Brussels, Belgium
Brussels, Belgium
Time filter
Source Type

Delvigne F.,University of Liège | brognaux A.,University of Liège | Gorret N.,French National Institute for Agricultural Research | Neubauer P.,TU Berlin | And 7 more authors.
Biochemical Engineering Journal | Year: 2011

The dynamics of microbial stress response in intensive cultivation conditions remains not completely understood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as biosensors of the heterogeneities generated in a two-compartment scale-down reactor. The stress promoters have been chosen for their responsiveness to carbon limitation corresponding to the global substrate profiles encountered in intensive fed-batch cultures. From our results, it can be concluded that the exposure of microbial cells to substrates heterogeneities tends to decrease the GFP expression level in fed-batch mode. Fluorescence intensities have been monitored at the single cell level by using flow cytometry. During the course of the fed-batch culture, a drop at the level of the intracellular GFP content has been observed for the two scale-down operating conditions and for the two promoters sensitive to substrate limitation (rpoS and csiE). The fluorescence drop can be attributed to the repression of these promoters but also to the release of GFP to the extracellular medium according to the increase of the fluorescence level of the supernatant. This leakage has been observed for all the operating conditions, i.e. the scale-down reactors and the culture operating in the normal mode, i.e. in a well-mixed bioreactor. Interestingly, GFP leakage is more pronounced in the case of the cultures operated in the normal mode. Indeed, staining by propidium iodide tends to be more elevated for the microbial cells cultured under the normal mode by comparison with those cultured in scale-down conditions, indicating a higher permeability of the membrane. These results suggest that GFP microbial biosensors could be used to detect simultaneously mixing imperfections and their impact on the viability of microorganisms. © 2011 Elsevier B.V.

Halbwachs J.-L.,University of Strasbourg | Boffin H.M.J.,ESO | Le Bouquin J.-B.,CNRS Grenoble Institute for Particle Astrophysics and Cosmology Laboratory | Kiefer F.,Tel Aviv University | And 17 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

In anticipation of the Gaia astrometric mission, a sample of spectroscopic binaries is being observed since 2010 with the Spectrograph pour l'Observation des PHénomènes des Intérieurs stellaires et des Exoplanètes (SOPHIE) spectrograph at the Haute-Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 per cent when combined with Gaia astrometric measurements. In order to validate the masses derived from Gaia, interferometric observations are obtained for three SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186. The masses of the six stellar components are derived. Due to its edge-on orientation, HIP 14157 is probably an eclipsing binary. We note that almost all the derived masses are a few per cent larger than the expectations from the standard spectral type-mass calibration and mass-luminosity relation. Our calculation also leads to accurate parallaxes for the three binaries, and the Hipparcos parallaxes are confirmed. © 2015 The Authors.

Rixhon G.,University of Liège | Juvigne E.,FRS FNRS
Geologica Belgica | Year: 2010

Located in the northern part of the Ardenne massif, the Ninglinspo catchment shows morphologic features (valley floor benches, slope dissymmetry, river superimposition, etc) which constitute the likely heritage of periglacial processes. Here, we consider chiefly the geomorphic meaning of the valley floor benches. Assuming that bench deposits resulted at least partially from periglacial processes during the last glacial means that, during the Holocene warming, the river was unable to evacuate them totally. Reasoning in the same way for previous glacial and interglacial episodes (e.g. with a river unable to transport during warm periods the entirety of the materials provided by periglacial slope processes), implies that a polygenic genesis of these benches should be considered. In this study, we try to bring to the fore this polygenic origin using different various techniques, including geophysical surveying and tephrochronology. Finally, catchment denudation rates by periglacial slope processes ranging from 0.45 to 2 mm/ka have been inferred since the last glacial.

In this article, we report the 2011 European guidelines on the management of cardiovascular diseases during pregnancy, with particular attention to the management of hypertension as hypertensive disorders are the most frequent cardiovascular complications in pregnancy.

Luciani M.,F.R.S. FNRS | Luciani M.,Solvay Group | Veredas D.,Solvay Group
Journal of Forecasting | Year: 2015

We introduce an approximate dynamic factor model for modeling and forecasting large panels of realized volatilities. Since the model is estimated by means of principal components and low-dimensional maximum likelihood, it does not suffer from the curse of dimensionality. We apply the model to a panel of 90 daily realized volatilities pertaining to SandP 100 from January 2001 to December 2008. Results show that our model is able to capture the stylized facts of panels of volatilities (comovements, clustering, long memory, dynamic volatility, skewness and heavy tails), and that it performs fairly well in forecasting, in particular in periods of turmoil, in which it outperforms standard univariate benchmarks. © 2015 John Wiley and Sons, Ltd.

Meyfroidt P.,F.R.S. FNRS | Meyfroidt P.,Catholic University of Louvain
Human Ecology | Year: 2013

Forest transition - i.e., the shift from decreasing to expanding forest cover - in the northern mountains of Vietnam was analyzed at the local scale in four villages from the 1970s to 2007-2008 to understand feedbacks from local environmental degradation on land uses, the conditions under which such feedbacks occur, and their possible roles in the transition. Remote sensing data were combined with field surveys including interviews, group discussions, mental and participatory mapping, observations and secondary sources. The feedbacks from environmental degradation and changes in the provision of ecosystem services to land practices via environmental cognitions were analyzed. The case studies showed that forest scarcity was perceived, interpreted and evaluated before possibly affecting land use practices. © 2013 Springer Science+Business Media New York.

Hasan M.R.,Catholic University of Leuven | Sabariego R.V.,Catholic University of Leuven | Geuzaine C.,University of Liège | Paquay Y.,F.R.S. FNRS
2016 IEEE International Energy Conference, ENERGYCON 2016 | Year: 2016

In this paper, the proper orthogonal decomposition and the Arnoldi-based Krylov subspace methods are applied to the magnetodynamic finite element analysis of power electronic converters. The performance of these two model order reduction techniques is compared both in frequency and time domain. Moreover, two original, adaptive and automated greedy snapshots selection methods are investigated using either local or global quantities for selecting the snapshots (frequencies or time steps). © 2016 IEEE.

Docquier N.,F.R.S. FNRS | Poncelet A.,Catholic University of Louvain | Delannoy M.,Catholic University of Louvain | Fisette P.,Catholic University of Louvain
Vehicle System Dynamics | Year: 2010

The goal of the present article is to analyse the performances of a modern vehicle equipped with a novel suspension system linking front, rear, right and left cylinders via a semi-active hydraulic circuit, developed by the Tenneco Automotive company. In addition to improving the vehicle's vertical performances (in terms of comfort), both the stiff roll motion of the carbody and the soft wrap motion of the rear/front wheel-axle units can be obtained and tuned via eight electrovalves. The proposed system avoids the use of classical anti-roll bars, which would be incompatible with the wrap performance. A major problem of the project is to produce a realistic and efficient 3D multibody dynamic model of an Audi A6 coupled, at the equational level, with an hydraulic model of the suspension including cylinders, accumulators, valve characteristics, oil compressibility and pipe dynamics. As regards the hydraulic submodel, a particular attention is paid to assemble resistive components properly without resorting to the use of artificial volumes, as proposed by some software dealing with the dynamics of hydraulic systems. According to Tenneco Automotive requirements, this model must be produced in a Matlab/Simulink form, in particular for control purposes. Thanks to the symbolic approach underlying our multibody program; a unified hybrid model can be obtained as a unique plant dynamic block to be real-time integrated in the Simulink environment on a standard computer. Simulation results highlight the advantages of this new suspension system, in particular regarding the behaviour of the car which can remain stiff in roll for curve negotiation, while maintaining a soft wrap behaviour on uneven surfaces. © 2010 Taylor & Francis.

Joshi N.,Copenhagen University | Baumann M.,Humboldt University of Berlin | Ehammer A.,Copenhagen University | Fensholt R.,Copenhagen University | And 10 more authors.
Remote Sensing | Year: 2016

The wealth of complementary data available from remote sensing missions can hugely aid efforts towards accurately determining land use and quantifying subtle changes in land use management or intensity. This study reviewed 112 studies on fusing optical and radar data, which offer unique spectral and structural information, for land cover and use assessments. Contrary to our expectations, only 50 studies specifically addressed land use, and five assessed land use changes, while the majority addressed land cover. The advantages of fusion for land use analysis were assessed in 32 studies, and a large majority (28 studies) concluded that fusion improved results compared to using single data sources. Study sites were small, frequently 300-3000 km2 or individual plots, with a lack of comparison of results and accuracies across sites. Although a variety of fusion techniques were used, pre-classification fusion followed by pixel-level inputs in traditional classification algorithms (e.g., Gaussian maximum likelihood classification) was common, but often without a concrete rationale on the applicability of the method to the land use theme being studied. Progress in this field of research requires the development of robust techniques of fusion to map the intricacies of land uses and changes therein and systematic procedures to assess the benefits of fusion over larger spatial scales. © 2016 by the authors; licensee MDPI, Basel, Switzerland.

Meyfroidt P.,F.R.S. FNRS | Meyfroidt P.,Catholic University of Louvain
Journal of Land Use Science | Year: 2015

Research into land and social-ecological systems science could benefit from improved clarity in the terminology used for causal analysis and a structured way to make causal inferences. Here I identify two aspects of causality, i.e. causal effects and causal mechanisms, and discuss explanation in historical sciences. I then propose definitions for the major terms used for causal relations, including driver, (spatial) determinant, location and contextual factor, proximate and underlying factors. Finally, I discuss the contribution of various operational approaches, including time series and counterfactual approaches for assessing causal effects and process-tracing approaches for establishing causal mechanisms. Having a coherent concept of causality, agreeing on a precise vocabulary and harnessing our tools with the clear purpose of establishing both causal effects and causal mechanisms should strengthen causal explanations for single cases, for drawing policy-relevant lessons and for theoretical development in relation to land and, more broadly, social-ecological systems processes. © 2015 Taylor & Francis

Loading FRS FNRS collaborators
Loading FRS FNRS collaborators