Urbisz, Anna Z.Chlond, DominikBugaj-Nawrocka, AgnieszkaChajec, Lukasz...
21页
查看更多>>摘要：Hybridisation is still a widely studied phenomenon that allows us to look at some processes differently. However, obtaining fertile hybrids, which we might consider in the long term as precursors of a new species, is still a field that requires research. Much of the research done so far indicates that hybrids are sterile - either sex or both. It is influenced by various mechanisms, both prezygotic and postzygotic reproductive isolation. Thanks to the use of light and transmission electron microscopy, our research has made it possible to understand, at least partially, the causes of infertility in male hybrids resulting from the crossing of two Afrotropical species of the genus Platymeris Laporte, 1833. The analysis of microscopic images showed that one of the possible causes of the infertility of hybrids might be spermatogenesis, during which sperm cells were not formed. In turn, the use of scanning electron microscopy revealed potential abnormalities in the structure of the hybrid eggshell. Moreover, karyotyping analyses suggest possible causes of infertility at the genetic level.
查看更多>>摘要：The 3D morphology of hierarchically structured electrocatalytic systems is determined based on multi-scale Xray computed tomography (XCT), and the crystalline structure of electrocatalyst nanoparticles is characterized using transmission electron microscopy (TEM), supported by X-ray diffraction (XRD) and spatially resolved near edge X-ray absorption fine structure (NEXAFS) studies. The high electrocatalytic efficiency for hydrogen evolution reaction (HER) of a novel transition-metal-based material system - MoNi4 electrocatalysts anchored on MoO2 cuboids aligned on Ni foam (MoNi4/MoO2@Ni) - is based on advantageous crystalline structures and chemical bonding. High-resolution TEM images and selected-area electron diffraction patterns are used to determine the crystalline structures of MoO2 and MoNi4. Multi-scale XCT provides 3D information of the hierarchical morphology of the MoNi4/MoO2@Ni material system nondestructively: Micro-XCT images clearly resolve the Ni foam and the attached needle-like MoO2 micro cuboids. Laboratory nano-XCT shows that the MoO2 micro cuboids with a rectangular cross-section of 0.5 x 1 mu m(2) and a length of 10-20 mu m are vertically arranged on the Ni foam. MoNi4 nanoparticles with a size of 20-100 nm, positioned on single MoO2 cuboids, were imaged using synchrotron radiation nano-XCT. The application of a deep convolutional neural network (CNN) significantly improves the reconstruction quality of the acquired data.
查看更多>>摘要：Understanding how defects are generated and propagate during operation in modern vertical cavity surface emitting lasers (VCSEL) is an important challenge in order to develop the next generation of highly reliable semiconductor lasers. Undesired oxidation processes or performance degrading dislocation networks are typically investigated by conventional failure analysis after damage formation. In this works new approach to VCSEL failure analysis, oxide confined high power VCSELs are investigated in-situ at elevated temperatures in a transmission electron microscope. At high temperatures, lateral oxidation of the current confinement layer as well as formation and propagation of dislocations are observed. The experimental results may deepen the understanding of defect generation in VCSELs during stress tests or standard operating conditions. On the other hand, in-situ TEM proofed to be a promising technique to be utilised in future VCSEL failure analysis, possibly leading to the development of improved defect models and increased VCSEL reliability.
查看更多>>摘要：In this study we present quantitative X-ray computed microtomography measurements (mu CT) of retained sub micron-sized particles in open porous media carried out in a laboratory mu CT setup. Due to the polychromatic spectrum of the used X-rays, the tomograms are affected by various non-linear artifacts, which belong to the class of beam hardening artifacts. These artifacts become more dominant, when the amount of retained particles increases and can affect wide areas of the images, making a qualitative and quantitative analysis barely possible. Furthermore, the colloidal depositions show an inhomogeneous distribution inside the filter, making a reliable material discrimination between filter and particle material challenging. We introduce a calibration method, which is capable to sufficiently remove the majority of the artifacts by linearization of the projection data and thus enabling the precise material quantification of the retained colloids in the reconstructed tomograms. While most beam hardening correction routines are only applicable to homogeneous materials, our algorithm takes into account inhomogeneous material distributions and is adapted to multi-material systems. Moreover, the method includes a material discrimination of the colloids and the filter in the raw data domain. Thus, erroneous segmentations at the interfaces between different material fractions are avoided. As a result we present quantitative concentration maps of the particle distribution inside the porous media with a resolution of < 10 mu m. A series of validation samples was prepared, covering a wide range of different, representative filter loading stages. The accuracy of the particle quantification was evaluated from these samples and the relative deviation of the overall contained particle mass was less than 10% in all cases, partially even less than 1%. The overall image quality due to the artifact removal was significantly improved. The local variation of the particle concentration could be well assessed from the obtained concentration maps.
查看更多>>摘要：Standardless Energy dispersive spectroscopy (EDS) on polished samples of Portland cement clinker is routinely performed both for unhydrated phases as well as in cement pastes. Typically, the calcium to silica ratio is investigated. EDS analyses are highly dependent on the polishing quality of the sample. It is thus worth studying the Ca/Si ratios of cement phases in a clinker since they can be used as a reference. Indeed, alite (Ca3SiO5 or C3S in cement chemistry notation) and belite (Ca2SiO4 or C2S) should have an atomic Ca/Si ratio of 3 and 2, respectively. EDS carried out under the scanning electron microscope (SEM) is routinely used on polished samples to assess the composition of such phases. In the present study, Ca/Si ratios are investigated on a commercial clinker polished at various steps (6, 3, 1 and 0.25 mu m diamond pastes, 0.05 mu m alumina). All along the polishing process, ratios are coherent with theoretical ones and with the reference ones obtained by electron probe microanalysis (EMPA) in the present study.
查看更多>>摘要：Porous silicon carbide composite ceramics were prepared by partial sintering method and sacrificial silicon, with phenolic resin applied as carbon template, and silicon powder as silicon source and pore-forming agent. It showed a composite structure of SiC/SiO2/SiC sandwich shell structure and SiC/SiOX heterojunction nanofiber. Through an investigation into the effect of carbon-silicon atomic ratio on the structure and thermodynamic properties of porous SiC. It was revealed that the carbon network formed by the phenolic resin played a role in restricting the position of the silicon powder and building a regularly-arranged porous SiC structure. The pre-pared samples reached a porosity of 50-75% while exhibiting a low thermal conductivity ranging from 0.74 to 1.3 W/(m.K), which is attributed to the nanoscale phonon dispersion mechanism and nanofiber thermal insulation, together with high stiffness. Porous ceramics demonstrate both mechanical and thermal insulation properties, which makes them applicable as thermal protection materials for hypersonic aircraft. This is effectively in reducing the aerodynamic thermal effects of hypersonic aircraft.
查看更多>>摘要：Hypoxia is a key factor in tumor microenvironments. Tumor-derived exosomes under hypoxia have their functions of communication between local and remote cells, and play an important role in tumor growth and metastasis. However, the effect of tumor-derived exosomes on cell structures and functions under hypoxia is unknown. In this work, the effects of exosomes derived from hepatocellular carcinoma cells (HCC-LM3) under normoxia (N-exos) and hypoxia (H-exos) environments on the biological and physical properties of target cells were stduied. The N-exos promoted the proliferation of hepatocytes (HL-7702) at 1.5 mg/mL, while the H-exos promoted the proliferation of hepatocytes at a lower concentration (1.0 mg/mL). After the cells cultured with the same concentrations of N-exos and H-exos for different time periods, the cell migration was enhanced. The stress fibers of the cells became loose and the cytoskeleton was rearranged, which were time dependent. The changes in morphological and mechanical parameters of the HL-7702 cells were detected by atomic force microscopy (AFM). The results showed that the cell edges became irregular and the filopodia were increased versus the exosomes treatment time. The heights and elastic moduli of cells were reduced. Compared with N-exos, H-exos had a more significant effect on the biological and physical properties of target cells. The results provide a method for studying how tumor-derived exosomes affect the interaction between tumor cells and their hypoxic microenvironment.
查看更多>>摘要：Cardiovascular/heart tissue and cells are subjected to dynamic forces from very early development, without pause, for the entire life of the animal or person and are characterized by being very sensitive to the mechanical properties of the surrounding tissue. Most cardiovascular diseases are characterized by important modifications that occur at the level of extracellular matrix (ECM) components that correlate with an increase in tissue stiffness and contribute to impaired heart function. Additionally, several studies show that cardiovascular/heart cells themselves can undergo modifications in their morphology and mechanical properties in various biological processes as well as in different pathologies. This mini review illustrates how atomic force microscopy (AFM) indentation can be used in combination with different experimental strategies to access the mechanical properties of cardiovascular/heart tissue and cells, which can help in understanding the different biological and pathological processes in these types of tissues and cells in depth.
查看更多>>摘要：The insufficient pollinator visitation is the most important limitation of fruit and seed production, which is common and ubiquitous in entomophilous angiosperms. The scent and attractive colours with flower guides and such floral rewards as nectar, pollen, and oil are important attractants for insects visiting and pollinating flowers in the family Iridaceae. The aim of this study was to investigate the morphology of flowers and the micromorphology, anatomy, and ultrastructure of floral nectaries in the rare and endangered species Iris sibirica with the use of light, scanning, and transmission electron microscopes and histochemical assays. Osmophores in the form of papillae were located on the adaxial surface of outer tepals and on the abaxial surface of the stylodium channel. The nectaries were located on the inner surface of the perianth tube and were composed of a single layered epidermis with papillae and several layers of glandular parenchyma with vascular bundles. I. sibirica nectaries represent the presecretory starch-accumulating type, where nectar is released for a short time immediately after flower opening. Nectar was produced throughout the flower lifespan in both male and female stages. It was secreted in the granulocrine mode and released through microchannels in the reticulate cuticle of nectary papillae. Transport of pre-nectar components proceeded via symplastic and apoplastic pathways. The nectary epidermal cells with papillae and glandular parenchyma cells contained total lipids, acidic lipids, and polysaccharides, whereas the epidermal cells with papillae additionally contained neutral lipids and polyphenol compounds. The nectaries and nectar production in I. sibirica flowers share the common location and follow several secretion patterns characteristic for the nectaries in some members of the family Iridaceae and the subfamily Iridoideae. Nevertheless, the mode of nectar release through the cuticle of epidermal papillae has been described in Iridaceae family for the first time. The visual, aromatic, and food attractants characteristic of I. sibirica flowers probably stimulate potential visits by pollinators, but the short nectar secretion period may limit the effectiveness of pollinators and sexual reproductive success.
查看更多>>摘要：Transmission electron microscopy (TEM) is used to observe the atomic structures of materials. Environmental TEM (ETEM) is a method wherein a gas can be evaluated and it has been used to observe the dynamic reaction between materials and gases at the atomic level. An electron beam (EB), which has a sufficiently high energy (exceeding a few tens of kilovolts), can be used to ionize gas molecules. Subsequently, the ionized molecules might react with the materials during ETEM. Therefore, the current generated by the ions and electrons were measured to verify the presence of ions generated due to the ionization of the N-2 gas atmosphere during EB irradiation in ETEM. The electron energy loss spectra (EELS) were acquired from the N-2 gas atmosphere to es-timate the types of ions generated. The results demonstrated that ions and electrons were generated in the N-2 atmosphere during ETEM and EB irradiation. Moreover, the EELS analysis indicated that the generated ion was N-2(+). The material observation conducted using gas ETEM can detect the reaction between gases, ions, and materials.
NSTL
Elsevier