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21.
Periodica Mathematica Hungarica - Let X 1,X 2,... be a sequence of independent and identically distributed random variables, and put % MATHTYPE!MTEF!2!1!+-%... 相似文献
22.
Ioan Tomescu 《Journal of Graph Theory》2003,43(3):210-222
In the set of graphs of order n and chromatic number k the following partial order relation is defined. One says that a graph G is less than a graph H if ci(G) ≤ ci(H) holds for every i, k ≤ i ≤ n and at least one inequality is strict, where ci(G) denotes the number of i‐color partitions of G. In this paper the first ? n/2 ? levels of the diagram of the partially ordered set of connected 3‐chromatic graphs of order n are described. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 210–222, 2003 相似文献
23.
3族新的不含紧优与几乎紧优的有向双环网络无限族 总被引:2,自引:0,他引:2
给出了3族新的不含紧优与几乎紧优的有向双环网络. 相似文献
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Wu J Huang J Xiao Q Zhang S Xiao Z Li Q Long L Huang L 《Magnetic resonance in chemistry : MRC》2004,42(7):659-662
Ten phenylethanoid glycosides, including two new ones, isolated from the aerial parts of the mangrove plant Acanthus ilicifolius were identified. The first complete assignments of the 1H and 13C NMR chemical shifts for these glycosides were achieved by means of 2D NMR techniques, including 1H-1H COSY, TOCSY, HSQC and HMBC spectra. 相似文献
26.
We consider the statistical mechanics of the traveling salesman problem (TSP) and develop some representations to study it. In one representation the mean field theory has a simple form and brings out some of the essential features of the problem. It shows that the system has spontaneous symmetry breaking at any nonzero temperature. In general the phase progressively changes as one decreases the temperature. At low temperatures the mean field theory solution is very sensitive to any small perturbations, due to the divergence of some local susceptibilities. This critical region extends down to zero temperature. We perform the quenched average for a nonmetric TSP in the second representation and the resulting problem is more complicated than the infinite-range spin-glass problem, suggesting that the free energy landscape may be more complex. The role played by frustration in this problem appears explicitly through the localization property of a random matrix, which resembles the tight binding matrix of an electron in a random lattice. 相似文献
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James Y. Becker Larry L. Miller Frank R. Stermitz 《Journal of Electroanalytical Chemistry》1976,68(2):181-191
The electrochemical oxidation of the alkaloid laudanosine (Ia) to O-methylflavinantine (II) has been studied in acetonitrile solvent. Using cyclic voltammetry, rotating disc voltammetry and preparative electrolyses on several alkaloids, simple aliphatic amines and aromatic compounds, some aspects of the mechanism of this coupling reaction are elucidated. The first anodic wave for laudanosine at platinum has Ep=0.55 V vs. Ag/Ag+. The electrode rapidly becomes partially passivated at potentials above 0.5 V. This is due to a film which “dissolves” below 0.5 V, at a rate independent of the potential. It is shown that the reaction (Ia)→(II) proceeds at 0.5 V by initial oxidation of the amine moiety. If acids such as sodium bicarbonate are added to the anolyte the amine is protonated causing the first wave to disappear. Oxidation at 1.1 V under these acidic conditions produces the same product, but more rapidly and in significantly higher yield because electrode filming and side reactions resulting from the amine oxidation are abrogated. 相似文献
30.
A systematic study of the adsorption and interfacial behaviour of the adenine mono-nucleotides (5′-AMP, 3′-AMP, cyclic 3′,5′-AMP, 5′-ADP and 5′-ATP) and adenosine for comparison at the HMDE has been carried out at pH 3.4 to 3.5. Thus, the N(1) of the adenine moiety is protonated to a major extent.The adsorption was followed by single sweep voltammetry (measurement of the time integral of the reduction peak of the adsorbed adenine moiety) and by a.c. voltammetry (out-of-phase component of the a.c. response being proportional to the differential double layer capacity). In this paper the situation corresponding to a “dilute” adsorption layer existing at low bulk concentrations is studied for various degrees of coverage. The potential dependence of the coverage is of bell shaped type with an extended maximum region around the potential of electrocapillary maximum (Eecm) of the blank. For the same bulk concentration the coverage decreases in the series AMP, ADP, ATP, i.e. with increasing negative charge of the nucleotide, and at the same time the potential range of adsorption narrows. Among the monophosphates the coverage decreases in the series 3′-AMP, 5′-AMP, cyclic 3′,5′-AMP. The variations are connected with the varying charge of the mononucleotides and with the possibilities for interactions with adjacent molecules in the adsorption layer.At elevated bulk concentrations above a threshold value a substantial increase in coverage occurs around Eecm as due to strong interactions between the adsorbed base moieties a rather compact film is formed. 相似文献