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A Gurtu P K Malhotra I S Mittra P M Sood SC Gupta VK Gupta GL Kaul LK Mangotra Y Prakash NK Rao ML Sharma 《Pramana》1974,3(5):311-322
This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR em = 〈n s〉/〈n ch〉, where 〈n ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R em = 1·71 implies an effectiveA-dependence ofR A =A 0.18,i.e., a very weak dependence. Predictions ofR em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production. 相似文献
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The synthesis of three stereoisomers of a major homologue of the methoxymycolic acids present in Mycobacterium tuberculosis is described. 相似文献
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Anderson S Taylor PN Verschoor GL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(2):518-527
Four linear benzofuran trimers have been prepared by a two-stage synthetic procedure. They were tested as materials for organic electroluminescence (OEL). Precursor phenylene ethynylene oligomers were formed in the first stage, then after removal of the phenolic hydroxyl protecting groups, a base was used to promote the cyclization of ortho-hydroxy phenylene ethynylenes to benzofurans. Both acetate esters and tert-butyl carbonates were employed as protecting groups. tert-Butyl and n-hexyl substituents on the benzofurans were used to modulate solubility, aggregation, and film-forming properties; two tert-butyl groups prevented aggregation in the solid state, thus maintaining emission in the blue region of the visible spectrum. The OEL characteristics of the tert-butyl-substituted benzofuran trimer were explored, and blue emission was observed. The two-stage synthetic procedure employed for the preparation of these benzofuran trimers may be applied to a wide variety of benzofuran oligomer and polymer targets. 相似文献
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