test case. A closed-form approximation of this scheme combined with ... [more ▼]

This paper studies the aggregation of predictions made by tree-based models for several perturbed versions of the attribute vector of a test case. A closed-form approximation of this scheme combined with cross-validation to tune the level of perturbation is proposed. This yields soft-tree models in a parameter free way, and reserves their interpretability. Empirical evaluations, on classification and regression problems, show that accuracy and bias/variance tradeoff are improved significantly at the price of an acceptable computational overhead. The method is further compared and combined with tree bagging. [less ▲]

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See detailClosed-Form Solutions for Open Orbits Around an Oblate Planet
Martinusi, Vladimir ULg; Gurfil, Pini

in Advances in the Astronautical Sciences (2012)

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See detailClosed-form solutions for satellite relative motion in an axially-symmetric gravitational field
Martinusi, Vladimir ULg; Gurfil, P.

in Advances in the Astronautical Sciences (2011), 140

A different approach is proposed for the study of satellite relative motion in an axially-symmetric gravitational field. Instead of using the Keplerian motion as the generating nominal orbit for the ... [more ▼]

A different approach is proposed for the study of satellite relative motion in an axially-symmetric gravitational field. Instead of using the Keplerian motion as the generating nominal orbit for the absolute motion, another "unperturbed" orbit is proposed instead: An equatorial orbit about an oblate planet. Based on the superintegrability of such motion, closed-form solutions for the equatorial relative motion are obtained. Analytic conditions for the periodicity of the relative motion in a generic central force field are presented, and utilized to design long-term bounded relative motion under high-order even zonal perturbations. [less ▲]

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See detailClosed-Loop Learning of Visual Control Policies
JODOGNE, Sébastien ULg

Doctoral thesis (2006)

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See detailClosed-Loop Learning of Visual Control Policies
Jodogne, Sébastien ULg; Piater, Justus ULg

in Journal of Artificial Intelligence Research (2007), 28

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See detailClosed-loop model of the cardiovascular system including ventricular interaction and valve dynamics: application to pulmonary embolism
Desaive, Thomas ULg; Dutron, S.; Lambermont, Bernard ULg et al

in 12th International Conference on Biomedical Engineering (2005)

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See detailClosed-loop transient stability emergency control
Ernst, Damien ULg; Pavella, Mania ULg

in Proceedings of the IEEE Power Engineering Society Winter Meeting 2000 (2000)

The question of transient stability control is revisited, various types of controls are identified, and a general approach to closed-loop emergency control is proposed. The focus is on feasibility aspects ... [more ▼]

The question of transient stability control is revisited, various types of controls are identified, and a general approach to closed-loop emergency control is proposed. The focus is on feasibility aspects, general salient features and illustration of stabilization capabilities of an emergency control scheme relying on generation shedding. [less ▲]

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See detailA closer eye on hedge funds' dynamic hedging
Babaei, Hamid; Muller, Aline ULg; Lambert, Marie ULg

Conference (2013, April 18)

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See detailCloser look at the low-frequency dynamics of vortex matter using scanning susceptibility microscopy
Raes, Bart; de Souza Silva, Clecio C.; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2014), 90

Using scanning susceptibility microscopy, we shed new light on the dynamics of individual superconducting vortices and examine the hypotheses of the phenomenological models traditionally used to explain ... [more ▼]

Using scanning susceptibility microscopy, we shed new light on the dynamics of individual superconducting vortices and examine the hypotheses of the phenomenological models traditionally used to explain the macroscopic ac electromagnetic properties of superconductors. The measurements, carried out on a 2H-NbSe2 single crystal at relatively high temperature T = 6.8 K, show a linear amplitude dependence of the global ac-susceptibility for excitation amplitudes between 0.3 and 2.6 Oe. We observe that the low amplitude response, typically attributed to the oscillation of vortices in a potential well defi ned by a single, relaxing, Labusch constant, actually corresponds to strongly non-uniform vortex shaking. This is particularly pronounced in the fi eld-cooled disordered phase, which undergoes a dynamic reorganization above 0.8 Oe as evidenced by the healing of lattice defects and a more uniform oscillation of vortices. These observations are corroborated by molecular dynamics simulations when choosing the microscopic input parameters from the experiments. The theoretical simulations allow us to reconstruct the vortex trajectories providing deeper insight in the thermally induced hopping dynamics and the vortex lattice reordering. [less ▲]

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See detailClosing address for the session "Bullks and Characterization"
Vanderbemden, Philippe ULg

Conference (2010, November)

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See detailClosing the Ring: A Fourth Extracellular Loop in Chemokine Receptors
Szpakowska, Martyna ULg; Perez Bercoff, Danielle; Chevigné, Andy

in Science Signaling (2014), 7(34),

Chemokine receptors are heterotrimeric guanine nucleotide binding protein (G protein) coupled receptors (GPCR) that play fundamental roles in many physio- logical and pathological processes. Typically ... [more ▼]

Chemokine receptors are heterotrimeric guanine nucleotide binding protein (G protein) coupled receptors (GPCR) that play fundamental roles in many physio- logical and pathological processes. Typically, these receptors form a seven-trans- membrane helix bundle, which is stabilized by a disulfi de bond bridging the top of the third transmembrane segment (TM3) and the second extracellular loop (ECL2). Resolution of the three-dimensional structures of the chemokine receptors CXCR1, CXCR4, and CCR5 revealed the existence of a second disulfi de bridge that links the N terminus of the receptor to the top of the seventh transmembrane segment (TM7), thereby closing the receptor into a ring. An important consequence of this second disulfi de bond is the formation of an additional extracellular loop, which shapes the entrance of the ligand-binding pocket and adds rigidity to the overall surface of the receptor. Here, we discuss the features of these pseudo-loops, the structural re- quirements for their formation, and the effects they may have on receptor function [less ▲]

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See detailClostridia and enterotoxaemia
Mainil, Jacques ULg

Conference (2006)

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