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91.
Jung Sook Ham 《Journal of Mathematical Analysis and Applications》2003,286(1):116-124
Let α≡{αn}n=0∞ be a weight sequence and let Wα denote the associated unilateral weighted shift on . In this paper we prove that if α is eventually increasing, then Wα is M-hyponormal and that if α has exactly two subsequential limits such that the larger one is different from the spectral radius of Wα then Wα is not M-hyponormal. 相似文献
92.
M.I. Yanovskaya N.M. Kotova N.V. Golubko N.YA. Turova 《Journal of Sol-Gel Science and Technology》1998,11(1):23-29
The interaction between magnesium and titanium alkoxides is studied in order to chose the best precursors for synthesis of MgTiO3. No reaction between magnesium and titanium methoxides and isopropoxides occurs. The solubility diagrams for Mg(OR)2-Ti(OR)4-ROH, R = Et,-Bu at 20°C are studied. Magnesium ethoxotitanates of variable composition MgnTi4-n (OEt)16-2n2nEtOH (n=2.0-0) which are structural analogs of Ti4(OR)16 (R = Me, Et) are isolated. This is a quite unusual example of statistical distribution of heteroatoms in molecular structures of metal alkoxides. Among the systems of metal alkoxides with simple aliphatic radicals only Mg(OBu)2-Ti(OBu)4-BuOH gives a convenient precursor for the synthesis of MgTiO3. A simple scheme of preparation of magnesium titanate from the alkoxide solutions is suggested. The phase purity of MgTiO3 is to a considerable extent dependent on the hydrolysis conditions. The alkoxy-derived magnesium titanate is obtained in the form of a uniform fine powder, it can be sintered into dense ceramics in the temperature range of 1140–1220°C which is 150–200°C lower in comparison with the conventional powders. 相似文献
93.
We have discovered a novel, spontaneous model oxidation that leads to a powerful base capable of carrying out a carbon-carbon bond forming condensation reaction analogous to that observed in the vitamin K-mediated carboxylation of glutamate. The model sequence incorporates a novel base-strength enhancement sequence and it implicates molecular oxygen as the initiating factor in the vitamin K-dependent carboxylation. When the oxygenation is carried out under an atmosphere of (18)O2, two atoms of (18)O are incorporated into the vitamin K oxide product. Selective (18)O labelling defines the carbonyl group next to methyl as the active site of the vitamin K. 相似文献
94.
2,3-Disubstituted indoles were synthesized by solid-phase reaction using the Fischer indole synthesis. A "traceless" silicon linker was employed with the silicon-carbon bonding being cleaved with TFA. An oxygen atom was placed into the middle of the spacer/linker so as to enhance solid-phase synthesis by better solvation. 相似文献
95.
96.
A microscopic site binding model to treat binding of several metal ions to multi-center receptors is proposed. The model introduces the appropriate parameterization in terms of microscopic complexation constants and metal-metal pair interaction energies. The model is solved with statistical mechanical techniques, including direct enumeration or transfer matrices. We obtain microscopic and macroscopic complexation constants, microstate probabilities, and binding isotherms for chain-like receptors, including the long-chain limit. Various examples to illustrate the usefulness of the model are given. 相似文献
97.
研究了酚醛型吸附树脂JDW 2在非水体系中对吡啶和N ,N 二甲基苯胺的静态吸附 .由实验结果推论正己烷中树脂对吡啶和N ,N 二甲基苯胺的吸附是以氢键吸附机理为主进行的 ,JDW 2酚醛型吸附树脂在正己烷中 ,等温吸附吡啶和N ,N 二甲基苯胺的平衡吸附数据符合Langmuir方程 ,相关系数在 0 99以上 ,因此 ,酚醛型吸附树脂在正己烷中吸附吡啶和N ,N 二甲基苯胺属单分子层吸附 ;同时对非水体系中乙醇或乙酸乙酯的含量对树脂吸附吡啶和N ,N 二甲基苯胺的影响进行了研究 相似文献
98.
Based on the hydrodynamic model theory and the transfer-matrix-method, we have reexamined the reflection properties by taking account of damping effects to the system of the metallic superlattice for the S-polarized soft X-rays and extreme ultraviolet. Fot the normal incidence, we find that the reflection intensity spectxm will decline monotonously with the increasing of the retardation, but for the regions of the higher frequencies and the smaller grazing angles, the damping effects could be neglected. 相似文献
99.
YoonMee Ham & Sang sup Yum 《偏微分方程(英文版)》1995,8(3):211-218
We consider a free boundary problem in a parabolic partial differential equation with multiple interfacial curves which is reduced to a reaction-diffusion equation. The forcing term of this problem is not continuously differentiable and thus we use Green's function to make a regular one. The existence, uniqueness and dependence. on initial conditions will be shown in this paper. 相似文献
100.
合成了一种有机-无机介孔二氧化硅杂化材料(SBA-15-Tpy),通过透射电镜显微镜、X射线衍射、热重分析和N_2吸附-解吸曲线对其进行表征,并基于该材料建立了在水中对Cu2+和Co2+的选择性识别。研究表明,SBA-15-Tpy与Cu2+和Co2+结合后会分别在800 nm和510 nm处产生新的吸收峰,加入其它金属离子后不发生明显的吸收峰值变化。在最优条件下,检测Cu2+和Co2+的线性范围分别为2.0~200.0μmol/L和10.0~200.0μmol/L,检出限分别为0.48μmol/L和4.28μmol/L。将上述方法用于江水中Cu2+和Co2+的测定,回收率在96.0%~108.5%之间。 相似文献