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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 solutions for the case of SIE lens models and application to the quadruply imaged quasar Q2237+0305
Wertz, Olivier ULg; Surdej, Jean ULg

in Monthly Notices of the Royal Astronomical Society (2014), 442(1), 428-439

Considering a small misalignment between a point-like source, a singular isothermal ellipsoid deflector and an observer, we derive to first order simple relations between the model parameters and the ... [more ▼]

Considering a small misalignment between a point-like source, a singular isothermal ellipsoid deflector and an observer, we derive to first order simple relations between the model parameters and the lensed image positions, and an expression for the time delay between pairs of opposed images which is analogue to the one previously derived for the case of ε - γ models. Combined with the first-order astrometric relations, we retrieve a simple expression for the time delays, in agreement with Witt, Mao & Keeton, which solely depends on the lensed image positions. The real advantage of using the first-order equations when dealing with symmetric gravitational lens systems is to directly test the validity of the adopted lens model without having to perform any accurate numerical fit. In this paper, we present in detail the calculations which lead to those relations between the singular isothermal ellipsoid lens model parameters and the lensed image positions. In addition, we model the well-known Einstein cross Q2237+0305 with three families of models: ε - γ, singular isothermal ellipsoid and non-singular isothermal ellipsoid plus shear, using a genetic algorithm from the Qubist Optimization Toolbox. We conclude that although the non-singular isothermal ellipsoid plus shear model shows the best agreement between the calculated and the observed image positions (〈 Δx〉 = 0.0026 arcsec), the more simple singular isothermal ellipsoid also leads to quite satisfactory and acceptable results (〈 Δx〉 = 0.0059 arcsec). © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. [less ▲]

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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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See detailAsymptotics of the S-matrix and unitarisation
Selyugin, O. V.; Cudell, Jean-René ULg

in Physics of Particles and Nuclei (2010), 41

The manner in which the elastic scattering amplitude obeys unitarity, how it enters the circle of unitarity, and what its asymptotic limit is, remains a problem for models which include terms that rise ... [more ▼]

The manner in which the elastic scattering amplitude obeys unitarity, how it enters the circle of unitarity, and what its asymptotic limit is, remains a problem for models which include terms that rise fast with s. We have checked that the features of cross sections which come from unitarisation are present for most unitarisation schemes, e.g. those that saturate the profile function or those that describe multiple exchanges via an analytic formula. We have also obtained a scheme which interpolates between different classes of the unitarisation and found corresponding non-linear equations. Considering different forms of energy dependence of the scattering amplitude, and a variety of unitarisation schemes, we show that, in order to reproduce the data, the fits choose an amplitude that corresponds to an asymptotic value S = 0. [less ▲]

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See detailAt Least Three Subdomains of V-Erba Are Involved in Its Silencing Function
Busch, Kerstin; Martin, Bernd; Baniahmad, Aria et al

in Molecular Endocrinology (1997), 11(3), 379-89

Several members of the thyroid hormone receptor (TR) family are able to switch from a transcriptional repressor to a transcriptional activator upon binding of their ligand. The oncogene v-erbA is a ... [more ▼]

Several members of the thyroid hormone receptor (TR) family are able to switch from a transcriptional repressor to a transcriptional activator upon binding of their ligand. The oncogene v-erbA is a variant form of the TR unable to bind hormone and thus acts as a constitutive repressor. We demonstrate, using fusion proteins between the DNA-binding domain of the yeast factor GAL4 and the silencing domains of v-erbA and TR beta, that point mutations in three different regions severely affect their repression function. Furthermore, the three regions, each as an inactive fusion protein with the GAL4 DNA-binding domain, restore silencing activity when assembled on the same promoter. These observations define at least three silencing subdomains, SSD1-SSD3, which are involved in the silencing function of v-erbA. We propose a model in which full silencing activity is brought about by the combined interaction of each silencing subdomain with corepressors and/or basal transcription factors. [less ▲]

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See detailAt least two expressed genes for transcription factors Pitx2 and Rpx are present in common carp and are upregulated during winter acclimatization.
Kausel, G.; Vera, T.; Valenzuela, G. et al

in General and Comparative Endocrinology (2010), 169(3), 250-257

The mechanisms of seasonal acclimatization in eurythermal fish such as common carp are not fully understood. Here, we concentrate on the regulation of pituitary factors, as this organ was shown to be ... [more ▼]

The mechanisms of seasonal acclimatization in eurythermal fish such as common carp are not fully understood. Here, we concentrate on the regulation of pituitary factors, as this organ was shown to be highly affected by seasonal changes. We cloned and sequenced two different cDNAs for each of the transcription factors Pitx2 and Rpx, known to play a role in pituitary development. We show that these genes are conserved throughout evolution, to different degrees depending on the specific domain considered. Finally, we show that the cDNAs for both factors are clearly up-regulated during the winter season, in sharp contrast to other regulators such as Pit1 or pituitary hormone genes such as prolactin (prl) and growth hormone (gh). Our results suggest that increased expression of Pitx2 and Rpx contributes to seasonal adaptation of common carp to winter conditions. [less ▲]

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See detailAt Least Two Regions Of The Oncoprotein Tre2 Are Involved In Its Lack Of Gap Activity
Bizimungu, C.; Vandenbol, Micheline ULg

in Biochemical and Biophysical Research Communications (2005), 335(3),

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See detailAt the center, what?’ Giacomo Joyce, Roland Barthes and the Novelistic Fragment
Delville, Michel ULg

in James Joyce Quarterly (1999), 36(4), 765-780

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See detailAt the crossing of physics and Aercheology : the OSIRIS project
Renotte, Yvon ULg; Laboury, Dimitri ULg; Tilkens, Bernard et al

in Europhysics News (2004), 35/6

How physics can help aercheology, including a path to the parket

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See detailAt the crossroad of thiamine degradation and biosynthesis
Bettendorff, Lucien ULg

in Nature Chemical Biology (2007), 3(8), 454-455

The physiological significance of thiaminase II has escaped our understanding for many years. The recent discovery of a new thiamine salvage pathway shows that this enzyme is involved in the regeneration ... [more ▼]

The physiological significance of thiaminase II has escaped our understanding for many years. The recent discovery of a new thiamine salvage pathway shows that this enzyme is involved in the regeneration of precursors for thiamine biosynthesis. [less ▲]

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See detailAt the Crossroads of Greek and Roman Medicine: The Contribution of Latin Papyri. 1. Medical Texts; 2. Iatromagical Papyri
de Haro Sanchez, Magali ULg; Marganne, Marie-Hélène ULg

in Maire, Brigitte (Ed.) "Greek" and "Roman" in Latin Medical Texts. Studies in Cultural Change and Exchange in Ancient Medicine (2014)

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See detailAt the Crossroads of Greek and Roman Medicine: the Contribution of Latin Papyri. I. Medical Texts
Marganne, Marie-Hélène ULg

in Maire, Brigitte (Ed.) 'Greek' and 'Roman' in Latin Medical Texts. Studies in Cultural Change and Exchange in Ancient Medicine (2014, July)

Far fewer Latin medical papyri, whether paraliterary, documentary or magical, have survived compared to Greek medical papyri, but they nonetheless provide interesting information about medical practices ... [more ▼]

Far fewer Latin medical papyri, whether paraliterary, documentary or magical, have survived compared to Greek medical papyri, but they nonetheless provide interesting information about medical practices in the Graeco-Roman world, the relationship between Greek and Latin medical languages, and the choices made to use one rather than the other, a subject that has never been exhaustively studied. As part of the update undertaken by CEDOPAL since 2008 of the Corpus Papyrorum Latinarum, published fifty years ago by the late Robert Cavenaile, we have inventoried Latin papyri containing medical references, classifying them by type or nature of content, provenance, form, layout and writing. We finally analyse their content and what it reveals about the reception of Greek medicine by Latin or Latin-speeking writers. [less ▲]

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See detailAt the Cutting Edge. Biosynthesis and Paracrine/Cryptocrine Actions of 'Self' Neurohypophysial-Related Peptides in the Thymus
Geenen, Vincent ULg; Robert, F.; Martens, Henri ULg et al

in Molecular & Cellular Endocrinology (1991), 76(1-3), 27-31

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See detailAt the heart of Jupiter’s aurora; at the crossroads of Astrophysics Geophysics and Plasma Physics
Grodent, Denis ULg

Scientific conference (2015, May 21)

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow ... [more ▼]

Auroral physics is at the intersection of more general fields of physics such as Astrophysics, Geophysics and Plasma Physics. In particular, the giant planets Jupiter and Saturn may be seen as slow rotating pulsars. For these two planets, there is a direct link between this pulsar-like behaviour and the auroral processes that are taking place in their atmosphere. We will take the example of Jupiter to illustrate haw the aurora is generated in the magnetosphere as a result of the volcanic activity of the moon Io. The ultraviolet aurora of Jupiter is conveniently described in terms of components located inside (poleward of) or outside (equatorward of) the main oval emission. However, these components may also be discriminated by their temporal behaviour, where the narrowest parts of the main “oval” remain relatively stable over time periods of several hours, and the satellite footprints show large variability with timescales of minutes. Inside the main emission, at the heart of the aurora, the so-called polar aurora, presumably corresponding to the polar cap mixing open and closed magnetic field lines, is characterized by rapid motions taking the form of swirls, giving rise to the “swirl region” and by beatings in the “active region”. This delicate auroral region is difficult to apprehend because of its ever-changing shape and because of the lack of appropriate tools to study it. [less ▲]

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See detail“ At The Intersections Between Care Labor Migration and Transnational Family Care Circulation: The Case of Colombian and Ecuadorian Care-Workers in the Global City of Brussels.”
Vivas Romero, Maria ULg

Scientific conference (2014, May 08)

In Belgium, female migrant Care workers are key elements for the demographic challenges the country faces. The aging of the population and the insertion of native women in the labor market led to an ... [more ▼]

In Belgium, female migrant Care workers are key elements for the demographic challenges the country faces. The aging of the population and the insertion of native women in the labor market led to an increasing demand for their liable/affordable care-work. A relevant aspect that might help us to understand their careers toward their social and labor incorporation in Belgium are the informal circulations of care that take place within their transnational family networks; which shift over the life course and are subject to the political, economic, cultural and social contexts of both sending and receiving societies (Baldassar and Merla 2014). This paper focuses on the labor migration of Ecuadorian/Colombian care-workers in the global city of Brussels and aims to analyze the role of transnational family care circulations in these women’s social and labor incorporation in Belgium. In order to do so I will make use of a Care Circulation approach (Baldassar and Merla 2014), which allows me to: Firstly, understand the individual characteristics and changes in gender roles that either facilitates or constraints their mobilization of care. Secondly, link the individual level to the opportunities and constraints posed by the state institutions and migration regimes in this mobilization of care. Lastly, it allows me to take a look at the networks of co-nationals who over time sustain their incorporation in Belgium and their transnational caregiving practices. It is through the combination of these past three aspects that this research contributes to a better understanding of the feminization of care labor migration in Belgium; by analyzing transnational family care circulation and highlighting the role of family and the domestic sphere in supporting certain types of labor migration such as care-work. Ultimately, this paper highlights these women’s agency within their transnational families and migratory projects, and recognizes the heterogeneity in their strategies and profiles even within the so-called “care sector”. [less ▲]

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See detailAt the other end of the field lines: the satellite footprints
Bonfond, Bertrand ULg

Conference (2011, April)

The electromagnetic perturbations caused by the interaction between the moons Io, Europa, and Ganymede and the Jovian magnetosphere propagate along magnetic field lines in the form of Alfvén waves and ... [more ▼]

The electromagnetic perturbations caused by the interaction between the moons Io, Europa, and Ganymede and the Jovian magnetosphere propagate along magnetic field lines in the form of Alfvén waves and finally create auroral footprints in Jupiter’s polar ionosphere. Thanks to the high spatial and temporal resolution of the Hubble Space Telescope, the analysis of the footprints in the Far UV domain provides extremely valuable information on these interactions. In the case of the Io footprint, the analysis of the multiplicity of the auroral spots and of their relative motion resulted into a new understanding of the far field interaction, which involves trans-hemispheric electron beams. Consistent with the in-situ energetic electrons observations, this scenario has been later reinforced by theoretical models simulating the Alfvén wave’s propagation and the ways these waves accelerate electrons. Moreover, while the altitude and the vertical profile of the auroral emissions provide crucial information on the energy of the precipitating electrons, the measure of the shape of the different sub-structures of the satellite footprints provides important clues about the size of the interaction region. The evolution of the footprint brightness is also an essential parameter for understanding the energies involved in the interaction. Finally, the study of the satellite footprints can also be used for broader purposes than just the investigation of the satellite-magnetosphere interaction, such as building more accurate Jovian magnetic field models. [less ▲]

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See detailAt which level of vitamin D should we aim?
CAVALIER, Etienne ULg

Conference (2014, January 18)

Detailed reference viewed: 21 (2 ULg)