Search results for " Methods"
showing 10 items of 4102 documents
Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope
2012
The ANTARES telescope observes a full hemisphere of the sky all the time with a duty cycle close to 100%. This makes it well suited for an extensive observation of neutrinos produced in astrophysical transient sources. In the surrounding medium of blazars, i.e. active galactic nuclei with their jets pointing almost directly towards the observer, neutrinos may be produced together with gamma-rays by hadronic interactions, so a strong correlation between neutrinos and gamma-rays emissions is expected. The time variability information of the studied source can be obtained by the gamma-ray light curves measured by the LAT instrument on-board the Fermi satellite. If the expected neutrino flux ob…
AUGMENTED REALITY
2011
Already used in very specific areas such as in military and medical or academic research, in 2009 thanks to improved technology, augmented reality is to reach wider audiences and as information campaigns, advertising-augmented published in newspapers or on the network, and through a growing number of applications for mobile phones, particularly iPhone. "The Augmented Reality on the desktop computer is based on the use of markers, or ARtags, and stylized drawings, which are shown to the webcam, are recognized by the PC, and which are overlaid in real-time multimedia content: video, audio , 3D objects, etc.. Normally, applications of augmented reality are based on Adobe Flash technology and t…
Theoretical study of photoinduced ring-isomerization in the 1,2,4-oxadiazole series
2004
Abstract A theoretical study of photoinduced ring-isomerization of 3-amino-5-methyl- and 3-amino-5-phenyl-1,2,4-oxadiazoles is reported. The results well agree with the reported experimental data: in particular, they explain the ring-photoisomerization into the corresponding 2-amino-1,3,4-oxadiazoles through a ring contraction-ring expansion route; moreover, the occurrence of competing pathways involving both the ring contraction and the internal cyclization–isomerization mechanism during irradiation of the 5-alkyl substituted substrates in the presence of a base has been also substantiated.
Low temperature rate coefficients of the H + CH+ → C+ + H2 reaction: New potential energy surface and time-independent quantum scattering
2015
The observed abundances of the methylidyne cation, CH(+), in diffuse molecular clouds can be two orders of magnitude higher than the prediction of the standard gas-phase models which, in turn, predict rather well the abundances of neutral CH. It is therefore necessary to investigate all the possible formation and destruction processes of CH(+) in the interstellar medium with the most abundant species H, H2, and e(-). In this work, we address the destruction process of CH(+) by hydrogen abstraction. We report a new calculation of the low temperature rate coefficients for the abstraction reaction, using accurate time-independent quantum scattering and a new high-level ab initio global potenti…
Size-consistent ab initio calculation of the electric quadrupole moment of Cl2
2003
Abstract The molecular electric quadrupole moment ( Θ ) of Cl 2 has been calculated using SDCI, and (SC) 2 -SDCI wave functions as well as CCSD, CCSD(T), and CC3 methods. All these correlation methods are single reference. All of them, but SDCI, are free of the size-extensivity error. The variation of Θ from the separated atoms to the equilibrium region is reported. The present results leads to an estimated value of 2.3520 a.u. (10.55 × 10 −40 Cm 2 ) corresponding to a CC(3) calculation at the CBS approach and including the ro-vibrational and thermal averaging corrections. This value is compatible with two experimental values and points to one of them as slightly more reliable.
Semi-Empirical Calculations of Hole Polarons in MgO and KNbO3 Crystals
1998
The semi-empirical quantum chemical INDO method has been used for cluster and large unit cell calculations of hole polarons bound to a cation vacancy in highly ionic MgO and partly covalent perovskite KNbO 3 . In both cases a hole is well localized on an oxygen atom displaced towards the vacancy. The calculated optical and thermal ionization energies for V - and V 0 centers are in excellent agreement with experimental data for MgO. In KNbO 3 we predict the existence of one-site and two-site (molecular) polarons with close absorption energies (1 e V). The relevant experimental data are discussed.
Asymptotic potentials and rate constants in the adiabatic capture centrifugal sudden approximation for X + OH(X-2 Pi) -> OX + H(S-2) reactions where …
2012
International audience; New long-range multipolar coefficients for the X + OH(X-2 Pi) interactions, where X = O(P-3), S(P-3) and N(S-4), are given here. They have been evaluated on the basis or monomer properties of the atoms and OH such as the dipole and quadrupole moments, and the static and dynamic polarizabilities. Each matrix element of the 18 x 18 (8 x 8 for N + OH) quasi-degenerate asymptotic potentials has been built up by means of the perturbation theory up to second order including or not the fine-structure of O, S and OH. The adiabatic potentials, obtained after diagonalization of the full matrix, show many crossings and complex behaviors near the asymptotes. Using the entrance c…
Study of the electronic and atomic structure of thermally treated SrTiO3(110) surfaces
2003
The electronic structure of heated SrTiO3(110) surfaces was investigated with metastable impact electron spectroscopy and ultraviolet photoelectron spectroscopy (He(I). Scanning tunnelling microscopy and atomic force microscopy (AFM) were used to study the topology of the surface. The crystals were heated up to 1000 °C under reducing conditions in ultrahigh vacuum or under oxidizing conditions in synthetic air for 1 h, respectively. Under both conditions microfacetting of the surface is observed. The experimental results are compared with ab initio Hartree-Fock calculations, also presented here, carried out for both ideal and reconstructed SrTiO 3(110) surfaces. The results give direct evid…
Theoretical study of the NH tautomerism in free base porphyrin
1997
Abstract The NH tautomerism of free base porphyrin is investigated at the semiempirical spin-unrestricted AM1 (UAM1) and ab initio RHF/3-21G levels. The UAM1 method provides delocalized geometries for all stationary structures without imposing any symmetry constraint. RHF/3-21G geometry optimizations have to be performed under symmetry restrictions to ensure that realistic delocalized structures are obtained. Both the semiempirical and the ab initio calculations predict that the interconversion between trans tautomers proceeds in an asynchronous two-step process via intermediate cis tautomers. The cis tautomers are characterized as minima in the potential energy surface and are 8–10 kcal m…
InBO3 and ScBO3 at high pressures: an ab initio study of elastic and thermodynamic properties
2016
We have theoretically investigated the elastic properties of calcite-type orthoborates ABO(3) (A= Sc and In) at high pressure by means of ab initio total-energy calculations. From the elastic stiffness coefficients, we have obtained the elastic moduli (B, G and E), Poisson's ratio (nu), B/G ratio, universal elastic anisotropy index (A(U)), Vickers hardness, and sound wave velocities for both orthoborates. Our simulations show that both borates are more resistive to volume compression than to shear deformation (B > G). Both compounds are ductile and become more ductile, with an increasing elastic anisotropy, as pressure increases. We have also calculated some thermodynamic properties, like D…