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See detailPhase separation during silica gel formation followed by time-resolved SAXS
Gommes, Cédric; Blacher, Silvia ULg; Goderis, Bart et al

in Nuclear Instruments & Methods in Physics Research. Section B, Beam Interactions with Materials and Atoms (2005), 238(1-4), 141-145

Time-resolved small angle X-ray scattering data are collected during the formation of silica gels from the base catalyzed polymerization of tetraethoxysilane in ethanol with 3-(2-aminoethylamino ... [more ▼]

Time-resolved small angle X-ray scattering data are collected during the formation of silica gels from the base catalyzed polymerization of tetraethoxysilane in ethanol with 3-(2-aminoethylamino)propyltrimethoxysilane and 3-aminopropyltriethoxysilane as additives. It is shown that a polymerization-induced spinodal demixing occurs during the gel formation. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailPhase shift effective range expansion from supersymmetric quantum mechanics
Samsonov, B. F.; Stancu, Floarea ULg

in Physical Review C (2003), 67(5), 054005

Supersymmetric or Darboux transformations are used to construct local phase equivalent deep and shallow potentials for lnot equal0 partial waves. We associate the value of the orbital angular momentum ... [more ▼]

Supersymmetric or Darboux transformations are used to construct local phase equivalent deep and shallow potentials for lnot equal0 partial waves. We associate the value of the orbital angular momentum with the asymptotic form of the potential at infinity, which allows us to introduce adequate long-distance transformations. The approach is shown to be effective in getting the correct phase shift effective range expansion. Applications are considered for the P-1(1) and D-1(2) partial waves of the neutron-proton scattering. [less ▲]

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See detailPhase slips in mesoscopic superconducting triangles
Schildermans, N.; Salenbien, R.; Silhanek, Alejandro ULg et al

in Physica C: Superconductivity (2008), 468(7-10), 757-760

Voltage-current (V(I)) characteristics are investigated in the superconducting state of an equilateral triangle of 2.2 mu m(2) area. Several steps in the V(I) curves indicate the presence of phase slip ... [more ▼]

Voltage-current (V(I)) characteristics are investigated in the superconducting state of an equilateral triangle of 2.2 mu m(2) area. Several steps in the V(I) curves indicate the presence of phase slip centers in the triangle. The field dependence of these steps follows the Little-Parks oscillations of the phase boundary, associated with the change of vorticity. The influence of the contacts manifests itself as an excess voltage and a negative differential resistance. In addition we show that the position of the current contacts modify the superconducting phase boundary measurements. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailPhase stability of Triphylite, LiFePO4, and the Phases of the Mason-Quensel-Sequence
Schmid-Beurmann, Peter ULg; Moavenian, M.; Hatert, Frédéric ULg

in Berichte der Deutschen Mineralogischen Gesellschaft : Beihefte zum European Journal of Mineralogy (2004), 16

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See detailPhase transition and thermodynamics of a hot and dense system in a scaled NJL model
Cugnon, Joseph ULg; Jaminon, Martine ULg; Van den Bossche, Bruno

in Nuclear Physics A (1996), 598

he chiral phase transition of a hot and dense system of quarks is studied within a modified SU(3) NJL Lagrangian that implements the QCD scale anomaly. The u- and s-quark condensates can or can not feel ... [more ▼]

he chiral phase transition of a hot and dense system of quarks is studied within a modified SU(3) NJL Lagrangian that implements the QCD scale anomaly. The u- and s-quark condensates can or can not feel the same chiral restoration depending on the considered region of the three-dimensional space (Tc, muuc, musc). The temperature behaviour of the pressure and the energy and entropy densities of the u- and s-quark system is investigated. At high temperature, the non-vanishing bare s-quark mass only modifies slightly the usual behaviour associated with an ideal quark gas. [less ▲]

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See detailPhase transition in granular gases
Terwagne, Denis ULg; Frère, Benjamin; Masabo, Jean-Pierre et al

Conference (2005, April)

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See detailPhase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra
McGuire, Michael A; Christianson, Andrew D; Sefat, Athena S et al

in Physical Review. B (2008), 78(9),

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal ... [more ▼]

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonal-orthorhombic crystallographic phase transition at similar to 160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder x-ray and neutron-diffraction measurements is presented. A magnetic moment of similar to 0.35 mu(B) per iron is derived from Mossbauer spectra in the low-temperature phase. Evidence of the structural transition is observed at temperatures well above the transition temperature (up to near 200 K) in the diffraction data as well as the polycrystalline elastic moduli probed by resonant ultrasound spectroscopy measurements. The effects of the two phase transitions on the transport properties (resistivity, thermal conductivity, Seebeck coefficient, and Hall coefficient), heat capacity, and magnetization of LaFeAsO are also reported, including a dramatic increase in the magnitude of the Hall coefficient below 160 K. The results suggest that the structural distortion leads to a localization of carriers on Fe, producing small local magnetic moments which subsequently order antiferromagnetically upon further cooling. Evidence of strong electron-phonon interactions in the high-temperature tetragonal phase is also observed. [less ▲]

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See detailPhase transitions in vibrated granular systems in microgravity
Opsomer, Eric ULg; Vandewalle, Nicolas ULg; Ludewig, François ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2011)

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See detailPhase-Change Materials: Vibrational Softening upon Crystallization and Its Impact on Thermal Properties
Matsunaga, Toshiyuki; Yamada, Noboru; Kojima, Rie et al

in Advanced Functional Materials (2011), 21(12), 2232-2239

Crystallization of an amorphous solid is usually accompanied by a significant change of transport properties, such as an increase in thermal and electrical conductivity. This fact underlines the ... [more ▼]

Crystallization of an amorphous solid is usually accompanied by a significant change of transport properties, such as an increase in thermal and electrical conductivity. This fact underlines the importance of crystalline order for the transport of charge and heat. Phase-change materials, however, reveal a remarkably low thermal conductivity in the crystalline state. The small change in this conductivity upon crystallization points to unique lattice properties. The present investigation reveals that the thermal properties of the amorphous and crystalline state of phase-change materials show remarkable differences such as higher thermal displacements and a more pronounced anharmonic behavior in the crystalline phase. These findings are related to the change of bonding upon crystallization, which leads to an increase of the sound velocity and a softening of the optical phonon modes at the same time. [less ▲]

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See detailPhase-resolved observations of a peculiar O star
Nazé, Yaël ULg

Poster (2006)

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See detailPhase-resolved X-ray and optical spectroscopy of the massive binary HD 93403
Rauw, Grégor ULg; Vreux, Jean-Marie ULg; Stevens, I. R. et al

in Astronomy and Astrophysics (2002), 388(2), 552-562

We report the first results of a campaign aimed at the study of early-type binaries with the XMM-Newton observatory. Phase-resolved EPIC spectroscopy of the eccentric binary HD93403 reveals a clear ... [more ▼]

We report the first results of a campaign aimed at the study of early-type binaries with the XMM-Newton observatory. Phase-resolved EPIC spectroscopy of the eccentric binary HD93403 reveals a clear orbital modulation of the X-ray luminosity as a function of the orbital phase. Below 1.0 keV, the observed X-ray flux is modulated by the opacity of the primary wind. Above 1.0 keV, the observed variation of the X-ray flux is roughly consistent with a 1/r dependence expected for an adiabatic colliding wind interaction. HD93403 appears less overluminuous in X-rays than previously thought and a significant fraction of the total X-ray emission arises probably within the winds of the individual components of the binary. Optical monitoring of the system reveals strong variability of the He II lambda 4686 and Halpha line profiles. The He II lambda 4686 line displays a broad asymmetrical emission component which is found to be significantly stronger between phases 0.80 and 0.15 than around apastron. This suggests that part of the emission arises in the interaction region and most probably in the trailing arm of a shock cone wrapped around the secondary. Some absorption lines of the secondary's spectrum display equivalent width variations reminiscent of the so-called Struve-Sahade effect. The differences in behaviour between individual lines suggest that the temperature may not be the only relevant parameter that controls this effect. [less ▲]

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See detailA phase-resolved XMM-Newton campaign on the colliding-wind binary HD 152248
Sana, H.; Stevens, I. R.; Gosset, Eric ULg et al

in Monthly Notices of the Royal Astronomical Society (2004), 350(3), 809-828

We report the first results of an XMM-Newton monitoring campaign of the open cluster NGC 6231 in the Sco OB 1 association. This first paper focuses on the massive colliding-wind binary HD 152248, which is ... [more ▼]

We report the first results of an XMM-Newton monitoring campaign of the open cluster NGC 6231 in the Sco OB 1 association. This first paper focuses on the massive colliding-wind binary HD 152248, which is the brightest X-ray source of the cluster. The campaign, with a total duration of 180 ks, was split into six separate observations, following the orbital motion of HD 152248. The X-ray flux from this system presents a clear, asymmetric modulation with the phase and ranges from 0.73 to 1.18 x 10(-12) erg s(-1) cm(-2) in the 0.5-10.0 keV energy band. The maximum of the emission is reached slightly after apastron. The EPIC spectra are quite soft, and peak around 0.8-0.9 keV. We characterize their shape using several combinations Of MEKAL models and power-law spectra and we detect significant spectral variability in the 0.5-2.5 keV energy band. We also perform 2D hydrodynamical simulations using different sets of parameters that closely reproduce the physical and orbital configuration of the HD 152248 system at the time of the six XMM-Newton pointings. This allows a direct confrontation of the model predictions with the constraints deduced from the X-ray observations of the system. We show that the observed variation of the flux can be explained by a variation of the X-ray emission from the colliding-wind zone, diluted by the softer X-ray contribution of the two O-type stars of the system. Our simulations also reveal that the interaction region of HD 152248 should be highly unstable, giving rise to shells of dense gas that are separated by low-density regions. Finally, we perform a search for short-term variability in the light curves of the system and we show that trends are present within several of the 30-ks exposures of our campaign. Further, most of these trends are in good agreement with the orbital motion and provide a direct constraint on the first-order derivative of the flux. In the same context, we also search for long-range correlations in the X-ray data of the system, but we only marginally detect them in the high-energy tail of the signal. [less ▲]

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See detailPhase-resolved XMM-Newton observations of the massive WR+O binary WR 22
Gosset, Eric ULg; Nazé, Yaël ULg; Sana, H. et al

in Astronomy and Astrophysics (2009), 508

Aims. To better understand the phenomenon of colliding winds in massive binary stars, we study the X-ray lightcurve of a WR+O system of the Carina region, a system well known for the high mass of its ... [more ▼]

Aims. To better understand the phenomenon of colliding winds in massive binary stars, we study the X-ray lightcurve of a WR+O system of the Carina region, a system well known for the high mass of its primary.<BR /> Methods: Phase-resolved X-ray observations of the massive WR+O binary system WR 22 were performed with the XMM-Newton facility. We observed the object at seven different phases from near apastron to near periastron.<BR /> Results: The X-ray spectrum can be represented by a two-component, optically thin, thermal plasma model with a first one at a typical temperature of 0.6 keV and a second hotter one in the range 2.0-4.5 keV. The hot component is indicative of a colliding wind phenomenon, but its flux is remarkably constant with time despite the high eccentricity of the orbit. Although surprising at first, this actually does not contradict the results of the hydrodynamical simulations of the wind collision that we performed. When the system goes from apastron to periastron, the soft part of the X-ray flux is progressively lowered by an increasing intervening absorbing column. This behaviour can be interpreted in terms of an X-ray emitting plasma located near the O star, but not fully intrinsic to it, and accompanying the star when it dives into the wind of the WR component. A model is presented that interprets most of the observational constraints. This model suggests that the mass-loss rate of dot{M}[SUB]WR[/SUB] 1.6 à 10[SUP]-5[/SUP] {M}[SUB]ȯ[/SUB] yr[SUP]-1[/SUP] assumed for the WR could still be slightly too high, whereas it is already lower than other published values. From the comparison of the observed and the expected absorptions at phases near periastron, we deduce that the hard X-ray emitting collision zone should at least have a typical size of 50-60 R[SUB]ȯ[/SUB], but that the size for the soft X-ray emitting region could reach 244 R[SUB]ȯ[/SUB] if the assumed mass-loss rate is correct. We also present an upper limit to the X-ray luminosity of the WR component that further questions the existence of intrinsic X-ray emission from single WN stars.<BR /> Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). Research Associate FNRS (Belgium). Postdoctoral Researcher FNRS (Belgium). [less ▲]

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See detailPhase-separated microstructures in "all-acrylic" thermoplastic elastomers
Leclère, Philippe; Rasmont, A.; Brédas, Jean-Luc et al

in Macromolecular Symposia (2001), 167

Atomic Force Microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. Measuring simultaneously the amplitude and the phase of the oscillating ... [more ▼]

Atomic Force Microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. Measuring simultaneously the amplitude and the phase of the oscillating cantilever in tapping-mode operation provides the surface topography along with the cartography of microdomains with different mechanical properties. This in turn allows to characterize the organization of the various components at the surface in terms of well-defined morphologies (e.g., spheres, cylinders, or lamellae). Here this approach is applied to a series of symmetric triblock copolymers made of a central elastomeric segment (polyalkylacrylate) surrounded by two thermoplastic sequences (polymethylmethacrylate). The occurrence of microphase separation in these materials and the resulting microscopic morphology are essential factors for determining their potential applications as a new class of thermoplastic elastomers. This paper describes how the surface morphology can be controlled by the molecular structure of the copolymers (volume ratio between the sequences, molecular weight, length of the alkyl side group) and by the experimental conditions used for the preparation of the films. The molecular structure of the chains is fully determined by the synthesis of the copolymers via living anionic polymerization while the parameters that can be modified when preparing the samples are the nature of the solvent and the thermal annealing of the films. Finally, we report on a systematic comparison between images and approach-retract curve data. We show that this experimental comparison allows the origin of the contrast that produces the image to be straightforwardly evaluated. The method provides an unambiguous quantitative measurement of the contribution of the local mechanical response to the image. We show that most of the contrast in the height and phase images is due to variations in local mechanical properties and not in topography. [less ▲]

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See detailPhase-shifting real time interferometry that uses bismut silicon oxide crystals
Georges, Marc ULg; Lemaire, Philippe

in Applied Optics (1995), 34(32), 7497-7506

A bismuth silicon oxide crystal is used in the diffusion regime as a dynamic recording medium in a real-time holographic interferometer based on anisotropic self-diffraction. This device is connected with ... [more ▼]

A bismuth silicon oxide crystal is used in the diffusion regime as a dynamic recording medium in a real-time holographic interferometer based on anisotropic self-diffraction. This device is connected with an interferogram-analysis method that uses the phase-shifting technique for quantitative measurement of diffusive-reflecting object deformations. In addition to the usual error sources in phase shifting, the temporal interferogram erasure is studied and is found weakly perturbative for the measured phase. Itis shown that quantitative measurements are possible for low-intensity object beams (8 μW/cm2) and a large observed area. Apractical situation of defect monitoring in a composite structure is presented. [less ▲]

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See detailPhase-transition regularities in critical constants, fusion temperatures and enthalpies of chemically similar chainlike structures
Balaban, A. T.; Klein, D. J.; March, N. H. et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2005), 6(9), 1741-1745

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See detailPhaseolus lunatus L.
Baudoin, Jean-Pierre ULg

in Plant Resources of Tropical Africa (PROTA Foundation) (2006), 1

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See detailPhases of Polonium via Density Functional Theory
Verstraete, Matthieu ULg

in Physical Review Letters (2010), 104

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See detailPhD committe presentation - 3rd year
Serino, Gennaro ULg

Report (2014)

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