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See detailTowards the production of carbon xerogel monoliths by optimizing convective drying conditions
Job, Nathalie ULg; Sabatier, Françoise; Pirard, Jean-Paul ULg et al

in Carbon (2006), 44(12), 2534-2542

Resorcinol-formaldehyde hydrogels prepared at various resorcinol/sodium carbonate ratios, R/C, were convectively air dried. The influence of the drying operating conditions, i.e. air temperature and ... [more ▼]

Resorcinol-formaldehyde hydrogels prepared at various resorcinol/sodium carbonate ratios, R/C, were convectively air dried. The influence of the drying operating conditions, i.e. air temperature and velocity, on the pore texture, shrinkage and cracking of the dried gels were investigated. Shrinkage was found to be isotropic. The shrinkage behaviour and the textural properties of the gels are independent of the drying operating conditions, but are completely determined by the value of the synthesis variables. The analysis of the drying kinetics shows two main drying periods. During the first phase, shrinkage occurs and the external surface of the material remains completely wet: heat and mass transfers are limited by external resistances located in a boundary layer. When shrinkage stops, the second period begins: the evaporation front recedes inside the solid and internal transfer limitations prevail. The drying time can be reduced by increasing the air temperature and/or velocity, but the temperature increase is limited when monolithicity is required, especially when the pores are small. For example, at a temperature of 160 degrees C and a velocity of 2 m/s, about 1 h is needed to dry a 2.8 cm in diameter and 1 cm in height cylinder containing macropores (pore width > 50 nm after drying). The same cylinder presenting small mesopores (pore width = 10-15 nm after drying) requires 20 h at 30 degrees C and 2 m/s to reach complete dryness without the development of cracks. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailComparaison de techniques de validation dynamique de données
Heyen, Georges ULg; Gerkens, Carine ULg; Mateus, Miguel et al

(2006, October)

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See detailThe XMM large scale structure survey: properties and two-point angular correlations of point-like sources
Gandhi, P.; Garcet, Olivier ULg; Disseau, L. et al

in Astronomy and Astrophysics (2006), 457(2), 393-404

We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5-2 keV and 2-10 keV bands down to fluxes of 2× 10[SUP]-15[/SUP] and 8× 10[SUP]-15[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP ... [more ▼]

We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5-2 keV and 2-10 keV bands down to fluxes of 2× 10[SUP]-15[/SUP] and 8× 10[SUP]-15[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] respectively, as part of the XMM-Newton Large Scale Structure Survey. The log N-log S in both bands shows a steep slope at bright fluxes, but agrees well with other determinations below ~2 × 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP]. The detected sources resolve close to 30 per cent of the X-ray background in the 2-10 keV band. We study the two-point angular clustering of point sources using nearest neighbours and correlation function statistics and find a weak, positive signal for ~1130 sources in the 0.5-2 keV band, but no correlation for ~400 sources in the 2-10 keV band below scales of 100 arcsec. A sub-sample of ~200 faint sources with hard X-ray count ratios, that is likely to be dominated by obscured AGN, does show a positive signal with the data allowing for a large angular correlation length, but only at the ~2 (3)sigma level, based on re-sampling (Poisson) statistics. We discuss possible implications and emphasize the importance of wider, complete surveys in order to fully understand the large scale structure of the X-ray sky. [less ▲]

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See detailL'image du mois. Une malformation uterine evoquant une masse annexielle
Wauters, Odile ULg; Pintiaux, Axelle ULg; Foidart, Jean-Michel ULg et al

in Revue Médicale de Liège (2006), 61(10), 665-6

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See detailPréparation aux cliniques: examen neurologique de l'enfant
Battisti, Oreste ULg

Learning material (2006)

présentation pratique des symptomes et signes de l'examen neurologique chez l'enfant

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See detailTeashirt 3 expression in the chick embryo reveals a remarkable association with tendon development
Manfroid, Isabelle ULg; Caubit, Xavier; Marcelle, Christophe et al

in Gene Expression Patterns (2006), 6(8), 908-912

Drosophila teashirt (tsh) is involved in the patterning of the trunk identity together with the Hox genes. In addition, it is also a player in the Wingless and the Hedgehog pathways. In birds and mammals ... [more ▼]

Drosophila teashirt (tsh) is involved in the patterning of the trunk identity together with the Hox genes. In addition, it is also a player in the Wingless and the Hedgehog pathways. In birds and mammals, three Tshz genes are identified and the expression patterns for mouse Tshz1 and Tshz2 have been reported during embryogenesis. Recently, we showed that all three mouse Tshz genes can rescue the Drosophila tsh loss-of-function phenotype, indicating that the function of the teashirt genes has been conserved during evolution. Here we describe the expression pattern of chick TSHZ3 during embryogenesis. Chick TSHZ3 is expressed in several tissues including mesodermal derivatives, the central and peripheral nervous systems. Emphasis is laid on the dynamic expression occurring in regions of the somites and limbs where tendons develop. We show that TSHZ3 is activated in the somites by FGF8, a known inducer of the tendon marker SCX. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailA new technique of stereotactic permanent breast seed implantation
Jansen, Nicolas ULg; Nickers, Philippe ULg

in Radiotherapy & Oncology (2006, October), 81(Suppl. 1), 249-250

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See detailVALIDATION ANALYTIQUE DE LA TROUSSE OCTEIA 25-HYDROXYVITAMINE D (IDS).
Cavalier, Etienne ULg; Levaux, Laetitia ULg; Carlisi, Ignazia ULg et al

in Immuno-Analyse & Biologie Spécialisée [=IBS] (2006, October)

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See detailStatistique et progrès : un mariage heureux ou une cohabitation difficile ?
Claustriaux, Jean-Jacques ULg

in Probio-Revue des Professeurs de biologie (2006), 29(1), 47-58

Présentation d'exemples multidisciplinaires en statistique appliquée.

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See detailEmpirical regression models using NDVI, rainfall and temperature data for the early prediction of wheat grain yields in Morocco
Balaghi, Riad; Tychon, Bernard ULg; Eerens, H. et al

Conference (2006, October)

In Morocco, no operational system actually exists for the early prediction of the grain yields of bread wheat. This study proposes empirical Ordinary Least Squares regression models to forecast the yields ... [more ▼]

In Morocco, no operational system actually exists for the early prediction of the grain yields of bread wheat. This study proposes empirical Ordinary Least Squares regression models to forecast the yields at provincial and national levels. The predictions were based on dekadal (10-daily) NDVI/AVHRR, dekadal rainfall sums and average monthly air temperatures. The global land cover map GLC2000 was used to select only the NDVI pixels that are related to agricultural lands. Provincial yields were assessed with errors varying from 80 to 762 kg.ha-1, depending on the province. At national level, yield was predicted at the third dekad of April with 73 kg.ha-1 error, using NDVI and rainfall. However, earlier forecasts are possible, starting from the second dekad of March with 84 kg.ha-1 error. At the province and country levels most of the yield variation was accounted for by NDVI. The proposed models can be used in an operational context to forecast bread wheat yields in Morocco. [less ▲]

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See detailDownscaling of ECMWF grid meteorological data : comparison with ground stations and validation
Tychon, Bernard ULg; Horion, Stéphanie

Conference (2006, October)

CGMS currently operates on observed station data. Switching from this classical approach to a modelled data from European Centre for Medium-range Weather Forecast, ECMWF, has to be tested before applying ... [more ▼]

CGMS currently operates on observed station data. Switching from this classical approach to a modelled data from European Centre for Medium-range Weather Forecast, ECMWF, has to be tested before applying it operationally. In this study, we concentrated on the impact of the downscaling of meteorological data with grid sizes ranging from 1.875 to 0.35 degrees to the new CGMS grid size of 25 X 25 km. Four different grid sizes corresponding respectively to the dimensions of the Operational, EPS, Monthly and Seasonal ECMWF Models were checked. The control was done on daily data of 25 stations selected on a 2-year period in a window covering the South of Germany and Czech Republic, a large part of Austria and the North of Italia in order to analyse the downscaling impact on plains, mountainous and coastal zones. For each grid size, four different downscaling methods were applied: the reference method that uses the classical CGMS interpolation procedure, the nearest neighbour approach, and two more complicated interpolation techniques using the Model Output Statistics developed by Meteo Consult (MC-MOS). The analysis showed that the accuracy of the downscaling procedure is largely influenced by the input data grid size. RMSE increases between the smallest and the largest grids are respectively 59%, 51%, 33%, and 33% for Tmax, Tmin, Wind Speed and Radiation fields. Rainfall does not seem to be affected by the downscaling process but the RMSE is high in all cases. In most cases, the best interpolation method is also the more complex one and the one that requires more computer time to be calculated. RMSE decrease of 22%, 50%, 57% and 28% respectively for Tmax, Tmin, Wind speed and Radiation fields when we compare the best interpolation method results with the reference approach. An exception in this general rule is for the rainfall rate estimation whose accuracy is not always best with the most complex interpolation technique. [less ▲]

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See detailThe B-CGMS project : evaluation after 5 years of monitoring and prediction
Curnel, Y.; Oger, Robert ULg; Leteinturier, B. et al

Conference (2006, October)

The B-CGMS project, started in 1998, is the adaptation to Belgian Conditions of the European Crop Growth Monitoring System (CGMS). This project involved 3 Belgian scientific institutes: the Walloon ... [more ▼]

The B-CGMS project, started in 1998, is the adaptation to Belgian Conditions of the European Crop Growth Monitoring System (CGMS). This project involved 3 Belgian scientific institutes: the Walloon agricultural research Centre (CRA-W), the Flemish Institute for Technological Research (VITO) and the University of Liège (ULg). The main difference with the European system is that more detailed inputs (meteorological, soil and NUTS inputs) are used. Crop yields predictions are realised on a monthly basis during the growing season (from April to September) for 6 crops (winter wheat, winter barley, maize, Potato, sugar beet, winter rapeseed). Yields predictions as well as analyses of meteorological situation of the month and RS information on the state of the crops are published in agrometeorological bulletins sent by e-mail since 2002. The information is also available on the Internet website of the project (http://.b-cgms.cra.wallonie.be). Crop yields predictions are produced through a combination of linear regression models which may include different categories of yield indicators (trend, meteo, RS and agrometeorological model outputs). Crop yields predictions procedure is currently semi-automated by the use of a statistical calibration toolbox (StatCaT). The evaluation of the project after 5 years of monitoring and prediction has first shown that final yields predicted B-CGMS as well as the ones predicted by MARS are coherent compared with official yields: no significant differences are observed. As far as the accuracy according to the month for which the prediction is made is concerned, we can notice that at agricultural circumscriptions level and for winter crops a lower precision of B-CGMS is observed before June and that there is no improvement in July (in comparison with June). The same evolution is observed for summer crops before July but in August and September, the prediction accuracy decreases. Even if calibration models present high adjusted coefficient of determination, the technological trend explains an important part of the variability and it is therefore necessary to consider the effect of a year factor on the quality of prediction in order to clearly the interest of the agrometeorological model. For some crops (as potato), adding agrometeorological yield outputs to models including already the technological trend allow to improve the quality of prediction especially for “extreme” year i.e. years where official yields move away significantly from the technological trend. For others crops as winter wheat, this improvement of the quality of prediction is not observed. However, fortunately, adding other yield indicators as meteo indicators can improve in general the quality of prediction and once again especially for “extreme” years. [less ▲]

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See detailMonitoring of the crop water stress in Belgium. The case of the 2003 heat wave.
Horion, Stéphanie; Tychon, Bernard ULg; De Longueville, Florence ULg

Conference (2006, October)

In this paper the crop water stress is evaluated with three different indices: (i) the Relative Soil Moisture Index [RSMI] resulting from agrometeorological model simulations, (ii) the Normalized ... [more ▼]

In this paper the crop water stress is evaluated with three different indices: (i) the Relative Soil Moisture Index [RSMI] resulting from agrometeorological model simulations, (ii) the Normalized Difference Vegetation Index, [NDVI] applied on S10 SPOT-VGT imagery, (iii) the Normalized Difference Water Index, [NDWI] applied on S10 SPOT-VGT imagery. The RSMI is one of the outputs of the Belgian Crop Growth Monitoring System. It indicates the soil water availability for crops. Crop water stress is assumed when soil water availability is lower than the crop potential evapotranspiration. One of the potential applications for drought monitoring is the calculation of the number of days with a crop water stress during the growing season or more precisely during the “moisture-sensitive period” of the crop. The two others (well-known) indices are derived from low resolution satellite imagery. Complete time series of S10 SPOT-VGT NDVI and NDWI data - i.e. from April 1998 onwards – have been acquired for the research. Using spatial information on land-uses in Belgium, a simple unmixing method is implemented to partly reduce the problem of mixed values occurring inevitably in 1x1km² pixels. Only the most agricultural pixels are considered for the analysis. The heat wave occurred during the summer 2003 has been chosen as a study case for the comparison. This summer was particularly hot, dry and sunny with the highest averaged temperature ever recorded from June to August in Uccle-Belgium. Many human activities were affected by this particular climatic condition, among which agriculture. In order to make the comparison possible, a standardization of the outputs of the 3 indexes is realised, taking into account the times series of each indexes. Moreover all the outputs are aggregated at municipality level. [less ▲]

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See detailGreen leaf area decline of wheat top three leaves in Belgium and G-D of Luxembourg from 2003 to 2006 : the relationships with grain yield.
Martin, B.; Tychon, Bernard ULg; El Jarroudi, Moussa ULg et al

Conference (2006, October)

The modified Gompertz model developed by Gooding et al. (2000) was used to describe the decline in green area of wheat top three leaves in field experiments where green leaf area at time t = 100*exp[-exp ... [more ▼]

The modified Gompertz model developed by Gooding et al. (2000) was used to describe the decline in green area of wheat top three leaves in field experiments where green leaf area at time t = 100*exp[-exp(-k*(t-m))]. In the absence of fungicide, green leaf area decline was associated with drought or infection with a number of foliar pathogens including Septoria tritici (sexual stage Mycospherella graminicola) and Puccinia recondita f.sp. tritici and Erysiphe graminis. On the whole experiments and cultivars there was no effect of fungicide on k but it was highly significant on m (P<0.001). When main effects are considered, fungicide delayed green leaf area decline rather than reduced its rate of progress once started. Fungicide had variable effects on grain yield, largely reflecting variation in disease infection pressures in the different years and susceptibility of the different cultivars. If no correlation was observed between k values and grain yields, m was at the contrary very closely associated with grain yields. This study supports the view of Gooding (2000) and Gaunt (1995) that, for many diseases, effects on green area duration give an adequate estimate of host yield reduction. Therefore we have use the close relationship between the parameter m of the Gompertz model and grain yield to improve the Belgium-Crop Growth Monitoring System (B-CGMS) by recalibrating LAI evolution simulated by B-CGMS according to the evolution of LAI derived from the Gompertz model. The system includes indeed a component allowing taking into account senescence in the evolution of LAI during the growing season. Recalibration has been realized through the modification of one of the parameters influencing the leaf senescence, the SPAN parameter. Modifying the SPAN parameter comes down to modify the lifespan of leaves. Considering that parasitic pressure reduces leaves lifespan and therefore the photosynthetic capacity, this approach makes it possible to take into account the influence of this pressure on yield predictions in the Belgian Crop Growth Monitoring System. [less ▲]

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See detailMonitoring of the crop water stress in Belgium. The case of the 2003 heat wave.
Horion, Stephanie; Tychon, Bernard ULg; De Longueville, Florence ULg

Conference (2006, October)

In this paper the crop water stress is evaluated with three different indices: (i) the Relative Soil Moisture Index [RSMI] resulting from agrometeorological model simulations, (ii) the Normalized ... [more ▼]

In this paper the crop water stress is evaluated with three different indices: (i) the Relative Soil Moisture Index [RSMI] resulting from agrometeorological model simulations, (ii) the Normalized Difference Vegetation Index, [NDVI] applied on S10 SPOT-VGT imagery, (iii) the Normalized Difference Water Index, [NDWI] applied on S10 SPOT-VGT imagery. [less ▲]

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See detailLa recherche et le développement en Europe dans le domaiine de la qualité et de la technologie de la viande et des produits carnés
Clinquart, Antoine ULg

in Viandes et Produits Carnés - Hors série "11èmes Journées des Sciences du Muscle et Technologies des Viandes" (2006, October)

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See detailNous ne pouvons ajourner la réforme des politiques d'aide au développement
Gemenne, François ULg; Niang, Abdoul Jelil; Ozer, Pierre ULg

Article for general public (2006)

Barça ou Barzakh, un autre monde ou l'autre monde, Barcelone ou l'au-delà. Voici le leitmotiv de tous ces candidats à l'exil qui s'entassent quotidiennement dans des cayucos, ces grandes pirogues colorées ... [more ▼]

Barça ou Barzakh, un autre monde ou l'autre monde, Barcelone ou l'au-delà. Voici le leitmotiv de tous ces candidats à l'exil qui s'entassent quotidiennement dans des cayucos, ces grandes pirogues colorées utilisées pour la pêche, en direction des îles Canaries. Après les départs massifs observés à partir de Nouadhibou, en Mauritanie septentrionale, les départs s'étalent vers le sud, du Sénégal, de Guinée-Bissau et même de Guinée-Conakry, soit des traversées de plus de 2000 kilomètres. Depuis le début de l'année, ils sont plus de 25 000 à avoir atteint les côtes espagnoles, largement plus que le « record » établi à 9929 pour toute l'année 2002. Mais combien y ont laissé la vie ? Il est malaisé de répondre à cette question. [...] [less ▲]

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See detailQuantifications naturelles projectivement équivariantes
Radoux, Fabian ULg

Scientific conference (2006, September 28)

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