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991.
Min‐Shiun Chao 《中国化学会会志》2003,50(6):1131-1138
Ionic polyurethanes (PUs) were prepared from hydroxyl‐terminated polybutadiene (HTPB) and 4,4′‐dicyclohexylmethane diisocyanate (H12MDI) by a two‐stage method. The ionic group was introduced by adding 4,8‐diazaundecanediamide (L‐2,3,2) as the chain extender of which the tertiary amines and carbonyl groups were complexed with nickel ions. It was found that the binding of hard segments and the flexibility of soft segments had subtle effects on the gas permeability. The effects of hard segment content and the amount of nickel ion on the gas permeability and morphological properties were investigated. Fourier transform infrared (FTIR) spectroscopy was utilized to identify the segregation between hard and soft segments and structure change, which affect the transport properties. The hydrogen bonding index (HBI), frequency difference, and shift as a measure of the phase segregation and the average strength of the interpolymer hydrogen bonds were utilized to study the intermolecular interaction and transport property of the prepared PUs. The oxygen and nitrogen permeabilities of membranes were determined by using gas permeability analyzer. The results of FTIR, differential scanning calorimetry and thermogravimetric analysis measurements explain the complexation and, hence, the gas permeability. 相似文献
992.
Somnath Roy Tarak Nath Mandal Anil Kumar Barik Sachindranath Pal Samik Gupta Arijit Hazra Ray J. Butcher Allen D. Hunter Matthias Zeller Susanta Kumar Kar 《Polyhedron》2007
Two new pyrimidine based NNS tridentate Schiff base ligands S-methyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL1] and S-benzyl-3-((2-S-methyl-6-methyl-4-pyrimidyl)methyl)dithiocarbazate [HL2] have been synthesised by the 1:1 condensation of 2-S-methylmercapto-6-methylpyrimidine-4-carbaldehyde and S-methyl/S-benzyl dithiocarbazate. A Ni(II) complex of HL1 and Co(III) and Fe(III) complexes of HL2 have been prepared and characterized by elemental analyses, molar conductivities, magnetic susceptibilities and spectroscopic studies. All the bis-chelate complexes have a distorted octahedral arrangement with an N4S2 chromophore around the central metal ion. Each ligand molecule binds the metal ion using the pyrimidyl and azomethine nitrogen and thiolato sulfur atoms (except in the nickel complex, one ligand molecule uses the thione sulfur in lieu of thiolato sulfur atom). In the Ni(II) complex, one of the ligand molecules behaves as a neutral tridentate and the other molecule functions as a uninegative tridentate, whereas in the Co(III) and Fe(III) complexes, the ligand molecules behave as monoanionic tridentate. All the complexes were analyzed by single crystal X-ray diffraction and significant differences concerning the distortion from an octahedral geometry of the coordination environment were observed. 相似文献
993.
994.
微柱高效液相色谱法测定环境样品中的铁、钴、镍、铜、锌、锰 总被引:1,自引:0,他引:1
研究了用 2-(2-喹啉偶氮 )-间苯二酚 (QAR)为柱前衍生试剂 ,以WatersXterraTM RP18(1 .0×5 0mm ,2. 5 μm)微柱为固定相 ,60 %的甲醇 (内含 0 . 5 %的醋酸 )为流动相 ,高效液相色谱分离、二极管矩阵检测器测定铁、钴、镍、铜、锌和锰的方法。根据信噪比 (S N =3 )得各金属离子的检测限分别为 :铁3 μg L、钴 4μg L、镍 2 μg L、铜 4μg L、锌 5 μg L、锰 8μg L ,方法用于环境样品中痕量铁、钴、镍、铜、锌、锰的测定 ,相对标准偏差在 1 . 6%~ 3 . 5 %之间 ,标准回收率为 93 %~ 1 0 7%。 相似文献
995.
Versican is the major matrix proteoglycan in aortic wall and participates in various biological functions of the tissue. In the present study the molecular characteristics of versican isolated from normal human aorta as well as those of versican expressed in aneurysmal aortic tissue were examined. Versican was isolated by combined anion-exchange and gel permeation chromatography and was further characterized by high-performance liquid chromatography, polyacrylamide gel electrophoresis and immunoblotting. In both tissues versican is exclusively substituted with chondroitin sulfate chains, in contrast to other human tissues where both chondroitin and dermatan sulfate chains are attached onto versican core proteins. Except for the significant decrease in the concentration of versican in the aneurysmal tissue, this PG undergoes specific alterations in the aneurysmal tissue. The molecular size of versican isolated from diseased tissue is decreased with a simultaneous increase in the ratio of glycosaminoglycan to protein in this tissue. The latter reflect the extensive fragmentation of versican in the diseased tissue and most probably the generation of shorter peptides enriched to glycosaminoglycan chains. Although the size of chondroitin sulfate chains is identical in both versican preparations, a significant increase in the percentage of 6-sulfated disaccharides is observed in chondroitin sulfate chains of versican in aneurysmal aortas, which is accompanied by decrease in 4-sulfated and non-sulfated units. 相似文献
996.
Versatile synthesis of some analogues of the naturally-occurring α-glucosidase inhibitor salacinol (1), involving thioanhydro alditol moieties with erythro, d,l-threo, xylo, ribo, d-arabino and d-manno configurations is described. Nucleophilic attack at the least-hindered carbon atom of an l- or d-protected erythritol cyclic sulfate by the thioanhydro alditol sulfur atom yielded the desired zwitterionic compounds. In addition, the preparation of the cyclic sulfates of 2,4-O-benzylidene-d-erythritol and 2,4-O-isopropylidene-l-erythritol was improved. Enzyme inhibition tests showed that most of the new compounds were weak but specific inhibitors, while good inhibitory activity was found for a six-membered ring analogue (β-glucosidase: Ki=16 μM). 相似文献
997.
R. Rozik R. Oriňàková K. Markušová L. Trnková 《Journal of Solid State Electrochemistry》2006,10(7):423-429
This paper describes a process of electrolytic deposition of nickel–cobalt (Ni–Co) binary alloy on Fe powder. Electrochemical behavior of this binary alloy was studied by cyclic voltammetry with a paraffin impregnated graphite electrode as a working electrode. Deposition of individual metals (Ni, Co), as well as the simultaneous nickel–cobalt co-deposition, was performed in aqueous solutions (Watts-type electrolyte) both with and without Fe powder. Special attention was paid to the influence of suspension density on the electrode process. This density affects on the quality of iron powder electroplating. Preferential deposition of the less noble metal (Co) leading to its higher content in the deposit was observed in contrast to the more noble one (Ni) in spite of higher content of Ni in the plating solution. This anomalous phenomenon–known already for other metals (Zn, Cd, Sn)–has been confirmed and investigated for iron-group metals (Fe, Co, Ni) in this work. Electrolytic deposition of Ni–Co binary alloys, including anomalous behavior is a complicated process. Understanding the anomalous behavior would lead to better control of the deposition process and to explanation of the mechanism of Ni–Co co-deposition. 相似文献
998.
Marcelo R. L. Oliveira José E. J. C. Graúdo Nivaldo L. Speziali Vito M. De Bellis 《Structural chemistry》1999,10(1):41-45
Potassium N-4-methylphenylsulfonyldithiocarbimate, K2(4-CH3C6H4SO2N=CS2), reacted with nickel(II) chloride hexahydrate and tetrabutylammonium bromide to form the bis(N-4-methylphenylsulfonyldithiocarbimate)nickelate(II) tetrabutylammonium salt (Bu4N)2[Ni(4-CH3C6H4S2C=NSO2)2]. The elemental analyses, IR and UV-Vis data obtained were consistent with the formation of a
diamagnetic planar complex. The 1H NMR and the 13C NMR spectra showed the expected signals for the dithiocarbimate moiety and the tetrabutylammonium cation. The single-crystal structure analysis showed that this substance crystallizes in the triclinic
space group with a = 10.474(3) Å, b = 10.767(3) Å, c = 13.657(3) Å and = 81.54(2)°, = 80.44(2)°, = 67.63(2)°, V = 1398.5(8) Å3, and Z = 2. The nickel atom is coordinated to four sulfur atoms. 相似文献
999.
1000.
The hydrogen bond strength in kieserite-type sulfate and selenate monohydrates has been studied by the method of double-matrix spectroscopy. The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) kieserite-type compounds MXO4·H2O (M=Mn, Co, Ni, Zn, and X=S, Se) with matrix-isolated X′O42− and M′2+ guest ions are presented and discussed in the region of the OD stretching modes. The OD frequencies indicate that the compounds under investigation form comparatively strong hydrogen bonds. The frequency shifts of the uncoupled OD stretching modes of the HDO molecules within the isostructural series and those influenced by the guest ions, and the strength of the hydrogen bonds formed, are discussed in terms of the respective OwO distances, which hint at stronger hydrogen bonds for the sulfate series than for the selenate one by mistake, the larger hydrogen bond acceptor capability of SeO42− ions compared to SO42− ones, the different metal–water interactions and repulsion potentials of the lattice, and the reorientation of the water molecules caused by the guest ions. The shifts of the OD stretches of the ODOSe′O3 bonds (Se′O42− matrix isolated) to the lower wavenumbers as compared to the parent selenates are caused by the reorientation of the hydrate water molecules and strengthening the hydrogen bond to the stronger acceptor and vice versa. When smaller metal ions having smaller M–OH2 bond lengths and, hence, stronger synergetic effect replace larger ones, the OD stretches are shifted to lower wavenumbers as compared to those due to the host M–OwO bonds and vice versa. 相似文献