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111.
We find an integrable generalization of the BCS model with nonuniform Coulomb and pairing interaction. The Hamiltonian is integrable by construction since it is a functional of commuting operators; these operators, which therefore are constants of motion of the model, contain the anisotropic Gaudin Hamiltonians. The exact solution is obtained diagonalizing them by means of Bethe ansatz. Uniform pairing and Coulomb interaction are obtained as the "isotropic limit" of the Gaudin Hamiltonians. We discuss possible applications of this model to a single grain and to a system of few interacting grains. 相似文献
112.
The effect of time-correlated and white Gaussian noises of low intensity on one-dimensional arrays consisting of diffusively coupled chaotic cells is analyzed. An improvement or worsening of the synchronization between cells of the array driven by low-intensity colored noise is observed for a resonant interval of time correlation values. A comparison between colored and white noise and additive and multiplicative contribution has been carried out investigating the nonlinear cooperative effects of noise strength, correlation time, and coupling strength to control spatiotemporal chaos in coupled arrays of chaotic cells. The possibility to distinguish highly correlated areas of a diffusively coupled network of cells by using low-intensity time correlated noise is discussed. (c) 2001 American Institute of Physics. 相似文献
113.
Stanislaw Dzwigaj Lorenzo Stievano Michel Che 《Journal of Physics and Chemistry of Solids》2007,68(10):1885-1891
Fe-containing SiBEA zeolites were prepared by a two-step postsynthesis method: creation of vacant T-sites by dealumination of tetraethylammonium BEA zeolite with nitric acid and then impregnation of the resulting SiBEA zeolite with an aqueous solution of Fe(NO3)3. X-ray diffraction shows that iron is incorporated in SiBEA at lattice sites. The presence of Fe in its oxidation state +3 and at isolated tetrahedral sites for low metal content, was demonstrated by diffuse reflectance UV-vis, EPR and Mössbauer spectroscopy. For high iron content, diffuse reflectance UV-vis and Mössbauer spectra revealed the additional presence of extra-lattice FeOx oligomers and superparamagnetic Fe-oxyhydroxide. Mössbauer spectroscopy identified superparamagnetic Fe-oxyhydroxide as the main phase when basic conditions are used for the preparation. 相似文献
114.
A simple HPLC method for vitamin E (alpha-tocopherol) measurement in the leaves of Rosmarinus officinalis has been developed and validated. It has enabled new data for alpha-tocopherol content to be established. The leaves, recently harvested, were dried in a microwave oven and crushed; then, alpha-tocopherol was directly extracted from portions of ground material with acetone, by probe sonication. After centrifugation the acetonic extract was analysed by HPLC with ergocalciferol (vitamin D2) added as internal standard and a gradient elution with a Nucleosil C18 column at 35 degrees C. Validation parameters of the method can be considered adequate. For standards: linearity is r=0.999, recovery is 100+/-2%, intra-assay precision has RSD=+/-3% and inter-assay precision has RSD=+/-6%. For samples: linearity is r=0.99, recovery: 93+/-7%, intra-assay precision has RSD=+/-4% and inter-assay precision has RSD=+/-7%. 相似文献
115.
Leonardo C. Ferreira Carlos A. L. Filgueiras Lorenzo C. Visentin Jairo Bordinho Manfredo Hrner 《无机化学与普通化学杂志》2008,634(11):1896-1900
The preparation and characterization of two novel HgCl2 and Hg(SCN)2 complexes with bis[N‐(2‐tert‐butylphenyl)imine]acenaphthene is here described. One‐pot reaction techniques were used, leading to high yields of 75 % and 81 %, respectively. The complexes were characterized by microanalysis, i.r. and 1HNMR spectroscopy, and by single crystal X‐ray diffraction. The structures of the complexes present similar characteristics, the most outstanding being the formation of dimers via intermolecular interaction. Whereas the HgCl2 complex shows a unidimensional network due to strong π–π interactions, its Hg(SCN)2 counterpart displays a supramolecular arrangement resulting from non classical hydrogen bond formation. 相似文献
116.
Pietro Baraldi Gian Carlo Franchini Andrea Marchetti Gavino Sanna Lorenzo Tassi Alessandro Ulrici Giulia Vaccari 《Journal of solution chemistry》2000,29(5):489-504
Thermodynamic interactions in the ethane-1,2-diol (1) + 1,2-dimethoxyethane(2) + water (3) ternary system have been investigated in terms of the excessmolar volume, derived from density measurements at 19 different temperaturesfrom –10;dg to 80;dgC. Fourteen three-component mixtures have been considered,covering the entire composition range. The excess molar volumes are discussedin terms of conformational changes induced in each component by the presenceof another one. The results obtained support the hypothesis of the absence of anythree-component complex adducts under all experimental conditions investigated. 相似文献
117.
A. Viña Orjales M. I. Turnes Carou M. C. Prieto Blanco P. López Mahía S. Muniategui Lorenzo D. Prada Rodríguez 《Chromatographia》2000,51(1-2):77-82
Summary A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best
possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by
capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the
addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV
and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each
compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated
achieving a tenfold enrichment factor and quantitation limits about 10−7M. 相似文献
118.
Controlled adsorptive accumulation at the hanging mercury drop electrode enables 0.8–11 × 10?5 M chlordiazepoxide to be quantified by differential-pulse stripping voltammetry with accumulation times of 1–3 min. With 3-min accumulation, the peak current is enhanced 12-fold for 1.0 × 10?7 M chlordiazepoxide compared to the current from differential pulse polarography. The detection limit is 0.9 × 10?9 M for 4-min accumulation. The procedure is applied to spiked human serum after preseparation of the drug on a Sep-Pak C18 cartridge. 相似文献
119.
M R Iesce F Cermola F De Lorenzo I Orabona M L Graziano 《The Journal of organic chemistry》2001,66(13):4732-4735
120.
A pulsed hard X-ray source with shot to shot reproducible spectrum, based on a 4.7 kJ small-chamber Mather-type plasma focus device, is presented. The hard X-ray output spectrum was measured in a single shot basis by differential absorption on metallic plates. The measured spectra have a single dominant peak around 75 keV and a spectral bandwidth covering the 40-150 keV range. A hard X-ray dose of (53±3) μGy per shot was measured on axis at 53 cm from the source, and found to be uniform within a half aperture angle of 6°. 相似文献