石墨烯能带中的重叠矩阵效应:Tight-Binding方法在模拟中的研究

采用紧束缚方法计算了石墨烯的价带(π)和导带(π*),考虑了非正交基矢下重叠矩阵效应,重叠积分参量s越小,导带越靠近费米面,而价带越远离费米面.在重叠积分参量s≤0.1时,基本保持了原子在实际空间中重叠所引起的能带的改变,太大(s=0.4)则会导致物理上失效.计算了石墨烯的能态密度,在费米面ε=0处(对应Dirac点)的能态密度为零,并且在Dirac点附近呈线性变化.     

Superthermostability of nanoscale TIC-reinforced copper alloys manufactured by a two-step ball-milling process

A Cu-TiC alloy, with nanoscale TiC particles highly dispersed in the submicron-grained Cu matrix, was manufactured by a self-developed two-step ball-milling process on Cu, Ti and C powders. The thermostability of the composite was evaluated by high-temperature isothermal annealing treatments, with temperatures ranging from 727 to 1273 K. The semicoherent nanoscale TiC particles with Cu matrix, mainly located along the grain boundaries, were found to exhibit the promising trait of blocking grain boundary migrations, which leads to a super-stabilized microstructures up to approximately the melting point of copper (1223 K). Furthermore, the Cu-TiC alloys after annealing at 1323 K showed a slight decrease in Vickers hardness as well as the duplex microstructure due to selective grain growth, which were discussed in terms of hardness contributions from various mechanisms.     

多层绝热材料规模化干燥处理时温度场的测试与分析

对大批量处理多层绝热材料的大型专用干燥箱满负荷运行时工作区域的温度场进行测试,通过温度分布和温度场均匀性的分析,得出了最高温度发生点的位置与成因以及影响温度场均匀性的主要因素,并对温度的控制方法、多层材料的布置方案和干燥设备的改进提出了建议。     

Multi-guasiparticle excitations of ~(91)Ru

The level structure in neutron-deficient nucleus 91Ru was investigated via the 58Ni(36Ar,2 plnγ)Ru reaction at a beam energy of 111 MeV.Charged particles,neutrons,and y-rays were emitted in this reaction and detected by the DIAMANT CsI ball,Neutron Wall,and the EXOGAM Ge clover array,respectively.In addition to the previously reported levels in 91Ru,new low-to-medium spin states were observed.Angular correlation and linear polarization measurements were performed to unambiguously determine spins and parities of the excited states in 91 Ru.The low-spin states of 91 Ru exhibit a scheme of multi-quasiparticle excitations,which is very similar to that of the neighboring N=47 isotone.These excitations have been interpreted in terms of the shell model.The calculations performed in the configuration space(p3/2,f5/2,p1/2,g9/2)reproduce the experimental excitation energies reasonably well,supporting the interpretation of the newly assigned positive-parity states in terms of the three quasiparticle configurationsπ(g9/2)^-2v(g9/2^-1 and v(g9/2)^-3.     

Numerical approach for generic three-phase flow based on cut-cell and ghost fluid methods

In this paper, we introduce numerical methods that can simulate complex multiphase flows. The finite volume method, applying Cartesian cut-cell is used in the computational domain, containing fluid and solid, to conserve mass and momentum. With this method, flows in and around any geometry can be simulated without complex and time consuming meshing. For the fluid region, which involves liquid and gas, the ghost fluid method is employed to handle the stiffness of the interface discontinuity problem. The interaction between each phase is treated simply by wall function models or jump conditions of pressure, velocity and shear stress at the interface. The sharp interface method “coupled level set (LS) and volume of fluid (VOF)” is used to represent the interface between the two fluid phases. This approach will combine some advantages of both interface tracking/capturing methods, such as the excellent mass conservation from the VOF method and good accuracy of interface normal computation from the LS function. The first coupled LS and VOF will be generated to reconstruct the interface between solid and the other materials. The second will represent the interface between liquid and gas.     

A discontinuous Galerkin immersed boundary solver for compressible flows: Adaptive local time stepping for artificial viscosity–based shock-capturing on cut cells

We present a higher-order cut cell immersed boundary method (IBM) for the simulation of high Mach number flows. As a novelty on a cut cell grid, we evaluate an adaptive local time stepping (LTS) scheme in combination with an artificial viscosity–based shock-capturing approach. The cut cell grid is optimized by a nonintrusive cell agglomeration strategy in order to avoid problems with small or ill-shaped cut cells. Our approach is based on a discontinuous Galerkin discretization of the compressible Euler equations, where the immersed boundary is implicitly defined by the zero isocontour of a level set function. In flow configurations with high Mach numbers, a numerical shock-capturing mechanism is crucial in order to prevent unphysical oscillations of the polynomial approximation in the vicinity of shocks. We achieve this by means of a viscous smoothing where the artificial viscosity follows from a modal decay sensor that has been adapted to the IBM. The problem of the severe time step restriction caused by the additional second-order diffusive term and small nonagglomerated cut cells is addressed by using an adaptive LTS algorithm. The robustness, stability, and accuracy of our approach are verified for several common test cases. Moreover, the results show that our approach lowers the computational costs drastically, especially for unsteady IBM problems with complex geometries.     

Target Design of Novel Histone Deacetylase 6 Selective Inhibitors with 2-Mercaptoquinazolinone as the Cap Moiety

Epigenetic alterations found in all human cancers are promising targets for anticancer therapy. In this sense, histone deacetylase inhibitors (HDACIs) are interesting anticancer agents that play an important role in the epigenetic regulation of cancer cells. Here, we report 15 novel hydroxamic acid-based histone deacetylase inhibitors with quinazolinone core structures. Five compounds exhibited antiproliferative activity with IC₅₀ values of 3.4–37.8 µM. Compound 8 with a 2-mercaptoquinazolinone cap moiety displayed the highest antiproliferative efficacy against MCF-7 cells. For the HDAC6 target selectivity study, compound 8 displayed an IC₅₀ value of 2.3 µM, which is 29.3 times higher than those of HDAC3, HDAC4, HDAC8, and HDAC11. Western blot assay proved that compound 8 strongly inhibited tubulin acetylation, a substrate of HDAC6. Compound 8 also displayed stronger inhibition activity against HDAC11 than the control drug Belinostat. The inhibitory mechanism of action of compound 8 on HDAC enzymes was then explored using molecular docking study. The data revealed a high binding affinity (−7.92 kcal/mol) of compound 8 toward HDAC6. In addition, dock pose analysis also proved that compound 8 might serve as a potent inhibitor of HDAC11.     

用平均场近似研究液晶分子结构与清亮点的关系

液晶的平均场理论假设每个液晶分子都是处在其它周围所有分子的平均作用势场中, 而不考虑该分子与周围各个分子之间的单独关联, 一个分子所感受到的分子场就是所有其它分子给予这个分子的作用场对位置和对取向的平均值. 当周围分子不是完全有序排列时, 其混乱程度可以用序参量S表示(S≤1), 中央一个分子受的势能为－Sg(θ). 其中g(θ)是在排列整齐的平均场中该分子的势能函数的负值. 在此基础上, 可以解一个关于序参量和温度的积分方程, 求出清亮点. 本文采用Gay-Berne势模拟液晶分子的双体势, 用分子力学UFF方法优化液晶分子(二环辛烷和硼笼的衍生物)的单体和双体的构型和能量, 从而获得Gay-Berne势的参数, 得到液晶的清亮点. 计算结果与实验基本一致.     

Structure and Aromaticity of AlCO-substituted Semibullvalene

The structures, energies and aromaticity (the nuclear-independent chemical shifts, NICS) of AlCO-substituted semibullvalenes were investigated at the B3LYP/6-311+G** level. Similar to BCO-substituted analogues, [2,6]-AlCO-semibullvalene is neutral bishomoaromatic. The NICS values reveal that the aromaticity of AlCO-substituted structures is smaller than that of BCO analogues.     

DFT Calculations of the Ionization Potential and Electron Affinity of Alaninamide

Adiabatic and vertical ionization potentials (IPs) and valence electron affinities (EAs) of alaninamide in gas phase have been determined using density functional theory (BLYP,B3LYP,B3P86) methods with 6-311++G(d,p) basis set,respectively. IPs and EAs of alaninamide in solutions have been calculated at the B3LYP/6-311++G(d,p) level. Five possible conformers of alaninamide and their charged states have been optimized employing density functional theory B3LYP method with 6-311++(d,p) basis set,respectively.