Solid state NMR characterization of formation of poly(ϵ‐caprolactone)/maghnite nanocomposites by in situ polymerization

Results of multinuclear MAS NMR spectroscopy are reported for poly (ε‐caprolactone)/maghnite nanocomposite formation, with ε‐caprolactone in situ polymerized in the presence of maghnite, a proton exchanged montmorillonite clay. Exfoliated and intercalated materials with different maghnite loading in the range 3–15 wt % were investigated. ¹H NMR evidences Brønsted acid hydroxyl groups in the silicate layers and shows that their broad signal at 7.6 ppm present in the parent clay disappears in the nanocomposite material. ²⁷Al MAS NMR results show that beside the hexacoordinated aluminum signal, two additional peaks corresponding to two different tetrahedral Al sites are present in the clay framework. The NMR signal intensity of only one of them was found to be affected in the nanocomposites compared with the parent maghnite, suggesting that these specific aluminum sites are the reactive ones at the initial stages of the polymerization. However almost no changes occurred in the ²⁹Si NMR spectra, confirming that the polymer grafting, as indicated earlier by atomic force microscopy, took place on the aluminum tetracoordinated sites rather than on the silicon sites. A mechanism of maghnite surface catalyzed polymerization of ε‐caprolactone was proposed, involving Brønsted and Lewis acid sites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3060–3068, 2007     

类锂离子C^3＋激发态（1s^2 2p）^2P光电离的计算

文中首次运用R—矩阵方法，在三态密耦近似下计算了类锂离子C^3 激发态(1s^2 2p)^2P光电离截面，主要给出了不同过程和不同分波的光电离截面。计算结果显示了光电离过程中非常丰富的Rydberg系列共振结构。     

强爆轰参数的理论估算

用两相的排平物态方程对硝基甲烷的强爆轰参数进行了理论估算 ,理论值与拟稳态强爆轰的实验值(爆速、爆压和爆温 )符合得很好 .这既检验了这种理论估算方法 ,也再次检验了爆轰的ZND理论和两相的排平物态方程 ,也是对实验方法的一种支持 .常k形物态方程的强爆轰参数理论估算方法也得到了有条件的肯定     

Time-Reversed Dynamical Entropy and Irreversibility in Markovian Random Processes

A concept of time-reversed entropy per unit time is introduced in analogy with the entropy per unit time by Shannon, Kolmogorov, and Sinai. This time-reversed entropy per unit time characterizes the dynamical randomness of a stochastic process backward in time, while the standard entropy per unit time characterizes the dynamical randomness forward in time. The difference between the time-reversed and standard entropies per unit time is shown to give the entropy production of Markovian processes in nonequilibrium steady states.     

Fluorescence Study of Excited-State Relaxation Processes of 2-Pyridyl-5-Aryloxazoles

Anomalously high fluorescence spectrum Stokes' shifts of 2(4-pyridyl)-5-(4-methylphenyl)oxazole, 2(4-pyridyl)-5-(4-methoxyphenyl)oxazole, 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole have been found. The fluorescence spectra of the compounds studied are shifted to longer wavelengths as the solvent dielectric constant increases. The dipole moments of these compounds increase by 3–4 times upon excitation. The fluorescence spectra of the compounds investigated are shifted to shorter wavelengths, and the fluorescence quantum yields increase as the temperature decreases. The fluorescence rate constant of 2(4-pyridyl)-5-(4-N,N-dimethylaminophenyl)oxazole changes slightly as the temperature decreases from 293 K (relaxed state) to 114 K (mainly nonrelaxed state). It was concluded that the anomalously high fluorescence Stokes' shift of 2-pyridyl-5-aryloxazole derivatives is caused by solvent orientation relaxation.     

多棒串接固体激光器谐振腔的研究

运用矩阵光学的方法对多棒串接固体激光器的谐振腔参数及其在平平腔时的热稳条件进行了研究，并计算了六棒串接平平腔固体激光器的稳定区.结果证明：多棒串接固体激光器的稳定区和非稳区相互间隔，在平平腔总腔长、激光棒数量n和棒间距L一定的条件下，当采用对称结构时(L₁=L₂)，则谐振腔的每段稳定区均达到最大；且只要 平平腔满足L₁=L₂=L/2以及热焦距f在大于某个下限值f_m时，稳定性条件01< 关键词： 多棒串接固体激光器 稳定区 热稳条件     

Coherent quantum transport in normal-metal/d-wave superconductor/normal-metal double tunnel junctions

Taking into account the effects of quantum interference and interface scattering, combining the electron current with hole current contribution to tunnel current,we study the coherent quantum transport in normal-metal/d-wave superconductor/normal-metal (NM/d-wave SC/NM) double tunnel junctions by using extended Blonder-Tinkham-Klapwijk (BTK) approach. It is shown that all quasiparticle transport coefficients and conductance spectrum exhibit oscillating behavior with the energy, in which periodic vanishing of Andreev reflection (AR) above superconducting gap is found.In tunnel limit for the interface scattering strength taken very large, there are a series of bound states of quasiparticles formed in SC.     

AGS能量下π~－π~－的Bose—Einstein关联

全同粒子间的玻色－爱因斯坦关联可以用来研究相对论性核碰撞中次级粒子源分布及有关的物理问题．本文用强子级联模型（ＨＣＭ）模拟２８Ｓｉ（１４．６ＡＧＣＶ／ｃ）＋Ａｕ反应，得到π－粒子的ｆｒｅｅｚｅ－ｏｕｔ状态，进而计算了π－π－关联函数，取得与实验一致的结果．还计算了ｆｒｅｅｚｅ—ｏｕｔπ－源的均方根线度，并讨论了它与拟合方法抽取的源参数间的关系．     

类锂铝复合机制产生X光激光的等离子体状态

本文从速率方程出发,讨论了类锂铝复合等离子体的激发态结构,衰减常数,反转率和小信号增益等表征介质增益特性的物理量以及它们随电子温度,电子密度和光子逃逸几率的变化。找到了进行类锂铝离子通过复合机制产生X光激光设计应创造的等离子体状态目标区域。还讨论了这些物理量随原子序数变化的定标律。     

三甲基膦和环氧乙烷的加成产物裂解反应机理的MNDO法研究

文中用ＭＮＤＯ方法研究了三甲基膦和环氧乙烷加成产物裂解反应机理