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See detailAstroPoles : Astronomy from the Polar Plateaus; The astronomy program for the International Polar Year
Burton, M.; et al.; Surdej, Jean ULg et al

Poster (2006, August)

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See detailAstrospheres of young and old stars
Cox, N.; Decin, L.; Marle, A.J. et al

Poster (2013, October)

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See detailLas astucias de la ilusión. El ”caso” Mallarmé
Durand, Pascal ULg

in Sanz Roig, Diana (Ed.) Bourdieu después de Bourdieu (2014)

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See detailAsymmetric Diels-Alder reactions of a nitroso compound derived from D-bornane-10,2-sultam
Gouverneur, Véronique; Dive, Georges ULg; Ghosez, Léon

in Tetrahedron, Asymmetry (1991), 2(12), 1173-1176

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See detailAsymmetric dihydroxylation of C,C double bonds using catalytic amounts of osmium tetroxide, selenides, and air
Krief, A.; Colaux, Catherine ULg

in Pure & Applied Chemistry (2002), 74(1), 107-113

Selenides, selenoxides, osmium tetroxide, and potassium osmate dihydrate are in equilibrium in aqueous tert-butanol containing potassium carbonate. We took advantage of this feature to withdraw the ... [more ▼]

Selenides, selenoxides, osmium tetroxide, and potassium osmate dihydrate are in equilibrium in aqueous tert-butanol containing potassium carbonate. We took advantage of this feature to withdraw the equilibrium in each of the two directions to produce allylalcohols from allylselenides and diols from olefins. The latter reaction performed in the presence of catalytic amounts of Cinchona alkaloids and osmium tetroxide allows the enantioselective dihydroxylation of C,C double bonds. [less ▲]

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See detailAsymmetric facial skin viscoelasticity during climacteric aging.
Pierard, Gérald ULg; Hermanns-Lê, Trinh ULg; Gaspard, Ulysse ULg et al

in Clinical, cosmetic and investigational dermatology (2014), 7

BACKGROUND: Climacteric skin aging affects certain biophysical characteristics of facial skin. The purpose of the present study was to assess the symmetric involvement of the cheeks in this stage of the ... [more ▼]

BACKGROUND: Climacteric skin aging affects certain biophysical characteristics of facial skin. The purpose of the present study was to assess the symmetric involvement of the cheeks in this stage of the aging process. METHODS: Skin viscoelasticity was compared on both cheeks in premenopausal and post-menopausal women with indoor occupational activities somewhat limiting the influence of chronic sun exposure. Eighty-four healthy women comprising 36 premenopausal women and 48 early post-menopausal women off hormone replacement therapy were enrolled in two groups. The tensile characteristics of both cheeks were tested and compared in each group. A computerized suction device equipped with a 2 mm diameter hollow probe was used to derive viscoelasticity parameters during a five-cycle procedure of 2 seconds each. Skin unfolding, intrinsic distensibility, biological elasticity, and creep extension were measured. RESULTS: Both biological elasticity and creep extension were asymmetric on the cheeks of the post-menopausal women. In contrast, these differences were more discrete in the premenopausal women. CONCLUSION: Facial skin viscoelasticity appeared to be asymmetric following menopause. The possibility of asymmetry should be taken into account in future studies of the effects of hormone replacement therapy and any antiaging procedure on the face in menopausal women. [less ▲]

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See detailAsymmetric Foreign Exchange Risk Exposure: evidence from U.S. multinationals
Muller, Aline ULg; Verschoor, Willem

in Journal of Empirical Finance (2006), 13

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See detailAsymmetric Optical Second-Harmonic Generation from Chiral G-Shaped Gold Nanostructures
Valev, V. K.; Silhanek, Alejandro ULg; Verellen, N. et al

in Physical Review Letters (2010), 104(12),

We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating ... [more ▼]

We present a new electromagnetic phenomenon-the asymmetric second-harmonic generation from planar chiral structures. The effect consists in distinguishing the handedness of a chiral material by rotating the sample in an experiment involving solely linearly polarized light. This phenomenon originates in the surface plasmon resonance of chiral gold nanostructures, where homodyne interference of anisotropic and chiral electric and/or magnetic multipoles appears to play an important role. [less ▲]

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See detailAsymmetric synthesis of 4-[18F]fluoro-L-m-tyrosine via aromatic fluorination.
Lemaire, Christian ULg; Damhaut, Ph.; Plenevaux, Alain ULg et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1991), 32

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See detailAsymmetric synthesis of n.c.a. L-[2-11C]-4-chlorophenylalanine.
Plenevaux, Alain ULg; Al-Darwich, M. J.; Lemaire, Christian ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (1993), 32

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See detailAsymmetrical international attitudes
Van Oudenhoven, J.; Askevis-Leherpeux, F.; Hannover, B. et al

in European Journal of Social Psychology (2002), 32(2), 275-289

In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international ... [more ▼]

In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain asymmetrical attitudes. Parting from social identity theory, asymmetrical attitudes can be predicted to occur most likely between countries that are linguistically either similar or closely related, but differ in size. Europe, more than any other continent, offers a rich variety of nations which represent natural conditions for our study, such as size and degree of linguistic similarity. In order to test hypotheses derived from social identity theory, we asked respondents (N = 405) from (Dutch- and French-speaking) Belgium, France, Germany, and The Netherlands to fill out a questionnaire on three large nations (Germany, Great Britain, France) and three smaller ones (The Netherlands, Belgium, and Denmark). Results strongly supported hypotheses and confirm that a social identity approach may help to better understand international attitudes. [less ▲]

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See detailAsymptotic distribution of robust estimators of ability and applications
Magis, David ULg

Scientific conference (2013, October 31)

In item response theory (IRT), ability estimation can be seriously affected by abnormal responses occurring from e.g., cheating, inattention, lack of time, guessing, tiredness, stress… Those phenomena may ... [more ▼]

In item response theory (IRT), ability estimation can be seriously affected by abnormal responses occurring from e.g., cheating, inattention, lack of time, guessing, tiredness, stress… Those phenomena may influence the ability estimation process tremendously. One the one hand, person fit indices were developed as post-hoc approaches to identify abnormal responses patterns as a whole (e.g., Meijer & Sijtsma, 2001). On the other hand, getting uncontaminated ability estimates would also be a challenging issue. Robust estimators were proposed in the IRT framework to lessen the impact of abnormal responses onto the estimation process (Mislevy & Bock, 1982; Schuster & Yuan, 2011; Wainer & Wright, 1980). Yet, these estimators are still rarely used in practice, mostly because very little is known about their statistical properties. The purpose of this talk is to briefly present these robust ability estimators, and to derive their asymptotic distribution under mild regularity conditions. In particular, a simple formula for the asymptotic standard error (ASE) of these estimators is obtained (Magis, in press). Results of a simulation study that involves both presence and absence of cheating in the data generation process will be outlined. References: Magis, D. (in press). On the asymptotic standard error of a class of robust estimators of ability in dichotomous item response models. British Journal of Mathematical and Statistical Psychology. Meijer, R., & Sijtsma, K. (2001). Methodology review: Evaluating person fit. Applied Psychological Measurement, 25, 107-135. doi: 10.1177/01466210122031957 Mislevy, R. J., & Bock, R. D. (1982). Biweight estimates of latent ability. Educational and Psychological Measurement, 42, 725-737. doi: 10.1177/001316448204200302 Schuster, C., & Yuan, K.-H. (2011). Robust estimation of latent ability in item response models. Journal of Educational and Behavioral Statistics, 36, 720-735. doi: 10.3102/1076998610396890 Wainer, H., & Wright, B. D. (1980). Robust estimation of ability in the Rasch model. Psychometrika, 45, 373-391. doi: 10.1007/BF02293910 [less ▲]

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See detailAsymptotic expansion of slightly coupled modal dynamic transfer functions
Denoël, Vincent ULg; Degée, Hervé ULg

in Journal of Sound & Vibration (2009), 328

In case of non-diagonal modal damping, normal modes of vibration do not decouple modal equations. The usual way to handle such a non-diagonal modal damping matrix is to neglect its off-diagonal elements ... [more ▼]

In case of non-diagonal modal damping, normal modes of vibration do not decouple modal equations. The usual way to handle such a non-diagonal modal damping matrix is to neglect its off-diagonal elements. In this paper, we propose an approximatemethod based on an asymptotic expansion of the transfer function. It is intermediate between the classical decoupling approximation and the formal solution requiring a full matrix inversion. Indeed, on the one hand, it allows to partially account for modal coupling and, on the other hand, still allows the modal equations to be solved independently from each other. We first provide the mathematical background necessary to canvass the proposed method, then consider a benchmark against which the benefits of the method are measured. [less ▲]

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See detailAn asymptotic expansion-based method for a spectral approach in equivalent statistical linearization
Canor, Thomas ULg; Blaise, Nicolas ULg; Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2014), 38

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the ... [more ▼]

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the Gaussian equivalent linearization expresses the properties of an equivalent linear system in terms of the mean vector and the covariance matrix of the responses, which are the unknowns of the optimization problem in a spectral approach. Even though the system has been linearized, the resulting set of equations is nonlinear. The computational effort in this method pertains to the solution of a possibly large set of nonlinear algebraic equations involving integrals and inversions of full matrices. This work proposes to develop and apply an asymptotic expansion-based method to facilitate and to improve the statistical linearization for large nonlinear structures. The proposed developments demonstrate that for slightly to moderately coupled nonlinear systems, the equivalent linearization can be applied with an appropriate modal approach and eventually seen as a convergent series initiated with the stochastic response of a main decoupled linear system. With this method, the computational effort is attractively reduced, the conditioning of the set of nonlinear algebraic equations is improved and inversion of full transfer matrices and repeated integrations are avoided. The paper gives a formal description of the method and illustrates its implementation and performances with the computation of stationary responses of nonlinear structures subject to coherent random excitation fields. [less ▲]

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See detailAsymptotic properties of the error distribution estimation in right censored and selection biased regression models
Laurent, Géraldine ULg; Heuchenne, Cédric ULg

Conference (2012, June 16)

Suppose the random vector (X,Y) satisfies the nonparametric regression model Y=m(X)+sigma(X)*epsilon where m(X) =E [Y|X] and sigma^2(X) = Var [Y|X] are unknown smooth functions and the error epsilon, with ... [more ▼]

Suppose the random vector (X,Y) satisfies the nonparametric regression model Y=m(X)+sigma(X)*epsilon where m(X) =E [Y|X] and sigma^2(X) = Var [Y|X] are unknown smooth functions and the error epsilon, with unknown distribution, is independent of the covariate X. The pair (X,Y) is subject to generalized bias selection and the response Y to right censoring. We define a new estimator for the cumulative distribution function of the error epsilon, where the estimators of m(.) and sigma^2(.) are obtained by extending the conditional estimation methods introduced in de Uña-Alvarez and Iglesias-Perez (2010). The asymptotic properties of the proposed estimator are established. A bootstrap technique is proposed to select the smoothing parameter involved in the procedure. Finally, this method is studied via extended simulations and applied to real data. [less ▲]

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See detailAsymptotic solutions for the case of nearly symmetric gravitational lens systems
Wertz, Olivier ULg; Pelgrims, Vincent ULg; Surdej, Jean ULg

in Monthly Notices of the Royal Astronomical Society (2012), 424

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See detailAsymptotic stability conditions for time-variant systems and observability : uniform and non-uniform criteria
Aeyels, D.; Sepulchre, Rodolphe ULg; Peuteman, J.

in Mathematics of Control, Signals & Systems (1998), 11

This paper presents some new criteria for uniform and non uniform asymtotic stability of equilibria for time-variant differential equations and this within a Liapunov approach. The stability criteria are ... [more ▼]

This paper presents some new criteria for uniform and non uniform asymtotic stability of equilibria for time-variant differential equations and this within a Liapunov approach. The stability criteria are formulated in terms of certain observability conditions with the output derived from the Liapunov function. For some classes of systems, this system theoretic interpretation proves to be fruitful since - after establishing the invariance of observability under output injection - this enables us to check the stability criteria on a simpler system. This procedure is illustrated for some classical examples. [less ▲]

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See detailAsymptotic standard errors of robust estimators of ability in dichotomous item response models
Magis, David ULg

Conference (2013, October 10)

In item response theory, the classical estimators of ability are highly sensitive to response disturbances and can return strongly biased estimates of the true underlying ability level. Robust methods ... [more ▼]

In item response theory, the classical estimators of ability are highly sensitive to response disturbances and can return strongly biased estimates of the true underlying ability level. Robust methods were introduced to lessen the impact of such aberrant responses onto the estimation process. The computation of asymptotic (i.e., large sample) standard errors (ASE) for these robust estimators, however, has not been fully considered yet. This paper focuses on a broad class of robust ability estimators, de ned by an appropriate selection of the weight function and the residual measure, for which the ASE is derived from the theory of estimating equations. The maximum likelihood (ML) and the robust estimators, together with their estimated ASE, are then compared through a simulation study. It is concluded that both the estimators and their ASE perform similarly in absence of response disturbances, while the robust estimator and its estimated ASE are less biased and outperform their ML counterparts in presence of response disturbances with large impact on the item response process. [less ▲]

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