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101.
Effect of refraction index and thickness of the light guide in the position-sensitive gamma-ray detector using compact PS-PMTs 总被引:1,自引:0,他引:1
Koji Inoue Haruo Saito Yasuyuki Nagashima Toshio Hyodo Yasuyoshi Nagai Shinichi Muramatsu Shota Nagai 《Radiation Physics and Chemistry》2000,58(5-6):763-766
We constructed a position-sensitive gamma-ray detector consisting of an array of BGO scintillators, a light guide and compact PS-PMTs. The effects of refractive index and thickness of the light guide of a glass plate on the detector performance were investigated. A light guide with higher refractive index and smaller thickness is found better for a good spatial resolution. 相似文献
102.
103.
Akira Sugimoto Yasuyuki Yoshino Ryo Watanabe Kazuhiko Mizuno Kaku Uehara 《Journal of heterocyclic chemistry》1999,36(4):1057-1064
By the reaction of 5,10-dialkyl-substituted 5,10-dihydrophenazine with hydrobromic acid in dimethyl sulfoxide at 90–110°, 10-alkyl-2(10H)-phenazinone was obtained as a major product. Brominated dihydrophenazine was isolated in the case of 1,6-dichloro-5,10-dimethyl-5,10-dihydrophenazine. 相似文献
104.
We consider the dynamics of skew product maps associated with finitely generated semigroups of rational maps on the Riemann
sphere. We show that under some conditions on the dynamics and the potential function ψ, there exists a unique equilibrium state for ψ and a unique exp(P(ψ) − ψ)-conformal measure, where P(ψ) denotes the topological pressure of ψ.
The research of M. Urbański was supported in part by the NSF Grant DMS 0400481. H. Sumi thanks University of North Texas for
kind hospitality, during his stay there. 相似文献
105.
We describe herein the synthesis and properties of the novel nucleoside derivative, 4,7-diamino-2-(2-deoxy-β-d-erythro-pentofuranosyl)-2,6-dihydro-7H-2,3,5,6-tetraazabenzo[cd]azulene (1). The palladium catalyzed cross-coupling reaction of 2,4-diamino-5-iodo-7-(2-deoxy-β-d-erythro-pentofuranosyl)pyrrolo[2,3-d]pyrimidine (9) with acrylonitrile afforded 2,4-diamino-5-[(E)-1-cyano-2-ethenyl]-7-(2-deoxy-β-d-erythro-pentofuranosyl)pyrrolo[2,3-d]pyrimidine (10) in 77% yield, which was treated with NaOMe in MeOH in the presence of NaSPh to give the desired 1 in 64% yield. Whereas 1 was stable in concentrated ammonia at room temperature, it was gradually hydrolyzed in water to give 4-amino-2-(2-deoxy-β-d-erythro-pentofuranosyl)-2,6-dihydro-7H-2,3,5,6-tetraazabenzo[cd]azulen-7-one (12). Density functional calculations indicated that 12 was 20 kcal/mol more thermodynamically stable than 1 in a model study. 相似文献
106.
A 1,3,5-substituted benzene platform has been widely used in the fields of supramolecular chemistry and molecular recognition. Here, we show that 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene 6 exhibits solvent-dependent conformation in the crystalline state. Recrystallization from dichloromethane-n-pentane gave the anti conformation 6-anti, while recrystallization from methanol-acetone gave the syn conformation 6-syn, in which the three benzyl-o-carboranyl moieties are located to one side of the central benzene ring. Interestingly, one acetone molecule is captured in the π-rich space of 6-syn and two complexes facing each other encapsulate two acetone molecules in a π-rich container formed by the eight benzene rings. The inclusion involves several weak interactions, that is, T-shaped C-H···π interactions, and C-H···O and C-H···π interactions. Two C-H···O interactions involving benzylic C-H hydrogens activated by the electron-withdrawing character of the o-carborane cage and the oxygen atom of the acetone seem to be the most important. DFT calculations indicate that the binding energy for entrapment of acetone is 6.6 kcal/mol. Inclusion of acetone is achieved through not only multiple C-H···O interactions but also a number of C-H···π interactions. The third benzyl-o-carborane moiety is fixed in the syn conformation by intramolecular and intermolecular C-H···π interactions. 相似文献
107.
Kazuhiro Haraguchi Kiju Konno Kaori Yamada Yasuyuki Kitagawa Kazuo T. Nakamura Hiromichi Tanaka 《Tetrahedron》2010,66(25):4587-8669
Stereoselectivity in N-iodosuccimide (NIS)-mediated electrophilic glycosidation was examined by employing 2,4-bis-O-(trimethylsilyl)thymine and three different silyl-protected erythro-furanoid glycals 12, 16, and 18. As a result, it was found that 3,5-O-(di-t-butylsilylene)-protected 18 gave only the β-anomer (21). The remarkable stereoselectivity observed by employing 18 is discussed on the basis of its X-ray crystallographic analysis. 1-Substituted glycals gave the corresponding β-anomer, again exclusively, to provide access to 1′-branched 2′-deoxynucleosides. 相似文献
108.
The equilibrium constants [K=anti/syn] of a pair of atropisomers due to restricted rotation about Csp3-Csp2 bond for [2-(2-hydroxynaphthalen-1-yl)-3,3-dimethylindolin-1-yl](4-substituted phenyl)methanone were determined in some solvents. The presence of the effective π-π interaction was demonstrated by the correlation between the equilibrium constants (K) and the substituent effect of the phenyl groups (σp), suggesting that the ‘neutral-type’ interaction is operative. 相似文献
109.
Synthesis of a highly luminescent three-dimensional pyrene dye based on the spirobifluorene skeleton
We have synthesized a highly luminescent (log e > 5.0, F > 0.9) pyrene dye based on a spirobifluorene skeleton [2,2',7,7'-tetrakis(7-tert-butyl-1-pyrenyl)-9,9'-spirobi[9H-fluorene; 4-PySBF]. The use of spirobifluorene prevents fluorescence quenching by intramolecular energy transfer and/or electron transfer among the chromophores in the excited state. The emission spectra of 4-PySBF exhibited a red shift of 20 nm in comparison to a model compound [9,9'-dioctyl-2,7-bis(7-tert-butyl-1-pyrenyl)-9H-fluorene; 2-PyF], but its UV-Vis spectrum remained unchanged. 相似文献
110.
The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution. 相似文献