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See detailPotential of space-based infrared Bracewell interferometers for planet detection
Defrere, Denis ULg; Absil, Olivier ULg; Hanot, Charles ULg et al

in Coulter, D. (Ed.) Techniques and Instrumentation for Detection of Exoplanets III (2007, September 12)

The Darwin and TPF-I space missions will be able to study the atmosphere of distant worlds similar to the Earth. Flying these space-based interferometers will however be an extraordinary technological ... [more ▼]

The Darwin and TPF-I space missions will be able to study the atmosphere of distant worlds similar to the Earth. Flying these space-based interferometers will however be an extraordinary technological challenge and a first step could be taken by a smaller mission. Several proposals have already been made in this context, using the simplest nulling scheme composed of two collectors, i.e., the original Bracewell interferometer. Two of these projects, viz. Pegase and the Fourier-Kelvin Space Interferometer, show very good perspectives for the characterisation of hot extra-solar giant planets (i.e., Jupiter-size planets orbiting close to their parent star). In this paper, we build on these concepts and try to optimise a Bracewell interferometer for the detection of Earth-like planets. The major challenge is to efficiently subtract the emission of the exo-zodiacal cloud which cannot be suppressed by classical phase chopping techniques as in the case of multi-telescopes nulling interferometers. We investigate the potential performance of split-pupil configurations with phase chopping and of OPD modulation techniques, which are good candidates for such a mitigation. Finally, we give a general overview of the performance to be expected from space-based Bracewell interferometers for the detection of extra-solar planets. In particular, the prospects for known extra-solar planets are presented. [less ▲]

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See detailEtude des principales maladies du système locomoteur chez le veau de race Blanc-Bleu Belge
Sartelet, Arnaud ULg

Master of advanced studies dissertation (2007)

The mortality rate due to musculoskeletal diseases in calves is 9 % of the overall mortality rate. It may then have major consequences on the future of the animal and on breeder’s economics. The most ... [more ▼]

The mortality rate due to musculoskeletal diseases in calves is 9 % of the overall mortality rate. It may then have major consequences on the future of the animal and on breeder’s economics. The most common musculoskeletal diseases are septic arthritis, congenital articular rigidity, fractures and spastic paresis. Two clinical studies were performed on 295 and 40 Belgian Blue calves. The first one reported a 72.3 % success rate in surgical treatments of septic arthritis. The 83.9 % rate of posterior presentation and the 90 % rate of males confirmed the hypothesis of hypomobility of calves affected by congenital articular rigidity. The success rate after appropriate treatment was 82.8 %. This study also confirmed the predisposition of Belgian Blue calves to tibial fractures (52 %). The success rate of fractures in calves was 74.1 %. An alternative to treatment in case of quadriceps or combined spastic paresis is fattening. Seventy height percent of affected calves have indeed been fattened with an almost normal growth rate. This alternative remains economically advantageous. The second study developed a classification of gastrocnemius spastic paresis based on general examination, special examination and postoperative results. This classification demonstrates the progressive nature of this disease and its consequences on body condition, allowing a more accurate diagnosis and prognosis. The success rate after partial tibial nevrectomy for grade II, III and IV was respectively 100 %, 72.7 % and 42.9 %. Those 2 studies demonstrate the effectiveness of accurate diagnosis and prognosis associated with an appropriate treatment to offer a better output to breeders despite the presence of these diseases. [less ▲]

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See detailLes images anachroniques de l'histoire de l'univers
Dondero, Maria Giulia ULg

in Espressione/Contenuto : Rivista dell’Associazione Italiana di Studi Semiotici (2007)

Cet article étudie les techniques de détection utilisées par l’astrophysique permettant la formulation d’hypothèses sur la vie et les parcours des astres (extinction, explosion, etc.). Le corpus se ... [more ▼]

Cet article étudie les techniques de détection utilisées par l’astrophysique permettant la formulation d’hypothèses sur la vie et les parcours des astres (extinction, explosion, etc.). Le corpus se constitue d’images tirées du dernier livre du célèbre astrophysicien Jean-Pierre Luminet "Le destin de l’Univers. Trous noirs et énergie sombre". Cet ouvrage de vulgarisation savante montre que ce sont les rapports entre images prises selon différentes longueurs d’onde (radio, infrarouge, spectre visible, ultraviolet, rayons X, gamma) et à différents moments qui permettent de visualiser des données, de les manipuler, de dater les phénomènes, de confirmer des hypothèses et de relancer l’investigation. Ce travail montre que les images en astrophysique sont des mosaïques construites à partir de mesures effectuées à travers une longue série de réglages des paramètres (température, composition chimique, vitesse de rotation, etc.) dont les couleurs surtout rendent compte. On y distingue les différentes fonctions des images à partir des processus qu’elles entendent détecter, mesurer, visualiser, imaginer à partir de la « densité » des agencements entre elles. On s’y enquête aussi sur des images à statut « artistique » qui sont contenue dans l’ouvrage de Luminet et on fait des hypothèses sur le rôle qu’elles jouent dans l’état d’acquisitions théoriques et de recherches en cours sur les trous noirs et d’autres phénomènes encore méconnus par la discipline. [less ▲]

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See detailEtude du rôle des bactéries symbiotiques de pucerons dans l'adaptation aux plantes hôtes
Yattara, Almouner Ag Alhamis ULg

Master of advanced studies dissertation (2007)

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See detailMacromolecular engineering of cyclic aliphatic polyesters by ring-opening polymerization and "click" chemistry
Lecomte, Philippe ULg; Li, Haiying; Riva, Raphaël ULg et al

Conference (2007, September 04)

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the ... [more ▼]

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the absence of any chain-end and exhibit distinct properties from their linear counterparts, such as glass transition temperature, order-disorder transition, reduced viscosity, lower hydrodynamic volumes. This communication aims at reporting on a novel route to biodegradable cyclic polyesters. Our strategy is based on the work of Prof. Kricheldorf who initiated the ring-opening polymerization of ε-caprolactone by cyclic tin dialkoxides, e.g., 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) in order to obtain “living” macrocyclic PCL, still containing two endocyclic tin-oxygen bonds. In this work, the resumption of polymerization by a few units of ε-caprolactone substituted by an acrylic unit, e.g., 1-(2-oxooxepan-3-yl)ethyl prop- 2-enoate, followed by intramolecular photo-crosslinking of pendant unsaturations and finally by hydrolysis gave rise to macrocyclic PCL. As a rule, this strategy is very well-suited for the synthesis of high molecular weight PCL. Moreover, tin alkoxides were kept untouched after the cross-linking step and remained thus available for further macromolecular engineering. The process was extended to the synthesis of other architectures such as sun-shaped, two-tail tadpoleshaped, and eight-shaped copolyesters. The second part of the lecture, it will be shown that the copper(I)-catalyzed Huisgen’s [3+2] cycloaddition, which is the most popular “Click" reaction, is very efficient to graft alkynes, duly substituted by functional groups or chains, onto aliphatic copolyesters bearing pendant azides. Interestingly enough, mild conditions were found and no degradation was observed during the “click” derivatization of copolyesters of PCL. The “click” reactions of alkynes onto pendant azides of copolyesters of PLA, by far more sensitive than PCL, was also successfully carried out without any detectable degradation. ”Click” chemistry is very versatile because this reaction was successfully implemented to graft functional groups or chains directly onto ω-azido-ε-caprolactone, without any ring-opening of the lactone, in order to make available a new range of functional caprolactones. Finally, the “click” grafting of PEO onto the tails of tadpole-shaped copolymers will be shown to be a route to amphiphilic copolymers with an original architecture. [less ▲]

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See detailA Patient with Hiv Infection, Cough, Asthenia, and Fever
Mayasi, N.; Chandrikakumari, Kavitha; Mukeba, D. et al

in Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America (2007), 45(5), 662-3559-600

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See detailThe annular groove phase mask coronagraph: an achromatic optical vortex
Mawet, D.; Riaud, Pierre ULg; Hanot, Charles ULg et al

in Coulter, Daniel R (Ed.) "Techniques and Instrumentation for Detection of Exoplanets III" Proceedings of the SPIE, Volume 6693, Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

The Annular Groove Phase Mask coronagraph (AGPM) is an intrinsically achromatic vectorial vortex. It consists of integrated subwavelength optical elements whose space-variant polarization properties can ... [more ▼]

The Annular Groove Phase Mask coronagraph (AGPM) is an intrinsically achromatic vectorial vortex. It consists of integrated subwavelength optical elements whose space-variant polarization properties can be engineered and optimized to synthesize one of the theoretically most efficient coronagraphs. This paper briefly recalls the principles of the AGPM, presents the benefit of its implementation inside a polarimetric differential imager, realistic numerical simulations assessing its performances, as well as the current status of the near-infrared and visible prototype manufacturing operations. [less ▲]

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See detailFresnel rhombs as achromatic phase shifters for infrared nulling interferometry: first experimental results
Hanot, Charles ULg; Mawet, D.; Loicq, Jerôme ULg et al

in Coulter, Daniel R (Ed.) "Techniques and Instrumentation for Detection of Exoplanets III" Proceedings of the SPIE, Volume 6693, Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

One of the most critical units of nulling interferometers is the Achromatic Phase Shifter. The concept we propose here is based on optimized Fresnel rhombs, using the total internal reflection phenomenon ... [more ▼]

One of the most critical units of nulling interferometers is the Achromatic Phase Shifter. The concept we propose here is based on optimized Fresnel rhombs, using the total internal reflection phenomenon, modulated or not. The total internal reflection induces a phase shift between the polarization components of the incident light. We present the principles, the current status of the prototype manufacturing and testing operations, as well as preliminary experiments on a ZnSe Fresnel rhomb in the visible that have led to a first error source assessment study. Thanks to these first experimental results using a simple polarimeter arrangement, we have identified the bulk scattering as being the main error source. Fortunately, we have experimentally verified that the scattering can be mitigated using spatial filters and does not decrease the phase shifting capabilities of the ZnSe Fresnel rhomb. [less ▲]

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See detailSWAP: a novel EUV telescope for space weather
Defise, Jean-Marc ULg; Halain, Jean-Philippe ULg; Berghmans, David et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be part of the PROBA2 payload, an ESA technological mission to be launched in early 2008 ... [more ▼]

The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be part of the PROBA2 payload, an ESA technological mission to be launched in early 2008. SWAP is directly derived from the concept of the EIT telescope that we developed in the '90s for the SOHO mission. Several major innovations have been introduced in the design of the instrument in order to be compliant with the requirements of the PROBA2 mini-satellite: compactness with a new of-axis optical design, radiation resistance with a new CMOS-APS detector, a very low power electronics, an athermal opto-mechanical system, optimized onboard compression schemes combined with prioritization of collected data, autonomy with automatic triggering of observation and off-pointing procedures in case of Solar event occurrence, ... All these new features result from the low resource requirements (power, mass, telemetry) of the mini-satellite, but also take advantage of the specificities of a modern technological platform, such as quick pointing agility, new powerful on-board processor, Packetwire interface and autonomous operations. These new enhancements will greatly improve the operations of SWAP as a space weather sentinel from a low Earth orbit while the downlink capabilities are limited. This paper summarizes the conceptual design, the development and the qualification of the instrument, the autonomous operations and the expected performances for science exploitation. [less ▲]

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See detailSTEREO: Heliospheric Imager design, pre-flight, and in-flight response comparison
Halain, Jean-Philippe ULg; Mazy, Emmanuel ULg; Defise, Jean-Marc ULg et al

in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series (2007, September 01)

The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO observatories launched in October 2006. The two HI instruments provide stereographic image pairs of solar ... [more ▼]

The Heliospheric Imager (HI) is part of the SECCHI suite of instruments on-board the two STEREO observatories launched in October 2006. The two HI instruments provide stereographic image pairs of solar coronal plasma and coronal mass ejections (CME) over a field of view ranging from 13 to 330 R[SUB]0[/SUB]. The HI instrument is a combination of two refractive optical systems with a two stage multi-vane baffle system. The key challenge of the instrument design is the rejection of the solar disk light by the front baffle, with total straylight attenuation at the detector level of the order of 10[SUP]-13[/SUP] to 10[SUP]-15[/SUP]. Optical systems and baffles were designed and tested to reach the required rejection. This paper presents the pre-flight optical tests performed under vacuum on the two HI flight models in flight temperature conditions. These tests included an end-to-end straylight verification of the front baffle efficiency, a co-alignment and an optical calibration of the optical systems. A comparison of the theoretical predictions of the instrument response and performance with the calibration results is presented. The instrument in-flight photometric and stray light performance are also presented and compared with the expected results. [less ▲]

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See detailDetection of transits of the nearby hot Neptune GJ 436 b
Gillon, Michaël ULg; Pont, F.; Demory, B*-O et al

in Astronomy and Astrophysics (2007), 472

This Letter reports on the photometric detection of transits of the Neptune-mass planet orbiting the nearby M-dwarf star GJ 436. It is by far the closest, smallest, and least massive transiting planet ... [more ▼]

This Letter reports on the photometric detection of transits of the Neptune-mass planet orbiting the nearby M-dwarf star GJ 436. It is by far the closest, smallest, and least massive transiting planet detected so far. Its mass is slightly larger than Neptune's at M = 22.6 ± 1.9 M_â . The shape and depth of the transit lightcurves show that it is crossing the host star disc near its limb (impact parameter 0.84 ± 0.03) and that the planet size is comparable to that of Uranus and Neptune, R = 25 200 ± 2200 km = 3.95 ± 0.35 R_â . Its main constituant is therefore very likely to be water ice. If the current planet structure models are correct, an outer layer of H/He constituting up to ten percent in mass is probably needed on top of the ice to account for the observed radius. [less ▲]

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See detailAccurate Spitzer infrared radius measurement for the hot Neptune GJ 436b
Gillon, Michaël ULg; Demory, B*-O; Barman, T. et al

in Astronomy and Astrophysics (2007), 471

We present Spitzer Space Telescope infrared photometry of a primary transit of the hot Neptune GJ 436b. The observations were obtained using the 8 mum band of the InfraRed Array Camera (IRAC). The high ... [more ▼]

We present Spitzer Space Telescope infrared photometry of a primary transit of the hot Neptune GJ 436b. The observations were obtained using the 8 mum band of the InfraRed Array Camera (IRAC). The high accuracy of the transit data and the weak limb-darkening in the 8 mum IRAC band allow us to derive (assuming M = 0.44 ± 0.04 M_o for the primary) a precise value for the planetary radius (4.19[SUP]+0.21[/SUP][SUB]-0.16[/SUB] R_â ), the stellar radius (0.463[SUP]+0.022[/SUP][SUB]-0.017[/SUB] R_o), the orbital inclination (85.90°[SUP]+0.19°[/SUP][SUB]-0.18°[/SUB]) and transit timing (2454280.78186[SUP]+0.00015[/SUP][SUB]-0.00008[/SUB] HJD). Assuming current planet models, an internal structure similar to that of Neptune with a small H/He envelope is necessary to account for the measured radius of GJ 436b. The photometric data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/471/L51 [less ▲]

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See detailL'astronomie dans le monde
Manfroid, Jean ULg

Article for general public (2007)

Anions interstellaires; S Orionis; Altaïr; Courants stellaires; Etoiles jeunes; 2MASSW J1207334-393254; Alpha Andromède; Etoiles à neutrons (1); LH54-425; AGNs invisibles; Deux supernovae; Les GRBs selon ... [more ▼]

Anions interstellaires; S Orionis; Altaïr; Courants stellaires; Etoiles jeunes; 2MASSW J1207334-393254; Alpha Andromède; Etoiles à neutrons (1); LH54-425; AGNs invisibles; Deux supernovae; Les GRBs selon Swift; Peser les trous noirs; Formation de trous noirs; Trou noir; ondes gravitationnelles : Virgo entre dans sa phase d'exploitation scientifique; Amas de galaxies actifs; Amas de galaxies; Galaxies actives d'amas; L'univers statique: le retour; Macho; Exoplanètes; Exoplanètes habitables?; Exoplanètes habitables? (suite); Une année d'un an; Une année de 31 heures; Valse des Jupiters; Disque de HD 15115; Impact majeur; Planètes isolées; Super-Jupiter; Impact et mini-extinction; L'effet Pioneer; Toungouska; Spéléo martienne; Autres lunes actives; Encelade; Hypérion; Pluton dépassé; Satellites d'Uranus; Titan [less ▲]

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See detailFresnel rhombs as achromatic phase shifters for infrared nulling interferometry
Mawet, D.; Hanot, Charles ULg; Lenaers, C. et al

in Optics Express (2007), 15

We propose a new family of achromatic phase shifters for infrared nulling interferometry. These key optical components can be seen as optimized Fresnel rhombs, using the total internal reflection ... [more ▼]

We propose a new family of achromatic phase shifters for infrared nulling interferometry. These key optical components can be seen as optimized Fresnel rhombs, using the total internal reflection phenomenon, modulated or not. The total internal reflection indeed comes with a phase shift between the polarization components of the incident light. We propose a solution to implement this vectorial phase shift between interferometer arms to provide the destructive interference process needed to disentangle highly contrasted objects from one another. We also show that, modulating the index transition at the total internal reflection interface allows compensating for the intrinsic material dispersion in order to make the subsequent phase shift achromatic over especially broad bands. The modulation can be induced by a thin film of a well-chosen material or a subwavelength grating whose structural parameters are thoroughly optimized. We present results from theoretical simulations! together with preliminary fabrication outcomes and measurements for a prototype in Zinc Selenide. [less ▲]

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See detailCircular Polarimetry Now Offered at EFOSC2
Saviane, Ivo; Piirola, Vilppu; Bagnulo, Stefano et al

in The Messenger (2007), 129

Starting from period P79, circular polarimetry measurements can be carried out with EFOSC2 at the ESO 3.6-m telescope. Here we describe the motivations behind the upgrade of the instrument, and a few ... [more ▼]

Starting from period P79, circular polarimetry measurements can be carried out with EFOSC2 at the ESO 3.6-m telescope. Here we describe the motivations behind the upgrade of the instrument, and a few results from the commissioning runs are used to show the excellent performance of the new polarimetry unit. [less ▲]

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See detailEfficient and Resilient Overlay Topologies over Ad Hoc Networks
Calomme, Sandrine; Leduc, Guy ULg

in Lecture Notes in Computer Science (2007, September), 4725

We discuss what kind of overlay topology should be pro-actively built before an overlay routing protocol enters a route search process on top of it. The basic overlay structures we study are the K-Nearest ... [more ▼]

We discuss what kind of overlay topology should be pro-actively built before an overlay routing protocol enters a route search process on top of it. The basic overlay structures we study are the K-Nearest Neighbours overlay topologies, connecting every overlay node to its K nearest peers. We introduce a family of optimizations, based on a pruning rule. As flooding is a key component of many route discovery mechanisms in MANETs, our performance study focusses on the delivery percentage, bandwidth consumption and time duration of flooding on the overlay. We also consider the overlay path stretch and the overlay nodes degree as respective indicators for the data transfer transmission time and overlay resilience. We finally recommend to optimize the K-Nearest Neighbours overlay topologies with the most selective pruning rule and, if necessary, to set a minimal bound on the overlay node degree for improving resilience. [less ▲]

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See detailUna metodología Interdisciplinaria para la puesta en turismo de un área natural protegida y habitada.
Escobar Jimenez, Kelly ULg

in Anuario Turismo Sociedad (2007, September), VIII

Este artículo intenta mostrar algunas pautas importantes a nivel teórico, metodológico y práctico del estudio diagnostico para la puesta en turismo de la Vía Parque Isla de Salamanca (VIPIS) Se pretende ... [more ▼]

Este artículo intenta mostrar algunas pautas importantes a nivel teórico, metodológico y práctico del estudio diagnostico para la puesta en turismo de la Vía Parque Isla de Salamanca (VIPIS) Se pretende en el presente artículo, primero, mostrar algunas pautas de la investigación interdisciplinaria para la puesta en turismo de un espacio habitado de alto valor ecológico (EHAVE), luego esbozar algunas consideraciones teóricas para el análisis de la participación comunitaria dentro de los proyectos de desarrollo turístico y por último intentamos trazar una reflexión sobre la aplicación de estos elementos teóricos y metodológicos en el estudio diagnóstico de la puesta en turismo de la VIPIS. En la VIPIS se ha utilizado el ecosistema de manglar como un puente entre los diferentes actores del parque natural y como un vínculo entre las diferentes disciplinas involucradas en el proyecto de investigación –economía, antropología, biología, arquitectura y turismo-. Todo esto con la intensión de hacer un estudio interdisciplinario para proponer alternativas de desarrollo respetuosas con las comunidades locales y el medio ambiente de la región. [less ▲]

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See detailUrbanisme durable (rapport final)
Boniver, Véronique ULg; Denis, Olivier; Dopagne, Claude ULg et al

Report (2007)

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