Last 7 days
Bookmark and Share    
Full Text
See detailStructural and Magnetic Properties of Nanosized strontium Hexaferrite Powders: Experimental and theoretical investigation
Abraime, Brahim; Ait Tamerd, Mohamed; Mahmoud, Abdelfattah ULg et al

Poster (2017, May 18)

Strontium M-type hexagonal ferrites were synthesized at different calcination temperatures (800 °C, 1000°C and 1100 °C) using sol-gel autocombustion method. Thermogravimetric analysis (TGA), X-ray ... [more ▼]

Strontium M-type hexagonal ferrites were synthesized at different calcination temperatures (800 °C, 1000°C and 1100 °C) using sol-gel autocombustion method. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy (MS) and superconducting quantum interference device magnetometer (SQUID) techniques were used to characterize crystal structure, phase composition, morphology and magnetic properties. TGA gives T=800 °C as beginning of suitable calcination. Hexaferrite structure of single phase is obtained according to XRD results for all samples with crystallite size between 28 nm and 35 nm. SEM images show the growth of grain size with increasing of annealing temperature. (BH)max is calculated based on SQUID results and shows an enhancement between T=800°C and T= 1000°C of 25%. The magnetic properties observed at low temperature are explained and confirmed by ab-initio calculations. [less ▲]

Detailed reference viewed: 22 (2 ULg)
Full Text
See detailApplication of wavelet transforms to geosciences: Extraction of functional and frequential information
Deliège, Adrien ULg

Doctoral thesis (2017)

It is now well-known that there exist functions that are continuous but nowhere differentiable. Still, it appears that some of them are less “irregular” than others. The pointwise regularity of a function ... [more ▼]

It is now well-known that there exist functions that are continuous but nowhere differentiable. Still, it appears that some of them are less “irregular” than others. The pointwise regularity of a function can be characterized by its Hölder exponent at each point. For the sake of practicability, it is more appropriate to determine the “size” of the sets of points sharing a same exponent, through their Hausdorff measure. By doing so, one gets the multifractal spectrum of a function, which characterizes in particular its monofractal or multifractal nature. The first part of this work is based on the so-called “wavelet leaders method” (WLM), recently developed in the context of multifractal analysis, and aims at its application to concrete situations in geosciences. First, we present the WLM and we insist particularly on the major differences between theory and practice in its use and in the interpretation of the results. Then, we show that the WLM turns out to be an efficient tool for the analysis of Mars topography from a unidimensional and bidimensional point of view; the first approach allowing to recover information consistent with previous works, the second being new and highlighting some areas of interest on Mars. Then, we study the regularity of temperature signals related to various climate stations spread across Europe. In a first phase, we show that the WLM allows to detect a strong correlation with pressure anomalies. Then we show that the Hölder exponents obtained are directly linked to the underlying climate and we establish criteria that compare them with their climate characteristics as defined by the Köppen-Geiger classification. On the other hand, the continuous version of the wavelet transform (CWT), developed in the context of time-frequency analysis, is also studied in this work. The objective here is the determination of dominant periods and the extraction of the associated oscillating components that constitute a given signal. The CWT allows, unlike the Fourier transform, to obtain a representation in time and in frequency of the considered signal, which thus opens new research perspectives. Moreover, with a Morlet-like wavelet, a simple reconstruction formula can be used to extract components. Therefore, the second part of the manuscript presents the CWT and focuses mainly on the border effects inherent to this technique. We illustrate the advantages of the zero-padding and introduce an iterative method allowing to alleviate significantly reconstruction errors at the borders of the signals. Then, we study in detail the El Niño Southern Oscillation (ENSO) signal related to temperature anomalies in the Pacific Ocean and responsible for extreme climate events called El Niño (EN) and La Niña (LN). Through the CWT, we distinguish its main periods and we extract its dominant components, which reflect well-known geophysical mechanisms. A meticulous study of these components allows us to elaborate a forecasting algorithm for EN and LN events with lead times larger than one year, which is a much better performance than current models. After, we generalize the method used to extract components by developing a procedure that detects ridges in the CWT. The algorithm, called WIME (Wavelet-Induced Mode Extraction), is illustrated on several highly non-stationary examples. Its ability to recover target components from a given signal is tested and compared with the Empirical Mode Decomposition. It appears that WIME has a better adaptability in various situations. Finally, we show that WIME can be used in real-life cases such as an electrocardiogram and the ENSO signal. [less ▲]

Detailed reference viewed: 67 (33 ULg)
See detailThe epistemic politics of TA institutionalization and international TA collaboration – a cosmopolitan perspective
Rosskamp, Benedikt ULg

Conference (2017, May 18)

When addressing the issue of further institutionalization of TA, two assumptions need to be empirically confronted and conceptually revisited. A first one considers the evolution of TA as a linear ... [more ▼]

When addressing the issue of further institutionalization of TA, two assumptions need to be empirically confronted and conceptually revisited. A first one considers the evolution of TA as a linear progression leading to new institutional creations in an increasing number of countries. Despite a series of calls for distributed, networked, multi-level and multi-actor TA capacities, the idea of creating more single, national, specialized and dedicated TA organizations remains dominant in TA discourse. A second assumption concerns the rationale of Technology Assessment and its performance in terms of “opening up” and “broadening out” (Ely et al. 2014) or “the reflexivity pathway” (Delvenne 2011), notably by resorting to participatory Technology Assessment. Results from case studies in Wallonia, Portugal and the Czech Republic require reconsidering the above-mentioned evolutionary assumptions for a more complex and paradoxical understanding of the future of TA. While the TA achievements in each case study are still uncertain to a high degree, we can sum up these respective TA developments under the banner of “evidence-based governance”. This particular understanding of knowledge and decision-making is coherent with a simultaneous observed shift away from the institutional deficit of TA (creating new institutions in newcomer countries) to a renewed strategy of resorbing a knowledge deficit (making TA knowledge available to a wider number of countries). This renewed approach to TA collaboration and capacity building increasingly gains traction both from a bottom-up perspective where actors try to organize themselves into a critical mass and in a top-down perspective of neoliberal and austerity policies. In such a constellation, positivistic science provides an evidence-base, which supposedly supports multi-level, multi-actor governance as it allows knowledge produced in one place to travel and serve a wide spectrum of actors and decision-making arenas. The consequences of this shift are crucially important to explore the re-makings and futures of Technology Assessment, as they put to the fore the issue of subsidiarity of both the production and the use of TA knowledge. Finally, we identify a shift from coexistence to a cosmopolitan mode of epistemic subsidiarity (Jasanoff 2013, 2014). The latter raises a series of new theoretical, practical and normative questions for the TA community. [less ▲]

Detailed reference viewed: 15 (0 ULg)
Full Text
See detailElections présidentielles française de 2017: analyse des résultats.
Verjans, Pierre ULg

Conference given outside the academic context (2017)

A la suite d'une campagne électorale particulièrement agitée, les deux principaux partis du pays depuis des décennies ne sont pas parvenus à placer leur candidat au deuxième tour. Les résultats et leurs ... [more ▼]

A la suite d'une campagne électorale particulièrement agitée, les deux principaux partis du pays depuis des décennies ne sont pas parvenus à placer leur candidat au deuxième tour. Les résultats et leurs conséquences méritent une analyse et une réflexion collective. [less ▲]

Detailed reference viewed: 57 (1 ULg)
Peer Reviewed
See detailAn exceptional Proterozoic assemblage of organic-walled microfossils and its implications for the early evolution of Eukaryotes
Loron, Corentin ULg; Rainbird, Rob; Greenman, Wilder et al

Conference (2017, May 18)

Detailed reference viewed: 13 (3 ULg)
See detailL’influence normative de la Chine en Amérique centrale: quels enjeux stratégiques ?
Wintgens, Sophie ULg

Conference (2017, May 18)

La République populaire de Chine (Chine) est aujourd’hui devenue un partenaire commercial incontournable, un important pourvoyeur d’investissements directs étrangers et un grand fournisseur de prêts ... [more ▼]

La République populaire de Chine (Chine) est aujourd’hui devenue un partenaire commercial incontournable, un important pourvoyeur d’investissements directs étrangers et un grand fournisseur de prêts financiers pour un nombre croissant de pays d’Amérique du Sud. Cette tendance s’observe également de plus en plus en Amérique centrale. L’accroissement de ses échanges économiques et commerciaux avec le Costa Rica, membre du Système d’intégration centraméricain (SICA) et premier pays centraméricain à avoir signé un accord de libre-échange avec Pékin, va de pair avec l’imposition des normes économiques et politiques dont sa politique commerciale internationale est porteuse. Ce constat pose dès lors la question du défi stratégique que représente cette influence normative chinoise pour les normes exportées par l’UE en Amérique centrale. Afin de répondre à cette question, cette communication se propose d’analyser la portée normative de la politique commerciale de la Chine envers l’Amérique centrale, afin de voir si elle est porteuse d’un projet politico-économique régional comparable au modèle d’intégration et de gouvernance régionale déployé par l’Europe communautaire dans le sous-continent. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
See detailThe earliest eukaryotes
Javaux, Emmanuelle ULg

Conference (2017, May 18)

Detailed reference viewed: 10 (0 ULg)
See detailQualité en chirurgie orthopédique
KURTH, William ULg

Scientific conference (2017, May 18)

Detailed reference viewed: 27 (0 ULg)
See detailDesign of reprocessable poly(ɛ-caprolactone)-based shape-memory materials
Defize, Thomas ULg

Doctoral thesis (2017)

Shape-memory polymers (SMPs) are remarkable materials able to switch from a temporary shape to their initial permanent shape by crossing a thermal transition, e.g. glass or melting transition. Efficient ... [more ▼]

Shape-memory polymers (SMPs) are remarkable materials able to switch from a temporary shape to their initial permanent shape by crossing a thermal transition, e.g. glass or melting transition. Efficient shape-memory effect is notably observed for chemically cross- linked semi-crystalline polymers. Chemical networks of semi-crystalline poly(ε-caprolactone) (PCL) are widely studied for the development of SMPs especially when biomedical applications are foreseen. As these SMPs are irreversibly cross-linked material, their (re)processing is quite limited since they cannot be molten or solubilized after cross-linking. This prevents any recycling. Thereby, using reversible cross-linking reactions allowing the formation or cleavage of the network upon a selected stimulus raise tremendous interest for the development of smart SMPs. Chemically cross-linked but remarkably (re)processable shape-memory polymers (SMP) were designed by crosslinking poly(ε-caprolactone) (PCL) stars via reversible cycloaddition reactions. The thermo-reversible Diels-Alder (DA) reaction between furan and maleimide was investigated to crosslink the PCL matrix. However, the relatively low retro DA temperature of the furan-maleimide adducts led to some inelastic deformation during shape memory tensile cycles. In order to get rid of this drawback, two alternative approaches were investigated, i.e. the substitution of the DA reaction firstly by the efficient triazolinedione click chemistry, especially the very fast and reversible Alder-ene reaction of 1,2,4-triazoline-3,5- dione (TAD) with indole compounds and secondly by a photo-reversible reaction, typically the photo-induced (2+2) cycloaddition of coumarins. With these networks, the typical shape memory properties of PCL networks (high fixity and recovery ratios) were preserved while upon an external (light or stress) stimulus, the PCL network can be (re)processed efficiently. [less ▲]

Detailed reference viewed: 10 (3 ULg)
Full Text
Peer Reviewed
See detailImplementation of SFC for the quality control of pharmaceuticals
Dispas, Amandine ULg; Andri, Bertyl ULg; Lebrun, Pierre ULg et al

Conference (2017, May 17)

Detailed reference viewed: 7 (0 ULg)
Full Text
See detailRencontre avec Pascal Matthey
Crucifix, Benoît ULg

Speech/Talk (2017)

Detailed reference viewed: 19 (1 ULg)
Peer Reviewed
See detailL'interpellation stigmatisante comme élément de construction identitaire: le cas "Django Unchained"
Wintgens, Caroline ULg

Conference (2017, May 17)

La polémique apparue autour du film Django Unchained de Quentin Tarantino (2012) permet d’approcher la question de la représentation du stigmate. Mon étude portant sur cette polémique et sur les arguments ... [more ▼]

La polémique apparue autour du film Django Unchained de Quentin Tarantino (2012) permet d’approcher la question de la représentation du stigmate. Mon étude portant sur cette polémique et sur les arguments y étant mobilisés a montré que c’est la représentation d’éléments issus de la culture afro-américaine, ayant participé à la construction d’une identité pour les individus porteurs d’un stigmate ethnique, qui est particulièrement mise en cause. La polémique devient dès lors le lieu d’une resignification des attributs liés au stigmate et d’une réaffirmation de la culture de résistance élaborée autour de celui-ci par ceux qui en sont porteurs. Le terme Nigger et sa présence excessive dans le film ont notamment été relevés par de nombreux internautes. C’est dans ce cadre que nous approcherons la question toujours centrale de l’interpellation stigmatisante, en tant qu’elle semble à la fois devenir le lieu d’une réaffirmation identitaire et permettre l’émergence d’une « réponse habilitante » (Butler, 2008). [less ▲]

Detailed reference viewed: 13 (1 ULg)
Full Text
See detailA Journey Through Julia: A dynamic and fast language
Cuvelier, Thibaut ULg

Speech/Talk (2017)

Usually, dynamic programming languages (like Python, R, or MATLAB) are quite slow when executed, which causes performance problems in many applications. Julia is a blossoming language, both dynamic and ... [more ▼]

Usually, dynamic programming languages (like Python, R, or MATLAB) are quite slow when executed, which causes performance problems in many applications. Julia is a blossoming language, both dynamic and fast, fully open source, with a syntax that is very similar to that of MATLAB. This talk presents briefly Julia and its ecosystem. [less ▲]

Detailed reference viewed: 9 (2 ULg)
Full Text
See detailModulation of NMDA receptor mediated excitatory synaptic currents in dopamine neurons of the substantia nigra
Destreel, Geoffrey ULg; Seutin, Vincent ULg; Engel, Dominique ULg

Poster (2017, May 17)

Dopamine (DA) neurons of the substantia nigra pars compacta (SNc) exhibit two main firing modes, spontaneous single action potential (AP) firing and bursting. The amount of DA released by these neurons in ... [more ▼]

Dopamine (DA) neurons of the substantia nigra pars compacta (SNc) exhibit two main firing modes, spontaneous single action potential (AP) firing and bursting. The amount of DA released by these neurons in target areas depends on the presynaptic AP firing pattern and is essential to modulate several aspects of behavior such as the control of movement. Bursting activity is mediated by excitatory afferents and specifically by the activation of NMDA receptors (NMDARs). However, the level of activation of NMDARs at these synapses during spontaneous synaptic activity is unknown. We assessed the occupancy of the glycine binding sites of the NMDAR by testing the effects of coagonists and by blocking the uptake of glycine on spontaneous excitatory postsynaptic currents (sEPSCs) in DA neurons of the SNc. Parasagittal midbrain slices (300 – 350 µm thickness) were cut from the brains 16- to 26- days old Wistar rats using a vibratome. Whole-cell recordings were made using warm (~35C°) standard artificial cerebrospinal fluid. sEPSCs were pharmacologically isolated and recorded at +40 and -70 mV. A large NMDAR-sEPSC component was present at +40 mV as revealed by the application of 50 µM D-AP5 (n=8, P < 0.001). At -70 mV, D-AP5 had no effect on the EPSC, as expected (n=7, P = 0.52). The mean amplitude of the average NMDAR sEPSC measured at +40 mV increased significantly from 8.6 ± 0.8 pA in control conditions to 10.9 ± 1.0 pA during bath application of 300 μM glycine (n=10, P < 0.001). We also investigated the effect of D-serine, the other coagonist at the NMDAR glycine site. The mean NMDAR EPSC amplitude measured at +40 mV showed a tendency toward larger values, from 6.8 ± 0.8 pA in control conditions to 8.8 ± 1.1 pA in the presence of 100 µM D-serine (n=4). Blockade of the glycine transporter-1 (GlyT1) significantly increased the mean amplitude of NMDAR sEPSCs measured at +40 mV from 7.1 ± 0.5 pA in control conditions to 10.5 ± 0.8 pA in the presence of 5 μM NFPS (n=8, P < 0.001). At -70 mV, NFPS had no effect on the AMPAR-sEPSC component, as expected (n=8, P = 0.23). In conclusion, our results indicate that the NMDAR glycine sites are not saturated by glycine and D-serine during sEPSCs in control conditions. [less ▲]

Detailed reference viewed: 29 (18 ULg)
Peer Reviewed
See detailNON-INVASIVE ANALYSIS OF POTENTIALLY DYSREGULATED MIRNAS IN ENDOMETRIOSIS
Munaut, Carine ULg; Emonard, Violaine; TIMMERMANS, Marie ULg et al

Conference (2017, May 17)

Detailed reference viewed: 16 (3 ULg)