Robust core-shell supramolecular assemblies based on cationic vesicles and ring-shaped {Mo-154} polyoxomolybdate nanoclusters: Template-directed synthesis and characterizations

Substantial progress has been made recently in extending the supramolecular assembly of biomimetic structures to vesicle-based sophisticated nanocomposites and mesostructures. We report herein the successful preparation of unilamellar surfactant vesicles coated with a monolayer of ring-shaped {Mo-154} polyoxometalate (POM) nanoclusters, (NH4)(28)[Mo-154 (NO)(14)O(448)Hi(4)(H2O)(70)].approximate to 350H(2)O, by coulomb attractions using preformed didodecyldimethylammonium bromide (DDAB) surfactant vesicles as templates. The resultant vesicle-templated supramolecular assemblies are robust (they do not disintegrate upon dehydration) both at room-temperature ambient and vacuum conditions, as characterized by conventional transmission electron microscopy (TEM) and atomic force microscopy (AFM). The flexibility of the complex soft assemblies was also revealed by AFM measurements. The effect of POM-vesicle coulomb attractions on the dimensions of the templating vesicles was also investigated by using dynamic light scattering (DLS).Although origins of the structure stability of the as-prepared supramolecular assemblies are not clear yet, the nanometer scale cavities and the related properties of macroions of the POM clusters may play an important role in it.

椭偏光学显微成像系统聚焦评价函数的研究

自动聚焦技术在椭偏光学显微成像系统中是一项关键的技术。利用几种常用聚焦评价函数作为研究手段研究了这一过程。实验中采用硅基底表面人血纤维蛋白膜层和多元蛋白质芯片样品作为研究对象，研究了几种函数在自动聚焦过程中函数值的变化，以及噪音、样品区域选择对聚焦效果的影响。实验验证拉普拉斯评价函数和Sobel评价函数可以满足系统的要求；采用多幅图像平均的方法可以有效降低噪音，当平均次数达到9次以上，系统噪音的影响就可以被降至有效评价的程度；沿同一锐边，选择不同的调焦区域，对聚焦过程基本没有影响；利用评价函数在实验中确定了倾斜平面成像的最佳聚焦平面，并与理论像平面吻合。实验证明利用聚焦评价函数可以成功实现自动聚焦技术在椭偏光学显微成像系统中的应用。

海流引起海底管道悬空的数值模拟

海底管道悬跨将影响管道的安全运营。在海底管道稳定性设计中，需要合理分析具有初始嵌入深度的海底管道产生悬空的物理机制。本文对海流作用下铺设于砂质海床上的海底管道悬空进行了数值模拟。求解不可压缩流体N-S方程，分析了海流作用下管道周围的流场特性，研究了管道两侧的压力分布特性和海床表面剪应力的分布特点。在管道绕流流场分析的基础上，通过对土体渗流方程的求解，得到了管道周围砂质海床内的渗流场以及渗流水力梯度场的分布情况。与海床表面剪应力计算结果进行比较分析发现，管道下方渗流出口处土体的流土渗透破坏将诱导管道发生悬空

Molecular dynamics simulation of hydrogen enhancing dislocation emission

The interactive pair potential between Al and H is obtained based on the ab initio calculation and the Chen-Mobius 3D lattice inversion formula. By utilizing the pair potentials calculated, the effects of hydrogen on the dislocation emission from crack tip have been studied. The simulated result shows that hydrogen can reduce the cohesive strength for Al single crystal, and then the critical stress intensity factor for partial dislocation emission decreases from 0.11 MPa root m (C-H = 0) to 0.075 MPa root m (C-H=0.72%) and 0.06 MPa root m (C-H = 1.44%). This indicates thar hydrogen can enhance the dislocation emission. The simulation also shows that atoms of hydrogen can gather and turn into small bubbles, resulting in enhancement of the equilibrium vacancy concentration.

Dynamic function of damage and its implications

Dynamic function of damage is the key to the problem of damage evolution of solids. In order to understand it, one must understand its mesoscopic mechanisms and macroscopic formulation. In terms of evolution equation of microdamage and damage moment, a dynamic function of damage is strictly defined. The mesoscopic mechanism underlying self-closed damage evolution law is investigated by means of double damage moments. Numerical results of damage evolution demonstrate some common features for various microdamage dynamics. Then, the dynamic function of damage is applied to inhomogeneous damage field. In this case, damage evolution rate is no longer equal to the dynamic function of damage. It is found that the criterion for damage localization is closely related to compound damage. Finally, an inversion of damage evolution to the dynamic function of damage is proposed.

Some advances in study of crack identification problems

In the present paper, the crack identification problems are investigated. This kind of problems belong to the scope of inverse problems and are usually ill-posed on their solutions. The paper includes two parts: (1) Based on the dynamic BIEM and the optimization method and using the measured dynamic information on outer boundary, the identification of crack in a finite domain is investigated and a method for choosing the high sensitive frequency region is proposed successfully to improve the precision. (2) Based on 3-D static BIEM and hypersingular integral equation theory, the penny crack identification in a finite body is reduced to an optimization problem. The investigation gives us some initial understanding on the 3-D inverse problems.

离体培养骨组织骨折愈合生物力学模型的建立

离体培养骨组织骨折愈合生物力学模型的建立李可心，张碧辉，钱民全，陈楚楚，董福慧，尚天裕，贝时璋取孵育１５天来亨鸡胚作供体，在无菌条件下取出鸡胚腔骨，去除两端于骺端，在骨干中段作半截断造成实验骨折，将自行设计机械加压装置之两针分别插入骨折线两端骨段，并...

Microstructure and mechanical properties of Zr-Cu-Al bulk metallic glasses

Zr49Cu46Al5 and Zr48.5Cu46.5Al5 bulk metallic glasses(BMGs) with diameter of 5 mm were prepared through water-cooled copper mold casting. The phase structures of the two alloys were identified by X-ray diffractometry(XRD). The thermal stability was examined by differential scanning calorimetry(DSC). Zr49Cu46Al5 alloy shows a glass transition temperature, T, of about 689 K, an crystallization temperature, T-x, of about 736 K. The Zr48.5Cu46.5Al5 alloy shows no obvious exothermic peak. The microstructure of the as-cast alloys was analyzed by transmission electron microscopy(TEM). The aggregations of CuZr and CuZr2 nanocrystals with grain size of about 20 nm are observed in Zr49Cu46Al5 nanocrystalline composite, while the Zr48.5Cu46.5Al5 alloy containing many CuZr martensite plates is crystallized seriously. Mechanical properties of bulk Zr49Cu46Al5 nanocrystalline composite and Zr48.5Cu46.5Al5 alloy measured by compression tests at room temperature show that the work hardening ability of Zr48.5Cu46.5Al5 alloy is larger than that of Zr48.5Cu46.5Al5 alloy.

Characteristics of deep penetration laser welding of dissimilar metal Ni-based cast superalloy K418 and alloy steel 42CrMo

Experimental trials of autogenous deep penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 5.0 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser output power, welding velocity and defocusing distance on the morphology, welding depth and width as well as quality of the welded seam were investigated. Results show that full keyhole welding is not formed on both K4.18 and 42CrMo side, simultaneously, due to the relatively low output power. Partial fusion is observed on the welded seam near 42CrMo side because of the large disparity of thermal-physical and high-temperature mechanical properties of these two materials. Tile rnicrohardness of the laser-welded joint was also examined and analyzed. It is suggested that applying negative defocusing in the range of Raylei length can increase the welding depth and improve tile coupling efficiency of the laser materials interaction. (c) 2007 Elsevier Ltd. All rights reserved.

激波与小扰动波的相互作用(激波稳定性问题)

本文讨论朗道和栗弗席兹意义下的激波稳定性问题,也就是求解激波与小扰动波的相互作用问题。在无耗散介质的定常、平面激波两边产生了小扰动。朗道等假定小扰动波传播方向是垂直于激波的,得到的稳定条件是M_>1,M_2<1。我们则把小扰动波取为二维的,即推广为小扰动波可以斜着激波传播的情形,这是更常见的。结论是,无论按群速度方向来区分趋向波和离散波,还是像朗道等那样,按相速度方向来区分趋向波和离散波,既便满足条件M_1>1,M_2<1,对于某些纵向扰动波长与频率范围的声波而言,激波都不稳定。接着提出了几个实验,根据可能的实验结果讨论了趋向波与离散波的定义应按相速度方向还是群速度方向,说明了其意义。 对于管道内的定常激波有类似结果。

关于等旋转定理

<正> 在定常、轴对称、无限电导率的流体中,每个磁面上的角速度相等。这个Ferraro等

平晶型激光错位干涉仪原理及其应用

<正>平晶型激光错位干涉仪(简称平晶干涉仪)的原理是:由激光器发出的激光经扩束平行光管后,变成一束截面积大、方向性良好的平面波,它通过被测系统后依次在一块平晶的前后表面反射,形成位置稍稍错开的两束光,其重迭部分出现干涉图案.它本质上是一种波前干涉仪.本文对平面波前检验及球面波前检验两种情况进行了理论分析,其主要结论最:对于理想平面波前及满足一定条件时的理想球面波前,其干涉图案是一组平行等间距直线条纹,而被测系统的非理想性则导致干涉条纹的弯曲.平面波前检验主要用于气、液体流场观测及透明固体介质的均匀性检验,文中给出了介质密度差与干涉图案形状的定量夫系.球面波前

微孔法及干涉法在非稳定光学谐振腔调准中的应用

<正>由于非稳定腔具有大的可控模体积,采用共焦结构可以稳定输出平行光,准直后的光斑有最强的中心主瓣等优点,在大能量大菲涅耳数的激光器件中应用很广.但它的光学调准要求在10微弧度以上,因此,调准方法成为获得稳定运转的关键之一.本文介绍两种高精度调准方法.(1)微孔法:三个主要内容是微孔、叉丝和迭象.微孔在光学系统中可得到大的景深.通过微孔,人眼可看到叉丝的各次反射象迭合在一起,将它们按对接法对准可获得极高的调准精度.在正支非稳定腔结构的输出位置上设照明分划板.人眼通过微孔观察调准的各个阶段.最后使所有分划线的象重合在一起.