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See detailFlux and color variations of the multiply imaged quasars HE0435 and UM673
Ricci, Davide ULg

Scientific conference (2011, March 04)

We present photometric studies of the gravitationally lensed QSOs UM673 and HE0435. Concerning the doubly imaged quasar UM673, we are presently carrying out a preliminary analysis of the observations ... [more ▼]

We present photometric studies of the gravitationally lensed QSOs UM673 and HE0435. Concerning the doubly imaged quasar UM673, we are presently carrying out a preliminary analysis of the observations. Regarding the quadruply imaged quasar HE0435, the analysis is complete. The variations of this lensed quadruplet show that the source is intrinsically variable. Furthermore, one component is also very likely affected by microlensing. The significant color variations observed for the four lensed images are also consistent with variations produced by the source, and not by the lens. Our flux and color analysis are based upon different methods (image subtraction and PSF fitting) for studying the multi-band variability. [less ▲]

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See detailFlux and color variations of the quadruply imaged quasar HE 0435--1223
Ricci, Davide ULg; Poels, Joël ULg; Elyiv, Andrii ULg et al

in Astronomy and Astrophysics (2011), 528

We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the ... [more ▼]

We present VRi photometric observations of the quadruply imaged quasar HE 0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time. methods: We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and PSF (Point Spread Function) fitting.results: Between these two seasons, our results show an evident decrease in flux by ~0.2-0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase (~0.05-0.015) in their V-R and R-i color indices. conclusions: These flux and color variations are very likely caused by intrinsic variations of the quasar between the observed epochs. Microlensing effects probably also affect the brightest "A" lensed component. [less ▲]

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See detailFlux argileux du Néogène au Quaternaire dans l'Océan Indien Nord
Fagel, Nathalie ULg

Book published by Soc. géol. Nord (1994)

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See detailFlux avalanches triggered by AC magnetic fields in superconducting thin films
Motta, M; Colauto, F; Johansen, TH et al

in Physica C (2012), 479

Flux avalanches are known to occur as a consequence of thermomagnetic instabilities. Some of their fingerprints are jumps in magnetization curves, or a paramagnetic reentrance in AC susceptibility ... [more ▼]

Flux avalanches are known to occur as a consequence of thermomagnetic instabilities. Some of their fingerprints are jumps in magnetization curves, or a paramagnetic reentrance in AC susceptibility measurements. In this work we have studied flux avalanches triggered by an AC field cycle by means of AC susceptibility and residual magnetization after an applied AC field measured as a function of an AC excitation field (h). These measurements allow comparing both results with magneto-optical imaging carried out in similar conditions. The results show a correspondence for the onset of the avalanche activity, as well as between the residual magnetic moment and the mean gray value calculated from the magneto-optical images in the remanent state. [less ▲]

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See detailFlux avalanches triggered by microwave depinning of magnetic vortices in Pb superconducting films
Awad, A. A.; Aliev, F. G.; Ataklti, G. W. et al

in Physical Review. B, Condensed Matter and Materials Physics (2011), 84(22), 224511

We observe abrupt changes in broadband microwave permeability of thin Pb superconducting films as functions of the microwave frequency and intensity, as well as of external magnetic field. These changes ... [more ▼]

We observe abrupt changes in broadband microwave permeability of thin Pb superconducting films as functions of the microwave frequency and intensity, as well as of external magnetic field. These changes are attributed to vortex avalanches generated by microwave induced depinning of vortices close to the sample edges. We map the experimental results on the widely used theoretical model assuming reversible response of the vortex motion to ac drive. It is shown that our measurements provide an efficient method of extracting the main parameter of the model—depinning frequencies—for different pinning centers. The observed dependences of the extracted depinning frequencies on the microwave power, magnetic field, and temperature support the idea that the flux avalanches are generated by microwave induced thermomagnetic instabilities. [less ▲]

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See detailFlux closure during a substorm observed by Cluster, Double Star, IMAGE FUV, SuperDARN, and Greenland magnetometers
Milan, S. E.; Wild, J. A.; Hubert, Benoît ULg et al

in Annales Geophysicae (2006), 24(2), 751-767

We examine magnetic flux closure during an extended substorm interval on 29 August 2004 involving a two-stage onset and subsequent re-intensifications. Cluster and Double Star provide observations of ... [more ▼]

We examine magnetic flux closure during an extended substorm interval on 29 August 2004 involving a two-stage onset and subsequent re-intensifications. Cluster and Double Star provide observations of magnetotail dynamics, while the corresponding auroral evolution, convection response, and substorm current wedge development are monitored by IMAGE FUV, SuperDARN, and the Greenland magnetometer chain, respectively. The first stage of onset is associated with the reconnection of closed flux in the plasma sheet; this is accompanied by a short-lived auroral intensification, a modest substorm current wedge magnetic bay, but no significant ionospheric convection enhancement. The second stage follows the progression of reconnection to the open field lines of the lobes; accompanied by prolonged auroral bulge and westward-travelling surge development, enhanced magnetic bays and convection. We find that the tail dynamics are highly influenced by ongoing dayside creation of open flux, leading to flux pile-up in the near-tail and a step-wise down-tail motion of the tail reconnection site. In all, 5 dipolarizations are observed, each associated with the closure of similar to 0.1 GWb of flux. Very simple calculations indicate that the X-line should progress down-tail at a speed of 20 km s(-1) or 6 R-E between each dipolarization. [less ▲]

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See detailLes flux d'azote mobilisés par les agricultures belges
Debouche, Charles ULg

in Bulletin d'Information (Association Royale des Ingénieurs Issus de la Fusagx - Aigx) (2001), 4

Les flux de matières azotées mobilisés par les exploitations agricoles sont identifiés et quantifiés par divers modèles mathématiques. Ceux-ci sont conçus de manière à pouvoir être appliqués tant au ... [more ▼]

Les flux de matières azotées mobilisés par les exploitations agricoles sont identifiés et quantifiés par divers modèles mathématiques. Ceux-ci sont conçus de manière à pouvoir être appliqués tant au niveau d'une exploitation agricole qu'au niveau d'un territoire déterminé. Après avoir décrit succinctement ces modèles, leurs caractéristiques et leurs limites, le résultat de leur application aux agricultures flamande et wallonne est présenté. Il met en évidence une différence importante entre ces deux agricultures, notamment quant à leurs responsabilités environnementales. Les flux d'azote mobilisés par des exploitations agricoles existantes sont également estimés. Ils illustrent la grande diversité de comportement d'exploitations agricoles apparemment semblables. [less ▲]

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See detailLes flux de CO2 en grandes cultures
Dufranne, Delphine ULg; Jerome, Elisabeth ULg; Moureaux, Christine ULg et al

Conference (2010, February 24)

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See detailFlux de Composés Organiques Volatils (COV) au-dessus d'une forêt belge: De la mesure par eddy covariance à la recherche des mécanismes d'émission et de déposition.
Laffineur, Quentin ULg

Scientific conference (2010, September 16)

Les écosystèmes forestiers à l'échelle globale sont les principaux émetteurs de COV (Composés Organiques Volatils). La quantité de COV émise et leur haute réactivité avec les principaux oxydants de l ... [more ▼]

Les écosystèmes forestiers à l'échelle globale sont les principaux émetteurs de COV (Composés Organiques Volatils). La quantité de COV émise et leur haute réactivité avec les principaux oxydants de l'atmosphère contribuent de manière non négligeable à la chimie de l'atmosphère (ozone). Dans le cadre d'un projet fédéral belge, des mesures continues de flux de COV par eddy-covariance au moyen d'un PTR-MS sont réalisées sur le site forestier de Vielsalm. Une première campagne de mesures a été effectuée pendant la période Juillet-Octobre 2009 et une seconde campagne a débutée au mois de Mars 2010. Les émissions les plus importantes observées ont été celles de l'isoprène, des monoterpènes et du méthanol. Des dépositions importantes de méthanol ont également été observées. L'exposé présentera ces mesures et leur exploitation avec pour objectif principal d'étudier la variabilité saisonnière des flux de COVs en relation avec leurs principales variables de contrôle. Les mécanismes potentiellement responsables de cette variabilité seront discutés. [less ▲]

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See detailFlux de nitrate dans une zone à nappes superficielles en Wallonie (Belgique)
Demarets, X.; Marcoen, Jean Marie ULg; Agneessens, R. et al

in Cahiers Agricultures (1995), 4

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See detailFlux des sédiments en suspension dans les rivières du bassin de la Meuse : proposition d’une typologie régionale basée sur la dénudation spécifique des bassins versants
Van Campenhout, Jean ULg; Denis, Anne-Cécile ULg; Hallot, Eric ULg et al

in Bulletin de la Société Géographique de Liège (2013), 61

Soil erosion may be apprehended at the watershed scale by quantifying the transport of suspended sediment at its outlet. Approximately 2000 measurements of suspended sediment concentration were used to ... [more ▼]

Soil erosion may be apprehended at the watershed scale by quantifying the transport of suspended sediment at its outlet. Approximately 2000 measurements of suspended sediment concentration were used to estimate the annual sediment discharge at 80 stations located in the Walloon region (Belgium), at the outlet of watershed from 16 to 2900 km². Some regional differences have been highlighted depending on the substrate and the land use in the watershed. At the region scale, the mean annual sediment yield reaches 20 t.km-2.yr-1 in Lorraine, 34 t.km-2.yr-1 in Ardenne and 69 t.km-2.yr-1 in Entre-Vesdre-et-Meuse. The size of suspended particles and the proportion of organic matter also show differences between each agro-geographical area. Data from other academic or administrative works were incorporated into the database to identify the best sites for continuous measuring of the suspended load concentration in Wallonia. [less ▲]

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See detailFlux des sédiments en suspension dans les rivières du bassin de la Meuse : proposition d'une typologie régionale basée sur la dénudation spécifique des bassins versants
Van Campenhout, Jean ULg; Hallot, Eric ULg; Houbrechts, Geoffrey ULg et al

Poster (2013, October 15)

L'érosion des sols peut être appréhendée à l'échelle du bassin versant en quantifiant le transport sédimentaire en suspension à son exutoire. Environ 2.000 mesures de concentration des matières en ... [more ▼]

L'érosion des sols peut être appréhendée à l'échelle du bassin versant en quantifiant le transport sédimentaire en suspension à son exutoire. Environ 2.000 mesures de concentration des matières en suspension ont permis d'estimer les débits solides annuels en fonction des débits liquides observés dans ces cours d'eau. Une méthodologie simple a été mise en place et appliquée à un réseau de 80 stations, à l’exutoire de bassins versants d’une superficie comprise entre 16 et 2.900 km² situées en région wallonne. Des différenciations régionales ont pu être mises en évidence en fonction du substrat et de l'occupation du sol des bassins versants. La granulométrie des particules transportées et la proportion de matière organique complètent l'analyse et confirment les différenciations observées selon les régions agro-géographiques. L’impact de la fréquence d’échantillonnage (et de sa synchronisation avec les débits de crue) sur l’estimation de la dénudation annuelle a été mis en évidence, ainsi que la grande variabilité interannuelle, qui est fonction de l’intensité et de la hauteur des précipitations. L’érosion des sols est ainsi très sensible aux événements extrêmes. Par ailleurs, l’intérêt de longues campagnes de mesures est souligné. Des données issues de travaux antérieurs ont également été intégrées à la base de données. Son interprétation a permis de définir les meilleurs sites susceptibles d’accueillir à long terme un réseau de mesure en continu de la concentration des matières en suspension en Wallonie. [less ▲]

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See detailFlux pinning properties of holes and blind holes arranged periodically in a superconductor
Raedts, S.; Silhanek, Alejandro ULg; Van Bael, M. J. et al

in Physica C: Superconductivity (2004), 404(1-4), 298-301

We investigate the dynamic response of a vortex lattice in nanostructured superconducting Pb films by means of ac-magnetization measurements. We compare the flux pinning properties of superconducting Pb ... [more ▼]

We investigate the dynamic response of a vortex lattice in nanostructured superconducting Pb films by means of ac-magnetization measurements. We compare the flux pinning properties of superconducting Pb films with arrays of fully perforated holes (antidots) and partially drilled holes (blind holes). Our results show that an array of blind holes, characterized by a thin superconducting bottom layer, gives rise to a less efficient pinning potential than an array of antidots. On top of that, a lower number of flux quanta trapped per pinning site (the saturation number), is observed for the blind hole array. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailLe flux solsticial de la Baltique: réponse à l'article du général Liagre
Folie, François ULg

in Ciel et Terre (1885), 2e série, t. 1

The author defends his theory about the influence of the lunar attraction on the mercury barometer.

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See detailFlux transport and tail dynamics during a prolonged substorm interval
Milan, S. E.; Wild, J. A.; Hubert, Benoît ULg et al

in Cluster and Double Star Symposium (2006, January 01)

Not Available

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See detailFlux-based Risk Assessement of the impact of Contaminants on Water resources and ECOsystems
Jamin, Pierre ULg; Dujardin, Juliette; Crèvecoeur, Sophie et al

Report (2012)

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See detailFlux-based risk assessment of the impact of contamnants on water ressources and ecosystems - FRAC-WECO.
Jamin, Pierre ULg; Dujardin, J.; Crévecoeur, Sophie et al

Report (2012)

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See detailFlux-pinning properties of superconducting films with arrays of blind holes
Raedts, S.; Silhanek, Alejandro ULg; Van Bael, M. J. et al

in Physical Review. B : Condensed Matter (2004), 70(2),

We performed ac susceptibility measurements to explore the vortex dynamics and the flux-pinning properties of superconducting Pb films with an array of microholes (antidots) and not fully perforated holes ... [more ▼]

We performed ac susceptibility measurements to explore the vortex dynamics and the flux-pinning properties of superconducting Pb films with an array of microholes (antidots) and not fully perforated holes (blind holes). A lower ac shielding together with a smaller extension of the linear regime for the lattice of blind holes indicates that these centers provide a weaker pinning potential than antidots. Moreover, we found that the maximum number of flux quanta trapped by a pinning site, i.e., the saturation number n(s), is lower for the blind hole array. [less ▲]

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