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W. Hugh Woodin 《Archive for Mathematical Logic》2016,55(1-2):319-351
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Thominet O Baker JR Britton H Etheridge ZC Soscia MG Caddick S 《Organic & biomolecular chemistry》2007,5(22):3703-3712
We present herein our recent efforts towards the synthesis of epoxydiynes which represent an unusual structural feature of the neocarzinostatin chromophore. A number of different routes to these epoxydiynes have been explored with varying success. Ultimately a concise and convergent approach was developed, which involved the addition of an allenyl zinc bromide to propargylic ketones/aldehydes followed by epoxide formation. This new protocol enabled us to synthesise a fully elaborated epoxydiyne which will find application for our studies towards the total synthesis of the NCS chromophore. 相似文献
105.
García-Zubiri IX Burrows HD Seixas de Melo JS Pina J Monteserín M Tapia MJ 《Photochemistry and photobiology》2007,83(6):1455-1464
The complexation of beta-carboline-3-carboxylic acid N-methylamide (betaCMAM) with the sodium salts of the nucleotides polyadenylic (Poly A), polycytidylic (Poly C), polyguanylic (Poly G), polythymidylic (Poly T) and polyuridylic (Poly U) acids, and with double stranded (dsDNA) and single stranded deoxyribonucleic acids (ssDNA) was studied at pH 4, 6 and 9. Predominant 1:1 complex formation is indicated from Job plots. Association constants were determined using the Benesi-Hildebrand equation. BetaCMAM-sensitized singlet oxygen quantum yields were determined at pH 4, 6 and 9, and the effects on this of adding oligonucleotides, dsDNA and ssDNA were studied at the three pH values. With dsDNA, the effect on betaCMAM triplet state formation was also determined through triplet-triplet transient absorption spectra. To evaluate possible oxidative damage of DNA following singlet oxygen betaCMAM photosensitization, we used thiobarbituric acid-reactivity assays and electrophoretic separation of DNA assays. The results showed no oxidative damage at the level of DNA degradation or strand break. 相似文献
106.
Pina J de Melo JS Burrows HD Batista RM Costa SP Raposo MM 《The journal of physical chemistry. A》2007,111(35):8574-8578
A comprehensive study has been made in solution at room temperature (293 K), low temperature (77 K), and in thin films (Zeonex matrixes) of the spectral and photophysical properties of six arylthienyl- and bithienyl-benzothiazole derivatives functionalized with different donor groups. Similar experiments have been carried out with two related precursors (containing the arylthienyl and aryl-bithienyl conjugated systems), and results are compared. Singlet-singlet and triplet-triplet absorption spectra, emission spectra together with lifetimes and quantum yields have been obtained, and from these data the rates for all the radiative and nonradiative processes determined, providing information on the dominant decay processes. The arylthienyl-benzothiazole derivatives show high fluorescence quantum yields (phi(F)) with negligible internal conversion (phi(IC)), whereas the bithienyl-benzothiazoles display lower but still significant phi(F) values, but now radiationless processes (phi(IC) and phi(ISC)) are competitive. A comparison with the analogous oligothiophenes is made. Singlet oxygen yields were also determined and the triplet energy transfer to (3)O2 to produce (1)O2 was found to be highly efficient with values of S(Delta)(= phi(Delta)/phi(T)) varying from 0.4 to 1. 相似文献
107.
An opinion function on a graph G = (V, E) is a function f: V → {−1, +1}. The vote of a vertex v is the sum of these function values over the closed neighborhood of v. A strict majority function on a graph G is an opinion function for which more than half of the vertices have a positive vote. The strict majority number of G is the minimum sum of the values in a strict majority function of G. We prove the conjecture of Cockayne and Mynhardt (Ars. Combin. 43 (1996), 235–245) that every tree has strict majority number at most 2. We also prove that every graph has strict majority number at most 4. Both bounds are sharp. © 1998 John Wiley & Sons, Inc. J Graph Theory 28: 49–56, 1998 相似文献
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Hugh L. Huffman Jr. Robert J. Lemire Paul G. Sears 《Journal of solution chemistry》1983,12(8):563-571
The conductance behavior of twenty-five 1∶1 electrolytes has been investigated in 3-methyl-2-oxazolidone (3Me20x) at 25°C. Conductance data were analyzed by the Lee-Wheaton equation, and all salts studied were found to be only slightly associated. Ionic limiting equivalent conductances were obtained using tris(iso-pentyl)butylammonium tetraphenylborate as a reference electrolyte. The relative values of the ionic limiting molar conductance are generally similar to those for other dipolar aprotic solvents. However, the order $$\lambda _0 (i - Pent_3 BuN^ + ) > \lambda _0 (Pent_4 N^ + )and\lambda _0 (Br^ - ) > \lambda _0 (ClO_4^ - )$$ is opposite to that found previously in the similar solvent 3-tert-bytyl-2-oxazolidone. 相似文献