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31.
Mössbauer measurements in a-(Fe0.765Mn0.235)78Sn2Si6B14 have been performed with57Fe and119Sn. Both hyperfine fields show a kink near 70 K, indicating a freezing of the transverse spins. The ratio of the two hyperfine fields contains information about the correlation of the transverse spins. The ratioB
hf(Sn)/B
hf(Fe) stays constant aboveT
xy
and rises belowT
xy
. This indicates an alignment of the transverse spins on a local scale, as was also found inAuFe and a-FeZr. 相似文献
32.
33.
34.
The equilibrium geometries, electronic structures, as well as one- and two-photon absorption cross sections of a series of octupolar chromophores with Zn(2+) or Cu(+) as coordinate centers and 4,4'-bis(dibutylaminostyryl)-[2,2']-bis(bipyridyl) as ligands have been determined by using B3LYP/6-31G and ZINDO methods. These molecules are designed by controlled combination of two or three bipyridyl ligands with the metal centers. The results show that Zn(2+) is an effective template for the design of octupolar structures which enable it to form tetrahedral and octahedral coordinated complexes; while Cu(+) only exists in a tetrahedral coordinated complex, comparing the tetrahedral complex with Zn(2+) as the center with that of Cu(+) as the center, it is found that the complex with the Cu(+) center is a better two-photon absorption material than the former as far as the transparency/nonlinearity is concerned. Furthermore, for the same metal center of Zn(2+), both one- and two-photon absorptions of the tetrahedral complex are redshifted relative to those of the octahedral complex, is attributed to the spiroconjugation effect in the tetrahedral complex. Our theoretical findings are consistent with recent experimental observations and provide an important foundation for the design of improved transparency-nonlinearity two-photon absorption materials. 相似文献
35.
René P. Sperb 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1984,35(1):116-121
Upper and lower bounds for the effectiveness factor
are derived, whereu is the solution of u=c
2
u in,u=1 on .
This research was done while the author was visiting Cornell University, Ithaca, New York. 相似文献
Zusammenfassung Es werden obere und untere Schranken hergeleitet für den Diffusionsfaktor , wobeiu die Lösung ist von u=c 2 u in,u=1 auf .
This research was done while the author was visiting Cornell University, Ithaca, New York. 相似文献
36.
Zi-Zhong Li Qing-Xiang Guo Tan Ren Xiao-Qing Zhu You-Cheng Liu 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(1):37-42
Tetramethylsilane (TMS) can be included by -cyclodextrin (-CD), and sodium 2,2-dimethylsilapentane-5-sulphonate (DSS) can form inclusion complexes with - and -CD. The NMR chemical shifts are changed considerably as a result of the strong interaction between CD and the guest compound in the inclusion complexes. A downfield shift of as much as 0.63 ppm shift downfield has been observed for the protons of external TMS in CD aqueous solution. In view of this, the question arises of whether TMS and DSS can be used as internal references. DSS in D2O is suggested as an external reference for aqueous cyclodextrin solution in NMR measurements. 相似文献
37.
A new series of MR-IPN polyacrylamide—poly(vinyl-ethylenediamine)chelatesorbents were prepared by the reaction of ethylenediamine with MR-IPN matrixes.The newchelate sorbent showed good sorption properties for auric and platinic ions. 相似文献
38.
Metathesis reactions between Ru(2)(DMBA)(4)Cl(2) (DMBA = N,N'-dimethylbenzamidinate) and MX (M = Na and K) yielded bis-adduct derivatives Ru(2)(DMBA)(4)X(2) (X = CN (1), N(3) (2), N(CN)(2) (3)). Metathesis reactions between Ru(2)(DMBA)(4)(NO(3))(2) and KI resulted in Ru(2)(DMBA)(4)I(2) (4). Compound 1 is diamagnetic, while compounds 2-4 are paramagnetic (S = 1). Both compounds 1 and 2 undergo two reversible one-electron processes, an oxidation and a reduction, while compound 3 features a quasireversible reduction. Single-crystal X-ray diffraction studies revealed that the Ru-Ru bond lengths are 2.4508(9), 2.3166(7), 2.304[1], and 2.328(1) A for compounds 1-4, respectively. Structural and electrochemical data clearly indicate that the axial ligands impart a significant influence on the electronic structures of diruthenium species. 相似文献
39.
René Fourneau 《Journal of Geometry》1977,9(1-2):143-147
In this paper, we give some properties of Choquet simplices which lead to the characterization of the closed Choquet simplices of n.The results of this paper were presented at the Conference on Convexity and Foundation of Geometry held in Haifa (10–14 March 1975). 相似文献
40.
Qin B Lin J Lin Z Ren H Xue Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(4):717-720
The vibration spectrum and FAB mass spectrum of (+/-)-1-[3-(2-methoxyphenoxy)-2-hydroxypropyl]-4-[(2,6-dimethylphenyl)aminocarbonylmethyl]piperazine dihydrochloride salt was studied. By comparing with the spectra of free base, different bands of IR were found in the NH+ stretching, the NH+ deformation motion, the CH2 of NCH2 group symmetric stretching, the CH2 of N-CH2 group twisting and the CN stretching. FAB shows the basic peak is M + H. Other m/e peaks are consistent with the structure. 相似文献