查看更多>>摘要：Microtextures of quartz sand grains can be used to establish sedimentary provenance of sedimentary deposits. V-shaped percussion cracks (Vs), which are randomly produced by grain-to-grain mechanical collision in high-energy subaqueous environments, are significant microtextures used for investigation of fluvial and marine sediment. In previous studies, others have used the percentage of microtextures obtained by scanning electron microscope to compare sediment samples. We developed a new method of measurement and evaluation of the surface of quartz grains using a confocal laser scanning microscope (CLSM) and applied the method to coastal sands containing quartz grains with abundant Vs. The method using international-standard surface-roughness parameters (ISO 25178) is useful for evaluating surface textures of quartz grains and for quantifying the structures of Vs (such as aperture area, density, and depth). The results of applying the method to coastal sands suggest that the density of Vs related to the coastal geological setting, that the depth of Vs related to wave height and offshore gradient, and that the size of Vs was not influenced by grain size or mineral composition of the coastal sands. This new method can corroborate preceding methods in provenance study of quartz grains in subaqueous environments. In principle, it also could apply to other types of microtextures and other minerals, such as degrees of weathering on surfaces of heavy minerals. This method, using a CLSM, has the potential to be applied to various provenance studies using grain-surface texture.
查看更多>>摘要：This study describes a method to quantify phosphorus grain boundary segregation by Energy Dispersive X-ray Spectroscopy in Scanning Transmission Electron Microscope (STEM-EDX). A “box-type method” is employed, removing the long-discussed problems of interaction volume and the beam broadening effect. The proposed methodology also introduces a novel way of subtracting the spectrum background to remove the influence of coherent Bremsstrahlung and spurious peaks. A Fe-P model alloy was used to compare the box method to the quantification results previously obtained by atom probe tomography on two high angle grain boundaries. The results are specifically reported in surface concentration (atom/nm2) to avoid additional hypotheses and allow the results between the two techniques to be directly compared. The measurements show that the box-type method can accurately measure phosphorus intergranular segregation in iron.
查看更多>>摘要：Whole sample microscopy mappings are of interest in many cases as they provide analytical information of phases varying in size by orders of magnitude and in composition across the sample. These benefits are amplified if more than one microscopic technique is used for the mappings. However, to take full advantage of correlative whole sample mappings, the data of each technique has to be carefully prepared, treated, correlated and evaluated. With this work, we want to present the key steps of our data treatment approach as well as the results on an exemplary sample, the Chelyabinsk meteorite. The most important step in our data treatment approach is to start by evaluating the spectral maps separately as far as possible (at-% quantification for EDS for example) and then generate pseudo spectral maps from this evaluation in the form of image stacks. This allows us to preserve the advantages of specialized software packages and standard work flows for every spectral mapping, whilst also unifying the data format and compressing the data sufficiently for correlation and the application of machine learning tools. We have performed whole sample mappings using SEM, EDS and Raman on a cross-section of a Chelyabinsk meteorite fragment, roughly 1.0cm × 0.8cm large. Combining these mappings into a single “super” spectral map, we were able to produce a uniquely detailed mapping of the composition of the meteorite fragment, as well as perform a quantitative analysis of the elemental composition of several crystallographic phases. The results of our compositional analysis; olivine (Fo72Fa28), pyroxene (≈ 97 % En80Fs20Wo0 and 3 % En56Fs6Wo38), feldspar (albite), troilite, FeNi (taenite and kamacite), merrillite, chromite and hydroxyapatite; agree qualitatively with other reports from literature.
查看更多>>摘要：Iron-Sulfur (Fe-S) clusters are essential for life, as they are widely utilized in nearly every biochemical pathway. When bound to proteins, Fe-S clusters assist in catalysis, signal recognition, and energy transfer events, as well as additional cellular pathways including cellular respiration and DNA repair and replication. In Eukaryotes, Fe-S clusters are produced through coordinated activity by mitochondrial Iron-Sulfur Cluster (ISC) assembly pathway proteins through direct assembly, or through the production of the activated sulfur substrate used by the Cytosolic Iron-Sulfur Cluster Assembly (CIA) pathway. In the mitochondria, Fe-S cluster assembly is accomplished through the coordinated activity of the ISC pathway protein complex composed of a cysteine desulfurase, a scaffold protein, the accessory ISD11 protein, the acyl carrier protein, frataxin, and a ferredoxin; downstream events that accomplish Fe-S cluster transfer and delivery are driven by additional chaperone/delivery proteins that interact with the ISC assembly complex. Deficiency in human production or activity of Fe-S cluster containing proteins is often detrimental to cell and organism viability. Here we summarize what is known about the structure and functional activities of the proteins involved in the early steps of assembling [2Fe-2S] clusters before they are transferred to proteins devoted to their delivery. Our goal is to provide a comprehensive overview of how the ISC assembly apparatus proteins interact to make the Fe-S cluster which can be delivered to proteins downstream to the assembly event.
查看更多>>摘要：Heteropyxis natalensis Harv. is a native South African tree used in traditional medicine among Venda and Zulu communities. In this study, micromorphological investigations using light and scanning electron microscopy identified long, tapered non-glandular trichomes on the abaxial and adaxial surfaces of the leaves. The total number of trichomes appeared to be greater on emergent leaves and decreased as leaves matured. In addition, schizolysigenous secretory cavities and druse crystals were found within the leaves. Swollen subdermal secretory cavities were also distributed in the midrib of the leaves. Transmission electron microscopy confirmed the presence of nuclei, plastids, mitochondria, vesicles, rough endoplasmic reticulum cisternae and Golgi bodies in the secretory epithelia of these cavities. Various histochemical tests revealed the presence of alkaloids, phenolics, lipids, proteins, essential oils, resin acids and trace amounts of unesterified pectins and polysaccharides in the leaves. This study provides new findings and contributes to the existing research regarding H. natalensis with respect to the micromorphology, ultrastructure and histochemical composition of this species.
查看更多>>摘要：This paper describes an innovative way of using environmental scanning electron microscopy (ESEM) and the development of a suitable accessory to perform in situ observation of living seedlings in the ESEM. We provide details on fabrication of an accessory that proved to be essential for such experiments but inexpensive and easy to build in the laboratory, and present our in situ observations of the tissue and cell surfaces. Sample-specific configurations and optimized tuning of the ESEM were defined to maintain Arabidopsis and flax seedlings viable throughout repetitive exposure to the imaging conditions in the microscope chamber. This method permitted us to identify cells and tissues of the live plantlets and characterize their surface morphology during their early stage of growth and development. We could extend the application of this technique, to visualize the response of living cells and tissues to exogenous enzymatic treatments with polygalacturonase in Arabidopsis, and their interaction with hyphae of the wilt fungus Verticillium dahliae during artificial infection in flax plantlets. Our results provide an incentive to the use of the ESEM for in situ studies in plant science and a guide for researchers to optimize their electron microscopy observation in the relevant fields.
查看更多>>摘要：This study presents a new protocol for preparing bone samples for scanning electron microscopy (SEM) using a room temperature ionic liquid (RTIL) treatment method. RTIL-based solutions can be adopted as an alternative to lengthy and laborious traditional means of preparation for SEM due to their unique low-vapour pressure and conductive properties. Applied to biological samples, RTILs can be used quickly and efficiently to observe hydrated, unfixed structures in typical SEM systems. This first-time feasibility study of the optimization of this protocol for bone was explored through various SEM modalities using two distinct ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMI][BF4]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMI][BF4]), at varying concentrations of 5, 10, and 25 % v/v in aqueous solution through an addition-based method. Based on qualitative observations in the SEM, a 60-second solution addition treatment of 10 % v/v [BMI][BF4] performed the best in imaging hydrated, unfixed bone samples, resulting in minimal charge buildup and no solution pooling on the surface. The treatment was applied effectively to a variety of bone samples, notably flat and polished, as well as highly topographical bone fracture surfaces of both healthy and osteoporotic human bone samples. In comparison to conventionally dehydrated bone, the RTIL treatment better preserved the natural bone structure, resulting in minimal microcracking in observed structures.
查看更多>>摘要：Biomaterials have a great potential to improve human health, however in vitro and in vivo studies are necessary to provide information on their efficacy and safety. This study reports on a comprehensive evaluation of core-shell electrospun fibers loaded with silver nanoparticles (Ag NP) where the delivery rate was controlled by different sizes of Ag NP and thermoresponsive poly(n-isopropylacrylamide) (PNIPAM) hydrogel particles. Fiber meshes also contain zinc oxide nanoparticles (ZnO NP), to improve pore structure for controlled release of Ag NP. In vitro cytotoxicity studies using cultured human A549 epithelial cells demonstrated that the ZnO NP component, which is known to cause cytotoxicity, of the fiber meshes did cause measurable cell death. In vitro antibacterial efficacy of the fiber meshes was shown with rapid and efficient growth inhibition in E. coli bacterial culture. Fiber meshes were implanted subcutaneously for up to 27 days in male and female C57BL/6 mice to evaluate the in vivo drug release and biocompatibility. Hyperspectral microscopy was used as an advanced tool to determine precise location of released Ag NP into the skin compared to the conventional tissue staining methods. Results suggested that Ag NP were continuously released over 27 days of implantation in mice. Hyperspectral imaging revealed that released Ag NP dispersed in the dermis of male mice, however, Ag NP accumulated in the hair follicles of female mice (Figure). Mice implanted with fiber meshes containing ZnO NP had better hair regrowth and wound healing, which was in contrast to in vitro cytotoxicity results. These findings suggest that these newly developed fiber meshes can have unique long-term release of drugs loaded in the fiber core and appear to be biocompatible. The differences in the sex-bias outcome suggest the opportunity for development of sex-specific drug delivery systems.
查看更多>>摘要：During the last several decades, since the discovery of a decagonal quasicrystal, a 2 nm cluster model has been widely accepted as its basic quasi-unit-cell (QUC). Instead of the traditional 2 nm QUC, a 3.2 nm QUC is proposed in this paper. The 3.2 nm QUC can fill all the blank areas. The 3.2 nm QUC consists of 251 atoms. The element type and position of each atom are determined using high-angle annular detector dark-field (HAADF) images taken along three projection directions, i.e., one along the ten-fold symmetry and the other two along the two-fold symmetry with an intersection angle of 18 degrees. The proposed model opens an avenue for further investigation of the aperiodic atomic structure of other quasicrystals.
查看更多>>摘要：The histological structure of the avian pineal gland during embryonic life has so far only been studied in chickens. It is known that the pineal organs of hatched chickens and turkeys differ significantly from each other based on their morphology and physiology. The aim of the present study was to investigate the histological structure of the embryonic pineal gland of domestic turkeys. The study was performed on turkey embryos aged 4–28 days. Along with histological analyses, three-dimensional (3D) images of the pineal glands from embryos aged 6–28 days were also obtained. In four-day-old embryos [embryonic day (ED) 4], primary evagination of the pineal gland from the neuroectoderm of the diencephalon was observed. On ED 6, the evagination formed a pineal recess with a thick and folded wall. In the next embryonic stages, the pineal recess was lengthened to the pineal canal, with the lumen opening to the third ventricle. The connection of the pineal lumen with the ventricular lumen was observed in all studied embryos. The first cellular rosettes without the lumen separated from the wall of the pineal recess occurred on ED 6. Several small and round follicles containing their own lumens were visible on ED 8. On ED 10, the pineal parenchyma was composed mainly of small, round follicles. The first oval follicles appeared on ED 12 and branched follicles appeared on ED 16. In some embryos at different stages, follicles formed from secondary evaginations of the diencephalon epithelium were observed. The turkey pineal organ maintained the follicular type of parenchyma without solid cellular aggregates throughout embryonic life. The pineal follicles originated from: 1) rosettes arising from the wall of the pineal canal (from ED 6); 2) an accessory evagination occurring in the neuroectoderm anteriorly and posteriorly to the pineal canal end (from ED 6); 3) direct development in the walls of larger follicles and detaching from them in a manner similar to the budding process (from ED 14); and 4) fusion of smaller follicles into branched ones. The pineal capsule started to develop on ED 6, first as a vascularization and later as a thin mesenchymal outline around the apical part, then at the dorsal and at the end the ventral part of the pineal gland. The pineal stroma was composed of mesenchymal tissue consisting of abundant in cells and blood vessels. The first evagination of the choroid plexus in the diencephalon was observed on ED 8. The attachment of the pineal gland to the dura mater first occurred on ED 16. Finally, the pineal gland of ED 28 embryos consisted of a wide proximal part attached to the dura mater and a narrow distal part that extended into the pineal stalk, which extended to the intercommissural region of the diencephalon. The present study revealed the occurrence of significant morphological differences in the developing embryonic pineal gland of turkeys compared with chickens.
NSTL
Elsevier