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51.
52.
Ken-Ichi Kawarabayashi 《Discrete Mathematics》2007,307(6):764-768
We prove that for any orientable surface S and any non-negative integer k, there exists an integer fS(k) such that every graph G embeddable in S has either k vertex-disjoint odd cycles or a vertex set A of cardinality at most fS(k) such that G-A is bipartite. Such a property is called the Erd?s-Pósa property for odd cycles. We also show its edge version. As Reed [Mangoes and blueberries, Combinatorica 19 (1999) 267-296] pointed out, the Erd?s-Pósa property for odd cycles do not hold for all non-orientable surfaces. 相似文献
53.
Terai T Osakabe K Katai M Sakaguchi K Narama I Matsuura T Katakawa J Tetsumi T 《Chemical & pharmaceutical bulletin》2003,51(3):351-353
Novel 9alpha and 9beta-hydroxy grayanotoxin II derivatives were prepared by photo-sensitized oxygenation of iso-grayanotoxin II and oxidation of grayanotoxin II tetraacetate with selenium dioxide respectively. The lethal dosage of 9alpha and 9beta-hydroxy grayanotoxin II were lower than that of grayanotoxin II. In addition, the lethal dosage of 9beta-hydroxy-dihydro grayanotoxin II was higher than that of dihydro grayanotoxin II. 相似文献
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55.
Abstract New liquid crystalline (LC) homo- and copolymethacrylates having a carbonate linkage between a benzylideneaniline mesogen and ethylene chain in the side chain were prepared by free radical polymerization of methacrylate derivatives comprising 4-cyano- and/or 4-methoxybenzylide-neaniline units using AIBN as an initiator. The structures of the polymers were characterized by FTIR, 1HNMR, and elemental analyses. The LC properties were evaluated by differential scanning calorimetry (DSC), polarizing microscopic observation of textures and X-ray diffraction. These measurements showed that all the homo- and copolymers form nematic phases. The isotropization temperatures on composition exhibited a negative deviation from a linear relationship between them predicted by the Schroeder-Van Laar equation. This phenomenon might be caused mainly by an unusual geometry arising from a smaller bond angle in the carbonate linkage. 相似文献
56.
The adsorbed state of nitrogen on Ru catalysts was studied by a TPD technique combined with an isotopic technique. (1) A molecular and an atomic species on Ru powder, (2) a molecular and three atomic species on Raney-Ru, and (3) two molecular and probably three atomic species on Raney-Ru/K were identified, respectively. Relations between the adsorbed states and those reactivities for an isotopic equilibration reaction of N2 were discussed. 相似文献
57.
Ioan Balint Akane Miyazaki Ken-ichi Aika 《Reaction Kinetics and Catalysis Letters》2005,85(1):189-196
Summary Well-defined platinum nanocrystals (» 52% cubic), with an average diameter of 12 nm, were prepared by colloid method and then supported on alumina. The effect of the exposed Pt surface on lean de-NOx reaction was investigated. The catalytic data free of transport effects were identified and then used to calculate the kinetic parameters of lean de-NOx reaction. 相似文献
58.
Two manganese(III) tetradentate Schiff-base dimers to which N,N'-dicyano-1,4-naphthoquinonediiminate (DCNNQI) radicals are attached have been selectively synthesized by varying the solvents used in the reactions: [Mn2(5-MeOsaltmen)2(DCNNQI)2].MeOH (1) and [Mn2(5-MeOsaltmen)(2)(DCNNQI)(2)] x 2CH2Cl2.2CH3CN (2) [5-MeOsaltmen2- = N,N'-(1,1,2,2-tetramethylethylene)bis(5-methoxysalicylideneiminate)]. These two complexes share the same molecular core, [(DCNNQI.-)-Mn(III)-(O)2-Mn(III)-(DCNNQI.-)], where -(O)2- is a biphenolate bridge in the out-of-plane dimerized [Mn(2)(5-MeOsaltmen)2]2+ moiety. However, their packing arrangements are completely different. Whereas complex 1 is found to be relatively isolated, strong intermolecular dimerization of the DCNNQI moieties (with the nearest contact being approximately 3.0 A) is observed in 2, forming a one-dimensional chain of [-Mn(III)-(O)2-Mn(III)-(DCNNQI.-)2-](infinity). The magnetic susceptibility of 1 can be modeled with an [S = 1/2, 2, 2, 1/2] four-spin system including strong antiferromagnetic Mn(III)/DCNNQI radical coupling (J(Mn/rad)/kB = -23 K) and ferromagnetic Mn(III)/Mn(III) coupling through the biphenolate bridge (J(Mn/Mn)/kB = +2.0 K). These interactions lead to an ST = 3 ground state that possesses significant uniaxial anisotropy (D(S=3)/kB = -2.1 K). Low-temperature ac and dc magnetic data of 1 reveal its single-molecule magnet behavior with quantum tunneling of the magnetization. By contrast, 2 possesses the diamagnetic ground state induced by dominating Mn(III)-Mn(III) antiferromagnetic interactions mediated by the diamagnetic DCNNQI dimers and/or pi-pi contact along the b axis. 相似文献
59.
Torimoto T Adachi T Okazaki K Sakuraoka M Shibayama T Ohtani B Kudo A Kuwabata S 《Journal of the American Chemical Society》2007,129(41):12388-12389
Nanoparticles of ZnS-AgInS2 solid solution (ZAIS) were synthesized by the thermal decomposition of (AgIn)xZn2(1-x)(S2CN(C2H5)2)4 precursors in a hot oleylamine solution. X-ray powder diffraction analyses revealed that the resulting nanoparticle powders were not a mixture of ZnS and AgInS2 but a ZnS-AgInS2 solid solution in which the fraction of ZnS was enlarged with a decrease in the value of x, that is, an increase in the content of Zn2+ in the precursors used. The energy gap of ZAIS nanoparticles could be controlled by the composition of solid solution. Intense emission was observed at room temperature, regardless of the kind of the particles, the peak wavelength of PL being blue-shifted from 720 to 540 nm with a decrease in the value of x. The highest quantum yield of ca. 24% was obtained for nanoparticles prepared with x = 0.86, which was much higher than the quantum yields reported for I-III-VI2-based semiconductor nanoparticles, such as CuInS2 and ZnS-CuInS2 solid solution. 相似文献