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101.
102.
The reconstruction numberrn(G) of a graphG was introduced by Harary and Plantholt as the smallest number of vertex-deleted subgraphsG
i
=G – v
i
in the deck ofG which do not all appear in the deck of any other graph. For any graph theoretic propertyP, Harary defined theP-reconstruction number of a graph G P as the smallest number of theG
i
in the deck ofG, which do not all appear in the deck of any other graph inP We now study the maximal planar graph reconstruction numberrn(G), proving that its value is either 1 or 2 and characterizing those with value 1. 相似文献
103.
Grosnick D Wright SC Bolton RD Cooper MD Frank JS Hallin AL Heusi PA Hoffman CM Hogan GE Mariam FG Matis HS Mischke RE Piilonen LE Sandberg VD Sanders GH Sennhauser U Werbeck R Williams RA Wilson SL Hofstadter R Hughes EB Ritter MW Highland VL McDonough J 《Physical review letters》1986,57(26):3241-3244
104.
105.
Zhao Y Slepkov AD Akoto CO McDonald R Hegmann FA Tykwinski RR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,11(1):321-329
Monodisperse, cross-conjugated perphenylated iso-polydiacetylene (iso-PDA) oligomers, ranging from monomer 15 to pentadecamer 25, have been synthesized by using a palladium-catalyzed cross-coupling protocol. Structural characteristics elucidated by X-ray crystallographic analysis demonstrate a non-planar backbone conformation for the oligomers due to the steric interactions between alkylidene phenyl groups. The electronic absorption spectra of the oligomers show a slight red-shift of the maximum absorption wavelength as the chain length increases from dimer 17 b to pentadecamer 25, a trend that has saturated by the stage of nonamer 22. Fluorescence spectroscopy confirms that the pendent phenyl groups present on the oligomer framework enhance emission, and the relative emission intensity consistently increases as a function of chain length n. The molecular third-order nonlinearities, gamma, for this oligomer series have been measured via differential optical Kerr effect (DOKE) detection and show a superlinear increase as a function of the oligomer chain length n. Molecular modeling and spectroscopic studies suggest that iso-PDA oligomers (n>7) adopt a coiled, helical conformation in solution. 相似文献
106.
The recently discovered intramolecular aza-xylylene Diels-Alder reaction, based on a 1,4-dehydrohalogenation reaction, was extended in terms of substrates and leaving groups allowing the assembly of tetrahydroquinolines in two synthetic steps. Intramolecular cleavage of a thiocarbamate using triphenylphosphine and tetrachloromethane (Appel conditions) to give chloromethyl phenylisocyanate has been presented for the first time. The synthetic feasibility of this process was demonstrated in the first total syntheses of the alkaloids rac-Angustureine and 1-methyl-2-propyltetrahydroquinoline. 相似文献
107.
Progress and developments made in microwave-assisted combinatorial synthesis and library production since 2002 are reviewed. The use of microwave technology in both solution and solid phase synthesis is discussed with special reference to agrochemical applications where appropriate. 相似文献
108.
The synthesis of a biotinated amphiphile assembled from d-(+)-biotin, ethylene diamine as spacer, galactaric acid and 1-dodecylamine was achieved in six steps. The key step was the synthesis of a bisacetonide protected galactaric ester, the structure of which was determined by X-ray analysis. Aminolysis, spacer attachment, coupling with biotin and deprotection led to the amphiphilic galactaramide. 相似文献
109.
The stoichiometric pK
1
*
and pK
2
*
for the ionization of carbonic acid has been determined from emf measurements in NaCl soluions to 6.0m at 25°C. Our results at low concentrations are in good agreement with the results of Harned and Bonner, of Dyrssen and Hansson and of Roy et al. The calculated values of pK
1
*
using Pitzer's equations agree with the measured values to ±0.01 pK units provided higher order terms are used. It was necessary to use a triplet interaction parameter () and higher order electrostatic terms (E) to calculate reliable values of pK
2
*
(±0.03 pK units) over the entire concentration range. These results demonstrate the reliability of the Pitzer equations to estimate activity coefficients in concentrated salt solutions. 相似文献
110.
Xiong C Zhang J Davis P Wang W Ying J Porreca F Hruby VJ 《Chemical communications (Cambridge, England)》2003,(13):1598-1599
Novel constrained beta-turn dipeptide mimetics, 8-phenyl thiaindolizidinone amino acids 3, have been synthesized stereoselectively and incorporated into Leu-enkephalin peptides as a replacement of dipeptide Gly3-Phe4 to afford four individual isomers of Leu-enkephalin analogues 6. 相似文献