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L. Hand D. Petersen H. Scott K. Gottfried M. Atac A. L. Read L. Voyvodic W. Czyż B. Furmańska R. Holyński A. Jurak S. Krzywdzinski G. Nowak H. Wilczyński W. Wolter B. Wosiek R. Ball J. Kiley A. Kotlewski L. Litt J. Florian J. J. Lord R. J. Wilkes 《Zeitschrift fur Physik C Particles and Fields》1979,1(2):139-142
An experimental search is presented for the existence of intra-nuclear cascading which, for small values of the Bjorken scaling variable ω, is the only mechanism of particle multiplication in the target nucleus. Our data indicate that cascading does exist as one of the effective mechanisms of particle multiplication in μ-nucleus collisions. No significant variation of the observed multiplicity with ω is observed. 相似文献
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Gabrielle McMullen Gottfried Sedelmeier Rainer Hildebrand Hans Fritz Horst Prinzbach 《Tetrahedron letters》1979,20(40):3847-3850
Tris-[2.2.1]- and tris-[2.2.2]-σ-homobenzenes are synthesised by reaction of 1,1′-bicyclobutenyl with appropriate dienophiles and hydrogenation of the adducts. 相似文献
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Gregor W Grabner G Adelwöhrer C Rosenau T Gille L 《The Journal of organic chemistry》2005,70(9):3472-3483
[structure: see text] Chromanol-type compounds act as antioxidants in biological systems by reduction of oxygen-centered radicals. Their efficiency is determined by the reaction rate constants for the primary antioxidative reaction as well as for disproportionation and recycling reactions of the antioxidant-derived radicals. We studied the reaction kinetics of three novel chromanols: cis- and trans-oxachromanol and the dimeric twin-chromanol, as well as ubichromanol and ubichromenol, in comparison to alpha-tocopherol and pentamethylchromanol. The antioxidant-derived radicals were identified by optical and electron spin resonance spectroscopy (ESR). The kinetics of the primary antioxidative reaction and the disproportionation of the chromanoxyl radicals were assessed by stopped-flow photometry in different organic solvents to simulate the different polarities associated with biomembranes. Furthermore, the reduction of the chromanoxyl radicals by ubiquinol and ascorbate was measured after laser-induced one-electron chromanol oxidation in ethanol and in a micellar system, respectively. The rate constants showed that twin-chromanol had better radical scavenging properties than alpha-tocopherol and a significantly slower disproportionation rate of its corresponding chromanoxyl radical. In addition, the radical derived from twin-chromanol is reduced by ubiquinol and ascorbate at a faster rate than the tocopheroxyl radical. Finally, twin-chromanol can deliver twice as many reducing equivalents, which makes this compound a promising new candidate as artificial antioxidant in biological systems. 相似文献