Showing papers by "University of Mons published in 1990"
TL;DR: It is concluded that the myelin lipids do not contribute to the signal, and Transverse magnetization decay data can be fitted with a triple exponential function, giving characteristic results for each tissue type, and are insensitive to variations of the pulse spacing interval.
Abstract: The dependence of 1/T1 on the magnetic field strength (the relaxation dispersion) has been measured at 37 degrees C on autopsy samples of human brain gray and white matter at field strengths corresponding to proton Larmor frequencies between 10 kHz and 50 MHz (0.0002-1.2 T). Additional measurements of 1/T1 and 1/T2 have been performed at 200 MHz (4.7 T) and 20 MHz (0.47 T), respectively. Absolute signal amplitudes are found to be proportional to the sample water content, not to the "proton density," and it is concluded that the myelin lipids do not contribute to the signal. Transverse magnetization decay data can be fitted with a triple exponential function, giving characteristic results for each tissue type, and are insensitive to variations of the pulse spacing interval. The longitudinal relaxation dispersion curves show characteristic shapes for each tissue type. The most striking difference is a large dispersion for white matter at very high fields. As a consequence, the relative difference in 1/T1 between gray and white matter shows a marked maximum around 10 MHz. Possible implications for MRI are discussed. A weighted least-squares fit of the dispersions has been performed using a four-parameter function of the form 1/T1 = 1/T1,w + D + A/(1 + (f/fc)beta'). The quality of the fit is superior to that of other functions proposed previously. The results of these fits are used to predict image contrast between gray and white matter at different field strengths.
165 citations
University of Turin1, Uppsala University2, University of Warsaw3, CERN4, University of Liverpool5, RWTH Aachen University6, Lancaster University7, University of Paris8, University of Kiel9, Laboratoire d'Annecy-le-Vieux de physique des particules10, Rutherford Appleton Laboratory11, University of Sheffield12, Max Planck Society13, University of Freiburg14, University of Hamburg15, University of Oxford16, University of Mons17
TL;DR: In this article, small angle scattering of 280 GeV positive muons by deuterium, carbon and calcium has been measured at scattering angles down to 2 mrad, where F 2 (Ca) and F 2(D) are not significantly different.
112 citations
TL;DR: The model of Woessner was applied to the water molecules tightly bound into the macromolecules, which resulted in a dynamical description of this water fraction, compatible with the two-sites model of Ramachandran based on x-ray diffraction and with the extensive studies of Berendsen.
103 citations
TL;DR: Deconvolution showed that the exponentials decaying most quickly are most orientation dependent, and each decaying mode was assigned to a fraction of protons localized in the macromolecular structure and characterized by particular dynamics.
64 citations
TL;DR: In this paper, the DELPHI detector at the e+e− storage ring LEP at the center of mass energies around 91.5 GeV was used to measure the production rates for 2-, 3-, 4, and 5-jet hadronic final states.
62 citations
TL;DR: In this paper, the theoretical aspect of thermal convection in two superimposed immiscible (or partially miscible) fluid layers in a rectangular cavity with differentially heated end walls is considered.
Abstract: This paper considers mainly the theoretical aspect of thermal convection in two superposed immiscible (or partially miscible) fluid layers in a rectangular cavity with differentially heated end walls. We develop a model valid for layers whose lateral extent is much larger than depth, deriving the horizontal velocity profile in each layer as a function of the various parameters such as expansion coefficients, viscosities, depth of each layer, and the interfacial tension gradient along the interface. Results are discussed, taking into account the results of experiments that we presented recently [1].
49 citations
TL;DR: In this paper, the authors search for the production of sleptons and gauginos in the two-prong decays of Z0, but no candidate remains after straightforward selections.
42 citations
TL;DR: A solid-on-solid--model description of the dynamics of wetting, using Langevin equations, is proposed and the dynamical contact angle, the shape of the profile near the substrate, and, for dry spreading, the occurrence, speed, and possible layering of a precursor film are obtained.
Abstract: We propose a solid-on-solid--model description of the dynamics of wetting, using Langevin equations. The Gaussian version, appropriate to partial wetting, is solved exactly. The general version is solved using local equilibrium and scaling arguments. We obtain the dynamical contact angle, the shape of the profile near the substrate, and, for dry spreading, the occurrence, speed, and possible layering of a precursor film.
41 citations
TL;DR: In this paper, the authors re-analysed the recently observed nuclear rainbow data for the 16O+16O system and demonstrated that there are three optical potentials which fit the data equally well.
38 citations
TL;DR: In this paper, the authors measured the cross section ratios R l = σ l (e + e − →l + l − ) σ h ( e + e−→l+l−) for l=e, μ and τ using data taken from a scan around the Z0.12.
28 citations
TL;DR: In this article, a thermodynamic model of size-dependent melting of small particles is proposed by assuming that the mean phonon frequency of the particles varies linearly with the number of defects and surface sites.
TL;DR: In this paper, a search was made for pairs of scalar quarks (squarks) produced in e+e− annihilations at LEP and decaying into a standard quark and a neutral, non-interacting, stable, massive particle (the lightest supersymmetric particle, LSP).
TL;DR: In this article, a real-time analysis of the flash-vacuum pyrolysis products of 1-acetylbenzotriazole (1) and 1-benzoylbenzotsamide (2) was performed by tandem mass Spectrometry.
Abstract: A real-time analysis of the flash-vacuum pyrolysis products of 1-acetylbenzotriazole (1) and 1-benzoylbenzotriazole (2) was performed by tandem mass Spectrometry. In the temperature range 500-600 °C, these compounds lose nitrogen, yielding N-acetyl- and N-benzoylcyclopenta- 2,4-dienylidenemethaneimines (10 and 17, respectively). At higher pyrolysis temperatures, 1 gives 2-methylbenzoxazole, cyanocyclopentadiene, methylcyanocyclopentadiene(s), benzonitrile and ketene, which were identified by collision-activated dissociation mass Spectrometry. Low-temperature infrared experiments confirmed the pyrolytic transformation 1(2) 10(17) at mediated temperatures.
TL;DR: In this paper, the shape of the contact angle and the speed of the precursor film were derived for SOS type models, near a wall which favors spreading and showed that long-range potentials lead to a layered structure of a precursor film.
Abstract: We study dynamical contact angles and precursor films using Langevin dynamics for SOS type models, near a wall which favors spreading. We first solve exactly the Gaussian model and discuss various asymptotic regimes. This is only appropriate to partial wetting. We then consider more general models. Using local equilibrium and scaling arguments, we derive the shape of the dynamical profile and the speed of the precursor film which exists when the spreading coefficient is strictly positive. Long-range potentials lead to a layered structure of the precursor film. We also consider the case of a meniscus in a capillary.
TL;DR: The nucleotide (nt) sequences of the genes encoding argininosuccinate synthetase from Escherichia coli K-12 (argG) and Saccharomyces cerevisiae (ARG1) were determined and three regions appear to contain possible Walker-type nt-binding sites and are therefore candidates for ATP- binding sites.
TL;DR: The diversity of the stereom growth processes observed in the present work may be reduced to the combination of one to three elementary events, viz. the development of long linear processes, of short unbranched processes and of short branched process.
Abstract: The very first mineral deposits appearing in regenerating fractured adambulacral spines of Asterias rubens are minute polyhedrons that cover the surface of fractured trabeculae. Polyhedrons fuse together forming a fold from which a microspine differentiates. Microspines develop into long linear trabeculae which send out lateral processes at regular length intervals. Lateral processes from adjacent trabeculae fuse together, bridging the trabeculae and giving the regenerate the typical meshwork structure of stereom. Most of the regenerate is built up according to this growth pattern which ensures its longitudinal growth. Simultaneously, the initial fascicular stereom of the stub sends out short radial processes which branch into upward and downward directed subprocesses. The latter fuse with their equivalents located above or below, building up longitudinal rows of stereom meshes. These rows then bridge together by additional branched or unbranched lateral processes, so forming a new stereom layer which progressively covers the whole stub. Up to three new layers of stereom are formed in this way at the stub periphery. These become continuous with the stereom layers of the regenerate by fusion of reciprocal subprocesses, so ensuring the continuity between the stub and the regenerate. In both structures the first stage of mineralization results in an open stereom. Stereom thickening occurs in a second stage of mineralization (that is chronologically separated from the formation of the open stereom) and results in the differentiation of the original stereom fabrics (i.e. fascicular stereom). Regeneration of removed spines starts with the formation of a new spine base made of labyrinthic stereom. The development of the latter mostly relies on short branched and unbranched processes which fuse with each other or with predifferentiated meshes. After completion of its base, the regenerating spine lengthens and thickens similarly to the regenerating fractured spines. The diversity of the stereom growth processes observed in the present work may be reduced to the combination of one to three elementary events, viz. the development of long linear processes, of short unbranched processes and of short branched processes. A survey of the literature allows the suggestion that the implementation of these elementary events is sufficient to describe most types of stereom morphogenesis.
TL;DR: In this paper, the relativistic Hartree-Fock method combined with an optimization of Slater parameters (radial energy integrals) based on the observed energy levels when they are available, has been used for the calcutions.
Abstract: Theoretical energy levels are reported for the n = 4, Δn = 0 transitions of the ions Br V-In XIX along the gallium isoelectronic sequence. The relativistic Hartree-Fock method, combined with an optimization of Slater parameters (radial energy integrals) based on the observed energy levels when they are available, has been used for the calcutions. Oscillator strengths of the 4 s 4 p 2 -4 p 3 and 4s 2 4d-4s 2 4⨍ electric dipole transitions have been calculated on the basis of the optimized Slater parameters.
TL;DR: In this paper, the electronic structure of poly(ether-ether-ketone) (PEEK) was investigated by combining X-ray and ultraviolet photoelectron spectroscopy data with the results of theoretical calculations.
TL;DR: Using a combination of flash-vacuum pyrolysis and tandem mass spectrometry, it was shown that benzonitrile N -sulfide, 1, is a stable molecule in the diluted gas phase.
TL;DR: Since EB can be destroyed by heating at temperatures above 262°C, the contaminated charcoal filters can be easily incinerated thus providing a simple and cheap decontamination procedure which can be extended to other suspected mutagens such as propidium iodide which is commonly used in flow cytometric DNA analysis.
Abstract: An activated charcoal filter has been used to remove ethidium bromide (EB) in water, various buffers, CsCl solutions and ethanol. In all cases studied, ethidium bromide was undetectable in the eluted liquid (contamination less than 0,5 μg/ml in a fluorescence detection assay performed in the presence of 10 μg/ml HeLa cell DNA). Since EB can be destroyed by heating at temperatures above 262°C, the contaminated charcoal filters can be easily incinerated thus providing a simple and cheap decontamination procedure which can be extended to other suspected mutagens such as propidium iodide (PI) which is commonly used in flow cytometric DNA analysis.
TL;DR: In this paper, the authors analyzed monochromadzed Al-K α XPS spectra from iso-and syndiotacdc polystyrenes with the help of theoretical band structures and densities of states produced from a valence effective Hamiltonian (VEH) computation scheme.
TL;DR: Faster pH recovery is explained by a preservation of Na+/K+ATPase due to the influence of amiodarone on membrane lipid dynamics, whereas for control hearts, HR, PCr, and pH recovered after 42 min and LVP did not reach its control values at the end of reperfusion time.
Abstract: Effects of amiodarone injected intravenously (i.v.) at two doses (10 and 20 mg/kg) on perfused isovolumic rat hearts were assessed by P-31 nuclear magnetic resonance (NMR). P-31 NMR is used to measure intracellular myocardial pH, phosphocreatine (PCr), and ATP contents time evolutions. Myocardial mechanical function is estimated by heart rate (HR), left ventricular developed pressure (LVP), and coronary flow (CF). In experimental procedure A (2-h retrograde perfusion), drug injection induced a dose-dependent bradycardia (10-20%) and a slight decrease in LVP but did not affect CF, pH, PCr, or ATP contents. Experimental procedure B consisted of 30-min stabilization, 18-min ischemia, and 72-min reperfusion. During ischemia, amiodarone did not preserve ATP and PCr pools and did not alleviate acidosis. ATP decreased to 30% of its control values, whereas the PCr peak was hardly detectable after 12 min of ischemia. After 24 min of reflow, HR, PCr, and pH of treated hearts recovered. LVP recovered after 36 min, whereas for control hearts, HR, PCr, and pH recovered after 42 min and LVP did not reach its control values at the end of reperfusion time. Faster pH recovery is explained by a preservation of Na+/K+ ATPase due to the influence of amiodarone on membrane lipid dynamics.
TL;DR: In this article, it was shown that oxidation proceeds rapidly at some critical temperature, independent of P over some range of P, in the cases of Cd, In, Sn, and Zn.
Abstract: Thin films of Cd, In, Sn, and Zn are deposited onto glass and irradiated in air by means of a cw-Ar+ laser beam. The films are oxidized. The variations of the diameter of the oxidized zones are measured as a function of time and laser beam power, P. The temperature is measured by an interferometric method. It is shown that oxidation proceeds rapidly at some critical temperature, independent of P over some range of P, in the cases of Cd, In, and Zn. These critical temperatures correspond to the melting temperatures of Cd and In. No relation to any specific temperature of the Zn-O phase diagram is found. Feedback effects are also discussed.
TL;DR: In this paper, numerical simulation of temperature of thin film-substrate systems is performed to understand the influence of the nature of the substrate and of the thickness of the thin film.
TL;DR: In this paper, the theoretical electronic properties of conjugated regular copolymers, poly(1,4-phenylene-2′,5′-thienylene) (PT 2−5) and poly( 1,4phenylene -2′-6′-pyridinediyl) (PP 2−6), were determined using the valence effective Hamiltonian (VEH) method.
TL;DR: In the single phase region of a nearest neighbor Ising ferromagnet with zero external field, the block magnetization and energy within the infinite-volume system are, asymptotically for large block size, independent Gaussian variables when the dimensiond exceeds four as discussed by the authors.
Abstract: In the single-phase region (including the critical point) of a nearest-neighbor Ising ferromagnet with zero external field, the block magnetization and energy within the infinite-volume system are, asymptotically for large block size, independent Gaussian variables when the dimensiond exceeds four. For other models, including ones with long-range interactions, a sufficient condition for such triviality of the scaling limit is finiteness of the “bubble quantity”.
TL;DR: The relativistic Fokker-Planck equation for a light test-particle in a plasma of infinitely heavy ions (Lorentz gas) was derived in this paper.
Abstract: We derive the relativistic Fokker-Planck equation for a light test-particlein a plasma of infinitely heavy ions (Lorentz gas). A partial H-theorem results and the solution to this equation may be explicitly computed.
01 Jan 1990
TL;DR: The numerical method used in this paper is the ADI finite differences method on a regular rectangular grid and the results for requested cases with a free upper surface are in agreement with those from other contributors.
Abstract: The numerical method used in this work is the ADI finite differences method on a regular rectangular grid. Results for requested cases with a free upper surface are in agreement with those from other contributors. The additional contribution concerns the thermocapillary effect since this effect cannot be neglected in experiments, like in molten gallium. The influence of thermocapillarity on the onset of oscillatory convection and the flow patterns of supercritical oscillatory states are discussed.
01 Jan 1990
TL;DR: In this paper, the electronic structure of poly-3-hexylthiophene is studied in the solid state with photoelectron spectroscopy, as the polymer is gradually doped from NOPF6.
Abstract: The electronic structure of poly-3-hexylthiophene is studied in the solid state with photoelectron spectroscopy, as the polymer is gradually doped from NOPF6. The evolution of the core level binding energies is related to the modification of the electron density on the conjugated backbone, due to the creation of polaron and bipolaron defects. Upon doping, valence spectra show a shift in the Fermi level of the system, and at saturation doping a finite density of states is observed at the Fermi level. In the case of poly-para-phenylene vinylene, the experimental density of states of the neutral polymer is related to the results of Valence Effecttive Hamiltonian calculations. Comparison with gas phase data on styrene leads to an estimation of the polarization energy.