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  • Life and Medical Sciences  (30,791)
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  • 1
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 2
    ISSN: 0741-0581
    Keywords: Photography ; Point source enlarger ; Electron micrograph ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Point source enlargers may cause unusual types of printing defects. One type is a large spot in the center of the enlarged picture field that sometimes appears when the edges of negatives are not adequately masked during printing. Another type is a blurry image caused by a defect in the polycontrast filter. The defect appears in the filter as a small spot of about 1/8-inch diameter, formed, presumably, by heat from the focused beam of the point source light. A spot defect of this type is difficult to see by a cursory visual examination of the filter and may develop unnoticed and persist for months before it is finally recognized.
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  • 3
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 4
    ISSN: 0741-0581
    Keywords: Quick freezing ; Synaptic vesicles ; Cholinergic nerve terminals ; Electric organ ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The limitations of chemical fixation in permitting the 1:1 quantitative correlations required for convincing ultrastructural explanations of cell biological processes are noted. We describe techniques for obtaining highly reproducible direct quick freezing on the polished surface of pure copper bars dipping into a static dewar of liquid N2. The importance and the ease of testing and obtaining bounce suppression with commerically available equipment is emphasized. Artefacts caused by tissue damage and bad freezing are illustrated, and a hitherto unrecognized population of presynaptic membrane attached vesicles is described in Torpedine electric organ. Between 15 and 20% of the synaptic vesicles are attached to ca. 30% of the cytoplasmic face of the presynaptic terminal membrane. There is a close correlation between the occurrence of such attachments and the application of electrocyte basal lamina to the external face. We suggest that these vesicles are the ‘membrane operators,’ ‘vesigates,’ and ‘highly active subpopulation’ of vesicles whose existence has been invoked to explain biochemical data in other laboratories. We further speculate that relatively selective Ca pumping by this immediately submembranous population leads to displacement of acetylcholine (ACh) and reloading with newly synthesized ACh. The preferential release of the latter would then be expected.
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  • 5
    ISSN: 0741-0581
    Keywords: Electron energy loss spectroscopy ; Parallel detection ; Photodiode assays ; Fluorescent screens ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The present report paper deals with the use of a photodiode array for recording electron energy loss spectra in a transmission electron microscope. Important properties of the array are outlined, together with a description of the circuitry needed for interfacing the output to a multichannel analyser.In the direct-exposure mode, the device can easily detect a single (80 or 100 keV) electron, allowing inner-shell energy losses between 200 eV and 2000 eV to be recorded in about 10 seconds. By signal averaging a large number of readouts, a dynamic range of at least 105 is possible. Irradiation damage to the array can be controlled by cooling the array and by various anealing procedures. Sensitivity and DQE are lower, but the dynamic range is higher in the indirect mode, where a fluorescent screen is used to convert the electrons into visible photons, which are then imaged onto the diodes. The choice of screen material and of optical coupling to the array are discussed. Several spectral artifacts are described, together with spectrum-processing techniques designed to remove them.
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  • 6
    ISSN: 0741-0581
    Keywords: Cross-section specimen ; Thin films ; Interfaces ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The structure and chemistry of thin solid films are best studied by transmission electron microscopy (TEM) when they are viewed in cross-section - that is, when the surface normal of the film is made perpendicular to the electron beam. In this orientation, the substrate, the thin film layers, and the interfaces between them can be imaged either simultaneously or individually. Further, information from each of these regions remains distinct from that obtained from the others, eliminating the problems of superimposition that are a consequence of viewing a layered structure in the conventional manner (i.e., parallel to the surface normal). A technique for fabricating TEM specimens that can be viewed in cross-section is described here. Although the majority of our work is with silicon-based materials, the technique can be readily adapted to the study of other systems.
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  • 7
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 8
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 9
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 10
    ISSN: 0741-0581
    Keywords: Morphometry ; Organelle arrangement ; Exocrine glands ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Currently available morphometric methods provide useful information on the three-dimensional properties (such as volume, surface, etc.) of biological structures. These methods, however, do not reveal how the same structures are spatially organized within the cell. A sum of problems, which concern mainly the definition of shape and location of the sectioned structures, does not allow the three-dimensional representation of the organelle arrangement from a quantitative analysis of sections. Following a different approach, this study considers the topographic relationship between ten distinct subcellular structures: nucleus, Golgi, ribosomes, mitochondria, lysosomes, lipid droplets, secretory granules, and apical, lateral, and basal plasmalemma. The analysis of associations from 2 × 2 tables calculated for each pair of structures and the pattern of multiple associations obtained by clustering methods provide a useful description of the spatial relationship among different cell compartments. The results of the investigation carried out in parallel on seven human exocrine glands (pancreas, parotid gland, submandibular gland, lacrimal gland, ceruminous gland, ampulla of the vas deferens, and seminal vesicle) allow an immediate evaluation of the method and a comparative analysis of the cytologic organization of secreting cells of human exocrine glands.
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  • 11
    ISSN: 0741-0581
    Keywords: Selective plasma etch ; Ceramic composites ; Transmission electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Transmission electron microscopy has been used to isolate and examine the intergranular glass phase in hot-pressed silicon nitride/silicon carbide composites. Previously there have been difficulties in locating a suitable region for studies of this nature because the interfering nitride and carbide grains inhibit isolation of the glass for examination. Radiofrequency plasma etching of thinned sections of 6 wt% Y2O3, 2 wt% A12O3 in Si3N4 containing 30 vol% of SiC proved to be fruitful in isolating the glass phase. A mixture of CF4 and O2 quantitatively remove the acicular nitride phase without any evidence of attack on either the glass or carbide. Composites containing ceria and magnesia as substitutes for yttria behave similarly. This indicates that glasses containing minor to major concentrations of elements forming stable fluorides inhibit the attack of fluoride ions on silica glasses containing these elements.
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  • 12
    ISSN: 0741-0581
    Keywords: Ewald sphere ; Refraction ; Specular reflection ; Double diffraction ; Diffraction geometry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A three-dimensional analysis in reciprocal space is used to analyse reflection high energy electron diffraction (RHEED) patterns. Particular emphasis is placed on investigating the surface resonance phenomenon, the resonance conditions, and the diffraction mechanisms. The surface resonance regions defined by the resonance beam threshold conditions are related to the limits for the specular reflection spot in the diffraction pattern. The introduction of an Ewald sphere of varying radius is shown to be useful in understanding the surface phenomenon. Simulations based on the geometric theory, taking account of the surface refraction effect, describe very well the RHEED pattern geometry from the (111) surface of a platinum single crystal.
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  • 13
    ISSN: 0741-0581
    Keywords: Plastic flow ; Section surface relief ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The technology of ultramicrotomy is now well established, but the properties of the resin that determine the different forces needed to generate a section have been neglected, although this process could introduce artefacts in the thin sections. We have investigated the principal resin dependent factors involved in the sectioning process and determined the related mechanical properties. Tensile experiments have given the best correlation with the sectioning quality of the resin: the elastic (Young's) modulus value (depending on polymer structure or hardening mode), the presence of a short plastic flow for a controlled fracture and enough flexibility to minimize shearing, and internal cracks, appear to be the main characteristic parameters. The ultrathin section seems to be generated by a process close to cleavage, favoured by the relative hardness of the embedding media, while machining and “true” sectioning requires softer resins.Consequently, the rupture follows the path of least resistance in the specimen-resin composite, providing sections with a surface relief. Embedded biological material copolymerizes with polycondensed matrix (epoxy resins), and, by reducing the heterogeneity, gives smoother sections. Embedments hardened by radical polymerization provide a rougher relief, since almost no copolymerization occurs, offering to the microtome a heterogeneous block with two constituents of very different mechanical properties. The surface relief seems to be an important factor in labelling, staining, and imaging, and more attention has to be paid for some improvements of the quality of the information provided by electron microscopy.
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  • 14
    ISSN: 0741-0581
    Keywords: Ultramicrotomy ; Thin sectioning ; Microtome knives ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Low-angle chromium metal shadowing was used to compare the surface roughness of ultrathin sections cut with diamond, sapphire, and glass knives. Surface roughness was less on diamond-cut and sapphire-cut sections than on glass-cut sections, and was greater over tissue than resin, and greatest over red blood cells and mitochondria. Surface roughness contributed to image density variation and thereby lowered contrast and informational content of the sectioned tissue.
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  • 15
    ISSN: 0741-0581
    Keywords: Microdomains ; Frank-Kasper phases ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The Laboratory of Atomic Imaging of Solids is dedicated to the direct imaging of materials in various fields of solid-state sciences at the atomic or molecular level. The main programs of this laboratory are briefly described, including quasicrystals, new phases and microdomains in Frank-Kasper phases, suboxides of metals, catalysts, minerals found in China, and molecular structure of organic substances. A recent systematic investigation of domain structures consisting of juxtaposed icosahedral columns is also presented.
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  • 16
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Microanalysis ; EDS ; HREM ; Coherence ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The intensity distribution in the microdiffraction pattern depends strongly on the coherence of the illuminated source. The coherence width at the specimen level is considered as a parameter to check the coherence of an electron microscope. Two application examples are illustrated. A small interphase precipitate of MgNi2 in an Ni superalloy has been identified by a combination of microdiffraction and energy dispersive spectrum (EDS) techniques, though it can not be found by conventional transmission electron microscopy (TEM) and selected area diffraction (SAD). By means of microdiffraction as well as high-resolution electron microscopy (HREM) imaging a defect structure has been determined. Such a defect makes the lattice extinction spots appear with various intensities in the selected area diffraction and microdiffraction patterns.
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  • 17
    ISSN: 0741-0581
    Keywords: Cross-sectional transmission electron microscopy (XTEM) ; LSI circuit ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Cross-sectional transmission electron microscopy (XTEM) has been used to diagnose silicon LSI circuits and Josephson junction devices. For LSI circuits, some typical failure problems have been presented. For Nb-Si-Nb Josephson junction, microholes in the thin silicon layer have observed, and they are responsible for the short circuiting of these devices.
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  • 18
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 19
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Electron and ion optics ; Aberration ; Deflection ; Multiple fields ; Phase retrieval ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: This paper summarizes theoretical research on electron optics in the field of electron microscopy that has been carried out by the author and his colleagues over a long period of time. The main topics to be discussed include the rotationally symmetrical imaging system and its aberrations; the method of matrix algebraic calculation and its applications to electron optics; new developments in scanning electron beam systems, i.e., the combined elec-tromagnetic focusing-deflection system with superimposed fields; the electromagnetic multipole system and its aberrations; the ion optical system with a curvilinear axis and its aberrations; and the phase retrieval in Fourier electron microscopy. This review may help to promote a better understanding of the present state of, and trends in, Chinese electron optics research.
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  • 20
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Heteroduplex mapping ; Lentiviruses ; Retroviruses ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A novel human lymphotropic virus capable of crippling the immune system by infecting and destroying T4 antigen-positive cells is now known to be the etiologic agent of the acquired immune deficiency syndrome (AIDS). The AIDS or human immunodeficiency virus (HIV) belongs to a family of RNA viruses called retroviruses. Several strains of HIV have been molecularly cloned, and DNA sequence comparisons have established that the proviral DNA genome is 9.7 kilobase pairs. The genome possesses characteristic retrovirus features including structural genes, flanked by long terminal repeats, in the order gag, pol, and env and, in addition, four unique nonstructural genes, several of which appear to be essential in regulating virus replication. Electron microscopy has played an important role in elucidating structural, genetic, and molecular properties of HIV and has aided in its classification as a member of the Lentivirnae retrovirus subfamily. Heteroduplex mapping methodologies pertinent to these findings are described. Although the relationships show considerable divergence, the similarities between HIV and lentiviruses are profound and encompass an indistinguishable morphology, genome sequence homology and topography, genomic diversity, and overlapping biology, including a preference for infecting cells of the immune system, a cytopathic effect in vitro, and the ability to produce a persistent, slowly progressing, degenerative disease in vivo. The newest HIV class (HIV-2) has recently been molecularly characterized. HIV-2 also bears all the hallmarks of a lentivirus but is more closely related to simian immunodeficiency viruses than the previously described HIV-1, despite a similar biology. The HIV-lentivirus phylogenetic relationship has broad implications for the AIDS disease process and has given new importance to the study of the natural history and pathogenesis of animal lentiviruses in searching for clues to prevent the spread of AIDS.
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  • 21
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Light microscopy ; Protozoal diagnosis ; Protozoal therapy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Several protozoa have emerged as the major opportunistic infections and cause of death in patients with acquired immunodeficiency syndrome (AIDS). Pneumocystis carinii pneumonia is the leading cause of death in AIDS patients. Electron microscopy (EM) usually shows numerous trophozoites and cysts of Pneumocystis filling up the entire alveolar space, while only cysts are seen under the light microscope. The focal thickening of cyst wall of Pneumocystis, as demonstrated by EM and manifested as a “parentheses” shaped structure with silver stain, serves as a diagnostic marker for Pneumocystis. Freeze-fracture EM has demonstrated the intimate contact between Pneumocystis trophozoites and the type I pneumocytes, which may contribute to the alveolar-capillary block, leading to severe respiratory distress. However, EM is seldom needed for the diagnosis of this infection.Toxoplasma encephalitis, which is an unusual clinical manifestation in cases of toxoplasmosis reported previously, has become a common complication and one of the major causes of death in patients with AIDS. Because subclinical infection by Toxoplasma is common, serologic tests usually offer no definite answers as to whether the infection is acute or chronic, active or past. The small size and its non-specificity in both morphology and tissue affinity make light microscopic diagnosis of toxoplasmosis difficult. Only immunologic staining, such as immunoperoxidase and immunofluorescence, can help to achieve a definite positive identification of the organism. When special antibodies or facility for such staining is not available, EM is the final resort for identifying Toxoplasma by showing the apical complex with the characteristic sausageshaped rhoptries.Cryptosporidiosis, practically unknown before the AIDS outbreak, has become one of the most common intestinal protozoa in both immunocompromised and immunocompetent patients. The protracted and sometimes fatal course of cryptosporidiosis in immunocompromised patients can be explained by the presence of autoinfective oocysts (thin-walled oocysts), as detected by EM, and by recycling of first-generation schizonts observed experimentally. While diagnosis of cryptosporidiosis can be made by detection of oocysts in stools in most cases, EM is still the last resort for a definitive identification of Cryptosporidium species.While the incidence of isosporiasis is still low, it has been found more frequently in patients with AIDS than in the general population. The parasite, Isospora belli, being a coccidian as is the Cryptosporidium species, is similar to the latter in its life cycle and clinical manifestations. However, the morphology of its diagnostic stage, the oocyst, is quite different from Cryptosporidium and it is much larger than the latter. The oocyst of Isospora belli, usually containing one sporoblast, can be detected by light microscopy in stools.Microsporidiosis, having been known only recently, is also relatively common in immunocompromised patients, including four patients with AIDS. Although this protozoan can be detected by light microscopy and its polar granules, identified by the periodic acid-Schiff or methenamine silver stain, are characteristic, a definitive diagnosis of microsporidiosis still depends on EM.
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  • 22
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Strongyloides stercoralis ; Strongyloidiasis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Strongyloides stercoralis, the only helminthic parasite that can complete its life cycle in the human host, is also the only helminthic parasite that has been reported with any frequency in AIDS patients. Symptoms include hives, skin eruptions, abdominal pain, perianal pruitis, diarrhea, and pneumonitis. Diagnosis is made by demonstrating rhabditiform larvae in the stool or female parasitic worms and eggs in the small intestinal mucosa; in disseminated cases, rhabditiform or filariform larvae can be found in liver, heart, lungs, thyroid, kidneys, adrenals, pancreas, lymph nodes, and central nervous system. Successful treatment has been achieved with thiabendazol. Strongyloidiasis is uncommon, but since cell-mediated immunity is important in combatting this organism, and since T-lymphocyte function is impaired in AIDS patients, strongyloidiasis should not be overlooked in the diagnosis of opportunistic illnesses in these individuals.
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  • 23
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 24
    ISSN: 0741-0581
    Keywords: Axonal degeneration ; Electron microscopy ; Human ; Visual pathways ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: It is a widely held belief that the products of axonal degeneration in the CNS are transitory and are caused by metabolic and phagocytic processes. However, recent light microscopic examinations of human and primate brains using the paraphenylene diamine staining method (PPD), which stains degenerating axons, have confirmed that the products of degeneration persist for years in visual pathways. The routine utilization of the PPD method for delineating human visual pathways requires further confirmation of axonal degeneration. Optic nerves, optic tracts, and lateral geniculate nuclei were collected from human brains that had clinical documentation of optic nerve damage prior to death. Optic nerves, optic tracts, and lateral geniculate nuclei taken from the brains of cynomolgus monkeys that had undergone enucleation 3 months to 1 year prior to sacrifice were also examined. All tissue was processed for electron microscopy; ultrathin sections were cut for electron microscopy, and consecutive sections were cut for light microscopy.In all cases, the homology of the degenerated processes was confirmed between the light microscopic (PPD) and the electron microscopic sections. Such ultrastructural examination demonstrates that the products of axonal degeneration remain in the primate visual system longer than previously supposed.
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  • 25
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 26
    ISSN: 0741-0581
    Keywords: TEM sample preparation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 27
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 28
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 29
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 30
    ISSN: 0741-0581
    Keywords: HVEM ; EM ; Three-dimensional reconstruction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The methodology is described, as developed at the Albany NIH Biotechnological High Voltage Electron Microscope Resource, for the three-dimensional reconstruction of objects in thick sections. The reconstructions are obtained from projection sets which are recorded by high voltage electron microscopy. The different steps of the procedure are illustrated in detail, using the cilium reconstruction as an example.
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  • 31
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 32
    ISSN: 0741-0581
    Keywords: 3-D reconstructions ; Computer ; Graphics ; Tastebud ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We have prepared software for producing three-dimensional reconstructions from serial micrographs using an IBM PC or compatible. The software can be configured for a variety of graphics board and digitizing tablet combinations.Data is entered into the program by digitizing contours directly from micrographs. The program can handle up to 2,000 contours per data file, of up to 255 object types. Morphometric information such as line length, perimeter, and area are generated for each contour. The reconstruction program aligns the plane information from each section and displays the final reconstruction on a high resolution (640 × 400 pixels) color monitor. Object types can be differentiated by line width, line color, and fill color. Hidden line processing and conditional fill routines make it possible to produce reconstructions with either a solid or semi-transparent appearance. Reconstructions can be generated quite rapidly from any viewing angle in the X, Y, and Z axes. The program has proven valuable for the elucidation of the three-dimensional nature of biological structures.
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  • 33
    ISSN: 0741-0581
    Keywords: Immunoelectron microscopy ; Cryoultramicrotomy ; Monoclonal antibodies ; Striated muscle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A systematic approach to the discovery of new proteins of ultrastructural interest is discussed. It involves the merging of monoclonal antibody technology with immunocytochemical technology, particularly immunoelectron microscopy. In this approach, monoclonal antibodies are raised to a cellular preparation that can be grossly heterogeneous in its protein composition. The hybridoma culture fluids are screened by immunocytochemistry for the ultrastructural localization of their antibodies. Those monoclonal antibodies that show specific ultrastructural localizations of interest are then selected for further investigation. The antigen to which a given monoclonal antibody is directed is then identified by immunoprecipitation and immunoblotting with that antibody. By this approach, two new striated muscle proteins of ultrastructural interest have been discovered and are named zeugmatin and enactin. The former is a protein of over 500 kD localized by immunoelectron microscopy to the Z-bands, the latter of 245 kD localized to the N1 line of striated muscle.
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  • 34
    ISSN: 0741-0581
    Keywords: Lung ; Freeze-fracture ; Endocytosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Electron microscopic examination of freeze-fracture replicas reveals distinctive arrangements and planar distributions of certain membrane constituents. In these replicas, the square (orthogonal) array of 6-7-nm intramembranous particles is an easily recognizable membrane differentiation commonly observed in transepithelial ion-transporting epithelia and in several mesenchymal cells, in which they were originally described. Recently, the occurrence, distribution, and number of square arrays have been documented in the lungs of mammals, turtles, and frogs. The current study confirms that there are more than 10 arrays per μm2 basal and lateral portion of the plasma membrane in the alveolar type I and ciliated cells of human, rat, guinea pig, turtle, and frog lung, and in type II pneumocytes of the turtle and frog lung. We have not observed them in mucous cells, brush cells, macrophages, or endothelial cells of any species examined, nor do they appear in the apical portion of the plasma membrane of any airway or alveolar lining cell. Upon elastase or other proteolytic dissociation of the alveolar cells of the mammalian lung, concomitant with breakdown and endocytosis of tight junction strands, the square arrays cluster and are internalized within the membranes of endocytic vesicles that are derived from the lateral and basal portions of the cell. Within 1 day of establishing the cells in tissue culture, tight and gap junctions reappear, but the square arrays do not. Nor do they return to cultures examined on subsequent days. We conclude that the square array is a widespread membrane differentiation throughout the lung and major airways; but extrapolating from results obtained from dog tracheal cells (Widdicombe et al., 1987), the square array configuration of particles is unnecessary for maintaining normal ion transport.
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  • 35
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    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 36
    ISSN: 0741-0581
    Keywords: Fixation ; Processing ; Electron microscopy ; Human biopsies ; Diagnosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Transmission electron microscopy serves a useful and often diagnostic purpose in the analysis of human disease. The emerging discipline of ultrastructural pathology serves a much wider field than that of kidney pathology and, of necessity, requires two essential elements. These are (1) the interpretive knowledge which covers all cells in all tissues which compose all organs, their normal substructural composition, and the ultrastructural expression of all of the basic mechanisms of the pathobiology of human disease, and (2) technically excellent preparations of these varied specimens.In this review, we emphasize the technical aspects necessary for the preparation of these specimens. These include the handling of varied specimens from the time of interruption of blood flow to the sample until fixation, fixation methodology, and routine processing methods for electron microscopy. Specialized techniques that are readily accomplished in an ultrastructural pathology service laboratory are also described. These include methods for the demonstration of glycogen, peroxidase(s), the glycocalyx. We also describe the preparation of permanent, alkaline Giemsa-stained 1-μm plastic sections for light microscopic diagnosis, the use of an agar-pelleting technique to change cell suspensions into readily handled blocks, and the use of Spurr's (J. Ultrastruct. Res. 26:31, 1969) low viscosity embedding for all skin and heavily collagenized specimens.The diagnostic report for individual samples can routinely be available within 24 hours of specimen arrival in the ultrastructural pathology laboratory with the methods we review here. Examples of these varied samples of human tissues and cells and methods for preparing them are illustrated. We have found such methods useful for diagnostic purposes, e.g., to identify the site of origin of a brain metastasis as the alveolar cell (type II pneumocyte) of the lung, based on the presence of typical lamellar (surfactant) bodies in the metastatic tumor cells (Dvorak and Monahan-Earley: Norelco Reporter 32:29-36, 1985c), as well as to describe for the first time a new tumor, such as the gut autonomic nerve (GAN) tumor (Walker and Dvorak: Arch. Pathol. Lab. Med. 110:309-316, 1986) or a cell injury process, axonal necrosis, to be characteristic of Crohn's disease (Dvorak et al.: Hum. Pathol. 11:620-634, 1980d; Dvorak and Silen: Ann. Surg. 201:53-63, 1985).
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    New York, NY : Wiley-Blackwell
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Natural Sciences in General
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Natural Sciences in General
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 46
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 47
    ISSN: 0741-0581
    Keywords: Endothelial cells ; Fibrinogen ; Scanning electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 48
    ISSN: 0741-0581
    Keywords: Electron microscopy ; Image processing ; Pseudo color ; Digital frame store ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: An on-line television-rate digital frame store device is utilized to provide color representations of a wide range of electron microscope images and image data. Various types of hardware devices in the frame store coupled with software manipulations via the host computer make rapid image acquisition, modification, measurement, and full-color display possible in real time either from micrographs or directly from an electron microscope. Lookup tables used in conjunction with grey-level image memories can be controlled from a menu display to provide a wide range of color-coding schemes and sequencing. It is also possible to use color graphics overlays and alpha numeric displays along with full-color image displays. This paper will describe many of the recent applications of color developed for electron microscopy studies of materials.
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  • 49
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    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Layered crystals ; Thin films ; Cleavage ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A rigid peripheral clamp with an annular heater is used to bond layered crystals to grids with a thermoplastic adhesive. The layered crystals are subsequently cleaved with adhesive tape while bonded to the grid. The final layered crystal thin film covering a grid opening is exposed only to room air and is free from adhesive or fluid contamination. The results of preparation of several layered crystals, including muscovite mica, molybdenite, and talc, are described.
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    ISSN: 0741-0581
    Keywords: Sample preparation ; Ceramics ; Powders ; Ion milling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A new method of preparing TEM samples from powders is described. The method consists of compacting epoxy-powder composite mixtures in special molds by centrifuging prior to polymerization. The compact is then ion milled by standard methods. Samples prepared in this way are currently being used to study dislocation structures developed during processing of ceramic powders.
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  • 51
    ISSN: 0741-0581
    Keywords: Image autocorrelation function ; Reversible transform ; Noise autocorrelation radius ; Noise removal ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A method for a reversible transform between an image and image autocorrelation function has been devised, and it has been applied to the reduction of random noise in a microscope image. Object-related features of an image signal as well as noise features are overlapped at the vicinity of the origin of an image autocorrelation, and a peak is formed at this position. The present method removes the noise contribution in this peak and returns the autocorrelation function, thus corrected, to the image. An autocorrelation function is computed by two Fourier transforms as based on the convolution theorem. The inverse transform from the image autocorrelation function is made possible by performing two Fourier transforms in reverse to the above. This method has been developed to remove random noise more accurately from a single image (especially for nonperiodic images) than other image-processing methods such as smoothing techniques and low pass filtering.
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  • 52
    ISSN: 0741-0581
    Keywords: Sarcoplasmic reticulum ; Golgi “stain” ; Skeletal and cardiac muscle ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The classical black reaction developed by Camillo Golgi is shown to impregnate the tubules and fenestrations of the sarcoplasmic reticulum (SR) in striated muscle. This is a double impregnation of chromate and silver, which usually fills extracellular spaces. The method is difficult insofar as long incubation times are required, and location of the successfully “stained” SR in plastic-embedded tissue blocks is unpredictable. The light microscope is absolutely necessary to find the good regions which can then be cut from the blocks in 1-μm-thick sections and examined in the electron microscope. Stereo pairs give the best results since these resolve overlap problems common to thick sections. A variety of artifacts are illustrated which can help avoid erroneous interpretations. The Golgi-“stained” SR shows this elusive network with unsurpassed contrast and should benefit the morphological studies of muscle-membrane enthusiasts.
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  • 53
    ISSN: 0741-0581
    Keywords: Ice ; Charging ; Phi-Rho-Zed curves ; Windowless detector ; Fracturing ; Oxygen ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The analysis of bulk frozen-hydrated biological samples has developed now to a level where practical application of the technique is possible. Provided the sample is carefully coated with a conductive metal, the development of a space charge capable of causing a significant distortion of the electron diffusion volume does not seem to occur, and analytical resolution can be conveniently held to approximately 2 μm (both depth and lateral resolution). Two valid quantitative methods are available, and two methods of determining dry weight fractions are also available. An area where further research could lead to improvement in analysis of frozen-hydrated bulk samples is in the investigation of fracturing methods. If fracture planes that were flat and reproducible could be easily obtained, some of the difficulties of analysing frozen-hydrated bulk samples would be considerably reduced.
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  • 54
    ISSN: 0741-0581
    Keywords: Electron probe beam diameter ; Digital image processing ; Acutance ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The present report illustrates a computerized method for precise measurement of the diameter of an electron beam. The value of this measurement extends beyond simply providing an accurate estimate of resolution. Other salient areas which will benefit include quantitative X-ray microanalysis, energy loss spectroscopy, diffraction studies, and electron beam lithography. The biological sciences as well as the material sciences will gain enormously from improved accuracy in measurement (control) of beam diameter. It is anticipated that most or all of the mathematical manipulations outlined in this paper will be incorporated into digital electronic packages which will perform the functions automatically for setting the electron beam diameter to the scientist's choice. The purpose of the present report is to indicate some of the principles involved so that as electron microscopy becomes more computerized and automated, the user will have some understanding of what the electronics are doing rather than simply depressing a button or two and ignoring the power of what resides within the walls of the instrument.The performance of a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM) is roughly determined by the incident electron probe beam size (diameter) involving a sufficient electron current. In the present paper, the diameter of an ultrafine electron beam is measured indirectly from the information given by the blurring of an edge in a STEM or a SEM image of a crystalline specimen with fine, sharp edges. The obtained data were processed by digital image processing methods which give an accurate value of the beam diameter. For confirming the validity of this method, a suitable simulation based on the convolution theorem was performed. By using this measurement, we could measure the diameter of an ultrafine electron beam down to 2 nm, which could not be measured easily by previous techniques.
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  • 55
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    New York, NY : Wiley-Blackwell
    ISSN: 0741-0581
    Keywords: Elemental analysis ; Ultrastructural cytochemistry ; Enzyme histochemistry ; Biogenic amines ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: X-ray microanalysis (XRMA) has been applied to a wide variety of cytochemical problems, but the most valuable applications have been to the validation of cytochemical methods (by the qualitative or quantitative analysis of reaction products), and to the simultaneous localization of more than one substance, which cannot easily be achieved by using alternative methods. The latter applications involve stoichiometric studies (the quantitative relationships between reaction products and substrates), and distribution studies. Ultrastructural cytochemistry with XRMA is limited by the need to use high-brightness electron sources. Apart from the limited availability of such sources, they may cause unacceptable damage to the specimen.Preparation methods for cytochemistry using XRMA are reviewed; in principle these do not differ from those used for other cytochemical applications, but it is important not to introduce extraneous elements (from fixative, buffer, or embedding medium) into the specimen, where the additional X-ray peaks may interfere with the analysis.Quantification in XRMA of cytochemical preparations poses special problems, because the addition of the reaction product to the specimen alters the yield of continuum X rays, used for assessing the mass of the specimen, and also dilutes endogenous elements. However, measurement of ratios between characteristic elemental peaks is a useful method in X-ray microanalytical cytochemistry, and it is concluded that one of the most important attributes of XRMA for cytochemical purposes is the ease with which the substances of interest can be measured.
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  • 56
    ISSN: 0741-0581
    Keywords: Morphometry ; Electron microscopy ; Computer program ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A computer program is described that facilitates systematic and unbiased sampling in morphometry. Input data are coordinates of the four corners of a section as displayed in the position indicators of the microscope stage. Outputs are coordinate values in the form of a regular lattice that describes where to place the stage and perform the sampling on the section. In addition, some other data are provided by the program, such as total area of section, length of sides, etc. The program is written in BASIC but can be easily converted to other computer languages.
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  • 57
    ISSN: 0741-0581
    Keywords: Embedment media ; Coagulant and noncoagulant fixatives ; Intracellular surfaces ; Scanning electron microscopy ; Thick sections ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Conventional plant histological specimens fixed in formalin-acetic acid-alcohol, chromic acid-acetic acid-formaldehyde, or glutaraldehyde-osmium and embedded in either paraffin or plastic are examined as possible rapid methods for providing an alternative image of cellular structure by using scanning electron microscopy. Using the mitotic figures of actively growing onion root tips as a study specimen, the organization of the nucleus and spindle apparatus is reasonably well preserved as compared with isolated mitotic spindles and studies of mitosis in endosperm tissue. Relief of internal structure in this technique is obtained through the coagulant nature of the fixative. Used judiciously, this technique can reveal aspects of the three-dimensional nature of internal tissue structure that may otherwise be difficult to discern.
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  • 58
    ISSN: 0741-0581
    Keywords: Ultrathin frozen sections ; Electron microscopy ; Immunocytochemistry ; Cryobiology ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A description of ultrathin frozen sectioning is presented. Small pieces of lightly-fixed but unembedded tissue are cryoprotected in 80% sucrose, mounted on chucks and frozen in liquid nitrogen. Frozen sections approximately 100 nm thick for electron microscopy are cut at about -90°C, using a cryosectioning unit mounted on a conventional ultramicrotome. Sections are picked up from the surface of the knife with a droplet of 80% sucrose, and are applied to membrane-coated EM grids at room temperature. The mounted sections are then used for EM immunocytochemistry. Essentially the same sectioning procedure can provide frozen sections 1 μm thick for light microscope immunocytochemistry.
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  • 59
    ISSN: 0741-0581
    Keywords: Decay measurements ; Electron-beam-induced current ; Hydrogenated amorphous silicon ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A simple method for decay measurements of the charge collection mode (commonly referred to as electron-beam-induced current or EBIC) of an electron probe instrument is presented. The decay, which occurs at continuous electron irradiation, should be distinguished from a decay measurement due to the electron beam blanking. This method could be applied to other modes of an electron probe instrument, e.g., cathodoluminescence, in studying electron-beam-sensitive semiconductors. An example of the decay of the EBIC signal in a hydrogenated amorphous silicon device is presented.
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Natural Sciences in General
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    ISSN: 0741-0581
    Keywords: Image processing ; Lattice defects ; Bacterial surface protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The surface protein of the archaebacterium Pyrodictium occultum forms two-dimensional periodic arrays of extremely poor order. Two variants of correlation averaging have been applied in order to retrieve the unit cell structure from electron micrographs of negatively stained samples: straightforward correlation averaging correcting for lateral displacements only and a more elaborate approach, including a partial compensation for rotational disorder. Surprisingly, both routes yield virtually identical structures. Inclusion of molecular motifs from highly disordered domains, which are rejected in the “straightforward” approach, appears not to improve resolution, possibly because the high local strain tends to distort the individual molecules.
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