References of "1998"
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See detailEscourgeon et Orge d'hiver fourragère
Bodson, Bernard ULg; Herman, Jean-Luc; Monfort, Bruno et al

in Fumure et protection phytosanitaire des céréales: Informations avant les semis des céréales (1998, September 10)

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See detailCloches et carillons dans les Principautés de Liège et Stavelot-Malmedy: problèmes et voies de recherche
Marganne, Marie-Hélène ULg; Mélard, Marc

Conference given outside the academic context (1998)

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See detailLe traitement des infections artérielles. Apport de l’allogreffe
LAVIGNE, Jean-Paul ULg

Doctoral thesis (1998)

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See detailObservation of short and long timescale variability of the jovian UV aurora
Grodent, Denis ULg; Gérard, Jean-Claude ULg; Dols, V. et al

in Bulletin of the American Astronomical Society (1998, September 01)

Three sets of Hubble Space Telescope far-ultraviolet images of Jupiter's North pole aurora have been obtained with the Wide Field and Planetary Camera 2 in June 1996, May 1997 and August 1997. The ... [more ▼]

Three sets of Hubble Space Telescope far-ultraviolet images of Jupiter's North pole aurora have been obtained with the Wide Field and Planetary Camera 2 in June 1996, May 1997 and August 1997. The exposure time was limited to 160 seconds in order to reveal short timescale auroral features that are normally averaged during longer exposures and blurred by the rapid jovian rotation. The 3 sets of images show the aurora in a comparable (quiet) activity level, exhibiting long term persistent features such as : (i) a stable thin morning arc, (ii) a morning-afternoon emission dichotomy, (iii) a minimum of low latitude emission around CML=175 deg, (iv) bright localized afternoon structures. The equatorward boundary of the arc closely follows but is not coincident with the footprint of the 20 RJ magnetic field line given by the VIP4 model. These stable structures contrast with rapidly changing features like small size spots blasting in one single image, bright regions connecting trans-auroral structures, and the inner diffuse emission. The question of temporal variability and spatial extent of the auroral features is of major importance in understanding the origin and acceleration mechanisms of the auroral particles exciting the jovian UV aurora. In particular, short timescale processes can be related to field aligned currents generating acceleration structures and discrete aurora. [less ▲]

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See detailFUV spectroscopy of the H_2 emission in the Jovian aurora: model update and results
Gérard, Jean-Claude ULg; Dols, V.; Colignon, David ULg et al

in Bulletin of the American Astronomical Society (1998, September 01)

The Jovian aurora exhibits bright emissions mainly due the bright Lyman-alpha line and to radiation from excited singlet states to the ground electronic state extending from 800 to 1600 Angstroms. Above ... [more ▼]

The Jovian aurora exhibits bright emissions mainly due the bright Lyman-alpha line and to radiation from excited singlet states to the ground electronic state extending from 800 to 1600 Angstroms. Above 1200 Angstroms, the molecular spectrum is dominated by the Lyman (B-X) bands and continuum and the Werner (C-X) bands. These transitions have been observed with the Goddard High Resolution Spectrometer (GHRS) and the Space Telescope Imaging Spectrometer (STIS) at various spectral and spatial resolutions. To analyze these spectra, a model synthetic auroral spectrum has been constructed and applied to the analysis of the ro-vibrational temperature of H_2 and a search for non-H_2 emission features. It has been recently updated to include the latest singlet state excitation and cascading cross sections, self-absorption in optically thick lines and to account for the energy distribution of the secondary electrons which cause additional excitation. We illustrate these effects in a few study cases and apply the model to high resolution (0.5 Angstroms) GHRS spectra and low resolution STIS spectra of the entire H_2 spectrum at wavelengths longer than Lyman-alpha. We determine the methane column overlying the auroral emission peak and find that a better fit is obtained with additional absorption by acetylene. [less ▲]

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See detailHST-STIS Observations of Jupiter's Aurora
Clarke, J. T.; Ajello, J.; Ballester, G. E. et al

in Bulletin of the American Astronomical Society (1998, September 01)

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an ... [more ▼]

HST observations of the UV emissions from Jupiter's aurora have been obtained with the new Space Telescope Imaging Spectrograph (STIS) since July 1997. UV images of the aurora are now possible with an order of magnitude higher sensitivity than possible with earlier cameras, and improved angular resolution from shorter exposures. Images have been obtained at 4 epochs since Sept. 1997, and reveal several new features of the auroral emission pattern. These include i) faint auroral emissions extending roughly 60 deg. in the wake or plasma flow direction beyond Io's magnetic footprint, ii) systematic motions of the main auroral oval both toward the pole and toward the equator at different local times and longitudes, and iii) clear identification of an auroral emission feature with Ganymede's magnetic footprint, from the relative motion of the feature remaining underneath Ganymede in a time series of images. Preliminary interpretations of these features will be presented. Spectra have also been obtained of auroral emission features including the northern and southern main ovals, the diffuse emission poleward of the main oval, and the northern and southern Io footprints. These spectra will be presented with estimates of the overlying hydrocarbon columns, the energy of the exciting electrons, the rotational temperature of the emitting hydrogen, and the overlying column of atomic hydrogen. This work was supported by NASA under grants GO-6743.01-95A and GO-7308.01-96A to the University of Michigan. [less ▲]

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See detailJovian Auroral Lyalpha Self-Reversals: A Window on Jupiter's Auroral Electrojet?
Gladstone, G. R.; Waite, J H, Jr; Gérard, Jean-Claude ULg

in Bulletin of the American Astronomical Society (1998, September 01)

High-resolution GHRS profiles of Lyalpha lines emitted from Jupiter's auroral regions were presented by Prang{e} et al. (Astrophys. J., 484, L169--L173, 1997). Their data show asymmetric self-reversed ... [more ▼]

High-resolution GHRS profiles of Lyalpha lines emitted from Jupiter's auroral regions were presented by Prang{e} et al. (Astrophys. J., 484, L169--L173, 1997). Their data show asymmetric self-reversed line profiles, with the blue or red peak brighter depending on the target location in Jupiter's northern auroral region. The measured asymmetries are equivalent to Doppler velocities towards and away from the observer of several km/s. As suggested by Sommeria et al. (Icarus, 119, 2--24, 1995), electrojet velocities of ~ 10--20 km/s may be present at Jupiter. Here we investigate the possibility that the observed wavelength shifts of the auroral Lyalpha line are a result of multiple scattering by H atoms carried along in Jupiter's auroral electrojet. If this explanation is found to be viable, then HST/STIS mapping of the velocity shifts in the Lyalpha line may represent (as with ground-based high-resolution observations of jovian auroral H_3(+) emission lines) a means for determining the dynamics of Jupiter's upper atmosphere and ionosphere. [less ▲]

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See detailThe Jovian Aurora: Implications of Multiwavelength Auroral Spectra for Auroral Particle Identity and Auroral Microphysics
Waite, J. H.; Gladstone, G. R.; Bolton, S. J. et al

in Bulletin of the American Astronomical Society (1998, September 01)

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on Jupiter's upper ... [more ▼]

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on Jupiter's upper atmosphere. Both energetic heavy ions and electrons energized in the outer magnetosphere contribute to the auroral excitation, as indicated by the combination of x-ray and ultraviolet observations. Imaging with the HST in the ultraviolet and with the IRTF at infrared wavelengths reveals several distinct regions of interaction: 1) a dusk sector where turbulent auroral patterns extend well into the polar cap; 2) a morning sector generally characterized by a single spatially confined auroral arc originating in the outer magnetosphere of Jupiter; 3) diffuse emissions associated with the Io plasma torus; and 4) a distinct region associated with the Io Flux Tube footprint. Ultraviolet spectroscopy has provided important information about the thermal structure of the upper atmosphere and altitude distribution of the auroral particle energy deposition, while Lyman alpha line profiles offer clues to the nature of thermospheric dynamical effects. Galileo observations at visible wavelengths on the nightside have provided a new view of the jovian aurora with unprecedented spatial information. Infrared observations have added much to the understanding of thermal structure and morphology and may hold the key to understanding the role of Joule heating. Radio observations imply that energetic particle precipitation extends to low latitudes, a result that has been corroborated at x-ray wavelengths. Multispectral observations of jovian auroral emissions will be discussed within a theoretical/modeling framework that serves to provide some insight into magnetosphere-ionosphere coupling and its effect on the upper atmosphere. Particular emphasis will be placed on the use of auroral spectra to identify incident energetic particles and their energy spectra as a means of elucidating the microphysics of auroral processes. [less ▲]

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See detailFirst results on the evaluation of Haser scale lengths in comet Hale-Bopp (C/1995 O1) at R >= 3 AU
Helbert, J.; Rauer, H.; Arpigny, Claude ULg et al

in Bulletin of the American Astronomical Society (1998, September 01)

Due to its exceptional brightness, comet Hale-Bopp offered the possibility for unprecedented long-term monitoring. Medium resolution long-slit spectroscopic data and images were obtained using the Danish ... [more ▼]

Due to its exceptional brightness, comet Hale-Bopp offered the possibility for unprecedented long-term monitoring. Medium resolution long-slit spectroscopic data and images were obtained using the Danish Faint Object Spectrograph (DFOSC) at the 1.54m Danish telescope and the Boller and Chivens spectrograph at the 1.52m ESO telescope, La Silla, Chile. Pre-perihelion, comet Hale-Bopp was monitored from 4.6 AU to 2.9 AU and post-perihelion, the monitoring yields data from 3 AU up to a heliocentric distance of 5 AU. Production rates are often derived by using a simple Haser model to approximate the coma density distribution. This requires knowledge of the destruction scale lengths of the observed daughter species and its parents. As the brightness of most comets diminishes quickly with heliocentric distance, scale lengths have been determined only in comets around 1 AU. Due to the lack of data for large heliocentric distances, production rates in distant comets can only be derived by extrapolating these scale lengths. In this preliminary analysis of our data we evaluate the scale-lengths of CN, C_3 C_2, and NH_2 at heliocentric distances greater than 3 AU post-perihelion. The differences of production rates derived by using these directly determined and the extrapolated scale lengths are discussed. [less ▲]

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See detailHubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission
Clarke, John T; Ben Jaffel, Lotfi; Gérard, Jean-Claude ULg

in Journal of Geophysical Research (1998), 103

Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 (WFPC 2) images of Jupiter's aurora have been obtained close in time with Galileo ultraviolet spectrometer (UVS) spectra and in situ particles ... [more ▼]

Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 (WFPC 2) images of Jupiter's aurora have been obtained close in time with Galileo ultraviolet spectrometer (UVS) spectra and in situ particles, fields, and plasma wave measurements between June 1996 and July 1997, overlapping Galileo orbits G1, G2, G7, G8, and C9. This paper presents HST images of Jupiter's aurora as a first step toward a comparative analysis of the auroral images with the in situ Galileo data. The WFPC 2 images appear similar to earlier auroral images, with the main ovals at similar locations to those observed over the preceding 2 years, and rapidly variable emissions poleward of the main ovals. Further examples have been observed of the equatorward surge of the auroral oval over 140-180° longitude as this region moves from local morning to afternoon. Comparison of the WFPC 2 reference auroral ovals north and south with the VIP4 planetary magnetic field model suggests that the main ovals map along magnetic field lines exceeding 15R[SUB]J[/SUB], and that the Io footprint locations have lead angles of 0-10° from the instantaneous magnetic projection. There was an apparent dawn auroral storm on June 23, 1996, and projections of the three dawn storms imaged with HST to date demonstrate that these appear consistently along the WFPC 2 reference oval. Auroral emissions have been consistently observed from Io's magnetic footprints on Jupiter. Possible systematic variations in brightness are explored, within factor of 6 variations in brightness with time. Images are also presented marked with expected locations of any auroral footprints associated with the satellites Europa and Ganymede, with localized emissions observed at some times but not at other times. [less ▲]

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See detailSimultaneous Determination of Pirlindole Enantiomers and Dehydropirlindole by Chiral Liquid Chromatography
Ceccato, Attilio ULg; Hubert, Philippe ULg; De Tullio, Pascal ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (1998), 17(6-7), 1071-9

Liquid chromatography was employed for the determination of pirlindole enantiomers and its oxidation product dehydropirlindole (DHP). The direct separation of pirlindole enantiomers and DHP was achieved ... [more ▼]

Liquid chromatography was employed for the determination of pirlindole enantiomers and its oxidation product dehydropirlindole (DHP). The direct separation of pirlindole enantiomers and DHP was achieved on a cellulose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase (Chiralcel OD-R). Acetonitrile was used as the organic modifier and sodium perchlorate was used as an ionic additive in the mobile phase. The influence of acetonitrile and sodium perchlorate concentrations on enantioselectivity and achiral selectivity towards DHP was investigated in order to find suitable conditions for the determination of low amounts of each analyte. The mobile phase selected consisted of a mixture of acetonitrile and phosphate buffer (pH 5.0) containing sodium perchlorate (0.05 M) (35:65, v/v) and the UV detector was set at 220 nm. The method developed was validated and was found to be linear in the 0.1-5 microg ml(-1) range (r2 = 0.999 for the three compounds). Repeatability and the intermediate precision for the three analytes at a concentration of 0.1 microg ml(-1) were about 3 and 4%, respectively. This concentration corresponds to the quantification of 0.1% for the minor enantiomer. Actual determinations of enantiomeric purity for single enantiomers of pirlindole were performed. [less ▲]

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See detailEffects of Brain Testosterone Implants on Appetitive and Consummatory Components of Male Sexual Behavior in Japanese Quail
Riters, L. V.; Absil, Philippe ULg; Balthazart, Jacques ULg

in Brain Research Bulletin (1998), 47(1), 69-79

Aromatization of testosterone (T) into an estrogen is necessary for the activation of consummatory and appetitive sexual behavior in male Japanese quail. T action within the medial preoptic nucleus (POM ... [more ▼]

Aromatization of testosterone (T) into an estrogen is necessary for the activation of consummatory and appetitive sexual behavior in male Japanese quail. T action within the medial preoptic nucleus (POM) is necessary and sufficient to activate consummatory behavior, and some evidence suggests that POM might be involved in the control of appetitive behavior, but other brain regions, such as the bed nucleus of the stria terminalis (BST), an area that contains a dense population of aromatase-immunoreactive neurons, are also likely to be involved. This study was performed to assess the effects of stereotaxic T implants targeting either the POM or the BST on the activation of both components of sexual behavior in castrated male quail. Appetitive sexual behavior was measured by an acquired social proximity response in which a male will approach a window providing visual access to a female after the window has been repeatedly paired with physical access to a female and the possibility to freely interact with her. Rhythmic cloacal sphincter movements that are produced by the male when given visual access to a female were used as another measure of appetitive sexual behavior that does not appear to depend on sexual learning. The experiments confirmed that copulation is necessary for males to develop the social proximity response that is used to measure the appetitive sexual behavior. T implants in the POM activated both components of sexual behavior, suggesting that these components cannot be completely dissociated. In contrast, T implants located within the BST did not affect either component, but because implants in the BST did not activate copulatory behavior, these results do not preclude a role for BST in the expression of a previously acquired appetitive sexual behavior. [less ▲]

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See detailSpectrophotometric Monitoring of Comet C/1995 O1 (Hale-Bopp): Pre- and Post-Perihelion
Rauer, H.; Helbert, J.; Arpigny, Claude ULg et al

in Bulletin of the American Astronomical Society (1998, September 01)

Spectrophotometric observations of comet C/1995 O1 (Hale-Bopp) were performed at the European Southern Observatory (ESO), Chile. From April to September 1996 its gaseous activity was monitored over a ... [more ▼]

Spectrophotometric observations of comet C/1995 O1 (Hale-Bopp) were performed at the European Southern Observatory (ESO), Chile. From April to September 1996 its gaseous activity was monitored over a heliocentric distance range from 4.6 AU to 2.9 AU. The monitoring is continued on Hale-Bopp's outbound path since September 1997 and covers up to now 3 AU to 5 AU heliocentric distance. Medium resolution spectra in the optical wavelength range from about 350 nm to 700 nm were taken at the 1.54m Danish and the 1.52m ESO telescope. Emission bands of the CN, C_3, C_2 and NH_2 radicals can be followed over the comet's orbit. We will present a first analysis of the post-perihelion activity evolution and compare to the pre-perihelion path. Currently, at 4.7 AU on the outbound path, we still see emission of CN, C_3, C_2 and NH_2. The production rate of CN showed a sudden increase around this heliocentric distance pre-perihelion (Rauer et al., Science 275, 1909). The post-perihelion activity evolution of CN and the other observed radicals in this distance range will be evaluated. [less ▲]

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See detailEffective Iterative Solvers for Highly Non-Linear & Large Deformation Pressure Dependent Problems
Boman, Romain ULg; Colantonio, Laurent; Ponthot, Jean-Philippe ULg

in Van Keer, R.; Verhegghe, B.; Hogge, M. (Eds.) et al Proceedings of ACOMEN'98, Advanced Computational Methods in Engineering, part 2: Contributed papers (1998, September)

In this paper, we present a stress update scheme for non-deviatoric elastoviscoplastic models, which can be considered as an extension of the radial return method for classical plasticity. We use the ... [more ▼]

In this paper, we present a stress update scheme for non-deviatoric elastoviscoplastic models, which can be considered as an extension of the radial return method for classical plasticity. We use the unconditionally stable backward Euler scheme to obtain the viscoplastic solution at each increment. To solve the large sparse non symmetric iteration matrix, we use the GMRES method. This fast iterative solver, in conjunction with an appropriate preconditioner, can save a lot a memory and CPU time when 3D problem are considered. A comparison between direct and iterative solvers will be discussed on two applications of cold compaction of powders. [less ▲]

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See detailNovel 2-oxo-2H-benzopyran derivatives as inhibitors of human leukocyte elastase
Pochet, L.; Doucet, C.; Pirotte, Bernard ULg et al

Poster (1998, September)

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