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21.
Waly Diallo Libasse Diop Kieran C. Molloy Rudolph Willem 《Journal of organometallic chemistry》2007,692(11):2187-2192
Molecular structures of [(Ph3Sn)2O3Se] (1) and [(Ph3Sn)2O4Cr](CH3OH) (2) have been determined using spectroscopic techniques and X-ray analysis. Each structure consists of polymers containing two types of tin centres: one of them is bridged by two oxygen atoms of the trifunctional oxyanion into a helical chain while the other is pendant to this chain. In the case of the chromato derivative the pendant tin is also bonded to the oxygen atom of the solvent (methanol); hydrogen bonds between the methanol and the non-coordinated oxygen of the chromate generate a three-dimensional structure containing tin atoms in a trigonal bipyramidal environment. In contrast, the two tin centres in the non-solvated selenito derivative have distinct geometries (tetrahedral and trigonal bipyramidal). Variable temperature Mössbauer spectroscopy data are consistent with the polymeric structure of the selenito derivative while NMR spectroscopy shows the presence of monomeric species in solution. 相似文献
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针对压阻式传感器存在的零点偏差、满度偏差以及输出信号的非线性误差,提出了采用ZSSC3008传感器信号调理芯片进行补偿校准的方案。描述了传感器补偿系统的整体构架, 阐述了ZSSC3008的硬件结构、应用电路设计以及对传感器的补偿过程。实验结果表明:用上位机补偿校准软件对传感器补偿后,实现了传感器的一致性以及输出信号与压力良好的线性关系,并具有操作效率高的优点。 相似文献
23.
Ana Siu Bryan Pivovar Jackie Horsfall Keith V. Lovell Steven Holdcroft 《Journal of Polymer Science.Polymer Physics》2006,44(16):2240-2252
Novel polymers with controlled microstructures were prepared and studied to further advance the understanding of structure–property relationships of proton conducting membranes. PAN‐g‐macPSSA membranes, which contained poly(styrenesulfonic acid) (PSSA) grafts of defined graft length, are compared with PVDF‐g‐PSSA membranes, prepared by radiation‐grafting, and Nafion® 117. The intrinsic properties of PAN‐g‐macPSSA membranes are insensitive to the macromonomer graft length but are highly dependent on the ion exchange capacities (IEC). Increasing the IEC increases the content of free water absorbed by the membrane. Self‐diffusion coefficients of water in water‐swollen PAN‐g‐macPSSA were found to be similar to that of N117, despite PAN‐g‐macPSSA's higher water content. Of the polymers studied, PAN‐g‐macPSSA exhibited the lowest methanol permeability, which is explained on the basis of it containing a more tortuous ionic network. Methanol permeability decreased with decreasing volume of free water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2240–2252, 2006 相似文献
24.
用0.5mol.L-1的FeCl3溶液作引发剂,采用原位化学聚合法将吡咯单体聚合在Nafion117膜基体中。复合膜的红外光谱图中出现明显聚吡咯(PPy)的特征吸收峰,说明吡咯单体聚合在Nafion117膜中。机械性能测试表明复合膜的拉伸强度比Nafion117膜提高了。热重测试表明复合膜具有更高的热稳定性能。对复合膜进行了甲醇渗透性能的测试,结果表明复合膜具有明显的阻醇作用,PPy/NF-3膜的甲醇渗透率值是5.9×10^-7cm^2.s^-1,和Nafion117膜相比降低了53%。 相似文献
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26.
Temperature-assisted electrical poling of TeO2-Bi2O3-ZnO glasses for non-linear optical applications
The suitability for effective thermal poling of the ternary tellurite glasses with the compositions (100 − 2x)TeO2-xBi2O3-xZnO (x = 5, 10 and 15, in molar percentage) for the second harmonic generation (SHG) was analyzed. The glass transitions and crystallization temperatures were studied via differential thermal analysis. The structural properties of the annealed glasses and furtherly heat-treated samples were probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. Thermal poling of the glasses was undertaken conventionally at various temperatures close to the glass transition temperature under high vacuum and the second harmonic generated signals were compared. A new technique of two stage poling was tested for comparison. The non-linear second harmonic signal of the poled glasses was analyzed using the Maker-fringe technique and it was found that the two stage poling enhanced the non-linear efficiency when compared to the conventionally poled samples. 相似文献
27.
117mSn在肿瘤治疗中的应用 总被引:1,自引:0,他引:1
117mSn作为一个核性质比较优良的放射性核素,在近十年内成为医学领域科研人员的关注热点。本文综述了117mSn的性质、制备以及其标记化合物的研究进展。 相似文献
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I.S EdelmanA.V Malakhovskii A.M PotseluykoT.V Zarubina A.V Zamkov 《Journal of Non》2002,306(2):120-128
Absorption spectra of Pr3+ and Dy3+ embedded in three glass matrices (SiO2-P2O5-GeO2, Al2O3-B2O3-SiO2 and LiB3O5) have been studied in detail in the near infrared spectral range. The temperature related behavior of the intensity, width and position of the observed absorption lines were studied. It has been shown that f-f transitions in the studied glasses are mainly allowed by static odd distortions of the ligand environment, and these distortions decrease with a rise in temperature. Comparative analysis of the parameters of the absorption lines and their temperature dependencies in different materials have enabled us to ascertain the difference of size, symmetry and dispersion of distortions of the nearest environment of these rare earth ions in different glasses. 相似文献
30.
T. A. Chubar' M. A. Orlova I. G. Gazaryan V. A. Fechina E. A. Mareeva O. V. Ignatenko P. A. Savitskii A. M. Rozhkova V. I. Tishkov 《Russian Chemical Bulletin》1999,48(12):2330-2333
The stability of recombinant wild-type horseradish peroxidase and its tryptophan-less mutant Trp117Phe toward γ-radiation
was studied. The absence of tryptophan in the enzyme molecule results in a certain stabilization, which is manifested as the
absence of the initial drop in activity and appearance of a lag period for doses of up to 45 Gy. Contrary to the wild-type
enzyme, the dose response of the mutant is almost independent of the nature of the substrate used to measure the catalytic
activity; this indirectly indicates that Trp117 participates in the oxidation of substrates. Pretreatment of the wild-type
recombinant enzyme with hydrogen peroxide destabilizes the enzyme towards irradiation, while the same procedure for the mutant
enzyme has virtually no effect on the dose response curve. This suggests the modification of Trp117 in the oxidation of the
native enzyme with H2O2 in the absence of electron-donor substrates, which is the modification of Trp171 in the recombinant lignin peroxidase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2355–2358, December, 1999. 相似文献