Microscopy and Microanalysis最新文献

Considerable inroads have recently been made on algorithms to determine the sample potential from four-dimensional scanning transmission electron microscopy data from thick samples where multiple scattering cannot be neglected. This paper further develops the scattering matrix approach to such structure determination. Through simulation, we demonstrate how this approach can be modified to better handle partial spatial coherence, unknown probe defocus, and information from the dark field region. By combining these developments we reconstruct the electrostatic potential of a monolithic SrTiO3 crystal showing good quantitative agreement with the expected structure.

In the elastic scattering regime, probe position-averaged convergent beam electron diffraction (PACBED) patterns have proven robust for estimating specimen thickness and mistilt. Through simulation, we show that core-loss-filtered PACBED patterns can be used to measure the site occupancy of a small concentration of dopants in an otherwise known crystal structure. By leveraging the reciprocity between scanning and conventional transmission electron microscopy, we interpret core-loss PACBED patterns using a strategy traditionally used for determining dopant concentrations via energy dispersive X-ray spectroscopy. We show that differences in the interaction range of different elements hinder a purely measurement-based quantification strategy, but that this can be overcome through comparison with simulations that generalize the Cliff-Lorimer k-factors.

An approach to characterize dopant spatial inhomogeneity at the nanoscale along with its local chemical environment has been developed using atom probe tomography. We achieve this through the combination of a local composition analysis using the nearest-neighbor atoms combined with a nonparametric Kolmogorov-Smirnov or Anderson-Darling statistical test. Using an in situ highly boron-doped silicon germanium layer we demonstrate that all three elements have an inhomogeneous distribution. Moreover, by subdividing the local dopant composition distribution, a correlation between the boron doping level and variations in the surrounding matrix composition was determined. These atomic-scale measurements provide new experimental insights into the dopant incorporation behavior in technologically relevant semiconductors and its relationship to the epitaxial growth processes.

Zoophytophagous insects, such as Podisus nigrispinus (Dallas, 1851) (Heteroptera: Pentatomidae), play an important role in maintaining agroecosystem balance. However, the anatomy, histology, and ultrastructure of their Malpighian tubules remain poorly understood. This study aimed to describe these features in P. nigrispinus. Adults were dissected, and their Malpighian tubules were examined using light and transmission electron microscopy. Anatomically, P. nigrispinus possesses four convoluted Malpighian tubules that open independently at the junction between the midgut and ileum. The tubules are lined by a single layer of cuboidal epithelial cells, characterized by a well-developed apical brush border, cytoplasm rich in vacuoles, and a spherical nucleus with predominantly decondensed chromatin. Transmission electron microscopy revealed apical microvilli, numerous electron-lucent vesicles, spherocrystals with concentric contents, rough endoplasmic reticulum profiles, mitochondria, and autophagosomes. In the basal region, the plasma membrane displays long invaginations forming wide extracellular spaces closely associated with mitochondria. These structural features suggest high metabolic activity. This is the first detailed description of the Malpighian tubules in P. nigrispinus, contributing to a better understanding of the excretory physiology of zoophytophagous predatory Hemiptera.

Carbonate minerals such as calcite cover a significant portion of Earth's ice-free land surface. Beyond their widespread distribution, they play a critical role in geological processes, including the global carbon cycle and various biogeochemical processes. Understanding the crystal chemistry of carbonates is therefore essential for advancing our knowledge of these systems. Atom probe tomography offers promising potential for revealing nanoscale chemical and isotopic processes in minerals; however, its application to carbonates remains technically challenging due to their poor thermal conductivity and absorption. In this study, we apply and adapt an in situ metallic coating technique and optimize atom probe tomography acquisition parameters for calcite. The results demonstrate that applying a Cr coating to calcite specimens significantly improves experimental yield and enhances mass resolution during atom probe analysis. Despite these improvements, the data do not yield stoichiometric proportions for calcite due to the post-ionization dissociation of CxOy molecules into neutrals. These findings provide a framework for extending atom probe tomography methods to other poorly conducting or beam-sensitive materials.

Stereomicroscopes are routinely used across disciplines for material and surface characterization due to their simplicity of use and minimal specimen preparation requirements. However, the stereomicroscope transillumination design is suboptimal, as a single incident beam at the specimen plane is shared and transmitted via two laterally offset detection axes. This flaw limits life science applications due to the transparent nature of samples which results in poor contrast images. We use a single additional element in the illumination path to correct the illumination uniformity across the field of view and, by doing so, enhance image contrast and facilitate detection of refractive structures in transparent biological specimens. We designed and fabricated an integrated lens-biprism element using low-cost, consumer-grade 3D printing methods and consumables. This 3D printed lens-biprism distributed diverging rays from a single incandescent light source into two parallel beams that converged at the specimen plane and transmitted through the respective left and right detection axes of a stereomicroscope. This improved transillumination setup increased the image contrast by up to 67.62% compared with the conventional stereomicroscope setup. We demonstrated the benefit of the lens-biprism element by visualizing dynamic cellular events in live tissue and discerning refractive structures more easily in transparent specimens.

Peroxisomes are dynamic organelles that play important roles in cellular metabolic and signaling pathways and are implicated in several disease conditions. Although a detailed comprehension of peroxisome dynamics is crucial in various contexts of health and disease, its accurate assessment still presents significant challenges, mainly due to their morphological heterogeneity. Here, we discuss different strategies to study peroxisome dynamics and present a semi-automated macro, PeroxiDynA, that enables the analysis of peroxisome dynamics from single-plane confocal images of mammalian cells in ImageJ. Our findings confirm that PeroxiDynA can be successfully employed to determine relative peroxisome number and spatial distribution. A comparison between PeroxiDynA and other image analysis strategies reveals that it results in increased reliability in the analysis of peroxisome abundance and morphology. Although future improvements are still required to minimize the time and limitations imposed during analysis of peroxisomal features, we propose that PeroxiDynA is a useful tool for biomolecular studies, not only to analyze peroxisomes but also the dynamics of small biological structures in cells from mammals and other organisms.

Four-dimensional scanning transmission electron microscopy (4D-STEM) is powerful for rapidly characterizing arrays of nanoparticles produced via high-throughput synthesis. However, such 4D-STEM datasets typically contain thousands of nanoparticles, each characterized by thousands of diffraction patterns spatially distributed across the nanoparticle, necessitating efficient and comprehensive analysis. We propose an end-to-end segmentation framework to automatically segment each nanoparticle into regions with distinct composition/orientation of crystal grains, using only the 4D-STEM data. Bragg disk information is extracted in a physics-informed manner from the diffraction patterns at each spatial location and combined with the real space coordinates to form feature vectors. These feature vectors are then used as inputs to a Gaussian mixture model (GMM) to segment the nanoparticle into distinct regions. We also develop two visualization tools based on the GMM outputs to infer the interface transition and the degree of superposition. Our framework comprehensively integrates machine learning tools and physics knowledge, and provides a basis for substantially compressing enormous 4D-STEM datasets, e.g., by replacing the full 4D-STEM dataset for each nanoparticle with only a single set of Bragg disk features for each distinct crystal grain identified in the nanoparticle. We demonstrate the power of our framework by presenting results for real, complex datasets.

The histomorphological features of the internal system in insects are considered important for understanding their biology. Julodis ehrenbergii Laporte, commonly known as the "jewel beetle or metallic wood-boring beetle," belongs to the family Buprestidae, and it is generally known that it feeds on pistachio, oak, blackberry apricot, and Alhagi mannifera Jaub. & Spach plants. This research reports for the first time the histomorphological features of the hindgut of adult J. ehrenbergii using light and scanning electron microscopy. Some characteristics, such as the epithelial layer, cuticle layer, and cross-sectional shape of regions belonging to the hindgut, were described in detail. Three regions that have a straight tubular structure are covered with a muscle layer and tracheal network. The epithelium of the whole hindgut is made up of cuboidal cells. The cuticle layer located on the apical surface of the cells is distinguished as endocuticle and exocuticle. These findings not only provide a foundation for understanding the hindgut morphology of J. ehrenbergii but also offer insights into the evolutionary adaptations of Coleoptera, contributing to broader entomological and ecological studies.