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Cross striation in human permanent and deciduous enamel measured with confocal Raman microscopy
摘要： Dental enamel is the most mineralized tissue in the human body and has a very complex organization. The aim of the present study was to evaluate chemical composition and orientation of crystals in human enamel cross striation using confocal Raman microscope. Slices of teeth were prepared and scanned using a confocal Raman microscope. Cross striation spacing was calculated according to the variation of PO4 3? peak intensity. The measurements showed a characteristic length between two cross striations of 2.70 (SD 0.43) μm for permanent teeth and 1.75 (SD 0.37) for deciduous teeth. Ratios between OH and PO4 3? peaks, for 0 and 90 degrees angulation, are, respectively, 9.18 (SD 0.80) and 44.74 (SD 3.12) for decidual teeth, and 11.72 (SD 1.46) and 22.12 (SD 3.15) for adult teeth. This confirmed that the hydroxyapatite crystal is well oriented along the enamel prism, as reported in the literature, but with a significant increase in deciduous teeth. K‐mean cluster binary images were calculated to compare the ratio of the centroid peaks of the cross striation zone and inter cross striation material. The regions corresponding to inner prism, included cross striations, are more mineralized than the outer part of enamel prism. In the prism, the Pearson correlation test was performed based on the intensity of hydroxyapatite characteristic peaks (ν1 PO4 3?, ν1 CO3 2?, and OH). The variations were well correlated: These results indicated that cross striations corresponded to the variation of hydroxyapatite concentration and not to a variation of crystals orientation.
关键词： Raman microscopy,cross striation,enamel prism,K‐mean cluster analysis,decidual teeth
更新于2025-09-23 15:23:52
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Progrès dans les méthodes diagnostiques du déficit en cellules souches limbiques. Apport de la microscopie confocale et de la tomographie en cohérence optique
摘要： The limbus is the anatomical and functional barrier between corneal and conjunctival epithelia. It is characterized by presence of the limbal stem cell niche which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views, parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, even with sub-epithelial fibrosis. Optical coherence tomography in central cornea and at the limbus, with scans in different orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective sub-epithelial fibrosis.
关键词： Limbal stem cell deficiency,Limbus,Optical coherence tomography,In vivo confocal microscopy
更新于2025-09-23 15:23:52
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[Methods in Molecular Biology] T-Cell Motility Volume 1930 (Methods and Protocols) || Live Cell Imaging and Analysis to Capture T-Cell Motility in Real-Time
摘要： T-lymphocytes are the principle coordinators of the immune defense system and play a major role in the protection of our body against infections, intruders of non-self, and malignancies. To mount an immune response, T-cells need to be effectively employed to tissue sites of infection or in?ammation and establish contacts with antigen-presenting cells (APCs) or malignant cells. Understanding how T-cells navigate toward their recruitment sites would offer new therapeutic opportunities. Advancement in the hardware and software upgrades of microscopy technology has created several ef?cient and easy-to-operate live cell imaging platforms. In this protocol, we present a generalized and simple-to-follow protocol for live cell imaging of migrating T-cells, which can also be adopted to visualize real-time tracking of intracellular signaling events.
关键词： Advanced microscopy,Cell tracking,Live cell imaging,T-cell migration
更新于2025-09-23 15:23:52
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Surface potential tailoring of PMMA fibers by electrospinning for enhanced triboelectric performance
摘要： Triboelectric generators rely on contact-generated surface charge transfer between materials with different electron affinities to convert mechanical energy into useful electricity. The ability to modify the surface chemistry of polymeric materials can therefore lead to significant enhancement of the triboelectric performance. Poly(methyl methacrylate) (PMMA) is a biocompatible polymer commonly used in medical applications, but its central position on the triboelectric series, which empirically ranks materials according to their electron-donating or electron accepting tendencies, renders it unsuitable for application in triboelectric generators. Here, we show that the surface potential of PMMA fibers produced by electrospinning can be tailored through the polarity of the voltage used during the fabrication process, thereby improving its triboelectric performance, as compared to typically spin-coated PMMA films. The change in surface chemistry of the electrospun PMMA fibers is verified using X-ray photoelectron spectroscopy, and this is directly correlated to the changes in surface potential observed by Kelvin probe force microscopy. We demonstrate the enhancement of triboelectric energy harvesting capability of the electrospun PMMA fibers, suggesting that this surface potential modification approach can be more widely applied to other materials as well, for improved triboelectric performance.
关键词： Energy harvesting,Triboelectric generator,Surface chemistry,Kelvin probe force microscopy,Electrospinning,Poly(methyl methacrylate)
更新于2025-09-23 15:23:52
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Suppressed Triplet Exciton Diffusion Due to Small Orbital Overlap as a Key Design Factor for Ultralong-Lived Room-Temperature Phosphorescence in Molecular Crystals
摘要： Persistent room-temperature phosphorescence (RTP) under ambient conditions is attracting attention due to its strong potential for applications in bioimaging, sensing, or optical recording. Molecular packing leading to a rigid crystalline structure that minimizes nonradiative pathways from triplet state is often investigated for efficient RTP. However, for complex conjugated systems a key strategy to suppress the nonradiative deactivation is not found yet. Here, the origin of small rates of a nonradiative decay process from triplet states of conjugated molecular crystals showing RTP is reported. Optical microscopy analysis showed that, despite a favorable molecular stacking, an aromatic crystal with strong RTP is characterized by small diffusion length and small values of the diffusion coefficient of triplet excitons. Quantum chemical calculations reveal a large overlap between the lowest unoccupied molecular orbitals but very small overlap between the highest occupied molecular orbitals (HOMOs). Inefficient electron exchange caused by the small overlap of HOMOs prevents triplet excitons from diffusing over long distances and consequently from quenching at defect sites inside the crystal or at the crystal surface. These results will allow design of comprehensive molecular structures to obtain molecular solids with more efficient RTP.
关键词： suppressed nonradiative rate,persistent room-temperature phosphorescence,triplet exciton diffusion,molecular orbital overlap,fluorescence microscopy
更新于2025-09-23 15:23:52
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[Advances in Imaging and Electron Physics] || superconductors and magnetic electron lenses
摘要： The use of superconductors seems a logical step if one wants to make iron-free magnetic lenses or to reduce the dimensions of conventional lenses since, when decreasing the coil size, the current density is increased. In the 1960s and 1970s, research mainly concentrated on the applicability of superconductors to magnetic electron lenses, and took place on a relatively large scale. This is reviewed in Section 2, after a general introduction into superconductivity in Section 1. Superconducting lenses and microscopes did not become popular due to their inconvenient operation and the lack of interest in high-voltage electron microscopy. High-voltage microscopy has been one of the main reasons for working on strong magnetic lenses and, consequently, on the utilization of superconductors. In 1986, with the discovery of high-temperature superconductivity, discussion on the applicability of superconductors to magnetic electron lenses was reopened. In the past, one of the most serious disadvantages in operating superconducting lenses had been related to the use of liquid helium refrigeration, so high-T c superconductors might be employed to overcome this problem, because their cooling demands are much more relaxed. However, especially during the first years of high-Tc superconductivity, despite their high operating temperatures, the materials themselves seemed extremely unfriendly, as they were brittle, sensitive to water, unstable, and difficult to produce. Fortunately, most of these disadvantages have now disappeared and the discussion concerning their utilization assumes a more fundamental character in the sense that most of the properties of the high-Tc materials are known, though a sound theoretical basis has not yet been defined. The properties of high-T c superconductors are the subject of Section 3. The question whether high-Tc superconductors are more appropriate for applications in particle optics than their classical counterparts was considered to be an interesting research topic. Therefore, this work was started as a feasibility study to the use of high-temperature superconductors in particle optics. Most short-term applications in this field were expected to exploit the high current density of these materials at temperatures above liquid helium, so this work concentrated on magnetic lenses as one of the most straightforward high current density applications. Since conventional iron circuit lenses are already used to their limits, as set by the saturation of the ferromagnetic circuit, significant improvements are to be expected only from iron-free lenses or highly saturated pole piece lenses. Their performance is restricted by the current density allowed in the windings and, further, for the iron-free lens, by the attainable mechanical tolerances, since, in the absence of iron, a lack of axial symmetry in the windings directly results in parasitic aberrations. For making small iron free lenses, high-Tc thin films are potentially interesting candidates, as they possess a high current density and can be patterned very accurately using lithographic techniques. Advantages to be expected from thin film lenses are smaller dimensions and better optical properties. An overview of fabrication techniques for high-Tc thin films is given in Section 4. The first attempt to make a coil in a superconducting thin film, using co-evaporated YBa2Cu3O7?x films, is the subject of Section 5. A thin film has to be patterned with some form of spiral in order to obtain a coil. Therefore, thin film lenses basically do not possess full axial symmetry. The relationship between the geometry of a flat coil and its optical properties is given in Section 6. The geometry of a feasible thin film lens element, along with its corresponding optical properties, is given in Section 7 while the technology used to fabricate this lens element is the subject of Section 8. Finally, based upon the work presented here, Section 9 treats the potential applicability of high-Tc superconductors in instruments that employ particle beams.
关键词： magnetic electron lenses,High-Tc superconductors,thin films,capacitive alignment,lens design,YBa2Cu3O7?x,superconductivity,electron microscopy
更新于2025-09-23 15:23:52
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Single Particle Tracking and Super-Resolution Imaging of Membrane-Assisted Stop-and-Go Diffusion and Lattice Assembly of DNA Origami
摘要： DNA nanostructures offer the possibility to mimic functional biological membrane components due to their nanometer-precise shape configurability and versatile biochemical functionality. Here we show that the diffusional behavior of DNA nanostructures and their assembly into higher order membrane-bound lattices can be controlled in a stop-and-go manner and that the process can be monitored with super-resolution imaging. The DNA structures are transiently immobilized on glass-supported lipid bilayers by changing the mono- and divalent cation concentrations of the surrounding buffer. Using DNA-PAINT super-resolution microscopy, we confirm the fixation of DNA origami structures with different shapes. On mica-supported lipid bilayers, in contrast, we observe residual movement. By increasing the concentration of NaCl and depleting MgCl2, a large fraction of DNA structures restarts to diffuse freely on both substrates. After addition of a set of oligonucleotides that enables three Y-shaped monomers to assemble into a three-legged shape (triskelion), the triskelia can be stopped and super-resolved. Exchanging buffer and adding another set of oligonucleotides triggers the triskelia to diffuse and assemble into hexagonal 2D lattices. This stop-and-go imaging technique provides a way to control and observe the diffusional behavior of DNA nanostructures on lipid membranes that could also lead to control of membrane-associated cargos.
关键词： single-particle tracking,DNA origami,diffusion,super-resolution microscopy,lipid membrane,DNA nanotechnology
更新于2025-09-23 15:23:52
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Caesium-Incorporated Triple Cation Perovskites Deliver Fully Reversible and Stable Nanoscale Voltage Response
摘要： Perovskite solar cells that incorporate small concentrations of Cs in their A-site have shown increased lifetime and improved device performance. Yet, the development of fully stable devices operating near the theoretical limit requires understanding how Cs influences perovskites’ electrical properties at the nanoscale. Here, we determine how the chemical composition of three perovskites (MAPbBr3, MAPbI3, and Cs-mixed) affects their short- and long-term voltage stabilities, with <50 nm spatial resolution. We map an anomalous irreversible electrical signature on MAPbBr3 at the mesoscale, resulting in local Voc variations of ~400 mV, and in entire grains with negative contribution to the Voc. These measurements prove the necessity of high spatial resolution mapping to elucidate the fundamental limitations of this emerging material. Conversely, we capture the fully reversible voltage response of Cs-mixed perovskites, containing small amounts of Cs, FA, and Br, demonstrating that the desired electrical output persists even at the nanoscale. The Cs-mixed material presents no spatial variation in Voc, as ion motion is restricted. Our results show that the nanoscale electrical behavior of the perovskites is intimately connected to their chemical composition and macroscopic response.
关键词： ion motion,MAPbI3,Cs-mixed perovskite,MAPbBr3,nanoscale voltage,perovskite solar cells,Kelvin probe force microscopy
更新于2025-09-23 15:23:52
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Direct Imaging of Isofrequency Contours of Guided Modes in Extremely Anisotropic All-Dielectric Metasurface
摘要： In this work, we investigate an all-dielectric metasurface based on the silicon on insulator platform for manipulating of guided modes in the visible and near-infrared spectral ranges. We use the Fourier modal method to demonstrate numerically, that guided modes excited in the metasurface support both hyperbolic-like and elliptic dispersion regimes. We implement a back focal plane microscope combined with a high refractive index solid immersion lens to directly image the isofrequency contours of the guided modes (surface waves). Reconstruction of dispersion unambiguously reveals the transition between different dispersion regimes.
关键词： Fourier microscopy,All-dielectric metasurface,isofrequency contours,Fourier modal method,dispersion reconstruction,surface waves
更新于2025-09-23 15:23:52
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Abrupt changes in the graphene on Ge(001) system at the onset of surface melting
摘要： By combining scanning probe microscopy with Raman and x-ray photoelectron spectroscopies, we investigate the evolution of CVD-grown graphene/Ge(001) as a function of the deposition temperature in close proximity to the Ge melting point, highlighting an abrupt change of the graphene’s quality, morphology, electronic properties and growth mode at 930 °C. We attribute this discontinuity to the incomplete surface melting of the Ge substrate and show how incomplete melting explains a variety of diverse and long-debated peculiar features of the graphene/Ge(001), including the characteristic nanostructuring of the Ge substrate induced by graphene overgrowth. We find that the quasi-liquid Ge layer formed close to 930 °C is fundamental to obtain high-quality graphene, while a temperature decrease of 10 degrees already results in a wrinkled and defective graphene film.
关键词： Chemical Vapor Deposition,Germanium,Scanning Tunneling Microscopy,Catalysis,Graphene
更新于2025-09-23 15:23:52