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71.
M. Melo O. Frazão A.L.J. Teixeira L.A. Gomes J.R. Ferreira da Rocha H.M. Salgado 《Applied physics. B, Lasers and optics》2003,77(1):139-142
In this paper, we present a continuous-wave tunable fibre ring laser operating in the L-band. A bi-directional pumped L-band erbium-doped fibre amplifier provides gain to the loop. Tunability is achieved by bending a single-mode fibre taper using a micrometer drive, controlling in this way the spectral cavity losses. Laser emission is achieved between 1587 and 1606 nm, and low variation of the output laser power is observed over all the tuning range. PACS 42.55.Wd; 42.60.Da 相似文献
72.
Malachias A Kycia S Medeiros-Ribeiro G Magalhães-Paniago R Kamins TI Williams RS 《Physical review letters》2003,91(17):176101
Three-dimensional composition maps of nominally pure Ge domes grown on Si(001) at 600 degrees C were obtained from grazing incidence anomalous x-ray scattering data at the Ge K edge. The data were analyzed in terms of a stack of layers with laterally varying concentration. The results demonstrated that the domes contained a Si-rich core covered by a Ge-rich shell and were independently supported by selective etch experiments. The composition profile resulted from substrate Si alloying into the Ge during growth to partially relax the stress in and under the domes. 相似文献
73.
A conjecture stated by Raychaudhuri which claims that the only physical perfect fluid non-rotating non-singular cosmological models are comprised in the Ruiz–Senovilla and Fernández–Jambrina families is shown to be incorrect. An explicit counterexample is provided and the failure of the argument leading to the result is explicitly pointed out. 相似文献
74.
M. Jubera J. Villarroel A. García-Caba?es M. Carrascosa J. Olivares F. Agullo-López A. Méndez J. B. Ramiro 《Applied physics. B, Lasers and optics》2012,107(1):157-162
The propagation losses (PL) of lithium niobate optical planar waveguides fabricated by swift heavy-ion irradiation (SHI),
an alternative to conventional ion implantation, have been investigated and optimized. For waveguide fabrication, congruently
melting LiNbO3 substrates were irradiated with F ions at 20 MeV or 30 MeV and fluences in the range 1013–1014 cm−2. The influence of the temperature and time of post-irradiation annealing treatments has been systematically studied. Optimum
propagation losses lower than 0.5 dB/cm have been obtained for both TE and TM modes, after a two-stage annealing treatment
at 350 and 375∘C. Possible loss mechanisms are discussed. 相似文献
75.
The study of thermodynamic properties of solutions provides important information on existing molecular interactions between the components present in a solution. These studies are critical for testing, validation and development of theories and mathematical models. The refractometric study of a solution is a simple assessment that can contribute to the understanding of these interactions. In this context, the behaviour of the binary water and glucose mixture was studied as well as ternary mixtures of water, glucose and acetonitrile at five different temperatures in the range 293–333 K by the determination of the refractive index of the solution. Due to the weakening of the molecular interactions with the increasing of the temperature, a decreasing dependence of refractive index with temperature was observed. The addition of acetonitrile provides an increase in the refractive index indicating the formation of clusters in the solution. 相似文献
76.
The MReaDy program was designed for studying Multiprocess Reactive Dynamic systems, that is, complex chemical systems involving different and concurrent reactions. It builds a global potential energy surface integrating a variety of potential energy surfaces, each one of them representing an elementary reaction expected to play a role in the chemical process. For each elementary reaction, energy continuity problems may happen in the transition between potential energy surfaces due to differences in the functional form for each of the fragments, especially if built by different authors. A N‐dimensional switch function is introduced in MReaDy in order to overcome such a problem. As an example, results of a collision trajectory calculation for H2 + OH → H3O are presented, showing smooth transition in the potential energy, leading to conservation in the total energy. Calculations for a hydrogen combustion system from 1000 K up to 4000 K shows a variation of 0.012% when compared to the total energy of the system. © 2016 Wiley Periodicals, Inc. 相似文献
77.
César O. Avellaneda Karim Dahmouche Luis O.S. Bulhões Agnieszka Pawlicka 《Journal of Sol-Gel Science and Technology》2000,19(1-3):447-451
Electrochemical lithium intercalation in thin films of CeO2-TiO2 and WO3, prepared by the sol-gel technique was investigated with cyclic voltammetry and spectroelectrochemical techniques in propylene carbonate solutions. A solid state system having the configuration WO3/Ormolyte/CeO2-TiO2 has been assembled. The solid electrolyte, an organically modified electrolyte (ormolyte), was prepared with different [O]/[Li] ratios. The transmittance variation of this system during a potentiostatic step from –0.7 V to 0.8 V was about 35% at 550 nm. 相似文献
78.
Mohallem JR Coura Tde O Diniz LG de Castro G Assafrão D Heine T 《The journal of physical chemistry. A》2008,112(38):8896-8901
The adiabatic finite-nuclear-mass-correction (FNMC) to the electronic energies and wave functions of atoms and molecules is formulated for density-functional theory and implemented in the deMon code. The approach is tested for a series of local and gradient corrected density functionals, using MP2 results and diagonal-Born-Oppenheimer corrections from the literature for comparison. In the evaluation of absolute energy corrections of nonorganic molecules the LDA PZ81 functional works surprisingly better than the others. For organic molecules the GGA BLYP functional has the best performance. FNMC with GGA functionals, mainly BLYP, show a good performance in the evaluation of relative corrections, except for nonorganic molecules containing H atoms. The PW86 functional stands out with the best evaluation of the barrier of linearity of H2O and the isotopic dipole moment of HDO. In general, DFT functionals display an accuracy superior than the common belief and because the corrections are based on a change of the electronic kinetic energy they are here ranked in a new appropriate way. The approach is applied to obtain the adiabatic correction for full atomization of alcanes C(n)H(2n+2), n = 4-10. The barrier of 1 mHartree is approached for adiabatic corrections, justifying its insertion into DFT. 相似文献
79.
Determination of carbosulfan and its metabolites in oranges by liquid chromatography ion-trap triple-stage mass spectrometry 总被引:1,自引:0,他引:1
Liquid chromatography ion-trap mass spectrometry LC-MSn has been successfully applied to identify and confirm carbosulfan and seven of its metabolites in oranges after pressurized liquid extraction (PLE) with dichloromethane. Mass spectra of carbosulfan and its metabolites were investigated using multiple stages of mass spectrometry. Although interpretation of the fragmentation pathways, based on mass spectra, enables structural elucidation and identification of these compounds, the proposed fragmentation pathways and ion structures need verification by exact mass measurements. The analytical method--PLE and LC-MS3 --was validated: limits of quantification (LOQ) ranged from 0.01 to 0.07 mg kg(-1); at this level, recoveries were 55-90% with RSDs (five replicate analyses) from 8 to 19%. The degradation of carbosulfan was determined in a laboratory study carried out in mature oranges (Valencia Late) and tangerines (Clementine of Nules) already harvested. Main degradation products of carbosulfan were carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran and dibutylamine. 相似文献
80.
Brandão GP de Campos RC Luna AS de Castro EV de Jesus HC 《Analytical and bioanalytical chemistry》2006,385(8):1562-1569
A procedure for the determination of As in diesel, gasoline and naphtha at μg L−1 levels by GFAAS is proposed. Sample stabilization was achieved by the formation of three component solutions prepared by
mixing appropriate volumes of the samples propan-1-ol and nitric acid aqueous solution. This mixture resulted in a one-phase
medium, which was indefinitely stable. No changes in the analyte signals were observed over several days in spiked samples,
proving long-term stabilization ability. The use of conventional (Pd) and permanent (Ir) modification was investigated and
the former was preferred. Central composite design multivariate optimization defined the optimum microemulsion composition
as well as the temperature program. In this way, calibration using aqueous analytical solutions was possible, since the same
sensitivity was observed in the investigated microemulsion media and in 0.2% v/v HNO3. Coefficients of correlation larger than 0.999 and an As characteristic mass of 22 pg were observed. Recoveries (n=4) obtained from spiked samples were 98±4, 99±3 and 103±5%, and the limits of detection in the original samples were 1.8,
1.2 and 1.5 μg L−1 for diesel, gasoline and naphtha, respectively. Validation was performed by the analysis of a set of commercial samples by
independent comparative procedures. No significant difference (Student’s t-test, p<0.05) was observed between comparative and proposed procedure results. The total determination cycle lasted 4 min for diesel
and 3 min for gasoline and naphtha, equivalent to a sample throughput of 7 h−1 for diesel and 10 h−1 for gasoline and naphtha. 相似文献