Studies on Solid-Liquid Phase Transfer Equilibrium of Onium Salts(Ⅱ)

The present paper contains the effects of the ammonium ion, counter ion, solvent and anion being transferred on the solid-liquid phase transfer equilibrium constant of quaternary ammonium salts. The most striking difference between solid-liquid and liquid-liquid phase transfer equilibriums is that the length of alkyl chain shows a large effect on the latter but little on the former This means that the chain length affects only the hydrophobicity, rather than the lipophilicity.Keywords Quaternary ammonium salt, Phase transfer catalysis, Equilibrium constant, Hydrophobicity, Lipophilicity     

离子对的聚集作用(Ⅲ)——不同负离子对聚集度的影响

相转移催化方法是现代有机合成的新方法之一。目前,在实验室和工业生产上都有广泛的应用。其中一种重要的催化剂就是鎓盐,因此,鎓盐在有机溶剂中的聚集状态、聚集数目(聚集度)的不同,以及与反应性能的关系是值得探讨的基本课题之一。近年来,国外开展了有关的研究工作,但其结果尚有争议。     

一、二维弹塑性流体动力学数值计算的高精度新自由面格式

提出了适用于X射线或电子束辐照、爆炸和高速碰撞等问题的一、二维弹塑性流体动力学数值模拟计算的一种新自由面格式。对于X射线及电子束辐照材料与结构的热-力学效应的数值计算结果表明,该新自由面格式明显优于目前一直沿用的Richtmyer格式。从理论上证明了该新自由面格式具有三阶精度,而Richtmyer格式为一阶精度。     

60Coγ和高能电子在硅中NIEL的Monte Carlo计算

本文提出了计算高能电子和γ非电离能量损失(NIEL)的Monte Carlo方法,首次利用Monte Carlo方法计算了高能电子和⁶⁰Coγ的NIEL.给出了电子和⁶⁰Coγ在半导体硅材料中产生的NIEL和缺陷分布.计算结果与文献的比较表明模型是合理的.     

Asymptotic bounds for some bipartite graph: complete graph Ramsey numbers

The Ramsey number r(H,K_n) is the smallest integer N so that each graph on N vertices that fails to contain H as a subgraph has independence number at least n. It is shown that r(K_2,m,K_n)(m−1+o(1))(n/log n)² and r(C_2m,K_n)c(n/log n)^m/(m−1) for m fixed and n→∞. Also r(K_2,n,K_n)=Θ(n³/log² n) and .     

助剂对氨合成Fe1-xO基催化剂母体歧化反应的抑制作用的穆斯堡尔谱研究

Fe1-xO基氨合成催化剂具有高活性、易还原的特点[1,2].但Fe1-xO基催化剂的母体Fe1-xO在570℃以下热力学上的不稳定性是Fe1-xO基催化剂使用过程中倍受关注的重要问题之一.     

Paramagnetic Meissner effect in highT c superconductors (I)

Theoretical and experimental results show that the state of minimum Ginsburg-Landau free energy of small superconducting particles contains no flux line if the applied field is smaller than its critical field. For such micronsized particles, after being cooled in a small magnetic field (e.g. less than 100 μT), the moment remaining during subsequent zero field warrning contains almost no contribution from trapped flux and is dominated entirely by the paramagnetic Meissner effect (PME) of the particles. A systematic study of such a moment has been carried out to reveal its characteristic behavior of temperature, magnetic field and cooling or warming rate dependence. Methods for removing and recovering the PME of small superconducting particles are also reported.     

Ring opening reaction of 1,3-cyclohexadiene studied by semiclassical dynamics simulation

A semiclassical dynamics simulation study is reported for the ring opening reaction of 1,3-cyclohexadiene (CHD) triggered by a femtosecond-scale laser pulse. The results clearly demonstrate that, following the excitation by the laser pulse, the ring opening occurs at ∼110 fs and the molecule decays to the ground electronic state at ∼210 fs due to non-adiabatic transition of electrons from LUMO to HOMO orbitals. Isomerization of the product of the ring opening reaction, 1,3,5-hexatriene (HT), to various stable isomers are also well demonstrated by the simulations.     

Asymptotic Upper Bounds for Ramsey Functions

 We show that for any graph G with N vertices and average degree d, if the average degree of any neighborhood induced subgraph is at most a, then the independence number of G is at least Nf _{a +1}(d), where f _{a +1}(d)=∫₀ ¹(((1−t)^{1/( a +1)})/(a+1+(d−a−1)t))dt. Based on this result, we prove that for any fixed k and l, there holds r(K _k + _l ,K _n )≤ (l+o(1))n ^k /(logn) ^{k −1}. In particular, r(K _k , K _n )≤(1+o(1))n ^{k −1}/(log n) ^{k −2}. Received: May 11, 1998 Final version received: March 24, 1999