共查询到6条相似文献,搜索用时 0 毫秒
1.
E. Meyer H. Heinzelmann P. Grütter Th. Jung Th. Weisskopf H.-R. Hidber R. Lapka H. Rudin H.-J. Güntherodt 《Journal of microscopy》1988,152(1):269-280
The atomic force microscope (AFM) offers the possibility to image the topography of insulating as well as conductive surfaces. Highly oriented pyrolytic graphite (HOPG) was chosen as an example for a layered material and compared to single crystalline lithium fluoride (LiF). Both materials are easily prepared and inert at ambient pressure. Furthermore they are well characterized by Helium atom scattering experiments and other techniques. On HOPG atomic resolution has been achieved. Distortions can be observed which we interpret as a frictional effect. In addition we performed large area scans where we seldomly observed dislocations. For the first time we present measurements on LiF, showing steps of one unit cell height. On larger areas the surface of LiF showed terraces, separated by steps of variable heights, ranging from a few ångströms to 100 Å. We used a static method to get information about the distance dependence of the force between lever and sample. By slowly expanding and retracting the sample piezo and simultaneous measurement of the lever deflection, plots were recorded, showing the force as a function of sample position. The results were compared with theoretical calculations. We could determine the tip radius and found differences between LiF and HOPG being characteristic for the samples. 相似文献
2.
We have employed field-emission secondary electron microscopy (FESEM) for morphological evaluation of freeze-fractured frozen-hydrated renal epithelial LLC-PK1 cells prepared with our simple cryogenic sandwich-fracture method that does not require any high-vacuum freeze-fracture instrumentation (Chandra et al. (1986) J. Microsc. 144 , 15–37). The cells fractured on the substrate side of the sandwich were matched one-to-one with their corresponding complementary fractured faces on the other side of the sandwich. The FESEM analysis of the frozen-hydrated cells revealed three types of fracture: (i) apical membrane fracture that produces groups of cells together on the substrate fractured at the ectoplasmic face of the plasma membrane; (ii) basal membrane fracture that produces basal plasma membrane-halves on the substrate; and (iii) cross-fracture that passes randomly through the cells. The ectoplasmic face (E-face) and protoplasmic face (P-face) of the membrane were recognized based on the density of intramembranous particles. Feasibility of fractured cells was shown for intracellular ion localization with ion microscopy, and fluorescence imaging with laser scanning confocal microscopy. Ion microscopy imaging of freeze-dried cells fractured at the apical membrane revealed well-preserved intracellular ionic composition of even the most diffusible ions (total concentrations of K+, Na+ and Ca+). Structurally damaged cells revealed lower K+ and higher Na+ and Ca+ contents than in well-preserved cells. Frozen-freeze-dried cells also allowed imaging of fluorescently labelled mitochondria with a laser scanning confocal microscope. Since these cells are prepared without washing away the nutrient medium or using any chemical pretreatment to affect their native chemical and structural makeup, the characterization of fracture faces introduces ideal sample types for chemical and morphological studies with ion and electron microscopes and other techniques such as laser scanning confocal microscopy, atomic force microscopy and near-field scanning optical microscopy. 相似文献
3.
Nowadays, the atomic force microscopy plays an indispensable role in imaging and manipulation of biological samples. To observe some specific behaviors and biological processes, fast and accurate imaging techniques are required, and one way to speed up the imaging process is to use short cantilevers. For short beams, the Timoshenko model seems to be more accurate compared to other models such as the Euler–Bernoulli. By using the Timoshenko beam model, the effects of rotational inertia and shear deformation are taken into consideration. In this paper, the frequency response of a rectangular atomic force microscope (AFM) in liquid environment has been analyzed by using the Timoshenko beam model. Afterward, since the dynamic response of AFM is influenced by the applied medium, the effects of physical and mechanical properties (e.g., fluid density and viscosity) on the frequency response of the system have been investigated. The frequency responses of the AFM cantilever immersed in various liquids have been compared with one another. And eventually, to study the influence of geometry on the dynamic behavior of AFM, the effect of the cantilever's geometrical parameters (e.g., cantilever length, width and thickness) on the frequency response of the system has been studied. 相似文献
4.
Hermizi Hapidin Nur Afiqah Amalina Romli Hasmah Abdullah 《Microscopy research and technique》2019,82(11):1928-1940
Tannic acid (TA) is a phenolic compound that might act directly on osteoblast metabolism. The study was performed to investigate the effects of TA on the proliferation, mineralization, and morphology of human fetal osteoblast cells (hFOB 1.19). The cells were divided into TA‐treated, untreated, and pamidronate‐treated (control drug) groups. Half maximal effective concentration (EC50) values for TA and pamidronate were measured using MTT assay. The EC50 of hFOB 1.19 cells treated with TA was 2.94 M. This concentration was more effective compared to the pamidronate (15.27 M). Cell proliferation assay was performed to compare cell viability from Day 1 until Day 14. The morphology of hFOB 1.19 was observed via inverted microscope and scanning electron microscope. Calcium (Ca) and phosphate (P) were assessed using energy‐dispersive X‐ray (EDX) analysis. Furthermore, the mineralization of hFOB 1.19 was determined by von Kossa staining (P depositions) and Alizarin Red S staining (Ca depositions). The number of cells treated with TA was significantly higher than the two control groups at Day 10 and Day 14. The morphology of cells treated with TA was uniformly fusiform‐shaped with filopodia extensions. Besides, globular‐like structures of deposited minerals were observed in the TA‐treated group. In line with other findings, EDX spectrum analysis confirmed the presence of Ca and P. The cells treated with TA had significantly higher percentage of both minerals at Day 3 and Day 10 compared to the two control groups. In conclusion, TA enhances cell proliferation and causes cell morphology changes, as well as improved mineralization. 相似文献
5.
The domain switching properties of the ferroelectric Pb(Zr0.2Ti0.8)O3 (PZT) thin films with two types of crystallographic orientations were investigated by electrostatic force microscopy (EFM). The crystallographic orientations of the PZT thin films were random on the (1 1 1)Pt/MgO(1 0 0) and c-axis preferred on the (1 0 0)Pt/MgO(1 0 0), respectively. When dc bias was applied to the films for writing in micro-scale area, electrostatic force images showed that the domain switching was hard in the PZT thin films with random orientation, while the pattern could clearly be written in the PZT films with c-axis orientation. The differences in the domain switching properties of each PZT thin film were investigated in the crystallographic orientations point of view, and the domain switching dynamics were also measured by investigating the nano-sized dot switching behavior with respect to the width of the applied voltage pulse. 相似文献
6.
Immunofluorescence staining techniques at present, when applied to follow the expression of HIV-1-specific antigens on infected cells, only give the information that the antigens detected are localized in the outer region of the membrane of the infected cell. We therefore set up a procedure using magnetic polystyrol particles coated with antibodies specific for the HIV-1 antigens under study, in combination with scanning electron microscopy. We were able to demonstrate that p24 and p18 structural antigens are clearly expressed on the surface of HIV-1-infected H9 lymphocytes. This means that there was no steric hindrance for structures of cell-like size specific for HIV-1 antigens to interact with their target antigens. Other antigens may be hidden in membrane structures and are therefore inaccessible, for example, to the beads used here, which were of a similar size to antigen-specific cells in vivo. The results of this model system must be seen with respect to the interaction of antigen-specific cell-mediated immunity with full antibody-dependent cellular cytotoxicity, or without cytotoxic T lymphocytes, the mediator function of antibodies. 相似文献