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.     

Predicting Fiber Contact in a Three-Dimensional Model of Paper

We present a new methodology for the mathematical analysis of 3D paper structure and apply it to a model that can be simulated on a computer. We rigorously derive upper and lower bounds for fiber contact areas, and derive an approximation that is very close to values calculated from the simulations. The method involves the stochastic geometry and combinatorics of large numbers of randomly located sets, which quantify the interactions between fibers. The main calculation involves a sum resembling a partition function with many-body interactions of all orders.     

Nuclear Liquid-Gas Phase Transition Shown in Multifragment ation

The Incomplete-Fusion-nagmentation Model has been used to reproduce nicely the experimental evidence of liquid-gas phase transition probed in the reaction of Au + Au at 600A MeV. The analysis of the relative yields of decay modes for the projectile remnant as a function of bound> shows clearly the competition and transformation processes of various decay modes of projectile remnant with decreasing of bound>. The agreement between theoretical and experimental results for the anaJysis of relative yield of decay modes indicates that the experimental evidence of liquid-gas phase transition is composed of the decay mode transformations.     

Synthesis,spectroscopic, magnetic and thermal properties of bimetallic salts, [Ni(L)][MCl4] {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. X-ray structure of [Ni(L)][CoCl4]

New bimetallic complex salts corresponding to the formulation [Ni(L)][MCl₄] have been synthesized by the facile reaction between [Ni(L)](ClO₄)₂ and [MCl₂(PPh₃)₂] in high yields {where M = Co(II), Zn(II), Hg(II) and L = 3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane}. The complexes were characterized by IR, electronic spectra, TGA/DSC, magnetic moment and conductivity measurements. The X-ray crystal structure for [Ni(L)][CoCl₄] clearly establishes the cationic–anionic interaction. It crystallizes in the space group P1 with unit cell dimensions a = 7.1740(15) Å, b = 8.1583(16) Å and c = 8.3102(16) Å. A square-planar geometry is evident for the [Ni(L)]²⁺ cation while the anion is found to be tetrahedral. A two-step thermolytic pattern is observed in the pyrolysis of the bimetallic complex salts.     

Ultra-incompressible Ternary Diborides Re_（0.5）Ir_（0.5）B_2,Re_（0.5）Tc_（0.5）B_2,Os_（0.5）W_（0.5）B_2 and Os_（0.5）Ru_（0.5）B_2：Density Functional Calculation

In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal (P63/mmc) and orthorhombic (Pmmn) structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B (Ru-B) than those of Re-B (Os-B). All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength.     

Catalyzed hydroboration of nitrostyrenes and 4-vinylaniline: a mild and selective route to aniline derivatives containing boronate esters

Transition metal catalyzed reactions of catecholborane (HBcat; cat = 1,2-O₂C₆H₄) with β-nitrostyrene and 3-nitrostyrene lead to products derived from competing hydrogenation and hydroboration of the alkene unit along with reduction of the nitro group. Hydroboration of 4-vinylaniline gave regioselective formation of either the branched or the linear organoboronate ester depending upon the catalyst precursors (i.e., RhCl(PPh₃)₃ or Rh(acac)(dppe) vs [Cp^∗IrCl₂]₂) used to facilitate this reaction. Hydroboration products were converted to air-stable primary amines by addition of pinacol.