Modeling biomembranes and red blood cells by coarse-grained particle methods

In this work, the previously developed coarse-grained (CG) particle models for biomembranes and red blood cells (RBCs) are reviewed, and the advantages of the CG particle methods over the continuum and atomistic simulations for modeling biological phenomena are discussed. CG particle models can largely increase the length scale and time scale of atomistic simulations by eliminating the fast degrees of freedom while preserving the mesoscopic structures and properties of the simulated system. Moreover, CG particle models can be used to capture the microstructural alternations in diseased RBCs and simulate the topological changes of biomembranes and RBCs, which are the major challenges to the typical continuum representations of membranes and RBCs. The power and versatility of CG particle methods are demonstrated through simulating the dynamical processes involving significant topological changes, e.g., lipid self-assembly vesicle fusion and membrane budding.     

聚变堆相关的液态金属膜流初步实验研究

在磁约束核聚变堆的面对等离子部件设计中,液态金属锂膜流因具有带走杂质、保护面对等离子固壁等优点而被认为是优选方案之一. 然而,如何克服聚变堆中强磁场环境下产生的磁流体力学效应并形成大面积均匀铺展锂膜流动是目前亟需解决的问题.本文通过搭建室温液 态镓铟锡回路和高温液态锂回路,开展了两种不同特性的液态金属膜流实验, 并采用传统可视化方法获得了展向磁场存在时镓铟锡和锂在导电底板形成的液膜流动表面特征.实验结果 表明: 无磁场时,两种液态金属膜流流动表面波动特性与常规流体膜流均一致, 即随着流动雷诺数的增加表面波动变得更为混乱; 而展向磁场存在时,镓铟锡膜流表面波动变得更为规则, 且沿着磁场方向平行排列,表现为拟二维波动的特征; 而锂膜流却产生了明显的磁流体 力学阻力效应,表现为在流动方向局部产生锂滞留现象, 且滞留点随雷诺数增大向下游移动. 最后通过膜流受力分析,进一步阐述了锂膜流受到比镓铟锡膜流更为严重磁流体力学效应影响的原因.      

一种基于特征分解的图像融合方法

一幅图像可以分解成几何特征不同的纹理部分和卡通部分,基于这两大特征提出了一种图像融合方法.利用卡通和纹理特征的差异,通过学习分别得到卡通字典和纹理字典.在融合过程中,分别利用特定的卡通和纹理字典对源图像的卡通和纹理部分进行融合,融合后的卡通和纹理部分经简单相加得到融合图像.实验结果表明,所提方法是有效的.     

我国少数民族群众利益表达机制探析

当前我国少数民族群众利益表达机制存在着四个方面的问题:少数民族群众利益表达主体发育程度不均衡、少数民族群众利益表达客体态度消极、少数民族群众利益表达渠道不畅通、少数民族群众利益表达方式不合理。这就需要采取措施完善我国的少数民族群众利益表达机制:一是提高少数民族群众利益表达能力,培育少数民族群众利益表达主体;二是畅通少数民族群众利益表达渠道,健全完善网络利益表达;三是营造少数民族群众利益表达环境,引导少数民族群众进行利益表达;四是完善少数民族群众利益表达方式,充分利用体制内表达方式;五是建立少数民族群众利益表达机会公平机制,确保表达机会公平。     

菊粉内切酶在毕赤酵母中的表达及酶学性质测定

为了实现菊粉内切酶在毕赤酵母(Pichia pastoris)中的高活性表达并对表达的菊粉内切酶酶学性质、水解菊粉的产物进行分析。通过下载无花果曲霉菊粉内切酶基因的编码序列,做了密码子优化后进行全基因合成,然后在毕赤酵母GS115中表达。对表达的菊粉内切酶的酶活、最适反应温度、最适pH值、热稳定性进行了分析,最后对酶水解菊粉的产物进行了高效液相色谱(HPLC)分析。摇瓶表达的酶活力为420 U/mL,酶的最适反应温度为55℃,最适反应pH为6.0。HPLC分析表明:表达的菊粉内切酶酶解底物菊粉的主要产物为低聚果糖,聚合度为3～5之间。构建的工程酵母可以高效表达菊粉内切酶,可以用于生产低聚果糖。     

选择性搜索和多深度学习模型融合的目标跟踪

提出一种基于深度学习的多模型(卷积神经网络和卷积深信度网络)融合目标跟踪算法.该算法在提取候选粒子方面,使用选择性搜索和粒子滤波的方法.CVPR2013跟踪评价指标(50个视频序列、30个跟踪算法)验证了:该算法在跟踪中能有效地缓解目标物体由于遮挡、光照变化和尺度变化等因素造成的跟踪丢失情况的发生.     

Mechanics of water pore formation in lipid membrane under electric field

Transmembrane water pores are crucial for sub-stance transport through cell membranes via membrane fusion, such as in neural communication. However, the molecular mechanism of water pore formation is not clear. In this study, we apply all-atom molecular dynamics and bias-exchange metadynamics simulations to study the pro-cess of water pore formation under an electric field. We show that water molecules can enter a membrane under an electric field and form a water pore of a few nanometers in diame-ter. These water molecules disturb the interactions between lipid head groups and the ordered arrangement of lipids. Fol-lowing the movement of water molecules, the lipid head groups are rotated and driven into the hydrophobic region of the membrane. The reorientated lipid head groups inside the membrane form a hydrophilic surface of the water pore. This study reveals the atomic details of how an electric field influences the movement of water molecules and lipid head groups, resulting in water pore formation.     

Closed-form expressions of the electrostatic potential close to a grid placed between two plates

The potential distribution between a grid and two plates is an electrostatic problem already solved for various applications such as MultiWire detectors used in Nuclear Physics, or electrostatic precipitators in Engineering. Since references and notations for this analytical solution are ancient and rather bewildering, the first part of this paper presents a revisit and a discussion of the formulations that assume a line charge on the wire. This is completed by establishing a ready-to use closed-form expression valid for the general configuration where the plates are not grounded. The second part is about the investigation of the line model accuracy close to the wires, using both analytical and numerical approaches. In the symmetric case where the grid is placed at equal distances between two grounded plates, it is shown that the error can be modelled using a quadrupole charge. For the asymmetric case, a larger discrepancy of the line model is brought to light, with an error featuring a dipole-like distribution. In order to cope with this small but not negligible error, a classical dipole model is implemented, leading to an accurate theoretical expression of the potential.     

平响应X射线光阴极的理论设计与计算模拟

给出了适用于0.1~5keV的平响应X射线光阴极的设计方案.采用两层不同厚度、相同面积的相同金属材料制备X射线光阴极,两金属层的厚度和微观结构经过优化后,在惯性约束聚变实验感兴趣的能区具有良好的平响应特征,不需要复杂的解谱过程.选取4种不同的光阴极材料,改变厚度和占空比设计,计算得到了光阴极不平整度.模拟结果表明,该光阴极在0.1~5keV能量响应基本一致,不平整度优于5%.