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  • 1
    facet.materialart.
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    Oxford University Press
    Publikationsdatum: 2015-08-09
    Print ISSN: 0022-0744
    Digitale ISSN: 1477-9986
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 2
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    Oxford University Press
    Publikationsdatum: 2015-08-09
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 3
    Publikationsdatum: 2015-08-09
    Beschreibung: Fluorescence microscopy allows us to observe fluorescently labeled molecules in diverse biological processes and organelle structures within living cells. However, the diffraction limit restricts its spatial resolution to about half of its wavelength, limiting the capability of biological observation at the molecular level. Structured-illumination microscopy (SIM), a type of super-resolution microscopy, doubles the spatial resolution in all three dimensions by illuminating the sample with a patterned excitation light, followed by computer reconstruction. SIM uses a relatively low illumination power compared with other methods of super-resolution microscopy and is easily available for multicolor imaging. SIM has great potential for meeting the requirements of live-cell imaging. Recent developments in diverse types of SIM have achieved higher spatial (~50 nm lateral) and temporal (~100 Hz) resolutions. Here, we review recent advancements in SIM and discuss its application in noninvasive live-cell imaging.
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  • 4
    Publikationsdatum: 2015-08-09
    Beschreibung: One of the most popular super-resolution microscopies that breaks the diffraction barrier is stimulated emission depletion (STED) microscopy. As the optical set-up of STED microscopy is based on a laser scanning microscopy (LSM) system, it potentially has several merits of LSM like confocal or two-photon excitation LSM. In this article, we first describe the principles of STED microscopy and then describe the features of our newly developed two-photon excitation STED microscopy. On the basis of our recent results and those of other researchers, we conclude by discussing future research and new technologies in this field.
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  • 5
    Publikationsdatum: 2015-08-09
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  • 6
    Publikationsdatum: 2015-08-09
    Beschreibung: The electrically automated ultrathin sectioning apparatus, which has been developed in recent years, can produce consecutive ultrathin sections with a diamond knife and a gallium ion beam. These newly developed apparatuses, however, have several shortcomings, such as the limited block cutting area, thermal damage to the sample by the focused ion beam and a sample electronic charge. To overcome these faults and for easier scanning electron microscopy three-dimensional fine structural reconstruction, we have developed a new cutting method using a deep ultraviolet laser, which we have named the ‘LANTome (Light Ablation Nanotome)’. Using this method, we confirmed the widening of sectioning areas, shortening of the sectioning time, automatic smoothing of rough surfaces, no sample electronic charge and minimal heat effects on the sample tissue, such as thermal denaturation.
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  • 7
    Publikationsdatum: 2015-08-09
    Beschreibung: Recent advances in nanoscopy, which breaks the diffraction barrier and can visualize structures smaller than the diffraction limit in cells, have encouraged biologists to investigate cellular processes at molecular resolution. Since nanoscopy depends not only on special optics but also on ‘smart’ photophysical properties of photocontrollable fluorescent probes, including photoactivatability, photoswitchability and repeated blinking, it is important for biologists to understand the advantages and disadvantages of fluorescent probes and to choose appropriate ones for their specific requirements. Here, we summarize the characteristics of currently available fluorescent probes based on both proteins and synthetic compounds applicable to nanoscopy and provide a guideline for selecting optimal probes for specific applications.
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  • 8
    Publikationsdatum: 2015-08-09
    Beschreibung: As one of the most powerful tools in the biological investigation of cellular structures and dynamic processes, fluorescence microscopy has undergone extraordinary developments in the past decades. The advent of super-resolution techniques has enabled fluorescence microscopy – or rather nanoscopy – to achieve nanoscale resolution in living specimens and unravelled the interior of cells with unprecedented detail. The methods employed in this expanding field of microscopy, however, are especially prone to the detrimental effects of optical aberrations. In this review, we discuss how super-resolution microscopy techniques based upon single-molecule switching, stimulated emission depletion and structured illumination each suffer from aberrations in different ways that are dependent upon intrinsic technical aspects. We discuss the use of adaptive optics as an effective means to overcome this problem.
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  • 9
    Publikationsdatum: 2015-08-09
    Beschreibung: The acrosome is a Golgi-derived sperm cell organelle enclosed by a continuous acrosomal membrane. The acrosomal membrane complexes with surrounding matrices containing molecules necessary for fertilization; however, the complex of acrosomal membrane and associating matrices (CAMAM) has not been visualized in detail under living conditions. Here, we analyzed the CAMAM at the nanometer level using super-resolution stimulated emission depletion (STED) fluorescence microscopy and equatorin-enhanced green fluorescent protein transgenic mice. The STED images were compared with the corresponding images taken by immunoelectron microscopy. Consequently, the substructure of CAMAM could be differentiated at nanometer-scale resolution by STED microscopy without the need for sectioning. The information obtained in this study will be beneficial not only for understanding the molecular mechanism of fertilization but also for cell imaging under living conditions.
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  • 10
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    Oxford University Press
    Publikationsdatum: 2015-04-03
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 11
    Publikationsdatum: 2015-04-03
    Beschreibung: Ptychographic iterative engine (PIE), a form of coherent diffractive imaging in which the phase of both low-angle and high-angle diffraction data is used to form an image without a lens, can in principle deliver wavelength-limited resolution. Working at low accelerating voltages (30 keV) reduces specimen knock-on damage, increases high-resolution contrast and allows a scanning electron microscope to be used as a transmission electron microscopy. However, electrons are very strongly scattered at low energy. To that end, the effect of dynamical scattering on PIE at low accelerating voltages is calculated to illustrate the possibility of generating high-resolution images with low energy electrons.
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  • 12
    Publikationsdatum: 2016-03-31
    Beschreibung: The application of multispectral imaging to discriminate myelinated and demyelinated areas of neural tissue is herein presented. The method is applied through a custom-made, multispectral imaging monochromator, coupled to a commercially available microscope. In the present work, a series of spinal cord sections were analysed derived from mice with experimental autoimmune encephalomyelitis (EAE), an experimental model widely used to study multiple sclerosis (MS). The multispectral microscope allows imaging of local areas with loss of myelin without the need of tissue labelling. Imaging with the aforementioned method and system is compared in a parallel way with conventional methods (wide-field and confocal fluorescence microscopies). The diagnostic sensitivity of our method is 90.4% relative to the ‘gold standard’ method of immunofluorescence microscopy. The presented method offers a new platform for the possible future development of an in vivo , real-time, non-invasive, rapid imaging diagnostic tool of spinal cord myelin loss-derived pathologies.
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  • 13
    Publikationsdatum: 2016-03-31
    Beschreibung: Advancement of microscopic technologies established significant progress in our understanding of the brain. In the recent effort to elucidate the complete wiring map of the brain circuitry termed ‘connectome’, the different modalities of imaging technology, including those of light and electron microscopy, have started providing essential contribution in multiple organisms. The contribution would be impossible without the recent innovation in both acquisition and analyses of the big connectomic data. The current data demonstrated complicated networks with unidirectional and reciprocal connections of the cerebral circuits at the macroscopic and light microscopic (‘mesoscopic’) levels, and the unimaginable complexity of synaptic connections between axons and dendrites at the electron microscopic (‘microscopic’) level. At the same time, the data highlighted the necessity to make substantial advancement in methodology of the connectomic studies, including efficient handling and automated analyses of the acquired dataset. Further understanding about structural and functional connectome seems to be facilitated by combinations of the different imaging modalities. Such multidisciplinary approaches will give us the clues to address whether the complete connectome can elucidate fundamental mechanisms processing the basic and higher functions of human brains.
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  • 14
    Publikationsdatum: 2016-03-31
    Beschreibung: The occupation sites and the occupancies of trace dopants in La/Co co-doped Sr-M-type ferrite, SrFe 12 O 19 , were quantitatively and precisely determined by beam-rocking energy-dispersive X-ray spectroscopy (EDXS) on the basis of electron-channeling effects. Because the Co atoms, in particular, should be partially substituted for the five crystallographically inequivalent sites, which could be key parameters in improving the magneto-crystalline anisotropy, it is difficult yet intriguing to discover their occupation sites and occupancies without using the methods of large-scale facilities, such as neutron diffraction and synchrotron radiation. In the present study, we tackled this problem by applying an extended statistical atom location by channeling enhanced microanalysis method, using conventional transmission electron microscopy, EDXS and dynamical electron elastic/inelastic scattering theories. The results show that the key occupation sites of Co were the 2a, 4f 1 and 12k sites. The quantified occupancies of Co were consistent with those of the previous study, which involved a combination of neutron diffraction and extended X-ray absorption fine structure analysis, as well as energetics considerations based on by first-principles calculations.
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  • 15
    Publikationsdatum: 2016-03-31
    Beschreibung: Needle-shaped precipitates in an aged Al–0.62Mg–0.93Si (mass%) alloy were identified using a compositional threshold method, an isoconcentration surface, in atom probe tomography (APT). The influence of thresholds on the morphological and compositional characteristics of the precipitates was investigated. Utilizing optimum parameters for the concentration space, a reliable number density of the precipitates is obtained without dependence on the elemental concentration threshold in comparison with evaluation by transmission electron microscopy (TEM). It is suggested that careful selection of the concentration space in APT can lead to a reasonable average Mg/Si ratio for the precipitates. It was found that the maximum length and maximum diameter of the precipitates are affected by the elemental concentration threshold. Adjustment of the concentration threshold gives better agreement with the precipitate dimensions measured by TEM.
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  • 16
    Publikationsdatum: 2016-03-31
    Beschreibung: Acetazolamide (AZA) reduces the water permeability of aquaporin-4, the predominant water channel in the brain. We determined the structure of aquaporin-4 in the presence of AZA using electron crystallography. Most of the features of the 5-Å density map were consistent with those of the previously determined atomic model. The map showed a protruding density from near the extracellular pore entrance, which most likely represents the bound AZA. Molecular docking simulations supported the location of the protrusion as the likely AZA-binding site. These findings suggest that AZA reduces water conduction by obstructing the pathway at the extracellular entrance without inducing a large conformational change in the protein.
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  • 17
    Publikationsdatum: 2016-03-31
    Beschreibung: To understand the bainitic transformation behavior in Cu–17Al–11Mn (at.%) alloys, dynamic in situ observation during heating was carried out in a scanning electron microscope (SEM). In this study, after optimizing the sample preparation method and observation conditions, we successfully observed the transformation process with sufficient resolution and contrast. From the observation results, bainite is first formed preferentially at the grain boundaries of the parent phase. Bainite is also formed inside the grains to relax the elastic strain generated by the initial bainite. Regarding the growth mode, in the early stage of the transformation, bainite grows along the longitudinal direction, and in the late stage, it grows along the lateral direction. The growth rate of the bainite was also evaluated by continuous observation of the same plate. Dynamic in situ observation of a martensitic transformation in the same alloy was also performed to compare the growth mode with that of bainite, and it was found that the behavior is considerably different between bainitic and the martensitic transformations.
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  • 18
    Publikationsdatum: 2016-03-31
    Beschreibung: Although many studies of the Golgi apparatus structure have been performed by light and electron microscopy, the full shape of the Golgi apparatus remained unclear due to the technical limitations of the previously applied microscopy techniques. In this study, we used serial section scanning electron microscopy (SEM) for the morphological study of the Golgi apparatus. This method is useful for three-dimensional (3D) reconstruction of cellular structures without requiring specialized instruments, unlike focused ion beam SEM (FIB-SEM) and serial block face SEM (SBF-SEM). Using the serial section SEM method developed by our laboratory, we investigate the 3D shape of the osmium-impregnated Golgi apparatus in rat epididymal cells, pancreatic acinar cells and gonadotropes. The combination of serial section SEM and a 3D reconstruction technique enabled us to elucidate the entire shape of the Golgi apparatus in these cells. The full shape of the Golgi apparatus in epididymal cells formed a basket-like structure with oval-shaped cisterns, while the Golgi apparatus in an acinar cell from the pancreas was composed of elongated ribbon-like structures that were connected to each other, making a coarse network. The overall image of the Golgi apparatus cisterns from a gonadotrope looked like a spherical cage. This study has clearly shown that entire 3D shape of the Golgi apparatus varies depending on the cell type and that the Golgi cisterns network appears as a single mass located in the large region of the cytoplasm.
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  • 19
    Publikationsdatum: 2016-03-31
    Beschreibung: The initial determination of left–right asymmetry is an essential process in embryonic development. In mouse embryo, cilia in the node play an important role generating the nodal flow that subsequently triggers left–right determination in the embryo. Although nodal cilia have historically been thought to have a 9 + 0 axonemal configuration, the existence of 9 + 2 cilia has been reported so far. Because the distribution of those two types of cilia within the node has not yet been reported, we assessed the arrangement of 9 + 0 and 9 + 2 cilia in the node. In this study, we concluded that most of the nodal cilia were 9 + 0 in structure and there were much fewer 9 + 2 cilia than 9 + 0 cilia. Furthermore, the two types of cilia were randomly distributed in the node with no regularity. In addition, we studied the embryonic origin of the crown cells surrounding the node to better understand their identity.
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  • 20
    Publikationsdatum: 2016-03-31
    Beschreibung: The ultrastructure of melanin granules in human hair was studied using 1,000 kV high-voltage scanning transmission electron microscopy to successfully reconstruct three-dimensional images of the whole melanin granule. It was revealed that the melanin granule was composed of a membrane-like outer structure that included many spherical vesicles, and an inner matrix containing a sheet-like structure in the elongated direction of the melanin granule and a sheet-like arrays structure in the cross direction. The outer structure of the melanin granule was maintained even after exposure to hair-bleaching agents to decompose the melanin granule, suggesting that the outer structure was a highly robust structure and composition compared with the inner matrix .
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  • 21
    Publikationsdatum: 2015-12-13
    Beschreibung: The dependence of the microstructure of Ge 2 Sb 2 Te 5 (GST) on Ti diffusion into GST by annealing in GST/Ti/TiN phase-change random access memory stack was studied by various transmission electron microscopy (TEM) techniques. The microstructure and crystal structure of GST were identified with high-resolution TEM (HRTEM) and image simulation technique, and the Ti diffusion into GST was revealed by scanning transmission electron microscope-energy-dispersive X-ray spectroscopy analysis. It was observed that Ti atoms of Ti/TiN thin layers were incorporated into GST cell through several thermal annealing steps and they could retard the phase transition from face-centered cubic (FCC) phase into hexagonal close-packed (HCP) phase partially and restrain the increase in grain size. Thus, it is concluded that Ti diffusion can affect the microstructure of GST including the type of the crystal phase and grain size of GST. It was shown that the insertion of diffusion barrier between TiN and GST could block Ti diffusion into GST and make it possible for FCC phase to completely transform into HCP phase.
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  • 22
    Publikationsdatum: 2015-12-13
    Beschreibung: In this study, we introduce scanning electron microscopy (SEM) of semithin resin sections. In this technique, semithin sections were adhered on glass slides, stained with both uranyl acetate and lead citrate, and observed with a backscattered electron detector at a low accelerating voltage. As the specimens are stained in the same manner as conventional transmission electron microscopy (TEM), the contrast of SEM images of semithin sections was similar to TEM images of ultrathin sections. Using this technique, wide areas of semithin sections were also observed by SEM, without the obstruction of grids, which was inevitable for traditional TEM. This study also applied semithin section SEM to correlative light and electron microscopy. Correlative immunofluorescence microscopy and immune-SEM were performed in semithin sections of LR white resin-embedded specimens using a FluoroNanogold-labeled secondary antibody. Because LR white resin is hydrophilic and electron stable, this resin is suitable for immunostaining and SEM observation. Using correlative microscopy, the precise localization of the primary antibody was demonstrated by fluorescence microscopy and SEM. This method has great potential for studies examining the precise localization of molecules, including Golgi- and ER-associated proteins, in correlation with LM and SEM.
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  • 23
    Publikationsdatum: 2015-12-13
    Beschreibung: All-solid-state Li-ion batteries (LIBs) with solid electrolytes are expected to be the next generation devices to overcome serious issues facing conventional LIBs with liquid electrolytes. However, the large Li-ion transfer resistance at the electrode/solid-electrolyte interfaces causes low power density and prevents practical use. In-situ -formed negative electrodes prepared by decomposing the solid electrolyte Li 1+ x +3 z Al x (Ti,Ge) 2– x Si 3 z P 3– z O 12 (LASGTP) with an excess Li-ion insertion reaction are effective electrodes providing low Li-ion transfer resistance at the interfaces. Prior to our work, however, it had still been unclear how the negative electrodes were formed in the parent solid electrolytes. Here, we succeeded in dynamically visualizing the formation by in situ spatially resolved electron energy-loss spectroscopy in a transmission electron microscope mode (SR-TEM-EELS). The Li-ions were gradually inserted into the solid electrolyte region around 400 nm from the negative current-collector/solid-electrolyte interface in the charge process. Some of the ions were then extracted in the discharge process, and the rest were diffused such that the distribution was almost flat, resulting in the negative electrodes. The redox reaction of Ti 4+ /Ti 3+ in the solid electrolyte was also observed in situ during the Li insertion/extraction processes. The in situ SR-TEM-EELS revealed the mechanism of the electrochemical reaction in solid-state batteries.
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  • 24
    Publikationsdatum: 2015-12-13
    Beschreibung: We have investigated how accurately atomic-resolution annular dark-field (ADF) images match between experiments and simulations to conduct more reliable crystal structure analyses. Quantitative ADF imaging, in which the ADF intensity at each pixel represents the fraction of the incident probe current, allows us to perform direct comparisons with simulations without the use of fitting parameters. Although the conventional comparison suffers from experimental uncertainties such as an amorphous surface layer and specimen thickness, in this study we eliminated such uncertainties by using a single-layer graphene as a specimen. Furthermore, to reduce image distortion and shot noises in experimental images, multiple acquisitions with drift correction were performed, and the atomic ADF contrast was quantitatively acquired. To reproduce the experimental ADF contrast, we used three distribution functions as the effective source distribution in simulations. The optimum distribution function and its full-width at half-maximum were evaluated by measuring the residuals between the experimental and simulated images. It was found that the experimental images could be explained well by a linear combination of a Gaussian function and a Lorentzian function with a longer tail than the Gaussian function.
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  • 25
    Publikationsdatum: 2015-12-13
    Beschreibung: Mechanical properties of complex steels are affected by their multi-phase structure. Scanning electron microscopy (SEM) is routinely used for characterizing dual-phase (DP) steels, although the identification of steel constituents is not straightforward. In fact, there are several ways of enabling the ferrite–martensite segmentation by SEM, and a wide range of electron energies can be utilized. This study demonstrates the phase identification of DP steels at high, low and extremely low landing energies of the primary electrons from tens of keV to tens of eV. Visualization of the specimen surface at very low landing energies has been achieved by inserting an earthed detector between the pole piece and the negatively biased specimen. This ‘cathode lens mode’ enables the use of the full energy range up to the primary electron energies. It has been found that extremely slow electrons (〈100 eV) are exceptionally suitable for separation of the martensite from the ferrite matrix due to high surface sensitivity, enabling visualization of very fine features. Moreover, the channelling contrast is significantly suppressed at the landing energy of tens of eV of the primary electrons, which enables separation of the phases clearly even in the images acquired at low magnification. The contrast between the phases at tens of eV can be explained by the different thickness of native oxide covering the martensite and the ferrite phase.
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  • 26
    Publikationsdatum: 2015-12-13
    Beschreibung: ‘Tubular aggregates’ are morphologically distinct cytoplasmic structures that have been linked to a variety of pathological conditions. This report documents the presence of tubular aggregates in an insect cell line (C6/36 cells derived from Aedes albopictus ) following inoculation of the cells with material derived from cell culture passaged homogenized Culex australicus mosquitoes. The tubular aggregates were detected in ~2% of treated cells and had three morphological forms that were termed primary, secondary and tertiary, with progressively greater levels of structural complexity. The findings indicate that tubular aggregates can be induced in an insect cell culture system by an unidentified agent present in some mosquitoes.
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  • 27
    Publikationsdatum: 2016-03-31
    Beschreibung: In this article, we propose a smart image-analysis method suitable for extracting target features with hierarchical dimension from original data. The method was applied to three-dimensional volume data of an all-solid lithium-ion battery obtained by the automated sequential sample milling and imaging process using a focused ion beam/scanning electron microscope to investigate the spatial configuration of voids inside the battery. To automatically fully extract the shape and location of the voids, three types of filters were consecutively applied: a median blur filter to extract relatively larger voids, a morphological opening operation filter for small dot-shaped voids and a morphological closing operation filter for small voids with concave contrasts. Three data cubes separately processed by the above-mentioned filters were integrated by a union operation to the final unified volume data, which confirmed the correct extraction of the voids over the entire dimension contained in the original data.
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  • 28
    Publikationsdatum: 2016-03-31
    Beschreibung: Polyelectrolyte brushes are polyelectrolyte polymers with one end fixed to a substrate. In this study, direct nano-scale visualization of polyelectrolyte brushes was carried out under ‘aqueous conditions’ by atmospheric scanning electron microscopy. The thickness of the polyelectrolyte brush layer was measured under both dry and aqueous conditions, experimentally confirming the swollen state of the brushes. These experimental findings qualitatively agreed with the results from previous neutron reflectivity experiments using similar polyelectrolyte brushes. Such direct visualization of polymer brushes in real space opens up a new route for better understanding their surface properties, such as friction, adhesion and wettability.
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  • 29
    Publikationsdatum: 2015-10-10
    Beschreibung: Scanning electron microscopy has been identified as an important approach in studying scale microstructures in fish with reference to taxonomy. In this article, a detailed microstructural analysis of the scales of Channa barca , a poorly known snakehead fish was carried out the location of focus, inter-radial distance, average width and inter-circular space of anterior circulii; inter-circular distance and dentition in lateral circulii; the shape, spacing, length of lepidonts in anterior circulii and the number and width of radii were compared with those of a related species, Channa aurantimaculata . The location of the focus was found to be similar to those of the gachua group of the genus Channa but was different from those of the marulius group. There were major similarities—though with a few notable differences—in scale microstructures between C. barca and the aforementioned closely related species C. aurantimaculata , indicating that scale microstructure analysis has the potential to distinguish even closely related fish species . While several of the microstructural features of the scale were found to be similar to those of the gachua group, others were closer in nature to those of the marulius group. Some microstructural characteristics, however, were found to be totally different from those of both gachua and marulius groups. All of these characteristic features of scale microstructure in C. barca are discussed with reference to taxonomic significance.
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  • 30
    facet.materialart.
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    Oxford University Press
    Publikationsdatum: 2015-10-10
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  • 31
    Publikationsdatum: 2015-10-10
    Beschreibung: Flow cytometry and microscopy are equally important in cell analysis. However, few reports have compared the optical data (cell size, internal complexity and fluorescent signal) from flow cytometry and microscopy. In this study, we compared the scattergram from XN-series, a flow cytometry based hematology analyzer with microscopic images of similarly treated leukocytes, and investigated the correlation between the appearance in the scattergram and cell size, internal complexity and fluorescence intensity. Healthy human peripheral blood was analyzed using the XN analyzer. For microscopic comparison, five types of leukocytes (monocytes, lymphocytes, basophils, neutrophils and eosinophils) were isolated from the peripheral blood by centrifugation and magnetic cell sorting, treated with a specific reagent and analyzed using electron microscopy, laser microscopy and confocal laser microscopy. Cell size, residual internal structures and fluorescence intensity correlated with intensity of forward-scattering, side scattering and fluorescent light. In this study, optical data from a clinically used hematology analyzer was clarified using microscopic images.
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  • 32
    Publikationsdatum: 2015-10-10
    Beschreibung: For optimizing the microstructure of complex phase (CP) steels, characterization using scanning electron microscopy (SEM) is powerful because it allows observations from very low to high magnification. SEM specimens of steels are often etched in order to distinguish between the different phases by producing topographic information. This is however an ‘indirect’ method of characterization, which does not give precise structural information. We have developed a new technique for the selective imaging of the martensite (M) phase in a ferritic (F)–M complex phase steel. Backscattered electron (BSE) images at 15–20 kV were recorded by systematically changing the collection angle , where is measured from the specimen surface. When was 30–45°, strong channeling contrast was observed. For lower values of , it is the low energy loss electrons that mainly contribute to the contrast. As increases, the M phase exhibits brighter contrast. When exceeds 60°, a selective imaging of the M phase is achieved. This is not because martensite has a larger mean atomic number than ferrite, but is due to the fact that martensite has a high crystallographic defect density. Anomalously bright M contrast is due to multiple scattering of BSE due to the high density of planar defects and dislocations. Low angle BSE allows high resolution characterization of complex microstructures, while high angle BSE gives quantitative assessment of the distribution and the volume fraction of the martensite phase.
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  • 33
    Publikationsdatum: 2015-10-10
    Beschreibung: The contrasts in backscattered electron (BSE) images, such as topographic, channeling and mean atomic number (Z) contrasts, were investigated quantitatively from the cross section of a heat-treated steel sheet using a scanning electron microscope (SEM). High primary electron energy ( E P ) enhances Z contrast, whereas low E P improves channeling contrast. A high take-off angle ( ; measured from the specimen surface) also enhances Z contrast, whereas low improves channeling contrast. When becomes very low, topographic information is enhanced and superimposed on channeling contrast due to the tilt effect of BSE. The relationship of the behaviors of the Z contrast and the channeling contrast can be understood by the detection ratio of low-loss electrons (LLEs) to the inelastic BSE components emitted from the sample surface; LLEs contribute to channeling contrast, and their ratio increases with decreasing E P and . The systematic results obtained in this study are useful for controlling SEM conditions in order to enhance the target information in BSE images for practical materials of interest.
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  • 34
    Publikationsdatum: 2015-10-10
    Beschreibung: It is crucial to determine the position of lattice atoms in a monolayer specimen with high precision using high-resolution transmission electron microscopy (HRTEM). Image simulations indicate that the intensity centers of periodic lattice atoms in graphene may deviate from their intrinsic positions if non-rotationally symmetric aberrations (except for three-fold and six-fold aberrations) exist in the HRTEM imaging system. In this letter, we quantitatively compared the deviations caused by non-rotationally symmetric aberrations, which are equivalent to individually produce a /4 phase shift in the wave aberration function at a given frequency of 7.2 nm –1 . A two-fold aberration caused a maximum shift of 0.3 Å, and in the images affected by the axial coma, graphene still maintained its hexagonal structure while all of the measured atomic positions deviated. Furthermore, we discovered that atoms on each sublattice tended to shift by similar distances in the image. Based on this rule, we retrieved the intrinsic bond length between neighboring carbon atoms by ‘shifting’ the measured atom positions in an experimental HRTEM image affected by residual aberrations.
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  • 35
    Publikationsdatum: 2015-10-10
    Beschreibung: The dislocation shielding field at a crack tip was experimentally proven at the atomic scale by measuring the local strain in front of the crack tip using high-resolution transmission electron microscopy (HRTEM) and geometric phase analysis (GPA). Single crystalline (110) silicon wafers were employed. Cracks were introduced using a Vickers indenter at room temperature. The crack tip region was observed using HRTEM followed by strain measurements using GPA. The measured strain field at the crack tip was compressive owing to dislocation shielding, which is in good agreement with the strain field calculated from elastic theory.
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  • 36
    Publikationsdatum: 2015-10-10
    Beschreibung: The structure of a highly ordered Al 58 Cu 26 Ir 16 decagonal quasicrystal (d-QC), which is constructed by a periodic stack of quasiperiodic atomic planes, was investigated using aberration-corrected scanning transmission electron microscopy. The entire quasiperiodic structure can be well described based on the pentagonal Penrose lattice decorated with a decagonal columnar cluster 2 nm across, and the individual clusters apparently showed up with localized atomic disorder to various degree that blurs the underlying cluster symmetry. Multivariate analysis of the cluster images with principal component analysis has successfully extracted two fundamental clusters, which are with definite mirror and 10-fold-rotation symmetries; this is the first solid example of the d-QC composed of multiple fundamental clusters with different symmetry. Consequently, it is found that all the observed variations can be reasonably interpreted by a linear combination between these two fundamental clusters of mirror and 10-fold symmetries, indicating that the possible atomic disorder is strongly restricted by these particular symmetries. Characteristic distributions of the mirror/10-fold clusters on the pentagonal Penrose lattice are also described.
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  • 37
    Publikationsdatum: 2015-10-10
    Beschreibung: To clarify the contribution of Ca to the gravitropic response, quantitative X-ray microanalyses were performed on cryosections of roots of soybean seedlings reoriented horizontally from their original vertical orientation. After reorientation, the roots bent gradually toward the ground at the elongation zone. The concentrations of Ca in the cell walls, cytoplasmic matrices and central vacuoles of cortical cells were measured in the upper and lower halves of the elongation zone at 0, 30, 60 and 120 min after reorientation. The Ca concentration did not significantly change in the cytoplasmic matrices or vacuoles. Additionally, the Ca concentration did not change significantly in cell walls at 30 min after reorientation; however, beyond 30 min, this concentration significantly increased gradually in the lower half of the elongation zone and decreased in the upper half of the elongation zone, indicating a typical asymmetrical distribution of Ca. These results suggest that Ca moves apoplastically in soybean roots to produce an asymmetrical Ca distribution in the elongation zone, which contributes to root curvature. The possible role of Ca in accelerating or repressing the effect of auxin is also discussed in this study.
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  • 38
    Publikationsdatum: 2015-10-10
    Beschreibung: Uranyl salts are toxic and radioactive; therefore, several studies have been conducted to screen for substitutes of electron stains. In this regard, the contrast evaluation process is time consuming and the results obtained are inconsistent. In this study, we developed a novel contrast evaluation method using affinity beads and a backscattered electron image (BSEI), obtained using scanning electron microscopy. The contrast ratios of BSEI in each electron stain treatment were correlated with those of transmission electron microscopic images. The affinity beads bound to cell components independently. Protein and DNA samples were enhanced by image contrast treated with electron stains; however, this was not observed for sugars. Protein-conjugated beads showed an additive effect of image contrast when double-stained with lead. However, additive effect of double staining was not observed in DNA-conjugated beads. The varying chemical properties of oligopeptides showed differences in image contrast when treated with each electron stain. This BSEI-based evaluation method not only enables screening for alternate electron stains, but also helps analyze the underlying mechanisms of electron staining of cellular structures.
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  • 39
    Publikationsdatum: 2015-10-10
    Beschreibung: We have developed a newly designed straining specimen holder for in situ transmission electron microscopy (TEM) compatible with high-angle single tilt-axis electron tomography. The holder can deform a TEM specimen under tensile stress with the strain rate between 1.5 x 10 –6 and 5.2 x 10 –3 s –1 . We have also confirmed that the maximum tilt angle of the specimen holder reaches ±60° with a rectangular shape aluminum specimen. The new specimen holder, termed as ‘straining and tomography holder’, will have wide range potential applications in materials science.
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  • 40
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2015-10-10
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  • 41
    facet.materialart.
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    Oxford University Press
    Publikationsdatum: 2015-12-18
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  • 42
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2015-12-18
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  • 43
    Publikationsdatum: 2016-05-29
    Beschreibung: The impact of mechanical stress on the morphology of crystallographic and magnetic domains in shape-controlled specimens of an orbital-spin-coupled system, MnV 2 O 4 , was examined by cryogenic Lorentz microscopy. Because of the difference in thermal expansion coefficients of MnV 2 O 4 and the supporting Mo mesh, compression on the order of 0.01% was applied to the thin-foil specimens near the structural/magnetic phase transformation temperatures. The extent of compression was comparable to the lattice striction associated with the cubic-to-tetragonal phase transformation in MnV 2 O 4 . The applied strain thus clearly influenced the morphology of crystallographic domains (i.e. twinning configuration in the tetragonal phase) produced during cooling. The magnetic domain structure was entirely dependent on the configuration of twinning in the tetragonal phase. The observations in this study provided useful information for understanding the relationship between the crystallographic domains and the magnetic domains in MnV 2 O 4 .
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  • 44
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2016-05-29
    Beschreibung: Most cellular organelles contain lipid bilayer membranes. The earliest characterization of cellular organelles was performed by electron microscopy observation of such membranes. However, the precise mechanisms for shaping the membrane in particular subcellular organelles is poorly understood. Classically, the overall cellular shape, i.e. the shape of the plasma membrane, was thought to be governed by the reorganization of cytoskeletal components such as actin and microtubules. The plasma membrane contains various submicron structures such as clathrin-coated pits, caveolae, filopodia and lamellipodia. These subcellular structures are either invaginations or protrusions and are associated with the cytoskeleton. Therefore, it could be hypothesized that there are membrane-binding proteins that cooperates with cytoskeleton in shaping of plasma membrane organelles. Proteins with the Bin–Amphiphysin–Rvs (BAR) domain connect a variety of membrane shapes to actin filaments. The BAR domains themselves bend the membranes by their rigidity and then mold the membranes into tubules through their assembly as spiral polymers, which are thought to be involved in the various submicron structures. Membrane tubulation by polymeric assembly of the BAR domains is supposed to be regulated by binding proteins, binding lipids and the mechanical properties of the membrane. This review gives an overview of BAR protein assembly, describes the significance of the assembly and discusses how to study the assembly in the context of membrane and cellular morphology. The technical problems encountered in microscopic observation of BAR domain assembly are also discussed.
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  • 45
    Publikationsdatum: 2016-05-29
    Beschreibung: In this study, new microscopy techniques were developed for understanding the mechanism for the bainitic transformation in a Cu–17Al–11Mn (at%) alloy. An orthogonally arranged focused ion beam and a scanning electron microscope were employed to observe three-dimensional (3D) morphology of the bainite phase, in addition to compositional analysis by using a scanning transmission electron microscope equipped with a double-detector energy-dispersive X-ray spectrometer system. The 3D morphology of these samples was observed at different aging times and aging temperatures; the results obtained indicated that with increasing aging time and/or aging temperature, the bainite phase at the initial stage of formation exhibits a plate-like shape, which changes to a lenticular form. A habit plane was uniquely determined as ~{9 3 2} by the combination of 3D image reconstruction and an electron back-scattered diffraction technique. The compositional analysis revealed the spatial distribution of the compositional variation between the bainite and matrix phases in the initial stages of the transformation. In the bainite phase, the Cu concentration was higher, while the concentrations of Al and Mn were lower than those in the surrounding matrix, indicative of the diffusion of the constituent elements with the growth of the bainite phase.
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  • 46
    Publikationsdatum: 2016-05-29
    Beschreibung: Cofilin is an actin-binding protein that severs actin filaments. It plays a key role in regulating actin cytoskeletal remodeling, thereby contributing to diverse cellular functions. However, the involvement of cofilin in phagocytosis remains to be elucidated. We examined the spatiotemporal localization of cofilin during phagocytosis of IgG-opsonized erythrocytes, IgG-opsonized latex beads and non-opsonized latex beads. Live-cell imaging showed that GFP-cofilin accumulates in the sites of IgG-opsonized particle binding and in phagocytic cups. Moreover, immunofluorescence microscopy revealed that endogenous cofilin localizes to phagocytic cups engulfing IgG-opsonized particles, but not non-opsonized latex beads. Scanning electron microscopy demonstrated a notable difference in morphology between phagocytic structures in IgG-dependent and IgG-independent phagocytosis. In phagocytosis of IgG-opsonized particles, sheet-like pseudopodia extended along the surface of IgG-opsonized particles to form phagocytic cups. In contrast, in opsonin-independent phagocytosis, long finger-like filopodia captured non-opsonized latex beads. Importantly, non-opsonized beads sank into the cells without extending phagocytic cups. Our analysis of cofilin mutant expression demonstrates that phagocytosis of IgG-opsonized particles is enhanced in cells expressing wild-type cofilin or active mutant cofilin-S3A, whereas the uptake of non-opsonized latex beads is not. These data suggest that cofilin promotes actin cytoskeletal remodeling to form phagocytic cups by accelerating actin turnover and thereby facilitating phagosome formation. In contrast, cofilin is not involved in opsonin-independent phagocytosis of latex beads.
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  • 47
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2016-05-29
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  • 48
    Publikationsdatum: 2016-05-29
    Beschreibung: Cation mixing in positive electrode materials for rechargeable lithium ion batteries, LiNi x Mn 2– x O 4 ( x = 0, 0.2, 0.5) and Li 0.21 Ni 0.7 Mn 1.64 O 4– (denoted as x = 0.7), is analyzed by high-angular-resolution electron-channeling X-ray/electron spectroscopy (HARECXS/HARECES) techniques, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. Mixing between the tetrahedral lithium sites and the octahedral transition metal sites is quantified, and the site-dependent valence states of the transition metals are examined. In the non-doped ( x = 0) sample, Mn was found to occupy only octahedral sites as either Mn 3+ or Mn 4+ . For x = 0.2–0.7, some of the nickel ions (6–13% depending on x ) occupy tetrahedral anti-sites. All the nickel ions are in the divalent state, regardless of the occupation site. For x = 0.2 and 0.7, manganese ions occupy both octahedral and tetrahedral sites; those in the octahedral sites are tetravalent, while the tetrahedral sites contain a mixture of divalent and trivalent ions. For x = 0.5, manganese occupies only the octahedral sites, with all ions determined to be in the tetravalent state (within experimental accuracy). All the samples substantially satisfied the local charge neutrality conditions. This study demonstrates the feasibility of using HARECXS/HARECES for quantitative analysis of the atomic configuration and valence states in lithium manganese oxide spinel materials.
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  • 49
    Publikationsdatum: 2016-05-29
    Beschreibung: Papanicolaou (Pap)-stained slides are usually observed using a transmitted light microscope for cytopathology. However, progress in pathological examinations has created a need for new diagnostic tools, because cytopathological preparations do not allow additional examinations without a loss of specimen, unlike histopathology. Low-vacuum scanning electron microscopy (LVSEM) can reveal the surface topography at an ultrastructual resolution without metal coating. The aim of this study was to determine the conditions required for observing Pap-stained slides of oral smears using LVSEM without any loss of specimen and to reexamine the same slides again using light microscopy, while preserving the cytopathological information.
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  • 50
    Publikationsdatum: 2016-05-29
    Beschreibung: The pennate diatom, Bacillaria paxillifer , forms a colony in which adjacent cells glide smoothly and almost continuously, yet no obvious apparatus driving the movement, such as flagella or cilia, is observed. Thus far, neither the mechanism nor physiological significance of this movement has been well understood. Here, we report quantitative analysis of the gliding motion of B. paxillifer and morphological analysis of this diatom with light and electron microscopes. The gliding of pairs of adjacent B. paxillifer cells in a colony was cyclic with rather constant periods while the average gliding period varied from a few seconds to multiples of 10 s among colonies. The gliding was compromised reversibly by inhibitors for actin and myosin, suggesting involvement of the actomyosin system. Indeed, we observed two closely apposed actin bundles near the raphe by fluorescence-labeled phalloidin staining. Using electron microscopy, we observed filamentous structures that resemble the actin bundles seen with fluorescence microscopy, and we also found novel electron-dense structures located between the plasma membrane and these actin-like filaments. From these and other observations, we suggest that B. paxillifer also uses actin bundles and propose a putative myosin as a molecular motor in the gliding of unicellular diatoms.
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  • 51
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2016-05-29
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  • 52
    Publikationsdatum: 2016-05-29
    Beschreibung: Mitochondrial cytochrome c oxidase utilizes electrons provided by c ytochrome c for the active vectorial transport of protons across the inner mitochondrial membrane through the reduction of molecular oxygen to water. Direct structural evidence on the transient cytochrome c oxidase–cytochrome c complex thus far, however, remains elusive and its physiological relevant oligomeric form is unclear. Here, we report on the 2D crystallization of monomeric bovine cytochrome c oxidase with tightly bound cytochrome c at a molar ratio of 1:1 in reconstituted lipid membranes at the basic pH of 8.5 and low ionic strength.
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  • 53
    Publikationsdatum: 2016-09-03
    Beschreibung: Actin filaments, the actin–myosin complex and the actin–tropomyosin complex were observed by a tip-scan atomic force microscope (AFM), which was recently developed by Olympus as the AFM part of a correlative microscope. This newly developed AFM uses cantilevers of similar size as stage-scan AFMs to improve substantially the spatial and temporal resolution. Such an approach has previously never been possible by a tip-scan system, in which a cantilever moves in the x , y and z directions. We evaluated the performance of this developed tip-scan AFM by observing the molecular structure of actin filaments and the actin–tropomyosin complex. In the image of the actin filament, the molecular interval of the actin subunits (~5.5 nm) was clearly observed as stripes. From the shape of the stripes, the polarity of the actin filament was directly determined and the results were consistent with the polarity determined by myosin binding. In the image of the actin–tropomyosin complex, each tropomyosin molecule (~2 nm in diameter) on the actin filament was directly observed without averaging images of different molecules. Each tropomyosin molecule on the actin filament has never been directly observed by AFM or electron microscopy. Thus, our developed tip-scan AFM offers significant potential in observing purified proteins and cellular structures at nanometer resolution. Current results represent an important step in the development of a new correlative microscope to observe nm-order structures at an acceptable frame rate (~10 s/frame) by AFM at the position indicated by the fluorescent dye observed under a light microscope.
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  • 54
    Publikationsdatum: 2016-09-03
    Beschreibung: A hybrid approach is presented for obtaining electric potentials for use in electron optics modeling. An initial solution from the boundary element method (BEM) is used to derive the bounding potential of a cylindrical subdomain subsequently used in a Fourier series solution. The approach combines the inherent precision of this analytic solution with the flexibility of BEM to describe practical, non-idealized systems of electrodes. The resulting lens field in the Fourier series subdomain is of higher precision, thereby allowing smaller errors in subsequent calculations of electron ray paths. The effects of aberrations are thus easier to observe in tracing non-paraxial rays. Example ray-traces through a simple, known einzel lens are given as validation of this approach.
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  • 55
    Publikationsdatum: 2016-09-03
    Beschreibung: -Agatoxin IV A, a peptidyl toxin from Agelenopsis aperta venom, selectively binds to voltage-gated P/Q-type calcium channels. -Agatoxin IV A has been used as a selective tool in pharmacological and electrophysiological studies. Visualization of P/Q-type calcium channels has previously been accomplished using biotin-conjugated -Agatoxin IV A in freshly prepared mouse cerebellar and hippocampal slices (Nakanishi et al ., J. Neurosci. Res. , 41 , 532, 1995). Here biotinylated -agatoxin IV A was applied to transcardially fixed brain slices prepared with various fixatives. -Agatoxin IV A did not bind to fixed tissues from P/Q-type calcium channel knockout mice, confirming that binding to normal, fixed tissues was not an artifact. Using transmission electron microscopy, locations of biotinylated -agatoxin IV A binding sites visualized with gold-conjugated streptavidin showed a similar pattern to those visualized with antibody. The ability of biotinylated -agatoxin IV A to bind to fixed tissue provides a new cytochemical technique to study molecular architecture of synapses.
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  • 56
    Publikationsdatum: 2016-09-03
    Beschreibung: The analysis of secreted antibody from large and diverse populations of B cells in parallel at the clonal level can reveal desirable antibodies for diagnostic or therapeutic applications. By immobilizing B cells in microdroplets with particulate reporters, decoding and isolating them in a microscopy environment, we have recovered panels of antibodies with rare attributes to therapeutically relevant targets. The ability to screen up to 100 million cells in a single experiment can be fully leveraged by accessing primary B-cell populations from evolutionarily divergent species such as chickens.
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  • 57
    Publikationsdatum: 2016-09-03
    Beschreibung: A new in situ environmental transmission electron microscope (ETEM) was developed based on a 300 kV TEM with a cold field emission gun (CFEG). Particular caution was taken in the ETEM design to assure uncompromised imaging and analytical performance of the TEM. Because of the improved pumping system between the gun and column, the vacuum of CFEG was largely improved and the probe current was sufficiently stabilized to operate without tip flashing for 2–3 h or longer. A high brightness of 2.5 x 10 9 A/cm 2 sr was measured at 300 kV, verifying the high quality of the CFEG electron beam. A specially designed gas injection-heating holder was used in the in situ TEM study at elevated temperatures with or without gas around the TEM specimen. Using this holder in a 10 Pa gas atmosphere and specimen temperatures up to 1000°C, high-resolution ETEM performance and analysis were achieved.
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  • 58
    Publikationsdatum: 2016-09-03
    Beschreibung: Information transfer of a 1-MV field-emission transmission electron microscope (TEM) was improved by reducing mechanical vibrations and improving the stability of an acceleration voltage. The resulting mechanical stability was estimated from lattice fringes with an obtained spacing of 19.6 pm under achromatic conditions. This value corresponds to a vibration amplitude of 〈19.6 pm. The stability of the acceleration voltage was improved by reducing thermal noises in the power supply. As a result, 39.2-pm-spacing linear lattice fringes were obtained under chromatic conditions. This indicates that 25.5 nm –1 information transfer was accomplished in the 1 MV field-emission TEM.
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  • 59
    Publikationsdatum: 2016-09-03
    Beschreibung: Liposomes present a challenge for atomic force microscopy (AFM) observation in aqueous medium because they easily collapse. Here, we demonstrate that bovine serum albumin coating of a glass substrate enables AFM observation of various liposomes in aqueous medium. With this AFM system, liposomes can be systematically observed and morphologically analyzed regardless of their surface charge, phase state, degree of lipid acyl chain unsaturation or PEG modification. This system thus has the potential to reveal the mechanical properties of liposomes of various lipid types and contents.
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  • 60
    Publikationsdatum: 2016-09-03
    Beschreibung: The advent of super-resolution microscopy brought a huge impact to various research fields ranging from the fundamental science to medical and industrial applications. The technological development is still ongoing with involving different scientific disciplines and often changing the standard of optical imaging. In this review, I would like to introduce the recent research progress in super-resolution microscopy as a follow-up for the featured issue in Microscopy (Vol. 64, No. 4, 2015) with discussions especially on the current trends and new directions in the technological development.
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  • 61
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    Oxford University Press
    Publikationsdatum: 2015-05-22
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  • 62
    Publikationsdatum: 2015-05-22
    Beschreibung: We successfully visualized the antibacterial behavior of biodegradable polymeric nanoparticles (NPs) on a biofilm formed by Staphylococcus epidermidis using field emission scanning electron microscopy (FE-SEM). A hydrophilic ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 ]), was applied for observation using FE-SEM. The differences in adherence and penetration behavior of three types of NPs were revealed using this method and confocal laser scanning microscopy. Biodegradable poly( dl -lactide- co -glycolide) (PLGA) NPs were prepared by the emulsion solvent diffusion method. In this study, we treated the biofilm with three PLGA NPs: unmodified PLGA, PLGA modified with chitosan (CS) and clarithromycin (CAM)-loaded + CS-modified PLGA. The viability of S. epidermidis cells treated with PLGA NPs was estimated using the LIVE/DEAD BacLight kit to understand the antibacterial ability of each NP sample in a quantitative way. The results confirmed that CAM-loaded + CS-modified PLGA had high antibacterial ability on the biofilm. This novel observation technique would be useful in the development of drug formations and medical agents.
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  • 63
    Publikationsdatum: 2015-05-22
    Beschreibung: We have performed immunohistochemical or ultrastructural analyses of living mouse small intestines using Epon blocks prepared by ‘ in vivo cryotechnique’ (IVCT). By electron microscopy, intracellular ultrastructures of epithelial cells were well preserved in tissue areas 5–10 μm away from cryogen-contact surface tissues. Their microvilli contained dynamically waving actin filaments, and highly electron-dense organelles, such as mitochondria, were seen under the widely organized terminal web. By quick-freezing of fresh resected tissues (FT-QF), many erythrocytes were congested within blood vessels due to loss of blood pressure. By immersion-fixation (IM-DH) and perfusion-fixation (PF-DH), small vacuoles were often seen in the cytoplasm of epithelial cells, and their intercellular spaces were also dilated. Moreover, actin filament bundles were irregular in cross sections of microvilli, compared with those with IVCT. Epon-embedded thick sections were treated with sodium ethoxide, followed by antigen retrieval and immunostained for immunoglobulin A (IgA), Ig kappa light chain (Ig), J-chain and albumin. By cryotechniques, IgA immunoreactivity was detected as tiny dot-like patterns in cytoplasm of some epithelial cells. Both J-chain and Ig immunoreactivities were detected in the same local areas as those of IgA. By FT-QF, however, the IgA immunoreactivity was more weakly detected, compared with that with IVCT. In thick sections prepared by IM-DH and PF-DH, it was rarely observed in both plasma and epithelial cells. Another albumin was diffusely immunolocalized in extracellular matrices of mucous membranes and also within blood vessels. Thus, IVCT was useful for preservation of soluble proteins and ultrastructural analyses of dynamically changing epithelial cells of living mouse small intestines.
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  • 64
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    Oxford University Press
    Publikationsdatum: 2015-05-22
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  • 65
    Publikationsdatum: 2015-05-22
    Beschreibung: Flow-diverting (FD) stents represent a new concept in the treatment of intracranial aneurysms with challenging anatomical dispositions. Having been introduced to clinical practice only in the last 5 years and featuring complex mechanisms of action, they are still under research. Scanning electron microscopy, as part of an animal research protocol, provides detailed surface observations of neointimal healing at the aneurysm's neck, as well as covered side branch ostia, allowing for the confirmation of scientific hypotheses and observations. Technical adaptations of preparation protocols are presented based on a pilot study on Large White pigs, stented with FD stents at carotid bifurcations.
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  • 66
    Publikationsdatum: 2015-05-22
    Beschreibung: By exploiting characteristics such as negligible vapour pressure and ion-conductive nature of an ionic liquid (IL), we established an in situ scanning electron microscope (SEM) method to observe the electrode reaction in the IL-based Li-ion secondary battery (LIB). When 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C 2 mim][FSA]) with lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) was used as the electrolyte, the Si negative electrode exhibited a clear morphology change during the charge process, without any solid electrolyte interphase (SEI) layer formation, while in the discharge process, the appearance was slightly changed, suggesting that a morphology change is irreversible in the charge–discharge process. On the other hand, the use of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C 2 mim][TFSA]) with Li[TFSA] did not induce a change in the Si negative electrode. It is interesting to note this distinct contrast, which could be attributed to SEI layer formation from the electrochemical breakdown of [C 2 mim] + at the Si negative electrode|separator interface in the [C 2 mim][TFSA]-based LIB. This in situ SEM observation technique could reveal the effect of the IL species electron-microscopically on the Si negative electrode reaction.
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  • 67
    Publikationsdatum: 2015-05-22
    Beschreibung: In this article, we report the development of a new 200-kV analytical electron microscope equipped with a monochromator with an integrated double Wien-filter system. It enables us to study the electronic structures of materials in detail using electron energy-loss spectroscopy (EELS) analysis at an atomic scale. A highly monochromated and isotropically round electron probe is produced on the specimen plane. The ultimate energy resolutions with 0.1-s acquisition times are measured to be 36 meV at 200 kV and 30 meV at 60 kV. In an EELS mapping experiment performed on SrTiO 3 with a monochromated electron probe whose energy resolution is 146 meV, an elemental map exhibits atomic resolution.
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  • 68
    Publikationsdatum: 2015-05-22
    Beschreibung: Si–Si atomic columns separated by 45 pm were successfully resolved with a 300-kV aberration-corrected scanning transmission electron microscope (STEM) equipped with a cold-field emission gun. Using a sufficiently small Gaussian effective source size and a 0.4-eV energy spread at 300 kV, the focused electron probe on the specimen was simulated to be sub-50 pm. Image simulation showed that the present probe condition was sufficient to resolve 45 pm Si–Si dumbbells. A silicon crystalline specimen was observed from the [114] direction with a high-angle annular dark field STEM and the intensity profile showed 45 pm separation. A spot corresponding to (45 pm) –1 was confirmed in the power spectrum of the Fourier transform.
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  • 69
    Publikationsdatum: 2015-05-22
    Beschreibung: We propose a one-step nanopatterning method where liquid monomers are polymerized directly with an electron beam under an atmospheric pressure. The method allows precise positional control of an electron beam that induces electropolymerization based on an anodic oxidation only in the irradiated areas. Various versatile conjugated polymers, including polypyrrole, polyaniline and poly(3-hexylthiophene), have been directly polymerized from monomers without solvents and patterned by our one-step nanopatterning method. Vertically oriented arrays of nanorods several hundred nanometers in diameter with an aspect ratio (height to diameter) of around two were fabricated.
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  • 70
    Publikationsdatum: 2015-05-22
    Beschreibung: This report introduces the first results obtained using phase-contrast scanning transmission electron microscopy (P-STEM). A carbon-film phase plate (PP) with a small center hole is placed in the condenser aperture plane so that a phase shift is introduced in the incident electron waves except those passing through the center hole. A cosine-type phase-contrast transfer function emerges when the phase-shifted scattered waves interfere with the non-phase-shifted unscattered waves, which passed through the center hole before incidence onto the specimen. The phase contrast resulting in P-STEM is optically identical to that in phase-contrast transmission electron microscopy that is used to provide high contrast for weak phase objects. Therefore, the use of PPs can enhance the phase contrast of the STEM images of specimens in principle. The phase shift resulting from the PP, whose thickness corresponds to a phase shift of , has been confirmed using interference fringes displayed in the Ronchigram of a silicon single crystal specimen. The interference fringes were found to abruptly shift at the edge of the PP hole by .
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  • 71
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    Oxford University Press
    Publikationsdatum: 2015-02-05
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  • 72
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    Oxford University Press
    Publikationsdatum: 2015-02-05
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  • 73
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    Oxford University Press
    Publikationsdatum: 2015-02-05
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  • 74
    Publikationsdatum: 2015-02-05
    Beschreibung: Two-photon excitation fluorescence microscopy has become widely used in various life science fields in this decade. In the field of neuroscience in particular, in vivo two-photon microscopy has provided vital information on neural activity and brain function. In the current era of connectomics, visualization of the morphology and activity of numerous neurons in ever larger regions of the living brain are required within short periods. Based on this viewpoint, we discuss the fundamentals, advantages and potential of two-photon excitation fluorescence microscopy for the investigation of neural circuit functions.
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  • 75
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    Oxford University Press
    Publikationsdatum: 2015-02-05
    Beschreibung: Recent powerful tools for reconstructing connectomes using electron microscopy (EM) have made outstanding contributions to the field of neuroscience. As a prime example, the detection of visual motion is a classic problem of neural computation, yet our understanding of the exact mechanism has been frustrated by our incomplete knowledge of the relevant neurons and synapses. Recent connectomic studies have successfully identified the concrete neuronal circuit in the fly's visual system that computes the motion signals. This identification was greatly aided by the comprehensiveness of the EM reconstruction. Compared with light microscopy, which gives estimated connections from arbor overlap, EM gives unequivocal connections with precise synaptic counts. This paper reviews the recent study of connectomics in a brain of the fruit fly Drosophila and highlights how connectomes can provide a foundation for understanding the mechanism of neuronal functions by identifying the underlying neural circuits.
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  • 76
    Publikationsdatum: 2015-02-05
    Beschreibung: Charting and understanding the full wiring diagram of complex neuronal structures such as the central nervous system or the brain (Connectomics) is one of the big remaining challenges in life sciences. Although at first it appears nearly impossible to map out a full diagram of, e.g., a mouse brain with sufficient resolution to identify each and every connection between neurons, recent technological advances move such an ambitious undertaking into the realms of possibility without spending decades at a microscope. However there are still many challenges to address in order to pave the way for fast and systematic neurobiological understanding of whole networks. These challenges range from a more robust and reproducible sample preparation to automated image data acquisition, more efficient data storage strategies and powerful data analysis tools. Here we will review novel imaging techniques developed for the challenge of mapping out the full connectome of a nervous system, brain or eye to name just a few examples. The imaging techniques reviewed cover light sheet illumination methods, single and multi-beam scanning electron microscopy, and we will briefly mention the possible combination of both light and electron microscopy. In particular we will review ‘clearing’ and in vivo methods that can be performed with light sheet fluroescence microscopes such as the ZEISS Lightsheet Z.1. We will then focus on scanning electron microscopy with single and multi-beam instruments including methods such as serial blockface imaging and array tomography methods.
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  • 77
    Publikationsdatum: 2015-02-05
    Beschreibung: The aim of connectomics analysis is to understand whole-brain neural connections. This is accomplished using new biotechnologies. Here, we provide an overview of the recent progress in connectomics analysis. The entire neural network of an organism was revealed for the first time in the nematode. Caenorhabditis elegans ( C. elegans ) have an advantage of their limited number of neurons and their transparency, allowing the neural network to be visualized using light and electron microscopes (EMs). It is practically impossible to adopt the same approach for mammals because of the large number of neural cells and the opacity of the central nervous system. A variety of new technologies are being developed to perform computer-assisted high-throughput image acquisition and analysis to obtain whole-brain maps for higher species, including mammals. Diffusion tensor magnetic resonance imaging and tractography and three-dimensional imaging with the EM are examples of novel approaches to connectomics. These new technologies will soon be applied not only to Drosophila , C. elegans and rodent research, but also to comprehensive connectomics analysis in a wide range of species including humans and primates. In the near future, results from connectomics analysis will reveal the neural circuitry of the whole brain and enhance our understanding of the human mind and neuropsychiatric diseases.
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  • 78
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    Oxford University Press
    Publikationsdatum: 2015-02-05
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  • 79
    Publikationsdatum: 2015-02-05
    Beschreibung: Recent developments in electron microscopy largely automate the continuous acquisition of serial electron micrographs (EMGs), previously achieved by laborious manual serial ultrathin sectioning using an ultramicrotome and ultrastructural image capture process with transmission electron microscopy. The new systems cut thin sections and capture serial EMGs automatically, allowing for acquisition of large data sets in a reasonably short time. The new methods are focused ion beam/scanning electron microscopy, ultramicrotome/serial block-face scanning electron microscopy, automated tape-collection ultramicrotome/scanning electron microscopy and transmission electron microscope camera array. In this review, their positive and negative aspects are discussed.
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  • 80
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    Oxford University Press
    Publikationsdatum: 2015-02-05
    Beschreibung: The article reflects on the development of tissue clearing methods in the last decade. This technological innovation has been achieved in the neuroscience community thanks to the combined efforts of molecular biologists, brain anatomists and light microscopists. Although this technology is becoming increasingly diversified, it mostly aims at the large-scale, three-dimensional reconstruction of brain structures.
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  • 81
    Publikationsdatum: 2015-02-05
    Beschreibung: Ultrastructural analyses with electron microscopy have provided indispensable information to understand physiology and pathology of the nervous system. Recent advancement in imaging methodology paved the way for complete reconstruction of the neuronal connection map in the central nervous system, which is termed ‘connectome’ and would provide key insights to understand the functions of the brain. The critical advancement includes serial ultrastructural observation with scanning electron microscopy (SEM) instead of conventional serial sectioning transmission electron microscopy along with specific tissue preparation methods to increase heavy metal deposition for efficient SEM imaging. The advanced imaging methods using SEM have distinct advantages and disadvantages in multiple aspects, such as resolution and imaging speed, and should be selected depending on the observation conditions, such as target tissue sizes, required spatial resolution and necessity for re-observation. Dealing with the huge dataset remained to be a major obstacle, and automation in segmentation and 3D reconstruction would be critical to understand neuronal circuits in a larger volume of the brain. Future improvement in acquisition and analyses of the morphological data obtained with the advanced SEM imaging is awaited to elucidate the significance of whole connectome as the structural basis of the consciousness, intelligence and memory of a subject.
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  • 82
    Publikationsdatum: 2016-02-04
    Beschreibung: Recent technological breakthroughs in image acquisition have enabled single-particle cryo-electron microscopy (cryo-EM) to achieve near-atomic resolution structural information for biological complexes. The improvements in image quality coupled with powerful computational methods for sorting distinct particle populations now also allow the determination of compositional and conformational ensembles, thereby providing key insights into macromolecular function. However, the inherent instability and dynamic nature of biological assemblies remain a tremendous challenge that often requires tailored approaches for successful implementation of the methodology. Here, we briefly describe the fundamentals of single-particle cryo-EM with an emphasis on covering the breadth of techniques and approaches, including low- and high-resolution methods, aiming to illustrate specific steps that are crucial for obtaining structural information by this method.
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  • 83
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    Oxford University Press
    Publikationsdatum: 2016-02-04
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  • 84
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    Oxford University Press
    Publikationsdatum: 2016-02-04
    Beschreibung: Single-particle reconstruction is the process by which 3D density maps are obtained from a set of low-dose cryo-EM images of individual macromolecules. This review considers the fundamental principles of this process and the steps in the overall workflow for single-particle image processing. Also considered are the limits that image signal-to-noise ratio places on resolution and the distinguishing of heterogeneous particle populations.
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  • 85
    Publikationsdatum: 2016-02-04
    Beschreibung: Single particle cryo-EM has recently developed into a powerful tool to determine the 3D structure of macromolecular complexes at near-atomic resolution, which allows structural biologists to build atomic models of proteins. All technical aspects of cryo-EM technology have been considerably improved over the last two decades, including electron microscopic hardware, image processing software and the ever growing speed of computers. This leads to a more widespread use of the technique, and it can be anticipated that further automation of electron microscopes and image processing tools will soon fully shift the focus away from the technological aspects, onto biological questions that can be answered. In single particle cryo-EM, no crystals of a macromolecule are required. In contrast to X-ray crystallography, this significantly facilitates structure determination by cryo-EM. Nevertheless, a relatively high level of biochemical control is still essential to obtain high-resolution structures by cryo-EM, and it can be anticipated that the success of the cryo-EM technology goes hand in hand with further developments of sample purification and preparation techniques. This will allow routine high-resolution structure determination of the many macromolecular complexes of the cell that until now represent evasive targets for X-ray crystallographers. Here we discuss the various biochemical tools that are currently available and the existing sample purification and preparation techniques for cryo-EM grid preparation that are needed to obtain high-resolution images for structure determination.
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  • 86
    Publikationsdatum: 2016-02-04
    Beschreibung: Automated data collection is an integral part of modern workflows in single particle electron microscopy (EM) research. This review surveys the software packages available for automated single particle EM data collection. The degree of automation at each stage of data collection is evaluated, and the capabilities of the software packages are described. Finally, future trends in automation are discussed.
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  • 87
    Publikationsdatum: 2016-02-04
    Beschreibung: The capabilities and application range of cryogenic electron microscopy (cryo-EM) method have expanded vastly in the last two years, thanks to the advances provided by direct detection devices and computational classification tools. We take this review as an opportunity to sketch out promising developments of cryo-EM in two important directions: (i) imaging of short-lived states (10–1000 ms) of biological molecules by using time-resolved cryo-EM, particularly the mixing-spraying method and (ii) recovering an entire continuum of coexisting states from the same sample by employing a computational technique called manifold embedding. It is tempting to think of combining these two methods, to elucidate the way the states of a molecular machine such as the ribosome branch and unfold. This idea awaits further developments of both methods, particularly by increasing the data yield of the time-resolved cryo-EM method and by developing the manifold embedding technique into a user-friendly workbench.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 88
    Publikationsdatum: 2016-02-04
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 89
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2016-02-04
    Beschreibung: This is a brief account of the earlier history of single-particle cryo-EM of biological molecules lacking internal symmetry, which goes back to the mid-seventies. The emphasis of this review is on the mathematical concepts and computational approaches. It is written as the field experiences a turning point in the wake of the introduction of digital cameras capable of single electron counting, and near-atomic resolution can be reached even for smaller molecules.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Publikationsdatum: 2015-12-13
    Beschreibung: The transport of intensity equation (TIE) is a convenient method of obtaining a potential distribution, as it requires only three transmission electron microscopy images with different amounts of defocus. However, the spatial resolution of the TIE phase map has not yet been evaluated experimentally. In this study, we investigated the phase distribution of spherical gold nanoparticles and its dependence on the defocus difference and found that the spatial resolution was finer than 2 nm, even for a defocus difference of 4 µm. Theoretical calculations reproduced the experimental results well.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 91
    Publikationsdatum: 2015-12-13
    Beschreibung: This article proposes a technique for staining bulk grids bearing ultrathin sections with a silicone device consisting of a base plate and a depression bar. Specifically, bulk grids were loaded into the holes on the base plate in order, and then the depression bar was inserted into the slot of the plate to fix the inner edges of the grids and thereby form several separated cells to facilitate the subsequent staining and washing procedures. The results showed that the proposed technique can improve handling efficiency, safety and identification of grids during staining courses.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 92
    Publikationsdatum: 2015-12-13
    Beschreibung: Uranyl acetate (UAc) has been generally used not only as a superb staining reagent for ultrathin sections of plastic-embedded biological materials, but also as high-contrast negative stains for biological macromolecules such as particles of protein or virus. However, the use and purchase of radioactive UAc have been restricted. In this study, we determine the performance of ytterbium triacetate, lutetium triacetate, samarium triacetate and gadolinium triacetate as new staining reagents for biological electron microscopy. We observed chemically fixed spinach ( Spinacia oleracea ) leaves stained with these reagents. Ultrathin sections were stained with these reagents. Some of them were counterstained with lead citrate. The transmission electron microscopy contrast of spinach organelles was evaluated in sections exposed to the conventional stain and new stains. We show acetate salts of samarium, gadolinium, ytterbium and lutetium could be excellent substitutes for UAc for thin section staining and for negative staining. In addition, each reagent showed appreciable negative-staining effects.
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  • 93
    Publikationsdatum: 2015-12-13
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 94
    Publikationsdatum: 2015-12-13
    Beschreibung: In order to analyse the internal structures of multi-component fluid materials such as emulsions (including the inter-particle spacing) by cryo-electron microscopy, it is necessary to observe their smooth cross-sectional surfaces over wide areas. We have developed a system that involves the following steps: preservation of the structure of an emulsion adhesive using freeze fixation in its normal (moist) state and during the drying process after being coated, preparation of cross sections of the internal structure using a cryo-ultramicrotome and then transferral of the cross sections into a cryo-scanning electron microscope for observation via a cryo-transfer system. This system allows the direct observation of the cross sections of emulsions and of several fluid materials.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 95
    Publikationsdatum: 2015-12-13
    Beschreibung: The scanning electron microscope is used in various fields to go beyond diffraction limits of the optical microscope. However, the electron pathway should be conducted in a vacuum so as not to scatter electrons. The pretreatment of the sample is needed for use in the vacuum. To directly observe large and fully hydrophilic samples without pretreatment, the atmospheric scanning electron microscope (ASEM) is needed. We developed an electron filter unit and an electron detector unit for implementation of the ASEM. The key of the electron filter unit is that electrons are transmitted while air molecules remain untransmitted through the unit. The electron detector unit collected the backscattered electrons. We conducted experiments using the selected materials with Havar foil, carbon film and SiN film.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 96
    Publikationsdatum: 2015-12-13
    Beschreibung: Cytoplasmic dynein is a microtubule-based motor protein that transports intracellular cargo and performs various functions during cell division. We previously reported that Lis1 suppressed dynein motility on microtubules in an idling state. Recently, a model showed that Lis1 prevents the ATPase domain of dynein from transmitting a detachment signal to its microtubule-binding domain. However, conformational information on dynein is limited. We used electron microscopy to investigate the conformation of dynein and nucleotide-induced conformational changes on microtubules. The conformation of dynein differed depending on the presence or absence of a nucleotide. In the presence of the nucleotide ADP-vanadate, dynein displayed an extended form on microtubules (extended form), whereas in the absence of a nucleotide, dynein lay along microtubules (compact form). This conformational change reflects chemomechanical coupling in dynein walking on microtubules. We also found that Lis1 fixed the conformation of dynein in the compact form regardless of the nucleotide condition. Removal of the Lis1 dimerization motif abolished Lis1-dependent fixation of dynein in the compact form. This suggests that the idling state of dynein on microtubules induced by Lis1 occurs through the Lis1-dependent arrest of dynein chemomechanical coupling.
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  • 97
    facet.materialart.
    Unbekannt
    Oxford University Press
    Publikationsdatum: 2016-02-04
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Publikationsdatum: 2016-02-04
    Beschreibung: Recent advances in single-particle electron cryo-microscopy (cryo-EM) were largely facilitated by the application of direct electron detection cameras. These cameras feature not only a significant improvement in detective quantum efficiency but also a high frame rate that enables images to be acquired as ‘movies’ made of stacks of many frames. In this review, we discuss how the applications of direct electron detection cameras in cryo-EM have changed the way the data are acquired.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 99
    Publikationsdatum: 2016-02-04
    Beschreibung: Single-particle electron microscopy (EM) provides the great advantage that protein structure can be studied without the need to grow crystals. However, due to technical limitations, this approach played only a minor role in the study of membrane protein structure. This situation has recently changed dramatically with the introduction of direct electron detection device cameras, which allow images of unprecedented quality to be recorded, also making software algorithms, such as three-dimensional classification and structure refinement, much more powerful. The enhanced potential of single-particle EM was impressively demonstrated by delivering the first long-sought atomic model of a member of the biomedically important transient receptor potential channel family. Structures of several more membrane proteins followed in short order. This review recounts the history of single-particle EM in the study of membrane proteins, describes the technical advances that now allow this approach to generate atomic models of membrane proteins and provides a brief overview of some of the membrane protein structures that have been studied by single-particle EM to date.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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  • 100
    Publikationsdatum: 2015-04-03
    Beschreibung: A novel technique for reconstructing the phase shifts of electron waves was applied to C s -corrected scanning transmission electron microscopy (STEM). To realize this method, a new STEM system equipped with an annular aperture, annularly arrayed detectors and an arrayed image processor has been developed and evaluated in experiments. We show a reconstructed phase image of graphite particles and demonstrate that this new method works effectively for high-resolution phase imaging.
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    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Allgemeine Naturwissenschaft , Physik
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