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See detailElectrical transport and percolation in magnetoresistive manganite/insulating oxide composites: Case of La0.7Ca0.3MnO3/Mn3O4
Vertruyen, Bénédicte ULg; Cloots, Rudi ULg; Ausloos, Marcel ULg et al

in Physical Review. B (2007), 75(16), 165112

We report the results of electrical resistivity measurements carried out on well-sintered La0.7Ca0.3MnO3/Mn3O4 composite samples with almost constant composition of the magnetoresistive manganite phase ... [more ▼]

We report the results of electrical resistivity measurements carried out on well-sintered La0.7Ca0.3MnO3/Mn3O4 composite samples with almost constant composition of the magnetoresistive manganite phase (La0.7Ca0.3MnO3). A percolation threshold (phi c) occurs when the La0.7Ca0.3MnO3 volume fraction is ~ 0.19. The dependence of the electrical resistivity rho as a function of La0.7Ca0.3MnO3 volume fraction fLCMO can be described by percolationlike phenomenological equations. Fitting the conducting regime (fLCMO > phic) by the percolation power law rho # (fLCMO - phic)^(-t) returns a critical exponent value of 2.0±0.2 at room temperature and 2.6±0.2 at 5 K. The increase of t is ascribed to the influence of the grain boundaries on the electrical conduction process at low temperature. (C) 2007 The American Physical Society. [less ▲]

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See detailElectrical transport in saturated and conjugated molecular wires
Remacle, Françoise ULg; Levine, R. D.

in Faraday Discussions (2006), 131

The mechanism for charge transport in dithio molecular wires tethered between two gold electrodes is investigated, using both a steady state and a time-dependent quantum mechanical approach. The interface ... [more ▼]

The mechanism for charge transport in dithio molecular wires tethered between two gold electrodes is investigated, using both a steady state and a time-dependent quantum mechanical approach. The interface with the electrodes is modeled by two gold clusters and the electronic structure of the entire Au-n-S-bridge-S-Au-n system is computed ab initio at the DFT level and semi-empirically, with the extended Huckel theory. Current vs. applied bias, I-V, curves are computed using a scattering Landauer-type formalism in a steady state picture. The applied source-drain and gate voltages are included at the ab initio level in the electronic Hamiltonian and found to influence strongly the I-V characteristics. The time evolution of a non stationary electronic wave packet initially localized on a gold atom at one end of the extended system shows that charge transfer proceeds sequentially, by a hopping mechanism, to the opposite end. Analysis of the effective one electron Hamiltonian matrix shows that the sulfur atom endows a resistive character to the Au-C-S junctions. The S atoms are however rather well coupled to both the gold and carbon atoms so that typically the super exchange limit for electron transfer is not reached unless the molecular bridge is saturated and the Fermi window function is narrow. [less ▲]

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See detailElectrically addressing a molecule-like donor pair in silicon: An atomic scale cyclable full adder logic
YAN, Yonghong; Mol, J. A.; Verduijn, J. et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2010), 114

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See detailElectrification Rurale. Vers une technique innovatrice pour l'Afrique.
Lilien, Jean-Louis ULg; omboua, Alphonse

in Revue d'electricité et d'électronique industrielle (2006), N°1-2006

In many developing countries , there are a lot of high voltage lines which cross many regions to supply electricity to the main towns or connect to networks the distanced electric substations . These ... [more ▼]

In many developing countries , there are a lot of high voltage lines which cross many regions to supply electricity to the main towns or connect to networks the distanced electric substations . These lines, used for supplying electricity to big towns, cross a lot of villages whose people broadly poor hope to be supplied with electricity without a suitable solution. However it seems very deplorable that the power conducted by these lines doesn’t profit to surrounding population. Unfortunately , for these villages , the use of classical substations is too expensive to the power distributors because of high cost of investment and production for these potential scattered consumers with the low demand of electricity. This paper presents the original solution settled in 2002 in one of the village located in Congo Brazzaville and continue to operate correctly in 2006. It is a new power transformer, based on the technique of SF6 measuring transformer, which is connected on one phase of the high voltage line 220kV and which produces the low voltage 230 V directly useful by the rural population. This prototype sample for the rural electrification has been designed to deliver a power of 50kVA. A cheap and robust system ! It requires a large popularization, mainly in sub saharian Africa that has got many such opportunities. Outside the role of bulk power transmission, the high voltage line is now also able to distribute a part of it. [less ▲]

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See detailElectro-assisted assembly of aliphatic thiol, dithiol and dithiocarboxylic acid monolayers on copper
Maho, A.; Denayer, Jessica ULg; Delhalle, J. et al

in Electrochimica Acta (2011), 56(11), 3954-3962

Molecular assemblies of organothiol molecules on polycrystalline copper surfaces are a well known process to confer them specific organizational and protective properties. In this paper, an original and ... [more ▼]

Molecular assemblies of organothiol molecules on polycrystalline copper surfaces are a well known process to confer them specific organizational and protective properties. In this paper, an original and promising approach is considered through an electro-assisted adsorption process via a cathodic polarization of the copper substrate. Spectroscopic characterizations (PM-IRRAS, XPS) and electrochemical studies (CV, LSV, cathodic desorption, SECM) highlight and confirm the benefits brought by this methodology in terms of resulting SAMs features and considerable savings of preparation time. In addition to normal alkylthiols with a monopod anchoring group, alkyldithiocarboxylic acid and alkyldithiol monolayers - both bipodal - are characterized with the prospect of forming either easier to remove or more adherent films, respectively. © 2011 Elsevier Ltd. All rights reserved. [less ▲]

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See detailElectro-mechanical Coupling in MEMS: Modeling and Experimental Validation
Rochus, Véronique ULg; Golinval, Jean-Claude ULg

Scientific conference (2007)

This paper presents the advantages of a strong coupled formulation to model the electro-mechanical coupling appearing in MEMS. The classical modeling approach is to use a staggered methodology iterating ... [more ▼]

This paper presents the advantages of a strong coupled formulation to model the electro-mechanical coupling appearing in MEMS. The classical modeling approach is to use a staggered methodology iterating between two different programs to obtain the solution of the coupled problem. In this research a strong coupled formulation is proposed and a tangent stiffness matrix of the whole problem is computed. Using this matrix, nonlinear algorithms such as the Riks-Crisfield algorithm may be applied to solve the static nonlinear problem and accurately determine the static pull-in voltage. Moreover, the natural frequencies may be computed around each equilibrium positions. The dynamic behavior of the structure may also be studied and two new parameters are defined: the dynamic pull-in voltage and the dynamic pull-in time. This strong coupled methodology deriving from variational principle may also be used for topology optimization and extended finite elements. [less ▲]

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See detailElectro-Mechano-Fluidic Modelling of Microsystems using Finite Elements
Rochus, V.; Gutschmidt, S.; Cardona, A. et al

in Proceedings of the 18th Conference on the Computation of Electromagnetic Fields (COMPUMAG 2011) (2011, July)

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See detailElectro-Mechano-Fluidic Modelling of Microsystems using Finite Elements
Rochus, V.; Gutschmidt, S.; Cardona, A. et al

in IEEE Transactions on Magnetics (2012), 48(2), 355-358

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See detailElectro-optic coefficient measurements : correction of electric-field inhomogeneities in the transverse configuration
Lemaire, Philippe; Georges, Marc ULg

in Optics Letters (1992), 17(20), 1411-1413

The problem of electric-field inhomogeneities in the measurement of the electro-optic coefficient in the transverse configuration is well known. We present a simple way to solve these difficulties. It ... [more ▼]

The problem of electric-field inhomogeneities in the measurement of the electro-optic coefficient in the transverse configuration is well known. We present a simple way to solve these difficulties. It involves local measurements at several points along the transverse direction of the phase difference between two components of light traveling through the crystal. The electro-optic coefficient is simply calculated by integrating the phase shifts along the transverse profile. For this procedure one needs nothing but the value of the voltage applied to the crystal, and knowledge of the internal electric field is not necessary. Limits of application are discussed, and results are shown for photorefractive sillenite crystals. [less ▲]

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See detailElectroantennogram of Culex quinquefasciatus Say (Diptera:Culicidae) to chemical compounds from fermented infusions and improvement of gravid mosquito trapping
Latte, Nicolas ULg

Master's dissertation (2006)

The urban mosquito Culex quinquefasciatus Say (Diptera: Culicidae) uses chemicals to locate suitable water pools for oviposition. These chemicals when identified can be used to trap gravid female ... [more ▼]

The urban mosquito Culex quinquefasciatus Say (Diptera: Culicidae) uses chemicals to locate suitable water pools for oviposition. These chemicals when identified can be used to trap gravid female mosquitoes. Experiments in Davis and in Sacramento (California, in the United States) were made to improve the trapping efficiency of Reiter/Cumming gravid traps baited by several attractants (or attractant blends). Unfortunately, it appeared that the number of gravid female mosquitoes collected was not sufficient to differentiate the efficacy of attractant blends tested by statistical analysis. However, a positive correlation between the total mosquito number collected daily and the highest humidity shows that the mosquito oviposition activity seems to be influenced by the humidity during the night. Observations on total number of mosquitoes and the highest temperature seem to reveal a threshold temperature which is critical for the adult mosquito survival. A coupled gas chromatography – electronantennography (GC-EAD) protocol was also developed step by step in order to find new Culex quinquefasciatus oviposition attractants. After obtaining repetitive electroantennographic (EA) response, two comparison experiments (SPME fiber type and infusion type) were made to finalize the specific GC-EAD/SPME protocol. This with the aim to prospect new attractants from fermented Bermuda grass infusion. Analyses based on all results permit to distinguish the EA responses from random perturbations (electromagnetic and vibration). GC-EAD/SPME of Bermuda grass infusion analyses confirms the presence of 10 and the activity of 9 chemical compounds as established by Du and Millar in 1999. Furthermore, experiments on Culex quinquefasciatus performed with the new protocol, brought to light the EA activity of 10 other unknown chemicals, 7 of which are low molecular weight chemical compounds. These new chemicals have now to be identified and their ability to elicit EA responses still has to be confirmed. [less ▲]

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See detailElectrocardiographic changes during dobutamine stress testing in patients with recent myocardial infarction: relation with residual infarct artery stenosis and contractile recovery
Lancellotti, Patrizio ULg; Mipinda, J. B.; Pierard, L. A.

in Acta Cardiologica (2004), 59(1), 11-16

OBJECTIVE: The identification of viable but jeopardized myocardium after acute myocardial infarction (AMI) is of great importance for selecting patients who could benefit from a revascularization ... [more ▼]

OBJECTIVE: The identification of viable but jeopardized myocardium after acute myocardial infarction (AMI) is of great importance for selecting patients who could benefit from a revascularization procedure. The aim of the study was to determine the accuracy of the dobutamine stress electrocardiogram (ECG) 1) for detecting significant stenosis of the infarct-related artery and 2) for predicting the occurrence of contractile recovery. METHODS AND RESULTS: Ninety-four patients underwent dobutamine stress ECG and quantitative angiography within the first week after AMI. A follow-up resting echocardiogram was obtained in all patients at 1 month. Significant stenosis of the infarct-related artery was detected in 76 patients and functional recovery occurred in 56 patients. Dobutamine stress induced ST-segment elevation in 44 patients, ST-segment depression in 17 and T-wave normalization in 34. Increase in QT dispersion and dobutamine ST elevation were more sensitive than chest pain and ST-segment depression (79% and 53% vs. 24% and 17%, respectively; p<0.05) for detecting significant infarct-related artery stenosis. Four independent variables were selected for predicting contractile recovery: > or = 20 ms increase in QT dispersion from baseline to low-dose dobutamine (p = 0.00016), dobutamine-induced ST-segment elevation (p = 0.0009), elective angioplasty of the infarct-related artery (p = 0.001) and T-wave normalization (p = 0.005). CONCLUSIONS: The analysis of predischarge dobutamine stress ECG is useful for predicting residual stenosis of the infarct-related artery and contractile recovery in the affected area. QT dispersion changes during the test are the most accurate parameter. [less ▲]

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See detailElectrochemical and PM-IRRAS characterization of cholera toxin binding at a model biological membrane.
Leitch, J. Jay; Brosseau, Christa L.; Roscoe, Sharon G. et al

in Langmuir : the ACS journal of surfaces and colloids (2013), 29(3), 965-76

A mixed phospholipid-cholestrol bilayer, with cholera toxin B (CTB) units attached to the monosialotetrahexosylganglioside (GM1) binding sites in the distal leaflet, was deposited on a Au(111) electrode ... [more ▼]

A mixed phospholipid-cholestrol bilayer, with cholera toxin B (CTB) units attached to the monosialotetrahexosylganglioside (GM1) binding sites in the distal leaflet, was deposited on a Au(111) electrode surface. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements were used to characterize structural and orientational changes in this model biological membrane upon binding CTB and the application of the electrode potential. The data presented in this article show that binding cholera toxin to the membrane leads to an overall increase in the tilt angle of the fatty acid chains; however, the conformation of the bilayer remains relatively constant as indicated by the small decrease in the total number of gauche conformers of acyl tails. In addition, the bound toxin caused a significant decrease in the hydration of the ester group contained within the lipid bilayer. Furthermore, changes in the applied potential had a minimal effect on the overall structure of the membrane. In contrast, our results showed significant voltage-dependent changes in the average orientation of the protein alpha-helices that may correspond to the voltage-gated opening and closing of the central pore that resides within the B subunit of cholera toxin. [less ▲]

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See detailElectrochemical and spectroscopic study of the self-assembling mechanism of normal and chelating alkanethiols on copper
Dilimon, V. S.; Denayer, Jessica ULg; Delhalle, J. et al

in Langmuir (2012), 28(17), 6857-6865

The self-assembly of aliphatic thiol (RSH), dithiol (R(SH) 2), and dithiocarboxylic acid (RS 2H) onto mildly oxidized and highly oxidized copper was studied in real time by in situ electrochemical ... [more ▼]

The self-assembly of aliphatic thiol (RSH), dithiol (R(SH) 2), and dithiocarboxylic acid (RS 2H) onto mildly oxidized and highly oxidized copper was studied in real time by in situ electrochemical impedance spectroscopy (EIS). Ex situ characterization of the films was carried out using linear sweep voltammetry (LSV), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). In situ EIS studies found a very fast adsorption of RSH, R(SH) 2, and RS 2H (within 10-15 s). This fast adsorption step is followed by the long-term additional adsorption and consolidation of SAM. However, the self-assembly of RS 2H passes through an intermediate step of molecule rearrangement for around 10 to 30 min after around 2 to 7 min of self-assembly. The binding of both sulfur moieties of R(SH) 2 with Cu happens simultaneous. The oxide reduction capacity of RSH, R(SH) 2, and RS 2H was good. However, the XPS studies showed the decomposition of RS 2H-based SAMs to Cu 2S. Monolayers prepared on both mildly oxidized and heavily oxidized Cu with R(SH) 2 had the highest stability. Monolayers of RS 2H showed the least stability on both mildly oxidized and heavily oxidized Cu. Although RSH-based SAMs had good organization on both mildly oxidized and highly oxidized Cu, R(SH) 2-based SAMs did not show good organization in either case. The RS 2H monolayer had good organization only on mildly oxidized Cu. © 2012 American Chemical Society. [less ▲]

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See detailElectrochemical characterization of Pt/carbon xerogel and Pt/carbon aerogel catalysts
Job, Nathalie ULg; Maillard, F.; Marie, J. et al

Poster (2008, September 08)

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See detailElectrochemical formation of polypyrrole nanowires
Jérôme, Christine ULg; Labaye, David; Jérôme, Robert ULg

in Synthetic Metals (2004), 142(1-3), 207-216

This paper aims at approaching the mechanism of formation of polypyrrole (PPy) nanowires by an all-electrochemical process, which consists in electrografting a poly(alkylacrylate) film onto the surface of ... [more ▼]

This paper aims at approaching the mechanism of formation of polypyrrole (PPy) nanowires by an all-electrochemical process, which consists in electrografting a poly(alkylacrylate) film onto the surface of a cathode, followed by the anodic electropolymerization of pyrrole (Py) at the surface of this organomodified electrode. The experimental conditions for the pyrrole oxidation, including solvent and concentrations of monomer and supporting electrolyte, have been changed with the purpose to tune the characteristic features of the polypyrrole nanowires. The polyacrylate template has also been modified, all other conditions being the same, in an effort to design the shape and size of the wires. The electrochemical behavior of the as-prepared PPy wires has been characterized. [less ▲]

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See detailElectrochemical strategies for the strengthening of polymer – metal interfaces
Baute, Noëlle; Jérôme, Christine ULg; Martinot, Lucien et al

in European Journal of Inorganic Chemistry (2001), 2001(5), 1097-1107

Polymers have been widely used for the protection of metals against corrosion and for improving the performance of structural adhesive joints. In this contribution, the weakness and short-term durability ... [more ▼]

Polymers have been widely used for the protection of metals against corrosion and for improving the performance of structural adhesive joints. In this contribution, the weakness and short-term durability of these polymer-metal interactions and some common approaches for alleviating this problem are briefly reviewed. Among the existing techniques, electrochemical processes offer the advantage of controlled interfacial reactions. Promising results have been reported by Strat-mann et al. and Le´cayon et al., who have emphasized the interest and opportunity to create strong chemical bonds between the organic coating and the metallic substrate. Their work is discussed in this review, along with results recently obtained in our group [less ▲]

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