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See detailVariability of major fatty acid contents in Luxembourg dairy cattle
Soyeurt, Hélène ULiege; Arnould, Valérie ULiege; Dardenne, Pierre et al

in Book of Abstracts of the 60th Annual Meeting of the European Association for Animal Production (2009)

Detailed reference viewed: 33 (6 ULiège)
See detailVariability of methane in the epilimnion of Lake Kivu
Borges, Alberto ULiege; Abril, Gwenael; Delille, Bruno ULiege et al

Poster (2011, July 11)

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See detailVariability of methane in the epilimnion of Lake Kivu
Borges, Alberto ULiege; Abril, G.; Morana, C. et al

Poster (2012, April 22)

Detailed reference viewed: 16 (2 ULiège)
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See detailVariability of methane in the epilimnion of Lake Kivu
Borges, Alberto ULiege; Abril, G.; Delille, Bruno ULiege et al

Poster (2011, April 08)

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See detailVariability of North Sea pH and CO2 in response to North Atlantic Oscillation forcing
Salt, L.A.; Thomas, H.; Prowe, A.E.F. et al

in Journal of Geophysical Research. Biogeosciences (2013), 118(1-9),

High biological activity causes a distinct seasonality of surface water pH in the North Sea, which is a strong sink for atmospheric CO 2 via an effective shelf pump. The intimate connection between the ... [more ▼]

High biological activity causes a distinct seasonality of surface water pH in the North Sea, which is a strong sink for atmospheric CO 2 via an effective shelf pump. The intimate connection between the North Sea and the North Atlantic Ocean suggests that the variability of the CO 2 system of the North Atlantic Ocean may, in part, be responsible for the observed variability of pH and CO 2 in the North Sea. In this work, we demonstrate the role of the North Atlantic Oscillation (NAO), the dominant climate mode for the North Atlantic, in governing this variability. Based on three extensive observational records covering the relevant levels of the NAO index, we provide evidence that the North Sea pH and CO 2 system strongly responds to external and internal expressions of the NAO. Under positive NAO, the higher rates of in fl ow of water from the North Atlantic Ocean and the Baltic out fl ow lead to a strengthened north-south biogeochemical divide. The limited mixing between the north and south leads to a steeper gradient in pH and partial pressure of CO 2 (pCO 2 ) between the two regions in the productive period. This is exacerbated further when coinciding with higher sea surface temperature, which concentrates the net community production in the north through shallower strati fi cation. These effects can be obscured by changing properties of the constituent North Sea water masses, which are also in fl uenced by NAO. Our results highlight the importance of examining interannual trends in the North Sea CO 2 system with consideration of the NAO state [less ▲]

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See detailVariability of North Sea pH and CO2 pumping in response to North Atlantic Oscillation forcing
Salt, L; Thomas, H; Prowe, F et al

Poster (2013, April 07)

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See detailThe variability of primary production in the ocean: from the synoptic to the global scale: The 45th International Liege Colloquium on Ocean Dynamics, Liege, Belgium, May 13-17, 2013
Grégoire, Marilaure ULiege; Levy, Marina; Marra, John et al

Book published by Journal of Marine System, Elsevier Science (2015)

The 45th International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered two hundreds scientists from around the world to discuss new insights related to the evaluation ... [more ▼]

The 45th International Liege Colloquium on Ocean Dynamics (http://modb.oce.ulg.ac.be/colloquium/) gathered two hundreds scientists from around the world to discuss new insights related to the evaluation of primary production at various spatial and temporal scales and in different regions of the world ocean (e.g. the polar and sea-ice region, the coastal and the deep ocean). Over the past two decades, substantial efforts were deployed to evaluate oceanic primary production. These efforts include in situ measurements of uptake rates using isotopic techniques, remote sensing, autonomous instrumentation for bio-optics, carbon or oxygen measurements, and the development of semi-empirical to complex biogeochemical models. The colloquium presented the opportunity to review the current knowledge in the estimation of primary production, and to assess the impact of physical processes on ocean productivity. Particular attention focused on the importance of physical processes at different spatial and temporal scales for controlling the level and variability of primary production and on the development of adequate methodologies to tackle this variability in order to derive large-scale, climate-driven budgets. Refined biogeochemical models considering for instance phytoplankton physiology, the representation of variable elemental stoichiometric ratios, the role of mixotrophy as well as satellite algorithms that are now able to simulate the plankton functional types are good candidates for scaling up. Contributions dealing with the difficult issue of interoperability of in-situ, satellite and modelling estimates of primary production were presented. Details on the terms of reference as well as the thematic session that were organized can be found at http://modb.oce.ulg.ac.be/?page=colloquium&year=2013. [less ▲]

Detailed reference viewed: 81 (6 ULiège)
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See detailThe variability of RR Tel
Heck, A.; Manfroid, Jean ULiege

in The Messenger (1982), 30

Photometric measurements of RR Tel performed at ESO are discussed. RR Tel is a galactic nova which has been associated with a sole outburst, observed in 1944. The photometric observations were made in the ... [more ▼]

Photometric measurements of RR Tel performed at ESO are discussed. RR Tel is a galactic nova which has been associated with a sole outburst, observed in 1944. The photometric observations were made in the ubvy system in August 1981, when a strong brightening was detected in V. IUE data subjected to a Fourier analysis indicate that the object has a period within 5 days of 395 days. Measurements of brightening of the J component also yield a period of 390 days. The presence of a Mira variable is considered, noting the supporting evidence from H2O and TiO spectral bands, but equally the lack of IR data until after 1960. It is suggested that data from before 1944 indicate that modulated bursts of mass transfer and accompanying accretion events preceeded the outburst of the underlying binary star, which could be a link between dwarf novae, classical novae, and symbiotic stars. [less ▲]

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See detailVariability of shelf sea pH and surface water CO2 in response to North Atlantic Oscillation forcing
Salt, L.; Thomas, H.; Prowe, A.E.F. et al

Conference (2012, April 22)

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See detailVariability of shelf-seas hydrodynamic models: lessons from the NOMADS2 project
Delhez, Eric ULiege; Damm, P.; de Goede, E. et al

in Journal of Marine Systems (2004), 45(1-2), 39-53

Model simulations at the seasonal time scale are often lacking in any real assessment of the associated error bounds. We use here the results of nine three-dimensional hydrodynamic models covering (at ... [more ▼]

Model simulations at the seasonal time scale are often lacking in any real assessment of the associated error bounds. We use here the results of nine three-dimensional hydrodynamic models covering (at least) the Southern and Central North Sea to investigate the range of model variability and model errors. The models are run as they are, i.e. with their usual grid, model domain, equation formulation and numerical details, but in a consistent framework-bathymetry, boundary and initial conditions, meteorological forcing functions interpolated from a common data set-. While the responses of the models are clearly qualitatively similar, large quantitative differences do occur. These differences are often of the same order of magnitude as both the ensemble mean and the sensitivity of the individual results to critical parameters. The direct comparison of the results with measurements from the North Sea Project provides a quantification of the model errors for the salinity and temperature distributions. Using the cost function approach, it is shown that the mean errors (for all the models and all seasons) reach about 70% of the natural variability for the temperature and 90% for the salinity. These errors are larger in summer, when a stratification develops over the Central and Northern North Sea, than in winter. No single model parameter (spatial resolution, turbulence closure scheme, model domain, etc.) can explain the different behaviours of the models. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 42 (7 ULiège)
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See detailThe variability of SPICA
Sterken, C.; Jerzykiewicz, M.; Manfroid, Jean ULiege

in Astronomy and Astrophysics (1986), 169

Differential uvby observations of Spica are presented and analyzed. No coherent short-period light or colour index variations are found. An analysis of the ellipsoidal light variation leads to a new value ... [more ▼]

Differential uvby observations of Spica are presented and analyzed. No coherent short-period light or colour index variations are found. An analysis of the ellipsoidal light variation leads to a new value of the radius of the primary component, which agrees very well with the radius determined by means of the Narrabri stellar intensity interferometer. The analysis also shows that the photometric data are consistent with the spectrographic period of the rotation of the line of apsides. In addition, recent hypotheses concerning the apparently extinct pulsations of the primary component are discussed. It is pointed out that the enhanced surface helium models of Cox (1985) predict pulsation constants substantially larger than the pulsation constant derived from the observationally determined mass and radius. [less ▲]

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See detailVariability of the air-sea CO2 fluxes inferred from in situ and remotely sensed parameteres in the Southern Ocean.
Boutin, J.; Rangama, Y.; Etcheto, J. et al

Poster (2002, October)

Detailed reference viewed: 7 (0 ULiège)
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See detailVariability of the chromosomal number and meiotic behavior in populations of Bidens pilosa L. (Asteraceae) from southern Brazil
Fachinetto, JM; Laughinghouse IV, Haywood ULiege; Silva, ACF et al

in Caryologia : Giornale di Citologia, Citosistematica, e Citogenetica (2008), 61(2), 164-169

Detailed reference viewed: 13 (1 ULiège)
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See detailVariability of the effects of serum-free medium, dibutyryl-cyclic AMP or theophylline on the morphology of cultured new-born rat astroblasts.
Moonen, Gustave ULiege; Cam, Y.; Sensenbrenner, M. et al

in Cell & Tissue Research (1975), 163(3), 365-372

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See detailVariability of the gas transfer velocity of CO2 in a macrotidal estuary (The Scheldt)
Borges, Alberto ULiege; Vandenborght, Jean-Pierre; Schiettecatte, Laure-Sophie et al

in Estuaries (2004), 27(4), 593-603

We report a large set of 295 interfacial carbon dioxide (CO2) flux measurements obtained in the Scheldt estuary in November 2002 and April 2003, using the floating chamber method. From concomitant ... [more ▼]

We report a large set of 295 interfacial carbon dioxide (CO2) flux measurements obtained in the Scheldt estuary in November 2002 and April 2003, using the floating chamber method. From concomitant measurements of the air-water CO2 gradient, we computed the gas transfer velocity of CO2. The gas transfer velocity is well correlated to wind speed and a simple linear regression function gives the most consistent fit to the data. Based on water current measurements, we estimated the contribution of water current induced turbulence to the gas transfer velocity, using the conceptual relationship of O’Connor and Dobbins (1958). This allowed us to construct an empirical relationship to compute the gas transfer velocity of CO2 that accounts for the contribution of wind and water current. Based on this relationship, the spatial and temporal variability of the gas transfer velocity in the Scheldt estuary was investigated.Water currents contribute significantly to the gas transfer velocity, but the spatial and temporal variability (from daily to seasonal scales) is mainly related to wind speed variability. [less ▲]

Detailed reference viewed: 288 (6 ULiège)
See detailVariability of the gas transfer velocity of CO2 in a macrotidal estuary (The Scheldt)
Borges, Alberto ULiege; Vanderborght, Jean-Pierre; Schiettecatte, Laure-Sophie et al

Poster (2005)

Detailed reference viewed: 10 (1 ULiège)
See detailVariability of the Jovian aurorae: focus on a selection of recent results
Bonfond, Bertrand ULiege; Grodent, Denis ULiege; Gérard, Jean-Claude ULiege et al

Conference (2013, July 11)

The aurorae at Jupiter can be separated into four main components: the satellite footprints, the outer emissions, the main emissions and the polar emissions. Each of these components displays some form of ... [more ▼]

The aurorae at Jupiter can be separated into four main components: the satellite footprints, the outer emissions, the main emissions and the polar emissions. Each of these components displays some form of variability in location, brightness and/or shape. The nature and the timescale of these changes is particularly revealing of the processes at play. The footprints of Io and Ganymede are often made of several spots. The distance between these spots and their brightness essentially varies as the planetary magnetic dipole rotates relative to the moons and as the plasma torus or plasma sheet wobble across the satellite orbital plane. However, the spots brightness can also considerably vary on a timescale of minutes as well as from one year to another. The outer emissions are made of diffuse, patchy or arc-shaped emissions. Two different sources have been proposed to explain these features: injections of hot plasma from the outer magnetosphere and the pitch angle scattering boundary. These features usually last for a few Jovian rotations, but their occurrence rate appears to be related to the global dynamics of the inner magnetosphere on timescales of months. The main emissions sometimes appear as a complete oval, but they usually have a more chaotic appearance, with broken arcs, gaps and forks. Their brightness and morphology respond to changes in the solar wind characteristics. Nevertheless, the dawn portion of the main emissions sometimes displays spectacular brightening apparently unrelated to the solar wind: the dawn storms. Moreover, on timescales of several months, the statistical location of the main emissions also evolves as the material input from Io increases or decreases. Globally speaking, the polar emissions also respond to the solar wind input. However, the term “polar emissions” encompasses many different auroral features obviously driven from different mechanisms. Spots and arcs, located just inside the main emissions on the dawn and night side and lasting for a few tens of minutes, have been seen to re-occur every 2 to 3 days. They have thus been associated with night-side reconnection related to the Vasyliũnas cycle. On the other hand, the dusk-side of the polar region is the locus of quasi-periodic UV flares on timescales of 2 to 3 minutes, while periodicities of 20 to 45 minutes have been identified for their X-ray counterpart. The central part of the polar region is very dynamic, with patches of emissions constantly appearing, moving and disappearing within minutes. However, along with these patches, elongated auroral arcs dubbed “polar auroral filaments” may remain present for several consecutive days. As we will see in this review talk, the current data set of UV images from the Hubble Space Telescope, including the brand new time-tag sequences from the latest 2012-2013 campaign, gives access to a wide range of auroral phenomena that only begin to reveal their secrets. [less ▲]

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See detailVariability of the net air-sea CO2 flux inferred from shipboard and satellite measurements in the Southern Ocean south of Tasmania and New Zealand
Rangama, Y.; Boutin, J.; Etcheto, J. et al

in Journal of Geophysical Research. Oceans (2005), 110(C9),

We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of ... [more ▼]

We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of the small-scale (10-100 km) pCO(2) variability and to estimate the net air-sea CO2 flux in the region (125 degrees E-205 degrees E; 45 degrees S-60 degrees S), which represents 22% of the Southern Ocean area between 45 degrees S and 60 degrees S. We split the study area into several biogeochemical provinces. In chlorophyll-poor regions, pCO(2) is negatively correlated with SST, indicating that pCO(2) is mostly controlled by mixing processes. For Chl > 0.37 mg m(-3), pCO(2) is negatively correlated with Chl, indicating that pCO(2) variability is mostly controlled by carbon fixation by biological activity. We deduce fields of pCO(2) and of air-sea CO2 fluxes from satellite parameters using pCO(2)-SST, pCO(2)-chlorophyll relationships and air-sea gas exchange coefficient, K, from satellite wind speed. We estimate an oceanic CO2 sink from December 1997 to December 1998 of -0.08 GtC yr(-1) with an error of 0.03 GtC yr(-1). This sink is approximately 38% smaller than that computed from the Takahashi et al. (2002) climatological distribution of Delta pCO(2) for the 1995 year but with the same K (-0.13 GtC yr(-1)). When we correct ocean pCO(2) for the interannual variability between 1995 and 1998, the difference is even larger, and we cannot reconcile both estimates in February-March and from June to November. This strengthens the need of new in situ measurements for validating extrapolation methods and for improving knowledge of interannual pCO(2) variability. [less ▲]

Detailed reference viewed: 69 (9 ULiège)