尿素分子团簇线性和一阶非线性光学极化率的理论计算

检验分子晶体非线性光学极化率的可加性,对于确认有向气体模型(Oriented-Gas Model) 具有重要的科学意义,对探索新型实用的分子非线性光学材料也有实际的意义。本文对尿素晶体中分子簇非线性光学极化率的可加性做了详尽的理论研究。首次做到了尿素分子最近邻排布团簇的非线性光学极化率的从头算,从而扩展了前人的工作。研究结果有效地确认了有向气体模型。同时,我们还提出了壳层结构模型 (Shell-Structure Model),用以解决有向气体模型中的缺陷,可实现更为有效可靠地计算晶体宏观非线性光学系数。     

Could the New Absorption Cross Section of J/ψ Change the Aspect of Nuclear Absorption Mechanism

The enlarged new absorption cross sections of J/ψ by π and ρ were put into the hadron and string cascade model, JPCIAE, and the J/ψ suppression factors in P-A, O-U, S-U and Pb-Pb minimum bias collisions at 200A GeV/c were calculated with nuclear absorption mechanism only. The results seem to indicate that, with new enlarged cross section it is still hard to change the aspect that nuclear absorption mechanism itself could not easily account for the J/ψ anomalous suppression in Pb-Pb collisions.     

Reactions of Podophyllotoxin with DDQ

Introduction 2, 3-Dichloro-5, 6-dicyanobenzoquinone (DDQ) can react with lignans of the mono- arylidene-butyrolactone1, aryltetralin2, dibenzylbutane3 and aryltetralin-butyrolactone4,5 series. We have studied the reactions of this reagent with podophyllotoxin 1, which is a well-known natural product on account of its long history of use in folk medicine and the biological activity of its many derivatives6. In particular, derivatives of 4-demethyl epipodophyllotoxin are used in cancer chemo…     

核形变对J/ψ压低的效应

用强子和弦级联模型,JPCIAE,研究(200A GeV)U+U中心碰撞中核形变对J/ψ压低的效应.结果表明:在两形变核的长轴都沿束流方向的碰撞中,J/ψ压低因子约为两长轴都垂直于束流方向碰撞时的二分之一.     

<Superscript>13</Superscript>C NMR investigation of the structure of alkylammonium chloride micells in aqueous solutions

¹³C NMR chemical shifts are obtained for aqueous solutions of alkylammonium chlorides (C₆–C₉) in the region of the critical micelle concentration (CMC). A new method of processing ¹³C NMR experimental data for aqueous solutions of alkylammonium chlorides is developed to calculate the aggregation numbers N of micelles and the equilibrium constants K of the micelle formation within the law of mass action. With the use of these N and K values the standard Gibbs energy of the micelle formation and its increment of −1.8 kJ/mol are found for the methylene group. A small increment confirms the hypothesis about the structure of micelles consisting of both contact and hydrated associates. The structural model of the association of alkylammonium chlorides in water, the effect of alkyl chain length on the CMC, the hydrophobic interaction, the formation of hydrate associates, and also a possible classification of surfactants based on this are discussed.     

相对论重离子碰撞的温度涨落与热容

使用LUCIAE3.0模型模拟了SPS能区Pb+Pb和C+C在不同能量(E_lab=20—200A GeV)和不同中心度下的重离子碰撞.并通过逐个事件的粒子温度涨落提取出了相应粒子的热容,发现对于同一碰撞系统,单位发射粒子的热容随碰撞能量的升高而下降直至饱和,随着碰撞参数b的增大而减小,而且发现单位发射粒子的热容具有随粒子质量的变大而变大的关系.同时还发现不同碰撞系统中同一种粒子具有相同的单位发射粒子热容,并给出了相应的解释.     

Influence of the special features of atomic structure of Si24 and MeSi24 (Me = Na or K) nanoparticles on their electron properties

The influence of atomic structure of silicon nanoparticles on the distribution of total and partial state densities in the valence and conductivity bands as well as on the valence band and gap widths is analyzed based on the calculated geometrical and electron structure of the Si ₂₄ and MeSi ₂₄ (Me = Na or K) clusters. Semi-empirical AM1 and PM3 methods are used for calculations. The adequacy of calculations is confirmed by their comparison with the available experimental data. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–51, February, 2006.     

Spatial structure and electronic spectrum of TiSi n − clusters (n = 6–18)

Results from optimizing the spatial structure and calculated electronic spectra of anion clusters TiSi _n ^? (n = 6–18) are presented. Calculations are performed within the density functional theory. Spatial structures of clusters detected experimentally are established by comparing the calculated and experimental data. It is shown that prismatic and fullerene-like structures are the ones most energetically favorable for clusters TiSi _n ^? . It is concluded that these structures are basic when building clusters with close numbers of silicon atoms.     

158A GeV的相对论重离子碰撞的强子快度分布及温度拟合

针对最近NA49在158A GeV的实验(C+C,Si+Si,Pb+Pb)数据,应用LUCIAE3.0模型进行模拟,得到了强子的快度分布和横向动量分布,并与实验数据进行比较,发现基本与实验数据相吻合。并对横向动量分布进行温度拟合,给出了和实验数据吻合很好的结果,但是对于重系统或重强子LUCIAE3.0给出的结果与实验符合相对较差.