二元无规混合系统的有效介质理论

本文从二元无规混合物的两种不同拓扑结构出发,在Maxwell-Garnett理论的基础上,提出一种自洽的方法以改进类平均场的Bruggeman有效介质理论。导出了二元无规混合物有效电导率的普适式,研究了一些实际材料的电导率和热导率问题,理论计算结果与实验数据符合甚好。 关键词：     

Hopfield神经网络模型的恢复特性

通过引入不同概率的双峰无规神经激活阈分布,来考虑对神经网络“记忆”恢复特性的影响,结果表明即使储存模式数超过孤立Hopfield模型的临界值α_c时系统仍然能成功地恢复储存信息。 关键词：     

铁磁/反铁磁双层膜系统中的交换偏置及矫顽场的温度特性

提出了一个讨论铁磁／反铁磁双层膜中的交换偏置及矫顽场温度特性的物理模型，该模型，假设铁磁层为具有单畴各向异性的单畴膜而反铁磁层由许多相互独立具有多晶各向异性的颗粒组成，其温度依赖性主要来源于系统态的热不稳定，包括反铁磁颗粒易轴取向的热涨落和相关磁学量的温度依赖性等。计算结果表明其交换偏置随温度的增加非线性地减少而其矫顽场在体阻截温度处达极大值，且其体阻截温度随反铁磁颗粒粒径的增加而增加。我们的计算结果和相关实验结果一致，通过本的讨论，我们建议通过铁磁膜耦合上大粒径硬反铁磁颗粒膜可获得高交换偏置、低矫顽场且近独立于温度的相关磁学器件。     

Silicon quantum dots delivered phthalocyanine for fluorescence guided photodynamic therapy of tumor

Imaging-guided cancer therapy provides a simultaneous tumor imaging and treatment, which helps to eliminate the excessive toxicity to the healthy tissues. For this purpose, multifunctional probes capable of both imaging and curing are needed. In this work, we synthesize water-soluble silicon quantum dots(Si QDs) smaller than 5 nm. Such Si QDs are used for delivering the hydrophobic drug phthalocyanine(Pc). The as-prepared Si/Pc nanocomposite particles show efficient transmembrane delivery into cells and feasible biocompatibility. Moreover, these composite particles emit dualchannel fluorescence signals even after cellular internalization and demonstrate robust photostability in the Si channel.More interestingly, the Si/Pc composite particles show efficient photodynamic therapy effects against tumors both in vitro and in vivo.     

无规场量子Ising模型的研究

本文通过将对近似方法和离散路径积分表示组合,提出一种超越平均场的方法,用来研究无规场存在下的量子横向Ising模型。无规场取不同的形式时对系统相图结构的影响作了统一的描述。无规场取双峰和三峰分布时,通过数值计算对系统的临界特性包括三临界点和重入现象存在的可能性作了详细的研讨。理论在配位数z→∞时退化为平均场结果。 关键词：     

Microstructures in Strongly Interacting Dipolar Fluids

The formation of ring- and chain-like microstructures in ferrofluids consisting of interacting magnetic particles coated by a surfactant layer is studied by Monte Carlo simulations. For thin coating layers, it is found that ring- and chain-like structures coexist. The ring-like structures are suppressed by thicker coating layers. These observations are in agreement with recent experiments. Also, the ring-like structures are formed by dynamical aggregation of particles, instead of bending of linear chains. The latter process is forbidden bv a substantial energy barrier.     

Evaluation on performance of MM/PBSA in nucleic acid-protein systems

The molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) method has been widely used in predicting the binding affinity among ligands, proteins, and nucleic acids. However, the accuracy of the predicted binding energy by the standard MM/PBSA is not always good, especially in highly charged systems. In this work, we take the protein-nucleic acid complexes as an example, and showed that the use of screening electrostatic energy (instead of Coulomb electrostatic energy) in molecular mechanics can greatly improve the performance of MM/PBSA. In particular, the Pearson correlation coefficient of dataset II in the modified MM/PBSA (i.e., screening MM/PBSA) is about 0.52, much better than that (< 0.33) in the standard MM/PBSA. Further, we also evaluate the effect of solute dielectric constant and salt concentration on the performance of the screening MM/PBSA. The present study highlights the potential power of the screening MM/PBSA for predicting the binding energy in highly charged bio-systems.     

Transport coefficients and mechanical response in hard-disk colloidal suspensions

We investigate the transport properties and mechanical response of glassy hard disks using nonlinear Langevin equation theory.We derive expressions for the elastic shear modulus and viscosity in two dimensions on the basis of thermalactivated barrier-hopping dynamics and mechanically accelerated motion.Dense hard disks exhibit phenomena such as softening elasticity,shear-thinning of viscosity,and yielding upon deformation,which are qualitatively similar to dense hard-sphere colloidal suspensions in three dimensions.These phenomena can be ascribed to stress-induced "landscape tilting".Quantitative comparisons of these phenomena between hard disks and hard spheres are presented.Interestingly,we find that the density dependence of yield stress in hard disks is much more significant than in hard spheres.Our work provides a foundation for further generalizing the nonlinear Langevin equation theory to address slow dynamics and rheological behavior in binary or polydisperse mixtures of hard or soft disks.     

氧空位对钴掺杂氧化锌半导体磁性能的影响

从实验和理论上阐述了氧空位对Co掺杂ZnO半导体磁性能的影响.采用磁控溅射法在不同的氧分压下制备了Zn_095Co_005O薄膜,研究了氧分压对薄膜磁性能的影响.实验结果表明,高真空条件下制备的Zn_095Co_005O薄膜具有室温铁磁性,提高氧分压后制备的薄膜铁磁性逐渐消失.第一性原理计算表明,在Co掺杂ZnO体系中引入氧空位有利于降低铁磁态的能量,铁磁态的稳定性与氧空位和Co之间的距离密切相关. 关键词： Co掺杂ZnO 稀磁半导体 第一性原理计算 氧空位缺陷     

活力物质的非平衡结构和动力学

活力物质是一类典型的非平衡态体系,已成为软凝聚态物理新近发展的一个重要研究方向.活力物质由微驱动粒子组成,驱动力独立地施加在体系中的每个粒子上.文章概述了作者平时研究中所关注的一些活力物质系统中出现的十分有意义的现象,着重介绍了活力物质系统的构成,以及活力物质的气液态、铁磁态、向列相态和凝胶状态中涌现出的非平衡结构及其特殊的动力学行为.