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See detailA dynamical energy-based hysteresis model for iron loss calculation in laminated cores
Steentjes, S.; Henrotte, F.; Geuzaine, Christophe ULg et al

in International Journal of Numerical Modelling (2014), 27(3), 433-443

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See detailDynamical evolution of titanium, strontium, and yttrium spots on the surface of the HgMn star HD 11753
Briquet, Maryline ULg; Korhonen, H.; González, J. F. et al

in Astronomy and Astrophysics (2010), 511

<BR /> Aims: We gathered about 100 high-resolution spectra of three typical HgMn (mercury-manganese) stars, <ASTROBJ>HD 11753</ASTROBJ>, <ASTROBJ>HD 53244</ASTROBJ>, and <ASTROBJ>HD 221507</ASTROBJ>, to ... [more ▼]

<BR /> Aims: We gathered about 100 high-resolution spectra of three typical HgMn (mercury-manganese) stars, <ASTROBJ>HD 11753</ASTROBJ>, <ASTROBJ>HD 53244</ASTROBJ>, and <ASTROBJ>HD 221507</ASTROBJ>, to search for slowly pulsating B-like pulsations and surface inhomogeneous distribution of various chemical elements. <BR /> Methods: Classical frequency analysis methods were used to detect line profile variability and to determine the variation period. Doppler imaging reconstruction was performed to obtain abundance maps of chemical elements on the stellar surface. <BR /> Results: For <ASTROBJ>HD 11753</ASTROBJ>, which is the star with the most pronounced variability, distinct spectral line profile changes were detected for Ti, Sr, Y, Zr, and Hg, whereas for <ASTROBJ>HD 53244</ASTROBJ> and <ASTROBJ>HD 221507</ASTROBJ> the most variable line profiles belong to the elements Hg and Y, respectively. We derived rotation periods for all three stars from the variations of radial velocities and equivalent widths of spectral lines belonging to inhomogeneously distributed elements: P[SUB]rot[/SUB] (<ASTROBJ>HD 11753</ASTROBJ>) = 9.54 d, P[SUB]rot[/SUB] (<ASTROBJ>HD 53244</ASTROBJ>) = 6.16 d, and P[SUB]rot[/SUB] (<ASTROBJ>HD 221507</ASTROBJ>) = 1.93 d. For <ASTROBJ>HD 11753</ASTROBJ> the Doppler imaging technique was applied to derive the distribution of the most variable elements Ti, Sr, and Y using two datasets separated by ~65 days. Results of Doppler imaging reconstruction revealed noticeable changes in the surface distributions of Ti II, Sr II, and Y II between the datasets, indicating the hitherto not well understood physical processes in stars with radiative envelopes that cause a rather fast dynamical chemical spot evolution. Based on observations obtained with the CORALIE Echelle Spectrograph on the 1.2-m Euler Swiss telescope, situated at La Silla, Chile.Postdoctoral Fellow of the Fund for Scientific Research, Flanders. [less ▲]

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See detailDynamical Flavor Origin of ZN Symmetries
Aristizabal Sierra, Diego ULg; Vicente, Avelino ULg; Fong, Sheng et al

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2015), 91(9),

Discrete Abelian symmetries (ZN) are a common “artifact” of beyond the standard model physics models. They provide different avenues for constructing consistent scenarios for lepton and quark mixing ... [more ▼]

Discrete Abelian symmetries (ZN) are a common “artifact” of beyond the standard model physics models. They provide different avenues for constructing consistent scenarios for lepton and quark mixing patterns, radiative neutrino mass generation as well as dark matter stabilization. We argue that these symmetries can arise from the spontaneous breaking of the Abelian U(1) factors contained in the global flavor symmetry transformations of the gauge-invariant kinetic Lagrangian. This will be the case provided the ultraviolet completion responsible for the Yukawa structure involves scalar fields carrying nontrivial U(1) charges. Guided by minimality criteria, we demonstrate the viability of this approach with two examples: first, we derive the “scotogenic” model Lagrangian, and second, we construct a setup where the spontaneous symmetry-breaking pattern leads to a Z3 symmetry which enables dark matter stability as well as neutrino mass generation at the two-loop order. This generic approach can be used to derive many other models, with residual ZN or ZN1×⋯×ZNk symmetries, establishing an intriguing link between flavor symmetries, neutrino masses and dark matter. [less ▲]

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See detailA dynamical model with hysteresis for the homogenization of ferromagnetic laminated cores
Henrotte, F.; Niyonzima, Innocent ULg; Steentjes, S. et al

in Proceedings of the 7th European Conference on Numerical Methods in Electromagnetism (NUMELEC2012) (2012, July)

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See detailDynamical Modeling of the Deep Impact Dust Ejecta Cloud
Bonev, T.; Ageorges, N.; Bagnulo, S. et al

in Käufl, H. U.; Sterken, C. (Eds.) Deep Impact as a World Observatory Event: Synergies in Space, Time, and Wavelength (2009)

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its ... [more ▼]

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its position and shape are governed by the physical properties of the dust grains. We use a Monte Carlo model to describe the evolution of the post-impact dust plume. The results of our dynamical simulations are compared to the data obtained with FORS2footnote{FORS stands for \underline{FO}cal Reducer and low dispersion Spectrograph for the Very Large Telescope (VLT) of the European Southern Observatory (ESO).} to derive the particle size distribution and the total amount of material contained in the dust ejecta cloud. [less ▲]

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See detailDynamical modeling of the Deep Impact dust ejecta cloud
Bonev, Tanyu; Ageorges, Nancy; Bagnulo, Stefano et al

Report (2007)

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its ... [more ▼]

The collision of Deep Impact with comet 9P/Tempel 1 generated a bright cloud of dust which dissipated during several days after the impact. The brightness variations of this cloud and the changes of its position and shape are governed by the physical properties of the dust grains. We use a Monte Carlo model to describe the evolution of the post-impact dust plume. The results of our dynamical simulations are compared to the data obtained with FORS2, the FOcal Reducer and low dispersion Spectrograph for the VLT of the European Southern Observatory (ESO), to derive the particle size distribution and the total amount of material contained in the dust ejecta cloud. [less ▲]

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See detailDynamical modelling from resting-state brain imaging
Liegeois, Raphaël ULg

Doctoral thesis (2015)

The statistical dependencies among neuroimaging time courses observed in different brain regions are collectively named functional connectivity (FC). This quantity is widely used in order to characterize ... [more ▼]

The statistical dependencies among neuroimaging time courses observed in different brain regions are collectively named functional connectivity (FC). This quantity is widely used in order to characterize normal brain functioning or neurodegenerative diseases. It is classically measured in a static way, by averaging the dependencies over the whole imaging acquisition. However, there is increasing evidence that considering the temporal fluctuations of FC leads to a finer description of FC properties and corresponding brain function. This observation is the starting point of the work developed throughout this thesis. First, we study the role of cerebral anatomy in the FC fluctuations. We observe that it guides transitions of FC between different patterns supporting consciousness-related processes such as mind wandering. Following this new characterisation of the fluctuating nature of FC, we develop statistical tools capturing static and dynamic properties of FC. We first introduce three markers of FC, collectively named spatiotemporal connectivity (STC), and computed from the power spectral density of the neuroimaging time series. STC captures spatial properties of FC, as classically computed, but also dynamical properties. We show on real data that STC provides a finer characterisation of FC, as well as higher robustness against inherent flaws of the imaging modality considered in our study. Then, in order to identify dynamical patterns of FC at the whole-brain level, we recast the concept of component analysis in the context of dynamical models. The corresponding development is based on a particular representation of statistical interactions: dynamical graphical models. We first propose an algorithm providing a decomposition of these models in a sparse contribution, reflecting parsimony of the direct interactions between cerebral regions, and a low-rank contribution, modelling the presence of hidden variables spreading a common behaviour in many of these regions. Then, we propose to interpret the identified hidden variables as dynamical neuronal networks, as for component analysis, but with an additional spectral characterisation of the corresponding components. In conclusion, this thesis presents descriptive contributions from the analyses of several datasets, and methodological contributions inspired from the properties of these datasets. [less ▲]

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See detailDynamical problems for dust particles
Lemaitre, Anne; Jancart, Sylvie ULg

Conference (1996)

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See detailDynamical properties of DNA-ligand complexes under shear stress: insights from classical molecular dynamics
Fresch, Barbara ULg

Conference (2013, June 19)

Nucleic acids are flexible molecules: their dynamical properties play an essential role in molecular recognition and self-assembly. In the biological environment, because of mechanical forces acting at ... [more ▼]

Nucleic acids are flexible molecules: their dynamical properties play an essential role in molecular recognition and self-assembly. In the biological environment, because of mechanical forces acting at the molecular level, DNA is transiently deformed, cut and resealed, damaged and repaired, and the strands pulled apart and then re-annealed. These unique features make short DNA oligonucleotides promising building blocks in the development of “bottom-up” nano-devices and molecular logic machines. Single molecule manipulation techniques (Atomic Force Microscopy/ Optical Tweezers) allow detailed investigation of nucleic acids response to the application of controlled mechanical stress. Interpretations of these data in terms of molecular structural changes and dynamical properties call for a collaborative effort between experiments and theoretical/computational modeling. We have theoretically investigated the dynamical properties a DNA dodecamer and its complex with two different binders (Hoechst 33258 and Ethidium cation) by performing fully atomistic classical Molecular Dynamics (MD) simulations. We focused on the modeling of the so-called overstretching transition occurring when double stranded DNA is subjected to a shear stress until separation of the two strands occurs. The results of our analysis reveal the molecular details of the overstretching dynamics and point out the effects of the binders on the structure and the dynamics of the oligonucleotide under stress. The minor groove binder Hoechst 33258 acts as a zip between the two strands enhancing the lifetime of some base-pairs during the pulling experiment while ethidium cation, which is an intercalator, facilitates the separation of the double helix at high elongations. The understanding of the interactions between the binders and the helix at the molecular level gives insights into the unbinding pathways probed by Single Molecule Force Spectroscopy (SMFS). [less ▲]

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See detailDynamical Regimes of a Granular Gas in Microgravity : a Molecular Dynamics Study
Opsomer, Eric ULg; Ludewig, François ULg; Vandewalle, Nicolas ULg

in Journal of Physics: Conference Series (2011)

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See detailDynamical Spot Evolution in HD 11753
Korhonen, H.; Hubrig, S.; Briquet, Maryline ULg et al

in Magnetic Stars. Proceedings of the International Conference, held in the Special Astrophysical Observatory of the Russian AS, August 27- September 1, 2010, Eds: I. I. Romanyuk and D. O. Kudryavtsev (2011)

Our recent studies of HD 11753, a late B-type star showing a HgMn peculiarity for the first time revealed the presence of a fast dynamical evolution of chemical spots on the surface of this chemically ... [more ▼]

Our recent studies of HD 11753, a late B-type star showing a HgMn peculiarity for the first time revealed the presence of a fast dynamical evolution of chemical spots on the surface of this chemically peculiar early-type star. These observations suggest a hitherto unknown physical process operating in stars with outer radiative envelopes. Furthermore, we have also discovered existence of magnetic fields on HgMn stars that were up to now considered non-magnetic. Here we will discuss the dynamical spot evolution in HD 11753 in detail, and also summarize our new results on the magnetic fields of the AR Aur binary system. [less ▲]

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See detailDynamical study of non adiabatic unimolecular reactions: The conical intersection between the B 2B2 and à 2A1 states of H2O+.
Dehareng, Dominique ULg; Chapuisat, Xavier; Lorquet, Jean-Claude ULg et al

in Journal of Chemical Physics (1983), 78(3), 1246-1264

The conical intersection conecting the B 2A' and A 2A' states of the H2O+ ion is studied. The two potential energy surfaces are calculated ab initio by the SCF/CI method within the Cs point group. The ... [more ▼]

The conical intersection conecting the B 2A' and A 2A' states of the H2O+ ion is studied. The two potential energy surfaces are calculated ab initio by the SCF/CI method within the Cs point group. The nonadiabatic elements <A|d/dq|B> are computed for several cross sections throughout the potential energy surfaces. A transformation to the diabatic representation is performed. The linear model is found to be a good approximation in the region close to the apex of the cone. The global functions t(s) and T(S) governing the nonadiabatic transition probability are calculated; their shapes are those predicted by the Landau-Zener model (in the Nikitin bidimensional version). A dynamical study is undertaken by means of classical trajectory calculations on the upper adiabatic potential energy surface. An average transition probability Ptr is derived. Excitation of rotation or of the bending mode of H2O before photon impact has no influence on Ptr. Excitation of the symmetrical or antisymmetrical valence mode of H2O lowers Ptr. The shape of ln(1-Ptr) as a function of time indicates the existence of two distinct regimes at short and intermediate time ranges, characterized by two different rate constants k1 and k2 respectively. The rate constants are of the order of 10exp(14) s-1. k1 exhibits a maximum as a function of the absorbed energy Eabs whereas k2 decreases as a function of Eabs. [less ▲]

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See detailDynamical study of the pentaquark antidecuplet
Stancu, Floarea ULg

in Physics Letters B (2004), 595

Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Theta(+) belongs. The framework is a constituent quark model where the short ... [more ▼]

Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Theta(+) belongs. The framework is a constituent quark model where the short-range interaction has a flavour-spin structure. In this model the lowest pentaquarks have positive parity. Each antidecuplet member is described by a variational solution with the Pauli principle properly taken into account. By fitting the mass of Theta(+) of minimal content uudd, the mass of Xi(--), of minimal content ddss (u) over bar, is predicted at approximately 1960 MeV. The influence of the octet-antidecuplet mixing on the masses of the Y = I and 0 pentaquarks is considered within the same model and the role of the hyperfine interaction in this mixing is pointed out. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailDynamical thermalization in Bose-Hubbard systems
Schlagheck, Peter ULg; Shepelyansky, Dima L.

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2016), 93

We numerically study a Bose-Hubbard ring of finite size with disorder containing a finite number of bosons that are subject to an on-site two-body interaction. Our results show that moderate interactions ... [more ▼]

We numerically study a Bose-Hubbard ring of finite size with disorder containing a finite number of bosons that are subject to an on-site two-body interaction. Our results show that moderate interactions induce dynamical thermalization in this isolated system. In this regime the individual many-body eigenstates are well described by the standard thermal Bose-Einstein distribution for well-defined values of the temperature and the chemical potential, which depend on the eigenstate under consideration. We show that the dynamical thermalization conjecture works well at both positive and negative temperatures. The relations to quantum chaos, quantum ergodicity, and the Åberg criterion are also discussed. [less ▲]

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See detailDynamical thermalization in Bose-Hubbard systems
Schlagheck, Peter ULg; Shepelyansky, Dima L.

Conference (2016, March)

A bosonic many-body system can exhibit the Bose-Einstein distribution in its single-particle eigenstates not only if it is coupled to a heat and particle reservoir, but also if it is subject to a two-body ... [more ▼]

A bosonic many-body system can exhibit the Bose-Einstein distribution in its single-particle eigenstates not only if it is coupled to a heat and particle reservoir, but also if it is subject to a two-body interaction of moderately low strength which couples the single-particle eigenstates with each other. We numerically verify this dynamical thermalization conjecture within disordered Bose-Hubbard rings of finite size whose parameters are chosen such that the dynamics of the system can be expected to be ergodic [1]. This allows one to associate with each many-body eigenstate of the Bose-Hubbard system well-defined (positive or negative) values for the effective temperature and the effective chemical potential which depend on the energy per particle of the eigenstate under consideration [1]. With this information one can then predict the populations of single-particle eigenmodes within each many-body eigenstate of the system according to the Bose-Einstein distribution, without knowing more details about the quantum dynamics of the many-body system. [less ▲]

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See detailDynamical Tunneling - Theory and Experiment
Keshavamurthy, Srihari; Schlagheck, Peter ULg

Book published by CRC Press (2011)

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See detailDynamical, dielectric, and elastic properties of GeTe investigated with first-principles density functional theory
Shaltaf, R.; Durgun, Engin ULg; Raty, Jean-Yves ULg et al

in Physical Review. B, Condensed Matter and Materials Physics (2008), 78

The dynamical, dielectric, and elastic properties of GeTe, a ferroelectric material in its low-temperature rhombohedral phase, have been investigated using first-principles density functional theory. We ... [more ▼]

The dynamical, dielectric, and elastic properties of GeTe, a ferroelectric material in its low-temperature rhombohedral phase, have been investigated using first-principles density functional theory. We report the electronic energy bands, phonon-dispersion curves, electronic and low-frequency dielectric tensors, infrared reflectivity, Born effective charges, and elastic and piezoelectric tensors and compare them with the existing theoretical and experimental results, as well as with similar quantities available for other ferroelectric materials, when appropriate. [less ▲]

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See detailDynamically constrained ensemble perturbations - application to tides on the West Florida Shelf
Barth, Alexander ULg; Alvera Azcarate, Aïda ULg; Beckers, Jean-Marie ULg et al

in Ocean Science (2009), 5(3), 259-270

A method is presented to create an ensemble of perturbations that satisfies linear dynamical constraints. A cost function is formulated defining the probability of each perturbation. It is shown that the ... [more ▼]

A method is presented to create an ensemble of perturbations that satisfies linear dynamical constraints. A cost function is formulated defining the probability of each perturbation. It is shown that the perturbations created with this approach take the land-sea mask into account in a similar way as variational analysis techniques. The impact of the land-sea mask is illustrated with an idealized configuration of a barrier island. Perturbations with a spatially variable correlation length can be also created by this approach. The method is applied to a realistic configuration of the West Florida Shelf to create perturbations of the M2 tidal parameters for elevation and depth-averaged currents. The perturbations are weakly constrained to satisfy the linear shallow-water equations. Despite that the constraint is derived from an idealized assumption, it is shown that this approach is applicable to a non-linear and baroclinic model. The amplitude of spurious transient motions created by constrained perturbations of initial and boundary conditions is significantly lower compared to perturbing the variables independently or to using only the momentum equation to compute the velocity perturbations from the elevation. [less ▲]

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