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61.
A submodular polyhedron is a polyhedron associated with a submodular function. This paper presents a strongly polynomial time algorithm for line search in submodular polyhedra with the aid of a fully combinatorial algorithm for submodular function minimization. The algorithm is based on the parametric search method proposed by Megiddo. 相似文献
62.
Koichi Nagano 《Archiv der Mathematik》2007,88(2):173-180
We construct several non-trivial examples of CAT(1) spaces by using the idea of free construction.
Received: 29 August 2005
Partially supported by the MEXT Grant-in-Aid for scientific research, and by the 2004 JSPS
Postdoctoral Fellowships for Research Abroad. 相似文献
63.
64.
Superoxide, which was produced by an electrochemical method, catalyzes instantaneously the interchange reaction of disulfides. The relationship between the half-wave potentials of disulfides and the amounts of superoxide required to complete the reaction were examined. 相似文献
65.
Standard enthalpies of formation of amorphous platinum hydrous oxide PtH2.76O3.89 (Adams' catalyst) and dehydrated oxide PtO2.52 at T=298.15 K were determined to be -519.6±1.0 and -101.3 ±5.2 kJ mol-1, respectively, by micro-combustion calorimetry. Standard enthalpy of formation of anhydrous PtO2 was estimated to be -80 kJ mol-1 based on the calorimetry. A meaningful linear relationship was found between the pseudo-atomization enthalpies of platinum
oxides and the coordination number of oxygen surrounding platinum. This relationship indicates that the Pt-O bond dissociation
energy is 246 kJ mol-1 at T=298.15 K which is surprisingly independent of both the coordination number and the valence of platinum atom. This may provide
an energetic reason why platinum hydrous oxide is non-stoichiometric.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
66.
Abstract— The aerobic xanthine oxidase reaction causes the co-oxidation of 2,5-dimethylfuran to cis-diacetylethylene and the bleaching of rubrene tetracarboxylate. These actions were suppressed by superoxide dismutase, catalase, desferoxamine and by benzoate and other hydroxyl radical scavengers. The bleaching of rubrene tetracarboxylate was not enhanced in D20. These results suggest that OHv, generated from O2- plus H2O2 by an iron-catalyzed Haber Weiss reaction, was the responsible agent and that singlet oxygen was not detectably involved. Control experiments, in which singlet oxygen was generated photochemically, demonstrated that replacement of H2O by D2O caused the expected enhancement of the chemical reactivity of singlet oxygen under the conditions of these experiments and that O2-, at concentrations achieved by the xanthine oxidase reaction, did not detectably quench singlet oxygen. We conclude that singlet oxygen, if produced at all during the aerobic xanthine oxidase reaction, cannot exceed 0.1% of the production of O2-. 相似文献
67.
Tohru Sakakibara Kiyotaka SuzukiAkiko Sakai Miwa ShindoChihiro Nagano Shinya NarumiYasuhiro Kajihara Katsura Mochizuki 《Tetrahedron letters》2003,44(30):5711-5714
Methyl 4,6-O-benzylidene-2,3-dideoxy-3-C-p-tolylsulfonyl-2-C-p-tolylthio-β-d-glucopyranoside and its 5a-carba-dl-analog exit mainly in a non-chair conformation in solutions, but the latter occupies a chair conformation in a solid state. 相似文献
68.
Stübiger G Marchetti M Nagano M Grimm R Gmeiner G Reichel C Allmaier G 《Journal of separation science》2005,28(14):1764-1778
The structural characterization of the O- and N-glycan structures of three different commercially available recombinant human erythropoietins (rhEPOs) is represented by means of a microscale sample purification using ZipTip technology and MALDI-TOF and MALDI low-energy CID MS. Glycopeptides were released from rhEPO samples by a differential endoproteolytic digestion to obtain site-specific glycosylation patterns. Mass accuracies in the range of +/- 0.04% obtained by the high-resolution TOF instrument allowed an unambiguous assignment of N-glycan structures via glycan database software. Furthermore, the O-glycan structures were directly analyzed on the glycopeptide level by MS/MS experiments. Principally, site-specific glycosylation was found to be very similar for the three different rhEPOs (EPO-alpha, EPO-beta, and novel erythropoiesis stimulating protein (NESP)) but exhibiting quantitative differences in distinct O- and N-glycan moieties. Significant differences were found in the degree of sialylation and acetylation. Especially, a considerable degree of variation of the O-acetylation of sialic acid residues could be realized on the glycan structures of O- and N-glycopeptides, whereas EPO-alpha and EPO-beta could be clearly differentiated from NESP solely on the O-glycopeptide level. 相似文献
69.
We have studied oxidation reactions using a synthetic heme-thiolate (SR complex) in order to ascertain the contributions of multiple intermediates derived from heme-thiolate to the oxygen atom transfer reaction to substrate. First, degradation of peroxyphenylacetic acid (PPAA) was examined in the presence of various substrates. The O-O bond cleavage mode of PPAA was clearly dependent on the reactivity of the substrate, and an easily oxidizable substrate enhanced heterolytic O-O bond cleavage. Second, competitive oxidations of cyclooctane and cyclooctene were carried out with various peroxybenzoic acids containing a series of substituents at the para-position as an oxygen source. The ratios of alkane hydroxylation rate/alkene epoxidation rate were dependent on the nature of the para-substituent of the oxidant. We conclude that substrate and oxidant interact with each other during the oxygen atom transfer reaction, that is, oxidation reaction occurs before O-O bond cleavage, even in the reaction catalyzed by heme-thiolate, which is considered to promote O-O bond cleavage. The results of an (18)O-incorporation study that is frequently performed to determine the active intermediates derived from iron porphyrins were consistent with this conclusion. 相似文献
70.
Tris(acetylacetonato)iron(III) (Fe(acac)(3)) was found to be an efficient catalyst for the cross-coupling reaction between aryl Grignard reagents and alkyl halides possessing beta-hydrogens. The reaction is applicable to secondary alkyl halides as well as primary ones. [reaction: see text] 相似文献