A simple micro‐extraction plate assay for automated LC‐MS/MS analysis of human serum 25‐hydroxyvitamin D levels

This short application note describes a simple and automated assay for determination of 25‐hydroxyvitamin D (25(OH)D) levels in very small volumes of human serum. It utilizes commercial 96‐well micro‐extraction plates with commercial 25(OH)D isotope calibration and quality control kits. Separation was achieved using a pentafluorophenyl liquid chromatography column followed by multiple reaction monitoring‐based quantification on an electrospray triple quadrupole mass spectrometer. Emphasis was placed on providing a simple assay that can be rapidly established in non‐specialized laboratories within days, without the need for laborious and time consuming sample preparation steps, advanced calibration or data acquisition routines. The analytical figures of merit obtained from this assay compared well to established assays. To demonstrate the applicability, the assay was applied to analysis of serum samples from patients with chronic liver diseases and compared to results from a routine clinical immunoassay. Copyright © 2015 John Wiley & Sons, Ltd.     

金属材料计算微观力学网格自动生成

金属材料微观结构形态不仅在材料科学中具有重要研究意义，而且也是微、细观力学分析，特别是计算微观力学的研究内容。本文依据冶金物理学理论基础，简化材料微结构形成过程，把数学和几何学结合起来，提出了“随机投放，逐点扫描”构造材料微结构形态的方法，并将此方法的仿真结果进行统计分析，用材料物理概念予以检验，表明仿真结果不丢失晶粒形状、晶粒度等主要统计特征，与真实材料的微结构有良好的一致性。     

双光纤Fabry-Perot干涉仪差动检测静电伺服硅微加速度计

详细介绍了一种新型的基于双光纤Fabry-Perot干涉式（以下简称DFPI）差动检测的静电伺服硅微加速度计的设计。通过结构建模以及模型仿真得到该加速度计的分辨率为0.2ug，测量范围为0．2ug～1g。     

激光陀螺抖动偏频解调与微小角速度检测

—本文讨论了激光陀螺抖动偏频解调与微小角速度检测的主要技术难点。针对难点，在整周期采样解调基础上提出了脉冲边沿触发鉴相解调方案，同时对该方案的合理性进行了详细分析和理论证明。文章最后指出，该方案对大角速度的高精度检测同样适用。     

采用显微网格法研究韧性材料平面应力状态下裂尖附近的应变场

用显微网格数字图象处理方法，测量了韧性材料平面应力条件下Ｉ型单边裂纹尖端附近的应变场。实验结果表明：在裂尖两侧存在与裂纹方向夹角约为５０°的大变形带。最大应变位于离裂尖一定距离的大变形带上，随着载荷增加，最大应变的位置逐渐靠近裂纹尖端。应变峰值轨迹线在裂纹顶端呈放射状，载荷增加时，应变峰值的轨迹线位置并不改变。     

The effect of hydrogen-fluorine defects on the conformational energy of polytrifluoroethylene chains

Conformational energy calculations were employed to determine the effect of hydrogen-fluorine defects on the conformation of the polytrifluoroethylene chain. It was determined that the 3₁ helix was energetically favored for all but the highly syndiotactic polymers, which favored the all-trans conformation. The incorporation of head-to-head linkages into the polymer chain increased the Conformational energy of the 3₁ helix while the Conformational energy of the all-trans form decreased. The energies of these two conformations did not equalize until the head-to-head concentration reached 20 to 30%, depending on the tacticity of the polymer. The trans, gauche, trans, gauche' conformation was also determined to be energetically favorable for the syndiotactic polymer, but both tacticity defects and head-to-head linkages caused a rapid increase in the Conformational energy. This was, therefore, concluded to be unlikely structure when chemical defects are incorporated into the polymer chain.     

Direct Writing of Conducting Polymers

Described herein is a new printing method—direct writing of conducting polymers (CPs)—based on pipette‐tip localized continuous electrochemical growth. A single barrel micropipette containing a metal wire (Pt) is filled with a mixture of monomer, supporting electrolyte, and an appropriate solvent. A droplet at the tip of the pipette contacts the substrate, which becomes the working electrode of a micro‐electrochemical cell confined to the tip droplet and the pipette. The metallic wire in the pipette acts as both counter and reference electrode. Electropolymerization forms the CP on the working electrode in a pattern controlled by the movement of the pipette. In this study, various width poly(pyrrole) 2D and 3D structures are extruded and characterized in terms of microcyclic voltammetry, Raman spectroscopy, and scanning electron microscopy.

     

X‐ray microtomographic visualization of Escherichia coli by metalloprotein overexpression

This paper reports X‐ray microtomographic visualization of the microorganism Escherichia coli overexpressing a metalloprotein ferritin. The three‐dimensional distribution of linear absorption coefficients determined using a synchrotron radiation microtomograph with a simple projection geometry revealed that the X‐ray absorption was homogeneously distributed, suggesting that every E. coli cell was labeled with the ferritin. The ferritin‐expressing E. coli exhibited linear absorption coefficients comparable with those of phosphotungstic acid stained cells. The submicrometer structure of the ferritin‐expressing E. coli cells was visualized by Zernike phase contrast using an imaging microtomograph equipped with a Fresnel zone plate. The obtained images revealed curved columnar or bunching oval structures corresponding to the E. coli cells. These results indicate that the metalloprotein overexpression facilitates X‐ray visualization of three‐dimensional cellular structures of biological objects.     

纳米级随机粗糙表面微观滑动摩擦力的计算研究

表面形貌很大程度上决定了摩擦副的摩擦性能, 而所有的表面都不可能是绝对光滑的.由于摩擦表面形貌的随机性, 决定了实际的摩擦过程具有随机性的特点, 因此为了获得与随机形貌对应的摩擦特性, 建立合理的随机摩擦模型是必要的. 本文基于Lennard-Jones势能建立了纳米级随机粗糙表面和原子级光滑的刚性平面间的随机摩擦模型; 模型中, 界面势能由法向载荷和界面间平衡距离决定.通过数值计算的方法, 推导了微观滑动摩擦力的计算公式和摩擦力与法向载荷之间的关系. 研究结果表明摩擦力随着法向载荷的增加而增加, 但不是线性增长. 结果也说明界面间的表面势能可能是微观摩擦力的本质起源. 关键词： 随机粗糙表面 Lennard-Jones势能 微滑动摩擦力 微摩擦     

微方肋冷却系统的换热特性

采用去离子水为冷却介质,对自行设计的不同结构微方肋散热器内的换热特性进行实验研究,结果表明:在进口温度为20 ℃、进口流量为57.225 L/h、底面平均温度为73.4 ℃时,散热器散热量可达2.83106 W/cm2,可以满足当前高热流密度散热需求;当散热面温度一定时,散热量随着散热器进口流量的增加而增加,但增速随散热器底面温度的增加变缓;努谢尔特数随雷诺数的增加而成幂次方增加,常规针肋结构和微针肋结构换热关系式不满足微方肋散热器特性。为了更好地表达微方肋散热器内的换热特性,拟合了微方肋散热器内对流换热关系式。