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排序方式: 共有93条查询结果,搜索用时 593 毫秒
1.
Khalid M. Tawarah Fuad A. Ababneh 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(1):15-22
The binding of K+ by dibenzo-pyridino-18-crown-6 (B2-py-18-C-6) and1,10-N,N-didecyl-diaza-18-crown-6 (22-DD) has been studiedconductometrically at 10, 15, 20 and 25 °C in acetonitrile. Thecomplexes formed were assumed to have 1 : 1 stoichiometry. The complexes ofK+ with 18-crown-6 (18-C-6) and dibenzo-18-crown-6 (B2-18-C-6) were alsostudied for comparison purposes. The stability constant, K, of a givencomplex and its molar conductance, c, were obtained by subjectingthe conductance data to a non-linear least-squares curve fitting procedure.The values of the enthalpy change, H, the entropy change, Sand the Gibbs free energy, G, associated with the formation of the 1: 1 complexes were derived and compared with relevant literature data. Thevalues of G at 25 °C indicate that the binding capacity of thefour macrocycles follows the order 18-C-6 > 22-DD > B2-18-C-6 >B2-py-18-C-6. The difference between the molar ionic conductance of the freeK+ cation and that of the bound cation, KL+, was estimated and the trend insuch differences correlates with the molecular size of the macrocycle, L. 相似文献
2.
In this paper, we propose three new matrix versions of the arithmetic–geometric mean inequality for unitarily invariant norms, which stem from the fact that the Heinz mean of two positive real numbers interpolates between the geometric and arithmetic means of these numbers. Related trace inequalities are also presented. 相似文献
3.
Commutator inequalities associated with the polar decomposition 总被引:1,自引:0,他引:1
Fuad Kittaneh 《Proceedings of the American Mathematical Society》2002,130(5):1279-1283
Let be a polar decomposition of an complex matrix . Then for every unitarily invariant norm , it is shown that
where denotes the operator norm. This is a quantitative version of the well-known result that is normal if and only if . Related inequalities involving self-commutators are also obtained.
where denotes the operator norm. This is a quantitative version of the well-known result that is normal if and only if . Related inequalities involving self-commutators are also obtained.
4.
Anina Wöhl Dr. Wolfgang Müller Dr. Stephan Peitz Normen Peulecke Dr. Bhaskar R. Aluri Dr. Bernd H. Müller Dr. Detlef Heller Dr. Uwe Rosenthal Prof. Dr. Mohammed H. Al‐Hazmi Dr. Fuad M. Mosa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7833-7842
In this paper we report the results of an extensive experimental kinetic study carried out on the novel ethylene trimerization catalyst system, comprising the chromium source [CrCl3(thf)3] (thf=tetrahydrofuran), a Ph2P‐N(iPr)‐P(Ph)‐N(iPr)H (PNPNH) ligand (Ph=phenyl, iPr=isopropyl), and triethylaluminum (AlEt3) as activator. It could be shown that the initial activity shows a first‐order dependency on the ethylene concentration. Also, a first‐order dependency was found for the catalyst concentration. The initial activity follows a typical Arrhenius behavior with an experimentally determined activation energy of 52.6 kJ mol?1. At elevated temperatures (ca. 80 °C), a significant deactivation was observed, which can be tentatively traced back to a ligand rearrangement in the presence of AlEt3. After a fast initial phase, a pronounced ‘kink’ in the ethylene‐uptake curve is observed, followed by a slow, almost linear, further increase of the total ethylene consumption. The catalyst composition, in particular the ligand/chromium and the cocatalyst/chromium molar ratio, has a strong impact on the catalytic performance of the trimerization of ethylene. 相似文献
5.
Norm inequalities for partitioned operators and an application 总被引:6,自引:0,他引:6
6.
E. Fuad Kent 《Fluid Dynamics Research》1996,18(6):307-312
A comparative study of visualization of Stokes flow induced by rotation of a circular cylinder in a V-shaped and rectangular channel was performed. The visualization was carried out using solid tracers of magnesium. Some quantitative data were deduced from visualization photographs and a comparison was made. 相似文献
7.
Fuad Kittaneh 《Linear and Multilinear Algebra》2013,61(4):203-206
It is shown that if the singular values of a compact operator T are dominated by those of the real part of T, then T must be self-adjoint. This improves an earlier result of Fong and Tsui. Some remarks on singular value inequalities associated with the Cartesian decomposition of a compact operator are also given. 相似文献
8.
9.
Chemistry of Natural Compounds - 相似文献
10.
Wahl A Al-Rimawi F Schnell I Kornysova O Maruska A Pyell U 《Journal of separation science》2008,31(9):1519-1528
A synthetic route to acrylamide-based monolithic stationary phases for CEC with rotaxane-type immobilized derivatized beta-CD was explored. N,N'-Ethylenedianilinediacrylamide was synthesized as the water-insoluble crosslinker forming water-soluble inclusion complexes with statistically methylated beta-CD. Mixed-mode stationary phases were synthesized by free radical copolymerization of the bisacrylamide-CD host-guest complex with water-soluble monomers and an additional water-soluble crosslinker in aqueous solution. Complex formation in solution and inclusion of the pseudorotaxane into the polymeric network (formation of a polyrotaxane architecture) were studied by means of (1)H-NMR chemical shift analysis, CD modified micellar EKC (CD-MEKC), 2D-NOESY spectroscopy, and solid state( 13)C-NMR spectroscopy. The presence of a mixed-mode selectivity of the stationary phase based on hydrophobic and hydrophilic interaction was confirmed by CEC with neutral polar and nonpolar solutes. 相似文献