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941.
942.
943.
Ildikó Mohammed-Ziegler Áron Szöllősy Miklós Kubinyi András Grofcsik Alajos Grün István Bitter 《Supramolecular chemistry》2013,25(6):415-421
Complexation of lithium ions by three chromoionophoric calix[4]arenes has been studied by 1H and 7Li NMR spectroscopy. The signalling unit of the chromoionophores is the N-methylpyridinium(methyleneimino) group in conjugation with a phenolic group of the calixarene ring while the coordination spheres contain esteric (ethoxycarbonylmethoxy) or etheric (ethoxy, propoxy) units. 1H NMR and NOESY measurements suggest the dominance of cone conformations of the calixarene rings with slight, solvent-dependent distortions. Complexation occurs only in the presence of a weak base. The interaction with lithium ions causes a broadening of both the 1H and 7Li NMR signals. Analysis of the chemical shifts in the three complexes indicates a different coordination environment for the lithium with the calixarene containing esteric groups from those having etheric groups. This explains the differences in the stabilities of the lithium complexes of the two types of calixarenes. 相似文献
944.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5-6):559-576
In this work, phenylisocyanate was polymerized in bulk and in a solution of THF by the complex base (CB), NaNH2/(CH3)3CONa catalyst under vacuum. The percent yield for bulk polymerization at ?20°C first increased with a slow rate reaching 32% conversion in 3 hours, then with a greater rate up to 86% in 6 hours. However, at 0°C the yields were relatively smaller and not very reproducible. The product obtained was a high molecular weight polymer, insoluble in most solvents, and partially crystalline. The polymerization in THF at ?20° gave 58% conversion in 9 hours with a high rate first, then a slower rate. The polymer samples were characterized by fractionation, FT-IR, DSC, NMR, TGA, and X-ray powder diffraction. The polymer samples in the solution polymerization contained trimer and oligomeric components. No glass transition temperature was observed at the temperature interval studied. 相似文献
945.
Hartmut Komber Gisbert Grossmann Axel Kretschmer 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):335-343
Abstract Compounds of the following structure (R1O)2(X)P[sbnd]Y–P(X)(OR2)2 (X = O, Y = Sn (n = 1–4), R1 = R2 = Me, iPr; X = S, Y = Sn (n = 1–4), R1, R2 = Me, Et, iPr, iBu; X = S, Y = S-Se-S, S-Te-S, R1 = R2 = Me were prepared and their NMR spectra were analysed. Depending on the number of sulfur atoms, bonded between the phosphorus atoms, typical ranges of the P-P coupling constants were found for the different sulfanes investigated: 2JPP from-10 to-20 Hz, 3JPP less than 3 Hz, 4JPP from +10 to +13 Hz and 5JPP less than 1 Hz. For the small vicinal coupling constants and the relatively large values of 4JPP different possibilities of their interpretation are given. 相似文献
946.
《Separation & Purification Reviews》2013,42(1):171-228
The toxic nature of some dyestuffs (DSs) has long been recognized. Accordingly, dyeing wastewaters represent a source of water contamination, and should be treated in some way so as to reduce the concentration of the polluting DSs to permissible limits, prior to dumping its wastewater. In addition, some DSs can be recovered for reuse, a point which should represent saving in the overall cost of the dyeing process. Extensive publications on the removal of DSs from dye house wastewaters have been cited in the literature in which many techniques have been applied, biological treatment being the method most widely used as a primary treatment. However, only few publications have been concerned with recovery of DSs from their wastewaters. In the present paper, numerous techniques, if not all, that are presently used for either removal or recovery of DSs have been reviewed, evaluated and compared. 相似文献
947.
The thermodynamic properties of binary liquid mixtures of (aldehyde + alcohol) are strongly influenced by chemical reactions in particular around and below ambient temperature. In two previous publications the chemical reaction equilibrium was investigated by 13C – Fourier transform NMR-spectroscopy at temperatures between 255 K and 295 K for a series of aldehydes (acetaldehyde, 1-propanal, 1-butanal, 1-heptanal) with three alcohols (methanol, ethanol, 1-propanol). Here these investigations are extended to three more aldehydes (1-decanal, 3-phenylpropanal and 2-chlorobenzaldehyde, respectively). The results for the binary systems with decanal or 3-phenylpropanal as the aldehyde in the binary mixture (aldehyde + alcohol) confirm the expectations from the first parts of this series, i.e., that the majority of the constituents of the mixture is present as hemiacetal and the first two poly(oxymethylene) – hemiacetals. The numerical results for the chemical reaction equilibrium constants from the previous investigations can be used to predict quantitatively the speciation in binary systems of ((either 1-decanal or 3-phenylpropanal) + (either methanol or ethanol or 1-propanol)). However the experimental results with 2-chlorobenzaldehyde reveal a different behaviour. In all investigated systems (2-chlorobenzaldehyde + alcohol) the most important reaction product was the corresponding acetal whereas the amounts of hemiacetal were very small. While the amounts of hemiacteal could still be quantified, it was not possible to quantify the amount of any poly(oxymethylene) – hemiacetal. 相似文献
948.
In this paper, by introducing a definition of parameterized comparison
matrix of a given complex square matrix, the solvability of a parameterized class
of complex nonsymmetric algebraic Riccati equations (NAREs) is discussed. The
existence and uniqueness of the extremal solutions of the NAREs is proved. Some
classical numerical methods can be applied to compute the extremal solutions of the
NAREs, mainly including the Schur method, the basic fixed-point iterative methods,
Newton's method and the doubling algorithms. Furthermore, the linear convergence
of the basic fixed-point iterative methods and the quadratic convergence of Newton's
method and the doubling algorithms are also shown. Moreover, some concrete parameter selection strategies in complex number field for the doubling algorithms
are also given. Numerical experiments demonstrate that our numerical methods are
effective. 相似文献
949.
Generalized Coupled Fixed Point Results on Complex Partial Metric Space Using Contractive Condition 下载免费PDF全文
Mani Gunaseelan Lakshmi Narayan Mishr Vishnu Narayan Mishra 《Journal of Nonlinear Modeling and Analysis》2021,3(1):93-104
In this paper, we obtain coupled fixed point results on complex partial metric space under contractive condition. An example to support our result is presented. 相似文献
950.
研究节点输出耦合混沌复杂动态网络不稳定平衡点的控制问题,基于输出控制思想,提出网络节点不稳定平衡点的全局控制方法以及牵制控制方法,将混沌复杂动态网络的所有节点镇定到其平衡点.利用李稚普诺夫稳定性理论,得到控制器参数选择条件,以蔡氏混沌电路作为网络节点动态进行仿真研究,证明该方法的有效性. 相似文献