bluuebunny/crossref_metadata_2025 huggingface dataset:
Extension of the “thin-crystal” condition by small crystal tilts: Why HREM images of SiC polytypes always look tilted
Authors: O'Keefe Michael A. , Radmilovic Velimir
Published: June 2020

Both experimental and simulated high-resolution electron microscope images of silicon carbide polytypes commonly exhibit symmetry changes in thicker crystal regions compared to the perfect (projected) space group symmetry of images from thin crystals. However, the changes predicted by simulation, and those found experimentally, are quite different.

High-resolution transmission electron microscope images of silicon carbide polytypes were obtained with the JEOL ARM-1000 high-resolution electron microscope in the course of an investigation into a series of metal matrix composites. Like all HRTEM images of silicon carbide, these images failed to show the correct symmetry in the thicker parts of the specimen. Changes in image symmetry as crystal thickness is increased also occur when images of silicon carbide are simulated; for example, Smith and O'Keefe simulated images of polytypes of silicon carbide for crystals oriented so that the electron beam was precisely along the <1210> direction, and found marked departure from thin-crystal symmetry at thicknesses of the order of 150Å for an electron energy of 500keV. However, the lack of symmetry in their simulated images appears to be due to the presence of many second-order terms contributing to the intensity spectra of the thick-crystal images, whereas the symmetry changes in experimental images from thicker crystals are usually of the form that preserves the thin-crystal-like contrast for one set of “twin” spots, yet smears out the contrast of the other. A typical example of this latter effect can be seen in the image of the 6H variant of SiC shown in figure 1.
Interpreting HVEM of muscle-cell impulse networks
Authors: DeCosta Paul , Cho Kyugon , Shemlon Stephen , Jun Heesung , Dunn Stanley M.
Published: June 2020

Introduction: The analysis and interpretation of electron micrographs of cells and tissues, often requires the accurate extraction of structural networks, which either provide immediate 2D or 3D information, or from which the desired information can be inferred. The images of these structures contain lines and/or curves whose orientation, lengths, and intersections characterize the overall network.

Some examples exist of studies that have been done in the analysis of networks of natural structures. In, Sebok and Roemer determine the complexity of nerve structures in an EM formed slide. Here the number of nodes that exist in the image describes how dense nerve fibers are in a particular region of the skin. Hildith proposes a network structural analysis algorithm for the automatic classification of chromosome spreads (type, relative size and orientation).
Determination of the strain field from an HREM image of a Si lomer dislocation
Authors: Tsai K.-H. , Schwartzman A. F. , Gallego R. , Ortiz M. , O'Keefe M. A. , Kim K.-S.
Published: June 2020

A novel approach to quantitative deformation characterization of high-resolution electron microscopy (HREM) defect images has been developed. The essential principle of this technique, called Computational Fourier Transform Deformation (CFTD) analysis, is to extract an accurate displacement field about a defect from its HREM image using Fourier transformation procedures. The methodology's unique feature is to digitize the defect image and compute the Moire pattern, from which the displacement field is obtained, without the need for an external reference lattice image, normally associated with the interference phenomena. Details of the image processing steps are described elsewhere. The motivation is that from this data, the displacement gradient can be calculated which yields much information on the experimental deformation mechanics of some solid undergoing a specific growth process or mechanical testing. One question that has arisen is whether different imaging conditions of the same defect affects the results of the CFTD analysis. We have studied this problem by analyzing the strain components of simulated images of a Lomer dislocation in Si and present our findings here.
The value of microscopy in research in ceramic and metallic materials
Authors: Loretto M H
Published: June 2020

This somewhat provocative symposium is scheduled to look at the (real) role of (transmission) electron microscopy in engineering materials. The very fact that the organisers have framed the title in this way, implies that there is a school of thought that questions the value of transmission electron microscopy (TEM) in areas other than in academic research - and perhaps even its value in academic research! Hence the aim of this paper is to assess whether TEM has made a contribution to the understanding, and thus to the successful application, of engineering materials or whether, as with so much physical metallurgy, it has simply confirmed what was already known to the practitioner for many years.
TEM study of grain boundary phase transformations in Cu-12 at PPM Bi polycrystals
Authors: Urdaneta E.C. , McMahon C. J. , Luzzi D. E.
Published: June 2020

Grain boundary segregation-induced faceting is being studied in Cu-12 at ppm Bi polycrystals as a model two-component alloy for grain boundary transformations. It has been demonstrated that Bi segregation is responsible for grain boundary faceting in copper and that this transformation is reversible. Previous Auger electron spectroscopy fracture surface analysis in Bi-doped Cu have shown that grain boundary faceting only occurs after the segregated Bi reaches a saturation concentration of about 1 monolayer.
Application of convergent-beam illumination methods to the study of lattice distortion across the interface
Authors: Liliental-Weber Zuzanna , Kaneyama T. , Terauchi M. , Tanaka M.
Published: June 2020

A high accuracy measurement of the lattice parameter can be obtained by x-ray diffraction. However, these methods have low spatial resolution and are limited by sample thickness. Therefore, for heterolayers much better information about local distortions near the interface can be obtained by electron microscopy using convergent-beam illumination. Large-angle convergent-beam electron diffraction (LACBED) patterns and convergent-beam imaging (CBIM) were applied to study of the lattice distortion across the interface of the GaAs epilayer grown on [001] GaAs substrate and the GaAs layer grown at 200°C (called the low-temperature (LT) layer). These LT GaAs layers are grown by molecular beam epitaxy from As oversaturation and are known to be As rich. Particle-induced x-ray studies reveal up to 1.5 % extra As. This excess As leads to the expansion of the lattice parameter up to 0.15% when measured by x-ray diffraction along the (004) reflection. From this study, it was expected that a cubic expansion of the lattice parameter would be equal in all three directions. However, TEM studies do not reveal the formation of dislocations at the interface, which would be expected taking into account the difference in the lattice parameter across the interface . Convergence beam illumination methods were applied to study in detail the strain, lattice parameter variation, and crystallographic distortion across the interface, since these methods have spatial resolution several orders of magnitude higher than x-ray diffraction. A CBED pattern taken in the substrate and in the layer with an incidence close to the [530] direction (exact orientation [0.869 0.495 0]) reveals the lattice parameter change, since the position of the cross of the 1113 and 1113 lines changes when an electron beam is placed in the substrate and the layer, respectively (Fig. la,b).
Deformation of a [001] Σ13 grain boundary in silicon
Authors: Sagalowicz Laurent , Clark William A. T.
Published: June 2020

The interaction between crystal lattice dislocations and grain boundaries has an important influence on the mechanical properties of polycrystalline materials. We describe here a study of the behavior of the Σ13, (510)1, 22.67°/[001] grain boundary in Si, deformed under symmetrical loading. The dissociation of crystal lattice dislocations which interact with this boundary during deformation is far more complicated than simple geometrical models predict.
Evidence for helical structures in poly(l-olefin sulfones) by TEM
Authors: Ruben George C. , Stockmayer W.H.
Published: June 2020

Advances in the techniques of TEM, including the preparation of ultrathin vertically shadowed platinum-carbon (Pt-C) replicas, have allowed the direct recognition of single-structural features, such as DNA , pectin helices or polysiloxane polymers. Here we report some observations on the chain conformations of serval poly (olefin sulfones). We find strong evidence for the presence of some helical conformations, which had been inferred for over a decade but could not so far be established by other methods.

Unusual conformational behavior of poly(olefin sulfones) was indicated over twenty-five years ago. Dilute solutions of several poly (1-olefin sulfones), [-CH2-CHR-S02-]X, in non-polar solvents exhibited unexpectedly strong low-frequency dielectric dispersion, with relaxation times typical of rigid tumbling or of the terminal normal mode. In contrast, polysulfones made from olefins with internal double bonds show no low-frequency dielectric loss. To explain these facts, we refer to the crucial experiments of Fawcett and Fee (1982), who prepared terpolymers of 1-hexene,
Microscopic versus process parameters in heavy-oil upgrading
Authors: Munoz V.A. , Mikula R.J. , Payette C. , Lam W.W.
Published: June 2020

The transformation of high molecular weight components present in heavy oils into useable liquid fuels requires their decomposition by means of a variety of processes. The low molecular weight species produced recombine under controlled conditions to generate synthetic fuels. However, an important fraction undergo further recombination into higher molecular weight components, leading to the formation of coke. The optical texture of the coke can be related to its originating components. Those with high sulfur and oxygen content tend to produce cokes with small optical texture or fine mosaic, whereas compounds with relatively high hydrogen content are likely to produce large optical texture or domains. In addition, the structure of the parent chemical components, planar or nonplanar, determines the isotropic or anisotropic character of the coke. Planar molecules have a tendency to align in an approximately parallel arrangement to initiate the formation of the nematic mesophase leading to the formation of anisotropic coke. Nonplanar highly alkylated compounds and/or those rich in polar groups form isotropic coke. The aliphatic branches produce steric hindrance to alignment, whereas the polar groups participate in cross-linking reactions.
Observation of ferroelectric domain boundaries in PZT(52/48) with TEM
Authors: Tsai Feng , Cowley J. M.
Published: June 2020

Lead zirconium titanates(PZT) are ferroelectric materials of considerable current interest because their potential for applications in memory devices and electrooptics has drawn the attention of industry. The performance of the devices made of PZT largely depends on the behaviors of ferroelectric domains and domain boundaries. TEM has been proved to be a very powerful tool in the study of ferroelectric domains and domain boundaries in ferroelectric materials. It is suggested that around the domain boundaries in BaTiO3 there is a distribution of lattice distortion and strain field. However, few references have been found on the study of ferroelectric domains and domain boundaries in PZT materials by TEM.
Quantitative measurement of surface roughness of TEM specimens
Authors: Zhang J. , Olsen K.H. , Schoessow K.A.
Published: June 2020

The thickness and the local thickness variation of thin film specimens are critical parameters for many types of AEM analysis. The local thickness variation of the thin film specimen can be estimated from the surface roughness of the specimen. TEM specimens of most materials, especially multi-phase materials, have rough surfaces as observed by secondary electron imaging. However, there is little quantitative assessment of the surface roughness because of the difficulty of specimen thickness measurement. In this study, surface roughness of TEM specimens prepared using chemical etching, electropolishing, and ion beam thinning was measured using a direct phase detecting optical interferometer. This interferometer gives a quantitative three dimensional map of the surface topography with a depth resolution of ∼0.7 nm by converting digitized light intensity at each point of a 1024×1024 array into the optical path difference using the three-measurement algorithm. The horizontal resolution of the interferometer (∼340 nm) is limited by optical diffraction and is poor by the TEM standard. The quantitative information obtained by the interferometer is complimentary to the secondary electron imaging in STEM or PEG SEM for characterizing TEM specimen surfaces.
Analyzing reactions of single mechanoenzyme molecules by light microscopy
Authors: Gelles Jeff
Published: June 2020

Mechanoenzymes are enzymes which use a chemical reaction to power directed movement along biological polymer. Such enzymes include the cytoskeletal motors (e.g., myosins, dyneins, and kinesins) as well as nucleic acid polymerases and helicases. A single catalytic turnover of a mechanoenzyme moves the enzyme molecule along the polymer a distance on the order of 10−9 m We have developed light microscope and digital image processing methods to detect and measure nanometer-scale motions driven by single mechanoenzyme molecules. These techniques enable one to monitor the occurrence of single reaction steps and to measure the lifetimes of reaction intermediates in individual enzyme molecules. This information can be used to elucidate reaction mechanisms and determine microscopic rate constants. Such an approach circumvents difficulties encountered in the use of traditional transient-state kinetics techniques to examine mechanoenzyme reaction mechanisms.
Immuno-electron microscopy at sub-nanometer resolution
Authors: Steven Alasdair C. , Newcomb William W. , Booy Frank P. , Brown Jay C. , Trus Benes L.
Published: June 2020

We have been studying the structure and assembly properties of the capsid of herpes simplex virus, type 1 (HSV-1), whose icosahedral shell (T=16) is ∽ 125 nm in diameter, has a mass of ∽ 200 MDa, and is composed of at least six protein species, ranging from 12 kDa to 149 kDa per monomer. To this end, the structures of empty and full purified capsids have been visualized in three-dimensional reconstructions from cryo-electron micrographs, at a resolution of ∽ 3.5 nm. With the intent of identifying specific structural features of the capsid in terms of particular proteins, or particular segments of these proteins, we have begun to explore the potentialities of cryo-reconstructions of capsids decorated with monoclonal antibodies.

B-capsids were purified from BHK cells infected with the MP strain of HSV-1. Some material was analyzed directly by cryo-electron microscopy and image reconstruction as described. Other samples were incubated with approximately equimolar amounts of a monoclonal antibody (8F5) raised against purified VP5 (the major capsid protein, 149 kDa). The resulting precipitate was then washed with buffer to flush out unbound antibodies, and then analyzed in the same way, i.e. by observation in a Philips EM400T equipped with a Gatan 626 cryo-holder. The specificity of Mab.8F5 for VP5 was confirmed by an ELISA with purified VP5.
Distribution and function of non-histone proteins in human chromosomes
Authors: Earnshaw W.C. , Cooke C.A.
Published: June 2020

The role of non-histone proteins in the structure and movements of mitotic chromosomes remains poorly understood. We describe here experiments aimed at characterization of the distribution of two very different classes of these proteins. The first is composed of integral components of the centromere (or primary constriction). The second class consists of proteins that we have termed “chromosome passenger proteins”. These proteins are chromosomal during most of the cell cycle, but appear to be associated with the cytoskeleton during anaphase and telophase.

The centromere regions of chromosomes perform three essential functions in mitosis. (1) They form the site of attachment of the chromosomes to the mitotic spindle. (2) They contain the mechanochemical motor molecules that are responsible for the movements of the chromosomes along microtubules. (3) They regulate the pairing of sister chromatids during mitosis. The first two of these mitotic functions are properties of a disk-shaped structural specialization, the kinetochore, which is located at the surface of the centromeric heterochromatin.
The effect of cytoskeletal protein mutations on cell motility and morphogenesis
Authors: Knecht David A.
Published: June 2020

The cortical cytoskeleton of eukaryotic cells is composed of actin filaments and a variety of associated proteins. The polymerization, depolymerization, cross-linking and bundling of these filaments, are presumed to be intimately involved in such processes as cell motility, cell adhesion and cell shape. In developing systems, all of these processes are involved in the morphogenetic mechanisms that shape tissues, organs and organisms.

We are investigating the complex interactions among cytoskeletal proteins using the simple eukaryotic amoebae, Dictyostelium discoideum. Our approach is to determine the function of the components of the cytoskeleton by creating mutants lacking particular proteins, or containing specific alterations in these proteins. Mutants lacking myosin heavy chain have been created using antisense RNA and homologous gene targetting. These cells have alterations in their shape and movement, and are incapable of accomplishing normal morphogenesis. Another cytoskeletal protein is ABP-120, which is capable of cross-linking actin filaments into orthogonal arrays, leading to the formation of an actin gel in vitro. ABP-120 is found in newly formed pseudopods extended during the chemotactic respose to extracellular cAMP. Mutants lacking this protein have been created by disruption of the chromosomal gene with a transformation vector. These cells are not as dramatically affected as the myosin mutants, but have clear alterations in their motility and in the pathway of responses in the cytoskeleton that correlate with the expected function of this protein. Mutations in several other cytoskeletal genes are currently being constructed.
Cisplatin-induced changes in the adrenal of the rat
Authors: Miller Casey M. , Aggarwal Surinder K.
Published: June 2020

Cisplatin (CDDP) is one of the most valuable antineoplastic drugs available for the treatment of testicular, ovarian, lung, head and neck cancers. However, the drug has severe toxic side effects of which nephrotoxicity and gastrointestinal toxicity are the major dose limiting factors. CDDP causes hypocalcemia and hypomagnesemia. Hypocalcemia has been demonstrated to effect the parathyroid gland and the neurohypophysis secretions, which in turn control the stomach smooth muscle contractility and the kidney function. In rats it induces stomach bloating and ulceration. Injections (i.v) of calcium have been demonstrated to prevent stomach bloating, ulceration and preserve normal kidney function[19]. Present is an effort to study the effect of CDDP on adrenal gland as another endocrine gland.
Morphometric estimation of viral burden in cell culture material by TEM
Authors: Bierley S.T. , Monticello T.M. , Morgan E.M. , Leininger J.R.
Published: June 2020

A major concern in the manufacture of cell culture-derived biotechnology products is the contamination of the cultures by potentially pathogenic agents such as retroviruses. Cell lines may have retroviral particles visible by TEM even when viral burden can not be demonstrated by infectivity assays or reverse transcriptase activity. The supernatant of the post-production cell cultures, therefore, must be evaluated by TEM for viral burden. An important question, however, is how to establish a quantitative viral load estimate for the evaluation of a purification process. The FDA recommends that a purification process for viral contaminants remove or inactivate 3-5 logs over the estimated viral burden.
Immunocytochemical detection of hepatic carbohydrate metabolic enzymes: Improved resolution with polyethylene glycol embedding and visio-bond semithin sections
Authors: Gao Kuixiong , Morris Randal E. , Giffin Bruce F. , Cardell Robert R.
Published: June 2020

Several enzymes are involved in the regulation of anabolic and catabolic pathways of carbohydrate metabolism in liver parenchymal cells. The lobular distribution of glycogen synthase (GS), phosphoenolpyruvate carboxykinase (PEPCK) and glycogen phosphorylase (GP) was studied by immunocytochemistry using cryosections of normal fed and fasted rat liver. Since sections of tissue embedded in polyethylene glycol (PEG) show good morphological preservation and increased detectability for immunocytochemical localization of antigenic sites, and semithin sections of Visio-Bond (VB) embedded tissue provide higher resolution of cellular structure, we applied these techniques and immunogold-silver stain (IGSS) for a more accurate localization of hepatic carbohydrate metabolic enzymes.
In situ hybridization detection of gene expression for hepatic metabolic enzymes
Authors: Cardell Robert R. , Davis Betty B. , Drake Richard L.
Published: June 2020

Key enzymes involved in gluconeogenesis and glycolysis are uniquely distributed within the liver lobule as shown, for example, by periportal hepatocytes having higher activities and quantities of the former and pericentral cells having higher activities and quantities of the latter enzymes. In this report we describe changes in the patterns of mRNA for a key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), in normal rats and diabetic rats with/without insulin treatment.

A 1.0 kb cDNA for rat PEPCK was subcloned into pGEM-3Z. 32P-labeled antisense and sense (control) RNA probes were produced and used for Northern blot analysis which showed that the antisense probe recognized a 2.8 kb mRNA in rat liver which corresponds to the PEPCK mRNA. The sense probe showed no affinity for mRNA from rat liver, lung or colon. 35S-labeIed antisense and sense RNA probes were prepared for in situ hybridization. These were degraded to an average length of 100-200 bases by alkaline hydrolysis. Six to 10 μm paraffin and frozen sections of rat liver were mounted on Tespa treated slides and were post-fixed in 4% paraformaldehyde in PBS for 20 min, treated with 20 μg/ml proteinase K, and further fixed in 4% paraformaldehyde. The sections were treated with acetic anhydride, dehydrated and air dried prior to hybridization. The 35S-UTP labeled RNA probes were dissolved at a final concentration of 1.0 x 105 cpm/μl in a hybridization solution with 50% formamide and used to hybridize each section at 55°C overnight under glass cloverslips. The slides were washed at a high stringency and treated with RNase A. After rinsing, the slides were dehydrated and air dried before autoradiography using Ilford K5 nuclear track emulsion. Some sections were stained in 0.02% toluidine blue and others were mounted unstained for image analysis.
Cuticular penetration ofSesbania exaltataSTEM tissue by penetration pegs from appressoria of the plant pathogenic fungus:Colletotrichum truncatum
Authors: Paul R. N. , Egley G. H.
Published: June 2020

Colletotrichum truncatumis a potentially useful pathogen for the biocontrol of the weedSesbania exaltata[(Raf.) Cory]. Information on the infection process is important in optimizing the use of this pathogen as a mycoherbicide. Successful infection of a host species depends upon the fungus’ ability to penetrate the plant’s defenses. Some fungi bypass the host plant cuticle by invading through stomates or other openings on the epithelial surface.Colletotrichumis capable of breaching the cuticle by means of a penetration peg1produced from an appressorium. We investigated this process by examiningS. exaltatastem tissue 24h after inoculation.
HREM of superstructures in high-temperature superconductors
Authors: Marks L. D. , Tsurata C. , Theil J. , Poeppelmieir K.
Published: June 2020

Fairly substantial interest has been aroused recently in the new wave of high temperature superconductors. The first such material discovered, La1.83Sr.17CuO4, has been reported to have a body centered tetragonal structure with a=b=.38 nm and an elongated c=1.3 nm. we have used HREM and electron diffraction on a new Hitachi H-9000 microscope at Northwestern (Cs=.9 mm, 300 kV) to analyse the structure of this material. In addition to phases which correspond to the reported structure, we have also observed phases with rather clear superstructures which correspond to a quadrupling of the unit cell, for instance Figures 1 and 2.

An additional point of interest is that the material showed no indication of losing oxygen by DIET processes, despite observation of the same crystal for more than 10 hrs.
Interactive simulation of high-resolution electron micrographs
Authors: Kilaas Roar
Published: June 2020

Only a few years ago image simulation of HRTEM images were mostly carried out as low priority jobs on large mainframe computers with images available the next day as overprinted characters on computer paper. Today the same calculation can be carried out on a dedicated workstation in a matter of minutes with output on high resolution video monitors. This improvement in computer hardware has produced a shift from software primarily designed to run as batch jobs to interactive software that allows instant changes to both the atomic model and microscope parameters. In these near “real time” calculations the user interface becomes an important part of the software, since setting up the conditions for the calculation may take longer than the calculation itself.

In an attempt to create a truly interactive environment for simulation of HRTEM images, a new set of programs has been written at the National Center for Electron Microscopy (NCEM) at Berkeley.
Interphase interfaces in Nio-Zro2 (Cao) eutectic
Authors: Dravid Vinayak P.
Published: June 2020

Directionally solidified eutectics (DSEs) of oxide-oxide components offer many advantages over the conventional bi-crystal specimens for interface studies. The two phases in the DSE grow in unison with a well-defined orientation relationship and offer a wide spatial range of crystallographically similar interfaces. A preliminary investigation has been carried out to characterize interphase interfaces in the DSE system NiO-ZrO2 (CaO). The transverse section of the DSE consists of alternate lamellae of cubic NiO and CaO-stabilized cubic ZrO2, as shown in Figure 1. The orientation relationship (OR) from the selected area diffraction (SAD) pattern (Figure 2) was observed to be:

growth direction //[011]NiO//[001]ZrO2 and
interfacial plane //(111)NiO//(100)Zr02

The above OR was predominant in the bulk material and is consistent with x-ray results, but at lamellar termination/faults the OR was observed to be:
Stacking-fault tetrahedra in ion-implanted III-V compounds
Authors: De Cooman B.C. , McKeman S. , Carter C.B.
Published: June 2020

The implantation of heavy ions into GaAs for the purpose of obtaining a shallow n-type layer has been studied in detail, The results obtained by Rutherford Backscattering and high-resolution electron microscopy show that the surface layer is amorphized during implantation and that the solid-phase epitactic regrowth gives rise to a surface layer containing a large density of microtwins and stacking faults. No other defects have been reported other than interstitial-type dislocation loops in the implanted material, despite the fact that P-implants in Si had shown that a high density of stacking-fault tetrahedra (SFT) were formed after annealing. The present contribution reviews the major findings obtained during the first observation of SFT in Ga1-xAlxAs/GaAs (x=0.3) superlattices and Ga1-xAlxAs (x=0.3) epilayers grown on (001) GaAs. The material was grown by molecular-beam epitaxy (MBE). The ion energy used was 175kV, the dose was 1015cm-2and the Se ions were implanted at room-temperature The specimens were examined before and after a 4 hour anneal at 660°C.
Influence of Zro2 on the microstructure of BaTiO3
Authors: Armstrong T.R. , Buchanan R.C.
Published: June 2020

Ceramic capacitor materials are typically based on ferroelectric perovskite structures such as BaTiO3. The desirable electrical properties can be improved by isovalent additions of cations such as Ca2+ for Ba2+ and Zr4+ for Ti4+ These additions are aliostructural with the BaTiOg perovskite lattice and create a wide range of solid solutions and property modifications. Additions of ZrO2 both decrease and broaden the dielectric constant peak at the Curie temperature and have been shown to increase the lattice parameter of BaTiO3 resulting in a decrease in the c/a ratio. ZrO2 is believed to affect the dielectric properties by residing at the grain boundaries and suppressing grain growth. The induced strain, resulting from suppressed grain growth, stabilizes the dielectric constant by suppressing the displacive phase transformations and results in a pseudo-cubic structure. The objective of this investigation was to determine the effects of added ZrO2 on the microstructure and grain boundary of BaTiO3.
Cryoultramicrotomy and the cryofixation of polymers
Authors: Cieslinski R. C. , Marshall J. G.
Published: June 2020

The recent development of ductile polymer blends and emulsion polymers has necessitated the adaptation of cryogenic methods, frequently used in biomedical microscopy, to the study of bulk polymers.

The use of cryogenic methods offers the polymer microscopist some advantages over more conventional staining techniques. It is possible to retain morphology without distortion in ductile materials such as polyethylene, polypropylene, and blends with soft components. There is no chemical alteration of the material which is usually a requirement of electron diffraction energy dispersive spectrometry, and electron energy loss spectrometry, Preparation artifacts are generally minimal. Figure 1 shows butyl acrylate rubber/styrene acrylonitrile blend stained with a RuO4 solution. Although less contrast is achieved, the cryo-sections show that the staining solution has caused the rubber domains to expand in size (Fig. 2).
Histogenesis of alveolar cell carcinoma
Authors: Rybicka Krystyna
Published: June 2020

Alveolar cell carcinoma (ACC) is a lung neoplasm characterized by the presence of lamellar bodies specific for normal type 2 alveolar cells. Tumor histogenesis is uncertain. The present study indicates that ACC originates from dedifferentiation of hyperplastic type 2 alveolar cells rather than migration of bronchial stem cells into alveoli as suggested earlier.

An aliquot of human lung biopsy diagnosed as ACC was fixed in glutaraldehyde and osmium, treated with 1% aqueous uranyl acetate, and embedded in epoxy resin. Sections were stained for glycogen by periodic acid - thiosemicarbazide - silver proteinate, and post-stained by uranyl acetate and lead citrate.

The tumor contained morphologically distinct cell clusters. Each cluster consisted of identical cells. Differences between clusters resulted from synchronous alterations in lamellar bodies, mitochondria, glycosomes, and ribosomes. These alterations revealed distinct stages in cell differentiation classified here as follows: stage 1-hyperplastic cells (Fig.1), stage 2-dedifferentiating cells (Fig.2), stage 3-undifferentiated cells (Fig.3), stage 4-differentiating cells (Fig.4).
The allosteric switch between right- and left-handed flagellar filaments
Authors: Trachtenberg S. , DeRosier D. J.
Published: June 2020

The flagellum is the common bacterial organelle of motility; it consists of a basal body (rotary motor), a hook (universal joint), and a rigid helical filament (propellor). The filament is assembled from only one protein species — flagellin. Flagellins from different bacterial species differ in molecular weight (25-60 kD) and amino acid composition. However, structural studies show that a common underlying symmetry and design scheme are shared by filaments from various species and of apparently different morphologies. A similarity in the subunit structure is also evident from these studies. To function as a propellor, the helical assembly of flagellin monomers must further coil into a macrosconic helix; mutants with straight filaments are non motile. Moreover, the filament responds to changes in its environment, such as in pH, ionic strength, and mechanical forces, and can change its pitch and hand.
Trophoblast development of normal primate placenta: A morphometric study
Authors: Weberg A. , Kaufmann R. C. , Verhulst S. , Amankwah K. S.
Published: June 2020

Histological and ultrastructural changes in the morphological development of placentae at various gestational ages have been descriptive and qualitative. A few studies have applied morphometric techniques to quantify the developmental changes in the trophoblast layer and stromal constituents, including fetal vessels. The data from these studies are primarily based on light microscopic observations and were derived from midterm to older placentae. However, no distinction was made between vasculosyncytial membrane and other syncytial areas. The vasculosyncytial region of the developing placenta serves as a valuable indicator of some pathological conditions; therefore, a quantitative measure of the changes in these regions during development would be beneficial. Using placentae from early gestation to term and distinguishing between vasculosyncytial areas, the trophoblast layer was measured with morphometric techniques, and observed morphological changes were correlated with gestational age.
Parathyroid gland before and after cisplatin treatment
Authors: Aggarwal S.K. , Fadool J.M.
Published: June 2020

Cisplatin (CDDP) a potent antitumor agent suffers from severe toxic side effects with nephrotoxicity being the major dose-limiting factor, The primary mechanism of its action has been proposed to be through its cross-linking DNA strands. It has also been shown to inactivate various transport enzymes and induce hypocalcemia and hypomagnesemia that may be the underlying cause for some of its toxicities. The present is an effort to study its influence on the parathyroid gland for any hormonal changes that control calcium levels in the body.

Male Swiss Wistar rats (Crl: (WI) BR) weighing 200-300 g and of 60 days in age were injected (ip) with cisplatin (7mg/kg in normal saline). The controls received saline injections only. The animals were injected (iv) with calcium (0.5 ml of 10% calcium gluconate/day) and were killed by decapitation on day 1 through 5. Trunk blood was collected in heparinized tubes.
Immunogold labeling of CMP-KDO synthetase produced by recombinant E. Coli cells
Authors: Durum F. A. , Goldman R. G. , Bolling T. J. , Miller M. F.
Published: June 2020

CMP-KDO synthetase (CKS) is an enzyme which plays a key role in the synthesis of LPS, an outer membrane component unique to gram negative bacteria. CKS activates KDO to CMP-KDO for incorporation into LPS. The enzyme is normally present in low concentrations (0.02% of total cell protein) which makes it difficult to perform large scale isolation and purification. Recently, the gene for CKS from E. coli was cloned and various recombinant DNA constructs overproducing CKS several thousandfold (unpublished data) were derived. Interestingly, no cytoplasmic inclusions of overproduced CKS were observed by EM (Fig. 1) which is in contrast to other reports of large proteinaceous inclusion bodies in various overproducing recombinant strains. The present immunocytochemical study was undertaken to localize CKS in these cells.

Immune labeling conditions were first optimized using a previously described cell-free test system. Briefly, this involves soaking small blocks of polymerized bovine serum albumin in purified CKS antigen and subjecting them to various fixation, embedding and immunochemical conditions.
Designing high-resolution slow scan CCD-based TEM camera systems
Authors: Mancuso James F. , Maxwell William B. , Camp Russell E. , Ellisman Mark H.
Published: June 2020

The imaging requirements for 1000 line CCD camera systems include resolution, sensitivity, and field of view. In electronic camera systems these characteristics are determined primarily by the performance of the electro-optic interface. This component converts the electron image into a light image which is ultimately received by a camera sensor.

Light production in the interface occurs when high energy electrons strike a phosphor or scintillator. Resolution is limited by electron scattering and absorption. For a constant resolution, more energy deposition occurs in denser phosphors (Figure 1). In this respect, high density x-ray phosphors such as Gd2O2S are better than ZnS based cathode ray tube phosphors. Scintillating fiber optics can be used instead of a discrete phosphor layer. The resolution of scintillating fiber optics that are used in x-ray imaging exceed 20 1p/mm and can be made very large. An example of a digital TEM image using a scintillating fiber optic plate is shown in Figure 2.
Unattended automated elemental analysis of fibrous and non-fibrous inorganic particulates
Authors: Sheehan CE , Emerson RJ , Mastovich JM , Singh JK , Ross JS
Published: June 2020

Automated identification and analysis of inorganic particulates by Scanning Electron Microscopy (SEM) and energy dispersive x-ray analysis (EDX) has been established for many years. Our laboratory has developed and refined a procedure for unattended automated analysis which significantly increases the number of particles analyzed per hour and dramatically decreases the analyst's time spent at the microscope.

The sample is analyzed in a JEOL JSM 6100 scanning electron microscope (JEOL, Inc, Peabody MA) integrated by Sesame (Fisons Instruments, Inc, San Carlos, CA) with a Kevex Quantum Delta Class energy dispersive x-ray spectrometer (Fisons Instruments, Inc, San Carlos, CA). Working within the software program Automated Image Analysis (AIA), our user-defined sequence of commands or procedure file is created. This procedure combines digital imaging and features analysis, x-ray analysis and integrated Sesame stage control.

Beginning with the field of choice, the procedure file is initiated by the operator, the image on the microscope is acquired onto the computer screen, a binary image is created, and features (particles) are processed (identified) followed by analysis of each particle for elemental composition.
Microprobe analysis in clinical diagnosis
Authors: Shelburne J. D. , Roggli V. L. , Ingram P.
Published: June 2020

In addition to providing an important and unique analytical tool for medical and biological research, the findings from microprobe analysis often have diagnostic, therapeutic and/or legal significance for patients. References cited below provide a guide to this expanding literature.

Of the various types of microanalysis available, electron probe microanalysis is at present the most useful for clinical studies. Backscattered electron imaging is used as a guide to identify relatively high atomic number inclusions in the relatively low atomic number background of human tissue. Correlation of the backscattered electron images with the images obtained through conventional light microscopy is an absolutely critical aspect of these studies. For better or for worse, the “gold standard” of current medical practice remains the light microscopic examination of conventionally stained (e.g. hematoxylin and eosin) paraffin sections. Accordingly, it is necessary that the microprobe data can ultimately be ascribed to particular features of the conventional images well understood by pathologists.
Valence electron spectroscopy of inhomogeneous media
Authors: Howie A. , McComb D.W.
Published: June 2020

The bulk loss function Im(-l/ε (ω)), a well established tool for the interpretation of valence loss spectra, is being progressively adapted to the wide variety of inhomogeneous samples of interest to the electron microscopist. Proportionality between n, the local valence electron density, and ε-1 (Sellmeyer's equation) has sometimes been assumed but may not be valid even in homogeneous samples. Figs. 1 and 2 show the experimentally measured bulk loss functions for three pure silicates of different specific gravity ρ - quartz (ρ = 2.66), coesite (ρ = 2.93) and a zeolite (ρ = 1.79). Clearly, despite the substantial differences in density, the shift of the prominent loss peak is very small and far less than that predicted by scaling e for quartz with Sellmeyer's equation or even the somewhat smaller shift given by the Clausius-Mossotti (CM) relation which assumes proportionality between n (or ρ in this case) and (ε - 1)/(ε + 2). Both theories overestimate the rise in the peak height for coesite and underestimate the increase at high energies.
Structure determination using convergent-beam electron diffraction
Authors: Steeds J W , Vincent R
Published: June 2020

There are many different approaches in quantitative electron diffraction which are being vigorously pursued at present. The approach we adopt is based on the insights provided by the Bloch-wave formulation of dynamical electron diffraction theory into the physics of dynamical scattering. This insight is used to select diffraction situations where a pseudo-kinematical approximation may be made. A forwards route is then possible directly from the experimental observations to the structural implications. This contrasts with the model-building, multi-parameter fitting procedures used in many other approaches where a problem of uniqueness inevitably arises.

Because the pseudo-kinematical approach ignores many of the detailed dynamical interactions which occur locally over small angular ranges we do not attempt to make accurate measurements, and wherever possible average (visually at least) along Bragg lines to eliminate local perturbations. In a sense the work resembles early X-ray crystallography where reflections were put in one of six or so classes from very weak to very strong.
Electron spectroscopic imaging and diffraction: applications II materials science
Authors: Mayer J.
Published: June 2020

With imaging energy filters becoming commercially available in transmission electron microscopy many of the limitations of conventional TEM instruments can be overcome. Energy filtered images of diffraction patterns can now be recorded without scanning using efficient parallel (2-dimensional detection. We have evaluated a prototype of the Zeiss EM 912 Omega, the first commercially available electron microscope with integrated imaging Omega energy filter. Combining the capabilities of the imaging spectrometer with the principal operation modes of a TEM gives access to many new qualitative and quantitative techniques in electron microscopy. The basis for all of them is that the filter selecte electrons within a certain energy loss range ΔE1 <ΔE < ΔE2 and images their contribution to an image (electron spectroscopic imaging, ESI) or a diffraction pattern (electron spectroscopic diffraction, ESD) In many applications the filter is only used to remove the inelastically scattered electrons (elastic or zero loss filtering). Furthermore, the electron energy loss spectrum can be magnified and recorded with serial or parallel detection.
The current state of spectrum imaging
Authors: Hunt J. A. , Williams D. B.
Published: June 2020

Traditionally, S(T)EM spectroscopic imaging involved processing the spectral data for an image pixel during image acquisition, discarding the original spectral data and saving only the results of the processing. This form of imaging proved satisfactory for many years but the limitations imposed by processing data “on-the-fly” were apparent. The advent of commercially available parallel detection EELS (PEELS) and inexpensive mass storage in excess of 100Mb allowed the concept of EELS spectrum imaging to be implemented. The majority of spectrum imaging work has used PEELS, although energy-dispersive x-ray spectroscopy (EDXS) has also been used. Spectrum imaging differs from previous imaging implementations because all the collected spectroscopic data are stored and processed post facto. A spectrum image as originally defined is a 3D data object (2 spatial & 1 energy dimension) and is generally much larger than a standard digital image because 1000-4000 spectral values are stored per spectrum image pixel. Instrumental limitations currently limit practical EELS spectrum images to around 128×128 pixels instead of the 1024×1024 to 2048×2048 pixels typical of normal digital microscopy images.
Crystal orientation effects in the x-ray microanalysis of spinels
Authors: Anderson Ian M.
Published: June 2020

Compounds with the crystal structure of the mineral spinel (MgAl2O4) provide an interesting test case for the quantitative x-ray microanalysis of crystals. The cations occupy more than one crystallographic site, two thirds occupying the octahedral 16d interstices and one third occupying the tetrahedral 8a interstices of the oxygen anion sublattice (Fd3m). Under dynamical electron diffraction conditions in the AEM, the standing-wave electron intensity on the two sublattices may differ considerably, in turn yielding proportionally different x-ray count rates from the cations on these sublattices. This effect has been exploited to determine the sites of impurity atoms in spinels using the ALCHEMI technique. The strong crystal orientation effect obstructs the accurate determination of the composition of spinels using x-ray microanalysis, however. In the system NiO-TiO2, which is the subject of ongoing investigation, a second phase is always found finely dispersed within the metastable spinel phase. The AEM is the only instrument which provides the high spatial resolution necessary to probe the composition.
Electron energy-loss near-edge structure in silicate minerals
Authors: McComb D W , Payne R S , Hansen P L , Brydson R
Published: June 2020

Electron energy-loss near-edge structure (ELNES) is an effective probe of the local geometrical and electronic environment around particular atomic species in the solid state. Energy-loss spectra from several silicate minerals were mostly acquired using a VG HB501 STEM fitted with a parallel detector. Typically a collection angle of ≈8mrad was used, and an energy resolution of ≈0.5eV was achieved.

Other authors have indicated that the ELNES of the Si L2,3-edge in α-quartz is dominated by the local environment of the silicon atom i.e. the SiO4 tetrahedron. On this basis, and from results on other minerals, the concept of a coordination fingerprint for certain atoms in minerals has been proposed. The concept is useful in some cases, illustrated here using results from a study of the Al2SiO5 polymorphs (Fig.l). The Al L2,3-edge of kyanite, which contains only 6-coordinate Al, is easily distinguished from andalusite (5- & 6-coordinate Al) and sillimanite (4- & 6-coordinate Al). At the Al K-edge even the latter two samples exhibit differences; with careful processing, the fingerprint for 4-, 5- and 6-coordinate aluminium may be obtained.