Abstract: To optimize specimen-processing protocols for investigations of fertilization in mammals, with high-resolution, low-voltage scanning electron microscopy (LVSEM), bovine oocytes matured in vitro were prepared by either aldehyde fixation, conductive staining, or high-pressure cryoimmobilization with freeze-substitution. Samples prepared by these different preparative techniques were coated with either platinum or gold and imaged with an LVSEM operating at 1.5 keV. Additionally, aldehyde-fixed oocytes, sputter-coated with gold, were imaged with a conventional scanning electron microscope (cSEM). The results show that bovine oocytes prepared by aldehyde fixation or cryoimmobilized by high-pressure freezing produced superior images of the zona pellucida (ZP) compared with those from the conductive stained samples. A comparison of LVSEM and cSEM images suggests that the gold-coating employed in cSEM preparation obscures the ZP detail seen with the LVSEM, but not with the cSEM. Application of these procedures provide not only a new view of the ZP but may be useful in elucidating the molecular mechanism of gamete interactions during the fertilization process.

Abstract: We have developed a method for the examination of atomic force microscopy (scanning force microscopy) tips using a high-resolution transmission electron microscope (TEM). The tips can be imaged in a nondestructive way, enabling one to observe the shape of an atomic force microscope probe in the vicinity of the apex with high resolution. We have obtained images of atomic force microscopy probes with a resolution on the order of 1 nm. The tips can be imaged repeatedly, so one can examine tips before and after use. We have found that the tip can become blunted with use, the rate of wear depending upon the sample and tip materials and the scanning conditions. We have also found that the tips easily accrue contamination. We have studied both commercially produced tips, as well as tips grown by electron beam deposition. Direct imaging in the TEM should prove useful for image deconvolution methods because one does not have to make any assumptions concerning the general shape of the tip profile.

Abstract: Interactions among discrete charges in the emission current of a photoelectron imaging system can limit its spatial resolution, significantly affecting the performance and design of emission microscopes employing high current densities. Under intense laser illumination a sample can emit photocurrent densities exceeding tens of amperes/cm2. This study describes Monte Carlo estimations of electron trajectory aberrations produced by discrete electron space charge interactions in a photoelectron emission microscope. The results also apply to photoelectron sources that might be used in other kinds of devices. A model of the emission process was used to assemble bunches of about 500 randomly positioned electrons whose individual trajectories were computed. Trajectory distortions of one member in each bunch that were due to the coulomb forces exerted by its neighbors were used to evaluate aberrations for a variety of voltages, current densities, and instrument configurations. Aberrations estimated in this way are smaller than those predicted by earlier theory or obtained in pulsed imaging experiments. Here we discuss the reasons for these differences, offer suggestions for improved instruments, and present experimental images.

Abstract: This work reports the distribution of a large, representative sample population of grain boundary plane crystallography in pure, annealed copper by use of an improved experimental procedure. The new methodology reduces the laboriousness and improves the accuracy of data collection, and so is described in detail. Analysis of the results concentrates on the Σ3 boundaries, and shows that three-quarters of these were tilt boundaries on the 011 zone. Of these tilt boundaries, nearly half were coherent twins, i.e., on 111/111 planes, or near coherent twins on 23,17,17/775 planes. The high population of the second group is thought to be due to oxygen take-up during annealing. The data in general showed a trend for lower energy Σ3s to occur more frequently. The results were interpreted in terms of boundary energies, local equilibration, and comparisons with previous work in copper and other systems.

Abstract: Because of their chemical properties, bacterial capsules tend to collapse during dehydration before electron microscopy. The purpose of this study is thus to evaluate the use of monoclonal antibodies (mAbs) against capsular material to stabilize and visualize bacterial capsule. Two important porcine pathogens with a known ultrastructure, namely, Actinobacillus pleuropneumoniae and Streptococcus suis, were used. Our data indicate that mAbs, either immunoglobulin G (IgG) or IgM, preferably from ascite fluids, can be used to stabilize bacterial capsular material in preparation for electron microscopy. However, because of their low antibody titer, the use of mAbs from culture supernatants is not recommended.

Abstract: Since 1972 the author and colleagues at Ford Motor Company have been publishing results of materials analyses which were obtained using ambient temperature or cryomicrotomy as one of the sample preparation techniques. Generally two types of sectioning, thin and ultrathin, were pursued for light-optical and electron-optical microscopy, respectively. These papers include the study of the following materials, which have been separated into nine classes: polymer composites, polymer blends, reverse osmosis membranes, carbon fibers, elastomers, automotive exhaust catalysts, aluminum surface coatings, aluminum alloy automotive wheels, and rapidly solidified aluminum alloys. This review is not intended to reiterate the conclusions of these prior publications but will provide the reader with an insight into the many ways microtomy can be used for materials studies.

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