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See detailInherent modulation: a fast chopping method for nulling interferometry
Absil, Olivier ULg; Karlsson, Anders; Kaltenegger, Lisa

in Shao, Michael (Ed.) Interferometry in Space (2003, February 01)

The reduction of the thermal background emission from the local and exozodiacal dust clouds is a critical element for the success of ESA's space mission, DARWIN. Internal modulation, a technique using ... [more ▼]

The reduction of the thermal background emission from the local and exozodiacal dust clouds is a critical element for the success of ESA's space mission, DARWIN. Internal modulation, a technique using fast signal chopping, isolating the planetary signal from these noise sources, was proposed by Mennesson and Léger. In this paper, a short review of internal modulation is given, and new configurations with internal modulation are proposed to reduce the complexity of the beam-combining optics. A modification to the implementation of internal modulation is then investigated. It provides similar performance with a single detector and a greatly simplified optical layout: the number of beam-combiners is reduced by a factor of about two. The principle of inherent modulation is different from internal modulation in that no sub-interferometers are used: different phase shifts are applied to the input beams before recombination such that an asymmetric transmission map is obtained directly, without plus or minuspi/2 modulation as used in internal modulation. By combining the phase shifts and the input beams differently a transposed transmission map is obtained, allowing the signal to be chopped. During operations, multiplexing between the two interferometers is performed, such that at any time only one interferometer is being used. [less ▲]

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See detailInfluence of optical path delay control on a ground-based nulling interferometer
Absil, Olivier ULg; Coude du Foresto, Vincent

in Traub, Wesley (Ed.) Interferometry for Optical Astronomy II (2003, February 01)

Atmospheric turbulence is a major source of noise in any fiber-linked interferometer through the piston effect between the two arms of the interferometer which induces an erratic movement of the fringes ... [more ▼]

Atmospheric turbulence is a major source of noise in any fiber-linked interferometer through the piston effect between the two arms of the interferometer which induces an erratic movement of the fringes. Because the stellar light has to be permanently cancelled by the central dark fringe, a ground-based nulling interferometer is not possible without stringent optical path delay (OPD) control. In this paper, we investigate the influence of the residual OPD error of a fringe tracking unit on the performances of a nulling interferometer. The accuracy required for this control system strongly depends on the observation wavelength. If we want to detect exozodiacal clouds ten times as dense as our zodiacal dust cloud in the near-infrared (L' band), the performances of the fringe tracker are crucial: the residual OPD should be about 20 nanometers RMS. This specification can only be reached if the fringe sensor is optimized for bright sources. In the mid-infrared (N band), the requirements are strongly relaxed: OPD control with an accuracy of 400 nm RMS is sufficient to be background-limited, but a lower residual OPD (about 50 nm RMS) is strongly recommended to reduce the stellar leakage. [less ▲]

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See detailDarwin ground-based European nulling interferometer experiment (GENIE)
Gondoin, Philippe; Absil, Olivier ULg; Fridlund, C V Malcolm et al

in Traub, Wesley (Ed.) Interferometry for Optical Astronomy II (2003, February 01)

Darwin is one of the most challenging space projects ever considered by the European Space Agency (ESA). Its principal objectives are to detect Earth-like planets around nearby stars and to characterize ... [more ▼]

Darwin is one of the most challenging space projects ever considered by the European Space Agency (ESA). Its principal objectives are to detect Earth-like planets around nearby stars and to characterize their atmospheres. Darwin is conceived as a space "nulling interferometer" which makes use of on-axis destructive interferences to extinguish the stellar light while keeping the off-axis signal of the orbiting planet. Within the frame of the Darwin program, the European Space Agency (ESA) and the European Southern Observatory (ESO) intend to build a ground-based technology demonstrator called GENIE (Ground based European Nulling Interferometry Experiment). Such a ground-based demonstrator built around the Very Large Telescope Interferometer (VLTI) in Paranal will test some of the key technologies required for the Darwin Infrared Space Interferometer. It will demonstrate that nulling interferometry can be achieved in a broad mid-IR band as a precursor to the next phase of the Darwin program. The present paper will describe the objectives and the status of the project. [less ▲]

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See detailDesign and tests for the heliospheric imager of the STEREO mission
Defise, Jean-Marc ULg; Halain, Jean-Philippe ULg; Mazy, Emmanuel ULg et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2003, February 01)

The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO spacecrafts to be launched in 2005. The two HI instruments will provide stereographic image pairs of solar ... [more ▼]

The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO spacecrafts to be launched in 2005. The two HI instruments will provide stereographic image pairs of solar coronal plasma and coronal mass ejections (CME) over a wide field of view (~90°), ranging from 13 to 330 R[SUB]0[/SUB]. These observations compliment the 15 R[SUB]0[/SUB] field of view of the solar corona obtained by the other SECCHI instruments (2 coronagraphs and an EUV imager). The key challenge of the instrument design is the rejection of the solar disk light, with total straylight attenuation of the order of 10[SUP]-13 [/SUP]to 10[SUP]-15[/SUP]. A multi-vane diffractive baffle system has been theoretically optimized to achieve the lower requirement (10[SUP]-13[/SUP] for HI-1) and is combined with a secondary baffling system to reach the 10[SUP]-15[/SUP] rejection performance in the second camera system (HI-2). This paper presents the last updates of the SECCHI/HI design concept, with the expected performance. A verification program is currently in progress. The on-going stray-light verification tests are discussed. A set of tests has been conducted in air, and under vacuum. The results are presented and compared with the expected theoretical data. [less ▲]

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See detailLa mesure du débit de filtration glomérulaire en clinique quotidienne
Delanaye, Pierre ULg; Chapelle, Jean-Paul ULg; Ferir, Anne-Marie et al

in Revue Médicale de Liège (2003), 58(2), 95-100

Glomerular filtration rate (GFR) is the most frequently used parameter to evaluate the renal function. GFR may be estimated with serum creatinine, creatinine clearance based on 24 hours urine collection ... [more ▼]

Glomerular filtration rate (GFR) is the most frequently used parameter to evaluate the renal function. GFR may be estimated with serum creatinine, creatinine clearance based on 24 hours urine collection or Cockcroft formula. All these methods have bias. Other approaches have thus been proposed. The limitations and advantages of isotopic methods and recent mathematical approaches (MDRD formula) are reviewed. [less ▲]

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See detailDecentralized local backup LSP calculation with efficient bandwidth sharing
Mélon, Laurent; Blanchy, François; Leduc, Guy ULg

in 10th IEEE International Conference on Telecommunications (2003, February)

This paper focuses on the protection of virtual circuits (Label Switched Paths, LSPs) in a (G)MPLS (Generalised Multi-Protocol Label Switching) network. The proposed algorithm is designed to protect ... [more ▼]

This paper focuses on the protection of virtual circuits (Label Switched Paths, LSPs) in a (G)MPLS (Generalised Multi-Protocol Label Switching) network. The proposed algorithm is designed to protect traffic with strong delay requirements such as EF (Expedited Forwarding) ordered aggregates in a DiffServ domain. For this type of application endto- end recovery schemes are usually considered to be far too slow. Local, fast-rerouting is the only solution which can compete with restoration times offered by SONET self-healing ring. However local restoration has a cost in terms of extra bandwidth consumed for the backup paths. Our scheme thus includes a sophisticated resource aggregation mechanism based on the concepts of "backup-backup aggregation" and "backupprimary aggregation". The path selection algorithm is also designed to efficiently reduce the resource usage. Moreover, when considering LSPs at different preemption levels, our algorithm is able to correctly calculate the amount of bandwidth that can be preempted despite the sharing of resource. We show that our approach, though local, can compete with the state-of-theart end-to-end recovery schemes in terms of resource reservation. The major contribution of our scheme, the "backup-primary aggregation", was then also used in the context of end-to-end recovery and improved its performance substantially. [less ▲]

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See detailRouting in a MPLS network featuring preemption mechanisms
Blanchy, François; Mélon, Laurent; Leduc, Guy ULg

in 10th IEEE International Conference on Telecommunications (2003, February)

In the context of Multiprotocol Label Switching (MPLS), we propose an integration of a computationally efficient preemption mechanism into a very dynamic Label Switched Paths (LSPs) routing scheme ... [more ▼]

In the context of Multiprotocol Label Switching (MPLS), we propose an integration of a computationally efficient preemption mechanism into a very dynamic Label Switched Paths (LSPs) routing scheme described in a previous paper. This preemption scheme includes a quick heuristic able to select the most interesting LSPs to reroute from a link. The efficiency of this algorithm is obtained through a very rigid but seemingly appropriate policy concerning which LSPs are appropriate for preemption. A feedback from preemption on the routing process is proposed, in order to regulate the rate of the reroutings and to tune the balance between stability and continuous reorganization in a network. This integrated traffic engineering entity is tested on the accuracy of the heuristic, the relevance of the feedback and the whole integration, the influence of the routing policy on the preemption mechanism and the reliability of the managed network. [less ▲]

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See detailDeficiency of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) impairs nutritionally induced obesity in mice.
Lijnen, Roger; Demeulemeester, Diego; Van Hoef, B. et al

in Thrombosis and Haemostasis (2003), 89(2), 249-255

Tissue inhibitor of matrix metalloproteinase-1 deficient (TIMP-1(-/-)) mice and wild-type (TIMP-1(+/+)) controls were kept on a standard (SFD) or a high fat diet (HFD) for 15 weeks. At the time of ... [more ▼]

Tissue inhibitor of matrix metalloproteinase-1 deficient (TIMP-1(-/-)) mice and wild-type (TIMP-1(+/+)) controls were kept on a standard (SFD) or a high fat diet (HFD) for 15 weeks. At the time of sacrifice, TIMP-1(-/-) mice on HFD had a significantly lower body weight (29 +/- 1.5 versus 41 +/- 1.8 g, p <0.005), and significantly less subcutaneous (0.81 +/- 0.19 versus 1.78 +/- 0.21 g, p <0.05) and gonadal (0.87 +/- 0.17 versus 1.85 +/- 0.18 g, p <0.005) fat mass. These differences were much less pronounced for mice on SFD. On HFD but not on SFD, adipocyte diameters were significantly lower in the adipose tissue of TIMP-1(-/-) mice. Plasma leptin levels in TIMP-1(-/-) mice on HFD were significantly lower as compared to TIMP-1(+/-) mice, and strongly correlated with adipose tissue mass for both genotypes. Staining with an endothelial cell specific lectin revealed a significantly higher blood vessel density, larger stained area and vessel size in adipose tissue of TIMP-1(-/-) mice on HFD. This difference disappeared after normalization to the adipocyte number, suggesting that it does not represent a true enhancement of angiogenesis. Thus, in a murine model of nutritionally induced obesity, TIMP-1 promotes adipose tissue development. [less ▲]

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See detailA new proposal of a simple model for the lateral-torsional buckling of unrestrained steel I-beams in case of fire: experimental and numerical validation
Vila Real, Paolo; Piloto, Paolo; Franssen, Jean-Marc ULg

in Journal of Constructional Steel Research (2003), 59(2), 179-199

The behaviour of Steel I-Beams exhibiting lateral-torsional buckling at elevated temperature has been studied by means of experimental and numerical analysis. The authors in an earlier paper have ... [more ▼]

The behaviour of Steel I-Beams exhibiting lateral-torsional buckling at elevated temperature has been studied by means of experimental and numerical analysis. The authors in an earlier paper have presented an analytical formula for the buckling resistance moment in the fire design situation. This new proposal, different from the actual proposal of the Eurocode 3 Part 1.2 has been validated in this work by comparison with the results from a set of 120 experimental and numerical tests performed on IPE 100 beams, submitted to temperatures varying from room temperature to 600 degreesC. The numerical simulations have been based on the measured geometrical dimensions of the cross-sections, the longitudinal imperfections, i.e. the out of straightness of the beams, the residual stresses and the yield strength. The Eurocode simple model promotes ultimate loads that depend mainly on the non-dimensional slenderness of the beams. The analytical results provided by the Eurocode 3, for a certain range of the slenderness, appear to be unsafe when compared with the numerical and experimental results. It is shown that the new proposal is safer than the Eurocode 3 formulas. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailFamily size and optimal income taxation
Cremer, Helmuth; Dellis, Arnaud; Pestieau, Pierre ULg

in Journal of Population Economics (2003), 16(1), 37-54

This paper studies the role of family size in the design of optimal income taxation. We consider a second best setting where the government observes the number of children and the income of the parents ... [more ▼]

This paper studies the role of family size in the design of optimal income taxation. We consider a second best setting where the government observes the number of children and the income of the parents but not their productivity. With a linear tax schedule the marginal tax rate is shown to decrease with the number of children, while the relationship between the demogrant and family size appears to be ambiguous. With two ability levels, optimal non-linear income tax implies zero marginal tax rates for the higher ability parents; low ability parents have positive marginal tax rates that decrease with family size. [less ▲]

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See detailLine profile variability in the spectra of Oef stars. I. BD + 60deg 2522
Rauw, Grégor ULg; De Becker, Michaël ULg; Vreux, Jean-Marie ULg

in Astronomy and Astrophysics (2003), 399

We report the analysis of a long term observing campaign designed to monitor the spectroscopic variability of the Oef star BD +60deg 2522. We find that the double-peaked He {II} lambda 4686 emission line ... [more ▼]

We report the analysis of a long term observing campaign designed to monitor the spectroscopic variability of the Oef star BD +60deg 2522. We find that the double-peaked He {II} lambda 4686 emission line undergoes strong profile variability on time scales of 2-3 day. However, the time scale as well as the pattern of these variations turn out to be epoch dependent and the phenomenon is thus most likely not ruled by a single stable clock. On the other hand, the absorption lines in the spectrum of BD +60deg 2522 display line profile variability on time scales of a few hours that might be related to non-radial pulsations. We tentatively propose that the beating of several non-radial pulsation modes triggers transient large-scale density perturbations in a confined stellar wind that produce the 2-3 day time scale variability. [less ▲]

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See detailClient, Mon Cher Client !
Van Caillie, Didier ULg

Article for general public (2003)

This chronicle insists on the importance of the Customer Relationship Management in modern firms, even in the smallest ones, and insists on the ability of the firm to adequately value its relation with ... [more ▼]

This chronicle insists on the importance of the Customer Relationship Management in modern firms, even in the smallest ones, and insists on the ability of the firm to adequately value its relation with its main clients. [less ▲]

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See detailGuide Technique Parasismique Belge pour Maisons Individuelles
Plumier, André ULg; Doneux, Catherine; Caporaletti, Valeria et al

Book published by Département M&S de l'Université de Liège (2003)

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See detailLire ou ne pas lire : état de la question
Baye, Ariane ULg; Lafontaine, Dominique ULg; Vanhulle, Sabine

in Cahiers du Centre de Lecture publique de la Communauté française (2003), 4

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See detailTraitement hormonal apres cancer du sein. Oui ... ou non?
Foidart, Jean-Michel ULg; Desreux, Joëlle ULg; Lifrange, Eric ULg et al

in Revue Médicale de Liège (2003), 58(2), 77-82

Clinical and experimental studies indicate that combined unique conjugated estrogens and medroxyprogesterone acetate moderately increase the risk of breast cancer in postmenopausal women. Classically ... [more ▼]

Clinical and experimental studies indicate that combined unique conjugated estrogens and medroxyprogesterone acetate moderately increase the risk of breast cancer in postmenopausal women. Classically, hormone replacement therapy is contra-indicated in women with a past history of breast cancer due to the fear of recurrence. However, these postmenopausal patients complain about hot flushes and adjuvant hormonal therapies (such as aromatase inhibitors, SERMs and Tamoxifen...) aggravate their symptoms. Observational studies and their meta-analyses do not show a deleterious effect but rather a beneficial impact of hormone replacement therapy among women with a past history of breast cancer. We summarise all these studies and their biological, clinical and epidemiological interpretations. We conclude that short term hormone replacement therapy is safe among those women requesting a replacement therapy after complete information. It is however advisable to conclude definitely only when prospective randomised trials with estradiol or tibolone (a promising alternative) will be available. Such ongoing studies will allow to conclude definitely the possible benefits and risks of hormone replacement therapy among patients with a past history of breast cancer. [less ▲]

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See detailMorphological study of magnesium hydroxide nanoparticles precipitated in dilute aqueous solution
Henrist, Catherine ULg; Mathieu, J. P.; Vogels, C. et al

in Journal of Crystal Growth (2003), 249(1-2), 321-330

Among other applications, magnesium hydroxide is commonly used as a flame-retardant filler in composite materials, as well as a precursor for magnesium oxide refractory ceramic. The microstructure of the ... [more ▼]

Among other applications, magnesium hydroxide is commonly used as a flame-retardant filler in composite materials, as well as a precursor for magnesium oxide refractory ceramic. The microstructure of the powder is of prime importance in both technical applications. The influence of synthesis parameters on the morphological characteristics of magnesium hydroxide nanoparticles precipitated in dilute aqueous medium was studied. Several parameters were envisaged such as chemical nature of the base precipitant, type of counter-ion, temperature and hydrothermal treatment. Special attention was given to the obtaining of platelet-shaped, nanometric and de-agglomerated powders. The powders were characterized in terms of particle size distribution, crystal habits, morphology and ability to be redispersed in water. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption and laser diffusion analyses were used for this purpose. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailRegulation of training system for adults in educational technology
Denis, Brigitte ULg; Piette, Sylvie-Anne

in Stacey, E.; Davies, E. (Eds.) Quality education @ a distance (2003, February)

This paper reports the characteristics of a post graduate diploma on educational technologies based on a combination of face-to-face and distance activities and assesses its quality. We first define the ... [more ▼]

This paper reports the characteristics of a post graduate diploma on educational technologies based on a combination of face-to-face and distance activities and assesses its quality. We first define the bases of the training program and present several tools (logbook, portfolio and questionnaires) which have been used to evaluate and regulate both training and individual learning process. Our observations indicate an increase and better regulation of the quality of the educational and learning processes. On the basis of the results we achieved, we propose that our original design could be extended to similar adult training programs. The way this innovative system is integrated in the universities shows an evolution due to its success that implies a certain kind of return on investment due to the demand of such kinds of device. [less ▲]

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See detailLa notion de réseau en sciences sociales
Claisse, Frédéric ULg

Scientific conference (2003, January 22)

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