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See detailHaroun and the Sea of Stories
Delrez, Marc ULg

Conference (1991)

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See detailThe HARPS search for southern extra-solar planets XXXII. Only 4 planets in the Gl~581 system
Forveille, T.; Bonfils, X.; Delfosse, X. et al

E-print/Working paper (2011)

The Gl 581 planetary system has generated wide interest, because its 4 planets include both the lowest mass planet known around a main sequence star other than the Sun and the first super-Earth planet in ... [more ▼]

The Gl 581 planetary system has generated wide interest, because its 4 planets include both the lowest mass planet known around a main sequence star other than the Sun and the first super-Earth planet in the habitable zone of its star. A recent paper announced the possible discovery of two additional super-Earth planets in that system, one of which would be in the middle of the habitable zone of Gl 581. The statistical significance of those two discoveries has, however, been questioned. We have obtained 121 new radial velocity measurements of Gl 581 with the HARPS spectrograph on the ESO 3.6 m telescope, and analyse those together with our previous 119 measurements of that star to examine these potential additional planets. We find that neither is likely to exist with their proposed parameters. We also obtained photometric observations with the 2.5 m Isaac Newton Telescope during a potential transit of the inner planet, Gl 581e, which had a 5% geometric transit probability. Those observations exclude transits for planet densities under 4 times the Earth density within -0.2 sigma to +2.7 sigma of the predicted transit center. [less ▲]

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See detailThe HARPS search for southern extra-solar planets XXXV. Super-Earths around the M-dwarf neighbors Gl433 and Gl667C
Delfosse, X.; Bonfils, X.; Forveille, T. et al

in Astronomy and Astrophysics (2012), 553

Context. M dwarfs have often been found to have super-Earth planets with short orbital periods. These stars are thus preferential targets in searches for rocky or ocean planets in the solar neighborhood ... [more ▼]

Context. M dwarfs have often been found to have super-Earth planets with short orbital periods. These stars are thus preferential targets in searches for rocky or ocean planets in the solar neighborhood. Aims: Our research group recently announced the discovery of one and two low-mass planets around the M1.5V stars Gl 433 and Gl 667C, respectively. We found these planets with the HARPS spectrograph on the ESO 3.6-m telescope at La Silla Observatory, from observations obtained during the guaranteed time observing program of that instrument. Methods: We obtained additional HARPS observations of those two stars, for a total of 67 and 179 radial velocity measurements for Gl 433 and Gl 667C, respectively, and present here an orbital analysis of these extended data sets and our main conclusions about both planetary systems. Results: One of the three planets, Gl 667Cc, has a mass of only M2sini ~ 4.25 M⊕ and orbits in the central habitable zone of its host star. It receives only 10% less stellar energy from Gl 667C than the Earth receives from the Sun. However, planet evolution in the habitable zone can be very different if the host star is a M dwarf or a solar-like star, without necessarily questioning the presence of water. The two other planets, Gl 433b and Gl 667Cb, both have M2sini of ~5.5 M⊕ and periods of ~7 days. The radial velocity measurements of both stars contain longer timescale signals, which we fit with longer period Keplerians. For Gl 433, the signal probably originates in a magnetic cycle, while data of longer time span will be needed before conclusive results can be obtained for Gl 667C. The metallicity of Gl 433 is close to solar, while Gl 667C is metal poor with [Fe/H] ~ -0.6. This reinforces the recent conclusion that the occurrence of super-Earth planets does not strongly correlate with the stellar metallicity. [less ▲]

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See detailThe HARPS search for southern extra-solar planets. X. A m sin i = 11 M_â planet around the nearby spotted M dwarf <ASTROBJ>GJ 674</ASTROBJ>
Bonfils, X.; Mayor, M.; Delfosse, X. et al

in Astronomy and Astrophysics (2007), 474

Context: How planet properties depend on stellar mass is a key diagnostic of planetary formation mechanisms. Aims: This motivates planet searches around stars that are significantly more massive or less ... [more ▼]

Context: How planet properties depend on stellar mass is a key diagnostic of planetary formation mechanisms. Aims: This motivates planet searches around stars that are significantly more massive or less massive than the Sun, and in particular our radial velocity search for planets around very low-mass stars. Methods: As part of that program, we obtained measurements of <ASTROBJ>GJ 674</ASTROBJ>, an M 2.5 dwarf at d = 4.5 pc. These measurements have dispersion much in excess of their internal errors. An intensive observing campaign demonstrates that the excess dispersion is due to two superimposed coherent signals, with periods of 4.69 and 35 days. Results: These data are described well by a 2-planet Keplerian model where each planet has a ~11 M_â minimum mass. A careful analysis of the (low-level) magnetic activity of <ASTROBJ>GJ 674</ASTROBJ>, however, demonstrates that the 35-day period coincides with the stellar rotation period. This signal therefore originates in a spot inhomogeneity modulated by stellar rotation. The 4.69-day signal, on the other hand, is caused by a bona-fide planet, <ASTROBJ>GJ 674b</ASTROBJ>. Conclusions: Its detection adds to the growing number of Neptune-mass planets around M-dwarfs and reinforces the emerging conclusion that this mass domain is much more populated than the Jovian mass range. We discuss the metallicity distributions of M dwarf with and without planets and find a low 11% probability that they are drawn from the same parent distribution. Moreover, we find tentative evidence that the host star metallicity correlates with the total mass of their planetary system. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under the GTO program ID 072.C-0488 at Cerro La Silla (Chile). Radial-velocity, photometric and Ca II H+K index time series are only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strabg.fr/cgi-bin/qcat?J/A+A/474/293 [less ▲]

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See detailThe HARPS search for southern extra-solar planets. XIV. Gl 176b, a super-Earth rather than a Neptune, and at a different period
Forveille, T.; Bonfils, X.; Delfosse, X. et al

in Astronomy and Astrophysics (2009), 493

A 10.24-day Neptune-mass planet was recently announced as orbiting the nearby M2 dwarf Gl 176, based on 28 radial velocities measured with the HRS spectrograph on the Hobby-Heberly Telescope. We obtained ... [more ▼]

A 10.24-day Neptune-mass planet was recently announced as orbiting the nearby M2 dwarf Gl 176, based on 28 radial velocities measured with the HRS spectrograph on the Hobby-Heberly Telescope. We obtained 57 radial velocities of Gl 176 with the ESO 3.6 m telescope and the HARPS spectrograph, which is known for its sub-m s[SUP]-1[/SUP] stability. The median photon-noise standard error of our measurements is 1.1 m s[SUP]-1[/SUP], significantly lower than the 4.7 m s[SUP]-1[/SUP] of the HET velocities, and the 4-year period over which they were obtained overlaps considerably with the epochs of the HET measurements. The HARPS measurements show no evidence of a signal at the period of the putative HET planet, suggesting that its detection was spurious. We do find, on the other hand, strong evidence of a lower mass 8.4 M_Earth planet, in a quasi-circular orbit and at the different period of 8.78 days. The host star has moderate magnetic activity and rotates on a 39-day period, which we confirm through modulation of both contemporaneous photometry and chromospheric indices. We detect that period, as well, in the radial velocities, but it is well removed from the orbital period and offers no cause for confusion. This new detection of a super-Earth (2 M_Earth < M sin (i) < 10 M_Earth) around an M dwarf adds to the growing evidence that such planets are common around very low-mass stars. A third of the 20 known planets with M sin (i)< 0.1 M_Jup and 3 of the 7 known planets with M sin (i) < 10 M_Earth orbit an M dwarf, in contrast to just 4 of the ~300 known Jupiter-mass planets. Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at La Silla Observatory under program ID 072.C-0488. [less ▲]

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See detailThe HARPS search for southern extra-solar planets. XXXIV. A planetary system around the nearby M dwarf GJ163, with a super-Earth possibly in the habitable zone
Bonfils, X.; Lo Curto, G.; Correia, A. C. M. et al

E-print/Working paper (2013)

The meter-per-second precision achieved by today velocimeters enables the search for 1-10 M_Earth planets in the habitable zone of cool stars. This paper reports on the detection of 3 planets orbiting ... [more ▼]

The meter-per-second precision achieved by today velocimeters enables the search for 1-10 M_Earth planets in the habitable zone of cool stars. This paper reports on the detection of 3 planets orbiting GJ163 (HIP19394), a M3 dwarf monitored by our ESO/HARPS search for planets. We made use of the HARPS spectrograph to collect 150 radial velocities of GJ163 over a period of 8 years. We searched the RV time series for coherent signals and found 5 distinct periodic variabilities. We investigated the stellar activity and casted doubts on the planetary interpretation for 2 signals. Before more data can be acquired we concluded that at least 3 planets are orbiting GJ163. They have orbital periods of P_b=8.632+-0.002, P_c=25.63+-0.03 and P_d=604+-8 days and minimum masses msini = 10.6+-0.6, 6.8+-0.9, and 29+-3 M_Earth, respectively. We hold our interpretations for the 2 additional signals with periods P_(e)=19.4 and P_(f)=108 days. The inner pair presents an orbital period ratio of 2.97, but a dynamical analysis of the system shows that it lays outside the 3:1 mean motion resonance. GJ163c, in particular, is a super-Earth with an equilibrium temperature of T_eq = (302+-10) (1-A)^(1/4) K and may lie in the so called habitable zone for albedo values (A=0.34-0.89) moderately higher than that of Earth (A_Earth=0.2-0.3). [less ▲]

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See detailThe HARPS search for southern extra-solar planets: XXXI. The M-dwarf sample
Bonfils, X.; Delfosse, X.; Udry, S. et al

in Astronomy and Astrophysics (2013), 549

(Abridged) Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. This drives observations of a sample of 102 southern nearby ... [more ▼]

(Abridged) Searching for planets around stars with different masses probes the outcome of planetary formation for different initial conditions. This drives observations of a sample of 102 southern nearby M dwarfs, using a fraction of our guaranteed time on the ESO/HARPS spectrograph (Feb. 11th, 2003 to Apr. 1st 2009). This paper makes available the sample's time series, presents their precision and variability. We apply systematic searches and diagnostics to discriminate whether the observed Doppler shifts are caused by stellar surface inhomogeneities or by the radial pull of orbiting planets. We recover the planetary signals corresponding to 9 planets already announced by our group (Gl176b, Gl581b, c, d & e, Gl674b, Gl433b, Gl 667Cb and c). We present radial velocities that confirm GJ 849 hosts a Jupiter-mass planet, plus a long-term radial-velocity variation. We also present RVs that precise the planetary mass and period of Gl 832b. We detect long-term RV changes for Gl 367, Gl 680 and Gl 880 betraying yet unknown long-period companions. We identify candidate signals in the radial-velocity time series and demonstrate they are most probably caused by stellar surface inhomogeneities. Finally, we derive a first estimate of the occurrence of M-dwarf planets as a function of their minimum mass and orbital period. In particular, we find that giant planets (m sin i = 100-1,000 Mearth) have a low frequency (e.g. f<1% for P=1-10 d and f=0.02^{+0.03}_{-0.01} for P=10-100 d), whereas super-Earths (m sin i = 1-10 Mearth) are likely very abundant (f=0.36^{+0.25}_{-0.10} for P=1-10 d and f=0.35^{+0.45}_{-0.11} for P=10-100 d). We also obtained eta_earth=0.41^{+0.54}_{-0.13}, the frequency of habitable planets orbiting M dwarfs (1<m sin i<10 Mearth). For the first time, eta_earth is a direct measure and not a number extrapolated from the statistic of more massive and/or shorter-period planets. [less ▲]

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See detailHartree-Fock instabilities and electronic properties
Dehareng, Dominique ULg; Dive, Georges ULg

in Journal of Computational Chemistry (2000), 21(6), 483-504

Hartree-Fock instabilities are investigated for about 80 compounds, from acetylene to mivazerol (27 atoms) and a cluster of 18 water molecules, within a double zeta basis set. For most conjugated systems ... [more ▼]

Hartree-Fock instabilities are investigated for about 80 compounds, from acetylene to mivazerol (27 atoms) and a cluster of 18 water molecules, within a double zeta basis set. For most conjugated systems, the restricted Hartree-Fock wave function of the singlet fundamental state presents an external or so-called triplet instability. This behavior is studied in relation with the electronic correlation, the vicinity of the triplet and singlet excited states, the electronic delocalization linked with resonance, the nature of eventual heteroatoms, and the size of the systems. The case of antiaromatic systems is different, because they may present a very large internal Hartree-Fock instability. Furthermore, the violation of Hund's rule, observed for these compounds, is put in relation with the fact that the high symmetry structure in its singlet state has no feature of a diradical-like species. It appears that the triplet Hartree-Fock instability is directly related with the spin properties of nonnull orbital angular momentum electronic systems. (C) 2000 John Wiley & Sons, Inc. [less ▲]

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See detailHartree-Fock instabilities: Relation between an artifact and some properties.
Dehareng, Dominique ULg; Dive, Georges ULg; Geron, Christine

in Recent Research Development in Chemical Physics (2002), 3

The Hartree-Fock instability problem is reviewed and some of the instabilities are put in relation with particular properties of the system.

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See detailThe Hartree-Fock triplet instability: influence of conformation and substitution
Géron, Christine; Dive, Georges ULg; Dehareng, Dominique ULg

in Journal of Molecular Structure-theochem (2006), 760(1-3), 75-85

The triplet Hartree-Fock (HF) instability is investigated through the examples of substituted ethylenes and the small linear conjugated systems butadiene, hexatriene, octatetraene. A statistical analysis ... [more ▼]

The triplet Hartree-Fock (HF) instability is investigated through the examples of substituted ethylenes and the small linear conjugated systems butadiene, hexatriene, octatetraene. A statistical analysis is performed for several conformations of the latters. The second eigenvalue of the instability matrix appears to be able to discriminate the groups of unsaturated compounds. The HF instability is largely influenced by conjugation and mesomeric effects and thus by the geometry. The number of pi electrons is also an important factor. The electronic correlation related to the HF instability is not quantified by the energy difference between the post-HF and HF levels. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailHarun Farocki
Hamers, Jérémy ULg

Scientific conference (2009, May 27)

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See detailHarun Farocki: Auge/Maschine III
Hamers, Jérémy ULg

in Gielen, Denis (Ed.) Jeux de massacre: Pascal Bernier Patrick Codenys Harun Farocki (2009)

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See detailHarun Farocki: Schnittstelle/Section
Hamers, Jérémy ULg

in Dits : Petites Pièces Traitant d'un Sujet Familier ou d'Actualité (2009), 12(printemps-été 2009), 90-99

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See detailHas disinfection of endoscopes by automatic machines become obligatory?
Delwaide, Jean ULg; Pelckmans, P.; Defrance, P. et al

in Revue Médicale de Bruxelles (1999), 20(1), 49-50

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See detailHas oxygen depletion an impact on nutrients and macrofauna in a highly dynamic macrophytodetritus accumulation?
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Poster (2014, May 06)

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production ... [more ▼]

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production falls in autumn, to decay inside the meadow or to be exported to sand patches to form “exported litter accumulations”. These accumulations are highly dynamic depending on hydrodynamics and seafloor geomorphology. Literature says that low O2 conditions might occur inside litter accumulations, but the annual oxygen dynamics or its impact on the litter-associated macrofauna has never been measured. We focused on 2 exported litter accumulations in Calvi Bay (Corsica), during 2 years for a total of 8 seasons. For each season, we collected water samples (n=6) from 3 different strata: Water Column (WC), Water Just Above the litter (WJA) and Water Inside the litter (WI). Oxygen was measured for each replicate using a Winkler-based automated routine for oxygen concentration measurements on micro-volumes. At the same time, nutrients concentrations (PO4, NH4, and NO2+NO3) were measured in WC, WJA and WI, but also in the Interstitial Water (IW) using a spectrophotometric continuous flow analyzer (adapted for low nutrients level in an oligotrophic environment). In parallel, macrofaunal (size >500µm) samples (n=3-6) were also collected, counted and identified to the specific level. Our results show significant differences between O2 concentrations/saturation from WI and the two other strata. Significant differences were detected between seasons, sites and years for WI which is the only stratum where really low O2 conditions can be observed. Significant differences were also detected between seasons for both WC and WJA but no differences between sites and years. On the other hand no significant differences were detected between WC and WJA. A similar observation was made for the nutrients at the annual, seasonal and spatial level. Moreover differences are also observed between the nutrients themselves. Our data shows no correlation between WI O2 concentrations and saturation, and global macrofauna abundance or biodiversity. Results are more contrasting at an individual specific level for the 4 most dominant species. For two amphipod species, Gammarella fucicola (55% of the global abundance) and Gammarus aequicauda, no significant correlations were detected between their abundance and O2. For the leptostracan species, Nebalia strausi, a significant negative correlation with O2 concentration was detected. For the last amphipod species, Melita hergensis, a significant positive correlation was observed. Our analyses also show significant correlations between WI O2 concentration/saturation, and WI / IW nutrients concentration. To conclude, this work shows that WI is a very particular and dynamic environment considering O2 concentration and saturation. Low O2 conditions can be observed in WI but never in WC or WJA showing that internal processes and relations with the sediment determine the O2 dynamics in WI and showing a potential “barrier” effect between WI and WC. Moreover O2 dynamics and its consequences may play a role in the nutrients dynamics and cycles. It is clear that faunal responses to low O2 conditions are not identifiable at a global community level. At a specific level, we show a more complex situation: some species do not seem to be impacted by low O2 conditions, but some present a significant positive, or a significant negative response. This shows the existence and complexity of species-dependent low O2 tolerance/adaptation, and the importance of a specific level data analyses to detect responses of dominant litter associated macro- invertebrates to O2 concentration and saturation variations. [less ▲]

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See detailHas the fight against international terrorism undermined European data protection standards? A special regard to the perspectives of the transatlantic relationship
Berardo, Fiammetta ULg

Doctoral thesis (2013)

Il s’agit d'une analyse des accords PNR (Passenger Name Records) entre l’Union Européenne et les Etats Unis et plus en général des changements aux lois de protection de la vie privée qui sont intervenus ... [more ▼]

Il s’agit d'une analyse des accords PNR (Passenger Name Records) entre l’Union Européenne et les Etats Unis et plus en général des changements aux lois de protection de la vie privée qui sont intervenus dans les dernières années, surtout à la suite des événements du onze septembre 2001. La réflexion porte donc sur l’évolution du concept de protection des données personnelles vis à vis des nouveaux instruments de collecte d’informations et d’enquête. [less ▲]

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See detailHas the final countdown to wildlife extinction in Northern Central African Republic begun ?
Bouché, Philippe ULg; Renaud, Pierre-Cyril; Lejeune, Philippe ULg et al

in African Journal of Ecology (2010), 48(4), 1-10

The wildlife populations of Northern Central African Republic experienced precipitous declines during the 1970s and 1980s. While anecdotes coming out of the region indicate that the wildlife populations ... [more ▼]

The wildlife populations of Northern Central African Republic experienced precipitous declines during the 1970s and 1980s. While anecdotes coming out of the region indicate that the wildlife populations remain under serious threat, little is known about their status. An aerial sample count was carried out in the Northern Central African Republic at the end of the dry season in June 2005 and covered an 85,000 km2 complex landscape containing national parks, hunting reserves and community hunting areas. Results show a dramatic decline of wildlife since the previous survey in 1985. In 20 years, large mammals’ numbers decreased by 65%, probably <br />because of poaching and diseases brought by illegal cattle transhumance. Elephant (Loxodonta africana) and Buffon kob (Kobus kob) populations showed the greatest decline (over 80% each), while buffalo (Syncerus caffer), roan antelope (Hippotragus equinus) and Giant Lord’s Derby Eland (Taurotragus derbianus) populations seem stable or increasing over these last 20 years. The analysis of the wildlife population distribution by status of the different types of protected areas (national parks, hunting areas) showed that individual encounter rates of elephant and buffalo were lower in national parks than in neighbouring hunting areas, while those for roan, giraffe (Giraffa camelopardalis) and Buffon kob were higher in the national parks. [less ▲]

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See detailHas the world economy reached its globalization limit?
Miskiewicz, J.; Ausloos, Marcel ULg

in Physica A: Statistical Mechanics and its Applications (2010), 389(4), 797-806

The economy globalization measure problem is discussed. Four macroeconomic indices of twenty among the "richest" countries are examined. Four types of "distances" are calculated. Two types of networks are ... [more ▼]

The economy globalization measure problem is discussed. Four macroeconomic indices of twenty among the "richest" countries are examined. Four types of "distances" are calculated. Two types of networks are next constructed for each distance measure definition. It is shown that the globalization process can be best characterised by an entropy measure, based on entropy Manhattan distance. It is observed that a globalization maximum was reached during the interval 1970-2000. More recently a deglobalization process has been observed. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailHasard. Der Spieler in der deutschsprachigen Literaturgeschichte.
Gerrekens, Louis ULg; Küpper, Achim ULg

Book published by Königshausen & Neumann (2012)

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See detail"Hase und Igel" - antastbar!
Viehöver, Vera ULg

in Das andere Theater (2012), 82(3), 22-24

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