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11.
The behaviour of adsorbed CO on Ru(001) flat and Ru(l,1,10) stepped surfaces in the CO pressure range between 10?6 and 101 Pa has been investigated by TDS, AES, LEED and UPS. The disproportionation of CO proceeds rapidly on the stepped surface and its apparent activation energy was obtained to be 20 kJ mol?1 at nearly zero coverage. The carbon species produced by CO disproportionation show non-uniform reactivity with 18O2 and provide four CO desorption peaks in TPR spectra, which are assigned to α-C18O,ß-C18O and those derived from carbidic and graphitic carbons. At smaller carbon coverage, only α-CO and β-CO were observed, but with increasing coverage the amount of ß-CO reaches a maximum and carbidic carbon is newly formed. Further increase of carbon deposition gives graphitic carbon. The conversion from carbidic to graphitic carbon and the dissolution into the bulk took place upon heating to 1000 K. It is remarkable that very active carbon species are converted to molecular CO through the reaction with O2 even at low temperature such as 200 K. It was also confirmed that active carbon species are formed on Ru surface during COH2 reaction. 相似文献
12.
Kimio Kunimori Tomoji Kawai Tamotsu Kondow Takaharu Onishi Kenzi Tamaru 《Surface science》1974,46(2):567-576
The kinetic behaviour of sulphur segregation was studied during heat treatment of a molybdenum ribbon between 750°C and 1350°C by using an Auger electron spectroscopic technique. When the specimen is heated to high temperatures, the sulphur present as an impurity in the polycrystalline molybdenum diffuses on to the surface along grain boundaries. The intensity changes of Auger electron signals of sulphur and molybdenum showed that the rate of the diffusion remained constant until the surface was covered with a first sulphide layer in the temperature range studied. The activation energy in the initial stage of the diffusion was 26kcal/mol. High resolution Auger spectra of the sulphur were measured and explained from the density of states of MoS2. 相似文献
13.
In this article, we prove that there does not exist a symmetric transversal design which admits an automorphism group of order 4 acting semiregularly on the point set and the block set. We use an orbit theorem for symmetric transversal designs to prove our result. As a corollary of the result, we prove that there is no projective plane of order 12 admitting a collineation group of order 8. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 411–430, 2008 相似文献
14.
The parallel factor (PARAFAC) kernel matrix to analyze a sample system stimulated by more than one type of perturbation is described. PARAFAC kernel is a quantitative representation of the synchronicity and asynchronicity observed within the PARAFAC score matrices generated by carrying out two-dimensional (2D) correlation analyses. Thus, kernel matrix representation provides more intuitively understandable interpretation to the conventional PARAFAC trilinear model. In this study, the utility of PARAFAC kernel is demonstrated by the study of poly(lactic acid)-nanocomposite undergoing a structural change depending on the temperature as well as the clay content in the sample. Seemingly complicated variation of nuclear magnetic resonance (NMR) spectra induced by the change in the temperature and clay content are readily analyzed by the multiple-perturbation 2D correlation spectroscopy and PARAFAC kernel. PARAFAC kernel revealed that crystalline and amorphous structures of the PLA substantially undergo thermal deformation, and these variations are also influenced by the presence of the clay. 相似文献
15.
It is possible to synthesize poly(N-substituted maleimide) by using a chiral complex consisting of a zinc and N-diphenylmethyl-1-benzyl-2-pyrrolidinoethanamine (DPhBP). The optical specific rotations [α]43525 in obtained polymers depend on the chirality of ligands in the catalysts. In the present study, density functional theory (DFT) calculations were adopted to investigate the polymerization mechanism in detail. The bulky diphenylmethyl group in the chiral ligand is effective to enhance the formation of the product in the initiation reaction. The geometry related to the pyrrolidine ring of the chiral ligand in the Zn catalyst is responsible for determining the configuration of polymers. It was also confirmed that the bulky substituent on the N atom of the N-substituted maleimide is another factor for obtaining polymers with high [α]43525. 相似文献
16.
Volatile compounds of iridium(I): (acetylacetonato)(1,5-cyclooctadiene)iridium(I) Ir(acac)(cod), (methylcyclopentadienyl)
(1,5-cyclooctadiene)iridium(I) Ir(Cp’)(cod), (pentamethylcyclopentadienyl)(dicarbonyl) iridium(I) Ir(Cp*)(CO)2 and (acetylacetonato)(dicarbonyl)iridium(I) Ir(acac)(CO)2 were synthesized and identified by means of element analysis, NMR-spectroscopy, mass spectrometry.
Thermal properties in solid phase for synthesized iridium(I) complexes were studied by means of thermogravimetric analysis
in inert atmosphere (He). By effusion Knudsen method with mass spectrometric registration of gas phase composition the temperature
dependencies of saturated vapor pressure were measured for iridium(I) compounds and the thermodynamic characteristics of vaporization
processes enthalpy ΔH
T* and entropy ΔS
T0 were determined. The energy of intermolecular interaction in the crystals of complexes was calculated. 相似文献
17.
Kenzi Hori Hiroshi Tsukube 《Journal of inclusion phenomena and macrocyclic chemistry》1998,32(2-3):311-329
Our strategy for designing new receptor molecules specific for Li+ ions is to combine two methods, theoretical calculations and the experimental technique. In developing the Li+ ion-specific receptors, we regarded crown ether derivatives of a 12-membered ring and side arms with functional groups as building blocks. This strategy worked well to synthesize new receptor molecules which selectively bind and transport the Li+ ion. 相似文献
18.
Molecular geometries of crown ether derivatives play an important role in capturing and transporting alkali metal ions such as Li+ and Na+. As selectivity of the ions is observed in solution, it is necessary to know their molecular structures in solutions. Recently, we investigated stable conformations of 12-crown-O3N and its alkali ion complexes in aqueous and acetonitrile solutions. In the present study, we applied a procedure similar to that in previous papers to investigate the side arm effect of 12-crown-O3N with an amine arm for capturing Li+ and Na+ in the two solutions. It was confirmed that the stable structures of Li+ and Na+ complexes in solutions, especially the geometry of the amine side arm, are highly solvent-dependent. This conformational difference is the key to understanding the high Li+ selectivity of 12-crown-O3N derivatives with an amine side arm in acetonitrile. 相似文献
19.
Hiroyuki Akita Katsumi Kurashima Masako Nozawa Shigeo Yamamura Kenzi Seri Yorishige Imamura 《Tetrahedron: Asymmetry》1998,9(24):269-4340
Enantioselective acetylation of (±)-4-(1-hydroxyethyl)benzenesulfonamide 6 with ‘Acylase I’ (No. A 2156) from Aspergillus melleus in the presence of vinyl acetate gave (R)-4-(1-acetoxyethyl)benzenesulfonamide 7 (98% ee) and (S)-6 (98% ee). Both (S)-6 and (R)-7 were individually converted to the (S)-hydroxyhexamide 2 (>99% ee) and (R)-hydroxyhexamide 2 (>99% ee), respectively. The absolute configuration of a metabolite (−)-hydroxyhexamide 2 from acetohexamide 1 was found to be S based on unequivocal chemical methods including X-ray analysis. 相似文献
20.
Isamu Inamura† Hideo Ochiai‡ Kenzi Toki Sachiko Watanabe Satomi Hikino Takeo Araki 《Photochemistry and photobiology》1983,38(1):37-44
Abstract— As an artificial model compound of the chlorophyll-protein complex in vivo , the chlorophyll/water-soluble macromolecular complexes were prepared by using synthetic linear polymers of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), and a natural polymer of bovine serum albumin (BSA). By the method described here, it is possible to prepare an aqueous chlorophyll (Chl)-macromolecular complex solution of a desired Chi aggregate, such as: Chi a (670), Chi a (740) and Chi b ; and with a desired relative content and concentration. These procedures for preparing such complexes will have wide applicability for technical use in Chi studies. For example, extremely diluted aqueous complex solutions of at least 1 × 10-4% wt Chi a (670 or 740)-macromolecular complex / wt can be obtained without changing the spectral features. From viscosity measurements, the structures of the complexes were inferred: (1) for a linear macromolecular (PVA or PVP) complex, a Chi species is tightly surrounded by a chain of the polymer causing shrinkage of the chain; (2) globular BSA molecules surround Chi species to form a large complex. The mechanism of stabilization of Chi aggregates in thylakoid membrane was discussed concerning an analogy to the complexes studied here. 相似文献