bluuebunny/crossref_metadata_2025 huggingface dataset:
A combined AEM/APFIM characterization of alloy X-750
Authors: Burke M.G. , Miller M.K.
Published: June 2020

In the development of advanced alloys for power system applications, the primary emphasis is placed on attaining specific mechanical properties with resistance to environmental attack. An important part of alloy development is the detailed characterization of the microstructure, because it is the composition, size and morphology of the microstructural features that define the mechanical properties of the material. The good mechanical properties of Ni-base superalloys are a result of the formation of fine coherent precipitates. In addition, other coarser phases may form which can degrade the properties of the alloys. Analytical electron microscopy (AEM) provides important information concerning the type and distribution of the phases in the alloys, but quantitative microchemical analysis of the ultra-fine precipitates is not readily obtainable with conventional AEM techniques. The high spatial resolution of the atom probe field-ion microscope (APFIM) makes this technique ideally suited to the analysis of the ultra-fine precipitates and surrounding matrix. The analysis of the matrix is particularly important in predicting the subsequent ageing response of the alloy, as previously shown in a detailed AEM/APFIM examination of Alloy 718. In this paper, a combined AEM/APFIM study of precipitation in Alloy X-750 is presented.
Evolution of intrinsic coercivity in Pt-Co-B alloys
Authors: Qiu N.
Published: June 2020

New permanent magnets based on Pt-Co-B ternary alloys have been developed by rapidly solidification with subsequent heat treatments. The coercivity achieved in the Pt-Co-B ternary alloys is more than double the highest coercivity observed in the Pt-Co binary system. Good thermal stability of the coercivity produced by annealing provides a basis for consolidation processes such as hot isotropic pressing to produce bulk magnets from the rapidly solidified Pt-Co-B materials. Increased coercivity coupled with special properties such as high Curie temperature, corrosion resistance and ductility may expand the potential applications for these alloys. The evolution of microstructure and its effect on coercivity from annealing the as-quenched materials are investigated to understand the magnetic hardening mechanism and optimize the magnetic properties.
Role of EM in interface science and engineering
Authors: Thomas Gareth
Published: June 2020

The world of materials is a world of interfaces. Indeed many technologically significant materials have properties both physical and mechanical which are determined by the structure, composition, and bonding of the interfaces within these materials. Thus, electron microscopy and microanalysis, with its high resolution and specificity of information, is one of the key methods needed for characterization. Imaging can be done by amplitude contrast but is limited by the factor g • R (where R is a displacement vector), or resolution in phase contrast, and in today's modern instruments atomic arrangements can be imaged directly, both in plan and cross-sectional views. Beautiful examples are now being published. However so far, few developments to utilize this information for materials design have been forthcoming. On the other hand, interface or intergranular phases are very important in many metallurgical and ceramic systems. In fact many materials are composites of one kind or another and composites involving intergranular phases are an important group of such materials.
The mensuration of interfaces
Authors: Stobbs W.M.
Published: June 2020

I do not have access to the abstracts of the first meeting of EMSA but at this, the 50th Anniversary meeting of the Electron Microscopy Society of America, I have an excuse to consider the historical origins of the approaches we take to the use of electron microscopy for the characterisation of materials. I have myself been actively involved in the use of TEM for the characterisation of heterogeneities for little more than half of that period. My own view is that it was between the 3rd International Meeting at London, and the 1956 Stockholm meeting, the first of the European series , that the foundations of the approaches we now take to the characterisation of a material using the TEM were laid down. (This was 10 years before I took dynamical theory to be etched in stone.) It was at the 1956 meeting that Menter showed lattice resolution images of sodium faujasite and Hirsch, Home and Whelan showed images of dislocations in the XlVth session on “metallography and other industrial applications”. I have always incidentally been delighted by the way the latter authors misinterpreted astonishingly clear thickness fringes in a beaten (”) foil of Al as being contrast due to “large strains”, an error which they corrected with admirable rapidity as the theory developed. At the London meeting the research described covered a broad range of approaches, including many that are only now being rediscovered as worth further effort: however such is the power of “the image” to persuade that the above two papers set trends which influence, perhaps too strongly, the approaches we take now. Menter was clear that the way the planes in his image tended to be curved was associated with the imaging conditions rather than with lattice strains, and yet it now seems to be common practice to assume that the dots in an “atomic resolution image” can faithfully represent the variations in atomic spacing at a localised defect. Even when the more reasonable approach is taken of matching the image details with a computed simulation for an assumed model, the non-uniqueness of the interpreted fit seems to be rather rarely appreciated. Hirsch et al., on the other hand, made a point of using their images to get numerical data on characteristics of the specimen they examined, such as its dislocation density, which would not be expected to be influenced by uncertainties in the contrast. Nonetheless the trends were set with microscope manufacturers producing higher and higher resolution microscopes, while the blind faith of the users in the image produced as being a near directly interpretable representation of reality seems to have increased rather than been generally questioned. But if we want to test structural models we need numbers and it is the analogue to digital conversion of the information in the image which is required.
Twin boundary structure in L10 alloys
Authors: Singh Abha , King A.H.
Published: June 2020

Ordered alloys have been of great interest in the last decades for their potential use as high temperature structural materials. The most commonly studied ordered alloys are Ni3 Al, with L12structure, and L1 0TiAl. Grain boundary fragility, however, is a major problem in the practical application of many ordered alloys, although it can be ameliorated in Ni3Al by boron doping. The problem calls for improved understanding of grain boundary structure in ordered alloys. Most studies so far have been done on alloys based on L12 and B2 structure. An investigation of twin boundary structure in L10 CuAu(I) has been carried out in the present work, by means of CTEM and computer image matching techniques.

The twins in the present study are order twins; i.e. they are formed upon ordering, when a cubic to tetragonal phase transformation occurs. The lattice strains associated with the cubic-tetragonal transformation are accommodated by a repeated twinning structure which consists of alternating twins on parallel {101) planes, as observed by Pashley and Presland.
High resolution study of the structure of the Σ=5 [001] twist grain boundary in NiO
Authors: Lee J. L. , Sass S. L.
Published: June 2020

The existence of grain boundaries (GBs) in many advanced ceramics can significantly alter their performance, rendering the study of GB structure an essential part of understanding ceramic properties on a fundamental level. Furthermore, the debate regarding the stability of [001] twist GBs in rocksalt-structured oxides provides the impetus for comparing experimental observations of the Σ=5 [001] twist GB structure in NiO with the stable GB structure calculated by Tasker and Duffy (Fig. 1). The Tasker and Duffy structure was obtained by introducing a Schottky defect in each of the GB unit cells, resulting in a 20% decrease in atomic density at the GB. High resolution TEM (HRTEM) employing Fresnel fringe and lattice imaging techniques (Fig. 2) supplemented with image simulations of six possible configurations for the NiO Σ=5 [001] twist GB structure using the TEMPAS program (Fig. 3) were the primary experimental methods used in an attempt to detect this reduced atomic density in NiO Σ=5 [001] twist GBs manufactured by a modified Schober-Balluffi method. Since the Fresnel fringe technique consists of a change in Fresnel fringe contrast with defocus due to a change in mean inner potential at the GB, it becomes necessary to consider the contribution of the various causes of a change in mean inner potential to the resulting contrast. These causes include: (i) a change in atomic density or a change in atomic structure at the GB, (ii) the existence of a space charge at the GB, (iii) the existence of a thin amorphous film at the GB, (iv) the presence of impurities at the GB or a change in composition across the GB, and (v) GB grooving. The contribution of a GB space charge to the change in mean inner potential at the GB is assumed to be small, given that the space charge associated with with a GB in an ionic crystal is on the order of a few tenths of a volt, whereas the mean inner potential at the GB is on the order of 15 - 20 V. An attempt to address the impurity and grooving issues was made by performing EDS and EELS across the GB in an ultra-high vacuum, high resolution STEM.
Crystallography and structure of (0001)α-Al2O3//(110)Pd interface
Authors: Cosandey F. , Lu P.
Published: June 2020

A fundamental understanding of the behavior of metal/oxide composites requires a detailed knowledge of interface properties and HREM studies have provided important information on interfacial structure and composition. The aim of the present investigation was to study the equilibrium shape, orientation relationship and atomic structure of low energy plane orientations in the Pd/α-Al2O3 system. Metal/Oxide interfaces were produced by first preparation of Pd-3wt%Al alloys followed by oxidation in air at 1000 °C for 48 hours leading to the formation of A13O3 particles. For the TEM observations we used an ISI-002B high resolution microscope with a resolution limit of ∼0.18 nm at 200 KeV.
Twinning dislocations and structural transition of twin boundary in YBa2Cu3O7-δ
Authors: Zhu Yimei , Suenaga M.
Published: June 2020

HREM studies suggest that there are two types of twin boundaries in YBa2Cu307-δ. one with a lattice translation (∼d110) along the boundary for fully oxygenated samples, and the other without a lattice translation for oxygen-deficient ones. Originally, the displacement was attributed to observational phenomena caused by misalignment of the crystal. However, diffraction analysis and twin boundary fringe contrast analysis showed that the lattice translation at the boundary is an intrinsic property of the twin boundary in fully oxygenated YBa2(Cu0.98 M0.02)3O7-δ (M = Cu, Zn, and Ni, and δ∽0.0). To further understand the kinetics of twin boundary formation, we present additional observations on twinning dislocation and structural transition of the twin boundaries.
Microstructural issues in c-parallel YBa2Cu3O7-δ thin films
Authors: Streiffer S.K. , Lairson B.M. , Zielinski E.M. , Umezawa T. , Geballe T.H. , Bravman J.C.
Published: June 2020

Considerable effort has been directed at understanding the microstructures present in YBa2Cu3O7-δ films with the c-axis perpendicular to the plane of the substrate. This work has largely been driven by the high critical currents achieved in this particular film orientation. Although the critical currents are in general lower, the demonstration of high crystal quality, extremely smooth, dense films with their c-axis parallel to the plane of the substrate has opened the possibility of exploiting the highly anisotropic nature of YBa2Cu3O7-δ. To fully utilize such films, a thorough investigation of microstructural issues is as necessary for this film orientation as for the c-perpendicular case. We have used transmission electron microscopy and scanning force microscopy to examine c-parallel films grown on SrTiO3 and LaAlO3 substrates by single-target, off-axis magnetron sputtering. Films were deposited at block temperatures ranging from 600°C to 640°C, in atmospheres ranging from 30 millitorr oxygen and 40 millitorr argon to 60 millitorr oxygen and 90 millitorr argon. In an effort to improve superconducting properties while maintaining as smooth a surface as possible, films were also grown by a template method in which an initial nucleation layer was deposited at 625°C and the remainder of the film deposited at 700°C.
Attractive mode force microscopy of chiral liquid crystal surfaces
Authors: Terris B.D. , Twieg R. J. , Nguyen C. , Sigaud G. , Nguyen H. T.
Published: June 2020

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.

Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.
Characterization of oxide films formed on Inconel 600 and incoloy 800 during exposure to high-temperature water
Authors: Allem Rafik , L'Espérance Gilles , Gonzalez Francisco , Brennenstuhl Alex M. , Caron Mario
Published: June 2020

The structure and composition of oxide films may give an insight into the corrosion resistance of nickel alloys of the type used as tubing in nuclear steam generators. This paper describes the results of a preliminary analytical TEM study aimed at characterizing the surface films formed on Inconel 600 and Incoloy 800 during exposure to high temperature water (300°C).

Alloy coupons were exposed to water at pH 10. pH control was accomplished by additions of either sodium hydroxide or morpholine. Thin foils and extraction replicas were prepared to study the oxide films. Thin electron transparent sections through the oxide/metal interface region were produced using standard techniques. Quantification of the Energy Dispersive and Electron Energy Loss Spectroscopies (EDS and EELS) spectra was carried out using calibration kAB factors and calculated partial cross sections respectively. Identification of crystalline phases was achieved by Focused Beam Electron Diffraction (FBED).
Stress-induced structures on surfaces observed using Scanning Tunneling Microscopy and low-energy Electron Microscopy
Authors: Williams Ellen D. , Phaneuf R.J. , Bartelt N.C. , Swiech W. , Bauer E.
Published: June 2020

Elastic stresses play a well-known and important role in the structure of thin films during growth. However, elastic effects can also greatly influence surface morphology of the substrate. One source of this influence, as has long been recognized is the elastic interactions between steps on surfaces. More recently, Marchenko has shown that surface stress can stabilize finite-size structures in surfaces, such as facets. Traditionally surface morphologies such as steps and facets have been measured by low-energy electron diffraction. However, the more recent development of ultra-high vacuum compatible microscopic techniques such as scanning tunneling microscopy, reflection electron microscopy, and low-energy electron microscopy, now make it possible to image steps and facets directly to obtain information about sizes and size distributions. This information in turn makes it possible to test the influence of stress on surface morphology directly.
AEM of reaction-bonded SiC
Authors: Chowdhury K Das , Carpenter R. W. , Braue W.
Published: June 2020

Research on reaction-bonded SiC (RBSiC) is aimed at developing a reliable structural ceramic with improved mechanical properties. The starting materials for RBSiC were Si,C and α-SiC powder. The formation of the complex microstructure of RBSiC involves (i) solution of carbon in liquid silicon, (ii) nucleation and epitaxial growth of secondary β-SiC on the original α-SiC grains followed by (iii) β>α-SiC phase transformation of newly formed SiC. Due to their coherent nature, epitaxial SiC/SiC interfaces are considered to be segregation-free and “strong” with respect to their effect on the mechanical properties of RBSiC. But the “weak” Si/SiC interface limits its use in high temperature situations. However, few data exist on the structure and chemistry of these interfaces. Microanalytical results obtained by parallel EELS and HREM imaging are reported here.
Freeze-dried dispersions for automated SEM analysis of individual submicron airborne particulates
Authors: Katrinak Karen A. , Brekke David W. , Hurley John P.
Published: June 2020

Individual-particle analysis is well established as an alternative to bulk analysis of airborne particulates. It yields size and chemical data on a particle-by-particle basis, information that is critical in predicting the behavior of air pollutants. Individual-particle analysis is especially important for particles with diameter < 1 μm, because particles in this size range have a disproportionately large effect on atmospheric visibility and health.
Multimode light microscopy and fluorescence-based reagents as tools for the study of chemical and molecular dynamics of living cells and tissues
Authors: Taylor D. L.
Published: June 2020

Cells function through the complex temporal and spatial interplay of ions, metabolites, macromolecules and macromolecular assemblies. Biochemical approaches allow the investigator to define the components and the solution chemical reactions that might be involved in cellular functions. Static structural methods can yield information concerning the 2- and 3-D organization of known and unknown cellular constituents. Genetic and molecular techniques are powerful approaches that can alter specific functions through the manipulation of gene products and thus identify necessary components and sequences of molecular events. However, full knowledge of the mechanism of particular cell functions will require direct measurement of the interplay of cellular constituents. Therefore, there has been a need to develop methods that can yield chemical and molecular information in time and space in living cells, while allowing the integration of information from biochemical, molecular and genetic approaches at the cellular level.
Living and fixed neurons observed in brain slices by laser-scanned confocal light microscopy
Authors: Turner James N. , Szarowski Donald H. , Smith Karen L. , Swann John W
Published: June 2020

Thick slices of brain tissue are studied in vitro because neurons deep in the slice maintain physiologic contact with large numbers of other neurons, and are thought to function in a manner similar to that of in tact brain. The three-dimensional (3-D) morphology and electrophysiology of these cells can be studied and correlated. The confocal light microscope with its z-direction discrimination forms optical sections through the entire thickness of the slice, and stereo pairs or full 3-D reconstructions can be displayed using the optical sections as data sets. Individual neurons injected with fluorescent dyes or peroxidase based stains are imaged in either the fluorescent or reflection modes.
Visions of vision: Studies of the horseshoe crab compound eye
Authors: Chamberlain Steven C.
Published: June 2020

The lateral eye of the horseshoe crab, Limulus polyphemus, is an important model system for studies of visual processes such as phototransduction, lateral inhibition, and light adaptation. It has also been the system of choice for pioneering studies of the role of circadian efferent input from the brain to the eye. For example, light and efferent input interact in controlling the daily shedding of photosensitive membrane and photomechanical movements. Most recently, modeling efforts have begun to relate anatomy, physiology and visually guided behavior using parallel computing. My laboratory has pursued collaborative morphological studies of the compound eye for the past 15 years. Some of this research has been correlated structure/function studies; the rest has been studies of basic morphology and morphological process.
Three-dimensional localization of poly(A) RNA and splicing components in the nucleus
Authors: Carter Kenneth C. , Bowman Douglas , Carrington Walter , Fogarty Kevin , McNeil John A. , Fay Fredric S. , Lawrence Jeanne Bentley
Published: June 2020

The physical distribution of active genes has long been a subject of interest and speculation, however technical limitations have necessitated that it be addressed only by indirect approaches with sometimes contradictory results. However, developments in fluorescence in situ hybridization methodologies allow the position of specific genes and RNAs to be visualized directly within intact cells, thus providing a more direct means to study such questions. To address whether compartmentalization occurs during the production and processing of pre-mRNA in mammalian somatic cells we have recently investigated the distribution of nuclear polyadenylated transcripts which represent approximately 90% of all pre-mRNA. We found that poly(A) RNA forms discrete nuclear “transcript domains” which are specifically positioned with respect to the underlying genome and contain snRNP antigens of the pre-mRNA splicing class. Several lines of evidence indicate a close spatial and temporal linkage between transcription and processing of pol II RNAs (reviewed in 5), therefore, it is possible that poly(A) RNA transcript domains reflect a clustering of active genes at these sites.
High resolution spot scan imaging of frozen, hydrated actin bundles with 400kV electrons
Authors: Jakana J. , Schmid M.F. , Matsudaira P. , Chiu W.
Published: June 2020

Actin is a protein found in all eukaryotic cells. In its polymerized form, the cells use it for motility, cytokinesis and for cytoskeletal support. An example of this latter class is the actin bundle in the acrosomal process from the Limulus sperm. The different functions actin performs seem to arise from its interaction with the actin binding proteins. A 3-dimensional structure of this macromolecular assembly is essential to provide a structural basis for understanding this interaction in relationship to its development and functions.
Conformational switching in the flagellar filament of Salmonella typhimurium
Authors: Trachtenberg S. , DeRosier D.J.
Published: June 2020

The flagellum is the bacterial organelle of motility. It is constructed from a basal body (rotary motor) a hook (universal joint), and a filament (propeller). The filament is a self-assembling helical structure usually composed of one protein species – flagellin. Flaqellins from different species differ in their molecular weight and amino acid composition. However, the amino and carboxy termini of all flagellin are highly homologous. The outer flagellin domain, comprising the central part of the primary sequence, is variable and not obligatory for motility. To function as a propeller, the straight helical flagellin assembly, in which all subunits ace equivalent, needs to supercoil into a corkscrew-shaped rigid structure in which the subunits are quasiequivalent. The filament can be viewed as an assembly of 11 helical protofilaments or subunit strands. Supercoiling is believed to be possible due to the coexistence of flagellin subunits in two stable and switchable conformations. Switching is co-operative and each protofilament acts as a unit. Switched protofilaments differ in length from unswitched ones, the result of which is an introduction of twisting and bending forces which can be relieved by deformation or supercoiling of the filament. If all subunits are either in the R- or L- conformation, the filament is straight and either right-handed or left-handed, respectively. Progressive switching of protofilaments results in a total of 12 polymorphic states.
An ultrastructural study of sertoli cells in two geographically isolated populations of Aphanius dispar
Authors: Ba-Omar Taber A. , Prentis Philip F.
Published: June 2020

We have recently carried out a study of spermiogenic differentiation in two geographically isolated populations of Aphanius dispar (freshwater teleost), with a view to ascertaining variation at the ultrastructural level. The sampling areas were the Jebel Al Akhdar in the north (Group A) and the Dhofar region (Group B) in the south. Specimens from each group were collected, the testes removed, fixed in Karnovsky solution, post fixed in OsO, en bloc stained with uranyl acetate and then routinely processed to Agar 100 resin, semi and ultrathin sections were prepared for study.
Correlative confocal light microscopy and high-voltage electron microscopy of neurons
Authors: Turner J.N. , Szarowski D.H. , Decker D. , Smith K.L. , Fejtl M. , Swann J.W. , Carpenter D.O.
Published: June 2020

Neurons are cells with extensive dendritic and axonal arborizations extending from the cell body hundreds of micrometers or more in all three-dimensions. These structures have specializations, such as dendritic spines, that are at or just below the level of resolution of the light microscope (LM), and others, such as synapses, that can be resolved only in the electron microscope. Thus, it can be essential to correlate light and electron microscopic images from the same specimen. Due to its discrimination along the z-dimension (optic axis), the confocal light microscope is ideal for investigating neurons and correlating their structure and function. At the ultrastructural level, we use the high-voltage electron microscope (HVEM) to collect three-dimensional data, because it images thick objects. We are studying neurons in culture, and in thick acute and long term cultured brain slices. LM observations are made either after fixation or live by LM, and these images are correlated with HVEM ultrastructural observations.
Cryo-electron microscopy: The method of choice for direct study of 3D-shape of individual DNA molecules in a solution
Authors: Bednar Jan , Furrer Patrick , Stasiak Andrzej , Dubochet Jacques
Published: June 2020

3-D reconstruction of the trajectory of individual DNA molecules freely suspended in vitrified buffer opens new ways to study DNA. We showed that tightly supercoiled regions appearing as one thick filament can be reconstructed from their two projections. We present here use of this technique to trace normal double-stranded DNA regions to study the effect of DNA supercoiling on the overall shape of circular DNA molecules.
Use of F9 teratocarcinoma STEM cells to study cell-matrix interactions in the early mouse embryo
Authors: Lenburg Marc , Jiang Rulang , Cheng Lengya , Grabel Laura
Published: June 2020

We are interested in defining the cell-cell and cell-matrix interactions that help direct the differentiation of extraembryonic endoderm in the peri-implantation mouse embryo. At the blastocyst stage the mouse embryo consists of an outer layer of trophectoderm surrounding the fluid-filled blastocoel cavity and an eccentrically located inner cell mass. On the free surface of the inner cell mass, facing the blastocoel cavity, a layer of primitive endoderm forms. Primitive endoderm then generates two distinct cell types; parietal endoderm (PE) which migrates along the inner surface of the trophectoderm and secretes large amounts of basement membrane components as well as tissue-type plasminogen activator (tPA), and visceral endoderm (VE), a columnar epithelial layer characterized by tight junctions, microvilli, and the synthesis and secretion of α-fetoprotein. As these events occur after implantation, we have turned to the F9 teratocarcinoma system as an in vitro model for examining the differentiation of these cell types. When F9 cells are treated in monolayer with retinoic acid plus cyclic-AMP, they differentiate into PE. In contrast, when F9 cells are treated in suspension with retinoic acid, they form embryoid bodies (EBs) which consist of an outer layer of VE and an inner core of undifferentiated stem cells. In addition, we have established that when VE containing embryoid bodies are plated on a fibronectin coated substrate, PE migrates onto the matrix and this interaction is inhibited by RGDS as well as antibodies directed against the β1 integrin subunit. This transition is accompanied by a significant increase in the level of tPA in the PE cells. Thus, the outgrowth system provides a spatially appropriate model for studying the differentiation and migration of PE from a VE precursor.
Vanadium accumulation in alveolar macrophages studied with the Zeiss CEM902
Authors: Godleski John J. , Stearns Rebecca C. , Katler Marshall
Published: June 2020

Vanadium compounds are known to cause irritation of the respiratory system. Mechanisms of toxicity include actions at the cell membrane and mitochondria. However, the primary target of toxicity has not been delineated. Alveolar macrophages are the primary defensive cells of the lung and likely to interact with inhaled vanadium compounds. The purpose of this study was to identify sites of vanadium accumulation in alveolar macrophages. The Zeiss CEM902 with capabilities to detect vanadium within the ultrastructural context of the cell by Electron Spectroscopic Imaging (ESI) and by Electron Energy Loss Spectral (EELS) analysis was used for this investigation.
Ultrastructural characterization of the effects of beta-alanyl-melphalan in mouse Ehrlich ascites tumor cells and mouse liver cells
Authors: Adam Michael , Adam Bao-Ling Tsay , Wolfinbarger Lloyd
Published: June 2020

Beta-alanyl-melphalan (BAM) was demonstrated to have significant cancerocidal activity using both in vitro cultures and in vivo chemotherapy assays. Ultrastructural observations in the present study confirmed the antitumor activity of melphalan (MEL) and BAM. Results showed that the MEL affected the cellular elements causing marked cell damage both in mouse Ehrlich ascites tumor cells (MEATC) and mouse liver cells (MLC). BAM appeared to affect the cellular elements, with marked cell damage, only in MEATC, but not in the MLC. There were nuclear and cytoplasmic alterations in MEL and BAM treated MEATC, i.e. peripheral thickening of chromatin in nuclei, severe mitochondrial alterations, ribosome accumulation and autolysis phenomena which lead to the destruction of the subcellular structures.
Animal models of traumatic crush injury to skeletal muscle
Authors: Coleman R. , Rubinstein I. , Ben-Ari H. , Ronen N. , Silbermann M. , Better O. S.
Published: June 2020

One of the more serious conditions developing in humans buried or trapped under collapsed buildings is the development of Crush Syndrome, which frequently results in death (1,2). One of the effects of traumatic pressure damage to skeletal muscle is the development of myopathy and rhabdomyolysis resulting in severe life-threatening physiological disturbances. The aim of the present research was to develop animal models of traumatic pressure damage to limb muscles that mimic the effects of crush injury in humans, with the ultimate aim of improving strategies for the management of Crush Syndrome.
Electron and immunoelectron microscopy of experimental Reston virus infection in monkeys
Authors: Geisbert Thomas W. , Jahrling Peter B. , Jaax Nancy K.
Published: June 2020

The tissues and fluids of five cynomolgus macaques (Macaca fasicularis) experimentally inoculated with Ebola-related Reston virus were examined by transmission electron microscopy (TEM) at various stages of disease to provide insight into the pathogenesis of this newly discovered; potential human pathogen. TEM information obtained from this investigation was compared with findings previously reported in monkeys naturally infected with Reston virus.
Comparison of quantified coated pit profiles in thin sections and freeze-fracture replicas of granular epithelial cells of the toad urinary bladder
Authors: Shinowara Nancy L. , Yu Jenchang , Palaia Thomas A.
Published: June 2020

It is well known that stimulation of granular cells by arginine vasopressin (AVP) results in apical membrane changes, including an increased water permeability and an associated exocytotic delivery of aggregates of intramembrane particles, Endocytotic clathrin-coated pits appear in stimulated collecting duct principal cells, which transport water in mammalian kidneys. Recently, presumptive coated pits (CPs), identified in replicas, were reported in apical membranes of stimulated granular cells. This study describes the comparison of structurally defined sectioned-CPs (s-CPs per unit membrane length with presumptive, replicated-CPs (r-CPs) per unit area in bladders when initial CP formation was expected.
Unique method of tissue culture preparation for EM
Authors: Wang Fen , Ledford Lindsay B. , Head Jonathan F. , Elliott Robert L.
Published: June 2020

A simplified technique of growing monolayer cells for electron microscopic examination has been developed. Our procedure has eliminated many difficult steps and therefore is easier than those reported by others.

Regular Beem capsules for routine embedding for electron microscopy were used(Fig. 1). Prior to tissue inoculation capsules were washed with 5% HCl and gas sterilized. A 0.5 ml cell suspension of MCF-7 cells (10,000/ml) was placed in the capsules and cells settled in the pyramid portion (Fig. 2). Culture medium was alpha-MEM with 10% FCS. Capsules were incubated at 37°C for 3 days. They were then fixed in 70% ethanol for 20 minutes and stained with crystal violet. The pyramid portion of the capsule was cut off and monolayer cell growth was confirmed by examination under a microscope (Fig. 3).
Human gallstones: Specimen preparation and light microscopy
Authors: Sinicki Ronald , Viney Christopher
Published: June 2020

Several methods for removing gallstones from the human body are in use or under investigation. They range from noninvasive techniques (dissolving; ultrasound lithotripsy), through minor surgery (use of wire basket lithotriptor; laser lithotripsy), to major surgery. The choice of procedure seeks to accomplish removal of stones while minimizing the cutting of patient tissue, the post-treatment rehabilitation time, and the overall cost. The effectiveness of a given procedure will vary, depending on the size and number of stones present, and especially on their composition and microstructure. Attempts have therefore been made to correlate gallstone structure (from computerized tomography studies or magnetic resonance imaging with the least severe procedure needed to break up and remove the stone. Such empirical correlations can be facilitated by additional in vitro microstructural characterization of stones, which attempt to relate the in vivo observations to likely fracture paths and mechanisms. It is convenient to distinguish between three broad categories of gallstone. Cholesterol gallstones are associated with cholesterol supersaturation, when the level of cholesterol in bile exceeds the amount that the bile salts can keep in solution; they contain more than 25 wt% cholesterol and are relatively rare. Pigment gallstones contain less than 25 wt% cholesterol, and result from the precipitation and agglomeration of bilirubin and other inorganic salts. Mixed stones are the most common, and form the subject of our present investigations. Viewed in cross-section, they contain radiating crystals of cholesterol, together with concentric layers of apparently amorphous pigment. There are few literature references to the study of gallstone structure by light microscopy. We found only one reference to the microscopy of thin sections; others described low resolution reflected light studies of surfaces generated by dividing stones with a sudden impact delivered to a sharp knife. The drought of high resolution light micrographs even extends to pathology atlases.
Enzymatic digestion of seeds as a preparation technique for Scanning Electron Microscopy
Authors: Scott Randy , Ocumpaugh W. R.
Published: June 2020

The study of the microstructure of seed is an area of interest. Work in progress was confused by the difficulty in determining what part of the monocot seed was embryo and what part was endosperm. Routine histological facilities were not available and the imaging of the scanning electron microscope was desired.

The image seen on the left was prepared by simply cutting, mounting and coating the seed. This micrograph presents a puzzle to those of us who are not very familiar with the structure of seeds. Note, some organization is in evidence in the long section down the middle of a grass seed. With imagination, it might be thought that the embryonic leaflets can be seen. The rootlet and other structure presents a confusing display.
Jet freezing in enzyme and cosmetic research
Authors: Müller T. , Moser S. , Vogt M. , Brooker B.E. , Terren N.
Published: June 2020

Freezing has turned out to be the only method capable of immobilizing biological material in its natural state. Freeze-fracturing and replication complete this preparation protocol of specimens for transmission elctron microscopy (TEM) which is based on purely physical methods. With a propane-jet, specimens of a thickness up to 20 μm can be frozen without detectable ice crystal formation, Cell and macromolecule suspensions, emulsions, liquids and polymers in a solvent can be “sandwiched” between two copper foils and kept in place while a coolant is moved very rapidly against the opposite surfaces. In the present jet freezing device (JFD 030) the temperature of the specimen, while residing in a thermostatically controlled chamber, can be monitored between 10 and 90°C immediately prior to freezing. Thus physiologically interesting situations can be immobilized and any precooling of the specimen is avoided. A special device enables the abslutely simultaneous exposure of the specimen to the double-sided jet of the coolant. High cooling rates with an exceptional reproducibility are achieved routinely (Fig.1).
A cryogenic technique for the environmental SEM
Authors: Baron Robert , Garone Lynne C.
Published: June 2020

Understanding the distribution of fluid in a self-contained multi-layer film developing system can yield insights into the mechanistic process and impact the design of the product i.e. hardener levels, timing layers, hydrophobicity of layers. One of the challenges to the microscopist presented with this problem is the difficulty associated with imaging a wet photographic system at sufficient resolution to study any structural changes of the layers. Many indirect methods such as water uptake measurements as a function of time or model structures have been used. None have the ability to look at the individual layers as a function of developing time in it's true “wet state”.
Techniques for preparing theLolium perennecoleorhiza for scanning electron microscope evaluation
Authors: Debaene Susan B.G. , Gardner John S. , Allen Phil S.
Published: June 2020

The coleorhiza is a nonvascular sheath that encloses the embryonic radicle in Poaceae, and is generally the first tissue to emerge during germination. Delicate hairlike extensions develop from some coleorhiza cells prior to radicle emergence. Similar to root hairs, coleorhiza hairs are extremely sensitive to desiccation and are damaged by exposure to negative water potentials. The coleorhiza ofLolium perenneis somewhat spherical when first visible, after which a knob forms at a right angle to the caryopsis due to inner pressure from the elongating radicle. This knob increases in length until the radicle finally punctures the coleorhiza. Standard fixation procedures cause severe desiccation of coleorhiza cells and hairs, making morphological study of the coleorhiza difficult. This study was conducted to determine a more successful process for coleorhiza preservation.
An improved method of detection Auer rods in acute myelogenous leukemia by LM & TM
Authors: Chien K. , Ngan M. , Lee S.
Published: June 2020

Auer rods are large, elongated, eosinophilic granules that contain peroxidase, lysosomal emzymes and crystalline inclusions. They are specific for acute myelogenous leukemia (AML) and are present in leukemic blasts and promyelocytes. Their incidence is about 10-20 percent and varies between different subtypes of AML. We present here an improved method of detecting Auer rods by the use of eponembedded plastic sections.
Bacterial envelope profiles revealed by freeze-substitution
Authors: Graham L.L. , Beveridge T.J.
Published: June 2020

Traditional methods of processing bacteria for thin section electron microscopy rely on chemical fixation and dehydration under conditions which maximize specimen deterioration. Cryotechniques, however, use physical fixation (rapid freezing) and are slowly being recognized as a superior alternative to the more conventional methods. Freeze-substitution is a cryotechnique which combines cryofixation with a gentle chemical fixation and dehydration regimen, yielding specimens amenable to standard embedment procedures and ultramicrotomy. Previous study has shown that freeze-substitution retains the molecular composition of eubacteria better than conventional methods of processing. In this study we extend our observations and show that a simple freeze-substitution protocol reliably preserves the ultrastructure of a diverse range of microorganisms including archaeobacteria and anaerobic eubacteria.
Electron cryo-microscopy of nucleocapsids of sendai viruses
Authors: Charest P. M. , Jakana J. , Schmid M.F. , Vidal S. , Kolakofsky D. , Chiu W.
Published: June 2020

The Sendai virus is a member of the parainfluenza viruses. It is pathogenic in infants and children causing severe respiratory tract infection. The virion contains five structural proteins and two non-structural proteins encoded by the negative-strand RNA genome included in the nucleocapsid (NC). The physical nature of the NC helix may appear different under various ionic strength conditions or according the protocols used to isolate and process them for electron microscopy1-3 In the present work, electron cryo-microscopy has been applied to visualize the nucleocapsids of the Sendai virus in different salt conditions. Chemical treatments were avoided to eliminate possible artifactual conformations of the nucleocapsids and to facilitate direct and more reliable structural interpretations. We have used both 100 and 400 kV electrons to image the intact virions as well as the NC. The primary effect of electron energies on the images is a higher contrast seen at lower voltage.
Desmosomal distribution in the epidermis of a non-contracting human skin equivalent
Authors: Oakford L.X. , Dimitrijevich S.D. , Gracy R.
Published: June 2020

In intact skin the epidermal layer is a dynamic tissue component which is maintained by a basal layer of mitotically active cells. The protective upper epidermis, the stratum corneum, is generated by differentiation of the suprabasal keratinocytes which eventually desquamate as anuclear comeocytes. A similar sequence of events is observed in vitro in the non-contracting human skin equivalent (HSE) which was developed in this lab (1). As a part of the definition process for this model of living skin we are examining its ultrastructural features. Since desmosomes are important in maintaining cell-cell interactions in stratified epithelia their distribution in HSE was examined.
Internal compartmentation of the mitochondrion: An HVEM tomographic study
Authors: Marko Michael , Leith Ardean , McEwen Bruce , Frank Joachim , Mannella Carmen
Published: June 2020

Much of what is known about the internal organization of the mitochondrion has been inferred from thin-section electron microscopy. This work has shown this organelle to have two membranes (outer and inner) and a matrix (the area bounded by the inner membrane), but there is considerable uncertainty about the 3D shape of the cristae (the infoldings of the inner membrane) and the nature of the contacts between the inner and outer membranes. Attempts to reconstruct the mitochondrion’s interior by serial sectioning have failed because the required resolution (5-10 nm) cannot be practically achieved in the z-direction. The only 3D views provided until now have come from high-resolution SEM of freeze-cleaved and metal-shadowed mitochondria.
Analysis of multiple diffraction contrast
Authors: Vincent R.
Published: June 2020

Transmission microscopy of modern alloys, ceramics and semiconductor/metal contact/insulator assemblies often discloses unfamiliar crystalline compounds, either uncharted on the relevant phase diagrams (if available) or metastable. Although the standard technigues of convergent beam electron diffraction (CBED) are sufficient to establish the space group, further progress towards defining the contents of the unit cell requires at least some qualitative estimate of the structure factors F, which are obscured by the varieties of multiple diffraction paths followed by electrons. However, modern analytical microscopes contain condenser-objective optics which focus the electron beam into a probe with a large convergence angle (∼0.1 rad). Although the bright- and dark-field (BF and DF) discs in these CBED patterns inevitably overlap, suitable aperturing is sufficient to transmit only the large-angle pattern from the direct or from any diffracted beam.
Probe size and 5th-order aberration
Authors: Shao Zhifeng
Published: June 2020

A small electron probe has many applications in many fields and in the case of the STEM, the probe size essentially determines the ultimate resolution. However, there are many difficulties in obtaining a very small probe.

Spherical aberration is one of them and all existing probe forming systems have non-zero spherical aberration. The ultimate probe radius is given by

δ = 0.43Csl/4ƛ3/4

where ƛ is the electron wave length and it is apparent that δ decreases only slowly with decreasing Cs. Scherzer pointed out that the third order aberration coefficient always has the same sign regardless of the field distribution, provided only that the fields have cylindrical symmetry, are independent of time and no space charge is present. To overcome this problem, he proposed a corrector consisting of octupoles and quadrupoles.
Analytical Electron Microscopy of α-Al2O3 implanted with iron
Authors: Sklad P. S.
Published: June 2020

Ion implantation has become an accepted method for achieving a wide variation in the near surface microstructure and properties of many materials. A number of recent studies have concentrated on modifying the properties of Al2O3. However, the effectiveness of such surface modification is strongly dependent on the microstructural development which takes place in the implanted region during post-implantation annealing. Analytical electron microscopy (AEM) techniques are unique in that they allow direct observation of changes in microstructure and composition which are produced during such anneals.

Single crystals of α-Al2O3 in the basal orientation were implanted with 160 keV Fe ions to a dose of 4 x 1016 or 1 x 1017 ions/cm2 with a dose rate of ∼2 amps/cm2. The implantations were carried out at room temperature. A number of specimens were subsequently annealed for 1 h at temperatures in the range 973 K to 1773 K in flowing oxygen.