The orientation of fibers in assemblies such as nonwovens has a major influence on the anisotropy of properties of the bulk structure and is strongly influenced by the processes used to manufacture the fabric. To build a detailed understanding of a fabric’s geometry and architecture it is important that fiber orientation in three dimensions is evaluated since out-of-plane orientations may also contribute to the physical properties of the fabric. In this study, a technique for measuring fiber segment orientation as proposed by Eberhardt and Clarke is implemented and experimentally studied based on analysis of X-ray computed microtomographic data. Fiber segment orientation distributions were extracted from volumetric X-ray microtomography data sets of hydroentangled nonwoven fabrics manufactured from parallel-laid, cross-laid, and air-laid webs. Spherical coordinates represented the orientation of individual fibers. Physical testing of the samples by means of zero-span tensile testing and z-directional tensile testing was employed to compare with the computed results.

Until recently, three-dimensional reconstruction on an ultrastructural level was only possible using serial section transmission electron microscopy (ssTEM). However, ssTEM is highly challenging and prone to artifacts as, e.g., section loss and image distortions. New methods, such as serial block-face scanning electron microscopy (SBFSEM) overcome these limitations and promise a high lateral resolution. However, little is known about the usability of SBFSEM in diminutive, but highly complex cellular systems. We used spider sperm (~3 µm in diameter), which fulfills these conditions, to analyze the potential of SBFSEM compared with ssTEM. Our data suggest that the resolution obtained by SBFSEM allows depicting structures on a cellular level and is sufficient to discriminate subcellular components, but is highly dependent on previous staining procedures and electron density of the target structures.

Confocal Raman microspectroscopy (CRM) has emerged as a powerful approach to visualize the compositional distribution in lignocellulosic biomass of cell walls. In this work, the applicability of CRM for imaging the topochemical correlation between lignin and hydroxycinnamic acids (HCA) in the Miscanthus sinensis internode was explored. Model compound [p-coumaric acid (PCA) and ferulic acid (FA)] analysis indicated that the band region from 1,152 to 1,197 cm−1 can be used to characterize the distribution of HCA. Raman images calculated by integrating over the area intensity of characteristic spectral regions showed heterogeneous distribution of lignin and HCA at cellular and sub-cellular level. When overlaying the Raman image of lignin and HCA distribution, it was found that these two polymers were co-located in the middle lamella and secondary wall of corresponding cells. Raman images for the band intensity ratio (1,173 cm−1/1,603 cm−1) indicated a clear association between lignin and HCA distribution within morphologically distinct cell wall layers of sclerenchyma fibers and the parenchyma. This is the first time that the spatial correlation between lignin and HCA concentration has been illustrated by a microspectroscopy imaging approach. The results are of importance in extending the current understanding of lignin and aromatics topochemistry in herbaceous biomass.

High quality fixation often inactivates epitopes and gentler fixation can fail to preserve biological structure at the required resolution. For studies of male reproduction, immunofluorescence techniques using paraformaldehyde fixation associated with paraffin as an embedding medium gives good epitope preservation, although the cell becomes morphologically compromised. On the other hand, glutaraldehyde associated with a plastic resin has been used with success to recognize and distinguish each spermatogonial cell subtype, but the antigenic sites become inaccessible to antibodies. Here we describe a new method that provides excellent morphological details of testicular cells while preserving the binding capacity of epitopes. Using a combination of glutaraldehyde and paraformaldehyde as a fixative and LR White resin for embedding, we show that it is possible to clearly recognize spermatogonial subtypes (Aund, A–A4, In and B spermatogonia) on 1-μm thick-sections and to label epitopes such as bromodeoxyuridine, a marker used for cellular cycle studies in the testis. The information gained from this procedure can be critical for understanding spermatogonial process of self-renewal and differentiation.

Since semiconductor devices are being scaled down to dimensions of several nanometers there is a growing need for techniques capable of quantitative analysis of dopant concentrations at the nanometer scale in all three dimensions. Imaging dopant contrast by scanning electron microscopy (SEM) is a very promising method, but many unresolved issues hinder its routine application for device analysis, especially in cases of buried layers where site-specific sample preparation is challenging. Here, we report on optimization of site-specific sample preparation by the focused Ga ion beam (FIB) technique that provides improved dopant contrast in SEM. Similar to FIB lamella preparation for transmission electron microscopy, a polishing sequence with decreasing ion energy is necessary to minimize the thickness of the electronically dead layer. We have achieved contrast values comparable to the cleaved sample, being able to detect dopant concentrations down to 1×1016 cm−3. A theoretical model shows that the electronically dead layer corresponds to an amorphized Si layer formed during ion beam polishing. Our results also demonstrate that contamination issues are significantly suppressed for FIB-treated samples compared with cleaved ones.

In low-energy electron microscopy (LEEM) we commonly encounter images which, beside amplitude contrast, also show signatures of phase contrast. The images are usually interpreted by following the evolution of the contrast during the experiment, and assigning gray levels to morphological changes. Through reconstruction of the exit wave, two aspects of LEEM can be addressed: (1) the resolution can be improved by exploiting the full information limit of the microscope and (2) electron phase shifts which contribute to the image contrast can be extracted. In this article, linear exit wave reconstruction from a through-focal series of LEEM images is demonstrated. As a model system we utilize a heteromolecular monolayer consisting of the organic molecules 3,4,9,10-perylene tetracarboxylic dianhydride and Cu-II-Phthalocyanine, adsorbed on a Ag(111) surface.

In the preparation process for scanning electron microscopy (SEM), flexed silkworm embryos typically assume several curled shapes with irregular postures that obscure morphological details during SEM observation. We describe a preparation technique based on glycerol substitution for better SEM visualization of straight and flat silkworm embryos. Glycerol has high viscosity, low vapor pressure, and sufficient electrical conductivity. Silkworm embryos were infiltrated with glycerol and arranged in a straight posture or flattened using a cover slip. Samples were directly observed by SEM without additional dehydration, drying, or coating procedures. The complete ventral side could be easily viewed in one image. Recoating alleviated the charging phenomenon. This represents a simple method for preparation of straight and flat samples from curled biological specimens for SEM observation.

Closed form analytical equations used to calculate the collection solid angle of six common geometries of solid-state X-ray detectors in scanning and scanning/transmission analytical electron microscopy are presented. Using these formulae one can make realistic comparisons of the merits of the different detector geometries in modern electron column instruments. This work updates earlier formulations and adds new detector configurations.