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See detailExozodiacal discs with infrared interferometry
Absil, Olivier ULg

Scientific conference (2007, March 05)

The detection of the warm inner part of debris discs---the extrasolar counterparts of the zodiacal cloud---is of prime importance to characterise the global architecture of planetary systems. Because of ... [more ▼]

The detection of the warm inner part of debris discs---the extrasolar counterparts of the zodiacal cloud---is of prime importance to characterise the global architecture of planetary systems. Because of the high contrast and small angular separation between the star and the exozodiacal light, high-precision infrared interferometry is the best-suited tool to carry out such observations. In this paper, we review the first detection of an exozodiacal disc by this method recently reported around Vega by Absil et al. (2006), and discuss the currently on-going observing efforts in this domain. We show how interferometric data can give access to the composition and the dynamics (including LHB-like events) of extrasolar planetary systems, and thereby put useful constraints on the presence of small bodies and/or giant planets. This statement is illustrated with new data obtained on various bright Vega-type stars, including Vega itself. Finally, we show how the new generation of interferometric instruments will change our view of debris discs: with their increased sensitivity and imaging capabilities, they will constrain the morphology of bright exozodiacal discs and push the detection limit towards meaningful density levels in the context of future life-finding missions such as Darwin/TPF. [less ▲]

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See detailExozodiacal Disks
Hinz, Phillip; Millan-Gabet, Rafael; Absil, Olivier ULg

in Lawson, P. R.; Traub, W. A.; Unwin, S. C. (Eds.) Exoplanet Community Report (2009)

From the viewpoint of direct imaging of exoplanets in the visible or infrared, exozodi dust disks can be both good and bad. An exozodi disk is good if it has structures (cleared regions or resonant clumps ... [more ▼]

From the viewpoint of direct imaging of exoplanets in the visible or infrared, exozodi dust disks can be both good and bad. An exozodi disk is good if it has structures (cleared regions or resonant clumps) that suggest the gravitational presence of planets, however it is bad if the dust fills the instrumental field of view with brightness that swamps the signal from a planet. Unfortunately, it takes very little dust to compete with or overwhelm the light from a planet: an Earth‐twin signal is roughly equal to a 0.1‐AU patch of Solar‐System‐twin zodi, in the visible or infrared. Thus, exozodi measurements are extremely important, but they are also difficult to make. Current limits of detection, in units of the Solar‐System brightness, are a few hundred using the Spitzer Space Telescope, about one hundred with the Keck Interferometer (KI), and about 10 expected from the Large Binocular Telescope Interferometer (LBTI). A small coronagraph or small interferometer in space is needed in order to reach the sensitivity required to detect the glow at the level of our own Solar System. [less ▲]

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See detailThe Exozodiacal Dust Problem for Direct Observations of Exo-Earths
Roberge, Aki; Chen, Christine H; Millan-Gabet, Rafael et al

in Publications of the Astronomical Society of the Pacific [=PASP] (2012), 124

Debris dust in the habitable zones of stars - otherwise known as exozodiacal dust - comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the ... [more ▼]

Debris dust in the habitable zones of stars - otherwise known as exozodiacal dust - comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the Solar System's zodiacal dust and the exozodiacal dust in the target system is likely to be the largest source of astrophysical noise in direct observations of terrestrial planets in the habitable zones of nearby stars. Furthermore, dust structures like clumps, thought to be produced by dynamical interactions with exoplanets, are a possible source of confusion. In this paper, we qualitatively assess the primary impact of exozodical dust on high-contrast direct imaging at optical wavelengths, such as would be performed with a coronagraph. Then we present the sensitivity of previous, current, and near-term facilities to thermal emission from debris dust at all distances from nearby solar-type stars, as well as our current knowledge of dust levels from recent surveys. Finally, we address the other method of detecting debris dust, through high-contrast imaging in scattered light. This method is currently far less sensitive than thermal emission observations, but provides high spatial resolution for studying dust structures. This paper represents the first report of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG). [less ▲]

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See detailExpanding on olfactory communication in a butterfly: cuticular chemicals indicate sex and age in Bicyclus anynana
Heuskin, Stéphanie ULg; Kaltenpoth, M.; Engl, T. et al

in International Society of Chemical Ecology, 28th Annual Meeting. Abstracts (2012, July)

Chemical (olfactory or gustatory) communication is fundamental to most living organisms but widely understudied compared to other channels of communication such as vision and audition, principally in ... [more ▼]

Chemical (olfactory or gustatory) communication is fundamental to most living organisms but widely understudied compared to other channels of communication such as vision and audition, principally in sexual selection . Here we present the first extensive analysis of cuticular chemical diversity in a butterfly, and investigate whether molecules inform potential mating partners about sex and age. Bicyclus anynana was chosen for its well-known potentialities as a lab model in eco-evo-devo studies , . Chemical interactions have been investigated so far in this species with focus on volatile olfactory components: male sexual pheromones composition and their roles in sexual selection , , their change in ratio with male age, inbreeding coefficient, and other factors . Here we aim completing the picture fully and focus on gustatory non-volatile cuticular chemical diversity in this model species. Indeed, as for Drosophila, the courtship of this butterfly is composed of a series of steps that include short-range interactions during which various chemicals may be involved in mate-choice, through olfactory but also gustatory channels of communication (Nieberding et al., data not published). More than hundred cuticular chemicals were identified and quantified by GC-MS analyses on different parts (abdomen, antennae, head, legs and wings) of B. anynana individuals (n=42, 210 GC-MS analyses) of each sex and at different ages (from 1 to 21 days old). The analysis of the chemical distribution was realised by multivariate statistical analyses (perMANOVA). The results led to the conclusion that some cuticular chemicals are indicative for the body parts and can inform about sex and age. [less ▲]

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See detailExpanding the CHARA/FLUOR hot disk survey
Mennesson, B.; Scott, N.; Ten Brummelaar, T. et al

in Journal of Astronomical Instrumentation (2013), 2(2), 1340010

Little is presently known about the hot (>300 K) dust component of debris disks surrounding main sequence stars, similar to the zodiacal dust cloud found in the inner solar system.While extensive surveys ... [more ▼]

Little is presently known about the hot (>300 K) dust component of debris disks surrounding main sequence stars, similar to the zodiacal dust cloud found in the inner solar system.While extensive surveys have been carried out from space, the majority of detections have surprisingly come from the ground, where near infrared interferometric observations have recently revealed small (∼1%) resolved excesses around a dozen nearby main sequence stars. Most of these results have come from the CHARA array “FLUOR” instrument (Mt. Wilson, CA), which has demonstrated the best sensitivity worldwide so far for this type of studies, and has carried out an initial survey of ∼40 stars. In order to further understand the origin of this “hot dust phenomenon”, we will extend this initial survey to a larger number of stars and lower excess detection limits, i.e. higher visibility accuracy providing higher contrast measurements. To this end, two major instrumental developments are underway at CHARA. The first one aims at improving FLUOR’s sensitivity to a median K-band magnitude limit of 5 (making 200 targets available). The second development is based on a method that we recently developed for accurate (better than 0.1%) null depth measurements of stars, and that can be extended to regular interferometric visibility measurements. [less ▲]

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See detailExpanding the scope of controlled radical polymerization via cobalt–tellurium radical exchange reaction
Kermagoret, Anthony ULg; Nakamura, Yasuyuki; Bourguignon, Maxime et al

in ACS Macro Letters (2014), 3(1), 114-118

Cobalt-mediated radical polymerization (CMRP) and tellurium-mediated radical polymerization (TERP) were combined for the first time, offering new perspectives in the precision design of macromolecular ... [more ▼]

Cobalt-mediated radical polymerization (CMRP) and tellurium-mediated radical polymerization (TERP) were combined for the first time, offering new perspectives in the precision design of macromolecular structures. In particular, the present work highlights the benefits of this strategy for the synthesis of novel poly(vinyl acetate)-based block copolymers. A range of well-defined poly(vinyl acetate)s (PVAc) were first produced via CMRP using the bis(acetylacetonato)cobalt(II) complex (Co(acac)2) as a regulating agent. Substitution of a methyltellanyl moiety for Co(acac)2 at the ω-chain end of the precursor was then achieved upon treatment with dimethylditelluride. In contrast to the PVAc prepared by TERP, the ones produced by sequential CMRP and Co/Te exchange reaction almost exclusively consist of regular head-to-tail-TeMe chain-end species that can be activated by TERP. Ultimately, a series of monomers problematic in Co(acac)2-mediated radical polymerization including N-isopropylacrylamide (NIPAM), 2-(dimethylamino)ethyl acrylate (ADAME), n-butyl acrylate (BA), isoprene (IP), and vinylimidazole (NVIm) were polymerized by TERP from the PVAc–TeMe macroinitiators leading to novel diblock copolymers that cannot be made by each technique used separately. [less ▲]

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See detailExpanding the value of your practice with dental implants.
Van Heusden, Alain ULg

Conference (2006)

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See detailAn expanding Universe without dark matter and dark energy
Magain, Pierre ULg

E-print/Working paper (2012)

Assuming that observers located inside the Universe measure a time flow which is different from the time appearing in the Friedmann-Lemaıtre equation, and determining this time flow such that the Universe ... [more ▼]

Assuming that observers located inside the Universe measure a time flow which is different from the time appearing in the Friedmann-Lemaıtre equation, and determining this time flow such that the Universe always appears flat to these observers, we derive a simple cosmological model which allows to explain the velocity dispersions of galaxies in galaxy clusters without introducing dark matter. It also solves the horizon problem without recourse to inflation. Moreover, it explains the present acceleration of the expansion without any resort to dark energy and provides a good fit to the observations of distant supernovæ. Depending on the present value of the matter-energy density, we calculate an age of the Universe between 15.4 and 16.5 billion years, ignificantly larger than the 13.7 billion years of the standard CDM model. Our model has a slower expansion rate in the early epochs, thus leaving more time for the formation of structures such as stars and galaxies. [less ▲]

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See detailExpansion et régression: deux mots clés de la dynamique des populations du martin pêcheur (Alcedo atthis)
Libois, Roland ULg; Hallet, Catherine

in Aves (1989), 26(n° spécial "Actes...."), 93-101

Annual censuses of nest kingfishers are performed since 1973 in the valley of the river Lesse, a tributary of the river Meuse (Belgium). The authors document sharp population fluctuations. It appears that ... [more ▼]

Annual censuses of nest kingfishers are performed since 1973 in the valley of the river Lesse, a tributary of the river Meuse (Belgium). The authors document sharp population fluctuations. It appears that these are mainly due to the weather conditions prevailing at key-periods. Hard winters reduce the numbers, sometimes to a low level, whereas heavy late-spring or early- summer rains involve a bad reproduiction rate (namely through clutch losses following flooding). Hence, the recovery of the nesting population is weakened. In comparison, other factors such as predation, seem to have only a limitid effect. In other respects, the noxious consequences of permanent disturbances are illistrated in the that part of river Lesse where kayak is practised on a large commercial scale. [less ▲]

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See detailExpansion Machine and fluid selection for the Organic Rankine Cycle
Quoilin, Sylvain ULg; Declaye, Sébastien ULg; Lemort, Vincent ULg

in Proceedings of the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (2010, July)

This paper considers a whole range of ORC applications, in terms of power (from the kW-scale to the multi-MW plants), heat source temperature (from 90°C to more than 300°C) or heat source nature (solar ... [more ▼]

This paper considers a whole range of ORC applications, in terms of power (from the kW-scale to the multi-MW plants), heat source temperature (from 90°C to more than 300°C) or heat source nature (solar, biomass, waste heat recovery, geothermy, etc.). Five typical ORC applications are considered in terms of evaporating and condensing temperature. A screening of the most used ORC working fluids is performed, and their thermodynamics performances are compared with respect to the foreseen application. A detailed analysis of the most common expansion machines is then conducted, by comparing their respective operating maps for each fluid and for each application type. The considered expansion machines are the single-stage radial-inflow turbine, the screw expander, and the scroll expander, which are widely used in commercial applications and/or in scientific literature. The limitations of these machines are listed and considered to define an operating map for each considered fluid. Finally, the allowable power range is described with respect to the application and to the selected expansion device. [less ▲]

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See detailExpansion of CD16+ CD56+ NK cells in vericyte® NK cell growth medium
Brohée, Laura ULg; Bastin, Renaud ULg; Wingert, S et al

Poster (2013)

Natural Killer (NK) cells play a key role in host resistance to virus and tumour. These cells are potent killers of virus infected and tumour cells via a direct recognition of the target by activation ... [more ▼]

Natural Killer (NK) cells play a key role in host resistance to virus and tumour. These cells are potent killers of virus infected and tumour cells via a direct recognition of the target by activation receptor such as NKG2D or by inducing Fcγ receptor (FcγRIII, CD16) mediated antibody dependent cellular cytotoxicity (ADCC). Current NK cell-based cancer immunotherapy aims to produce large amounts of functional NK cells, unfortunately most culture media used for NK cell expansion induced the downregulation of CD16 on NK cells. Here, we tested the impact of a new NK cell growth medium (Vericyte® from Medicyte) on CD16 expression. Sorted NK cells and peripheral blood mononuclear cells (PBMC) were cultivated in vericyte® NK cell growth medium and cells issued from these cultures were characterized in term of expansion and phenotype at several time points. After 5 days of culture, an expansion of both NK cells and PBMC was observed and maintained at least until day 20 of culture. In PBMC cultures, we observe only a small preferential NK cell growth since NK cells were around 5-10% at beginning of the culture and this percentage increased to 15% at the end of the culture. However, these cells showed a high proliferative potential when we started the culture with sorted NK cells (the proportion of contaminant cells remain low, under 5%). NK cells expressed CD56 and NKp46 and interestingly after a decreased expression of CD16 on the cell surface at day 3, this receptor was up regulated and most of the cells are CD56bright CD16bright from day 7 to day 12. According FACS FCS/SSC dot plot, NK cells acquired morphology of large activated lymphocytes and some of them expressed activation markers such CD25. Finally, these cells were able to kill efficiently tumour cell line K562. Thus our data show that vericyte® NK cell growth medium allows the expansion of functional CD16+CD56+ NK cells. Cytokine production and ADCC function are under investigation. [less ▲]

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See detailExpansion of the Magdalenian in Northwest Europe
Miller, Rebecca ULg; Noiret, Pierre ULg

Poster (2011)

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See detailExpansion of the main auroral oval at Jupiter : evidence for Io’s control over the Jovian magnetosphere
Bonfond, Bertrand ULg; Grodent, Denis ULg; Gérard, Jean-Claude ULg et al

Poster (2012, April)

In spring 2007, New Horizons' Jupiter fly-by provided a unique opportunity for the largest observation campaign dedicated to the Jovian aurora ever carried out by the Hubble Space Telescope. UV images of ... [more ▼]

In spring 2007, New Horizons' Jupiter fly-by provided a unique opportunity for the largest observation campaign dedicated to the Jovian aurora ever carried out by the Hubble Space Telescope. UV images of the aurora have been acquired on a quasi-daily basis from mid-February to mid-June 2007. Polar projection of the auroral emissions clearly show a continuous long-term expansion of main oval additionally to day by day variations. The main oval moved so much that the Ganymede footprint, which is usually located equatorward of the main emissions, has even been observed inside of it. Simultaneously, the occurrence rate of large equatorward isolated auroral features increased over the season. These emission patches are generally attributed to injections of depleted flux tubes. On 6th June, one of these features exceptionally moved down to the Io footpath. The Io footprint seemed to disappear while the footprint moved through this patch of emission. This disappearance is a unique case among all the UV images of the aurora acquired during the last 12 years. We suggest that all these changes seen in the Jovian aurora are evidence for a major reconfiguration of the magnetosphere induced by increased volcanic activity on Io. Indeed, New Horizons observed particularly intense activity from the Tvashtar volcano in late February 2007. Moreover, sodium cloud brightening caused by volcanic outbursts have also been seen in late May 2007. According to our interpretation, repeated volcanic outbursts beefed up the plasma torus density and its mass outflow rate. This caused the corotation breakdown boundary to migrate closer to Jupiter. Consequently, the main auroral oval moved equatorward. As heavy flux tubes move outward, sparsely filled ones should be injected into the inner magnetosphere in order to conserve the magnetic flux in this region. This phenomenon could explain the large number of injection signatures observed in May-June 2007. Such a cloud of depleted flux tubes probably disrupted the Io-magnetosphere interaction, leading to an abnormally faint Io footprint. [less ▲]

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See detailExpansion ou régression des aires de distribution de quelques espèces de Coléoptères Elateridae d'Europe occidentale
Jeuniaux, Charles ULg

in Mém. soc. r. belge ent. (1992), 35

L'examen des matériaux de collection accumulés depuis 150 ans et le traitement cartographique et statistique des données permettent de reconnaître certaines tendances expansives ou régressives des aires ... [more ▼]

L'examen des matériaux de collection accumulés depuis 150 ans et le traitement cartographique et statistique des données permettent de reconnaître certaines tendances expansives ou régressives des aires de distribution des Elatérides en Europe occidentale; Dans certains cas, ces tendances peuvent être attribuées à l'effet de l'altération des conditions écologiques, d'origine anthropiques, ou à celui de modifications méso- ou macroclimatiques. [less ▲]

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See detailExpansion urbaine et risques hydrologiques : cas de Butembo (RD Congo)
Sahani, Muhindo; Ozer, Pierre ULg; Moeyersons, Jan

in Ozer, André; Ozer, Pierre (Eds.) Colloque International "La Géographie Physique et les Risques Naturels" - Livre de résumés (2014)

Butembo constitue un cas typique de zone urbaine en région tropicale humide rencontrant une explosion démographique exceptionnelle. L’exode vers Butembo pour fuir l’insécurité dans la sous-région a ... [more ▼]

Butembo constitue un cas typique de zone urbaine en région tropicale humide rencontrant une explosion démographique exceptionnelle. L’exode vers Butembo pour fuir l’insécurité dans la sous-région a conduit à une rapide concentration spontanée des populations et à une urbanisation sans cesse croissante. L’imperméabilisation des vastes étendues de terres consécutive à cette expansion spatiale rapide de la ville a généré des problèmes environnementaux qui affectent la structure urbaine. La ville est actuellement confrontée à des risques hydrologiques diversifiés : ravinements progressifs et régressifs, inondations, et remobilisation d’anciens glissements de terrain. [less ▲]

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See detailExpansion urbaine et risques hydrologiques : cas de Butembo (RDC)
Sahani, Muhindo; Moeyersons, Jan; Ozer, Pierre ULg

Poster (2013, December 19)

Butembo constitue un cas typique de zone urbaine en région tropicale humide rencontrant une explosion démographique exceptionnelle. L’exode vers Butembo pour fuir l’insécurité dans la sous-région a ... [more ▼]

Butembo constitue un cas typique de zone urbaine en région tropicale humide rencontrant une explosion démographique exceptionnelle. L’exode vers Butembo pour fuir l’insécurité dans la sous-région a conduit à une rapide concentration spontanée des populations et à une urbanisation sans cesse croissante. L’imperméabilisation des vastes étendues de terres consécutive à cette expansion spatiale rapide de la ville a généré des problèmes environnementaux qui affectent la structure urbaine. A l’instar de nombreuses villes d’Afrique centrale, Butembo est actuellement confrontée à des risques hydrologiques diversifiés : ravinements progressifs et régressifs, inondations, et remobilisation d’anciens glissements de terrain. [less ▲]

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See detailLes expansions cuticulaires bordantes, formation nouvelle des décapodes natantia. Données morphologiques et biochimiques chez Palaemon serratus (Pennant, 1877)
Drach, P.; Jacques, F.; Jeuniaux, Charles ULg et al

in Bulletin de la Société Zoologique de France (1982), 107(2), 437-447

In the Decapoda Natantia, transparent cuticular lamellae extend backwards from the tergite and the procurrent lamina ; similar lamellae extend around external and internal cuticles of pleurites ; they ... [more ▼]

In the Decapoda Natantia, transparent cuticular lamellae extend backwards from the tergite and the procurrent lamina ; similar lamellae extend around external and internal cuticles of pleurites ; they make an accute dihedron on the ridge of which there is often a row of denticles. The most specific biochemical reactions demonstrate the presence of chitine in these formations. Linear series of trate the presence of chitine in these formations. Linear series of thin canals are visible : these are the pore canals of the dihedral shaped epithelial cells located between the tergite and the procurrent lamina. These expansions sweep the anterior part of the tergite covered during the extension movement ; this also true for the expansions situated on the posterior border of pleurites during the flexion movements. [less ▲]

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See detailExpansions of Nanotechnology
van Lente, Harro; Coenen, Christopher; Fleischer, Torsten et al

in van Lente, Harro; Coenen, Christopher; Fleischer, Torsten (Eds.) et al Little by Little: Expansions of Nanoscience and Emerging Technologies (2012)

Little by little, nanotechnology has emerged amid enormous anticipations and fantastic promises of new materials, aspiring to manipulate our world “atom by atom.” While these grand visions continue to ... [more ▼]

Little by little, nanotechnology has emerged amid enormous anticipations and fantastic promises of new materials, aspiring to manipulate our world “atom by atom.” While these grand visions continue to capture the imaginations of various audiences—and continue to be contested, as well—nanotechnology has developed into more than that. During the last two decades, many research programs and industrial R&D expenditures have resulted in actual products and tangible innovations. Nanotechnology, it seems, is expanding. But what does it mean to say that nanotechnology is expanding? [less ▲]

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