An analytical poroelastic model for laboratorial mechanical testing of the articular cartilage (AC)

The articular cartilage (AC) can be seen as a biphasic poroelastic material. The cartilage deformation under compression mainly leads to an interstitial fluid flow in the porous solid phase. In this paper, an analytical poroelastic model for the AC under laboratorial mechanical testing is developed. The solutions of interstitial fluid pressure and velocity are obtained. The results show the following facts. (i) Both the pressure and fluid velocity amplitudes are proportional to the strain loading amplitude. (ii) Both the amplitudes of pore fluid pressure and velocity in the AC depend more on the loading amplitude than on the frequency. Thus, in order to obtain the considerable fluid stimulus for the AC cell responses, the most effective way is to increase the loading amplitude rather than the frequency. (iii) Both the interstitial fluid pressure and velocity are strongly affected by permeability variations. This model can be used in experimental tests of the parameters of AC or other poroelastic materials, and in research of mechanotransduction and injury mechanism involved interstitial fluid flow.     

亚微米颗粒在汇作用下运动机理的实验研究

当前,城市空气质量的不断恶化,引起了公众的普遍性关注.空气中的悬浮颗粒物,是城市大气环境重要污染源之一,其分布、运动及扩散规律已成为科学领域的研究热点.与连续流体不同,大气中的悬浮颗粒物是离散的,确定颗粒运动的模型是研究大气细微颗粒污染问题的关键.本文拟研究小空间静稳空气中亚微米级颗粒在汇作用下的运动规律,并构建其运动模型.在密闭实验空间中通过燃烧生成亚微米颗粒,利用静电吸附装置模拟颗粒汇,并通过粒子图像测速(particle image velocimetry,PIV)实验和激光多普勒测速仪(lasser Doppler velocimeter,LDV)实验技术测量分析不同空间内亚微米颗粒在大气中的热运动速度和在汇作用下的运动规律,并推导出颗粒物的速度分布经验公式.结果显示:粒子在汇作用下的运动与连续流体汇运动规律类似,但在小空间内颗粒的运动不满足流体连续方程;说明在无气流夹带输运情况下,利用汇作用及颗粒的扩散而发展的颗粒净化技术是可行的.     

基于YAG透明陶瓷制作衍射光栅元件的研究

研究并制作了以钇铝石榴石(YAG)透明陶瓷为基底材料的衍射光栅元件。通过磁控溅射技术在YAG透明陶瓷表面溅射一层均匀致密的金属铬,获得带有硬掩模的陶瓷样品。借助接触式曝光系统进行光刻,反复试验,获得带有衍射光栅的YAG透明陶瓷样品。经光学轮廓仪检测,样品铬膜厚0.072 m,光栅细节得到完好保留。实际光栅的衍射图样再次验证了以YAG透明陶瓷代替传统微光刻基底材料制作衍射光栅的可行性,使得衍射光栅在更为复杂的环境下发挥作用成为可能。     

Sensitive determination of strongly polar aromatic amines in water samples by stir bar sorptive extraction based on poly(vinylimidazole-divinylbenzene) monolithic material and liquid chromatographic analysis

A simple and sensitive method for the determination of polar aromatic amines (PAAs) was developed using stir bar sorptive extraction (SBSE) coupling to high-performance liquid chromatography. A hydrophilic poly(vinylimidazole-divinylbenzene) (VIDB) monolithic material was prepared and acted as SBSE coating. The influences of polymerization conditions for VIDB on the extraction efficiency were investigated using aniline and 2,4-dinitroaniline as detected solutes. To achieve optimum extraction performance for PAAs, several parameters including extraction and desorption time, desorption solvent, ionic strength and pH value of sample matrix were investigated. The results showed that under the optimized experimental conditions, the method showed good sensitivity and excellent recoveries, as well as advantages such as linearity, simplicity, low cost and high feasibility. The extraction performance of present method to the target compounds also compared with commercial SBSE which using polydimethylsiloxane as coating and other SBSE which based on monolithic materials. Finally, the proposed method was successfully applied to the determination of PAAs in lake and sea waters, and excellent recoveries of spiked target compounds in real samples were obtained.     

Development and validation of stir bar sorptive extraction of polar phenols in water followed by HPLC separation in poly(vinylpyrrolididone‐divinylbenzene) monolith

An effective and simple method for polar phenols in water matrix was developed by using stir bar sorptive extraction (SBSE) based on a hydrophilic poly(vinylpyrrolididone‐divinylbenzene) (VPDB) monolithic material and HPLC analysis. To achieve optimum extraction performance for phenols, several parameters, including extraction and desorption time, desorption solvent, pH value, and ionic strength of sample matrix, were investigated. Under the optimized experimental conditions, eight phenols were directly enriched from water samples and analyzed by HPLC‐DAD. The detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.72–1.37 and 2.40–4.27 ng/mL from spiked water, respectively. Recoveries of eight phenolic compounds were found in the range of 55.2–95.9%. The calibration curves showed the linearity ranging from 5 to 150 ng/mL with linear regression coefficient R² values above 0.98. Method repeatability presented as intra‐ and interday precisions were also found with the RSDs less than 4.10 and 7.61%, respectively. The distribution coefficients between VPDB and water (K_VPDB/W) for phenolic compounds were also calculated and compared with K_O/W. Finally, the proposed method was successfully applied to the determination of the target compounds in tap water, sea water and wastewater samples.     

A priori and a posteriori error analysis of edge stabilization Galerkin method for the optimal control problem governed by convection-dominated diffusion equation

In this paper, we study an edge-stabilization Galerkin approximation scheme for the constrained optimal-control problem governed by convection-dominated diffusion equation. The method uses least-square stabilization of the gradient jumps across element edges. A priori and a posteriori error estimates are derived for both the state, co-state and the control. The theoretical results are illustrated by two numerical experiments.     

基于交变电场的月表除尘方法研究进展

实施月球表面探测时, 月表尘埃物质容易在探测设备表面沉积并造成严重不利影响. 近年来交变电场 除尘方法被认为是在月表进行尘埃防护的有效手段, 但要使该方法实用化, 仍需要弄清除尘的机理, 确定相关 影响的因素, 以便进行优化设计. 本文从实现交变电场的电帘出发, 分别介绍电帘表面的交变电场分布、颗粒 在电帘表面的受力状态、颗粒群运动过程中的摩擦电荷分布、颗粒运动的模拟方法、颗粒运动过程、除尘效 率和能耗的理论和实验研究, 并对自清洁太阳能电池板系统的设计与制备进行了总结. 对颗粒的起跳过程、静 电的生成和除尘效率影响因素等普遍关注的问题进行了细致的讨论和总结, 指出了颗粒的带电量对起跳过程 的关键作用. 最后, 对该除尘防尘存在的问题进行了归纳, 并展望了该领域的发展趋势.      

Trapping of helium atom by vacancy in tungsten: a density functional theory study

The interaction between helium (He) atom and vacancy defect in tungsten (W) has been investigated by using first-principles simulations. We have obtained that the most stable site for He in tungsten is the substitutional position because He can keep its own electronic structure at this position. In the studied tungsten system, vacancy can act as a trapping center for surrounding He atom with negative trapping energy. The migration behaviors of He atom at tetrahedral interstitial site in W, which can be trapped by vacancy but the final position is almost unchanged comparing with its initial position through structural relaxation, have been predicted and discussed. It is also found that single He atom prefers to go through an octahedral site rather than through a direct path to the vacancy, and the stronger the interaction between He atom and vacancy is, the lower the migration barrier will be.     

一种骨小管中液体流动产生的流量及切应力模型

骨组织受力变形后其内部液体就会流动,同时在其微观结构——骨单元壁中扩散,并进一步产生一系列与骨液流动相关的物理效应,如流体剪切应力、流动电位等,这些物理效应被细胞感知并做出破骨或成骨等反应,来使骨适应外部载荷环境.鉴于骨组织产生的内部液体流动很难实验测定,理论模拟是目前的主要研究手段.基于骨单元的多孔弹性性质建立了骨小管内部液体的流动模型,该模型将骨单元所受的外部载荷与骨小管内部液体的压力、流速、流量和切应力联系起来,并进一步可以研究其力传导与力电传导机制.骨小管模型的建立分别基于中空和考虑哈弗液体的骨单元模型,并考虑了骨单元外壁的弹性约束和刚性位移约束两种边界条件.最终得到骨单元在外部轴向载荷作用下,骨小管内部液体的流量及流体切应力的解析解.结果表明:骨小管中的液体流量与流体切应力都正比于应变载荷幅值和频率,并由载荷的应变率决定.因此应变率可以作为控制流量和流体切应力的一种生理载荷因素.流量随着骨小管半径的增大而非线性增大,而流体切应力则随着骨小管半径的增大而线性增大.此外,在相同的载荷下,含哈弗液体的骨单元的模型中,骨小管中液体的流量和切应力均大于中空骨单元模型.     

Synthesis of Unsymmetrical 1,3‐Diynes via Pd/Cu‐Catalyzed Cross‐Coupling of Terminal Alkynes at Room Temperature

A facile and practical synthetic route of unsymmetrical 1,3‐diynes via the PdCl/CuI catalyzed oxidative coupling of two different terminal alkynes has been developed by using 3‐(diphenylphosphino)propanoic acid as a ligand in the presence of oxygen. This system is suitable for not only aromatic alkynes but also heteroaromatic and aliphatic alkynes which were transformed into the corresponding unsymmetrical 1,3‐diynes in moderate to good yields at room temperature. Moreover, the unsymmetrical 1,3‐diynes were also obtained on a multi‐gram scale. Mechanistic studies suggest that oxygen plays a key role in the catalytic cycles.