排序方式: 共有60条查询结果,搜索用时 125 毫秒
1.
2.
The 1,6,7,12,13,18‐hexaazatrinaphthylene (HATN) complex [(Et2Zn)3(μ3‐HATN)] was synthesized and characterized by IR spectroscopy, UV/Vis spectroscopy, elemental analysis and ESI‐MS spectrometry. Attempts to prepare ZnCl2 complexes of HATN leads only to the mononuclear [(Cl2Zn)(HATN)] derivative, characterized by X‐ray diffraction, IR‐ and UV/Vis‐spectroscopy as well as ESI‐MS spectrometry. The bright red 2,2′‐bipyridine (bipy) complex [(Et2Zn)(bipy)] ( 1 ) was synthesized and characterized by X‐ray diffraction and NMR spectroscopy. The UV/Vis‐spectra of the HATN‐complexes show absorptions in regions of far longer wavelengths than the corresponding 2,2′‐bipyridine or 1,10‐phenantroline complexes. Consequently the π*‐LUMO of HATN ( 5 ) is lower in energy than the π*‐LUMO of 2,2′‐bipyridine ( 2 ) or 1,10‐phenanthroline (phen). 相似文献
3.
Quay van der Hoff Ansie Harding 《International Journal of Mathematical Education in Science & Technology》2017,48(1):16-30
This study focuses on the mathematics department at a South African university and in particular on teaching of calculus to first year engineering students. The paper reports on a cause–effect analysis, often used for business improvement. The cause–effect analysis indicates that there are many factors that impact on secondary school teaching of mathematics, factors that the tertiary sector has no control over. The analysis also indicates the undesirable issues that are at the root of impeding success in the calculus module. Most important is that students are not encouraged to become independent thinkers from an early age. This triggers problems in follow-up courses where students are expected to have learned to deal with the work load and understanding of certain concepts. A new model was designed to lessen the impact of these undesirable issues. 相似文献
4.
Timothy W. StephensNohelli E. De La Rosa Mariam SaifullahShulin Ye Vicky ChouAmanda N. Quay William E. Acree Jr. Michael H. Abraham 《Fluid Phase Equilibria》2011,309(1):30-35
Data have been compiled from the published literature on the partition coefficients of solutes and vapors into anhydrous sulfolane. The logarithms of the water-to-sulfolane partition coefficients, log P, and gas-to-sulfolane partition coefficients, log K, were correlated with the Abraham solvation parameter model. The derived correlations described the observed log P and log K values for solutes dissolved in sulfolane to within average standard deviations of 0.14 log units or less. The log P correlation was extended to include the partition of ions by inclusion of a cation-solvent and an anion-solvent term. 相似文献
5.
Ruediger Vahldieck Wolfgang J. R. Hoefer 《International Journal of Infrared and Millimeter Waves》1987,8(7):711-721
This paper describes the analysis of dielectric resonator filters with printed tuning septum in waveguide sections operating below cutoff. In this design approach a thick dielectric slab of high permittivity is placed longitudinally in the waveguide. A bilateral ladder-shaped metallization determines the resonator and coupling sections (modified finline filter). In contrast to conventional dielectric resonator filters, this approach provides better passband separation and increased stopband attenuation. Furthermore, due to the bilateral tuning septum, the resonator and coupling sections can be manufactured accurately with photolithographic techniques rather than by expensive machining. 相似文献
6.
Hawtin P Hardern I Wittig R Mollenhauer J Poustka A Salowsky R Wulff T Rizzo C Wilson B 《Electrophoresis》2005,26(19):3674-3681
On-chip electrophoresis can provide size separations of nucleic acids and proteins similar to more traditional slab gel electrophoresis. Lab-on-a-chip (LoaC) systems utilize on-chip electrophoresis in conjunction with sizing calibration, sensitive detection schemes, and sophisticated data analysis to achieve rapid analysis times (<120 s). This work describes the utility of LoaC systems to enable and augment systems biology investigations. RNA quality, as assessed by an RNA integrity number score, is compared to existing quality control (QC) measurements. High-throughput DNA analysis of multiplex PCR samples is used to stratify gene sets for disease discovery. Finally, the applicability of a high-throughput LoaC system for assessing protein purification is demonstrated. The improvements in workflow processes, speed of analysis, data accuracy and reproducibility, and automated data analysis are illustrated. 相似文献
7.
Friedrichs O Sanchez-López JC López-Cartes C Klassen T Bormann R Fernandez A 《The journal of physical chemistry. B》2006,110(15):7845-7850
In the present work we investigate the hydrogen sorption mechanism in a MgH(2)/Nb(2)O(5) composite and analyze why Nb(2)O(5) could strongly improve hydrogen sorption kinetics in magnesium. Hereby we make use of the fact that Nb(2)O(5) nanoparticles are able to reduce the milling time significantly with the achievement of excellent sorption kinetics, and can so exclude effects occurring at long-term milling that make difficult the study of the mechanism. On the basis of extensive chemical, crystalline, and microstructural characterization of the MgH(2)/Nb(2)O(5) nanopowder system, a "pathway model" is proposed, which explains the kinetic hydrogen sorption improvement by a formation of pathways of niobium oxide species with lower oxidation state that facilitate the hydrogen transport into the sample. This mechanism is shown to be supported by additional oxidation experiments, which indicate increased oxygen diffusion through these pathways. 相似文献
8.
9.
10.