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51.
本文研究如下一种场站设置问题:设S是欧空间E~m中由有限个点A_1,A_2,…,A_n组成的集合.d(A_i,A_j)表示点A_i和A_j之间的距离.令σ(S)=Σ_(1≤i相似文献
52.
采用传统提拉法单晶生长技术成功生长出了Cr,Mg:GSGG晶体, 并对生长出的晶体样品进行了氧化气氛和还原气氛退火处理. 通过对比分析退火处理前后样品吸收光谱的变化, 推断出晶体中四面体配位Cr4+离子的形成机理为: 晶体生长和高温氧化气氛退火的过程中, 四价Cr4+离子首先在八面体格位上形成, 然后在热激发作用下与邻近四面体格位上的Ga3+离子发生置换反应, 从而形成一定浓度的四面体配位Cr4+离子. 实验结果还表明, 随着电荷补偿离子Mg2+离子浓度的增大, 更有利于提高四面体配位Cr4+离子的浓度. 相似文献
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54.
The title compound was synthesized by reaction of Cu(ClO4)2, picolinic acid and carbamide in C2H5OH/CH3CN solution, and characterized by single-crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a=14.0481(8), b=9.0130(5), c=18.626(1)?, V=2358.3(2)?3, Z=4, Dx=1.771g·cm-3, μ=1.235mm-1 and F(000)=1276. The final R factor is 0.0440 for 1434 observed reflections. The X-ray analysis revealed that the copper(Ⅱ) atom is coordinated by two picolinic ligands in the equatorial plane, while the two oxygen atoms of perchlorate occupy the axial positions of octahedron with lengthened Cu-O distances, resulting in a 4+2 elongated octahedral environment. In the compound, there also exist two protonated carbamide cations for charge balance. CCDC: 195354. 相似文献
55.
An Aluminophosphate Molecular Sieve with 36 Crystallographically Distinct Tetrahedral Sites 下载免费PDF全文
Jun Kyu Lee Alessandro Turrina Liangkui Zhu Seungwan Seo Dr. Daliang Zhang Dr. Paul A. Cox Prof. Paul A. Wright Prof. Shilun Qiu Prof. Suk Bong Hong 《Angewandte Chemie (International ed. in English)》2014,53(29):7480-7483
The structure of the new medium‐pore aluminophosphate molecular sieve PST‐6 is determined by the combined use of rotation electron diffraction tomography, synchrotron X‐ray powder diffraction, and computer modeling. PST‐6 was prepared by calcination of another new aluminophosphate material with an unknown structure synthesized using diethylamine as a structure‐directing agent, which is thought to contain bridging hydroxy groups. PST‐6 has 36 crystallographically distinct tetrahedral sites in the asymmetric unit and is thus crystallographically the most complex zeolitic structure ever solved. 相似文献
56.
利用吡啶吸附-IR,NH3吸附-脱附,原位热重积炭,DSC等技术并结合甲基环己烷(MCH)脱氢活性试验,研究了K2O对工业Pt-Sn/Al2O3催化剂的表面酸性及MCH脱氢稳定性的影响,结果表明,K2O能有效地调变催化剂的表面酸性,降低其表面酸中心特别是强酸中心的数目;MCH脱氢反应的积炭量随K2O含量的增加而减少,但催化剂的高温脱氢稳定性与K2O含量并不完全呈顺变关系,K2O含量应严格控制,当K 相似文献
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58.
Yu. V. Mironov S. F. Solodovnikov V. E. Fedorov Yu. V. Gatilov 《Journal of Structural Chemistry》2004,45(5):874-878
The reaction of a water solution of K4Re6Te8(CN)6 with a solution of Mn(NO3)2 in 0.02M hydrochloric acid in the presence of DMF gave crystals of a cluster rhenium complex [{ Mn(H2O)2(DMF)}2Re6Te8(CN)6]·2H2O. The structure of the compound was determined by single crystal X-ray diffraction (a = 12.6679(9) Å, b = 17.4524(12) Å, c = 9.7882(6) Å, β = 105.570(6)°, V = 2084.6(3) Å3, Z = 2, space group P21/n, R = 0. 0389). In the complex, the [Re6Te8(CN)6]4− cluster anions are linked to Mn2+ cations by the cyanide bridges, the manganese cations being additionally coordinated by the DMF molecule and two water molecules. The neighboring clusters are joined by Re-C-N-Mn bridges into a three-dimensional framework possessing cavities filled with doubly disordered water molecules.Original Russian Text Copyright © 2004 by Yu. V. Mironov, S. F. Solodovnikov, V. E. Fedorov, and Yu. V. Gatilov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 918–922, September–October, 2004. 相似文献
59.
Sato Y Nishizawa S Teramae N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(41):11650-11656
A new class of label-free molecular beacon (MB) system based on DNA strands that contain abasic (AP) sites (AP-DNA) and adopt stem-loop structures, in combination with fluorescent ligands that bind these AP sites, has been developed. Unlike a conventional MB, which requires covalent labeling of the MB with a fluorophore and a quencher, the developed system (APMB) does not require covalent attachment of signal transduction units. Detailed sensing functions of a series of APMB systems were examined with the aid of the fluorescent ligand named ATMND to provide insight into the design strategy for APMB systems. The effects of the stem length and the position of the AP site in the stem moiety on the fluorescence response of the APMB system were examined. Genotyping of a G/C SNP of PCR amplification products was successfully demonstrated with the APMB system and blue-fluorescent ATMND as a ligand. The APMB system was further extended to a system that utilized green-fluorescent lumiflavin. 相似文献
60.
The results of quantum chemical calculations of the electronic structure and geometry of octahedral clusters [Mo6S8(CN)6]6−, [Mo6Se8(CN)6]6−, [Re6S8(CN)6]4−, and Rh6(CO)16 by the ab initio SCF (RHF) and DFT (B3LYP) methods with various basis sets are presented. The electronic states of the clusters under study
in ideal spherically symmetric potential were classified in the orbital quantum number l (1s, 1p, 1d, 1f, 1g, 1h, 1i), l = 0–6. In real crystal field with Oh symmetry these states are split. The calculated new electronic states were matched to the irreducible representations of
the point symmetry group Oh. The polarizabilities of the compounds considered are 55–65 Å3. A new model for the electronic structure of octahedral clusters containing M6 groups was proposed. The model is based on the idea of free electrons moving in spherically symmetric potential field.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2617–2624, December, 2005. 相似文献