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A nonperturbative picture ofN \(\bar N\) annihilation is proposed. In particular, different parts of the nucleon and the antinucleon do not behave independently, but are tied together by their topological charge. We describe theN \(\bar N\) state as a coherent soliton-antisoliton configuration, and argue that vector mesons play an important role in the decay process. SomeS-wave selection rules are derived. Their relevance to the present LEAR experiments is discussed. 相似文献
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Seyed Mojtaba Amininasab Soheila Esmaili Mehdi Taghavi Zahed Shami 《International Journal of Polymer Analysis and Characterization》2016,21(8):686-696
A series of novel organosoluble polyamides (PAs) bearing different functional groups such as flexible ether, substituted imidazole, and xanthene rings and electron-withdrawing CF3 groups were synthesized from diamines and various dicarboxylic acids. The structures of diamines and PAs were fully characterized by elemental analysis, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectroscopy. The PAs showed good solubility in aprotic and polar organic solvents, with high thermal stability exhibiting the glass transition temperatures (Tgs) and 10% weight loss temperatures (T10%) in the range of 184–277°C and 410–480°C in N2 atmosphere, respectively. These polymers showed fluorescence emission upon irradiation with UV light. Diamine compounds and two of synthesized polymers were also screened for antibacterial activity against gram-positive and gram-negative bacteria, and the obtained results for all four combinations showed good inhibition. Extraction capability for heavy metal ions such as Cr3+, Pb2+, Hg2+, Cd2+, and Co2+ from aqueous solutions was also tested at 25°C and pH 7–8. 相似文献
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Thiocarbonyldiimidazole has been found to be an efficient acid activator for the synthesis of β-lactams by ketene-imine cycloaddition at room temperature. The experimental procedure is simple and results in excellent yields of the products. All products were characterized by spectral data and elemental analyses. 相似文献
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Three diamine monomers with different derivatives of imidazole heterocyclic ring, aryl ethers and electron withdrawing trifluoromethyl groups in the backbone were synthesized and used in polycodensation reaction with various aliphatic and aromatic dicarboxylic acids for preparation of a series of novel polyamides(PAs). The PAs were obtained in high yields and possessed inherent viscosities in the range of 0.26-0.75 d L/g. All of the polymers were amorphous in nature,showed outstanding solubility and could be easily dissolved in amide-type polar aprotic solvents. They showed good thermal stability with glass transition temperatures between 162-302 ℃. Thermogravimetric analysis showed that all polymers were stable, with 10% weight loss recorded above 421 ℃ in N_2 atmospheres. All the PAs presented fluorescence upon irradiation with ultraviolet light and thus showed promise for applications in electroluminescent devices. The monomers and PAs were also screened for antibacterial activity against Gram positive and Gram negative bacteria. 相似文献
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Mohammed M. Hashemi Hossein Ghafuri Zahed Karimi-Jaberi 《Monatshefte für Chemie / Chemical Monthly》2006,137(2):197-200
Summary. Various alkyl, aryl, and heterocyclic Hantzsch 1,4-dihydropyridines were converted to the corresponding pyridines in excellent yields and short times using sodium nitrite
in the presence of a catalytic amount of acidic silica gel at room temperature. 相似文献
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