http://hdl.handle.net/2268/156 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/150324 Title: Simulations numériques de figures de diffractions à l'usage de la sixième secondaire et du premier baccalauréat <br/> <br/>Author, co-author: Leblanc, Christophe <br/> <br/>Abstract: La diffraction constitue de nos jours un phénomène physique incontournable pour la recherche (diffraction par rayons X, diffraction de neutrons, cristallographie, ...) et est, à juste titre, enseignée aussi bien en dernière année de secondaire qu'à l'université. Le logiciel présenté ci-dessous est un programme permettant de réaliser des figures de diffractions de manière simple et intuitive. Il existe naturellement déjà de nombreux programmes de simulations de figures de diffractions que l'on peut facilement trouver sur internet. Cependant ceux-ci sont, pour la plupart, ou bien limités (à la connaissance de l'auteur) à quelques cas particuliers - diffractions sur une ou plusieurs fentes, un rond, plus rarement un carré - ou bien complexes à l'utilisation. Bien que ces programmes soient dignes d'intérêts et peuvent se montrer utiles dans le cadre d'un enseignement, leurs limitations empêchent d'acquérir une intuition réelle de ce qu'est la diffraction. Par exemple, quelle est la figure de diffraction obtenue par un réseau cristallin cubique, un réseau hexagonal, ou encore une hélice ? C'est précisément cette faille pédagogique que vient combler le logiciel présenté ci-dessous. En effet, celui-ci permet d'obtenir la figure de diffraction de « n'importe quelle forme » (en deux dimensions), « forme » entièrement paramétrable par l'utilisateur au moyen d'un simple fichier bitmap ; format de fichier graphique le plus répandu et le plus simple à employer. Il est naturellement également possible d'effectuer de la diffraction de manière expérimentale au moyen d'un simple laser hélium-néon (facilement accessible dans le commerce et d'un prix modéré) et de diapositives. Cependant, outre que le logiciel présenté ci-dessous peut-être obtenu gratuitement par simple demande à l'auteur, celui-ci se montre beaucoup plus souple d'utilisation que de simples diapositives car entièrement paramétrable, et, comme tout logiciel, échappe aux aléas expérimentaux (poussières sur les diapositives, problèmes d'alignements diapositives-laser, nécessité d'un local sombre, ...) Thu, 13 Jun 2013 08:15:45 GMT http://hdl.handle.net/2268/149801 Title: Bayesian ODE-penalized B-spline model with Gaussian mixture as error distribution <br/> <br/>Author, co-author: Jaeger, Jonathan; Lambert, Philippe <br/> <br/>Abstract: In the standard Bayesian ODE-penalized B-spline approach, it is assumed that the error distribution is homogeneous Gaussian. But, in many applications, the normal assumption for the error distribution is not a realistic choice. The goal of this paper is to extend the standard Bayesian ODE-penalized B-spline approach to settings where the error term distribution can be described using a mixture of normals. Tue, 04 Jun 2013 16:32:31 GMT http://hdl.handle.net/2268/149800 Title: On the use of adhesion parameters to validate models specified using systems of affine differential equations <br/> <br/>Author, co-author: Jaeger, Jonathan; Lambert, Philippe <br/> <br/>Abstract: A strategy for the selection of system of differential equations is proposed based on Bayesian ODE-penalized B-spline approach. It estimates the ODE parameters, approximates the solution of the ODE model and quantifies the suitability of the proposed differential equations to model the dynamics of the observed state functions. Simulation study confirms that these ODE-adhesion parameters are able to question a system of differential equations as a descriptor of the dynamics in the state functions. This methodology is illustrated on a pharmacokinetic study. Tue, 04 Jun 2013 16:21:01 GMT http://hdl.handle.net/2268/149799 Title: Bayesian penalized smoothing approaches in models specified using affine differential equations with unknown error distributions <br/> <br/>Author, co-author: Jaeger, Jonathan; Lambert, Philippe <br/> <br/>Abstract: A full Bayesian approach based on ODE-penalized B-splines and penalized Gaussian mixture is proposed to jointly estimate ODE-parameters, state function and error distribution from the observation of some state functions involved in systems of affine differential equations. Simulations inspired by pharmacokinetic studies show that the proposed method provides comparable results to the method based on the standard ODE-penalized B-spline approach (i.e. with the Gaussian error distribution assumption) and outperforms the standard ODE-penalized B-splines when the distribution is not Gaussian. This methodology is illustrated on the Theophylline dataset. Tue, 04 Jun 2013 16:16:17 GMT http://hdl.handle.net/2268/149736 Title: A PML for convex truncated domains in time-dependent acoustics with a DG-FE discretization <br/> <br/>Author, co-author: Modave, Axel; Lambrechts, Jonathan; Delhez, Eric; Geuzaine, Christophe <br/> <br/>Abstract: A new perfectly matched layer (PML) is proposed for convex truncated domains in the context of time-dependent acoustics. With this formulation, the size of the computational domain can be reduced when classical shapes of truncated domains are less appropriate. A numerical discretization based on the discontinuous Galerkin method is then described and validated. An example of realistic three-dimensional application is finally proposed. Mon, 03 Jun 2013 21:57:03 GMT http://hdl.handle.net/2268/149049 Title: Minéralogie et propriétés physico-chimiques des smectites de Bana et Sabga (Cameroun). Utilisation dans la décoloration d'une huile végétale alimentaire <br/> <br/>Author, co-author: Mache, Jacques Richard <br/> <br/>Abstract: In this study, clay samples were collected in the localities of Bana and Sabga, in the regions of the west and north-west Cameroon, respectively. The purpose of this study was to determine their mineralogical composition, their physico-chemical properties and to assess their potential use in the bleaching process of palm oil, which is the main edible vegetable oil produced and refined in Cameroon. <br /> The results obtained from the analyses (XRD, FTIR, DTA / TGA and SEM) revealed that montmorillonite is the main clay mineral in these materials. It is associated with kaolinite and mica. Non-clay minerals such as quartz, anatase, cristobalite, K-feldspar and heulandite are also identified in variable quantities. Chemical analyses of the major elements show that the clays from Bana and Sabga consist mainly of the follow oxides such as SiO2, Al2O3 and Fe2O3. Bana clays have a cation exchange capacity (CEC) between 50 and 60 meq/100 g and a specific surface area between 50 and 60 m2/ g. Sabga clays have a lower capacity cation exchange (38- 46 meq/100 g) and a wider range of specific surface area (33-90 m2 / g). The characterization of the natural clays allowed to select of one sample by locality for sulfuric acid treatment. <br />The acid treatment of these materials led to structural, morphological and textural changes. Analysis by X-ray diffraction showed a progressive decrease in the intensity of the (001) reflection of montmorillonite and a shift of its basal d001-value. Treatment with more acid concentration causes an increase in the surface area of the obtained products and a decrease in cation exchange capacity. <br />The assessment of the bleaching power of natural and acid-activated Bana clay in palm oil decolorization shows that the activated clay has a high bleaching capacity (~ 87%) compared to the natural clay (~ 55%). palm oil Bleaching by these clay materials does not deteriorate the bleached oil. These materials can thus be used as bleaching earths in the refining oil process. Thu, 23 May 2013 11:15:33 GMT http://hdl.handle.net/2268/148958 Title: Prévision des rendements agricoles. Guide d'utilisation. <br/> <br/>Author, co-author: Bronne, Charles-Emmanuel; Wellens, Joost; Midekor, Akoly Agblévi; Diakité, Mamadou; Denis, Antoine; Tychon, Bernard <br/> <br/>Abstract: Manuel présentant une méthode, développée par l'Université de Liège, de prévision de la production agricole. Cette méthode se base sur l'utilisation de différents programmes informatiques, et a pour but de prévoir le rendement agricole à partir de données météorologiques, agrométéorologiques, et NDVI (télédétecté). Elle est appliquée dans ce manuel sur les cultures du coton et du maïs au Burki Faso. Thu, 23 May 2013 06:47:25 GMT http://hdl.handle.net/2268/148891 Title: Compost Pile Monitoring Using Different Approaches:GC-MS, E-nose and dynamic olfactometry <br/> <br/>Author, co-author: Gutierrez, M. C.; Chica, A. F.; Martin, M. A.; Romain, Anne-Claude <br/> <br/>Abstract: The evaluation of odour emissions associated to the composting process is complex because these emissions depend on several factors such as the raw material to be composted, the different stages of the composting process, meteorological conditions, and others. For this reason, the aim of this paper is to compare complementary approaches to monitor odours. The odour source selected for this study is green waste compost at different maturity stages. The study site is a composting facility located in the south of Belgium. The compared approaches were: a portable e-nose developed by the Environmental Monitoring Research team (Arlon, Belgium) to monitor odorous emissions from the composting piles; chemical analyses performed in the laboratory using a GC–MS (manufactured by Thermo) to analyse volatile organic compounds which were collected by active sampling on Tenax TA sorbent simultaneously to the in situ e-nose measurements and olfactometric measurements to determine the odour concentration (ouE/m3) using the Odile olfactometer (Odotech). The portable e-nose was also used in the laboratory with compost odour samples collected in bags. The large numbers of data sets obtained were explored by statistical methods such as principal components analysis. The results obtained highlight the advantages of monitoring the composting process with these three approaches. Each approach gives different information about the composting process and the emissions generated. While the e-nose is capable of identifying some chemical family emissions and some activities such as turning steps, the GC–MS identifies each chemical compound emitted and dynamic olfactometry quantifies the odour concentration (ouE/m3) in relationship with these emissions. Wed, 22 May 2013 13:18:53 GMT http://hdl.handle.net/2268/148536 Title: Influence of swimming strategy on microorganism separation by asymmetric obstacles <br/> <br/>Author, co-author: Berdakin, I; Jeyaram, Y.; Moshchalkov, V.V.; Venken, L.; Dierckx, S.; Vanderleyden, J.; Silhanek, Alejandro; Condat, C.A.; Marconi, V. <br/> <br/>Abstract: It has been shown that a nanoliter chamber separated by a wall of asymmetric obstacles can lead to an inhomogeneous distribution of self-propelled microorganisms. Although it is well established that this rectification effect arises from the interaction between the swimmers and the noncentrosymmetric pillars, here we demonstrate numerically that its efficiency is strongly dependent on the detailed dynamics of the individual microorganism. In particular, for the case of run-and-tumble dynamics, the distribution of run lengths, the rotational diffusion, and the partial preservation of run orientation memory through a tumble are important factors when computing the rectification efficiency. In addition, we optimize the geometrical dimensions of the asymmetric pillars in order to maximize the swimmer concentration and we illustrate how it can be used for sorting by swimming strategy in a long array of parallel obstacles. Wed, 15 May 2013 16:45:42 GMT http://hdl.handle.net/2268/148438 Title: Luminescence dating of the Palaeolithic site of Kulbulak (Uzbekistan) using IR50 and pIRIR290 signals from K-feldspar <br/> <br/>Author, co-author: Vandenberghe, Dimitri; Van Nieuland, J.; De Dapper, Morgan; Flas, Damien; Debeer, A.-E.; De Pelsmaeker, E.; Kolobova, K.; Pavlenok, K.; Islamov, U. Tue, 14 May 2013 09:08:28 GMT http://hdl.handle.net/2268/148280 Title: Relationship between the Synthesis of Prussian Blue Pigments, Their Color, Physical Properties, and Their Behavior in Paint Layers <br/> <br/>Author, co-author: Samain, Louise; Grandjean, Fernande; Long, Gary J.; Martinetto, Pauline; Bordet, Pierre; Strivay, David <br/> <br/>Abstract: Prussian blue pigments, highly insoluble mixed-valence iron(III) hexacyanoferrate(II) complexes of typical stoichiometry Fe4III[FeII(CN)6]3·xH2O or KFeIII[FeII(CN)6]·xH2O, have been used as pigments in oil paintings and watercolors for 300 years. For poorly understood reasons, these pigments often fade with time. Although the preparation methods have been recognized since the mid-eighteenth century as a contributory factor in the fading of the pigment, the spectral and physical properties of Prussian blue that vary with the type of synthesis were not precisely identified. Several Prussian blue pigments have been prepared by different methods and characterized by thermogravimetric analyses, high-energy powder X-ray diffraction, atomic absorption and flame emission, UV–visible, iron-57 Mössbauer, iron K-edge X-ray absorption, and Raman spectroscopy. The type of synthesis influences the hue, tinting strength, and hiding power properties of the Prussian blue pigments. Two major features appear to be strongly dependent on the preparative methods, the particle size and the local disorder. Both a nitrogen atmosphere and an intermediate aging step of the Berlin white, Fe2II[FeII(CN)6], during the synthesis are required to obtain a highly colored pigment through the optimization of particle size, minimization in the perturbations to the FeII–CN–FeIII intervalence electron transfer pathway, and the minimization of disordered vacancies. The potassium containing Prussian blue structure has been revisited. It can be described with the Pm3m space group, where approximately one-quarter of the [FeII(CN)6]4– sites are vacant and where the potassium cation is located at a zeolitic-like position inside the lattice cavities. The degree of ordering of the [FeII(CN)6]4– vacancies in all Prussian blues was quantified using atomic pair distribution analysis, an ordering that is consistent with the iron K-edge X-ray absorption spectra. The presence of strain in the crystals is observed by both powder X-ray diffraction and Mössbauer spectroscopy. The structural similarity between the alkali-free, improperly referred to as “insoluble”, and the alkali containing, “soluble”, Prussian blues may explain why the two varieties are almost undistinguishable by spectroscopic techniques. Sun, 12 May 2013 19:36:35 GMT http://hdl.handle.net/2268/148083 Title: Replacing explicit water and lipids by implicit representation in molecular dynamics simulations <br/> <br/>Author, co-author: Steinhauer, Sven; Crowet, Jean-Marc; Lins, Laurence; Brasseur, Robert <br/> <br/>Abstract: Molecular dynamics (MD) is an appropriate method for investigation of biomolecular systems and helps in explaining results from wet lab experiments or in getting further insight into details, which are not accessible by experimental methods(Lindahl, 2008). By now, many biologically relevant processes for drug design, toxicological studies and other fields of application, can not be performed by atomistic MD simulations (Lindahl, 2008). <br />In MD, the necessary time effort for carrying out a simulation is considerable and depends mainly on (1) the complexity of the simulated system (2) the simulated time scale (3) the simulation method (4) the efficiency of used hardware and software algorithms. Carried out MD simulations nowadays may still take weeks of calculation on high end computers. <br /> <br />In practice, biologically relevant processes, as e.g. protein folding, take usually place above the time scale of milli seconds. They can take up to the order of some thousands of seconds (in case of the folding of membrane proteins). Molecular dynamics computer simulations have reached the scale of micro seconds for simulations of systems where each atom was described and simulated over time.(Lindahl, 2008) <br /> <br />Nevertheless, MD has risen to an important promoter methodology for many different fields of application. By replacing bunches of atoms by artificial particles, complexity of the systems can be reduced. This method is called the coarse grain method (CG). Biggin and Bond (2008) found an acceleration of their simulation processes for self assembling membrane / protein systems in water by factor 100. They estimated one to two days of calculation for a simulated time scale of 0.1 to 0.2 micro seconds for their systems. <br /> <br />Implicit force fields like "IMPALA", aim to describe water and/or membrane molecules in simulations by a couple of simple and partially precalculable equations. “IMPALA” is a force field initially developed by our laboratory. Using this method, thousands of water and lipid molecules can be replaced, leading to a reduced complexity of the system to be simulated. <br />"IMPALA"(Ducarme et al., 1998) based on the assumption of rigid peptides and aimed to find the insertion characteristics of such in membranes. Elimination of the necessity for simulating the aqueous and lipid phase atom by atom in the software package "Gromacs"(Berendsen et al., 1995) will permit both: a gain of speed, as it was already the case for the introduction of the coarse grain method, and a gain of precision by turning rigid molecules flexible through "Gromacs". Our current work is the integration of the "IMPALA" implicit force field into "Gromacs". <br /> <br />Biggin, P.C. & Bond, P.J. Molecular dynamics simulations of membrane proteins. Methods Mol. Biol. 443, 147-60(2008). <br />Berendsen, et al. (1995) Comp. Phys. Comm. 91: 43-56. <br />Ducarme, P., Rahman, M. & Brasseur, R. IMPALA: a simple restraint field to simulate the biological membrane in molecular structure studies. Proteins 30, 357-71(1998). <br />Lindahl, E.R. (2008). Molecular dynamics simulations. Methods Mol. Biol. 443, 3-23. Wed, 08 May 2013 12:29:25 GMT http://hdl.handle.net/2268/147911 Title: Synthesis and fading of eighteenth-century Prussian blue pigments: a combined study by spectroscopic and diffractive techniques using laboratory and synchrotron radiation sources <br/> <br/>Author, co-author: Samain, Louise; Grandjean, Fernande; Long, Gary J.; Martinetto, Pauline; Bordet, Pierre; Sanyova, Jana; Strivay, David Sun, 05 May 2013 10:10:15 GMT http://hdl.handle.net/2268/147627 Title: A Balance Equation Determines a Switch in Neuronal Excitability <br/> <br/>Author, co-author: Franci, Alessio; Drion, Guillaume; Seutin, Vincent; Sepulchre, Rodolphe <br/> <br/>Abstract: We use the qualitative insight of a planar neuronal phase portrait to detect an excitability switch in arbitrary conductance-based models from a simple mathematical condition. The condition expresses a balance between ion channels that provide a negative feedback at resting potential (restorative channels) and those that provide a positive feedback at resting potential (regenerative channels). Geometrically, the condition imposes a transcritical bifurcation that rules the switch of excitability through the variation of a single physiological parameter. Our analysis of six di erent published conductance based models always nds the transcritical bifurcation and the associated switch in excitability, which suggests that the mathematical predictions have a physiological rel- evance and that a same regulatory mechanism is potentially involved in the excitability and signaling of many neurons. Mon, 29 Apr 2013 13:16:34 GMT http://hdl.handle.net/2268/147626 Title: An Organizing Center in a Planar Model of Neuronal Excitability Read More: http://epubs.siam.org/doi/abs/10.1137/120875016?journalCode=sjaday <br/> <br/>Author, co-author: Franci, Alessio; Drion, Guillaume; Sepulchre, Rodolphe <br/> <br/>Abstract: The paper studies the excitability properties of a generalized FitzHugh-Nagumo model. The model differs from the purely competitive FitzHugh-Nagumo model in that it accounts for the effect of cooperative gating variables such as activation of calcium currents. Excitability is explored by unfolding a pitchfork bifurcation that is shown to organize five different types of excitability. In addition to the three classical types of neuronal excitability, two novel types are described and distinctly associated to the presence of cooperative variables. Mon, 29 Apr 2013 13:16:15 GMT http://hdl.handle.net/2268/147513 Title: Non-destructive characterization of the Nizet Manuscript (XVIIIth century) : first results <br/> <br/>Author, co-author: Machowski, Mélanie; Calvo Del Castillo, Helena; Hocquet, François-Philippe; Dister, Hervé; Oger, Cécile; Strivay, David Sun, 28 Apr 2013 20:39:51 GMT http://hdl.handle.net/2268/147428 Title: How did I become a scientist <br/> <br/>Author, co-author: Javaux, Emmanuelle Sat, 27 Apr 2013 11:42:53 GMT http://hdl.handle.net/2268/147427 Title: L’eau dans l’univers <br/> <br/>Author, co-author: Jehin, Emmanuel; Javaux, Emmanuelle; Magain, Pierre; Gillon, Michaël Sat, 27 Apr 2013 11:40:57 GMT http://hdl.handle.net/2268/147332 Title: CLUPI, a high-performance imaging system on the ESA-NASA rover of the 2018 ExoMars mission to discover biofabrics on Mars <br/> <br/>Author, co-author: Josset, J.-L.; Westall, F.; Hofmann, B. A.; Spray, J. G.; Cockell, C.; Kempe, S.; Griffiths, A. D.; De Sanctis, M. C.; Colangeli, L.; Koschny, D.; Pullan, D.; Föllmi, K.; Diamond, L.; Josset, M.; Javaux, Emmanuelle; Esposito, F.; Barnes, D.; Giesen, N. <br/> <br/>Abstract: The scientific objectives of the ESA-NASA rover of the 2018 mission of the ExoMars Programme are to search for traces of past or present life and to characterise the near-sub surface. Both objectives require study of the rock/regolith materials in terms of structure, textures, mineralogy, and elemental and organic composition. The 2018 rover ExoMars payload consists of a suite of complementary instruments designed to reach these objectives. CLUPI, the high-performance colour close up imager, on board the 2018 ESA-NASA Rover plays an important role in attaining the mission objectives: it is the equivalent of the hand lens that no geologist is without when undertaking field work. CLUPI is a powerful, highly integrated miniaturized (<700g) low-power robust imaging system, able to operate at very low temperatures (-120°C). CLUPI has a working distance from 10cm to infinite providing outstanding pictures with a color detector of 2652x1768. At 10cm, the resolution is 7 micrometer/pixel in color. The focus mechanism and the optical-mechanical interface are a smart assembly in titanium that can sustain a wide temperature range. The concept benefits from well-proven heritage: Proba, Rosetta, MarsExpress and Smart-1 missions… Because the main science objective of ExoMars concerns the search for life, whose traces on Mars are likely to be cryptic, close up observation of the rocks and granular regolith will be critical to the decision as whether to drill and sample the nearby underlying materials. Thus, CLUPI is the essential final step in the choice of drill site. But not only are CLUPI's observations of the rock outcrops important, but they also serve other purposes. CLUPI, could observe the placement of the drill head. It will also be able to observe the fines that come out of the drill hole, including any colour stratification linked to lithological changes with depth. Finally, CLUPI will provide detailed observation of the surface of the core drilled materials when they are in the sample drawer at a spatial resolution of 15 micrometer/pixel in color. The close-up imager CLUPI on the ESA-NASA rover of the 2018 mission will be described together with its capabilities to provide important information significantly contributing to the understanding of the geological environment and could identify outstanding potential biofabrics (stromatolites...) of past life on Mars. <br/> <br/>Commentary: 14 Thu, 25 Apr 2013 11:51:53 GMT http://hdl.handle.net/2268/147330 Title: Planet TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of Their Reservoirs <br/> <br/>Author, co-author: Dehant, V.; Van Hoolst, T.; Breuer, D.; Claeys, P.; Debaille, V.; De Keyser, J.; Javaux, Emmanuelle; Goderis, S.; Karatekin, O.; Mattielli, N.; Noack, L.; Spohn, T.; Vandaele, A. C.; Vanhaecke, F.; Wilquet, V. <br/> <br/>Abstract: An overview is given of the Planet TOPERS project addressing habitability in our solar system. Thu, 25 Apr 2013 11:48:54 GMT