A method for preparing powdered specimens for transmission electron microscopy

A new method of preparing TEM samples from powders is described. The method consists of compacting epoxy-powder composite mixtures in special molds by centrifuging prior to polymerization. The compact is then ion milled by standard methods. Samples prepared in this way are currently being used to study dislocation structures developed during processing of ceramic powders.     

The fatty acid monolayer technique for preparing frozen-hydrated specimens

A major difficulty in preparing frozen-hydrated specimens from solutions is to control an optimal thickness of water remaining on the EM grid just before it is immersed in liquid nitrogen. In this report, we describe a modification of the fatty acid monolayer technique for preparing frozen-hydrated specimens. With the use of this technique, all excess solvent is removed when a behenic acid (a fatty acid) monolayer film is picked up over the surface of the electron microscope grid. Low-dose electron diffraction patterns and optical diffraction patterns of low-dose micrographs of bacteriorhodopsin (bR) of Halobacterium halobium thus prepared show strong reflection orders at a resolution of ∽4 Å and ∽10 Å, respectively. Because the preparation of thin, hydrated specimens by the behenic acid monolayer technique does not depend upon evaporation of water, a dramatic change of ion concentration and pH is not expected to occur. The method should be applicable to specimens which need to be kept in a specific buffer and/or at a specific ionic strength.     

A technique for preparing human dermal and scar specimens for scanning electron microscopy

The aims in a current study of dermis and scar tissue using the scanning electron microscope are:

• 1 to maintain the orientation of the specimen
• 2 to preserve the in vivo architecture, and
• 3 to expose a satisfactory surface.

A technique which best fulfils these requirements involves glutaraldehyde fixation of a splinted specimen, freeze-fracturing using a modified pair of pliers, freeze-drying, incubation in a buffered saline solution of hyaluronidase and freeze-drying again after washing. Consistently satisfactory specimens have been obtained, which provide information about fibre architecture and cell distribution.     

A new freeze-etch unit for freeze-etch rotary shadowing, low temperature freeze-fracturing and conventional freeze-etching.

A new freeze-etch unit is described in which one can make replicas where hydrated, frozen, fractured specimens rotate during specimen heavy metal shadowing. The freeze-etch unit can also be used to do low temperature freeze-fracturing and conventional freeze-etching.     

Efficient embedding technique for preparing small specimens for stereological volume estimation: zebrafish larvae

Stereological sampling regimes, in particular volume and number estimation, often require systematic uniformly random sections throughout a specimen. A method has been developed to increase the efficiency of preparing fish larvae for sectioning prior to histological or stereological analysis. Embedding a group of larvae in a resin block using this technique greatly reduces the quantity of sections produced and allows easy assessment of sample groups. Saving time in this way therefore makes stereology a more viable research tool.     

Technique for preparing cross-section transmission electron microscopy specimens from ceramic oxide braze joints

A method for preparing cross-section transmission electron microscopy specimens from alumina and partially stabilized zirconia braze joints is described. The technique relies on masking a mechanically dimpled 3mm disc in order to avoid preferential thinning of the metallic braze filler alloy during ion milling. The results presented show that specimens made by this technique are suitable for characterizing the fine microstructural details of interfacial reactions at oxide surfaces that occur during brazing.     

Critical point drying for scanning electron microscopy: a semi-automatic method of preparing biological specimens.

Slow, controlled, rates of critical point bomb heating and of gas venting have been shown to improve the preservation of biological specimens in critical point drying. A procedure that represents a balance between avoidance of specimen damage and speed of operation has been developed for use with CO2 as the transitional fluid. Bomb heating is automated and controlled electronically, and manual venting of the gaseous CO2 is monitored using a gas flow meter.     

An inexpensive system for classifying tool wear states using pattern recognition

The purpose of this research work is to develop an inexpensive model tool wear sensing system using pattern recognition. Accordingly, the combined output of radial force, feed force and acoustic emission (r.m.s. value) is utilized to model the tool flank wear in a turning operation. The tool wear sensing system consists of two phases: training and classification. The training phase is done off-line and is used to determine the weight coefficients for the linear decision functions using the prototype patterns from the cutting tests. The classification phase is in real time. In the first stage of the classification phase, the minimum distance classifier selects a prototype (conditions already trained) cutting test that is closest to the cutting test to be performed. The linear decision functions of the prototype test selected are used for classifying the incoming signal of the actual cutting test into one of three wear classes.

The success rate of training for various tests varied between 39.57% and 100%. The success rate of classifying signals from actual tests was also encouraging, demonstrating that the proposed methodology can be successfully applied to predict the status of the cutting tool on-line using low budget equipment.     

An inexpensive device for freeze drying and plastic embedding tissues at low temperatures

The preparation of biological tissues for electron microscopy by rapid freezing retains the original localization of ions and molecules. A reproducible freezing regime was established by quenching tissues in liquid propane according to the method of Elder et al. (1981). Tissue was thereafter freeze dried in a custom built freeze drying device with a liquid nitrogen cooled stage to prevent ice recrystallization during drying. The device was also designed to allow the vacuum embedding of tissue in low temperature resin such as Lowicryl® and polymerization in situ. This paper describes the design of the device and an example of its use in the freeze drying of cartilage. The results show that minimal ice damage occurs to the chondrocytes and that intracellular organelles are clearly visible. The regime described may prove a useful and pragmatic alternative to cutting tissue in the frozen state. Translocation of elements is unlikely except perhaps in the case of very labile elements such as Na and K, but this remains to be fully elucidated.     

气体流量计自动检定装置

介绍了气体流量计自动检定装置的软件和硬件组成、系统功能 ,分析了影响系统准确度的因素     

Preparation and mechanical requirements for freeze-etching thick-walled plant tissues*

The freeze-etching technique is useful in studying cells from higher plant tissues even when thick cell walls are present. However, such cells require special consideration both in preparation for the freeze-etching process as well as during fracturing and subsequent stages. Modifications to the technique and to the apparatus are described which make it possible to freeze-etch thick-walled plant tissues more successfully than by employing other methods.     

An inexpensive and highly efficient device for observing a transmitted electron image in SEM

An inexpensive, efficient device that supplies a transmission mode to the conventional SEM has been developed. The transmitted electrons strike a metal plate, and these generate secondary electrons that are proportional to the quantity of the transmitted electrons. The generated electrons are collected by the secondary electron detector. Hence, the performance of this device is influenced by the number of secondary electrons generated in the metal plate. In order to construct a device that can attain the best transmitted electron image, the signal-to-noise ratio of images, obtained from various trial devices, were measured by a newly-developed digital image processing program. When the material and shape of the device are selected, to produce high-secondary emission, the efficiency of the device compares with that of a relatively expensive standard detector system (scintillator detector).