Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailOrbit Determination for Gaia Spectroscopic Binaries
Jancart, Sylvie ULg; Pourbaix, D.

in O'Flaherty, K.S.; Perryman, M.A.C (Eds.) The Three-Dimensional Universe with Gaia (2005, January 01)

Synthetic radial velocities for a population of 2300+ known spectroscopic binaries are generated according to the present scanning law. The effect of the distribution of the observations and of the noise ... [more ▼]

Synthetic radial velocities for a population of 2300+ known spectroscopic binaries are generated according to the present scanning law. The effect of the distribution of the observations and of the noise on the orbit fitting is investigated. According to our preliminary results short periods, below one day, will be hard to identify among the many aliases, even in the absence of noise. Requirements in terms of computing power for this shell task are estimated in conjunction with the adopted algorithm for the period search part of the orbit reconstruction. These results are for binaries detected in the Radial Velocity Spectrometer only. [less ▲]

Detailed reference viewed: 4 (0 ULg)
Full Text
See detailOrbital dynamics characteristics of a QB50 CubeSat performing atmospheric reentry
Asma, C.; Naviaux, J.; Kerschen, Gaëtan ULg et al

in Proceedings of the AIAA Atmospheric Flight Mechanics Conference (2010)

The QB50 mission has the scientific objective to study the temporal and spatial variations of a number of key parameters in the lower thermosphere with a network of 50 CubeSats, each performing identical ... [more ▼]

The QB50 mission has the scientific objective to study the temporal and spatial variations of a number of key parameters in the lower thermosphere with a network of 50 CubeSats, each performing identical in-situ measurements. One of these 50 CubeSats, the von Karman Institute Atmospheric Re-Entry CubeSat, will further be equipped by a thermal protection system and a dedicated sensor pack to study the atmospheric re-entry. This paper is devoted to the orbital dynamics analysis performed for the QB50 mission and the atmospheric re-entry trajectory analysis for a double unit CubeSat. The main focus is on the sensitivity of the results on atmospheric models, drag coefficient and the launch date. Typical atmospheric re-entry trajectories, including the stagnation point heat flux values are calculated using three different methods for three different scenarios. The predicted heat flux values will be used in the preliminary design of the thermal protection system of the VKI atmospheric re-entry CubeSat, which is to be the first CubeSat to be used as an atmospheric re-entry demonstrator. [less ▲]

Detailed reference viewed: 108 (1 ULg)
Full Text
Peer Reviewed
See detailAn orbital period of 0.94days for the hot-Jupiter planet WASP-18b
Hellier, Coel; Anderson, D. R.; Cameron, A Collier et al

in Nature (2009), 460

The `hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which ... [more ▼]

The `hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only ~0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94days and a mass of ten Jupiter masses (10M[SUB]Jup[/SUB]), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 10[SUP]6[/SUP], as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System. [less ▲]

Detailed reference viewed: 31 (6 ULg)
Full Text
See detailOrbital rendez-vous using differential drag in the QB50 constellation
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Proceedings of the AIAA/AAS Astrodynamics Specialist Conference (2012)

Detailed reference viewed: 34 (12 ULg)
Full Text
See detailLes orbites quasi elliptiques, les potentiels riemanniens et les forces centrales
Swings, Polydore ULg

in Bulletin de la Classe des Sciences. Académie Royale de Belgique (1927), XIII(2), 88-89

Detailed reference viewed: 3 (0 ULg)
Full Text
Peer Reviewed
See detailOrbitofrontal cortex involvement in chronic analgesic-overuse headache evolving from episodic migraine
Fumal, Arnaud ULg; Laureys, Steven ULg; Di Clemente, Laura et al

in Brain (2006), 129(Pt 2), 543-550

The way in which medication overuse transforms episodic migraine into chronic daily headache is unknown. To search for candidate brain areas involved in this process, we measured glucose metabolism with ... [more ▼]

The way in which medication overuse transforms episodic migraine into chronic daily headache is unknown. To search for candidate brain areas involved in this process, we measured glucose metabolism with 18-FDG PET in 16 chronic migraineurs with analgesic overuse before and 3 weeks after medication withdrawal and compared the data with those of a control population (n = 68). Before withdrawal, the bilateral thalamus, orbitofrontal cortex (OFC), anterior cingulate gyrus, insula/ventral striatum and right inferior parietal lobule were hypometabolic, while the cerebellar vermis was hypermetabolic. All dysmetabolic areas recovered to almost normal glucose uptake after withdrawal of analgesics, except the OFC where a further metabolic decrease was found. A subanalysis showed that most of the orbitofrontal hypometabolism was due to eight patients overusing combination analgesics and/or an ergotamine-caffeine preparation. Medication overuse headache is thus associated with reversible metabolic changes in pain processing structures like other chronic pain disorders, but also with persistent orbitofrontal hypofunction. The latter is known to occur in drug dependence and could predispose subgroups of migraineurs to recurrent analgesic overuse. [less ▲]

Detailed reference viewed: 25 (0 ULg)
Full Text
Peer Reviewed
See detailOrbitofrontal dysfunction related to both apathy and disinhibition in frontotemporal dementia
Peters, Frederic; Perani, Daniela; Herholz, Karl et al

in Dementia & Geriatric Cognitive Disorders (2006), 21(5-6), 373-379

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral ... [more ▼]

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral disturbances have been distinguished in fv-FTD patients: apathetic and disinhibited manifestations. In this study, we searched for relationships between brain metabolism and presence of apathetic or disinhibited behavior. Metabolic activity and behavioral data were collected in 41 fv-FTD patients from European PET centers. A conjunction analysis of the PET data showed an expected impairment of metabolic activity in the anterior cingulate, ventromedial and orbital prefrontal cortex, the dorsolateral prefrontal cortex and the left anterior insula in fv-FTD subjects compared to matched controls. A correlation was observed between disinhibition scores on the Neuropsychiatric Inventory scale and a cluster of voxels located in the posterior orbitofrontal cortex ( 6, 28, - 24). Comparison of brain activity between apathetic and nonapathetic fv-FTD patients from two centers also revealed a specific involvement of the posterior orbitofrontal cortex in apathetic subjects ( 4, 22, - 22). The results confirm that the main cerebral metabolic impairment in fv-FTD patients affects areas specializing in emotional evaluation and demonstrate that decreased orbitofrontal activity is related to both disinhibited and apathetic syndromes in fv-FTD. Copyright (C) 2006 S. Karger AG, Basel. [less ▲]

Detailed reference viewed: 141 (5 ULg)
See detailOrbits of Hipparcos metal-poor stars with well-defined spectroscopic abundances.
Bancken, F.; Jehin, Emmanuel ULg; Ferraz-Mello, S.

in Impact of Modern Dynamics in Astronomy (1998, July)

We investigate the orbits of metal-poor stars in a modified Ostriker and Caldwell Galactic mass model. These stars have well-determined spectroscopic abundances and our objective is to search for a ... [more ▼]

We investigate the orbits of metal-poor stars in a modified Ostriker and Caldwell Galactic mass model. These stars have well-determined spectroscopic abundances and our objective is to search for a relationship between these abundances and the characteristics of orbits such as excentricity, chaoticity... [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
See detailOrbits of language operations: finiteness and upper bounds
Charlier, Emilie ULg

Scientific conference (2011, August)

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailOrco mediates olfactory behaviors and winged morph differentiation induced by alarm pheromone in the grain aphid, Sitobion avenae
Fan, Jia; Zhang, Yong; Francis, Frédéric ULg et al

in Insect Biochemistry and Molecular Biology (2015), 64

Olfaction is crucial for short distance host location and pheromone detection by insects. Complexes of olfactory receptors (ORs) are composed of odor-specific ORs and OR co-receptors (Orco). Orcos are ... [more ▼]

Olfaction is crucial for short distance host location and pheromone detection by insects. Complexes of olfactory receptors (ORs) are composed of odor-specific ORs and OR co-receptors (Orco). Orcos are widely co-expressed with odor-specific ORs and are conserved across insect taxa. A number of Orco orthologs have been studied to date, although none has been identified in cereal aphids. In this study, an Orco gene ortholog was cloned from the grain aphid, Sitobion avenae, and named “SaveOrco”; RNA interference (RNAi) reduced the expression of SaveOrco to 34.11% in aphids, resulting in weaker EAG (electroantennogram) responses to plant volatiles (Z-3-hexene-1-ol; methyl salicylate, MeSA) and aphid alarm pheromone (E-b-farnesene, EBF). Aphid wing differentiation induced by EBF was investigated in both RNAi treated and untreated aphids. EBF induced production of winged aphids in both pre-natal and postnatal periods in untreated aphids, but no such induction was observed in the RNAi-treated aphids. We conclude that SaveOrco is crucial for the aphid's response to pheromones and other volatiles, and is involved in wing differentiation triggered by EBF [less ▲]

Detailed reference viewed: 45 (0 ULg)
Full Text
Peer Reviewed
See detailThe order Herpesvirales.
Davison, Andrew J; Eberle, Richard; Ehlers, Bernhard et al

in Archives of Virology (2009), 154(1), 171-7

The taxonomy of herpesviruses has been updated by the International Committee on Taxonomy of Viruses (ICTV). The former family Herpesviridae has been split into three families, which have been ... [more ▼]

The taxonomy of herpesviruses has been updated by the International Committee on Taxonomy of Viruses (ICTV). The former family Herpesviridae has been split into three families, which have been incorporated into the new order Herpesvirales. The revised family Herpesviridae retains the mammal, bird and reptile viruses, the new family Alloherpesviridae incorporates the fish and frog viruses, and the new family Malacoherpesviridae contains a bivalve virus. Three new genera have been created in the family Herpesviridae, namely Proboscivirus in the subfamily Betaherpesvirinae and Macavirus and Percavirus in the subfamily Gammaherpesvirinae. These genera have been formed by the transfer of species from established genera and the erection of new species, and other new species have been added to some of the established genera. In addition, the names of some nonhuman primate virus species have been changed. The family Alloherpesviridae has been populated by transfer of the genus Ictalurivirus and addition of the new species Cyprinid herpesvirus 3. The family Malacoherpesviridae incorporates the new genus Ostreavirus containing the new species Ostreid herpesvirus 1. [less ▲]

Detailed reference viewed: 98 (12 ULg)
Full Text
See detailOrder reduction in time integration caused by velocity projection
Arnold, Martin; Cardona, Alberto; Bruls, Olivier ULg

in Proceedings of the 3rd Joint International Conference on Multibody System Dynamics and the 7th Asian Conference on Multibody Dynamics (2014, July)

Holonomic constraints restrict the configuration of a multibody system to a subset of the configuration space. They imply so called hidden constraints at the level of velocity coordinates that may ... [more ▼]

Holonomic constraints restrict the configuration of a multibody system to a subset of the configuration space. They imply so called hidden constraints at the level of velocity coordinates that may formally be obtained from time derivatives of the original holonomic constraints. A numerical solution that satisfies hidden constraints as well as the original constraint equations may be obtained considering both types of constraints simultaneously in each time step (stabilized index-2 formulation) or using projection techniques. Both approaches are well established in the time integration of differential-algebraic equations. Recently, we have introduced a generalized- alpha Lie group time integration method for the stabilized index-2 formulation that achieves second order convergence for all solution components. In the present paper, we show that a separate velocity projection would be less favourable since it may result in an order reduction and in large transient errors after each projection step. This undesired numerical behaviour is analysed by a one-step error recursion that considers the coupled error propagation in differential and algebraic solution components. This one-step error recursion has been used before to prove second order convergence for the application of generalized-alpha methods to constrained systems. As a technical detail, we discuss the extension of these results from symmetric, positive definite mass matrices to the rank deficient case. [less ▲]

Detailed reference viewed: 39 (7 ULg)
Full Text
Peer Reviewed
See detailOrder short-term memory capacity predicts nonword reading and spelling in first and second grade
Binamé, Florence ULg; Poncelet, Martine ULg

in Reading and Writing An Interdisciplinary Journal (in press)

Recent theories of short-term memory (STM) distinguish between item information, which reflects the temporary activation of long-term representations stored in the language system, and serial-order ... [more ▼]

Recent theories of short-term memory (STM) distinguish between item information, which reflects the temporary activation of long-term representations stored in the language system, and serial-order information, which is encoded in a specific representational system that is independent of the language network. Some studies examining the relationship between reading acquisition and verbal STM for order and item information separately in beginning readers have found that order STM capacity is independently predictive of nonword decoding abilities in first grade, but item STM is not. In this longitudinal study, we first aimed to explore whether this finding also holds for nonword spelling abilities. We also sought to determine whether order STM capacity remains an independent predictor of nonword decoding and spelling abilities in the second year of reading instruction. For this purpose, 70 typically developing children were followed over 3 years, from kindergarten to second grade. In kindergarten, children were administered order and item STM tasks and phonological awareness tasks, in addition to tasks assessing letter name knowledge, vocabulary knowledge, and nonverbal reasoning. In first and second grades, the children’s word and nonword reading and spelling abilities were assessed. The results revealed that order STM capacity was a robust independent predictor of nonword reading and spelling abilities in first and second grade, but was not related to the abilities to read and spell words. The specific role of order STM in the acquisition of the sublexical reading and spelling routes is discussed. [less ▲]

Detailed reference viewed: 28 (4 ULg)
Full Text
Peer Reviewed
See detailOrdered nanoporous membranes based on diblock copolymers with high chemical stability and tunable separation properties
Li, Xian-Feng; Fustin, Charles-André; Lefèvre, Nathalie ULg et al

in Journal of Materials Chemistry (2010), 20(21), 4333-4339

Detailed reference viewed: 12 (1 ULg)
Full Text
Peer Reviewed
See detailOrderly process of sequential cytokine stimulation is required for activation and maximal proliferation of primitive human bone marrow CD34+ hematopoietic progenitor cells residing in G0.
Ladd, A. C.; Pyatt, R.; GOTHOT, André ULg et al

in Blood (1997), 90(2), 658-68

Bone marrow (BM) CD34+ cells residing in the G0 phase of cell cycle may be the most suited candidates for the examination of cell cycle activation and proliferation of primitive hematopoietic progenitor ... [more ▼]

Bone marrow (BM) CD34+ cells residing in the G0 phase of cell cycle may be the most suited candidates for the examination of cell cycle activation and proliferation of primitive hematopoietic progenitor cells (HPCs). We designed a double simultaneous labeling technique using both DNA and RNA staining with Hoechst 33342 and Pyronin Y, respectively, to isolate CD34+ cells residing in G0(G0CD34+). Using long-term BM cultures and limiting dilution analysis, G0CD34+ cells were found to be enriched for primitive HPCs. In vitro proliferation of G0CD34+ cells in response to sequential cytokine stimulation was examined in a two-step assay. In the first step, cells received a primary stimulation consisting of either stem cell factor (SCF), Flt3-ligand (FL), interleukin-3 (IL-3), or IL-6 for 7 days. In the second step, cells from each group were washed and split into four or more groups, each of which was cultured again for another week with one of the four primary cytokines individually, or in combination. Tracking of progeny cells was accomplished by staining cells with PKH2 on day 0 and with PKH26 on day 7. Overall examination of proliferation patterns over 2 weeks showed that cells could progress into four phases of proliferation. Phase I contained cytokine nonresponsive cells that failed to proliferate. Phase II contained cells dividing up to three times within the first 7 days. Phases III and IV consisted of cells dividing up to five divisions and greater than six divisions, respectively, by the end of the 14-day period. Regardless of the cytokine used for primary stimulation, G0CD34+ cells moved only to phase II by day 7, whereas a substantial percentage of cells incubated with SCF or FL remained in phase I. Cells cultured in SCF or FL for the entire 14-day period did not progress beyond phase III but proliferated into phase IV (with <20% of cells remaining in phases I and II) if IL-3, but not IL-6, was substituted for either cytokine on day 7. G0CD34+ cells incubated with IL-3 for 14 days proliferated the most and progressed into phase IV; however, when SCF was substituted on day 7, cells failed to proliferate into phase IV. Most intriguing was a group of cells, many of which were CD34+, detected in cultures initially stimulated with IL-3, which remained as a distinct population, mostly in G0/G1, unable to progress out of phase II regardless of the nature of the second stimulus received on day 7. A small percentage of these cells expressed cyclin E, suggesting that their proliferation arrest may have been mediated by a cyclin-related disruption in cell cycle. These results suggest that a programmed response to sequential cytokine stimulation may be part of a control mechanism required for maintenance of proliferation of primitive HPCs and that unscheduled stimulation of CD34+ cells residing in G0 may result in disruption of cell-cycle regulation. [less ▲]

Detailed reference viewed: 15 (1 ULg)
See detailOrders in quaternion algebras
Pays, Isabelle ULg

Conference (1990, March)

Detailed reference viewed: 8 (0 ULg)