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See detailOscillating blue stragglers, gamma Doradus stars and eclipsing binaries in the open cluster NGC 2506
Arentoft, T.; De Ridder, J.; Grundahl, F. et al

in Astronomy and Astrophysics (2007), 465

Context: This is the first step in a project to combine studies of eclipsing binaries and oscillating stars to probe the interior of Blue Stragglers (BS). This may imply a way to discriminate ... [more ▼]

Context: This is the first step in a project to combine studies of eclipsing binaries and oscillating stars to probe the interior of Blue Stragglers (BS). This may imply a way to discriminate observationally between different birth mechanisms of BS stars. Aims: We study the open cluster NGC 2506 which contains oscillating BS stars and detached eclipsing binaries for which accurate parameters can be derived. This will tightly constrain the cluster isochrone and provide an absolute mass, radius and luminosity-scale for the cluster stars along with the cluster age, metallicity and distance. The present work focuses on obtaining the light curves of the binaries and determine their orbital periods, on obtaining power spectra of the oscillating BS stars to select targets for follow-up studies, and on searching for gamma Doradus type variables which are also expected to be present in the cluster. Methods: With a two-colour, dual-site photometric campaign we obtained 3120 CCD-images of NGC 2506 spread over four months. We analysed the BI time-series of the oscillating stars and used simulations to derive statistical uncertainties of the resulting frequencies, amplitudes and phases. A preliminary mode-identification was performed using frequency ratios for the oscillating BS stars, and amplitude ratios and phase differences for a population of newly detected gamma Doradus stars. Results: We quadrupled the number of known variables in NGC 2506 by discovering 3 new oscillating BS stars, 15 gamma Doradus stars and four new eclipsing binaries. The orbital periods of 2 known, detached eclipsing binaries were derived. We discovered a BS star with both p-mode and g-mode variability and we confronted our gamma Doradus observations with state-of-the-art seismic models, but found significant discrepancy between theory and observations. Conclusions: . NGC 2506 is an excellent target for asteroseismic tests of stellar models, as strong external constraints can be imposed on the models of a population of more than 20 oscillating stars of different types. Based on observations obtained at the Flemish Mercator telescope on La Palma, Spain, the Danish 1.5-m telescope at ESO, La Silla, Chile, and on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programme 075.D-0206(B)). Catalog of individual photometry measurements for all variables is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/465/965 [less ▲]

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See detailOscillation mode lifetimes of red giants observed during the initial and first anticentre long run of CoRoT
Hekker, Saskia; Barban, Caroline; Baudin, Frederic et al

in Astronomy and Astrophysics (2010), 520

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See detailOscillation of Saturn's southern auroral oval
Nichols, J. D.; Clarke, J. T.; Cowley, S. W. H. et al

in Journal of Geophysical Research (2008), 113(A11),

Near-planetary-period oscillations in the Cassini plasma and magnetic field data have been observed throughout Saturn's magnetosphere despite the fact that Saturn's internal magnetic field is apparently ... [more ▼]

Near-planetary-period oscillations in the Cassini plasma and magnetic field data have been observed throughout Saturn's magnetosphere despite the fact that Saturn's internal magnetic field is apparently highly axisymmetric. In addition, the period of the Saturn kilometric radiation has been shown to vary over time. In this paper we present results from the recent Hubble Space Telescope observations of Saturn's southern ultraviolet auroral emission. We show that the center of the auroral oval oscillates with period 10.76 h +/- 0.15 h for both January 2007 and February 2008, i.e., close to the periods determined for oscillations in other magnetospheric phenomena. The motion of the oval center is described for 2007 by an ellipse with semimajor axis similar to 1.4 degrees +/- 0.3 degrees oriented toward similar to 09-21 h LT, eccentricity similar to 0.93, and center offset from the spin axis by similar to 1.8 degrees toward similar to 04 h LT. For 2008 the oscillation is consistent with an ellipse with semimajor axis similar to 2.2 degrees +/- 0.3 degrees oriented toward similar to 09-21 h LT, eccentricity similar to 0.99, and a center offset from the spin axis by similar to 2.2 degrees toward similar to 03 h LT. The motion of the auroral oval is thus highly elliptical in both cases, and the major oscillation axis is oriented toward prenoon/premidnight. This result places an independent constraint on the magnitude of the planet's dipole tilt and may also indicate the presence of an external current system that imposes an asymmetry in the ionospheric field modulated close to the planetary period. [less ▲]

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See detailOscillations in rapidly rotating stars
Reese, Daniel ULg

in Astronomische Nachrichten (2010, December 01), 331

Spurred by the spectroscopic and interferometric observations of rapidly rotating stars and the highly accurate pulsation data coming from asteroseismology space missions, theoreticians have spent many ... [more ▼]

Spurred by the spectroscopic and interferometric observations of rapidly rotating stars and the highly accurate pulsation data coming from asteroseismology space missions, theoreticians have spent many years developing models for such stars and studying their oscillations. This has led to the discovery of new phenomena and new types of pulsation modes. In what follows, a review is given of the different methods used to model the effects of rotation on stellar pulsations, as well as a description of these effects on inertial, gravito-inertial, r and acoustic modes. [less ▲]

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See detailOscillations in the basal ganglia: illustration of a cellular effect at the network level
Dethier, Julie ULg; Drion, Guillaume; Franci, Alessio et al

Poster (2013, June)

Parkinson’s disease (PD) is a neuro-degenerative pathology affecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of ... [more ▼]

Parkinson’s disease (PD) is a neuro-degenerative pathology affecting the basal ganglia (BG), a set of small subcortical nervous system nuclei. The hallmark of the disease is a dopaminergic denervation of the striatum, al- tering information patterns along movement-related ganglia-mediated path- ways in the brain. Severe motor symptoms result from the pathological state: tremor at rest, bradykinesia, akinesia, and rigidity. The transition to the disease state correlates with a switch in the firing mode of the neurons in the BG, from tonic pacemaker activity to burst firing. At the network level, macro-electrode recordings reveal excessive oscillations in the beta (8- 30Hz) frequency band. The oscillations generation mechanism and their functional role remain under debate. We propose a network model where a cellular mechanism controls the dynamical state of the network. In our model, the oscillatory state impacts the neural information processing prop- erties of the network. The network model predicts that a single decrease of the dopaminergic level in the parkinsonnian condition switches the network into an abnormal oscillatory dynamical and globally insensitive state. The brief dopaminergic increase prior to voluntary movements suppresses beta oscillations to drive the network to a conductive state to sensory processing and cognition. [less ▲]

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See detailOscillations of bride stay cables induced by periodic motions of deck and/or towers
Pinto da Costa, Antonio; Martins, Joao; Branco, F. et al

in Journal of Engineering Mechanics (1996), 122(7), 613-622

Cables in stayed bridges may oscillate due to periodic motions of the deck or tower induced by wind or traffic.

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See detailLes oscillations respiratoires ou de second ordre de la pression sanguine
Fredericq, Léon ULg

in Archives Internationales de Physiologie (1906), IV

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See detailOscillator Models and Collective Motion: spatial patterns in the dynamics of engineered and biological networks
Paley, Derek; Leonard, Naomi E.; Sepulchre, Rodolphe ULg et al

in IEEE Control Systems Magazine (2007), 27(4), 89-105

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See detailOscillator Models and Collective Motion: Splay State Stabilization of Self-Propelled Particles
Paley, Derek; Leonard, Naomi; Sepulchre, Rodolphe ULg

in Proceedings of the 44th IEEE Conference on Decision and Control and European Control Conference (2005)

This paper presents a Lyapunov design for the stabilization of collective motion in a planar kinematic model of N particles moving at constant speed. We derive a control law that achieves asymptotic ... [more ▼]

This paper presents a Lyapunov design for the stabilization of collective motion in a planar kinematic model of N particles moving at constant speed. We derive a control law that achieves asymptotic stability of the splay state formation, characterized by uniform rotation of N evenly spaced particles on a circle. In designing the control law, the particle headings are treated as a system of coupled phase oscillators. The coupling function which exponentially stabilizes the splay state of particle phases is combined with a decentralized beacon control law that stabilizes circular motion of the particles in the splay state formation around the center of mass of the group. [less ▲]

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See detailOscillator strength for K-like iron, cobalt and nickel
Quinet, Pascal ULg; Hansen, J E

in Proceedings of the 5th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas (1996)

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See detailOscillator strengths for Ca-like iron, cobalt and nickel (Fe VII, Co VIII, Ni IX)
Quinet, Pascal ULg; Hansen, J E

in Journal of Physics : B Atomic Molecular & Optical Physics (1996), 29

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See detailOscillator strengths for lines of astrophysical interest in Rh II
Quinet, Pascal ULg; Biémont, Emile ULg; Palmeri, P et al

in Astronomy and Astrophysics (2012), 537

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See detailOscillator strengths for the gallium-like ions Br V - In XIX
Biémont, Emile ULg; Quinet, Pascal ULg

in Atomic Spectra and Oscillator Strengths for Astrophysics and Fusion Research (1990)

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See detailOscillator strengths for transitions in Pd II
Quinet, Pascal ULg

in Proceedings of the 5th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas (1996)

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See detailOscillatority of Nonlinear Systems with Static Feedback
Efimov, Denis ULg; Fradkov, Alexander

in SIAM Journal on Control & Optimization (2009), 48(2), 618-640

New Lyapunov-like conditions for oscillatority of dynamical systems in the sense of Yakubovich are proposed. Unlike previous results these conditions are applicable to nonlinear systems and allow for ... [more ▼]

New Lyapunov-like conditions for oscillatority of dynamical systems in the sense of Yakubovich are proposed. Unlike previous results these conditions are applicable to nonlinear systems and allow for consideration of nonperiodic, e.g., chaotic modes. Upper and lower bounds for oscillations amplitude are obtained. The relation between the oscillatority bounds and excitability indices for the systems with the input are established. Control design procedure providing nonlinear systems with oscillatority property is proposed. Examples illustrating proposed results for Van der Pol system, Lorenz system, and Hindmarsh–Rose neuron model as well as computer simulation results are given. [less ▲]

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See detailOscillators as Systems and Synchrony as a Design Principle
Sepulchre, Rodolphe ULg

in Menini, L.; Zaccarian, L.; Abdallah, C. T. (Eds.) Current trends in nonlinear systems and control (2005)

The chapter presents an expository survey of ongoing research by the author on a system theory for oscillators. Oscillators are regarded as open systems that can be interconnected to robustly stabilize ... [more ▼]

The chapter presents an expository survey of ongoing research by the author on a system theory for oscillators. Oscillators are regarded as open systems that can be interconnected to robustly stabilize ensemble phenomena characterized by a certain level of synchrony. The first part of the chapter provides examples of design (stabilization) problems in which synchrony plays an important role. The second part of the chapter shows that dissipativity theory provides an interconnection theory for oscillators. [less ▲]

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See detailOsculating circle with microscopes within microscopes
Bair, Jacques ULg; Henry, Valérie ULg

in Foundations of Science (2013), 18(2), 319-325

Classically, an osculating circle at a point of a planar curve is introduced technically, often with formula giving its radius and the coordinates of its center. In this note, we propose a new and ... [more ▼]

Classically, an osculating circle at a point of a planar curve is introduced technically, often with formula giving its radius and the coordinates of its center. In this note, we propose a new and intuitive definition of this concept: among all the circles which have, at the considered point, the same tangent as the studied curve and thus seem equal to the curve through a microscope, the osculating circle is this that seems equal to the curve through a microscope within microscope. [less ▲]

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See detailOSEM reconstruction of pinhole SPECT acquired in body contour mode.
Seret, Alain ULg; Flérès, D.; Defrise, Michel

Poster (2003)

Detailed reference viewed: 40 (1 ULg)
See detailOser la qualité, un référentiel en Communauté française de Belgique et son accompagnement
Pirard, Florence ULg

in Rayna, S.; Bouve, C.; Moisset, P. (Eds.) Pour un accueil de qualité de la petite enfance: quel curriculum ? (2009)

Detailed reference viewed: 46 (3 ULg)