Inexpensive holder for hand-trimming resin-embedded tissues

A simple and inexpensive mount for securely holding resin-embedded tissues for trimming prior to sectioning for light or electron microscopy is described. The unit is composed of a base plate from which a 12.7-mm drill chuck protrudes. A tissue block is clamped into a microtome chuck and that is mounted in the drill chuck. A standard dissecting microscope is placed over the unit and used to magnify the block for trimming. Total cost of materials is estimated to be $20-40 USD.     

Preparation of ceramic fibre TEM cross-sections using ultramicrotomy and ion beam thinning methods

The preparation of specimens for detailed TEM microanalysis of micrometre-diameter, ceramic fibre cross-sections is described. The starter material is ceramic fibre in powder form and both ultramicrotomy-based and ion beam thinning-based methods are described. Requirements for specimens of uniform and adequate thinness, for easy selection of representative fibre cross-sections within the same specimen and for a reliable and time-efficient preparation method, resulted in choice of the ultramicrotomy-based method and the associated development of a novel extrusion and sedimentation technique of embedding the fibres to provide necessary pre-alignment and packing.     

Sectioning spherical aluminum oxide particles for transmission electron microscopy

A technique was developed to aid in the interpretation of nucleation and growth characteristics of otherwise electron-opaque Al₂O₃ particles. The technique involved embedding a dense collection of particles in an Epon mixture and sectioning with a diamond knife on an ultramicrotome. Serial sections were utilized to obtain three-dimensional information. It was found that ultramicrotomy does not introduce artifacts in ceramics which would otherwise affect measurements of the crystallite size or phase fraction, nor does it affect the crystallographic data significantly. It was observed that α-Al₂O₃ nucleated at the surface of isolated particles and in the neck region of sintered particles. Other data, obtained from diffraction and in situ hot-stage studies, indicated that each polycrystalline α-Al₂O₃ particle transformed to a nearly single crystal of γ-Al₂O₃, which extended into adjacent particles under favorable circumstances.     

An easy method for orientated embedding tissue culture cell monolayers in LR white resin for postembedding immunocytochemistry

Partial polymerization of LR White resin blocks is a frequently encountered problem if oxygen is present during the polymerization reaction. Instructions are given for a simple method to embed cell culture monolayer in LR White acrylic resin, which is suitable for immunocytochemistry. The advantage of this method is that it is easy and reliable. It also ensures accurate orientation of the cell monolayer in relation to the desired plane of sectioning.     

Continuous serial thin sectioning for electron microscopy

The process of serial sectioning for electron microscopy has been refined such that loss of thin sections is kept below 0.1% and the series is continued at will. The method relies on microscopic control of all manipulative steps, Formvar casting on plate glass for coated slot grids, coating of the block with contact cement for reliable ribboning, pickup by a one-step method with grid support in the diamond knife trough, staining in LKB grid holders, gentle treatment of grids in the electron microscope, and a slight modification to the microscope for safe grid withdrawal. The results are particularly applicable to the reconstruction of neuronal microcircuits and larger volumes of neuropil.     

An appraisal of ultramicrotomy, FIBSEM and cryogenic FIBSEM techniques for the sectioning of biological cells on titanium substrates for TEM investigation

Ultramicrotomy, focused ion beam scanning electron microscopy (FIBSEM) and cryogenic FIBSEM (cryo-FIBSEM) techniques, as developed for the controlled cross-sectioning of mesenchymal stem cells (MSCs) and human osteoblasts (HObs) on titanium (Ti) substrates for transmission electron microscopy (TEM) investigation, are compared. Conventional ultramicrotomy has been used to section cells on Ti-foil substrates embedded in resin, but significant problems with cell detachment using this technique restricted its general applicability. Conventional FIBSEM 'lift-out' procedures were found to be effective for the preparation of uniform sections of fixed and dehydrated cell/Ti specimens, but the control of cell staining remains an issue. Cryo-FIBSEM procedures used with an 'H-bar' sample geometry enabled the sectioning of fixed and hydrated cell/Ti specimens, but issues remain over ion beam-induced artefacts and control of frost on the sample foils.     

高精度智能定硫仪的设计

为了测量煤中硫的含量,设计了基于库仑滴定法的高精度智能定硫仪.对智能定硫仪的结构和工作原理进行了介绍,重点分析了仪器的数据采集模块、电解电流控制模块和炉温控制模块.该仪器采用12位串行A/D转换器对4路输入信号进行采集,通过冷端补偿和PID控制实现了炉温的高精度测量与控制,并采用D/A转换器对电解电流进行精确控制,最后对测量数据的精密度和准确度进行了检验.测试结果表明,用该仪器测量低硫煤时标准偏差为0.012%,测量高硫煤时标准偏差为0.027%,精度远高于国家标准.     

Preparation of metal specimens for HREM by ultramicrotomy

The preparation of aluminum specimens by ultramicrotomy for high resolution electron microscopy is reported. Illustrative examples of high resolution micrographs from aluminium and an aluminium/aluminium oxide interface obtained with the specimens are presented.     

An improved preparation method for cross‐sectional TEM specimens of films deposited on metallic substrates

Cross‐sectional TEM analysis is one of the most important techniques to characterize microstructures of films. However, the complex process, low efficiency, and low success rate of specimen preparation limit its application. This paper analyzed the main causes of low success rate and proposed an improved method for specimen preparation of films deposited on metallic substrates. This method consisting of twin‐jet electropolishing and one‐sided rocking ion milling is high in efficiency and success rate. Microsc. Res. Tech. 79:276–279, 2016. © 2016 Wiley Periodicals, Inc.     

An electron-microscope-based system for accurate microdimensional measurements

Calibration measurements of linear dimensions in the range 0.1 to 100 μm are provided by a high-resolution, scanning electron microscope-scanning specimen stage system. Computer-controlled, with a stationary sem electron beam and interferometric measurement of stage position, the system can provide point-to-point measurements accurate to 0.01 μm. It also forms the basis for development and certification of calibrated standards for planar objects, particles, and other microscopic objects and features     

一种快速精确的虹膜定位方法

为了提高虹膜定位的速度和精度,本文提出了一种定位方法.对于虹膜的内边缘定位,本文基于图像二值化和形态学的腐蚀、膨胀,建立了有效的去噪算法,并提出了一种灰度投影与圆的方程相结合的方法,可准确定位虹膜内边缘.对于虹膜的外边缘定位,本文利用虹膜内边缘定位数据对边缘图像去噪得到有效的边缘信息,在此基础上提出了一种改进的Hough变换方法,可以快速准确地定位虹膜外边缘.实验结果表明,本文提出的虹膜定位算法显著提高了虹膜定位的速度和精度,避免了传统Hough算法搜索的盲目性.     

面向飞机蒙皮柔性夹持数控切边的定位仿真系统及应用

针对切边过程中有效定位点动态变化的特征,提出＂X-2-1＂动态定位原理。基于几何约束关系实现了柔性工装对曲面零件的虚拟装夹,精确计算出柔性工装的调形参数。通过协调单元生死顺序和铣削力加载,实现了切边过程有限元仿真分析。选择典型飞机蒙皮零件进行了集成验证试验,试验分析结果表明加工精度满足制造要求。     

一种描述缺口根部初始裂纹长度的客观量

工程构件的初始裂纹长度是人为规定的，不具有客观性。而依据疲劳损伤累积理论所确定的裂纹形成寿命，其对应的裂纹长度是一个相对客观的参量。本文依据裂纹扩展的累积损伤模型和材料的ε－Ｎ曲线，提出了一种确定缺口试件初始裂纹长度的方法。文中计算了一些材料的初始裂纹长度，并与试验结果和其它文献的结果进行了比较，结果相当吻合，由本文的方法所确定的初始裂纹长度是一个客观参量，它为疲劳寿命分析提供了一个客观的基础，具有实际应用价值。     

An all-digital method for accurate measurements of mechanical deformations

In this paper, an experimental analysis method based on image treatment techniques for the quantitative evaluation of some polycrystal material deformations is presented. This method has been successfully developed for this purpose by adapting and developing algorithms suitable for the images under study. Details of the whole process as applied to a typical example are described and discussed.     

多尺度光斑中心的快速检测

分析了光斑图像成像特点和理想光斑灰度分布模型,针对含有多个不同尺度光斑的图像,提出了一种可以在复杂环境下一次性快速检测出多个光斑中心的方法。该方法基于高斯模糊后光斑中心不变的性质,先对含有大量光斑的图像进行快速多级高斯模糊,构建其高斯尺度空间;然后,使用加速的非极大值抑制方法在尺度空间内寻找多个尺度的局部极值,初步确定各光斑中心的像素级坐标;最后,联合这些坐标的邻域像素,拟合局部曲面,得到光斑中心的亚像素级精确位置。利用仿真实验和实物实验验证了提出方法的有效性。结果表明:该算法对640pixel×480pixel图像,处理时间仅需50ms,每千个光斑的平均检测时间为23ms,在复杂环境下正确率可达89%。此外,该方法对弱光斑较敏感,适合快速处理含有大量不同尺度光斑的图像,并能够有效减少光斑的错检和漏检。由于检测速度快,自适应性强,在实际应用中取得了良好的检测效果。     

Cryo-sectioning and chemical-fixing ultramicrotomy techniques for imaging rubber latex particle morphology

Two methods adapted from biological microscopy are described for a new application in imaging the morphology of rubbery latex particles. In the first method, a drop of latex is frozen in liquid nitrogen, sectioned with a diamond knife and vapour-stained with osmium tetroxide, then viewed by transmission electron microscopy. When applied to latexes made by emulsion polymerization of methyl methacrylate in a natural rubber latex seed, inclusions are clearly visible. A chemical fixation method is then described for imaging the morphology of such rubbery latex particles. Glutaraldehyde is added to the latex, followed by osmium tetroxide. The sample is then dehydrated in ethanol, epoxy resin added, and the sample cured, ultramicrotomed, and imaged with transmission electron microscopy. An inclusion morphology is again clearly seen.     

大型精密转台高精度角度微驱动装置的研制

针对用于标定和检测的大型精密转台(要求其定位误差≤±0.5″),研制了高精度角度微驱动装置。介绍了转台的总体结构,给出了角度微驱动装置的驱动原理和构成。该角度微驱动装置主要通过一个角位移转换机构把精密直线位移转化为精密角位移来实现高的角度分辨率,其在驱动转台旋转的过程中几乎不给转台带来轴向力和径向力,因此不影响转台的轴系精度。为了满足定位要求,转台设计采用了粗精结合、二次定位的方法,即先采用力矩电机进行粗定位,然后使用角度微驱动装置来实现精定位。最后,从理论上计算了角度微驱动装置的分辨率并进行了测试和应用验证,证明此角度微驱动装置的分辨率优于0.08″,满足转台定位精度要求。