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See detailIl latino dell'Alcestis Barcinonensis
Macedo, Gabriel ULg

Conference (2012, September 06)

This paper presents a linguistic description of the Barcelona Alcestis, an anonymous Latin poem contained in a fourth century papyrus codex. Traces of Vulgar Latin are identified in the orthography, which ... [more ▼]

This paper presents a linguistic description of the Barcelona Alcestis, an anonymous Latin poem contained in a fourth century papyrus codex. Traces of Vulgar Latin are identified in the orthography, which reveals the language as it was heard, understood and spoken by the copyist, whereas the syntactic features of the text can inform us about the language used by the author in the time of the composition. [less ▲]

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See detailIl latino dell'Alcestis di Barcellona
Macedo, Gabriel ULg

in Molinelli, Piera; Cuzzolin, Pierluigi; Fedriani, Chiara (Eds.) Latin Vulgaire Latin Tardif X. Actes du Xe Colloque international sur le latin vulgaire et tardif (2014)

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See detail"Latinum est : non legitur" Lire le latin et traduire du latin en grec à Byzance
Rochette, Bruno ULg

Scientific conference (2011, April)

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See detail"Latinum est : non legitur". Lire le latin et traduire le latin en grec en Orient
Rochette, Bruno ULg

in Scrivere e leggere nell'Alto Medioevo (2012, May)

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See detailLatitudinal - local time distribution of the O2 and OH infrared nightglows and O density in the Venus lower thermosphere
Soret, Lauriane ULg; Gérard, Jean-Claude ULg; Saglam, Adem et al

Conference (2009, September)

Atomic oxygen has been measured in situ only above 145 km on both the day and the night sides of Venus. Limb observations obtained with the Venus Infrared Thermal Imaging Spectrometer (VIRTIS) on board ... [more ▼]

Atomic oxygen has been measured in situ only above 145 km on both the day and the night sides of Venus. Limb observations obtained with the Venus Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express show that the O2 infrared nightglow peaks at ~97 km [1, 2], with a mean intensity value of about 1 MR. Yet, the distribution is largely inhomogeneous, with an enhanced region of ~3 MR statistically located near the midnight meridian at low latitude [3]. The oxygen density can be mapped using the O2 airglow and CO2 density vertical distributions [4]. The O2 vol-ume emission rates are obtained with an Abel inversion of the O2 limb profiles using CO2 vertical distributions taken from the Venus International Reference Atmosphere (VIRA) model. The results show that the O density peak varies in altitude with a mean value of 105 km. It ranges from 1.0x1010 to 14.5x1011 cm-3, with a mean value of 2.2x1011 cm-3. The zonally averaged peak altitude appears to be constant while its amplitude decreases with latitude. Another approach uses the O2 volume emission rates obtained with an Abel inversion of the O2 limb profiles. In-deed, it is then possible to vertically integrate these profiles to simulate nadir observations. The resulting map gives values between 0 and 2.8 MR (with a mean value of 0.6 MR) in the north hemisphere. A statistical map created with actual nadir observations shows intensities ranging from 0 to 2.1 MR, with a mean of 0.5 MR in the south hemisphere. A combination of the two types of observations could cover Venus entire nightside. Statistical mapping of the OH Meinel emission has also been performed using limb profiles. A strong correlation with the O2 emission is revealed. The average altitude of the emission peak is ~95.3 km for the OH(1-0) band and the average intensity is 0.4 MR [5]. [less ▲]

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See detailLatitudinal and local time distribution of the O2 infrared nightglow and O density in the lower thermosphere
Soret, Lauriane ULg; Gérard, Jean-Claude ULg; Saglam, Adem et al

Poster (2009, May)

Atomic oxygen is the major component in the Earth’s upper thermosphere. The O density reaches a maximum of about 3x1010 cm-3 near 100 km. The 1.27 µm emission of the IR Atmospheric bands generated by ... [more ▼]

Atomic oxygen is the major component in the Earth’s upper thermosphere. The O density reaches a maximum of about 3x1010 cm-3 near 100 km. The 1.27 µm emission of the IR Atmospheric bands generated by recombination of O atoms has been observed in the nightglow. On the night side, the O2 airglow peaks at ~95 km with a value of ~10 MR. <br />Atomic oxygen is present in the Martian atmos-phere but that the intensities values are below the cur-rent instrument detectability threshold. The Mars at-mosphere oxygen density is highly variable, depending on the altitude, temperature, latitude and longitude. <br />On Venus, atomic oxygen has been measured in situ only above 145 km on both the day and the night sides. Limb observations obtained with the Venus In-frared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express show that the O2 infrared nightglow peaks at ~97 km, with a mean intensity val-ue of about 1,3 MR [1, 2]. Yet, the distribution is largely inhomogeneous, with an enhanced region of ~3 MR statistically located near the midnight meridian at low latitude [3]. The oxygen density can be mapped using the O2 airglow and CO2 density vertical distribu-tions [4]. The O2 volume emission rates are obtained with an Abel inversion of the O2 limb profiles and CO2 vertical distributions are taken from the Venus International Reference Atmosphere (VIRA) model. The results show that the O density peak is located between 93 and 105 km (with a mean value of 104 km) and ranges from 2.8x1010 to 8.5x1011 cm-3 (with a mean value of 2.2x1011 cm-3). No correlations between the peak altitude and the latitude or the peak altitude and the local time are observed. However, the O density decreases and its variability increases while moving away from the antisolar point. [less ▲]

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See detailThe latitudinal gradient of nitric oxide in the thermosphere
Cravens, T. E.; Gérard, Jean-Claude ULg; Stewart, A. I. et al

in Journal of Geophysical Research (1979), 84

Theoretical calculations of nitric oxide altitude profiles are made at five different latitudes by using neutral temperatures and composition primarily from the MSIS (mass spectrometer and incoherent ... [more ▼]

Theoretical calculations of nitric oxide altitude profiles are made at five different latitudes by using neutral temperatures and composition primarily from the MSIS (mass spectrometer and incoherent scatter) model. The nitric oxide calculated for an altitude of 105 km remains nearly constant with increasing latitude. Observations made by the ultraviolet nitric oxide instrument on the Atmosphere Explorer C satellite show that at low magnetic activity (Ap value of approximately 4), the NO density at 105 km agrees with the theory; however, at moderate levels of activity it increases with latitude. This discrepancy between the theoretical and observed latitudinal gradients of nitric oxide suggests the transport of NO from a high latitude source to lower latitudes. At 200 km the theoretical and observed latitudinal gradients are in reasonable agreement, an indication that the knowledge of the local composition and temperature is sufficient to model nitric oxide at this altitude. [less ▲]

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See detailThe latitudinal gradient of the NO peak density
Fesen, C. G.; Rusch, D. W.; Gérard, Jean-Claude ULg

in Journal of Geophysical Research (1990), 95

Results are presented from SME observations of the latitudinal gradients of peak NO densities at about 110-km altitude during the solstice and equinox periods from 1982 through 1985. It is shown that the ... [more ▼]

Results are presented from SME observations of the latitudinal gradients of peak NO densities at about 110-km altitude during the solstice and equinox periods from 1982 through 1985. It is shown that the response of the peak NO densities to the declining level of solar activity varies with latitude, with the polar regions exhibiting low sensitivity and the low-latitude regions responding strongly. The SME data also revealed marked asymmetries in the latitudinal structure of the two hemispheres for each season and considerable day-to-day variations in the NO densities. The solar cycle minimum data for June were simulated using a two-dimensional model; results of sensitivity studies performed with varied quenching rate and eddy diffusion coefficient are presented. [less ▲]

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See detailLatitudinal patterns of magnitude and interannual variability in net ecosystem exchange regulated by biological and environmental variables
Yuan, Wenping; Luo, Yiqi; Richardson, Andrew D et al

in Global Change Biology (2009), 15(12), 2905-2920

Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the ... [more ▼]

Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the sink are not well known. In this study, we examined latitudinal patterns of interannual variability (IAV) in net ecosystem exchange (NEE) of CO2 based on 163 site-years of eddy covariance data, from 39 northern-hemisphere research sites located at latitudes ranging from similar to 29 degrees N to similar to 64 degrees N. We computed the standard deviation of annual NEE integrals at individual sites to represent absolute interannual variability (AIAV), and the corresponding coefficient of variation as a measure of relative interannual variability (RIAV). Our results showed decreased trends of annual NEE with increasing latitude for both deciduous broadleaf forests and evergreen needleleaf forests. Gross primary production (GPP) explained a significant proportion of the spatial variation of NEE across evergreen needleleaf forests, whereas, across deciduous broadleaf forests, it is ecosystem respiration (Re). In addition, AIAV in GPP and Re increased significantly with latitude in deciduous broadleaf forests, but AIAV in GPP decreased significantly with latitude in evergreen needleleaf forests. Furthermore, RIAV in NEE, GPP, and Re appeared to increase significantly with latitude in deciduous broadleaf forests, but not in evergreen needleleaf forests. Correlation analyses showed air temperature was the primary environmental factor that determined RIAV of NEE in deciduous broadleaf forest across the North American sites, and none of the chosen climatic factors could explain RIAV of NEE in evergreen needleleaf forests. Mean annual NEE significantly increased with latitude in grasslands. Precipitation was dominant environmental factor for the spatial variation of magnitude and IAV in GPP and Re in grasslands. [less ▲]

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See detailLatitudinal structure of the Venus O2 infrared airglow: A signature of small-scale dynamical processes in the upper atmosphere
Gérard, Jean-Claude ULg; Soret, Lauriane ULg; Piccioni, Giuseppe et al

in Icarus (2014), 236

Images of the nightside limb of Venus have been obtained in the northern hemisphere with the VIRTIS multispectral infrared imager on board Venus Express between April 2006 and October 2008. We analyze the ... [more ▼]

Images of the nightside limb of Venus have been obtained in the northern hemisphere with the VIRTIS multispectral infrared imager on board Venus Express between April 2006 and October 2008. We analyze the latitudinal distribution of the O2(a1D) airglow limb profiles at 1.27 lm to characterize its distribution and variability. We show that the instantaneous structure of the emission is very different from the statistical global view of an enhanced emission near the equator, decreasing in brightness and slightly increasing in altitude toward the poles. The peak intensity of the limb profiles varies by a factor up to 50 between the brightest spots and the darkest regions. The bright airglow spots correspond to regions of enhanced downward flow of oxygen atoms originating from the dayside. Considerable variations in brightness and morphology are observed in the altitude–latitudinal distribution over a 24-h period. Analysis of the limb profiles indicates that secondary airglow peaks located at altitudes higher than the mean value of 96 km are observed on about 30% of the latitudinal cuts, but they are concentrated in narrow latitude areas extending over a few hundred kilometers. Most of them occur in transition regions between two altitude regimes in the 50 to 60 N region, possibly associated with the drop of the cloud top altitude observed equatorward of the ‘‘cold collar’’. We interpret these results as an indication that the strength of vertical transport in this mesosphere–thermosphere transition region is very variable both in location and time. This variability, also observed in nadir airglow images and wind measurements, is a key characteristic of the mesosphere–thermosphere transition region. It may be caused by fluctuations of the global day-to-night circulation generated by gravity waves. We show with a one dimensional model that local enhancements of eddy transport is a possibility. This variability is currently not accounted for by global circulation models that predict a single stable region of enhanced airglow in the vicinity of the antisolar point. [less ▲]

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See detailLattice Boltzmann 3D flow simulations on a metallic foam
Beugre, Djomice Antoine ULg; Calvo, Sébastien ULg; Dethier, Gérard ULg et al

in Journal of Computational & Applied Mathematics (2009)

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See detailLattice Boltzmann Simulation Code Optimization Based on Constant-time Circular Array Shifting
Dethier, Gérard ULg; de Marneffe, Pierre-Arnoul ULg; Marchot, Pierre ULg

in Procedia Computer Science (2011), 4

Lattice Boltzmann (LB) methods are a class of Computational Fluid Dynamics (CFD) methods for fluid flow simulation. LB simulation codes have high requirements regarding memory and computational power ... [more ▼]

Lattice Boltzmann (LB) methods are a class of Computational Fluid Dynamics (CFD) methods for fluid flow simulation. LB simulation codes have high requirements regarding memory and computational power: they may involve the update of several millions of floating point values thousands of times and therefore require several gigabytes of available memory and run for several days. Optimized implementations of LB methods minimize these requirements. An existing method based on a particular data layout and an associated implementation implying a constant time array shifting allows to reduce the execution time of LB simulations and almost minimize memory usage when compared to a naive implementation. In this paper, we show that this method can be further improved, both in memory usage and performances by slightly modifying the data layout and by using blocking in order to enhance data locality. [less ▲]

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See detailLattice dynamics and anomalous softening in the YbFe4Sb12 skutterudite
Moechel, A.; Sergueev, I.; Wille, H.-C. et al

in Physical Review (2011), 84(18),

The lattice dynamics of the filled skutterudite YbFe4Sb12 was studied by resonant ultrasound spectroscopy and an anomalous softening in the temperature dependence of the elastic constants at similar to 50 ... [more ▼]

The lattice dynamics of the filled skutterudite YbFe4Sb12 was studied by resonant ultrasound spectroscopy and an anomalous softening in the temperature dependence of the elastic constants at similar to 50 K was observed. This anomaly can not be explained by the dynamics of the filler, in contrast to other filled skutterudites. We have further investigated the origin of this anomaly using macroscopic and microscopic measurements. A rearrangement of the spectral weight of the Yb phonon states was observed in the temperature dependence of the density of phonon states, obtained by inelastic neutron scattering. We suggest that the anomaly is due to a change of the Yb valence state and that the anomaly and the phonon spectral weight rearrangement have the same origin. [less ▲]

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See detailLattice dynamics and ferroelectric instability of barium titanate
Ghosez, Philippe ULg; Gonze, X.; Michenaud, J. P.

in Ferroelectrics (1997), 194

Using first-principles calculations, we investigate the lattice dynamics of cubic and rhombohedral BaTiO3 and rye discuss the origin of the structural instability of this ferroelectric material. First, we ... [more ▼]

Using first-principles calculations, we investigate the lattice dynamics of cubic and rhombohedral BaTiO3 and rye discuss the origin of the structural instability of this ferroelectric material. First, we report results on the Born effective charges and the dielectric tensor and we emphasize the important reduction of these quantities in the ferroelectric phase, Then, the phonon frequencies at the Gamma point are calculated. We point out the similarity of theoretical eigenvectors in the cubic and rhombohedral phases. We examine the interaction of the vibration modes with the electric field and in particular the giant LO-TO splitting of the ferroelectric mode. Finally, separating the dipole-dipole interaction from the remaining short-range forces, we quantify the balance of forces leading to an unstable phonon in the cubic phase and we demonstrate its sensitivity to tiny effective charge changes. Within our decomposition, the stabilization of the unstable mode in the rhombohedral phase is produced by a reduction of the Born effective charges, while its stabilization under isotropic pressure is associated with a modification of the short-range forces. [less ▲]

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See detailLattice dynamics and magnetic properties in selected functional iron compounds
Herlitschke, Marcus ULg

Doctoral thesis (2015)

The presented thesis reports about to the investigation of four different materials with respect to their magnetic properties and their lattice dynamics. The carbodiimide FeNCN, which was recently ... [more ▼]

The presented thesis reports about to the investigation of four different materials with respect to their magnetic properties and their lattice dynamics. The carbodiimide FeNCN, which was recently synthesized for the first time and can be considered as an non-oxidic analogue to FeO, is discussed in chapter 2. The NCN 2− group bridges two iron and exhibits a double negative charge, similar to the oxygen in FeO. This material exhibits an increased magnetic order temperature as compared to FeO. FeNCN was investigated with magnetometry, Mössbauer spectroscopy and nuclear inelastic scattering, revealing an unusual behaviour of the hyperfine parameters below the ordering temperature. This observation is discussed with respect to the crystal field and the d-orbital level population with temperature. The investigation of the magnetocaloric material Mn5−x FexSi3 is reported in chapter 3 with focus on the interaction of magnetism and lattice dynamics. Among the Mn5−xFe x Si3 compounds, MnFe4 Si3 is the most interesting one due to the possible application as a room temperature refrigeration material. The investigation reveals that a direct measurement of the influence of the magnetocaloric effect on the density of iron phonon states is not possible, however, the elasticity was observed to be strongly influenced by this effect. The studies on the spin orientation in nanospheres and a NANOPERM alloy are discussed in chap ter 4 and chapter 5. Two approaches were followed in order to investigated the spin orientation, nuclear forward scattering and nuclear resonant small-angle X-ray scattering. In the first part, maghemite nanospheres are analysed with in-field nuclear forward scattering, revealing that the spins orient only partially along the direction of the applied magnetic field. A modeled magnetization calculated from the observed degree of spin orientation matches excellently the macroscopic magnetometry data and literature values. Though revealing the amount of oriented spins, nuclear forward scattering is not sensitive to their position in the nanoparticles. Thus, the nuclear forward scattering was combined with small-angle X-ray scattering, leading to small-angle patterns in dependence of the local spin orientation in the aforementioned samples. [less ▲]

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See detailLattice dynamics and structure of GeTe, SnTe and PbTe
Pereira, Paula Bauer; Sergueev, Ilya; Gorsse, Stephane et al

in PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS (2013), 250(7), 1300-1307

The lattice dynamics in the IV-VI compounds GeTe, SnTe and PbTe were studied by Te-125 and Sn-119 nuclear inelastic scattering and the obtained partial density of phonon states were compared with ... [more ▼]

The lattice dynamics in the IV-VI compounds GeTe, SnTe and PbTe were studied by Te-125 and Sn-119 nuclear inelastic scattering and the obtained partial density of phonon states were compared with published theoretical calculations. The phase purity and structure were characterized by high energy X-ray diffraction. The effect of the atomic arrangement, rhombohedral for GeTe and cubic for SnTe and PbTe, is visible in the density of phonon states. Vibrational properties are found to be in good agreement with available calculated data and the softer character of the NaCl-type structures in comparison with the rhombohedral GeTe is confirmed. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [less ▲]

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See detailLattice dynamics in antimony and tellurium based phase-change materials
Simon, Ronnie Ernst ULg

Doctoral thesis (2015)

Detailed reference viewed: 36 (4 ULg)