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See detailFirst-light LBT Nulling Interferometric Observations: Warm Exozodiacal Dust Resolved within a Few AU of eta Crv
Defrere, Denis ULiege; Hinz, P. M.; Skemer, A. J. et al

in Astrophysical Journal (2015), 799

We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81-12.41 μm) emission around the nearby main-sequence star η ... [more ▼]

We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81-12.41 μm) emission around the nearby main-sequence star η Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% ± 0.35% over a field-of-view of 140 mas in radius (~2.6 AU for the distance of η Crv) and shows no significant variation over 35° of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by the Spitzer Infrared Spectrograph (IRS; ~23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the solar zodiacal cloud unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (~3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust for the distance where the insolation is the same as Earth's (2.3 AU). [less ▲]

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See detailFirst-line crizotinib versus chemotherapy in ALK-positive lung cancer.
Solomon, Benjamin J.; Mok, Tony; Kim, Dong-Wan et al

in The New England journal of medicine (2014), 371(23), 2167-77

BACKGROUND: The efficacy of the ALK inhibitor crizotinib as compared with standard chemotherapy as first-line treatment for advanced ALK-positive non-small-cell lung cancer (NSCLC) is unknown. METHODS: We ... [more ▼]

BACKGROUND: The efficacy of the ALK inhibitor crizotinib as compared with standard chemotherapy as first-line treatment for advanced ALK-positive non-small-cell lung cancer (NSCLC) is unknown. METHODS: We conducted an open-label, phase 3 trial comparing crizotinib with chemotherapy in 343 patients with advanced ALK-positive nonsquamous NSCLC who had received no previous systemic treatment for advanced disease. Patients were randomly assigned to receive oral crizotinib at a dose of 250 mg twice daily or to receive intravenous chemotherapy (pemetrexed, 500 mg per square meter of body-surface area, plus either cisplatin, 75 mg per square meter, or carboplatin, target area under the curve of 5 to 6 mg per milliliter per minute) every 3 weeks for up to six cycles. Crossover to crizotinib treatment after disease progression was permitted for patients receiving chemotherapy. The primary end point was progression-free survival as assessed by independent radiologic review. RESULTS: Progression-free survival was significantly longer with crizotinib than with chemotherapy (median, 10.9 months vs. 7.0 months; hazard ratio for progression or death with crizotinib, 0.45; 95% confidence interval [CI], 0.35 to 0.60; P<0.001). Objective response rates were 74% and 45%, respectively (P<0.001). Median overall survival was not reached in either group (hazard ratio for death with crizotinib, 0.82; 95% CI, 0.54 to 1.26; P=0.36); the probability of 1-year survival was 84% with crizotinib and 79% with chemotherapy. The most common adverse events with crizotinib were vision disorders, diarrhea, nausea, and edema, and the most common events with chemotherapy were nausea, fatigue, vomiting, and decreased appetite. As compared with chemotherapy, crizotinib was associated with greater reduction in lung cancer symptoms and greater improvement in quality of life. CONCLUSIONS: Crizotinib was superior to standard first-line pemetrexed-plus-platinum chemotherapy in patients with previously untreated advanced ALK-positive NSCLC. (Funded by Pfizer; PROFILE 1014 ClinicalTrials.gov number, NCT01154140.). [less ▲]

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See detailA first-order energy-dissipative momentum-conserving scheme for elasto-plasticity using the variational updates formulation
Noels, Ludovic ULiege; Stainier, Laurent ULiege; Ponthot, Jean-Philippe ULiege

in Computer Methods in Applied Mechanics & Engineering (2008), 197(6-8), 706726

In a previous paper [L. Noels, L. Stainier, J.-P. Ponthot, An energy momentum conserving algorithm using the variational formulation of visco-plastic updates, Int. J. Numer. Methods Engrg. 65 (2006) 904 ... [more ▼]

In a previous paper [L. Noels, L. Stainier, J.-P. Ponthot, An energy momentum conserving algorithm using the variational formulation of visco-plastic updates, Int. J. Numer. Methods Engrg. 65 (2006) 904-942] the authors demonstrated the efficiency of the variational formulation of elasto-plastic updates to develop energy-momentum conserving time integration algorithms. Indeed, within such a framework, the stress tensor always derives from an incremental potential, even when plastic behavior is considered. Therefore the verification of the conservation of energy in the non-linear range can easily be demonstrated: the sum of the reversible stored energy and irreversible dissipated energy exactly corresponds to the work of the external forces applied to the structure. Although this formulation was shown to be accurate and robust, the introduction of numerical dissipation for high-frequency numerical modes can be necessary to simulate complex phenomena. In this work, we propose a modification of the variational updates framework to introduce this numerical property, leading to a new energy-dissipative momentum-conserving time-integration algorithm for elasto-plasticity. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailFirst-order Logic and Numeration Systems
Charlier, Emilie ULiege

in Sequences, Groups, and Number Theory (in press)

The Büchi-Bruyère theorem states that a multidimensional set of non-negative integers is b-recognizable if and only if it is b-definable. This result is a powerful tool for showing that many properties of ... [more ▼]

The Büchi-Bruyère theorem states that a multidimensional set of non-negative integers is b-recognizable if and only if it is b-definable. This result is a powerful tool for showing that many properties of b-automatic sequences are decidable. Going a step further, first-order logic can be used to show that many enumeration problems of b-automatic sequences can be described by b-regular sequences. The latter sequences can be viewed as a generalization of b-automatic sequences to integer-valued sequences. These techniques were extended to two wider frameworks: U-recognizable multidimensional sets of non-negative integers and multidimensional beta-recognizable sets of reals. In the second case, real numbers are represented by infinite words, and hence, the notion of beta-recognizability is defined by means of Büchi automata. Again, logic-based characterizations of $U$-recognizable (resp. beta-recognizable) sets allows us to obtain various decidability results. The aim of this chapter is to present a survey of this very active research domain. [less ▲]

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See detailFirst-principle study of crystals exhibiting an incommensurate phase transition
Gonze, X.; Caracas, R.; Sonnet, R. et al

in AIP Conference Proceedings (2000), 535

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See detailFirst-principles and experimental studies of hexagonal YMnO3 single crystals and epitaxial films
Prikockyte, Alina ULiege

Doctoral thesis (2012)

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk ... [more ▼]

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk and in thin film forms. Yttrium manganite belongs to the class of ABO3 compounds. Most theoretical studies of ferroelectricity to date were concentrated on cubic perovskite ABO3. Yttrium manganite is hexagonal and is an improper ferroelectric. We were interested to study theoretically and experimentally how these two features behave in thin film form. Our study is organized as follows. [less ▲]

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See detailFirst-principles calculation of kinetic barriers and metastability for the corundum-to-Rh/sub 2/O/sub 3/(II) transition in Al/sub 2/O/sub 3/
Xu, Bin ULiege; Stokes, Harold; Dong, Jianjun

in Journal of Physics : Condensed Matter (2010), 22(31), 3154036-3154036

We demonstrate that the rhombohedral corundum crystal and the orthorhombic Rh/sub 2/O/sub 3/ (II) crystal are structurally related by a diffusionless monoclinic common subgroup pathway, along which the ... [more ▼]

We demonstrate that the rhombohedral corundum crystal and the orthorhombic Rh/sub 2/O/sub 3/ (II) crystal are structurally related by a diffusionless monoclinic common subgroup pathway, along which the intermediate structures have the space group P2/c symmetry. This transformation pathway is energetically favored because the majority of Al-O bonds are preserved during the transition. Only 1/3 of the four-coordinated anions and 1/2 of the six-coordinated cations break and reform a single bond. No other bonds are broken in the transformation. Our calculated forward (corundum-to-Rh/sub 2/O/sub 3/ (II)) enthalpy barrier (about 140 meV/atom) in Al/sub 2/O/sub 3/ is not pressure-sensitive at least up to 160 GPa, which is consistent with the observed metastability of the corundum phase around room temperature. In contrast, we predict a significantly decreasing backward (Rh/sub 2/O/sub 3/ (II)-to-corundum) enthalpy barrier on decompression, which suggests that the high-pressure Rh/sub 2/O/sub 3/ (II) phase of Al/sub 2/O/sub 3/ is unlikely to be recoverable at ambient conditions. In addition, we propose a general, common subgroup-based approach to compare elastic properties of two phases with different Bravais lattices. By treating both rhombohedral and orthorhombic phases with common monoclinic P2/c unit cells (non-primitive for the corundum phase), we show that the elastic properties of the high-pressure Rh/sub 2/O/sub 3/ (II) phase are very comparable to those of the ambient corundum phase. [less ▲]

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See detailFirst-principles calculation of the band offset at BaO/BaTiO3 and SrO/SrTiO3 interfaces
Junquera, J.; Zimmer, M.; Ordejon, P. et al

in Physical Review. B, Condensed Matter and Materials Physics (2003), 67

We report first-principles density-functional pseudopotential calculations on the atomic structures, electronic properties, and band offsets of BaO/BaTiO3 and SrO/SrTiO3 nanosized heterojunctions grown on ... [more ▼]

We report first-principles density-functional pseudopotential calculations on the atomic structures, electronic properties, and band offsets of BaO/BaTiO3 and SrO/SrTiO3 nanosized heterojunctions grown on top of a silicon substrate. The density of states at the junction does not reveal any electronic induced interface states. A dominant perovskite character is found at the interface layer. The tunability of the band offset with the strain conditions imposed by the substrate is studied. Using previously reported theoretical data available for Si/SrO, Si/BaO, SrTiO3/Pt, and BaTiO3/SrRuO3 interfaces we extrapolate the band alignments along two gate stacks of technological interest: Si/SrO/SrTiO3/Pt and Si/BaO/BaTiO3/SrRuO3 heterostructures. [less ▲]

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See detailFirst-principles calculation of the electronic, dielectric, and dynamical properties of CaF2
Verstraete, Matthieu ULiege; Gonze, Xavier

in Physical Review. B : Condensed Matter (2003), 68

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See detailFirst-principles calculations of dielectric and effective charge tensors in Barium Titanate
Ghosez, Philippe ULiege; Gonze, X.; Michenaud, J. P.

in Ferroelectrics (1994), 153

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See detailFirst-principles calculations of the nonlinear optical susceptibilities and Raman scattering spectra of lithium niobate
Hermet, P.; Veithen, M.; Ghosez, Philippe ULiege

in Journal of Physics : Condensed Matter (2007), 19

Nonlinear optical susceptibilities and nonresonant Raman scattering spectra of the ferroelectric phase of lithium niobate (LiNbO3) are computed using a first-principles approach based on density ... [more ▼]

Nonlinear optical susceptibilities and nonresonant Raman scattering spectra of the ferroelectric phase of lithium niobate (LiNbO3) are computed using a first-principles approach based on density functional theory and taking advantage of a recent implementation based on the nonlinear response formalism and the 2n+1 theorem. Infrared reflectivity spectra of the ferroelectric phase of LiNbO3 are also calculated. New assignments are proposed for the E-modes, clarifying a longstanding debate in the literature. In addition, it is shown that knowledge of the nonlinear optical susceptibility tensor of LiNbO3 does not significantly alter the profile of its Raman spectra in a configuration where the longitudinal optic modes are involved. [less ▲]

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See detailFirst-principles calculations of the structural and dynamical properties of ferroelectric YMnO3
Prikockyte, Alina ULiege; Bilc, Daniel ULiege; Hermet, Patrick ULiege et al

in Physical Review. B, Condensed Matter and Materials Physics (2011), 84

We report the structural and dynamical properties of the ground state ferroelectricP63cm structure of hexagonal YMnO3. The lattice parameters, atomic positions, local magnetic moment of Mn atoms, band gap ... [more ▼]

We report the structural and dynamical properties of the ground state ferroelectricP63cm structure of hexagonal YMnO3. The lattice parameters, atomic positions, local magnetic moment of Mn atoms, band gap, and -point phonons are calculated within the local spin-density approximation plus Hubbard U term and the B1-WC hybrid functional. Our results are discussed in comparison to theoretical and experimental values available in the literature. Based on our first-principles calculations, we propose a reassignment of certain modes. We also discuss the relation between the phonon modes of the ferroelectric P63cm phase and those of the paraelectric P63/mmc phase that condense at the phase transition. [less ▲]

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See detailFirst-principles characterization of the four phases of barium titanate
Ghosez, Philippe ULiege; Gonze, X.; Michenaud, J. P.

in Ferroelectrics (1999), 220(1-2), 1-15

Using a first-principles approach, the four phases of perovskite barium titanate are studied. We determine the lattice parameter, the bulk modulus and the cohesive energy of the cubic phase; the relaxed ... [more ▼]

Using a first-principles approach, the four phases of perovskite barium titanate are studied. We determine the lattice parameter, the bulk modulus and the cohesive energy of the cubic phase; the relaxed atomic positions in the three ferroelectric structures; and the evolution of the electronic properties from one phase to the other. The role of electronic exchange-correlation energy in the stabilization of the different phases is also investigated. [less ▲]

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See detailFirst-principles characterization of the P21ab ferroelectric phase of Aurivillius Bi2WO6
Djani-Ait, Hania ULiege; Hermet, Patrick ULiege; Ghosez, Philippe ULiege

in Journal of Physical Chemistry C (2014), 118

The structural, dielectric, dynamical, elastic, piezoelectric and nonlinear optical (second-order susceptibility and Pockels tensors) properties of Bi2WO6 in its P21ab ferroelectric ground state are ... [more ▼]

The structural, dielectric, dynamical, elastic, piezoelectric and nonlinear optical (second-order susceptibility and Pockels tensors) properties of Bi2WO6 in its P21ab ferroelectric ground state are determined using density functional theory. The calculation of infrared and Raman spectra on single crystal allowed us to clarify the assignment of experimental phonon modes, considering the good agreement between the calculated and the experimental Raman spectra obtained on polycrystal. The calculation of the elastic constants con rms the elastic stability of the crystal and allow us to estimate the Young and shear moduli of polycrystalline samples. The piezoelectric constants have signi cant intrinsic values comparable to those of prototypical ABO3 ferroelectrics. The electro-optic response is strongly dominated by the ionic contribution of transverse optic modes, yielding sizable Pockels coe cients around 9 pm/V along the polar direction. [less ▲]

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See detailFirst-principles computation of material properties: the ABINIT software project
Gonze, X.; Beuken, J. M.; Caracas, R. et al

in Computational Materials Science (2002), 25(3), 478-492

The density functional theory (DFT) computation of electronic structure, total energy and other properties of materials, is a field in constant progress. In order to stay at the forefront of knowledge, a ... [more ▼]

The density functional theory (DFT) computation of electronic structure, total energy and other properties of materials, is a field in constant progress. In order to stay at the forefront of knowledge, a DFT software project can benefit enormously from widespread collaboration, if handled properly. Also, modern software engineering concepts can considerably ease its development. The ABINIT project relies upon these ideas: freedom of sources, reliability, portability, and self-documentation are emphasised, in the development of a sophisticated plane-wave pseudopotential code. We describe ABINITv3.0, distributed under the GNU General Public License. The list of ABINITv3.0 capabilities is presented, as well as the different software techniques that have been used until now: PERL scripts and CPP directives treat a unique set of FORTRAN90 source files to generate sequential (or parallel) object code for many different platforms; more than 200 automated tests secure existing capabilities; strict coding rules are followed; the documentation is extensive, including online help files, tutorials, and HTML-formatted sources. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailFirst-Principles conductance of nanoscale junctions from the polarizability of finite systems
Verstraete, Matthieu ULiege; Bokes, Peter; Godby, Rex W

in Journal of Chemical Physics (2009), 130

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See detailFirst-principles design of efficient solar cells using two-dimensional arrays of core-shell and layered SiGe nanowires
Pekoz, Rengin; Malcioglu, Osman Baris ULiege; Raty, Jean-Yves ULiege

in Physical Review. B, Condensed Matter and Materials Physics (2011), 83(3), 0353176-03531760353176

Research for third generation solar cell technology has been driven by the need to overcome the efficiency and cost problems encountered by current crystalline Si- and thin-film-based solar cells. Using ... [more ▼]

Research for third generation solar cell technology has been driven by the need to overcome the efficiency and cost problems encountered by current crystalline Si- and thin-film-based solar cells. Using first-principles methods, Ge/Si and Si/Ge core/shell and Si-Ge layered nanowires are shown to possess the required qualities for an efficient use in photovoltaic applications. We investigate the details of their band structure, effective mass, absorption property, and charge-carrier localization. The strong charge separation and improved absorption in the visible spectrum indicate a remarkable quantum efficiency that, combined with new designs, compares positively with bulk Si. [less ▲]

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See detailFirst-principles model potentials for lattice-dynamical studies: general methodology and example of application to ferroic perovskite oxides
Wojdeł, Jacek; Hermet, Patrick ULiege; Ljungberg, Mathias et al

in Journal of Physics : Condensed Matter (2013), 25

We present a scheme to construct model potentials, with parameters computed from first principles, for large-scale lattice-dynamical simulations of materials. We mimic the traditional solid-state approach ... [more ▼]

We present a scheme to construct model potentials, with parameters computed from first principles, for large-scale lattice-dynamical simulations of materials. We mimic the traditional solid-state approach to the investigation of vibrational spectra, i.e., we start from a suitably chosen reference configuration of the compound and describe its energy as a function of arbitrary atomic distortions by means of a Taylor series. Such a form of the potential-energy surface is general, trivial to formulate for any material, and physically transparent. Further, such models involve clear-cut approximations, their precision can be improved in a systematic fashion, and their simplicity allows for convenient and practical strategies to compute/fit the potential parameters. We illustrate our scheme with two challenging cases in which the model potential is strongly anharmonic, namely, the ferroic perovskite oxides PbTiO3 and SrTiO3. Studying these compounds allows us to better describe the connection between the so-called effective-Hamiltonian method and ours (which may be seen as an extension of the former), and to show the physical insight and predictive power provided by our approach—e.g., we present new results regarding the factors controlling phase-transition temperatures, novel phase transitions under elastic constraints, an improved treatment of thermal expansion, etc. [less ▲]

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See detailFirst-principles modeling of ferroelectric oxide nanostructures
Ghosez, Philippe ULiege; Junquera, J.

in Handbook of theoretical and computational nanotechnology (2006)

Detailed reference viewed: 39 (0 ULiège)