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171.
Jos C.A. de Pontes Antonio M. Batista Ricardo L. Viana Sergio R. Lopes 《Chaos, solitons, and fractals》2005,23(5):1689-1694
We investigate short-term memories in linear and weakly nonlinear coupled map lattices with a periodic external input. We use locally coupled maps to present numerical results about short-term memory formation adding a stochastic perturbation in the maps and in the external input. 相似文献
172.
W. Ryba-Romanowski M. Berkowski B. Viana P. Aschehoug 《Applied physics. B, Lasers and optics》1997,64(5):525-529
3 H4 and 3F4 states of Tm in SrGdGa3O7 single crystal was evaluated. Tm-Tb energy transfer reduces effectively the lifetime of terminal level in a potential 3H4-3F4 laser transition but gives rise to parasitic nonradiative relaxation of the initial 3H4 level. SrGdGa3O7 crystal single doped with thulium possesses combination of properties advantageous for laser oscillations near 1.9 μm, namely
high rate of cross relaxation process leading to population buildup on the initial 3F4 level and relatively high crystal field splitting of the ground 3H6 level.
Received: 25 April 1996/Revised version: 10 October 1996 相似文献
173.
We prove the Zorich–Kontsevich conjecture that the non-trivial Lyapunov exponents of the Teichmüller ow on (any connected
component of a stratum of) the moduli space of Abelian differentials on compact Riemann surfaces are all distinct. By previous
work of Zorich and Kontsevich, this implies the existence of the complete asymptotic Lagrangian flag describing the behavior
in homology of the vertical foliation in a typical translation surface.
Work carried out within the Brazil–France Agreement in Mathematics. Avila is a Clay Research Fellow. Viana is partially supported
by Pronex and Faperj. 相似文献
174.
Te-Butyl Telluroesters and Se-Butyl Selenoesters are hydrolyzed to carboxylic acids under very mild conditions by reaction with copper(II) chloride dihydrate. When the reaction is performed in ethanol or methanol, using anhydrous copper(II) chloride a transesterification occurred leading to the oxygenated esters in good yield. 相似文献
175.
Ytterbium ions infrared and visible cooperative luminescences, resulting from YAG laser and selective site excitations, in (6%) Yb-doped Y2SiO5 thin film are analyzed. Magnetically coupled Yb-Yb ion pairs seem to play a major role in energy transfer and cooperative emission, confirming the prevalence of superexchange mechanisms. 相似文献
176.
Jaime E. A. Rodriguez Oscar Paz la Torre Renato Vidal Martins Paulo Henrique Viana 《Bulletin of the Brazilian Mathematical Society》2008,39(1):137-155
We study curves of genus 3 over algebraically closed fields of characteristic 2 with the canonical theta characteristic totally
supported in one point. We compute the moduli dimension of such curves and focus on some of them which have two Weierstrass
points with Weierstrass directions towards the support of the theta characteristic. We answer questions related to order sequence
and Weierstrass weight of Weierstrass points and the existence of other Weierstrass points with similar properties.
– Dedicated to the treasured memory of our coauthor, Paulo Henrique Viana 相似文献
177.
Ramos JM Viana RM Téllez S CA Pereira WC Izolani AO da Silva MI 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(2):433-438
To elucidate tentative assignments of metal-ligand modes of thiosemicarbazide complexes, a structural study and a assignment of the normal vibrations of 2-methylthiosemicarbazide copper(II) nitrate, [Cu(2MeTSC)(2)(NO(3))(2)] have been done through the ab initio DFT: pBP86/DN** procedure, and through the normal coordinate analysis (NCA). In the vibrational calculations, the elongated CuONO(2) bonds of the nitrate groups were considered in the CS and CN tautomers of the complex. DFT calculations had revealed that the infrared spectra can be well interpreted through the CN tautomer, failing in the prediction of the -NO(2) group wavenumbers. A little difference stabilization energy for the tautomers were found: for the CN tautomer was E=-3487,36376a.u., and for the CS tautomer, E=-3473,93598a.u. The observed combination bands at 1763.0 and at 1754.0 cm(-1) are an indicative that the -NO(3)(-) groups acts as monodentate ligands. Calculations had confirmed the experimental assignment of the infrared spectrum. 相似文献
178.
Rajia Ait Benhamou Aurlie Bessire Gilles Wallez Bruno Viana Mohamed Elaatmani Mohamed Daoud Abdelwahed Zegzouti 《Journal of solid state chemistry》2009,182(8):2319-2325
The double phosphate Ca9Eu(PO4)7, obtained by solid state reaction, was found to be isotypic with Ca3(PO4)2, with space group R3c and unit cell parameters a=10.4546(1) Å, c=37.4050(3) Å, V=3540.67(9) Å3, Z=6. The structure parameters refined using the Rietveld method showed that europium shares positions M1, M2 and M3 with calcium, contradicting previously published Mössbauer results. Low temperature luminescence under selective excitation of Eu3+ in Ca9Y1−xEux(PO4)7 and in Ca9Eu(PO4)7 samples was studied, confirming the Eu3+ distribution into these sites. At 10 K, 5D0→7F0 emission lines of Eu3+ were observed at 578.5, 579.5, 580.1 nm for the M3, M1 and M2 sites, respectively. High temperature X-ray powder diffraction evidenced a second-order phase transition around 573 °C. 相似文献
179.
This work discusses the entanglement and quantum polarization of superpositions of two-mode coherent states of the types |ψ1〉 = N1(|α, β〉 + |β, α〉) and |ψ2〉 = N2(|−α, −α〉 + |α, α〉). We use the concurrence to measure their entanglements and the quantum Stokes parameters and the Q function in order to analyze their polarization and degree of polarization. 相似文献
180.
Manoel Carvalho Castro Edson Firmino Viana Carvalho Waldeci Paraguassu Alejandro Pedro Ayala Frank C. Snyder Michael W. Lufaso Carlos William de Araujo Paschoal 《Journal of Raman spectroscopy : JRS》2009,40(9):1205-1210
In this work, we have performed Raman scattering measurements in Ba2BiSbO6 ceramics in the temperature range from 10 to 573 K. The Raman spectra were examined using group theory to analyze the decomposition of the reducible representation of the vibrational modes and with a virtual octahedral model. At room temperature, five modes were observed. At low temperatures, the spectra subtly showed the rhombohedral–monoclinic phase transition, which was identified by changes in the Raman intensity of the bending and symmetrical stretching SbO6 octahedral modes. The cubic–rhombohedral phase transition was not clearly evident in the high‐temperature Raman data. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献