共查询到20条相似文献，搜索用时 15 毫秒
1.
2.
3.
4.
5.
Doughty MJ 《Microscopy research and technique》2012,75(4):474-483
AIMS: To evaluate measurements of collagen fibril spacing using different shaped regions of interest (ROI) on transmission electron micrograph (TEM) images of rabbit corneal stroma. METHODS: Following glutaraldehyde fixation and phosphotungstic acid staining, TEM images of collagen fibrils in cross section were projected at a final magnification close to 250,000 × to obtain overlays. Interfibril distances (IFDs; center‐to‐center spacing) were measured within different ROIs of the same nominal area (0.25 μm2) but different shape (with the length to width, L:W, ratio from 1:1 to 6:1). The IFD distribution was analyzed, and the 2D organization assessed using a radial distribution analysis. RESULTS: The fibrils had an average diameter of 35.3 ± 3.8 (SD) nm, packing density of 393 ± 4 fibrils / μm2 and a fibril volume fraction of 0.39 ± 0.02. IFDs ranged from 29 to 1400 nm depending on the shape of the ROI, with average values ranging from 263 to 443 nm. By artificially selecting IFD data only to a radial distance of 250 nm, the average IFDs were just 145–157 nm. The radial distributions, to 250 nm, all showed a nearest neighbors first peak which shifted slightly from predominantly at 45–54 nm with more rectangular ROIs. The radial distribution profiles could be shown to be statistically different if the ROI L:W ratio was 2:1 or greater. CONCLUSION: Selection of an ROI for assessment of packing density and interfibril distances should be standardized for comparative assessments of TEMs of collagen fibrils. Microsc. Res. Tech., 2011. © 2011 Wiley‐Liss, Inc. 相似文献
6.
Objective: This study was carried out to observe the enzymatic degradation of human dentin collagen fibrils exposed to exogenous collagenase in situ using atomic force microscopy, to understand the characteristics of the enzymatic degradation of collagen fibrils on dentin specimens. Methods: Polished dentin specimens from caries‐free third molars were etched with citric acid, and then treated with an aqueous solution of 6.5% NaOCl for 120 s. The specimen was then put into a fluid cell and treated with a mixed solution of collagenase I (MMP‐1) and collagenase II (MMP‐8) for 9 h. AFM with contact mode was performed in situ to monitor the enzymatic degradation process of the dentin collagen fibrils. The distinctly topographic changes of the dentin surface were recorded continuously during different stages of the enzymatic degradation process. Results: The mixed solution of exogenous collagenase I and collagenase II could degrade dentin organic matrix (mainly collagen) efficiently, and the structures of dentin substrate were clearly exposed. Conclusion: It is possible to carry out real‐time observations on the enzymatic biodegradation process of human dentin collagen fibrils on dentin specimens with atomic force microscopy in situ. By this means, the fine structures of the etched dentin substrate were clearly revealed, possibly contributing to the related study of human dentin in vitro. 相似文献
7.
Moretto SG Azambuja N Arana-Chavez VE Reis AF Giannini M Eduardo Cde P De Freitas PM 《Microscopy research and technique》2011,74(8):720-726
Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (μTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to μTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest μTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin. 相似文献
8.
Terenzio Congiu Ugo E. Pazzaglia Petra Basso Daniela Quacci 《Microscopy research and technique》2014,77(9):653-660
Transverse and longitudinal sectioning of undecalcified cortical bone is a commonly employed technique for investigating the lamellar structure of the osteons. Since a flat surface is required, the specimen has to be grinded and then polished. Whereas the smear of debris and inorganic/organic deposits left by these treatments cannot be removed by ultrasonication alone, a chemical treatment of the specimen surface with either a basic or an acid etching solution is currently employed. A further effect of the latter can be the enhancement of the lamellar bone pattern. The kind of etching solution, its pH, the concentration of etchants, and the contact time significantly affect the sectioned surface when it is observed with scanning electron microscopy (SEM). The etching procedures can severely influence the obtained images. Homogeneous cortical bone specimens were sampled from the first metatarsal of two fresh human subjects. One or two cut surfaces were exposed to different acid and basic solutions in bonded conditions. Considering the type of chemical agents, the solution pH, and the exposure time of the specimens, the effects of several etching media have been investigated and compared. Strong etching, either acid or basic produced surface decalcification and severe damage of the collagen matrix, compromising any morphological or morphometric analysis. Weak acid etching (for example citric and acetic acid), even though causing distinctive alteration of the sample, enhanced the visibility of the lamellar pattern, while the polyphosphate treatment of the surface decalcified a thin layer matrix, ensuring a good visibility of fibrils and avoiding rough distortions. Microsc. Res. Tech. 77:653–660, 2014. © 2014 Wiley Periodicals, Inc. 相似文献
9.
Young Chan Lee Ho Jung Kim Kyung Sook Kim Samjin Choi Sung Wan Kim Hun‐Kuk Park Young Gyu Eun 《Microscopy research and technique》2015,78(7):569-576
There continues to be a paucity of data regarding the nanostructural changes of vocal fold (VF) collagen after injury. The aim of this study is to investigate the nanostructural and morphological changes in the rabbit VF lamina propria following acute injury using atomic force microscopy (AFM). Unilateral VF injury was performed on 9 New Zealand breeder rabbits. Sacrifice and laryngeal harvest were performed at three time points: 1 day, 3 days, and 7 days after injury. Histology and immunohistochemistry data were collected to confirm extracellular matrix (ECM) changes in rabbit VF. The progressive changes in thickness and D‐spacing of VF collagen fibrils were investigated over a 7‐day postinjury period using AFM. At post‐injury day 1, a fibrin clot and inflammatory cell infiltration were observed at the injured VF. The inflammatory score at postinjury day 1 was highest in injured VF tissue, with a significant decrease at postinjury day 7. The immunoreactivity of inflammatory proteins (COX‐2, TNF‐α) was observed in VF up to day 7 after injury. AFM investigation showed clustered and disorganized collagen fibrils at the nanoscale resolution at post‐injury day 7. Collagen fibrils in injured VF at postinjury day 7 were significantly thicker than control and postinjury days 1 and 3 (P < 0.001). D‐spacing of collagen at postinjury day 7 was not studied due to loss of distinct edges resulting from immature collagen deposition. AFM investigation of VF could add valuable information to understanding micromechanical changes in VF scar tissue. Microsc. Res. Tech. 78:569–576, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
10.
Ugo E. Pazzaglia Terenzio Congiu Petra Basso Ivano Alessandri Lucia Cucca Mario Raspanti 《Microscopy research and technique》2016,79(8):691-699
Observation of heat‐deproteinized cortical bone specimens in incident light enabled the high definition documentation of the osteonal pattern of diaphyseal Haversian bone. This prompted a study to compare these images with those revealed by polarized light microscopy, carried out either on decalcified or thin, undecalcified, resin‐embedded sections. Different bone processing methods can reveal structural aspects of the intercellular matrix, depending on the light diffraction mode: birefringency in decalcified sections can be ascribed to the collagen fibrils orientation alone; in undecalcified sections, to both the ordered layout of collagen and the inorganic phase; in the heat‐deproteinized samples, exclusively to the hydroxyapatite crystals aggregation mode. The elemental chemical analysis documented low content of carbon and hydrogen, no detectable levels of nitrogen and significantly higher content of calcium and phosphorus in heat‐deproteinized samples, as compared with dehydrated controls. In both samples, the X‐ray diffraction (XRD) pattern did not show any significant difference in pattern of hydroxyapatite, with no peaks of any possible decomposition phases. Scanning electron microscopic (SEM) morphology of heat‐deproteinized samples could be documented with the fracturing technique facilitated by the bone brittleness. The structure of crystal aggregates, oriented in parallel and with marks of time periods, was documented. Comparative study of deproteinized and undecalcified samples showed that the matrix inorganic phase did not undergo a coarse grain thermal conversion until it reached 500°C, maintaining the original crystals structure and orientation. Incident light stereomicroscopy, combined with SEM analysis of deproteinized bone fractured surfaces, is a new enforceable technique which can be used in morphometric studies to improve the understanding of the osteonal dynamics. Microsc. Res. Tech. 79:691–699, 2016. © 2016 Wiley Periodicals, Inc. 相似文献
11.
李金华;王应啸;姚芳萍 《制造技术与机床》2023,(9):189-195
为了研究VC作为晶粒生长抑制剂对原位生成WC增强镍基涂层的影响,在H13钢表面分别制备了VC含量为0.1%、1.5%、2%的WC增强镍基涂层。熔覆试样经过切割、磨抛、腐蚀处理后,分别采用扫描电镜（SEM）、X射线衍射仪（XRD）、能谱仪（EDS）、显微硬度计、摩擦磨损试验机进行组织、物相、硬度、摩擦磨损性能的分析和测试。结果表明,VC抑制WC颗粒生长的效果显著。随着VC含量的增多,WC颗粒逐渐细化、涂层组织均匀细密。VC抑制剂减缓WC溶解-析出过程以及降低WC表面能是抑制WC晶粒生长的重要原因。随着VC的加入,WC硬质相的生成被抑制,含钒物质增多。WC增强镍基涂层的硬度随VC含量的增加而提高,但当VC含量大于1.5%时,涂层杂质相增多,WC含量减少而导致涂层硬度下降。当VC含量为1.5%时,能有效细化晶粒,提高涂层硬度。添加VC抑制剂的WC增强镍基涂层摩擦磨损性能更优,磨损机理主要为粘着磨损、脆性剥落和磨粒磨损。 相似文献
12.
13.
A method for TEM visualization of the extracellular matrix three-dimensional organization in tissues
A method for obtaining high-resolution three-dimensional images of the extracellular matrix organization in tissues is described. It consists of TEM observation of rotary-shadowed platinum–carbon replicas obtained from critical-point dried resinless sections of polyethylene glycol-embedded specimens. The procedure is simple and rapid, with high rates of sample recovery. An example of its application to EM immunocytochemistry (fibronectin localization) is presented. The utilization of the method to demonstrate cell-extracellular matrix relationships, and its limitations in the study of cells are discussed. 相似文献
14.
Activated sludge flocs are complex consortia of various micro-organisms. The community structures of samples taken from municipal sewage treatment plants were characterized using fluorescently labelled, 16S and 23S rRNA-targeted oligonucleotide probes in combination with confocal scanning laser microscopy (CSLM). In comparison with conventional epifluorescence microscopy, CSLM considerably improved the capability to visualize directly the spatial distribution of defined bacterial populations inside the sludge flocs. Analyses could be performed at high resolution undisturbed by problems such as autofluorescence or limited spatial resolution in thick samples. In addition, CSLM was used to analyse some structural properties of paraformaldehyde-fixed activated sludge flocs, such as floc size and homogeneity. Typical floc sizes were found to be in the range between 5 and 50 μm. Whereas most of the flocs were completely colonized by bacteria, there were also examples of flocs containing gas bubbles or particles in the interior. 相似文献
15.
为了提高钛合金的高温抗氧化性能,推动钛合金在高温和复杂工况环境下的进一步工程应用,利用高能激光束作用下Ti、Al、Nb三种元素混合粉末之间的原位反应在BT3-1钛合金表面制备了高温抗氧化的高铌Ti-Al金属间化合物复合涂层。针对原位反应所制备涂层存在的缺陷,通过自行设计的热处理工艺优化了涂层和界面微观组织。借助光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)分析了热处理前后复合涂层的物相结构及显微形貌。结果表明:热处理前的涂层主要由单质Nb、金属间化合物γ-TiAl、α_2-Ti_3Al、Ti_3Al_2等物相组成;热处理后的复合涂层,单质Nb固溶到γ-TiAl和α_2-Ti_3Al中,同时形成了新相Ti_3AlNb_(0.3),涂层近似为γ-TiAl+α_2-Ti_3Al双相层片状等轴晶组织。此外,涂层中并未观察到减弱抗氧化性的单质Nb颗粒和Ti_3Al_2相,Ti、Al、Nb的宏观偏析得以消除,涂层与基材界面位置的气孔和裂纹均以消失,出现了明显的白亮带冶金结合过渡层,涂层组织也更加均匀致密。热处理对提高钛合金表面Nb的合金化程度和改善Ti-Al金属间化合物的高温抗氧化性能起到了显著的促进作用。 相似文献
16.
In this article, an in situ observation method, combining laser scanning confocal microscopy and electron backscattering diffraction, was used to investigate the morphological and crystallographic evolution of bainite transformation in a Fe‐0.15C binary alloy. The nucleation at a grain boundary and inclusions, sympathetic nucleation, and impingement event of bainitic ferrite were directly shown in real time. The variant evolution during bainite transformation and misorientation between bainitic ferrites were clarified. Strong variant selection was observed during sympathetic nucleation. Microsc. Res. Tech., 2009. © 2009 Wiley‐Liss, Inc. 相似文献
17.
Sriram Vijayan Rongxuan Wang Zhenyu Kong Joerg R. Jinschek 《Microscopy research and technique》2022,85(4):1527-1537
Studies on materials affected by large thermal gradients and rapid thermal cycling are an area of increasing interest, driving the need for real time observations of microstructural evoultion under transient thermal conditions. However, current in situ transmission electron microscope (TEM) heating stages introduce uniform temperature distributions across the material during heating experiments. Here, a methodology is described to generate thermal gradients across a TEM specimen by modifying a commercially available MEMS-based heating stage. It was found that a specimen placed next to the metallic heater, over a window, cut by FIB milling, does not disrupt the overall thermal stability of the device. Infrared thermal imaging (IRTI) experiments were performed on unmodified and modified heating devices, to measure thermal gradients across the device. The mean temperature measured within the central viewing area of the unmodified device was 3–5% lower than the setpoint temperature. Using IRTI data, at setpoint temperatures ranging from 900 to 1,300°C, thermal gradients at the edge of the modified window were calculated to be in the range of 0.6 × 106 to 7.0 × 106°C/m. Additionally, the Ag nanocube sublimation approach was used, to measure the local temperature across a FIB-cut Si lamella at high spatial resolution inside the TEM, and demonstrate “proof of concept” of the modified MEMS device. The thermal gradient across the Si lamella, measured using the latter approach was found to be 6.3 × 106°C/m, at a setpoint temperature of 1,000°C. Finally, the applicability of this approach and choice of experimental parameters are critically discussed. 相似文献
18.
Investigations of the micromorphology of rabbit tibial articular cartilage using scanning and transmission electron microscopy revealed that the collagenous elements in the tissue form fluid-containing tubular structures. The commonly described radial or deep zone longitudinal fibres were found to be tubular structures with internal diameters of 1–2 μm. The walls of the tubules were composed of tightly packed fibrils of collagen. The tangential zone, close to the tibial plateau, was composed mainly of a spongy arrangement of collagen fibrils, containing bunches of tangentially lying small (< 1 μm) diameter tubules. The application of conventional chemical fixation techniques resulted in the fine detail of this tissue being obscured. When the tissue was frozen, followed by cryo-scanning electron microscopy or freeze-drying, prior to observation in the scanning electron microscope the tubule structures were not obviously present. It was only by applying freeze-substitution techniques, followed by critical point drying or resin embedding, that the structure was revealed clearly. Segregation of water into ice crystals did occur during the freezing process, but the formation of those crystals played no part in creating the tubular morphology observed. A similar structure was still revealed following pre-treatment with glycerol, methanol or Triton X-100, provided that concentration of these additives was not too high. The walls of the tubules in the radial region were composed of straight, longitudinally arranged as well as helically arranged, 30 nm diameter fibrils. The lumen of the tubules appears to be lined by a circumferentially arranged array of approximately 10 nm diameter fibres, spaced at regular intervals of 50–70 nm. 相似文献
19.
Altendorf H Decencière E Jeulin D De sa Peixoto P Deniset-Besseau A Angelini E Mosser G Schanne-Klein MC 《Journal of microscopy》2012,247(2):161-175
The recent booming of multiphoton imaging of collagen fibrils by means of second harmonic generation microscopy generates the need for the development and automation of quantitative methods for image analysis. Standard approaches sequentially analyse two-dimensional (2D) slices to gain knowledge on the spatial arrangement and dimension of the fibrils, whereas the reconstructed three-dimensional (3D) image yields better information about these characteristics. In this work, a 3D analysis method is proposed for second harmonic generation images of collagen fibrils, based on a recently developed 3D fibre quantification method. This analysis uses operators from mathematical morphology. The fibril structure is scanned with a directional distance transform. Inertia moments of the directional distances yield the main fibre orientation, corresponding to the main inertia axis. The collaboration of directional distances and fibre orientation delivers a geometrical estimate of the fibre radius. The results include local maps as well as global distribution of orientation and radius of the fibrils over the 3D image. They also bring a segmentation of the image into foreground and background, as well as a classification of the foreground pixels into the preferred orientations. This accurate determination of the spatial arrangement of the fibrils within a 3D data set will be most relevant in biomedical applications. It brings the possibility to monitor remodelling of collagen tissues upon a variety of injuries and to guide tissues engineering because biomimetic 3D organizations and density are requested for better integration of implants. 相似文献
20.
Bowen WANG Bingheng LU Lijuan ZHANG Jianxun ZHANG Bobo LI Qianyu JI Peng LUO Qian LIU 《Frontiers of Mechanical Engineering》2023,18(1):11
High-entropy alloys (HEAs) are considered alternatives to traditional structural materials because of their superior mechanical, physical, and chemical properties. However, alloy composition combinations are too numerous to explore. Finding a rapid synthesis method to accelerate the development of HEA bulks is imperative. Existing in situ synthesis methods based on additive manufacturing are insufficient for efficiently controlling the uniformity and accuracy of components. In this work, laser powder bed fusion (L-PBF) is adopted for the in situ synthesis of equiatomic CoCrFeMnNi HEA from elemental powder mixtures. High composition accuracy is achieved in parallel with ensuring internal density. The L-PBF-based process parameters are optimized; and two different methods, namely, a multi-melting process and homogenization heat treatment, are adopted to address the problem of incompletely melted Cr particles in the single-melted samples. X-ray diffraction indicates that HEA microstructure can be obtained from elemental powders via L-PBF. In the triple-melted samples, a strong crystallographic texture can be observed through electron backscatter diffraction, with a maximum polar density of 9.92 and a high ultimate tensile strength (UTS) of (735.3 ± 14.1) MPa. The homogenization heat-treated samples appear more like coarse equiaxed grains, with a UTS of (650.8 ± 16.1) MPa and an elongation of (40.2% ± 1.3%). Cellular substructures are also observed in the triple-melted samples, but not in the homogenization heat-treated samples. The differences in mechanical properties primarily originate from the changes in strengthening mechanism. The even and flat fractographic morphologies of the homogenization heat-treated samples represent a more uniform internal microstructure that is different from the complex morphologies of the triple-melted samples. Relative to the multi-melted samples, the homogenization heat-treated samples exhibit better processability, with a smaller composition deviation, i.e., ≤ 0.32 at.%. The two methods presented in this study are expected to have considerable potential for developing HEAs with high composition accuracy and composition flexibility. 相似文献