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排序方式: 共有238条查询结果,搜索用时 15 毫秒
91.
The association constants, Ka of KI, Nal and CaCl2 complexing with 1,4,7,10,13-pentaoxacyclopentadecane and 1,4,7,10,13,16-hexaoxacycloocta-decane in DHO were determined by the aid of 13C dipole-dipole relaxation time measurements. The mole fraction of the complexed ligand, PC were obtained by the use of the equation of 1/Tobs 1 - 1/T10 = PC (1/TO 1 - 1/T10) where the T10 and To 1 are the relaxation times of free and complexed macrocyclic ethers respectively. Ka values obtained from the above given equation depending on the cation concentration, [A+ O] typically reflected the relation between the cationic radius and cyclic ether ring size. 相似文献
92.
The melt rheology of polysulfone was studied in steady shear and oscillatory shear flow. Even when melt viscosity data were corrected for the dependence of the glass transition temperature on M n the viscosity molecular weight relation was not a simple power law over any appreciable range. The melt compliance is very low and reaches its maximum value at molecular weights > 2000. Since the molecular flexibility, measured as the size of the equivalent random segment of rubber elasticity theory, is similar to that of other common polymers, this suggests that the polar nature of polysulfone is contributing to the high “entanglement” density. 相似文献
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Yiğit Murat Karaca Emine Özge Yiğit Beyhan Gürbüz Nevin Özdemir İsmail 《Transition Metal Chemistry》2019,44(6):565-573
Transition Metal Chemistry - New ruthenium(II) complexes with N-heterocyclic carbene ligand were synthesized by transmetalation reactions between silver(I) N-heterocyclic carbene complexes and... 相似文献
96.
New, sterically demanding 1,3‐dialkylbenzimidazolium salts ( 2a–c ) as N‐heterocyclic‐carbene precursors have been synthesized and characterized. The ortho position of aromatic aldehydes was directly and selectively arylated with aryl chlorides in the presence of a catalytic system prepared in situ from Pd(OAc)2, 1,3‐dialkylbenzimidazolium chlorides ( 2a–c ), and Cs2CO3. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:569–574, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20479 相似文献
97.
A new chelating resin, poly(diacetonitrile methacrylamide-co-divinylbenzene-co-vinylimidazole), was synthesized and characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and elemental analysis. The novel resin was used for the first time as a chelating adsorbent for the preconcentration of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn from various samples by flame atomic absorption spectrometry. The adsorption capacities of the resin were 29.3, 31.6, 29.3, 27.3, 35.5, 31.7, 39.8, and 32.3?mg?g?1 for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn, respectively. The detection limits of the metal ions were from 0.42 to 3.21?µg?L?1. A preconcentration factor of 30 for all metal ions was obtained. The precision of the method as the relative standard deviation was less than or equal to 2.6%. The described method was validated with certified reference materials and fortified real samples. The method was used for the determination of the analytes in well water and wastewater. 相似文献
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J. M. Nevin 《General Relativity and Gravitation》1991,23(3):253-260
The Einstein field equations are solved assuming spherical or static cylindrical symmetry and a string dust source. All solutions which may be matched onr =a to an external vacuum solution having the same symmetry are found. 相似文献