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See detailEx-situ’ conservation of Antarctic cyanobacteria : a culture collection to explore diversity and bioactivity
Wilmotte, Annick ULg; Renard, Marine ULg; Kleinteich, J et al

Poster (2014, August)

Cyanobacteria appear as the dominant phototrophs in Antarctic terrestrial and freshwater ecosystems. Since 2011, the Belgian Science Policy Office has funded the BCCM/ULC public collection of (sub)polar ... [more ▼]

Cyanobacteria appear as the dominant phototrophs in Antarctic terrestrial and freshwater ecosystems. Since 2011, the Belgian Science Policy Office has funded the BCCM/ULC public collection of (sub)polar cyanobacteria. It is currently holding 102 Antarctic cyanobacterial strains and the catalogue is available on http://bccm.belspo.be/db/ulc_search_form.php. A Quality Management System was implemented and an ISO9001 certificate was obtained for the public deposition and distribution of strains. The strains are kept as living cultures, and their cryopreservation is in progress. The Antarctic cyanobacterial strains were isolated from samples of the three main biogeographic provinces. The purpose of this public collection is to gather a representative portion of the cyanobacterial diversity with different ecological origins (limnetic microbial mats, soil crusts, cryoconites, endoliths, etc.) and make it available for researchers to study the diversity, evolution, adaptations to the environmental conditions, and genomic make-up. Three cyanobacterial orders are represented: Chroococcales, Oscillatoriales and Nostocales. This is particularly important in view of the emerging use of metagenomic approaches on environmental samples, where the comparisons with the genome sequences from well-defined strains is very useful. They could also serve as references for compounds such as fatty acids and pigments. In addition, cyanobacteria produce a range of secondary metabolites (e.g. alkaloides, cyclic and linear peptides, polyketides) with different bioactive potential (e.g. antibiotic, antiviral, anticancer, cytotoxic, genotoxic). Bioassays have shown antifungal activities of the cell extracts of strains Plectolyngbya hodgsonii ULC009 and Phormidium priestleyi ULC026. Due to the geographic isolation and the strong environmental stressors of the habitat, the exploration of these metabolites in Antarctic cyanobacterial strains seems especially promising for biotechnology or biomedical applications. In summary, the BCCM/ULC public collection could serve as a general reference for Antarctic cyanobacteria with multiple applications, as well as a resource for novel bioactive compounds. [less ▲]

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See detail‘Ex-situ’ preservation and characterization of Antarctic cyanobacteria in the BCCM/ULC collection
Kleinteich, Julia ULg; Renard, Marine ULg; Simons, Véronique et al

Poster (2015, June 09)

The BCCM/ULC public collection of (sub)polar cyanobacteria is funded since 2011 by the Belgian Science Policy Office. An ISO9001 certificate was obtained for the public deposition and distribution of ... [more ▼]

The BCCM/ULC public collection of (sub)polar cyanobacteria is funded since 2011 by the Belgian Science Policy Office. An ISO9001 certificate was obtained for the public deposition and distribution of strains, as part of the multi-site certification for the BCCM consortium. BCCM/ULC is currently holding 160 public cyanobacterial strains and the catalogue is available on http://bccm.belspo.be/catalogues/ulc-catalogue-search. Continuous maintenance of living cultures, some of which are also cryopreserved, ensure the preservation and the possibility to rapidly deliver strains to clients for fundamental and applied research. The main holding of the collection concerns (sub)polar strains isolated from different biotopes and representative of a large taxonomic diversity. The molecular characterization is underway, on the basis of 16S rRNA and ITS sequences, but also Multiple Locus Sequence Analysis and genome sequencing. In addition, cyanobacteria are known to produce a range of secondary metabolites (e.g. alkaloides, cyclic and linear peptides, polyketides) with various bioactive potential. The presence of genes involved in the production of microcystin is currently studied by PCR, and analytical methods are used to confirm the toxin production. Due to the geographic isolation and the strong environmental stressors of the habitat, the exploration of these metabolites in Antarctic cyanobacterial strains seems especially promising for biotechnology or biomedical applications. [less ▲]

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See detailEx-vivo cytokine production by whole blood cells from cancer patients
De Groote, Donat; Vrindts-Gevaert, Yvonne; Lopez Y Cadenas, Miguel ULg et al

in Cancer Detection & Prevention (1996), 20

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See detailLes exacerbations dans la BPCO: un fardeau a reduire
Corhay, Jean-Louis ULg; Nguyen Dang, Delphine ULg; Louis, Renaud ULg

in Revue Médicale de Liège (2006), 61(10), 691-6

Exacerbations of chronic obstructive pulmonary disease (COPD) play a very important role. Unfortunately they were neglected a long time in the therapeutic tests. However exacerbations influence the ... [more ▼]

Exacerbations of chronic obstructive pulmonary disease (COPD) play a very important role. Unfortunately they were neglected a long time in the therapeutic tests. However exacerbations influence the decline of the respiratory function over time, cause important deterioration of the quality of life of the patients, increase morbidity and mortality of COPD, and finally represent a burden for health care. Reducing the number of exacerbations could potentially slow down the progression of the disease. Thus the prevention of exacerbations should be the "corner stone" of the maintenance treatment of the COPD. In this review we propose to recall the importance of exacerbations in COPD and to present the treatment which have been shown to reduce exacerbation rate in COPD. [less ▲]

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See detailExact and Heuristic Solution Methods for a VRP with Time Windows and Variable Service Start Time
Michelini, Stefano ULg; Arda, Yasemin ULg; Crama, Yves ULg et al

Scientific conference (2015, February 05)

We consider a VRP with time windows in which the total cost of a solution depends on the duration of the vehicle routes, and the starting time for each vehicle is a decision variable. We first develop a ... [more ▼]

We consider a VRP with time windows in which the total cost of a solution depends on the duration of the vehicle routes, and the starting time for each vehicle is a decision variable. We first develop a Branch-and-Price algorithm considering the pricing subproblem, an elementary shortest path problem with resource constraints (ESPPRC). We discuss research on this exact solution methodology, based on a bidirectional dynamic programming approach for the ESPPRC, and on the design of a matheuristic. [less ▲]

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See detailAn exact bi-directional dynamic programming algorithm for an elementary shortest path problem with variable service start time
Arda, Yasemin ULg; Crama, Yves ULg; Kucukaydin, Hande ULg

Conference (2014, January 31)

We consider an elementary shortest path problem with resource constraints (ESPPRC), where a capacitated single vehicle serves customers by respecting their associated time windows. The vehicle can start ... [more ▼]

We consider an elementary shortest path problem with resource constraints (ESPPRC), where a capacitated single vehicle serves customers by respecting their associated time windows. The vehicle can start servicing the customers at any desired time, but it can be used for a fixed amount of time. The total transportation cost depends on the total distance traveled and the total amount of time that the vehicle spends by performing the assigned trip. On the other hand, each served customer yields a revenue. Thus, the aim is to identify the path to be followed and the start time of the vehicle from the depot that minimize the total transportation cost minus the gained revenues. This kind of a problem can be encountered as a pricing subproblem when a branch-and-price algorithm is applied to solve vehicle routing problems with additional constraints. In such a case, the revenues correspond to the dual prices of the visited vertices. It is known that the classical ESPPRC can be solved to optimality by implementing a dynamic programming (DP) algorithm. However, our problem has to take an infinite number of Pareto-optimal states into consideration, since the vehicle can leave the depot at any point in time and charges depending on the total traveling and waiting time. We propose an exact DP algorithm which can deal with an infinite number of Pareto-optimal states by representing total traveling and waiting time as a piecewise linear function of the service start time at the depot and develop suitable dominance rules. Furthermore, a column generation algorithm is devised for solving the relaxed set covering formulation of the related vehicle routing problem where new columns are determined by the proposed DP algorithm. Finally, computational results are presented. [less ▲]

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See detailAn Exact Method for Designing Shewhart X ̅ and S2 Control Charts to Guarantee the In-Control Performance
Faraz, Alireza ULg; Heuchenne, Cédric ULg

in Journal of Quality Technology (2016)

The in-control performance of the Shewhart X ̅ and S2 control charts with estimated in-control parameters has been evaluated by a number of authors. Results indicate an unrealistically large amount of ... [more ▼]

The in-control performance of the Shewhart X ̅ and S2 control charts with estimated in-control parameters has been evaluated by a number of authors. Results indicate an unrealistically large amount of Phase I data is needed to have the desired in-control average run length (ARL) value in Phase II. To overcome this problem, it has been recommended that the control limits be adjusted based on a bootstrap method to guarantee that the in-control ARL is at least a specified value with a certain specified probability. In our paper we present simple formulas for the required control limits so that practitioners do not have to use the bootstrap method. An assumption of normality is required. The advantage of our proposed method is in its simplicity; there is no bootstrapping and the control chart constants do not depend on the Phase I sample data. [less ▲]

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See detailExact Model Reduction of Combinatorial Reaction Networks
Conzelmann, Holger; Fey, Dirk ULg; Gilles, E. D.

in BMC Systems Biology (2008), 2

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See detailAn exact Riemann Solver and Godunov Scheme for Simulating Highly Transient Mixed Flows
Kerger, François ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Journal of Computational & Applied Mathematics (2011), 235

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See detailExact solution of the dynamic epidemic model on the Bethe lattice
Vandewalle, Nicolas ULg; Ausloos, Marcel ULg

in Physica A: Statistical Mechanics and its Applications (1996), 230(1-2), 1-10

The dynamic epidemic model considers the spreading of a cluster in a medium containing a fraction x of mobile particles which are pushed by the propagation front. This model is analytically studied on the ... [more ▼]

The dynamic epidemic model considers the spreading of a cluster in a medium containing a fraction x of mobile particles which are pushed by the propagation front. This model is analytically studied on the Bethe lattice for any branching rate z. We give the exact solution x(c)= (z(2) - 1)/z(2) for the percolation threshold. This is in contrast with the x(c) = (z - 1)/z result for static particles. Moreover, we calculate the critical exponents y = 1 and v = 1 characterizing respectively the divergence of the cluster mass and the correlation length at x(c). These exponents are found to be the same as for the case of static particles, i.e. for random percolation on the Bethe lattice. [less ▲]

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See detailExact solution to the relative orbital motion in a central force field
Condurache, D.; Martinusi, Vladimir ULg

in 2nd International Symposium on Systems and Control in Aerospace and Astronautics, 2008. ISSCAA 2008. (2008)

The paper presents the exact solution to the relative orbital motion that takes place in a central force field.This problem is a generalization of the problem of the Keplerian relative motion in a central ... [more ▼]

The paper presents the exact solution to the relative orbital motion that takes place in a central force field.This problem is a generalization of the problem of the Keplerian relative motion in a central force field. The solution is presented in a coordinate free vectorial form, offering closed form expressions for the law of motion and the velocity. The solution is offered to the non-linear model of the relative motion problem, and itgeneralizes the solutions found by Clohessy-Wiltshire, Lawden and Tschauner-Hempel for the case of the Keplerian relative motion. The applications of this problem are in satellite formation flying, satellite constellations and orbital rendezvous. [less ▲]

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See detailExact solution to the relative orbital motion in eccentric orbits
Condurache, Daniel; Martinusi, Vladimir ULg

in Solar System Research (2009), 43

This paper studies the relative orbital motion between arbitrary Keplerian trajectories. A closed-form vectorial solution to the nonlinear initial value problem that models this type of motion with ... [more ▼]

This paper studies the relative orbital motion between arbitrary Keplerian trajectories. A closed-form vectorial solution to the nonlinear initial value problem that models this type of motion with respect to a noninertial reference frame is offered. Without imposing any particular conditions on the leader or the deputy satellites trajectories, exact expressions for the relative law of motion and relative velocity are obtained in a closed form. This solution allows the parameterization of the relative motion manifold and offers new methods to study its geometrical and topological properties. The result presented in this paper opens the way to obtain new classes of approximate solutions to the equations of relative motion with time, an eccentric or true anomaly as independent variables. [less ▲]

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See detailExact validation of breeding value prediction software
Leclerc, H.; Druet, Tom ULg; Ducrocq, V.

in Proceedings of the 8th World Congress on Genetics Applied to Livestock Production (2006)

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See detailExactitude du positionnement numérique des axes de ruissellement dans les bassins versants agricoles
Ouedraogo, Mohamar ULg

Doctoral thesis (2014)

Des études récentes menées en Belgique estiment les dommages causés par les inondations et les coulées boueuses entre 12,5 et 122 millions d’euros par an pour les infrastructures publiques, et entre 1,6 ... [more ▼]

Des études récentes menées en Belgique estiment les dommages causés par les inondations et les coulées boueuses entre 12,5 et 122 millions d’euros par an pour les infrastructures publiques, et entre 1,6 et 16,5 millions d’euros par an pour les habitations. La carte des zones à risque potentiel de ruissellement concentré est l’un des outils mis en place par la Wallonie pour lutter contre ces phénomènes de plus en plus fréquents. Cependant, la résolution (10 × 10 m) du MNT utilisé pour extraire les axes de ruissellement est trop faible pour prendre en compte les détails de la microtopographie (travail du sol, résidus de cultures, cultures…) des parcelles agricoles. De plus, elle ne tient pas compte des incertitudes inévitables, présentes dans les données altimétriques utilisées. L’objectif de cette thèse est d’envisager l’utilisation des nouvelles technologies d’acquisition des données altimétriques de haute densité (plusieurs points/m²), i.e., le scanner laser terrestre (TLS) et la photogrammétrie à partir d’un véhicule non piloté (VNP) pour créer un modèle numérique de terrain (MNT) de meilleure exactitude et de haute résolution spatiale (maille de dimensions ± 1 x 1 m). Cela permet de tenir compte de la variabilité altimétrique des parcelles agricoles, et d’analyser son impact sur le positionnement numérique des axes de ruissellement. Dans un premier temps, un TLS et un VNP à voilure fixe ont été utilisés pour acquérir des données altimétriques sur un bassin versant agricole de 12 ha. Deux logiciels photogrammétriques ont permis de générer le MNTPSC (Agisoft PhotoScan) et le MNTMCM (MicMac) ; tandis que des traitements statistiques ont été nécessaires pour supprimer les erreurs systématiques présentes dans les nuages de points obtenus au TLS avant de les fusionner pour générer le MNTTLS. La comparaison des MNT avec des points de contrôle (GCP) positionnés au récepteur GNSS (Global Navigation Satellite System) en mode RTK (Real Time Kinematic) a montré que le MNTTLS est le plus exact avec un RMSE (Root Mean Square Error) de 4,5 cm, suivi par le MNTMCM et le MNTPSC avec des RMSE valant respectivement 9,0 et 13,9 cm. Dans un second temps, la méthode de Monte Carlo a été utilisée pour générer à partir du MNTTLS, des MNT équiprobables. L’extraction des axes de ruissellement à partir des MNT équiprobables a permis de définir pour chaque maille du MNT, la probabilité d’appartenir à l’axe de ruissellement, et de définir une zone contenant l’axe de ruissellement extrait du MNTTLS avec une probabilité définie. Une telle zone peut être utilisée pour la mise en place de solutions telles que les bandes et les chenaux enherbés. La comparaison des algorithmes de suppressions des dépressions fermées d’une part, et des algorithmes d’extraction de la direction de l’eau d’autre part, a montré peu de différence au niveau de la probabilité d’appartenance des mailles à l’axe de ruissellement lorsque le MNT est de haute résolution spatiale (± 1 m). Enfin, les analyses statistiques ont montré que les altitudes des GCP utilisés dans la méthode de Monte Carlo sont influencées par l’état d’ameublissement et par la rugosité des sols des parcelles agricoles. Les études futures, e.g., à l’échelle de la Wallonie, devront prendre en compte l’impact de ces erreurs. [less ▲]

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See detailExactitude et précision de la mesure de superficie de parcelle de culture
Ly, Sarann ULg

Master of advanced studies dissertation (2005)

There are a number of important reasons for determining areas: natural resource valorisation and protection, environmental management or others works. But what is a data quality? Accuracy is characterised ... [more ▼]

There are a number of important reasons for determining areas: natural resource valorisation and protection, environmental management or others works. But what is a data quality? Accuracy is characterised by systematic errors and mistakes. When these errors are eliminated, the standard deviation qualifies the precision. It is characterized by the random errors that there is no absolute way to eliminate them and which obey the general law of normal distribution. Three formulas are selected according to instruments available to compute the culture parcel area: (1) Area by polar coordinates, (2) Area by rectangular coordinates and (2) formula of Sarron. When parameter measurements are subject to error, areas calculated from the parameters will also be in error. The statistical models associated to each formula are developed to evaluate the precision of area measurement and are checked by simulations. Three types of available instrument according to suitable methods: (1) Total Station, (2) GPS (RTK GPS and DGPS) and (3) Topofil and Compass (forest instruments). These instruments are used in the field to confirm the three variance computation formulas. For all instruments used, approximate and observed variances are equivalent. Two exceptions to this confirmation: the total station and DGPS in case of area determined by a small number of points. [less ▲]

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See detailEXAFS study of halato-telechelic polymers and-capped with group IVb metal carboxylates at room and low temperature
Vlaic, G.; Navarra, G.; Regnard, J. R. et al

in Journal of Physics II France (1995), 5(5), 665-675

The EXAFS analysis at 300, 70 and 5 K has shown that the thermal disorder is very low in a carboxylato telechelic polybutadiene neutralized with an increasing excess of Zr isopropoxide. Two types of Zr-O ... [more ▼]

The EXAFS analysis at 300, 70 and 5 K has shown that the thermal disorder is very low in a carboxylato telechelic polybutadiene neutralized with an increasing excess of Zr isopropoxide. Two types of Zr-O bonds in the first shell account for the experimental data. The Zr-O distances and number of oxygen neighbours in the two subshells are found to be independent of temperature in the investigated range. The proportion of Zr in the samples has no effect on the total number of oxygen atoms around Zr, in contrast to their relative distribution in the two subshells. The number of Zr atoms increases in the second shell with the total amount of this metal. Upon increasing degree of neutralization from 200 to 600%, the static disorder increases together with a strong reduction of the dynamic part of the Debye-Waller (DW) factor. At a high degree of neutralization (> 400%), the DW factor for the Zr-Zr bond is largely independent of temperature. These observations agree with formation of Zr polynuclear microdomains, the size and rigidity of which increase with the Zr content, in good agreement with the profound changes previously reported in the viscoelastic properties of these materials. [less ▲]

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See detailExamen à grande dispersion d'un cas typique de multiplet de résonance de la vapeur diatomique de soufre
Swings, Polydore ULg; Legros, A.

in Bulletin de la Classe des Sciences. Académie Royale de Belgique (1931), XVII(6), 808-811

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