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排序方式: 共有437条查询结果,搜索用时 15 毫秒
1.
Ladislav Pesek Leszek A. Dobrzanski Pavol Zubko Jaroslaw Konieczny 《Journal of magnetism and magnetic materials》2006
The paper presents mechanical properties of two kinds of Co-based and one Fe-based metallic ribbons by the depth sensing indentation (DSI) technique. Investigations were carried out on two kinds ternary alloy Co77Si11,5B11,5 and Fe78Si13B9 and multicomponent Co68Fe4Mo1Si13,5B13,5, which are so-called “zero-magnetostriction” materials. Metallic ribbons were investigated in amorphous state and partially crystallized state after annealing in 400°C in argon atmosphere. Heating of ribbons obtained by melt spinning technique was performed to check its effect on changes of mechanical properties. 相似文献
2.
Raman spectra of electrochemically charged single-wall carbon nanotubes (HiPco) were studied by five different laser photon energies between 1.56 and 1.92 eV. The bands of radial breathing modes (RBM) were assigned to defined chiralities by using the experimental Kataura plot. The particular (n,m) tubes exhibit different sensitivity to electrochemical doping, monitored as the attenuation of the RBM intensities. Tubes which are in good resonance with the exciting laser exhibit strong doping-induced drop of the RBM intensity. On the other hand, tubes whose optical transition energy is larger than the energy of an exciting photon show only small changes of their RBM intensities upon doping. This rule presents a tool for analysis of mixtures of single-walled carbon tubes of unknown chiralities. It also asks for a re-interpretation of some earlier results which were reported on the diameter-selectivity of doping. The radial breathing mode in strongly n- or p-doped nanotubes exhibited a blue-shift. A suggested interpretation follows from the charging-induced structural changes of SWCNTs bundles, which also includes a partial de-bundling of tube ropes. 相似文献
3.
Summary New cyanato-copper(II) complexes with aminopyridines (ampy) were prepared and studied;viz. Cu(NCO)2(3-ampy)2 (- and -form), Cu(NCO)2(3-ampy)2(H2O), Cu(NCO)2(4ampy)2, and Cu(NCO)2(2-ampy). According to physical results, the Cu(NCO)2L2 complexes exhibitpseudo-octahedral structures with amine nitrogens or cyanate oxygens occupying axial sites. For - and -Cu(NCO)2(3-ampy)2 the crystal structure reorganization is connected with a change in axial distortion. The compound Cu(NCO)2(2-ampy) is square pyramidal or — more probably — rhombic octahedral and its strong antiferromagnetism reveals the N-bridging function of the NCO groups.Part XXII, Ref. 9. 相似文献
4.
The problem of calculation of Sturmian functions (positive energy Weinberg states) for nonlocal (exchange) interactions is considered. It is shown that the method of continued fractions proposed by Horáek and Sasakawa makes the calculation of Sturmian eigenfunctions and eigenvalues feasible even for complicated nonlocal interactions. As an example Sturmian functions and Sturmian eigenvalues for the low energy electron-hydrogen scattering in the static exchange approximation are calculated. In addition a very general proof of convergence of the method of continued fractions is presented.Dedicated to the memory of Professor Jozef Kvasnica. 相似文献
5.
Oriňák Andrej Vering Guido Arlinghaus Heinrich F. Andersson Jan T. Halas Ladislav Oriňáková Renáta Turčániová Ľudmila 《平面色谱法杂志一现代薄层色谱法》2005,18(1):44-50
JPC – Journal of Planar Chromatography – Modern TLC - A new hyphenated technique that enables coupling of thin-layer chromatography (TLC) with time-of-flight secondary-ion mass... 相似文献
6.
Ladislav Sojk 《Journal of chromatography. A》1980,190(2)
The optimal separation properties of Carbowax 20M as a stationary phase in 300-m glass capillary columns at temeperatures below its lower temperature limit (60°) in terms of the selectivity, efficiency and speed of the gas chromatographic analysis of isomeric C10---13n-alkenes were investigated.In the separation of isomeric n-alkenes two possible states of the Carbowax stationary phase below 60° were used (solid state and intermediate liquid state), and the dependence of the retention of the isomers on temperature was studied. The region of the hysteresis portion of the ICW = f(T)diagram permits the continuous setting of column selectivity. The efficiency of the column at temperatures below the lower temperature limit of Carbowax 20M depends on the spatial cis-trans configuration of n-alkenes and, in the solid state, for cis-isomers is comparable to the high efficiency of this column at higher temperatures (115°). Utilization of Carbowax 20M in the solid state made it possible to achieve faster and more complete separations of the eleven possible positional and spatial isomers of n-tridecenes in comparison with previous methods. 相似文献
7.
Kyselová Z Kysel'ová Z Krizanová L Soltés L Stefek M 《Journal of chromatography. A》2005,1084(1-2):95-100
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of eye lens proteins showed that both progression of diabetic cataract in rats in vivo and precipitation of soluble eye lens proteins stressed by free radicals in vitro were accompanied by significant protein cross-linking. There was a noticeable contribution of disulfide bridges to protein cross-linking in diabetic eye lens in vivo. In contrast, under conditions in vitro, when eye lens proteins were exposed to hydroxyl or peroxyl radicals, we showed that the participation of reducible disulfide linkages in the formation of high molecular mass products was markedly lower. These in vivo--in vitro differences indicate that the generally accepted role of reactive oxygen species in diabetic cataractogenesis may be overestimated in connection with the processes of protein cross-linking. 相似文献
8.
Stereoselectivity of reductive amination of (R)-1-hydroxy-1-phenylpropan-2-one by methylamine was studied. From the four isomers possible, only two are produced by this
reaction. These are marked as (−)-(1R,2S)-ephedrine (desired product) and (+)-(1S,2R)-ephedrine. The reaction stereoselectivity depends both on the type of the catalyst and reaction conditions. The most suitable
type is the supported platinum. However, this catalyst rapidly deactivates. With a decreasing activity of Pt catalyst, the
stereoselectivity decreases. It is also decreased during the production of the second liquid phase (water) in the reaction
mixture. 相似文献
9.
Chitosan is industrially acquired by the alkaline N-deacetylation of chitin. Chitin belongs to the β-N-acetyl-glucosamine polymers, providing structure, contrary to α-polymers, which provide food and energy. Another β-polymer providing structure is hyaluronan. A lot of studies have been performed on chitosan to explore its industrial use. Since chitosan is biodegradable, non-toxic, bacteriostatic, and fungistatic, it has numerous applications in medicine. Hyaluronan, one of the major structural components of the extracellular matrix in vertebrate tissues, is broadly exploited in medicine as well. This review summarizes the main areas where these two biopolymers have an impact. The reviewed areas mostly cover most medical applications, along with non-medical applications, such as cosmetics. 相似文献
10.
3T3 and VH10 cells were subjected to oxidative damage by hydroxyl radicals generated from Cu(II) ions and ascorbate. The presence of reactive oxygen and nitrogen species in cells was determined using fluorescent dyes. MitoQ—a mitochondrially targeted antioxidant—was examined to prevent cell death and was compared with trolox as a reference standard serving as an antioxidant. MitoQ at lower concentrations (up to 500 nM) prevented damage of mitochondria and thereby increased viability of cells. However, at higher concentrations (over 500 nM) MitoQ decreased the viability of both strains of cells. The last observation indicates that the application of MitoQ should be evaluated also from the point of its cell-destructive potential. 相似文献