bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transmission electron microscopy studies of plasma‐etched silicon nitride/silicon carbide composites
Authors: Pink Francis X. , Ostreicher Kim J. 
Published: February 2005

AbstractTransmission 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.
A computer program for morphometry of circular and elliptical profiles on the microscope
Authors: Núñez‐Durán Harol , Riboni Laura 
Published: February 2005

AbstractWe describe a short computer program, which is written in Pascal language, to measure the diameter of circular and elliptical profiles in sections. Coordinate pairs on the microscope stage, corresponding to two or three points of a profile, are input to obtain its diameter. The program enables one to take measurements directly on the microscope, thereby reducing photographic work and caliper measurement. While the program is largely designed for electron microscopy, it also may be useful for light microscopy morphometry.
Data acquisition system for maximum‐likelihood analysis of electron microscopic autoradiographs
Authors: Fuhrmann Daniel R. , Brown Michael A. , Miller Michael I. , Roysam Badrinath , Saffitz Jeffrey E. , Thomas Lewis J. 
Published: February 2005

AbstractEMAMAP is a program for the data acquisition phase of maximum‐likelihood analysis of electron microscope autoradiographs. This program is written in C and has been implemented on a Masscomp MC‐500 which supports a graphics processor and a digitizing tablet. The image analysis is automated at a low level: the program operator outlines the edges of the structures of interest using the digitizing tablet, while contiguous regions formed by closed contours are automatically filled by the software. The resulting image is compressed for efficient storage by a quadtree encoding technique for which data compression ratios of greater than 25:1 have been achieved. In practical terms this implies that the data from a typical experiment of 50 autoradiographs could be stored on a single floppy disk. The system is currently in use for acquiring actual biological experimental data.
Structural studies of lanthanide phthalocyanines by high‐resolution electron microscopy
Authors: Zhang W. P. , Kuo K. H. 
Published: February 2005

AbstractEpitaxial films of lanthanide phthalocyanines (LnPc2H, Ln = Nd, Tb, Er, Tm, Yb, or Lu) formed on a KCl or NaCl crystal have been studied by means of high‐resolution electron microscopy. These complexes are isomorphous and have both tetragonal and base‐centered orthorhombic structures. Though radiation damage makes it difficult to study these beam‐sensitive materials by electron microsocpy, the behaviors of thin film growth and details of structural defects can still be identified at the molecular level.
Computer software for specimen orientation adjustment using double‐tilt or rotation holders
Authors: Chou C. T. 
Published: February 2005

AbstractComputer software for specimen orientation adjustment relative to the incident electron beam has been developed. The difficulties encountered when tilting severly strained, highly beam‐sensitive, or small‐grain‐size specimens with known structures using either a double‐tilt or a rotation holder in transmission electron miscroscopy (TEM) can be minimized. Combined with computer programs for obtaining the reduced bases from diffraction patterns, the software is also useful for unknown crystals. The algorithm is introduced and examples are given.
Quasicrystals and noncrystallographic symmetry
Authors: Kuo K. H. 
Published: February 2005

AbstractNew findings on quasicrystals with icosahedral, octagonal, decagonal, and dodecagonal symmetries obtained recently in the Beijing Laboratory of Electron Microscopy, Chinese Academy of Sciences, are presented. Special emphasis is put on the relation between quasicrystalline and crystalline structures. The important role played by electron diffraction and high‐resolution electron microscopy in revealing these quasiperiodic structures is pointed out.
Microdiffraction and analysis
Authors: Zhu Jing 
Published: February 2005

AbstractThe 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.
Ultrastructural and paraphenylene studies of degeneration in the primate visual system: Degenerative remnants persist for much longer than expected
Authors: Johnson Betty M. , Sadun Alfredo A. 
Published: February 2005

AbstractIt 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.
A simple device to aid tissue processing of large numbers of blocks for light or electron microscopy
Authors: Smith K. J. , Larramendi P. C. H. 
Published: February 2005

AbstractA simple device is described that aids the processing of large numbers of tissue blocks for light or electron microscopy. The device has a number of compartments into which different tissue blocks can be placed. Each compartment has a fine mesh floor, allowing the free exchange of the reagents used in tissue processing, and a gentle flow of the reagents is promoted by a magnetic stirring bar, or a rotary mixer. All the materials used are resistant to solvents such as propylene oxide. The device is labor‐saving in that many blocks can be processed as easily as a single block. The device may also be of value in quantitative microscopy, since it ensures that all tissue blocks examined experience an identical processing history.
High Tc ceramic superconductors: Introduction, background, and challenges to the electron microscopist
Authors: Davies Peter K. 
Published: February 2005

AbstractThis introductory article reviews the recent developments in high Tc superconducting ceramics. Particular emphasis is given to the structural and chemical aspects of these compounds that may be of interest to the electron microscopist. Included are some of the contributions made by electron microscopy techniques over the last 10 months. The applications of electron microscopy to solving practical problems associated with these exciting new materials are also discussed.
Structural characterization of Ba2YCu3O7 by high resolution transmission electron microscopy
Authors: Ourmazd A. , Spence J. C. H. , Zuo J. M. , Li C. H. 
Published: February 2005

AbstractWe show that high‐resolution transmission electron microscopy can be used directly to reveal the structure of the metal framework and its defects in Ba2YCu3O7. The use of dynamical effects under carefully selected and controlled conditions allows the detection of long‐range order in the disposition of the oxygen vacancies, but inevitable misalignments make the quantification of the order parameter difficult. Specimen preparation methods are compared, and a wide‐angle convergent‐beam pattern is demonstrated.
Structure of superconducting thin films of YBa2Cu3O7−x grown on SrTiO3 and cubic zirconia
Authors: Tietz L. A. , De Cooman B. C. , Carter C. B. , Lathrop D. K. , Russek S. E. , Buhrman R. A. 
Published: February 2005

AbstractThin films of the superconductive oxide YBa2Cu3O7−x have been made by electron‐beam coevaporation of the metals in an oxygen atmosphere onto single‐crystal {001}‐oriented SrTiO3 and yttria‐stabilized zirconia (YSZ) substrates. The oxide films were superconducting in the as‐deposited state (Tc = 81–83K, Jc = 106 A/cm2 at 4.2K). Bright‐field imaging, selectedarea diffraction (SAD), and high‐resolution imaging in the transmission electron microscope were used to characterize the microstructure of these films. All of the films were polycrystalline. On SrTiO3 the films were oriented, for the most part, with {110} parallel to the substrate surface. On YSZ, two microstructures were observed: one with smaller rectangular grains oriented with (100) or (010) parallel to the substrate surface and the other with (001) parallel to the surface (i.e., c‐axis up).
High‐resolution electron microscopy of high‐temperature superconductors
Authors: Marks L. D. , Li D. J. , Shibahara H. , Zhang J. P. 
Published: February 2005

AbstractWe review recent results obtained at Northwestern using high‐resolution electron microscopy to study high‐temperature superconductors. While in general these materials form large, very perfect single crystal grains which display very few imperfections, there is also evidence of slip defects, amorphous regions, and order‐disorder transformations. We also report that the gadolinium‐based superconductors and in one case yttrium‐based superconductors show evidence for some copper solid solubility in the form of copperrich planar defects. The structure of a metastable trigonal polytype is also reported, as are the effects of electron beam and water vapor damage to the materials.
Preliminary study of electron‐energy‐loss spectra of YBa2 Cu3O7−δ
Authors: Batson P. E. , Chisholm M. F. 
Published: February 2005

AbstractWe have obtained the electron‐energy‐loss spectra below 1,000 eV for YBa2Cu3O7−δ. The spectra show contributions from all elemental constituents, although the Y‐signal is very weak owing to its small concentration. The low‐loss region and the Ba‐core losses are very similar to those obtained for BaO. The Cu absorption is similar to that seen in CuO with minor differences relating to Cu concentration and anisotropy. The oxygen 1s absorption has a shape that is quite different from that obtained in CuO and shows striking orientational anisotropy. Radiation damage in the microscope is a problem and leads to changes in the shape of the oxygen edge.
Containment system for the preparation of vitrified‐hydrated virus specimens
Authors: Jeng Tzyy‐Wen , Talmon Yeshayahu , Chiu Wah 
Published: February 2005

AbstractA guillotine‐type quick freezing device and a bio‐hazard containment box have been designed, constructed, and used to prepare vitrifiedhydrated specimens of viruses in their native environment. Special design considerations include the preservation of the specimen in its natural state in vitrified ice, prevention of virus aerosols escape, and control of the potentially explosive air‐coolant vapor mixtures.
Dynamic hydration effects in an electron microscope cold stage
Authors: Lamvik Michael K. , Davilla Scott D. 
Published: February 2005

AbstractWater can be a substantial proportion of the residual gas in modern electron microscopes even when frozen hydrated specimens are not used. During measurements of the mass thickness of thin collodion film specimens at low temperatures, it was found that a volatile surface layer (condensed water) modified the apparent rate of mass loss induced by radiation exposure. Mass loss can be enhanced by the presence of water (specimen “etching”), or mass loss can be masked by the dynamic adsorption of water to the specimen surface. The microscope or the grid can be a secondary source of the water; even with cold anticontaminator plates in the vicinity of the specimen, water can be desorbed by x‐rays or backscattered electrons. In one typical situation, the mass loss rate appears reduced (due to water adsorption), but the ultimate damage is greater (due to etching). These results illustrate that care must be taken in interpreting mass thickness measurements made in the presence of water and that the lowest stage temperature does not necessarily produce the best observation conditions for all specimens.
Artifacts introduced by ion milling in Al‐Li‐Cu alloys
Authors: Singh A. K. , Imam M. A. , Sadananda K. 
Published: February 2005

AbstractIon milling is commonly used to prepare specimens for observation under transmission electron microscope (TEM). This technique sometimes introduces artifacts in specimens contributing to misleading interpretation of TEM results as observed in the present investigation of Al‐Li‐Cu alloys. This type of alloy, in general, contains several kinds of precipitates, namely δ′ T1, and θ′. It is found that ion milling even for a short time produces drastic changes in the precipitate characterics as compared to standard electropolishing methods of specimen preparation for TEM. Careful analysis of selected area diffraction patterns and micrographs shows that after ion milling δ′ precipitates are very irregular, whereas other precipitates coarsen and they are surrounded by misfit dislocations. In situ hot‐stage TEM experiments were performed to relate the microstructure to that observed in the ion‐milled specimen. Results and causes of ion milling effects on the microstructure are discussed in relation to standard electropolishing techniques and in situ hot‐stage experiment.
Fine structural cytology of the adenohypophysis in rat and man
Authors: Horvath Eva , Kovacs Kalman 
Published: February 2005

AbstractThe present review deals with the use of electron microscopy in the identification of pituitary cell types as well as the assessment of their functional state, in rat and man. Application of immunoelectron microscopy, especially immunogold techniques, utilizing multiple labeling in establishing differentiation and hormone content of cell types, is emphasized. Recent evidence of plurihormonality in various pituitary cell types indicates that the once axiomatic one cell‐one hormone theory is untenable and that the present perception of pituitary cell types and their function requires modification. Detection of hormonal and nonhormonal substances in pituitary cell types, not associated with their known endocrine function, suggests that hypophysial cells may have yet unknown roles, possibly in the realm of paracrine and autocrine regulation.
Junctional complexes and cell polarity in the urinary tubule
Authors: Brown Dennis , Orci Lelio 
Published: February 2005

AbstractIn this review, we demonstrate how differentiated membrane domains can be detected in epithelial cells using conventional light and electron microscopy, freeze‐fracture electron microscopy and the immunoand cytochemical detection of membrane components. Using specific examples from the kidney, we show how the polarized insertion of these components into either apical or basolateral plasma membrane regions on either side of the tight junction barrier is related to specific functions of principal and intercalated cells in the collecting duct. In addition, distinct basal and lateral membrane domains have been revealed in some cells that are maintained in the absence of a tight junctional barrier in the plane of the membrane. This suggests that other factors, possibly related to cytoskeletal elements, may be involved in the functional segregation of these membrane areas. We propose that epithelial cell plasma membranes should be subdivided into apical, lateral and basal regions, and that the term “basolateral” may be an oversimplification.
Relationship between structure and function in renal proximal tubule
Authors: Welling Larry W. , Welling Dan J. 
Published: February 2005

AbstractEpithelia which support large transepithelial fluid movements are generally found to have histologic specializations which increase the surface areas of the cell membranes across which flows occur. A relationship between structure and function seems obvious in those cases. On the other hand, the area increasing specializations may also result in complicated shapes for the cells and their adjacent intercellular channels. In this paper we review the means for examining cell shape by quantitative stereologic techniques and the results obtained for the epithelium of the proximal renal tubule. We conclude that cell shape not only is a critical ingredient in any structure‐function correlation for that tissue but also a “fingerprint” and a powerful tool with which one can predict and study epithelial absorptive flows and their driving forces.
Morphology of the minipig kidney
Authors: Dobyan Dennis C. , Bulger Ruth Ellen 
Published: February 2005

AbstractThe minipig has a multilobar kidney with a wide cortex and short papilla. The vascular bundles are of a simple type. Although short and long looped nephrons are both present, the short looped kind predominates. The minipig has many morphological similarities to dog and human kidneys. One particularly unique feature of the minipig papillary collecting duct cells, however, is the presence of electron‐dense granules in the basal cytoplasm which appear to be secreted into the lateral intercellular spaces, perhaps forming a water‐tight seal in a manner analogous to membrane‐coating granules found in the epidermis of skin.
Ultrastructural investigation of renal biopsies: A discussion of artifacts and special methodology
Authors: Olsen T. Steen , Racusen Lorraine C. , Solez Kim 
Published: February 2005

AbstractThe aim of this presentation is to draw attention to the problems inherent in evaluating the ultrastructure of percutaneous renal biopsies and to discuss some of the special techniques which are useful in this area. It is important to realize that the ultrastructure as it appears in this kind of material does not necessarily reflect conditions in vivo. Comparison with suitable reference material may, however, permit reliable conclusions in terms of pathological diagnosis and pathogenesis. It is advocated that purely qualitative methods, which until now have predominated in ultrastructure work with renal biopsies, be replaced by morphometry and semiquantitative methods when it is possible and practical to do so in any research situation.
Correlation averaging of a badly distorted lattice: The surface protein of Pyrodictium occultum
Authors: Hegerl Reiner , Baumeister Wolfgang 
Published: February 2005

AbstractThe 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.
Volume determination of TEM specimens containing particles or precipitates
Authors: Hare Thomas M. , Russ John C. , Lane Jay E. 
Published: February 2005

AbstractThe volume of thin foil specimens, which contain precipitate or other particles, viewed in the TEM is needed to determine particle density and spacing. It can be determined from the locations of the particles, measured using stereo pairs. A calculation that determines the volume between planes (not necessarily parallel or horizontal) that enclose the points is described. These planes will systematically underestimate the actual surface spacing and hence the volume, but a simple correction factor based on the number of points used in the fit can be used to estimate the actual volume. The method is tested, and its accuracy is evaluated using simulated data and applied to precipitate particles in creep‐tested silicon carbide.
Controlled vascular corrosion casting of the rabbit eye
Authors: Fahrenbach W. H. , Bacon D. R. , Morrison J. C. , Van Buskirk E. M. 
Published: February 2005

AbstractWe have refined the technique of vascular corrosion casting with methacrylate to permit the reproduction of physiological states of vascular tone and to produce sturdy castings of ocular microvasculature. The method entails careful maintenance of homeostasis up to the moment of plastic perfusion, avoidance of vascular rinsing or fixation with the attendant anoxia, reduction of the viscosity of the casting resin without impairing the properties of the resultant polymer, addition of a cross‐linking agent to increase the strength of the plastic, and injection at physiological temperature and pressure. This casting regimen reproduces the normal anatomical conditions of blood vessels and can be used to demonstrate altered conditions of vascular tone. In all instances, the second, untouched eye serves as a control for unilateral manipulations. Special problems of replicating the ocular vasculature are related to the intraocular pressure, which opposes the vascular perfusion pressure and constitutes an impediment to perfusion.
An accurate temperature monitoring device for balzers rotary cold tables
Authors: Barry Vanwinkle W. , Graham William F. 
Published: February 2005

AbstractIn the Balzers rotary cold table, the recording thermocouple is located 45 mm below the specimen stage. As a result, there is inconsistency between the temperature indicated by the thermocouple gauge and the actual temperature of the specimen carrier. This inconsistency is most notable and can lead to problems when the cold table temperature is changed, such as during the procedure when fracturing at one temperature is followed by etching at a higher temperature.In this article, we describe modifications to the Balzers rotary cold table that permit the constant measurement of actual specimen temperature in the stationary, off, and rotating positions. The changes involve the use of a miniature temperature‐sensing diode (TFD‐Omega), mounted on the cradle that accepts standard counterflow, rapid‐loading specimen stages.