压缩变形对C20富勒烯分子电子传输特性的影响

The geometry,electronic structure and electronic transmission of Au electrode-compressed C20 fullerene Au electrode systems are investigated systemically,and some interesting results are obtained by use of molecular dynamics,Extend Hückel method of the first principle,and Green's function based method. The analytical results show that,due to intervention of Au electrodes,the electronic structure of compressed C20 fullerene is changed significantly,the coalescent between C20 fullerene and Au electrodes is intervenient of covalent bond and electrovalent bond,and the compressed C20 fullerenes are better conductors of electricity than those uncompressed or slightly compressed ones. The methods and the relative conclusions are beneficial to go further deep into electronic transmission of carbon fullerenes.     

贵金属金的状态方程

 提出了一个热压强的计算公式,从而获得金的状态方程。并结合实验数据与文献中常用的其它两个状态方程进行了比较。结果发现,修正后的状态方程与实验数据吻合很好,略优于其它两个状态方程。     

Grünwald插值算子的L2收敛性

证明了以Legendre多项式的极值点为插值结点组的Grünwald插值多项式在L2范数下是收敛的.     

球坐标系下多介质混合物模型的数值模拟

利用多介质混合模型在求解球坐标系下的Riemann问题时,需要考虑界面处压力平衡性弱、奇点处理、状态方程复杂等多个难点。本文将原始基于体积分数的Mie-Grüneisen多介质混合模型扩展到球坐标系下,并对多个细节进行了修正和改进,包括:在界面处对热力学参数进行修正、采用质量分数导出新输送方程、利用质量分数加权计算偏导数、采用相邻网格点的物理量定义奇点等。经过改进后的计算模型,可以得到无振荡的数值解,而且可以准确捕捉到冲击波和界面的位置。另外,使用改进后的质量分数模型比原始的体积分数模型得到的计算结果更准确。     

Enantioselective synthesis of macrolactone core of the natural product Sch725674

An enantioselective synthesis of the macrolactone core of natural product Sch725674 was accomplished from furfural. Key reactions in assembly of the macrolactone are the use of furan as a but-2-ene-dione equivalent and ring closing metathesis.     

Stereoselective synthesis of Sch 642305, an inhibitor of bacterial DNA primase

Sch 642305 is a fungal nonanolide, which inhibits bacterial DNA primase and HIV-1 Tat transactivation. The enantioselective synthesis of Sch 642305 was succeeded starting from useful chiral building block via stereoselective dianion alkylation of β-ketosulfoxide and lactonization.     

Existence and Global Asymptotic Behavior of Positive Solutions for Sublinear and Superlinear Fractional Boundary Value Problems

In this paper, the authors aim at proving two existence results of fractional differential boundary value problems of the form(P_(a,b)){D~αu(x) + f(x, u(x)) = 0, x ∈(0, 1),u(0) = u(1) = 0, D~(α-3)u(0) = a, u(1) =-b,where 3 α≤ 4, Dαis the standard Riemann-Liouville fractional derivative and a, b are nonnegative constants. First the authors suppose that f(x, t) =-p(x)t~σ, with σ∈(-1, 1)and p being a nonnegative continuous function that may be singular at x = 0 or x = 1and satisfies some conditions related to the Karamata regular variation theory. Combining sharp estimates on some potential functions and the Sch¨auder fixed point theorem, the authors prove the existence of a unique positive continuous solution to problem(P_(0,0)).Global estimates on such a solution are also obtained. To state the second existence result, the authors assume that a, b are nonnegative constants such that a + b 0 and f(x, t) = tφ(x, t), with φ(x, t) being a nonnegative continuous function in(0, 1)×[0, ∞) that is required to satisfy some suitable integrability condition. Using estimates on the Green's function and a perturbation argument, the authors prove the existence and uniqueness of a positive continuous solution u to problem(P_(a,b)), which behaves like the unique solution of the homogeneous problem corresponding to(P_(a,b)). Some examples are given to illustrate the existence results.     

现代高分子物理课程系列漫谈——溶液中高分子单链自由能

针对休克尔分子轨道(HMO)理论中只考虑相邻原子轨道相互作用的缺点,提出了一种改进的HMO模型,明确考虑间位碳原子共振积分,采用对称性匹配的分子轨道,得到了π共轭体系的能级公式,发现分子对称性降低可产生额外稳定化能,从而正确解释了纯碳环C2n分子稳定结构中键角交替变化规律,为理解二级Jahn-Teller效应提供了新思路。     

Magnetocaloric Effect in Anisotropic Mixed Spin ½—1 System: Pair Approximation Method

We use the Pair Approximation method to analyze the magnetic and magnetocaloric behaviors of diluted mixed spin ${\rm S_A}$=1 and spin ${\rm S_B}$=1/2 with the anisotropic Heisenberg model, on a cubic lattice with coordination number $z$=6. Our system is described in presence of an external magnetic field; the phase diagram and thermodynamic properties related to the concentration of magnetic atom (A or B) and the single ion anisotropy are constructed and discussed. Special attention is paid to magnetocaloric properties provided by isothermal entropy change as well as the cooling capacity. These cooling power keys are plotted and discussed as a function of interaction anisotropy and magnetic component concentration of two sublattices ions A and B. Numerical results show a double peak structure in the entropy change curve and the inverse magnetocaloric effect related to the presence of the negative single-ion anisotropy.     

VIBRATION AND STABILITY OF RING-STIFFENED THIN-WALLED CYLINDRICAL SHELLS CONVEYING FLUID

Based on the Flügge shell theory,equations of motion of ring-stiffened thin-walled cylindrical shells conveying fluid are developed with the aid of the Hamilton's principle.Analysis is carried out on t...