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See detailModelling the Cape Ghir Upwelling Filament
Troupin, Charles ULg

Scientific conference (2008, December 12)

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See detailModelling the cardiovascular system
Shaw, G. M.; Chase, J. G.; Starfinger, C. et al

in Critical Care and Resuscitation : Journal of the Australasian Academy of Critical Care Medicine (2007), 9(3), 264-269

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See detailModelling the Cenozoic evolution of atmospheric CO2
François, Louis ULg; Gaillardet, J.; Godderis, Y.

in Geochimica et Cosmochimica Acta (2002), 66(15A), 243-243

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See detailModelling the climate effect on Black Grouse Population Dynamic in Rhön Biopshere Reserve
Loneux, Michèle ULg; Kolb, Karl-Heinz; Lindsey, James ULg

in Plummer, Ron (Ed.) Black Grouse Endangered Species (2005, December)

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See detailModelling the Climatic Response to Solar Variability
Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution ... [more ▼]

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution models, the solar luminosity has increased steadily by 25-30% over the past 4 × 10[SUP]9[/SUP] years. Periodic variations are also suspected with characteristic timescales of 11 or 22 years, 80-90 years and possibly longer periods. The ultraviolet radiation below 300 nm also exhibits significant changes over the 27-day solar rotation period as well as the 11-year solar cycle. Variations in the solar constant are expected to produce both direct and indirect (feedback) perturbations in the global surface temperature. A hierarchy of zero- to three-dimensional models have been used to study the complex couplings involved by such effects. The response of a zonally averaged model to possible total irradiance changes associated with the Gleissberg cycle is investigated and compared with measurements of the sea-surface temperature made since 1860. Changes in the solar ultraviolet irradiance modulate the amount and distribution of atmospheric ozone, which is predicted to change by several percent in the stratosphere. These perturbations directly affect the middle atmospheric thermal structure, but may also generate indirect effects that could possibly account for some short-term geophysical signatures of solar activity. The cycle-modulated energetic particle interaction with the middle atmosphere is also a possible source of global climatic perturbations. [less ▲]

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See detailModelling the climatic response to solar variability.
Gérard, Jean-Claude ULg

in The Earth's Climate and Variability of the Sun over Recent Millennia: Geophysical, Astronomical and Archaeological Aspects (1990)

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of ... [more ▼]

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of the possible temperature signature of the Gleissberg solar cycle and climatic effects of ultraviolet irradiance variations and intense solar charged particle interaction with the Earth's atmosphere. [less ▲]

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See detailModelling the Climatic Response to Solar Variability: Discussion
Pecker, J*-C; Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

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See detailModelling the Coastal Ocean’s Complex Ecohydrodynamics. A case study; the Northern Bering Sea
Nihoul, Jacques ULg; Adam, Paul; Djenidi, Salim ULg et al

in Progress in Belgian Oceanographic Research (1993)

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See detailModelling the competition between two phytoplanktonic species
Elkafazi, Abderahman; Djenidi, Salim ULg; Nihoul, Jacques ULg

in Bulletin de la Société Royale des Sciences de Liège (1996), 65

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See detailModelling the components of binaries in the Hyades: the dependence of the mixing-length parameter on stellar mass
Yıldız, M.; Yakut, K.; Bakış, H. et al

in Monthly Notices of the Royal Astronomical Society (2006), 368(4), 1941-1948

We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to ... [more ▼]

We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to observations so as to give the observed total V and B-V of that system and the observed slope of the main sequence in the corresponding parts. According to our findings, there is a very definite relationship between the mixing-length parameter and the stellar mass. The fitting formula for this relationship can be given as α= 9.19(M/M[SUB]solar[/SUB]- 0.74)[SUP]0.053[/SUP]- 6.65, which is valid for stellar masses greater than 0.77M[SUB]solar[/SUB]. While no strict information is gathered for the chemical composition of the cluster, as a result of degeneracy in the colour-magnitude diagram, by adopting Z= 0.033 and using models for the components of 70 Tau and θ[SUP]2[/SUP] Tau we find the hydrogen abundance to be X= 0.676 and the age to be 670 Myr. If we assume that Z= 0.024, then X= 0.718 and the age is 720 Myr. Our findings concerning the mixing-length parameter are valid for both sets of the solution. For both components of the active binary system V818 Tau, the differences between radii of the models with Z= 0.024 and the observed radii are only about 4 per cent. More generally, the effective temperatures of the models of low-mass stars in the binary systems studied are in good agreement with those determined by spectroscopic methods. [less ▲]

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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Conference (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

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See detailModelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie ULg; Hambuckers, Alain ULg; Trolliet, Franck ULg et al

Poster (2014, April)

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are ... [more ▼]

The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project (“Sustainability of tropical forest biodiversity and services under climate and human pressure”), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land cover (potential or human-induced). First, we show simulations over the whole Congo basin at a 0.5◦ spatial resolution. Then, we present high-resolution simulations (1 km) carried out over different areas of the Congo basin, notably the DRC part of the WWF Lake Tele – Lake Tumba Landscape. Studied in the BIOSERF project, this area is characterized by a forest-savannah mosaic but also by swamp and flooded forest. In addition, forward transient projections of the model driven with the outputs of about thirty global cli- mate models (GCMs) from the new Coupled Model Intercomparison Project Phase 5 (CMIP5) will permit to outline the likely response of carbon pools to changing climate over the Congo basin during the 21th century. [less ▲]

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See detailModelling the Danube-influenced North-western continental shelf of the Black Sea. I: Hydrodynamical processes simulated by 3-D and box models
Beckers, Jean-Marie ULg; Grégoire, Marilaure ULg; Nihoul, Jacques ULg et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 453-472

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of ... [more ▼]

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of general circulation in the Black Sea are highlighted. Compared with a coarse resolution model, forced with the same climatic monthly averaged atmospheric data, the high resolution model exhibits stronger variability, including frontal structures and coastal upwellings induced by baroclinic instabilities, in particular along the Turkish coast. A comparison of the shelf-open sea exchanges, with particular focus on the cold intermediate waters, shows that both models lead to a replenishment of the CIL in the basin interior by cold waters formed on the shelf. Due to the better representation of frontal structures, the high resolution model is an appropriate candidate for coupling with a biological model. Problems of calibration, interpretation and data availability typically arise from this kind of coupled 3-D model. In order to overcome such difficulties, the results of the 3-D hydrodynamical model are used to guide the development of an integrated 0-D box model capable of achieving the objectives of projects like EROS21, where the effect of changes in the Danube inflows on the shelf ecosystem is investigated. The 0-D model is thus designed to cover this region and is obtained through integration over an appropriate variable volume. The integration procedure shows where the weaknesses of an 0-D approach might lie. Diagnoses in the 3-D model of the integral quantities show the range of uncertainty one can expect in the exchange laws of the 0-D model. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling the Danube-influenced north-western continental shelf of the Black Sea. II: Ecosystem response to changes in nutrient delivery by the Danube River after its damming in 1972
Lancelot, Christiane; Staneva, J.; Van Eeckhout, D. et al

in Estuarine Coastal & Shelf Science (2002), 54(3), 473-499

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has ... [more ▼]

The ecological model BIOGEN, describing the carbon, nitrogen, phosphorus and silicon cycling throughout aggregated chemical and biological compartments of the planktonic and benthic marine systems, has been implemented in the north-western Black Sea to assess the response of this coastal ecosystem to eutrophication by the Danube River. The trophic resolution of BIOGEN was chosen to simulate the major ecological changes reported in this coastal area since the 1960s. Particular attention was paid to establishing the link between quantitative and qualitative changes in nutrients, phytoplankton composition and food-web structures. The BIOGEN numerical code structure includes 34 state variables assembled in five interactive modules describing the dynamics of (1) phytoplankton composed of three distinct groups, each with a different trophic fate (diatoms, nanophytoflagellates, non-silicified opportunistic species); (2) meso- and microzooplankton; (3) trophic dead-end gelatinous organisms composed of three distinct groups (the omnivorous Noctiluca and the carnivores Aurelia and the alien Mnemiopsis), and organic matter degradation and associated nutrient regeneration processes by (4) planktonic and (5) benthic bacteria. The capability of the BIOGEN model to simulate the recent ecosystem changes reported for the Black Sea was demonstrated by running the model for the period 1985-1995. The BIOGEN code was implemented in an aggregated and simplified representation of the north-western Black Sea hydrodynamics. The numerical frame consisted of coupling a 0-D BIOGEN box model subjected to the Danube with a 1-D BIOGEN representing the open-sea boundary conditions. Model results clearly showed that the eutrophication-related problems of the north-western Black Sea were not only driven by the quantity of nutrients discharged by the Danube, but that the balance between them was also important. BIOGEN simulations clearly demonstrated that phosphate, rather than silicate, was the limiting nutrient driving the structure of the phytoplankton community and the planktonic food-web. In particular, it showed that a well-balanced N:P:Si nutrient enrichment, such as that observed in 1991, had a positive effect on the linear, diatom-copepod food-chain, while the regenerated-based microbial food-chain remained at its background level. When present, the gelatinous carnivores also benefited from this enrichment throughout their feeding on copepods. A synergetic effect of fishing pressure and cultural eutrophication was further indirectly suggested by modifying the mortality coefficient of copepods. However, BIOGEN scenarios with unbalanced nutrient inputs, such as nitrogen or phosphate deficiency recorded in 1985 and 1995, predicted the dominance of an active microbial food-web in which bacteria and microzooplankton played a key role; the former as nutrient regenerator, the latter as a trophic path to the copepods and hence to the carnivorous. In such conditions, however, a significant biomass reduction of all gelatinous organisms was simulated, in perfect agreement with recent observations. From these model scenarios it is suggested that the observed positive signs of Black Sea ecosystem recovery might well be related to the reduction of nutrient loads in particular phosphate, by the Danube. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailModelling the development of potential spoilage and biopreservative microorganisms on precooked pasta in different conditions of temperature based on classical microbiology and 16S rDNA metagenomic
Gand, Mathieu ULg; Cargnel, Mickaël ULg; Kergourlay, Gilles ULg et al

Poster (2014, September)

An important way to prevent the spoilage of food is the respect of the cold chain during the storage. While the temperature instructions are generally respected during process and distribution of food ... [more ▼]

An important way to prevent the spoilage of food is the respect of the cold chain during the storage. While the temperature instructions are generally respected during process and distribution of food products, it is not always the case with the consumers. Indeed, a few persons reach the right temperature level required for a safe storage of foodstuffs in their refrigerator. Besides, the food can sometimes spend a few hours in ambient temperature between the buying in the supermarket and the storage in cold temperature. In this study, we propose to model the growth of microorganisms on precooked pasta, stored in different conditions of temperature that reflect the situations described above (constant 4°C, constant 8°C, constant 12°C, 1/3 4°C – 2/3 8°C, 1/3 4°C – breach during 4h at 20°C – 2/3 8°C and 1/3 8°C – breach during 4h at 20°C – 2/3 8°C. The product was surface inoculated with potential spoilage and biopreservative strains (Lactococcus piscium, Leuconostoc mesenteroides and Leuconostoc citreum). Analyses by classical microbiology and V1-V3 16S rDNA metagenomics were done each day until the out of date of the food matrix. The transition from 4 to 8°C and the breach at 20°C during 4h have clearly boosted the growth of the microorganisms. The metagenomic analysis was a powerful tool to follow separately each population in each condition of storage. The results of this communication show the importance of keeping the foodstuffs in 4°C or lower in the refrigerator with the goal to avoid the spoilage or the development of pathogens and the potential of metagenomics for selection of biopreservative strains. [less ▲]

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See detailModelling the development of potential spoilage and biopreservative microorganisms on white pudding in different conditions of temperature based on classical microbiology and 16S rDNA metagenomic
Gand, Mathieu ULg; Cauchie, Emilie ULg; Kergourlay, Gilles ULg et al

Poster (2014, September)

An important way to prevent the spoilage of food is the respect of the cold chain during the storage. While the temperature instructions are generally respected during process and distribution of food ... [more ▼]

An important way to prevent the spoilage of food is the respect of the cold chain during the storage. While the temperature instructions are generally respected during process and distribution of food products, it is not always the case with the consumers. Indeed, a few persons reach the right temperature level required for a safe storage of foodstuffs in their refrigerator. Besides, the food can sometimes spend a few hours in ambient temperature between the buying in the supermarket and the storage in cold temperature. In this study, we propose to model the growth of microorganisms on white pudding, stored in different conditions of temperature that reflect the situations described above (constant 4°C, constant 8°C, constant 12°C, 1/3 4°C – 2/3 8°C, 1/3 4°C – breach during 4h at 20°C – 2/3 4°C and 1/3 4°C – breach during 4h at 20°C – 2/3 8°C. The product was surface inoculated with potential spoilage and biopreservative strains (Raoultella terrigena, Serratia quinivorans, Carnobacterium maltaromaticum, Lactobacillus oligofermentans, Lactobacillus nenjiangensis, Lactobacillus fuchuensis, Leuconostoc mesenteroides, lactococcus lactis and Lactobacillus graminis). Analyses by classical microbiology and V1-V3 16S rDNA metagenomics were done each day until the out of date of the food matrix. The transition from 4 to 8°C and the breach at 20°C during 4h have clearly boosted the growth of the microorganisms. The metagenomic analysis was a powerful tool to follow separately each population in each condition of storage. The results of this communication show the importance of keeping the foodstuffs in 4°C or lower in the refrigerator with the goal to avoid the spoilage or the development of pathogens and the potential of metagenomics for selection of biopreservative strains. [less ▲]

Detailed reference viewed: 194 (6 ULg)