Spectral imaging in the scanning electron microscope (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer has the potential to be a powerful tool for chemical phase identification, but the large data sets have, in the past, proved too large to efficiently analyze. In the present work, we describe the application of a new automated, unbiased, multivariate statistical analysis technique to very large X-ray spectral image data sets. The method, based in part on principal components analysis, returns physically accurate (all positive) component spectra and images in a few minutes on a standard personal computer. The efficacy of the technique for microanalysis is illustrated by the analysis of complex multi-phase materials, particulates, a diffusion couple, and a single-pixel-detection problem.

The environmental cell device discussed in this paper provides a modest low-vacuum scanning electron microscopy (SEM) capability to a standard SEM without requiring additional pumping. This environmental cell confines a volume of low vacuum in contact with the sample surface using a container that has an aperture for admitting the primary electron beam. The aperture is large enough to permit a limited field of view of the sample, and small enough to limit the outflow of gas into the SEM chamber to that which can be accommodated by the standard SEM pumping system. This environmental cell also functions as a gaseous detector device.

A new single-tilt technique for performing TEM stereomicroscopy of strain fields in crystalline materials has been developed. The technique is a weak beam technique that involves changing the value of g and/or sg while tilting across a set of Kikuchi bands. The primary benefit of the technique is it can be used with single-tilt TEM specimen holders including many specialty holders such as in situ straining, heating, and cooling holders. Standard stereo-TEM techniques are almost always limited to holders allowing two degrees of rotational freedom (i.e., double-tilt or tilt/rotation holders). An additional benefit of the new technique is that it eliminates the need to focus with the specimen height control. These advantages make it useful for stereo viewing or for quantitative stereomicroscopy provided necessary consideration is given to errors that may result from the technique.

In this article, we show that nanometer-sized precipitates of atomic numbers higher than those of the surrounding crystalline matrix can be clearly revealed in a conventional transmission electron microscope by high-angle, centered dark-field imaging after minimizing the diffraction contrast. The effect is similar to that of Z-contrast STEM, albeit with a spatial resolution limited to 1 nm. Its sensitivity to atomic number differences between precipitates and matrix is about 10, which is demonstrated for precipitates formed after Er, Ge, Cr, and Si ion implantation into SiC.

Ionization of atoms is the first step in many analytical procedures. The cross section for ionizing a particular atomic shell is essential for calculating the magnitude of analytical signals. Calculations using atomic wave functions for various shells of all elements relevant for X-ray microanalysis over a range of electron energies up to 400 keV were performed. The calculations for high energies above threshold can be considerably simplified by using the mathematical form of the Bethe ridge that dominates the scattering in this region. Corrections for exchange at low energies above threshold are incorporated in these calculations. A selection of results showing the effects of different approximations on ionization cross sections for K, L, and M shells is presented.

Microscopy has played a critical role in first identifying and then defining the role of lysosomes in formation of atherosclerotic foam cells. We review the evidence implicating lysosomal lipid accumulation as a factor in the pathogenesis of atherosclerosis with reference to the role of microscopy. In addition, we explore mechanisms by which lysosomal lipid engorgement occurs. Low density lipoproteins which have become modified are the major source of lipid for foam cell formation. These altered lipoproteins are taken into the cell via receptor-mediated endocytosis and delivered to lysosomes. Under normal conditions, lipids from these lipoproteins are metabolized and do not accumulate in lysosomes. In the atherosclerotic foam cell, this normal metabolism is inhibited so that cholesterol and cholesteryl esters accumulate in lysosomes. Studies of cultured cells incubated with modified lipoproteins suggests this abnormal metabolism occurs in two steps. Initially, hydrolysis of lipoprotein cholesteryl esters occurs normally, but the resultant free cholesterol cannot exit the lysosome. Further lysosomal cholesterol accumulation inhibits hydrolysis, producing a mixture of cholesterol and cholesteryl esters within swollen lysosomes. Various lipoprotein modifications can produce this lysosomal engorgement in vitro and it remains to be seen which modifications are most important in vivo.

The development of Leydig cells in mammals has been widely described as a biphasic pattern with two temporally mature Leydig cell populations, fetal stage followed by the adult generation beginning at puberty. In the present study, mouse Leydig cells were examined for apoptosis during postnatal testis development using electron microscopy and in situ DNA fragmentation by terminal deoxynucleotidyl transferase staining (TdT). Both the morphological study and the DNA fragmentation analysis showed that cellular death by apoptosis did not occur in Leydig cells during the neonatal, prepubertal, puberty, and adult periods. From these results, we suggest that the remaining fetal Leydig cells in the neonatal testis are associated with the involution or degeneration processes. In contrast, in the prepubertal and puberty stages, fragmentation of apoptotic DNA was detected in germ cells present in some seminiferous tubules.

At present, mechanisms by which specific structural and mechanical properties of the three-dimensional extracellular matrix microenvironment influence cell behavior are not known. Lack of such knowledge precludes formulation of engineered scaffolds or tissue constructs that would deliver specific growth-inductive signals required for improved tissue restoration. This article describes a new mechanical loading–imaging technique that allows investigations of structural–mechanical properties of biomaterials as well as the structural–mechanical basis of cell–scaffold interactions at a microscopic level and in three dimensions. The technique is based upon the integration of a modified, miniature mechanical loading instrument with a confocal microscope. Confocal microscopy is conducted in a reflection and/or fluorescence mode for selective visualization of load-induced changes to the scaffold and any resident cells, while maintaining each specimen in a “live,” fully hydrated state. This innovative technique offers several advantages over current biomechanics methodologies, including simultaneous visualization of scaffold and/or cell microstructure in three dimensions during mechanical loading; quantification of macroscopic mechanical parameters including true stress and strain; and the ability to perform multiple analyses on the same specimen. This technique was used to determine the structural–mechanical properties of three very different biological materials: a reconstituted collagen matrix, a tissue-derived biomaterial, and a tissue construct representing cells and matrix.

One of the most interesting aspects of this book is the frequency at which the contributing authors are found in the references at the end of not one, but usually several chapters: this is by no means a mistake. Editors Hacker and Gu have assembled a wealth of expertise from well-known individuals in the fields of autometallography, immunogold-silver staining and molecular morphology. Composed of 16 chapters with a total of 32 contributing authors, the material is presented in a very well organized and coherent format.