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See detailThe electrophysiology of migraine
Ambrosini, A.; Schoenen, Jean ULg

in Current Opinion in Neurology (2003), 16(3), 327-331

Purpose of review The pathophysiology of migraine is far from being understood. Electrophysiological methods are useful to investigate peripheral and central mechanisms underlying this disorder. The ... [more ▼]

Purpose of review The pathophysiology of migraine is far from being understood. Electrophysiological methods are useful to investigate peripheral and central mechanisms underlying this disorder. The purpose of this review is to highlight the results of electrophysiological studies published during the last year and to examine their added value to our previous knowledge. Recent findings Studies by visual and auditory evoked potentials and event-related responses suggested that lack of habituation is the principal interictal abnormality of sensory processing in migraineurs. Recently confirmed for somatosensory and laser-evoked cortical potentials and for brainstem responses, it is also responsible for the increased intensity dependence of auditory evoked potentials. This abnormality is possibly caused by a reduced cortical preactivation level due to hypofunctioning subcortico-cortical aminergic pathways. Although studies of cortical excitability by transcranial magnetic stimulation have yielded conflicting results, results obtained using habituation of pattern-reversal visual evoked potentials to explore cortical excitability changes induced by repetitive transcranial magnetic stimulation strongly favour the hypothesis that migraine is characterized by a decreased level of preactivation excitability. With regard to pain mechanisms in migraine, electrophysiological studies of trigeminal pathways using nociceptive blink and corneal reflexes have confirmed that sensitization of central trigeminal nociceptors occurs during the attack, and may even persist interictally. Summary Scientific publications over the last year confirmed that electrophysiological methods are particularly suited to unravelling some of the pathophysiological mechanisms of migraine. To improve their future contribution, they need to be better standardized and to be correlated with behavioural, metabolic and genetic studies. [less ▲]

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See detailThe electroreduction of acrylonitrile : a new insight into the mechanism
Mertens, Marc; Calberg, Cédric ULg; Martinot, Lucien et al

in Macromolecules (1996), 29(14), 4910-4918

Several complementary electrochemical techniques have been used in order to clear up the mechanism of the electrochemical reduction of acrylonitrile (AN) on nickel. According to Lecayon et al., the ... [more ▼]

Several complementary electrochemical techniques have been used in order to clear up the mechanism of the electrochemical reduction of acrylonitrile (AN) on nickel. According to Lecayon et al., the electropolymerization of AN occurs in acetonitrile in the presence of tetraethylammonium perchlorate in such a way that polyacrylonitrile (PAN) is “grafted” onto the cathode. This electrochemical reaction has been reinvestigated both in acetonitrile, a nonsolvent of PAN, and in N,N-dimethylformamide (DMF), a good solvent for the polymer. The key role of the reduction potential on the electrografting reaction has been emphasized. The two electrochemical phenomena previously reported by Lecayon et al. have indeed been confirmed, but now it is clear that the “electrografting” of PAN selectively occurs at the less cathodic potential. At this potential, a PAN film is formed by a radical process and firmly secured onto the electrode, even in DMF. If the cathodic potential is further increased, the PAN film is easily removed from the metal and dissolves quickly in DMF. The transfer of one electron from the metal to the monomer occurs when the reduction is carried out at the more cathodic potential. A nonadherent PAN film is then formed onto Ni in acetonitrile, although the AN polymerization occurs in solution when acetonitrile is replaced by DMF. The AN polymerization is then consistent with an anionic process. [less ▲]

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See detailElectroresistance Effect in Ferroelectric Tunnel Junctions with Symmetric Electrodes
Bilc, Daniel ULg; Novaes, F. D.; Iniguez, J. et al

in ACS Nano (2012), 6(2), 1473-1478

Understanding the effects that govern electronic transport in ferroelectric tunnel junctions (FTJs) is of vital importance to improve the efficiency of devices such as ferroelectric memories with ... [more ▼]

Understanding the effects that govern electronic transport in ferroelectric tunnel junctions (FTJs) is of vital importance to improve the efficiency of devices such as ferroelectric memories with nondestructive readout. However, our current knowledge (typically based on simple semiempirical models or first-principles calculations restricted to the limit of zero bias) remains partial, which may hinder the development of more efficient systems. For example, nowadays it is commonly believed that the tunnel electroresistance (TER) effect exploited in such devices mandatorily requires, to be sizable, the use of two different electrodes, with related potential drawbacks concerning retention time, switching, and polarization imprint. In contrast, here we demonstrate at the first-principles level that large TER values of about 200% can be achieved under finite bias in a prototypical FTJ with symmetric electrodes. Our atomistic approach allows us to quantify the contribution of different microscopic mechanisms to the electroresistance, revealing the dominant role of the inverse piezoelectric response of the ferroelectric. On the basis of our analysis, we provide a critical discussion of the semiempirical models traditionally used to describe FTJs. [less ▲]

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See detailElectrospinning and nanofibers
Sorlier, Pierre; Grignard, Bruno ULg; Mitu, Alina et al

Poster (2007, August 31)

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See detailElectrospinning of a functional perfluorinated block copolymer as a powerful route for imparting superhydrophobicity and corrosion resistance to aluminum substrates
Grignard, Bruno ULg; Vaillant, Alexandre; de Coninck, Joel et al

in Langmuir (2011), 27(1), 335-342

Superhydrophobic aluminum surfaces with excellent corrosion resistance were successfully prepared by electrospinning of a novel fluorinated diblock copolymer solution. Micro- and nanostructuration of the ... [more ▼]

Superhydrophobic aluminum surfaces with excellent corrosion resistance were successfully prepared by electrospinning of a novel fluorinated diblock copolymer solution. Micro- and nanostructuration of the diblock copolymer coating was obtained by electrospinning which proved to be an easy and cheap electrospinning technology to fabricate superhydrophobic coating. The diblock copolymer is made of poly(heptadecafluorodecylacrylate-co-acrylic acid) (PFDA-co-AA) random copolymer as the first block and polyacrylonitrile (PAN) as the second one. The fluorinated block promotes hydrophobicity to the surface by reducing the surface tension, while its carboxylic acid functions anchor the polymer film onto the aluminum surface after annealing at 130 °C. The PAN block of this copolymer insures the stability of the structuration of the surface during annealing, thanks to the infusible character of PAN. It is also demonstrated that the so-formed superhydrophobic coating shows good adhesion to aluminum surfaces, resulting in excellent corrosion resistance. [less ▲]

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See detailElectrospinning of biocompatible polymers for potential biomdical applications
Croisier, Florence ULg; Zalfen, Alina; Aqil, Abdelhafid ULg et al

Poster (2008, June 23)

Detailed reference viewed: 22 (2 ULg)
See detailElectrospray mass spectrometry of noncovalent complexes between small molecule ligands and nucleic acids
Gabelica, Valérie ULg

in Joseph H., Banoub; Patrick A., Limbach (Eds.) Mass spectrometry of nucleosides and nucleic acids (2010)

CONTENTS 8.1 Introduction 8.1.1 ESI-MS of Noncovalent Complexes 8.1.2 Nucleic Acid Targeting by Small Molecules 8.2 Electrospray Mass Spectrometry of Nucleic Acid Noncovalent Complexes 8.2.1 ... [more ▼]

CONTENTS 8.1 Introduction 8.1.1 ESI-MS of Noncovalent Complexes 8.1.2 Nucleic Acid Targeting by Small Molecules 8.2 Electrospray Mass Spectrometry of Nucleic Acid Noncovalent Complexes 8.2.1 Stoichiometries: Number of Strands and Detection of Nucleic Acid Higher-Order Structures 8.2.2 Stoichiometries: Number of Bound Ligands 8.2.3 Role of Cations in Nucleic Acid Structure and Ligand Binding 8.2.4 Determination of Equilibrium Binding Constants 8.2.5 Are the Relative Intensities Proportional to the Abundances in Solution? 8.3 Characterizing Noncovalent Ligand Binding by MS/MS of the Complexes 8.3.1 Overview of Dissociation Pathways 8.3.2 How Observed Pathways Depend on Instrumental Parameters 8.3.3 How Observed Pathways Depend on Ligand Binding 8.3.4 Probing the Energetics of Ligand-DNA Interactions 8.3.5 Determining the Ligand Binding Mode 8.3.6 Determining the Ligand Binding Site by MS/MS 8.4 Conclusion and Outlook References [less ▲]

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See detailElectrospray Mass Spectrometry of Telomeric RNA (TERRA) Reveals the Formation of Stable Multimeric G-Quadruplex Structures
Collie, Gavin W.; Parkinson, Gary N.; Neidle, Stephen et al

in Journal of the American Chemical Society (2010), 132(27), 93289334

We report on the self-assembled structures formed by 12-mer, 22-mer, and 45-mer telomeric RNA (telRNA/TERRA) sequences compared to their DNA analogues, as studied by electrospray mass spectrometry ... [more ▼]

We report on the self-assembled structures formed by 12-mer, 22-mer, and 45-mer telomeric RNA (telRNA/TERRA) sequences compared to their DNA analogues, as studied by electrospray mass spectrometry, circular dichroism, and thermal denaturation. The major difference between telomeric RNA and DNA sequences is the ability of telomeric RNA to form higher-order dimeric assemblies, initiated by cation-mediated stacking of two parallel G-quadruplex subunits. The 5′-5′ stacking had been observed recently by NMR for the r(GGGUUAGGGU) 10-mer (Martadinata, H.; Phan, A. T. J. Am. Chem. Soc. 2009, 131, 2570); the present work shows that stacking also occurs for the 22-mer containing four G-tracts and for the 45-mer containing eight G-tracts, suggesting a general structural feature of telomeric RNA. The importance of kinetic effects in multimer formation, unfolding, and structural rearrangements is also highlighted. [less ▲]

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See detailElectrospray Mass Spectrometry Study of Selective Complexes of Polyammonium Macrotricyclic Ligands with Dicarboxylic Acids
Collette, Caroline ULg; Meunier, Cécile; De Pauw, Edwin ULg et al

in Rapid Communications in Mass Spectrometry : RCM (1997), 11

Macrocyclic and macropolycyclic polyammonium host molecules have been shown to complex a variety of inorganic and organic anions strongly and selectively. The selectivity of the complexation depends on ... [more ▼]

Macrocyclic and macropolycyclic polyammonium host molecules have been shown to complex a variety of inorganic and organic anions strongly and selectively. The selectivity of the complexation depends on the substrate lenght and on the size of the host cavity of the macrocycle. We describe in this article the analysis of the complexation of dicarboxylic acid substrates by a macrotricyclic host using electrospray mass spectrometry. [less ▲]

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See detailElectrospray Mass Spectrometry to Study Drug-Nucleic Acids Interactions
Rosu, Frédéric ULg; De Pauw, Edwin ULg; Gabelica, Valérie ULg

in Biochimie (2008), 90(7), 1074-1087

We present here a tutorial review on the electrospray mass spectrometry technique and its applications to the study of drug-nucleic acid non-covalent complexes. Particular emphasis has been made on the ... [more ▼]

We present here a tutorial review on the electrospray mass spectrometry technique and its applications to the study of drug-nucleic acid non-covalent complexes. Particular emphasis has been made on the basic principles of the technique, to allow even the non-specialist to design fit-for-purpose mass spectrometry experiments and interpret the results. Standard applications will be described in detail, including the determination of stoichiometries and equilibrium binding constants of non-covalent complexes, the study of binding kinetics, and the development of ligand screening assays. We also outline the potentials of more advanced and/or more recent MS-based techniques (tandem mass spectrometry, ion mobility spectrometry and gas-phase spectroscopy) for the study of the nucleic acid-ligand complexes. [less ▲]

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See detailElectrostatic analysis of moving conductors using a finite element perturbation method
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in Proceedings of the 13th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC2008) (2008, May)

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See detailElectrostatic Analysis of Moving Conductors Using a Perturbation Finite Element Method
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in IEEE Transactions on Magnetics (2009), 45(3), 1004-1007

This paper deals with the analysis of electrostatic problems involving moving devices by means of a perturbation finite element method. A reference problem without any moving parts is first solved and ... [more ▼]

This paper deals with the analysis of electrostatic problems involving moving devices by means of a perturbation finite element method. A reference problem without any moving parts is first solved and gives the source for a sequence of perturbation problems in subdomains restricted to the neighborhood of these parts. The source accounts for all the previous calculations for preceding positions what increases the efficiency of the simulations. This proposed approach also improves the computation accuracy and decreases the complexity of the analysis of moving conductors thanks to the use of independent and adaptively refined meshes. [less ▲]

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See detailElectrostatic complexation as a driving force for the self-association of double hydrophilic diblock copolymers in water
Gohy, Jean-François; Mores, Sandrine; Antoun, Sayed et al

Poster (2003, May 16)

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See detailElectrostatic coupling of MEMS structures: transient simulations and dynamic pull-in
Rochus, Véronique ULg; Rixen, Daniel J.; Golinval, Jean-Claude ULg

in Nonlinear Analysis (2005), 63

In micro-electromechanical systems (MEMS), coupling of structures through electrostatic forces is a primordial phenomenon. Simulating the dynamics of MEMS and taking into account such strong coupling ... [more ▼]

In micro-electromechanical systems (MEMS), coupling of structures through electrostatic forces is a primordial phenomenon. Simulating the dynamics of MEMS and taking into account such strong coupling effects allows one to predict dynamical performance and stability, and is therefore an essential issue in the design of highly effective and reliable devices. Analysis techniques for such systems require special attention in order to provide to the designer accurate and fast tools.We propose a finite element approach (FEM) that properly handles the strong electromechanical coupling in MEMS. In the simulation example of a micro-bridge, we show that such simulation techniques can reveal complex dynamical behaviors of MEMS such as dynamic pull-in. [less ▲]

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See detailElectrostatic Coupling of MEMs Structures: Transient Simulations and Dynamic Pull-in
Rochus, Véronique ULg; Rixen, Daniel J.; Golinval, Jean-Claude ULg

Conference given outside the academic context (2004)

In Micro-electromechanical systems (MEMS) coupling of structures through electrostatic forces is a primordial phenomenon. Simulating the dynamics of MEMS and taking into account such strong coupling ... [more ▼]

In Micro-electromechanical systems (MEMS) coupling of structures through electrostatic forces is a primordial phenomenon. Simulating the dynamics of MEMS and taking into account such strong coupling effects allows to predict dynamical performance and stability, and is therefore an essential issue in design of highly effective and reliable devices. Analysis techniques for such systems require special attention in order to provide to the designer accurate and fast tools. We propose a finite element approach (FEM) that properly handles the strong electromechanical coupling in MEMS. In the simulation example of a micro-bridge, we show that such simulation techniques can reveal complex dynamical behaviors of MEMS such as dynamic pull-in. [less ▲]

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See detailElectrostatic hierarchical co-assembly in aqueous solutions of two oppositevely charged double hydrophilic diblock copolymers
Voets, Ilja K.; de Keizer, Arie; Leermakers, Frans A. M. et al

in European Polymer Journal (2009), 45(10), 2913-2925

The formation of spherical micelles in aqueous solutions of poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP-b-PEO and poly(acrylic acid)-block-poly(vinyl alcohol), PAA-b-PVOH ... [more ▼]

The formation of spherical micelles in aqueous solutions of poly(N-methyl-2-vinyl pyridinium iodide)-block-poly(ethylene oxide), P2MVP-b-PEO and poly(acrylic acid)-block-poly(vinyl alcohol), PAA-b-PVOH has been investigated with light scattering-titrations, dynamic and static light scattering, and 1H 2D Nuclear Overhauser Effect Spectroscopy. Complex coacervate core micelles, also called PIC micelles, block ionomer complexes, and interpolyelectrolyte complexes, are formed in thermodynamic equilibrium under charge neutral conditions (pH 8, 1 mM NaNO3, T = 25 °C) through electrostatic interaction between the core-forming P2MVP and PAA blocks. 2D 1H NOESY NMR experiments show no cross-correlations between PEO and PVOH blocks, indicating their segregation in the micellar corona. Self-consistent field calculations support the conclusion that these C3Ms are likely to resemble a ‘patched micelle’; that is, micelles featuring a ‘spheres-on-sphere’ morphology. [less ▲]

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See detailElectrostatic potential maps at the quantum chemistry level of the active sites of the serine peptidases, α-chymotrypsin and subtilisin
Lamotte-Brasseur, Josette; Dive, Georges ULg; Dehareng, Dominique ULg et al

in Journal of Theoretical Biology (1990), 145(2), 183-98

The electronic properties of the active-sites of the structurally unrelated serine peptidases, alpha-chymotrypsin and subtilisin, have been expressed in the form of three-dimensional electrostatic ... [more ▼]

The electronic properties of the active-sites of the structurally unrelated serine peptidases, alpha-chymotrypsin and subtilisin, have been expressed in the form of three-dimensional electrostatic potential maps derived from integrals calculated at the quantum chemistry level. As a consequence of the asymmetrical distribution of the secondary structures that occur within a 7 A sphere around the serine of the catalytic triad, the active sites are highly polarized entities and exhibit large dipole moments. One part of the active sites generates a nucleophilic suction-pump. Its isocontour at -10 kcal mol-1 defines an impressive, negatively-charged volume which bears a narrow channel in the immediate vicinity of the active-site serine 195 in alpha-chymotrypsin or 221 in subtilisin. In native alpha-chymotrypsin, there is a perfect complementation between this nucleophilic suction-pump and the positively-charged electrophilic hole that is generated by the backbone NH of Ser 195 and Gly 193. In subtilisin, generation of the complementing electrophilic hole requires binding of a carbonyl donor ligand and may be achieved by rotation of the side-chain amide of Asn 155 towards the backbone NH of Ser 221. Small variations in the atomic co-ordinates of alpha-chymotrypsin used for the calculations, the presence of water molecules in its active site and the occurrence of point mutations in the amino acid sequence of subtilisin have little effects on the shape and characteristics of the electrostatic potential. [less ▲]

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See detailElectrostatic Simulation using XFEM for Conductor and Dielectric Interfaces
Rochus, Véronique ULg; Rixen, Daniel; Van Miegroet, Laurent ULg et al

in International Journal for Numerical Methods in Engineering (2011), 85(10), 12071226

ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to ... [more ▼]

ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to evaluate accurately the electrostatic forces acting on the devices. Extended Finite Element (X-FEM) approaches can easily handle moving boundaries and interfaces in the electrostatic domain and seem therefore very suitable to model Micro-Electro-Mechanical Systems. In this study we investigate different X-FEM techniques to solve the electrostatic problem when the electrostatic domain is bounded by a conducting material. Preliminary studies in one-dimension have shown that one can obtain good results in the computation of electrostatic potential using X-FEM. In this paper the extension of these preliminary studies to 2D problem is presented. In particular a new type of enrichment functions is proposed in order to treat accurately Dirichlet boundary conditions on the interface. [less ▲]

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