Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailGlobal auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations
Coumans, Valérie ULg; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Annales Geophysicae (2004), 22(5), 1595-1611

The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI 12 camera sensitive to Doppler shifted ... [more ▼]

The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI 12 camera sensitive to Doppler shifted Lyman-alpha emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI 12 around 14:00MLT at similar to75degrees MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in aurora] arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop along field lines in the upward field-aligned currents by creating an opposite polarization electric field. This feedback mechanism possibly reduces the electron acceleration. [less ▲]

Detailed reference viewed: 72 (9 ULg)
Full Text
Peer Reviewed
See detailGlobal auroral proton precipitation observed by IMAGE-FUV: Noon and midnight brightness dependence on solar wind characteristics and IMF orientation
Coumans, Valérie ULg; Gérard, Jean-Claude ULg; Hubert, Benoît ULg et al

in Journal of Geophysical Research. Space Physics (2006), 111(A5),

The brightness of proton aurora observed near solar maximum at summer and winter solstices with the FUV-SI12 global imager on board the IMAGE satellite has been correlated with the solar wind and the ... [more ▼]

The brightness of proton aurora observed near solar maximum at summer and winter solstices with the FUV-SI12 global imager on board the IMAGE satellite has been correlated with the solar wind and the interplanetary magnetic field characteristics measured by ACE satellite instruments. By contrast to the electron aurora, we find a strong correlation both on nightside and dayside between the proton precipitated power and the solar wind dynamic pressure calculated with 1-hour averaged solar wind data. For both southward and northward IMF, the proton power increases with \B-z\, but much more rapidly on the nightside for southward IMF orientation. Correlations for the nightside aurora were also calculated with a series of solar wind-magnetosphere coupling functions. We find highest correlation coefficients for expressions containing the dynamic pressure or involving the solar wind electric field in the Y-Z plane. The influence of the solar wind dynamic pressure on the proton aurora is tentatively explained by the effect of the pressure on the shape of the magnetosphere, generating stretching of the magnetotail and proton precipitation but also by other coupling processes between the solar wind and the magnetosphere. Adding FUV-WIC and SI13 electron aurora images in the study, we determine how proton and electron precipitations simultaneously react to solar wind and IMF characteristics and Kp. Results shows that protons are more reactive to dynamic pressure variations than electrons when B-z is positive, while the influence on of both types of particles is similar for negative B-z. The precipitating proton flux is found proportionally larger compared with the electron flux when the total auroral flux increases for low activity level. Instead, for high activity level, the proportion of the proton and the electron powers are similar when auroral power increases. Consequently, it is suggested that similar mechanisms cause proton and electron auroral precipitation for high activity levels, while they appear somewhat decoupled for lower activity conditions. [less ▲]

Detailed reference viewed: 42 (7 ULg)
See detailGlobal balances as a basis for ethical statements
Fayyaz, Sara; Kopriwa, Nicole; Hillerbrand, Rafaela et al

Poster (2010)

Detailed reference viewed: 12 (0 ULg)
Full Text
Peer Reviewed
See detailThe global biogeography of semi-arid periodic vegetation patterns.
Deblauwe, V; Barbier, N; Couteron, P et al

in Global Ecology & Biogeography (2008), 17(6), 715-723

Detailed reference viewed: 15 (0 ULg)
Full Text
Peer Reviewed
See detailGlobal capacity announcement of electrical distribution systems: A pragmatic approach
Cornélusse, Bertrand ULg; Vangulick, David; Glavic, Mevludin ULg et al

in Sustainable Energy, Grids and Networks (2015), 4

We propose a pragmatic procedure to facilitate the connection process of Distributed Generation (DG) with reference to the European regulatory framework where Distribution System Operators (DSOs) are ... [more ▼]

We propose a pragmatic procedure to facilitate the connection process of Distributed Generation (DG) with reference to the European regulatory framework where Distribution System Operators (DSOs) are, except in specific cases, not allowed to own their generation. The procedure is termed Global Capacity ANnouncement (GCAN) and is intended to compute the estimates of maximum generation connection amount at appropriate substations in a distribution system, to help generation connection decisions. The pragmatism of the proposed procedure stems from its reliance on the tools that are routinely used in distribution systems planning and operation, and their use such that the possibilities of network sterilization are avoided. The tools involved include: long-term load forecasting, long-term planning of network extension/reinforcement, network reconfiguration, and power flow. Network sterilizing substations are identified through repeated power flow computations. The proposed procedure is supported by results using an artificially created 5-bus test system, the IEEE 33-bus test system, and a part of real-life distribution system of ORES (a Belgian DSO serving a large portion of the Walloon region in Belgium). [less ▲]

Detailed reference viewed: 89 (25 ULg)
Full Text
Peer Reviewed
See detailThe global carbon cycle and its changes over glacial-interglacial cycles - Preface
François, Louis ULg; Faure, H.; Probst, J. L.

in Global and Planetary Change (2002), 33(1-2), -

Detailed reference viewed: 10 (1 ULg)
Full Text
See detailGlobal changes, human activities and (re-) emerging of mosquito-borne pathogens: diversity, ecology and control of potential vectors
Boukraa, Slimane ULg

Doctoral thesis (2016)

Worldwide, mosquitoes (Diptera: Culicidae) are known as potential vectors of pathogens that cause infectious diseases, affecting both humans and animals, such as malaria, dengue, chikungunya, West Nile ... [more ▼]

Worldwide, mosquitoes (Diptera: Culicidae) are known as potential vectors of pathogens that cause infectious diseases, affecting both humans and animals, such as malaria, dengue, chikungunya, West Nile fever and dirofilariasis. In terms of morbidity and mortality, mosquitoes are considered as the most dangerous animals confronting mankind. Indeed, over three billion people live at risk of becoming infected by a mosquito-borne disease. Focus on mosquitoes has greatly increased not only in the tropic areas but also in the Palearctic region like Europe and Mediterranean areas. Researches on re-emerging vector-borne diseases are become a major issue in human and animal health worldwide, both in the North and South hemisphere. The spread in space and time of these many vector-borne diseases is strongly influenced by environmental factors (landscape, location and abundance of hosts and vectors, etc.) and climate (temperature, humidity, etc.) that influence population dynamics of the vector and the reservoir hots of pathogens. The acquisition of bio-ecological and taxonomic knowledges of mosquitoes is nevertheless an essential step for the understanding, preventing and management of current risks of the (re)-emergence of mosquito-borne parasites and mainly the preparation and prevention against future threats. The absence of vaccine and treatments against most of mosquito-borne diseases implies efficient vector control strategies, which are up to date mainly based on the use of chemical insecticides. However, most vectors develop resistance against currently used products whereas new chemical compounds was limited firstly by financial costs in research and development, and secondly by the toxicity of derivatives to human population, biodiversity, and environment. The exploitation of new methods, such as the use of microbial communities (mainly bacteria or entomopathogenic fungi) for vector control, will be therefore a promoted strategy at the global level. This doctoral thesis focuses on five main objectives: (i) to inventory and identify mosquito fauna in the livestock areas and their surroundings, especially in the equestrian farms; (ii) to study the population genetic structure of the potential vector complex Cx. pipiens s.l.; iii) to study the phylogeny and the origin of exotic mosquito species (Ae. albopictus & Ae. koreicus) as well as the potential tracks of their introduction; (iv) to know the bioecology and spatiotemporal dynamic of potential vectors; and finally (v) to suggest a biocontrol tool that can prevent and fight the proliferation of mosquitoes especially potential vectors and those causing nuisance problems. Obtained results in this thesis allowed highlighting identification and record of new mosquito species in the studied areas. It also allowed updating the list of mosquito fauna in the two countries, Belgium (31 species including three invasive mosquitoes) and Algeria (53 species including four new records form this research: Culex brumpti, Coquillettidia richiardii, Cq. Buxtoni and Uranotaenia balfouri). The phylogenetic analyses (COI and ND4) performed during this thesis allowed to confirm that Aedes koreicus and Ae. japonicas complex constitute two distinct species. In addition, given the phylogenetic analyses (COI and ND5 genes) and information about the origin of used tires inspected during this study in Belgium, Ae. albopictus was very probably reintroduced from the United States. In both Belgium and Algeria, this work permitted identifying and confirming the presence of different molecular forms of the Cx. pipiens complex: Cx. pipiens form pipiens, Cx. pipiens f. molestus as well as their hybrid form. Medical and veterinary importance of identified mosquito species and the risk of (re-)emerging of mosquito-borne diseases in Belgium and Algeria are discussed. Finally, the endosymbiont bacteria Pseudomonas seemed to be an interesting candidate for paratransgenic bacteria in order to reduce and/or inhibit the transmission of pathogens by mosquito vectors. [less ▲]

Detailed reference viewed: 159 (5 ULg)
See detailGlobal Character of the Venus UV Night Airglow.
Stewart, A. I.; Gérard, Jean-Claude ULg; Bougher, S.

in Bulletin of the American Astronomical Society (1979, March 01)

Detailed reference viewed: 6 (1 ULg)
Full Text
See detailThe global chemistry climate model ECHAM6-HAMMOZ
Schultz, Martin G.; Franco, Bruno ULg; Kaffashzadeh, Najmeh et al

Poster (2016, February 02)

Atmospheric composition of short-lived gases and aerosols is an important component of the global climate system. Complex processes from emissions, transport, and chemical reactions to heterogeneous loss ... [more ▼]

Atmospheric composition of short-lived gases and aerosols is an important component of the global climate system. Complex processes from emissions, transport, and chemical reactions to heterogeneous loss processes and radiation interactions need to be implemented in climate models to reach an adequate understanding of the role of short-lived climate forcers on the climate system and to allow the assessment of climate impacts on the regional scale. With ECHAM6-HAMMOZ we have developed a comprehensive model of tropospheric and stratospheric aerosols and gas-phase chemistry which is now running successfully on the Jülich supercomputer JURECA. [less ▲]

Detailed reference viewed: 23 (1 ULg)
Peer Reviewed
See detailGlobal climate warming and decline of the Black Grouse in western Europe: Are predictions reliable?
Loneux, Michèle ULg

in Journal of Ornithology (2006, August), 147(5, Suppl. 1), 203

Detailed reference viewed: 52 (11 ULg)
Full Text
Peer Reviewed
See detailGlobal comparison of light use efficiency models for simulating terrestrial vegetation gross primary production based on the LaThuile database
Yuan, W.; Cai, W.; Xia, J. et al

in Agricultural and Forest Meteorology (2014), 192-193

Simulating gross primary productivity (GPP) of terrestrial ecosystems has been a major challenge in quantifying the global carbon cycle. Many different light use efficiency (LUE) models have been ... [more ▼]

Simulating gross primary productivity (GPP) of terrestrial ecosystems has been a major challenge in quantifying the global carbon cycle. Many different light use efficiency (LUE) models have been developed recently, but our understanding of the relative merits of different models remains limited. Using CO2 flux measurements from multiple eddy covariance sites, we here compared and assessed major algorithms and performance of seven LUE models (CASA, CFix, CFlux, EC-LUE, MODIS, VPM and VPRM). Comparison between simulated GPP and estimated GPP from flux measurements showed that model performance differed substantially among ecosystem types. In general, most models performed better in capturing the temporal changes and magnitude of GPP in deciduous broadleaf forests and mixed forests than in evergreen broadleaf forests and shrublands. Six of the seven LUE models significantly underestimated GPP during cloudy days because the impacts of diffuse radiation on light use efficiency were ignored in the models. CFlux and EC-LUE exhibited the lowest root mean square error among all models at 80% and 75% of the sites, respectively. Moreover, these two models showed better performance than others in simulating interannual variability of GPP. Two pairwise comparisons revealed that the seven models differed substantially in algorithms describing the environmental regulations, particularly water stress, on GPP. This analysis highlights the need to improve representation of the impacts of diffuse radiation and water stress in the LUE models. © 2014 Elsevier B.V. [less ▲]

Detailed reference viewed: 32 (2 ULg)
Full Text
Peer Reviewed
See detailGlobal comparison of magnetospheric ion fluxes and auroral precipitation during a substorm
Mende, S. B.; Frey, H. U.; Immel, T. J. et al

in Geophysical Research Letters (2002), 29

Integrated fluxes from global images taken by the High Energy Neutral Atom (HENA) and the far ultraviolet (FUV) imagers on the IMAGE spacecraft were compared for a six-hour period, during which a ... [more ▼]

Integrated fluxes from global images taken by the High Energy Neutral Atom (HENA) and the far ultraviolet (FUV) imagers on the IMAGE spacecraft were compared for a six-hour period, during which a reasonably intense substorm occurred. HENA and the FUV proton auroral imager (SI-12) monitor emissions which are representative of trapped and precipitating magnetospheric proton fluxes, respectively. For several hours prior to substorm onset, measurements of the fluxes of lower energy (10-16 and 16-27 keV) magnetospheric Energetic Neutral Atoms (ENA-s) by HENA and precipitating auroral protons by FUV SI-12 show strong similarities, with the implication that, in general, proton precipitation is controlled by a steady pitch angle diffusion process. Less similarity is seen between ENA-s and the auroral electron precipitation, which is monitored with the FUV Wideband Imaging Camera. Prior to substorm onset, ENA intensity at large radial distance (L > 8) is reduced while the overall integrated ENA flux increases signifying earthward motion and accumulation of the plasma. About 20 minutes before onset, the auroral fluxes decrease while the ENA intensity continues to grow. The observations are consistent with a pre-onset increase in plasma pressure in the inner magnetosphere without an increase in precipitation showing more efficient trapping perhaps by the distorted nightside magnetosphere. At substorm onset the increase in precipitation intensity is very sudden while the more gradual intensification of the energetic ENA-s continues. At onset the electron aurora shows an increase in intensity of one order of magnitude, while the increase in precipitating proton flux is only 50%. The intensification of the precipitation is relatively short lived (~10 minutes) while the ENA substorm enhancements last about an hour. [less ▲]

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
See detailGlobal compartmental analysis of the fluorescence decay surface of the halato telechelic polymer (N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)-trifluoro-methanesulfonate-end-capped poly(tetrahydrofuran
Hermans, Bart; De Schryver, Frans C; Van Stam, Jan et al

in Macromolecules (1995), 28(9), 3380-3386

The kinetic behavior of the halato telechelic polymer (N,N-dimethyl-N-[3-(1-pyrenyl)propyl]-ammonio)trifluoromethanesulfonate-end-capped poly(tetrahydrofuran) (POLYPROBE) in tetrahydrofuran is ... [more ▼]

The kinetic behavior of the halato telechelic polymer (N,N-dimethyl-N-[3-(1-pyrenyl)propyl]-ammonio)trifluoromethanesulfonate-end-capped poly(tetrahydrofuran) (POLYPROBE) in tetrahydrofuran is investigated by global compartmental analysis of the fluorescence decay surface. At low POLYPROBE concentrations the emission decays monoexponentially. When an analogous end-capped halato telechelic polymer without the pyrene chromophore ((N,N,N-triethylammonio)trifluoromethanesulfonate-end-capped poly(tetrahydrofuran), POLYSALT) is added to solutions containing a low POLYPROBE concentration, the emission can be fitted by a biexponential decay function. From these observations it is concluded that the second excited-state species in the POLYPROBE-POLYSALT system is POLYPROBE involved in ion aggregation due to dipole-dipole or ion-dipole interaction. At higher POLYPROBE concentrations, without added POLYSALT, a triexponential decay function is needed to describe the emission. The third excited-state species is POLYPROBE excimer, which can be formed via two pathways: either intermolecularly when a locally excited POLYPROBE encounters a ground-state POLYPROBE or intramolecularly when an aggregate of two POLYPROBE molecules rearranges. From the global compartmental analysis in which the value of one of the rate constants is scanned, it is found that the bimolecular processes are slowed down by the presence of the polymer chain, while intramolecular rearrangements are not affected. [less ▲]

Detailed reference viewed: 45 (1 ULg)
Full Text
Peer Reviewed
See detailGlobal democratic consensus on neuropathological disease criteria.
Achim, Cristian; Auer, Roland; Bergeron, Catherine et al

in Lancet Neurology (2002), 1(6), 340

Detailed reference viewed: 27 (1 ULg)
Full Text
Peer Reviewed
See detailGlobal design of hydraulic structures optimised with physically based flow solvers on multiblock structured grids
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Proceedings of the 9th International Symposium on River Sedimentation (2004)

This paper presents the numerical studies lead by the Laboratory of Applied Hydrodynamics and Hydraulic Constructions of the University of Liège (HACH) for the rehabilitation of the 21-meter high ... [more ▼]

This paper presents the numerical studies lead by the Laboratory of Applied Hydrodynamics and Hydraulic Constructions of the University of Liège (HACH) for the rehabilitation of the 21-meter high Nisramont dam in Belgium. After determination of the up-to-date 1000-year return flood using the hydrological runoff model WOLFHYDRO on the global 74,000 ha watershed real topography coupled with statistical analyzes, and after validation on the existing situation and for extreme observed events, the 2D finite volume multiblock flow solver WOLF2D has been applied to the design of the new stilling basin and to the bottom outlet rehabilitation impact study. The multiblock solver possibilities allow mesh refinement close to interesting areas, such as dam spillway and stilling pool, without leading to prohibitive CPU times, while suitable shallow water equations formulation allows the computation of the flows on the strongly vertically curved bottom of the spillway. In the described simulation, 270,000 structured finite volumes, from .25 to 1 meters long, are used to simulate as a whole the flows in the upstream reservoir, dam, spillway, stilling basin and downstream river, this on a real topography. [less ▲]

Detailed reference viewed: 78 (2 ULg)
Peer Reviewed
See detailThe global distribution of nitric oxide in the thermosphere as determined by the Atmosphere Explorer D satellite
Cravens, T. E.; Gérard, Jean-Claude ULg; Lecompte, M. et al

in Journal of Geophysical Research (1985), 90

The ultraviolet nitric oxide spectrometer (UVNO) experiment on the Atmosphere Explorer D (AE-D) satellite measured thermospheric nitric oxide during the winter of 1974-1975 using resonant fluorescence ... [more ▼]

The ultraviolet nitric oxide spectrometer (UVNO) experiment on the Atmosphere Explorer D (AE-D) satellite measured thermospheric nitric oxide during the winter of 1974-1975 using resonant fluorescence from the 1-0 gamma band of the molecule. Almost complete latitude coverage was obtained, but the observations were confined to morning local times close to 0900. The 1-0 gamma band intensity profiles measured by the instrument were inverted to provide vertical profiles of the NO number density between about 90 and 200 km. Typically, the measured NO concentrations reached a maximum between altitudes of 100 and 110 km, and more NO was observed at higher latitudes than at low latitudes, in agreement with previous observational studies. The shape of the NO profile was also found to be a function of latitude, with a plateau appearing in the profile near 130 km for low latitudes and mid-latitudes in the winter hemisphere. [less ▲]

Detailed reference viewed: 28 (0 ULg)
Peer Reviewed
See detailThe global distribution of thermospheric odd nitrogen for solstice conditions during solar cycle minimum
Gérard, Jean-Claude ULg; Roble, R. G.; Rusch, D. W. et al

in Journal of Geophysical Research (1984), 89

A two-dimensional model of odd nitrogen in the thermosphere and upper mesosphere is described. The global distributions of nitric oxide and atomic nitrogen are calculated for the solstice period for quiet ... [more ▼]

A two-dimensional model of odd nitrogen in the thermosphere and upper mesosphere is described. The global distributions of nitric oxide and atomic nitrogen are calculated for the solstice period for quiet and moderate magnetic activity during the solar minimum period. The effect of thermospheric transport by winds is investigated along with the importance of particle-induced ionization in the auroral zones. The results are compared with rocket and satellite measurements, and the sensitivity of the model to eddy diffusion and neutral winds is investigated. Downward fluxes of NO into the mesosphere are given, and their importance for stratospheric ozone is discussed. The results show that the summer-to-winter pole meridional circulation transports both NO and N(S-4) across the solar terminator into the polar night region where there is a downward vertical transport toward the mesosphere. The model shows that odd nitrogen densities at high winter latitudes are entirely controlled by particle precipitation and transport processes. [less ▲]

Detailed reference viewed: 11 (1 ULg)
See detailGlobal distributions of upper ocean CO2 and O2
Monfray, P.; Orr, J.; Stoens, A. et al

Conference (1999)

Detailed reference viewed: 3 (0 ULg)
Full Text
See detailThe global grid for empowering renewable energy
Ernst, Damien ULg

Speech/Talk (2015)

Detailed reference viewed: 75 (2 ULg)