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1.
For a graph G and a positive integer m, G(m) is the graph obtained from G by replacing every vertex by an independent set of size m and every edge by m2 edges joining all possible new pairs of ends. If G triangulates a surface, then it is easy to see from Euler's formula that G(m) can, in principle, triangulate a surface. For m prime and at least 7, it has previously been shown that in fact G(m) does triangulate a surface, and in fact does so as a “covering with folds” of the original triangulation. For m = 5, this would be a consequence of Tutte's 5‐Flow Conjecture. In this work, we investigate the case m = 2 and describe simple classes of triangulations G for which G(2) does have a triangulation that covers G “with folds,” as well as providing a simple infinite class of triangulations G of the sphere for which G(2) does not triangulate any surface. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 79–92, 2003 相似文献
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The variation of the electroactivity range with composition of water+ sulphuric acid mixtures has been studied. It is shown that ferrocene provides a reference potential independent of solvent at low H2SO4 contents while polynuclear hydrocarbons fulfill the same function at high H2SO4 contents. Water+H2SO4 mixtures become more oxidizing (reduction limit) and less reducing (oxidation limit) when the H2SO4 concentration increases. 相似文献
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Marine de Person Aude Sevestre P. Chaimbault Laurent Perrot Francis Duchiron Claire Elfakir 《Analytica chimica acta》2004,520(1-2):149-158
This paper reports the use of an on-line LC–ESI–MS/MS method for the identification and quantification of di- and tripeptides in champagne wine without laborious sample pretreatment. The identification of these compounds, in their underivatised form, is based on identical retention times and ESI–MS spectra to those of reference standards. The presence of nine dipeptides (Arg–Ile, Ile–Arg, Ile–Val, Lys–Phe, Lys–Tyr, Phe–Lys, Tyr–Gln, Tyr–Lys, Val–Ile) and the absence of two tripeptides (Phe–Arg–Arg and Lys–Met–Asn) have been evidenced in the matrix. Calibration curves for each analyte were established using Phe–Arg as internal standard. The calibration curves were linear in the concentration range 0.1–10 mg L−1 with a determination coefficient, r2, better than 0.992. The accuracy for the calibration standard was estimated at between 92 and 102%. This method allows high recovery and satisfies the necessary requirements with respect to accuracy, repeatability and sensitivity. The first application of this analytical method to the measurement of di- and tri-peptides in different vintages of champagne wine is reported. Compositional changes in the peptides occurred depending on the vintage. 相似文献
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The preparation of different aminoindazoles by nucleophilic aromatic photosubstitution of nitroindazoles by amines is described. In this manner, the amino, methylamino, dimethylamino and dimethylamino substituents are introduced in 3,4,5 or 7-position. The irradiation in the presence of ethanol gives ethoxyindazoles in only four cases. Two demethylation reactions have been observed: the first one concerns the formation of methylamino derivatives starting from dimethylamine; the second one, the formation of N(H)1-indazoles by irradiation in presence of diethylamine. 相似文献
6.
Aude Fayol 《Tetrahedron》2005,61(48):11511-11519
Three-component reaction of an α-isocyanoacetamide 7, an homoallylamine 8 and an aldehyde 9 in methanol at room temperature provides oxa-bridged tricycle 4 in good to excellent yield as a mixture of two separable diastereoisomers. In this one-pot multicomponent process, one C-N, one C-O and three C-C bonds are formed with concomitant creation of five asymmetric centers and three rings. Fragmentation of epoxy-tetrahydronaphthyridine 4 affords differentially substituted 5,6,7,8-tetrahydro-1,7-naphthyridine (5, 6) depending on the reaction conditions, providing thus additional structural diversity. A one-pot three-component synthesis of 5,6,7,8-tetrahydro-1,7-naphthyridine (6) from 7, 8 and 9 is also documented. 相似文献
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Abelev BI Aggarwal MM Ahammed Z Anderson BD Arkhipkin D Averichev GS Bai Y Balewski J Barannikova O Barnby LS Baudot J Baumgart S Belaga VV Bellingeri-Laurikainen A Bellwied R Benedosso F Betts RR Bhardwaj S Bhasin A Bhati AK Bichsel H Bielcik J Bielcikova J Bland LC Blyth SL Bombara M Bonner BE Botje M Bouchet J Brandin AV Bravar A Burton TP Bystersky M Cadman RV Cai XZ Caines H Calderón de la Barca Sánchez M Callner J Catu O Cebra D Chajecki Z Chaloupka P Chattopadhyay S Chen HF Chen JH 《Physical review letters》2007,99(11):112301
We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC. 相似文献
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We report on an innovative configuration of a supercontinuum laser based on an Yb-doped nonlinear microstructured fiber. Due to this particular fiber design combining amplification and nonlinear properties, a wideband output spectrum is generated in the fiber under the Q-switched regime. By exploiting stimulated Brillouin scattering, high peak power pulses are achieved and contribute to a spectral broadening due to a nonlinear wavelength conversion process. Both infrared (1000-1200 nm) and visible (650-750 nm) spectra are generated with an average power of 200 mW. 相似文献
10.
Contribution of Cytosine‐Containing Cyclobutane Dimers to DNA Damage Produced by Photosensitized Triplet–Triplet Energy Transfer 下载免费PDF全文
Dr. Thierry Douki Izabel Bérard Aude Wack Sigrid Andrä 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(19):5787-5794
Mutagenic cyclobutane pyrimidine dimers (CPDs) can be induced in DNA through either direct excitation or photosensitized triplet–triplet energy transfer (TTET). In the latter pathway, thymines are expected to receive the excitation energy from the photosensitizer and react with adjacent pyrimidines. By using state‐of‐the art analytical tools, we provide herein additional information on the formation of cytosine‐containing CPDs. We thus determined the yield of all possible CPDs upon TTET in a series of natural DNAs with various base compositions. We show that the distribution of CPDs cannot be explained only by excitation of individual thymines. We propose that the mechanism for TTET involves at least dinucleotides as the minimal targets. The observation of the formation of cytosine–cytosine CPDs also suggests that additional pathways are involved in this photosensitized reaction. 相似文献