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991.
María Inés Frascaroli Juan Manuel Salas-Peregrin Luis F. Sala Sandra Signorella 《Polyhedron》2009,28(6):1049-1056
The oxidation of 3-O-methyl-d-glucopyranose (Glc3Me) by CrVI in acid medium yields CrIII, formic acid and 2-O-methyl-d-arabinose as final products when a 50-times or higher excess of Glc3Me over CrVI is used. The redox reaction takes place through the combination of CrVI → CrIV → CrII and CrVI → CrIV → CrIII pathways. Intermediacy of free radicals and CrII in the reaction was demonstrated by the observation of induced polymerization of acrylamide and detection of CrO22+ formed by reaction of CrII with O2. Intermediate oxo-CrV–Glc3Me species were detected by EPR spectroscopy. In 0.3–0.5 mol/L HClO4, intermediate CrV rapidly decompose to the reaction products, while, at pH 5.5–7.5, where the redox processes are very slow, five-coordinate CrV bis-chelates of the pyranose and furanose forms of Glc3Me remain more than 15 h in solution. The C1–C2 bond cleavage of Glc3Me upon reaction with CrVI distinguishes this derivative from glucose, which is oxidized to gluconic acid. 相似文献
992.
Francisco J. Jiménez‐Hornero Juan V. Giráldez Ana M. Laguna Sean J. Bennett Carlos V. Alonso 《国际流体数值方法杂志》2007,55(7):655-672
A two‐dimensional lattice model has been developed to describe the influence of vegetation on the turbulent flow structure in an open channel. The model includes the influence of vegetation density on the frictional effect of the channel bed and walls. For the walls, a semi‐slip boundary condition has been considered as an alternative to overcome the no‐slip boundary condition limitations in turbulent flows. The drag stress exerted by the flow on the vegetation as well as the gravity effect has also been taken into account. The proposed lattice model has been used to simulate the experimental results reported from the study of the influence of alternate vegetated zones on the open‐channel flow. The results show that the lattice model approach is a valid tool for describing these kinds of flows. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
993.
一类量子环面李代数的自同构群 总被引:3,自引:0,他引:3
=C_q[x_1~(±1),x_2~(±1)]为复数域上的非交换环面结合代数,A=\C,Der为的导子李代数.本文研究李代数L_q=DerA的自同构群Aut L_q. 相似文献
994.
该文研究带耗散项的线性和半线性波动方程外问题. 首先利用一个Sobolev型不等式得到了线性耗散波动方程在外区域上的整体能量衰减估计, 此结果用来证明非线性项为|u|p (2
+) 的半线性波动方程解的整体存在性. 为此, 该文主要研究N维(3≤ N≤7)外区域上球对称解的情形. 相似文献
995.
The line-integrated optical measurement of impurity radiation profiles for the study of light impurity transport is performed in the HT-7 tokamak. The carbon impurity line emissivity is obtained by Abel inversion. The radial transport behaviours of carbon impurities at different central line averaged electron densities ne are investigated in ohmic discharges. The diffusion coefficient Dk(r), the convection velocity Wk(r) and the total flux of the impurity ions Fk decrease with the increase of ne, which shows a reduction in the impurity particle transport at higher electron densities. 相似文献
996.
Juan F. García‐Reyes Fabio Mazzoti Jason D. Harper Nicholas A. Charipar Sheran Oradu Zheng Ouyang Giovanni Sindona R. Graham Cooks 《Rapid communications in mass spectrometry : RCM》2009,23(19):3057-3062
A fast, reagentless, and direct method is presented for the mass spectrometric analysis of olive oil without any sample pretreatment whatsoever. An ambient ionization technique, the low‐temperature plasma (LTP) probe, based on dielectric barrier discharge, is used to detect both minor and trace components (free fatty acids, phenolics and volatiles) in raw untreated olive oil. The method allows the measurement of free fatty acids (the main quality control parameter used to grade olive oil according to quality classes), selected bioactive phenolic compounds, and volatiles. The advantages and limitations of the direct analysis of extremely complex mixtures by the ambient ionization/tandem mass spectrometry combination are discussed and illustrated. The data presage the possible large‐scale application of direct mass spectrometric analysis methods in the characterization of olive oil and other foodstuffs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
It is shown that the F
4 rational and trigonometric integrable systems are exactly solvable for arbitrary values of the coupling constants. Their spectra are found explicitly while eigenfunctions are obtained by pure algebraic means. For both systems new variables are introduced in which the Hamiltonian has an algebraic form being also (block)-triangular. These variables are a certain invariants of the F
4 Weyl group. Both Hamiltonians preserve the same (minimal) flag of spaces of polynomials, which is found explicitly. 相似文献
998.
The shape and diffraction pattern of a liquid crystal display (LCD) pixel used in a point-diffraction interferometer is qualitatively evaluated using the experimental diffraction patterns of computer-generated apertures. The diffraction patterns for apertures with contours between a circle and a square were numerically plotted from analytical expressions of these topological forms. The observed patterns are qualitatively in accordance with previous calculations of such apertures using scalar diffraction theory in the far field. 相似文献
999.
Tao Xu Chun-Yi Zhang Guang-Mei Wei Juan Li Xiang-Hua Meng Bo Tian 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):323-332
Currently, the variable-coefficient nonlinear Schr?dinger
(NLS)-typed models have attracted considerable attention in such
fields as plasma physics, nonlinear optics, arterial mechanics and
Bose-Einstein condensates. Motivated by the recent work of Tian et
al. [Eur. Phys. J. B 47, 329 (2005)], this paper is devoted to
finding all the cases for a more generalized NLS equation with
time- and space-dependent coefficients to be mapped onto the
standard one. With the computerized symbolic computation, three
transformations and relevant constraint conditions on the
coefficient functions are obtained, which turn out to be more
general than those previously published in the literature. Via
these transformations, the Lax pairs are also derived under the
corresponding conditions. For physical applications, our
transformations provide the feasibility for more
currently-important inhomogeneous NLS models to be transformed
into the homogeneous one. Applications of those transformations to
several example models are illustrated and some soliton-like
solutions are also graphically discussed. 相似文献
1000.