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91.
92.
Complex formation in zinc(II) meso-nitro-octa-ethylporphyrin (1) and the corresponding α,β-dinitro (2) and α, γ-dinitro (3) zinc(II) chelates has been studied using proton NMR at 220MHz. This allows complete resolution of all the distinct groups in the proton spectrum, and the large concentration dependence of the spectra of 1 and 2 can be analysed to afford the monomeric and monomer-dimer shifts for all protons in these molecules. In contrast 3 shows no concentration dependence, nor any change upon addition of pyrrolidine, which immediately dissociates the aggregates of 1 and 2. The monomeric 1H and 13C shifts are reported, together with those of zinc(II) octaethylporphyrin (4), and the complete assignment given allows the substituent shifts of the meso nitro groups in the porphyrin to be obtained. Analysis of the monomer-dimer shifts in terms of the ring current model gives the detailed geometries of the dimers, which have an inter-ring separation of ca 4.5 Å and a lateral displacement from the vertical of ca 1.0 Å. The results also allow the distinction between two different molecular complexes considered previously, and fully confirm our earlier suggestions that binding is due to metal-to-porphyrin, rather than metal-to-substituent, interactions. 相似文献
93.
灰竹挥发油化学成分分析 总被引:5,自引:0,他引:5
用溶剂提取法提取了灰竹的挥发性物质,用GC-MS法鉴定出22种化合物,其中主要成分(相对含量)为烯类(19.0%),醇类(39.9%),酯类(1.0%)、酸类(10.9%),酮类(2.3%)、芳香烃类(19.8%)和烷烃类(3.6%)化合物,占总检出量约97%。 相似文献
94.
桔梗等中药微量元素初探 总被引:5,自引:0,他引:5
对中药桔梗、怀牛膝,华山参、鹿角胶,龟甲胶及阿胶进行了微量元素研究。结果发现:同一种中药因产地不同,其微量元素的含量不同。同一种植物药,其部位不同,所含微量元素多少不等。同一类型的中药,其品种、来源不同,微量元素的含量高低也不相同。本研究为今后对这些中药进行真伪鉴别,合理开发或综合利用都提供了科学的依据。 相似文献
95.
Viatcheslav V. Kolmychkov Olga S. Mazhorova Yurii P. Popov Patrick Bontoux Mohammed El Ganaoui 《Comptes Rendus Mecanique》2005,333(10):739-745
Three-dimensional calculations have been done to simulate the onset of convective motion in ternary nondilute solution under phase transition conditions. The process is considered for Rayleigh number in the range , where subcritical convective motion with hexagonal flow pattern is identified. The results are in good agreement with the linear and finite amplitude theory of hydrodynamics instability. To cite this article: V.V. Kolmychkov et al., C. R. Mecanique 333 (2005). 相似文献
96.
The multiple allocation uncapacitated hub location problem is considered. This problem arises in transportation systems when
several locations send and receive passengers and/or express packages and the performance of these systems can be improved
by using transshipment points (hubs), where the passengers/packages are collected and distributed.
An Integer Programming formulation, the one giving the best computational results until now, serves as a basis for the solution
method. Using the fact that the transportation costs between hubs satisfy the triangle inequality, an analysis of the set
of solutions that are not candidates to be optimal is carried out and, as a consequence, the formulation of the problem can
be strengthened by means of powerful valid inequalities obtained through the study of the intersection graph of an associated
set packing problem. The algorithm developed uses the most promising of these inequalities in a Lagrangian relaxation context
to reduce the size of the branching tree and improve the computational times. This improvement is shown by means of a computational
study, where a set of instances are optimally solved with low computational effort. 相似文献
97.
We deal with the relationship between the spectral radius and the topological bihaviour of the group of invertible elements
in a topological algebra, introducing accordingly several types of (generalized Q-) algebras. We then give properties and
characterizations of such algebras. Applications to weighted algebras as well as several classes of examples are provided.
相似文献
98.
Marie-Paule Pileni 《Chemical physics letters》1980,71(2):317-321
Changes of the surfactant vesicle sizes and of the efficiency of the photoredox reaction between various solubilized Zn porphyrins and duroquinones upon incorporation of the chromophore or upon addition of salts have been examined by quasi-elastic light scattering and laser photolysis techniques. The yields of porphyrin cation and duroqumone anion radicals appear to be independent of the nature of the porphyrin-qumone system. Addition of salts influences both the yield and the ejection of porphyrin cations from the vesicles by screening up the surface charge. 相似文献
99.
M.Habibou Maitournam Benjamin Pommier Jean-Jacques Thomas 《Comptes Rendus Mecanique》2002,330(10):703-708
A method for the solution of cyclic thermomechanical nonlinear problems is presented: it is a Direct Cyclic Method which is an alternative approach to classical methods. It consists in directly seeking the asymptotic response of an inelastic structure subjected to a periodic thermomechanical loading without following the loading path. It is based on the Large Time Increment Method, the periodicity of the limit state and the Fourier transform. To cite this article: M.H. Maitournam et al., C. R. Mecanique 330 (2002) 703–708. 相似文献
100.
F.R. Van Buren G.H.J. Broers A.J. Bouman C. Boesveld 《Journal of Electroanalytical Chemistry》1978,88(3):353-361
Results of an electrochemical method for the determination of oxygen ion diffusion coefficients DO2? in porous pellets of La0.50Sr0.50CoO3?y are presented. Log DO2? can be expressed as log DO2?=?(2.3±0.2) 103/T?(6.6±0.6) cm2 s?1. The activation energy Ea for the diffusion process equals 44 kJ mol?1. Further the related electrochemical measurement and the adjustment of the oxygen deficiency y are described. At 75°C the following empirical Nernst relation between the electrode potential E (vs. a Pt/H2 (1 atm) electrode in the same solution) and Δy is found: E=627–108 ln (Δy + 0.0054) mV. (Δy=y?y0; y0=mole fraction of vacancies at the reversible O2 potential of 1190 mV). The use of La0.50Sr0.50CoO3?y as a solid solution electrode in practical storage cells seems to be excluded for thermodynamic and kinetic reasons. 相似文献