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Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献
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R. Navarrete Casas A. García Rodríguez F. Rey Bueno A. Espínola Lara C. Valenzuela Calahorro A. Navarrete Guijosa 《Applied Surface Science》2006,252(17):6026-6030
In the present work, we have studied the adsorption of xanthine derivatives by activated carbon sorbents in aqueous solutions. The study comprised both kinetic, equilibrium and thermodynamic aspects. The kinetic results were reported in a previous paper; the equilibrium-related results are discussed here. The two types of carbon used exhibit some differences but the equilibrium isotherms obtained are all of the H-3 type in the classification of Giles. This suggests a high affinity of the sorbents for the sorbates. We also found that the overall adsorption process comprises more than one individual adsorption-desorption process of which one leads to the formation of a “monolayer” and the other to the “precipitation” of the sorbate on the sorbent surface (multilayer adsorption); the amount of sorbate adsorbed in monolayer form was seemingly greater in C-A14. 相似文献
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Spin density redistribution between the paramagnetic centers Cu2+, N-O, and N’-O’ of bischelate complexes CuL2 of the copper ion with enaminoketone 3-imidazoline nitroxides (L) are investigated using an ab initio RHF (restricted Hartree-Fock)
approach. The most important channels of unpaired electron delocalization over the systems of π- and Σ-bonds in such complexes
are revealed. The conformation dependence of spin density localized on paramagnetic centers and delocalized due to a distortion
of the structure of the environment of the Cu2+ ion from square planar to tetrahedral is analyzed and explained.
Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 5, pp. 840–849, September-October, 1997. 相似文献
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Gosse C Boutorine A Aujard I Chami M Kononov A Cogné-Laage E Allemand JF Li J Jullien L 《The journal of physical chemistry. B》2004,108(20):6485-6497
This report examines the organization properties of new fluorescent DNA-lipids, either alone in water or in interaction with 1-octyl-beta-d-glucopyranoside micelles or egg phosphatidylcholine vesicles. We first describe the design and the syntheses of the conjugates. Then, we use UV-Vis absorption, steady-state fluorescence emission, electron microscopy, and fluorescence correlation spectroscopy after two-photon excitation to show that these DNA-lipids form spherical micelles in aqueous solution and incorporate much better in micelles than in vesicles. We also investigate the significance of the lipophilic chains of these DNA-lipids on the melting behavior of the double-stranded hybrids: in water melting curves are broadened whereas in amphiphilic assemblies duplexes melt as the unconjugated controls. This work is expected to be useful for improving the rational design of antisense medicines. 相似文献
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J. L. Gascón M. Rodríguez J. A. Suárez Del Rey 《Journal of Radioanalytical and Nuclear Chemistry》1996,207(1):63-69
The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates. 相似文献
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Barthez J.M. Molino F. Marignan J. Ayral A. Guizard C. Jullien R. 《Journal of Sol-Gel Science and Technology》1997,8(1-3):83-88
We present here an experimental and numerical study of the chemical and aggregative mechanisms for titanium alkoxide in a
reverse micellar medium. NMR experiments were done to study the first step of the sol-gel process: hydrolysis of titanium
isopropoxide. Light and X-ray scattering experiments were then conducted to characterize the clustering of aggregates and
aggregation kinetics. Fractal dimension, measured by U.S.A.X.S., varies with the hydrolysis ratio and the hydration of the
surfactant. This evolution was explained by polydispersity of the hydrolysis which depends on the surfactant concentration.
This hypothesis was tested through a numerical simulation of irreversible aggregation using a chemically limited aggregation
model. The hydrolyzed sites are distributed among the monomers by a random procedure governed by a polydispersity parameterp, varying from 0 to 1. The total number of hydrolyzed sites is governed by a parameterq belonging to the interval [0, 1]. Thep-q evolution of the fractal dimension coincides rather well with the experimental data in all the region of the two dimensional
phase space. 相似文献