bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural diagnosis of peritoneal malignant mesothelioma
Authors: Siew S.
Published: June 2020

Mesothelial cells constitute the lining of the three serous sacs of the body i.e. the pleura, pericardium and peritoneum. The more common type of malignant neoplasia of the serous sacs is seeding by metastatic tumors and primary malignancy of the mesothelium is unusual. Of the three sacs, the pleura is the most common site of malignant mesothelioma. Involvement of the peritoneum is extremely rare.

We report 3 cases of malignant mesothelioma of the peritoneum. All of them were female. Their ages were 57, 67 and 72 years, respectively. The patients presented with abdominal discomfort and/or ascites. The extent of the tumors ranged from a peritoneal implant to widespread infiltration of the peritoneum and omentum. Histologic examination in Case 1 showed the presence of a diffusely infiltrating papillary mesothelioma without a sarcomatoid component. A mesodermal element was present in the other two cases. In order to establish a morphological diagnosis of malignant mesothelioma, the possibility has to be excluded of a metastatic adenocarcinoma.
Ultrastructural reaction of the dermis of a rat stung by scorpion (Leirus quinquestriatus)
Authors: Amr Z. , Amr S. , Al-Bagdadi F. , Al-Milhem W.
Published: June 2020

The animals injuries and their reaction to the effect of venomous animals has been reported in different parts of the world. The middle east with its large desserts, is part of the world were these venom animals are the cause of many injuries and deaths. The venoms, in general are about 90% proteins, each venom has several toxic components which act in combination to elicit its general and local effects. The reviewed literature revealed that most of the reported study on the effect of scorpion is : fibronecrosis of the dog's myocardium, hepatic lipolytic effect, lipid metabolism. Information on the effect of scorpion stings on the dermis is lacking. Recent studies on the effect of L. quenstriatus venom on mice, were reported. The changes involved the vascular bed, cellular degeneration of the liver, disruption of the microfilaments and the microtubules of nerve fibres. It is anticipated that this study is to provide the picture of the local ultrastructural changes of the dermal cells in response to the scorpion venom by stinging.
Ultrastructural evidence for bladder MAST cell degranulation and their imminent association with nerve fibers in patients with interstitial cystitis
Authors: He F. , Hofmeister M. , Ratliff T. , Becich M.
Published: June 2020

The ultrastructure of human mast cells (HMCs) in various diseases has been well documented; however, detailed morphological description of human bladder mast cells (HBMCs) in patients with interstitial cystitis (IC) is incomplete. The present study was undertaken to reveal any morphological modifications of human bladder mast cells (HBMCs) from the IC patients and to investigate the spatial relationships between nerve fibers and these mast cells at the ultrastructural level.

Fresh-fixed surgical biopsy specimens from IC patients as well as paraffin blocks of IC retrieved through our medical record archival system were processed with routine and deparaffinization methods for transmission electron microscopy (1). No differences in mast cell morphology were noticed between the fresh-fixed or paraffin embedded tissues.

The general electron microscopic appearances of the HBMCs in IC located in both mucosa and muscle layers were similar to those of HMCs observed in other sites where mastocytosis may occur due to various pathological processes (Fig. 1).
Use of thin sections and freeze-etch replicas to differentiate the macrogametocyte from the microgametocyte in the malarial parasite Plasmodium falciparum
Authors: Meszoely Charles A. M. , Venugopal Devi , Erbe Eric F. , Wergin William P.
Published: June 2020

Gametocytes of Plasmodium falciparum grown in culture were chemically fixed in 2% glutaraldehyde. For observation of thin sections, specimens were postfixed in 1 % osmium tetroxide, dehydrated in ethanol, and embedded in resin. Thin sections were stained with uranyl acetate and lead citrate and examined with a Zeiss EM-10 transmission electron microscope (TEM). For observations of freeze-etched replicas, specimens were cryoprotected in 30% glycerol, fractured, etched, shadowed and coated in a modified Denton DFE-2 module. The replicas were examined with a JEOL JEM 100-B TEM.

Previous ultrastructural studies on the gametocytes of many species of Plasmodium compared and contrasted the pellicular complex and cytoplasmic organelles, but differentiation of the macrogametocyte and the microgametocyte in freeze-etched preparations has not been reported. The intraerythrocytic macro- and microgametocytes can be easily differentiated by their staining properties in Giemsa stained preparations examined by light microscopy. The present study, using thin sectioning and freeze-etching techniques, differentiates the macrogametocyte from the microgametocyte of Plasmodium (Laverania) falciparum (Welch, 1897) by characterizing their cytoplasmic organelles.
Localization of cell-surface and basement-membrane heparan-sulfate proteoglycans using the malaria circumsporozoite protein
Authors: Frevert U. , Sinnis S. , Cerami C. , Nussenzweig V.
Published: June 2020

Malaria sporozoites, which invade hepatocytes within minutes after transmission by an infected mosquito, are covered with the circumsporozoite (CS) protein, which in all Plasmodium species contains the conserved region II-plus. This region is also found as a cell-adhesive motif in a variety of host proteins like thrombospondin, properdin and the terminal complement components.

The CS protein with its region II-plus specifically binds to heparan sulfate proteoglycans (HSPG) on the basolateral surface of hepatocytes in the space of Disse (FIG. 1), to certain basolateral cell membranes and basement membranes of the kidney (FIG. 2) as well as to heparin in the granules of connective tissue mast cells. The distribution of the HSPG receptors for the CS protein was examined by incubation of Lowicryl K4M or LR White sections of liver and kidney tissue with the recombinant CS ligand, whose binding sites were detected with a monoclonal anti-CS antibody and protein A gold.
An immunocytochemical, cytosol, and ultrastructural study of tissue ferritin in breast carcinoma
Authors: Elliott Robert L. , Wang Fen , Elliott Mary C. , Head Jonathan F.
Published: June 2020

Increased levels of serum ferritin in breast carcinoma is well known, however, its exact source has been disputed. Weinstein et al found six times the ferritin concentration in malignant tissue as compared to benign tissue. The anaplastic tumors had the highest ferritin concentrations, suggesting that the major site of the increased ferritin was the malignant epithelium. We found in a previous cytosolic and electron microscopic study of tissue ferritin in breast carcinoma that the malignant epithelium is almost certainly the source of the increased ferritin.

To better define and expand this study and increase our knowledge of the role of transferrin receptors and iron metabolism in breast cancer, we began an immunocytochemical study of tissue ferritin to compliment our cytosol and ultrastructural observations. This was done with a mouse antihuman ferritin monoclonal antibody. To date 92 specimens have been examined by all three techniques. Immunocytochemical tissue slides showed intense staining of the cytoplasm with immunoperoxidase, and the intensity of the cytoplasmic staining correlated with the cytosolic concentrations and the electron microscopic findings.
The vascular morphology of the rabbit ureter: A corrosion-cast study
Authors: Douglas G. C. , Hossler F. E.
Published: June 2020

The prevention of urological complications in renal homotransplantation and ureteral reconstruction requires preserving the integrity of the ureteral blood supply. Vascular insufficiency is believed to be the underlying cause of ureteral necrosis and urinary extravasation in kidney transplant surgery. However, the ureteral vasculature has been described primarily at the gross level. Because of its critical role in the success of renal transplants and its potential vulnerability to surgical trauma, the ureteral vasculature deserves a more detailed investigation.

We studied the ureteral vasculature (UV) in 29 male New Zealand rabbits using routine light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) of vascular corrosion casts. After cannulation of the abdominal aorta, the UV was perfuse fixed with buffered glutaraldehyde, embedded, and cut into thin sections for LM and TEM. For corrosion casting the UV was perfused with buffered saline and filled with resin (Mercox®/methylmethacrylate, 4/1) at physiological temperature and pressure. Cast tissues were macerated with 10% KOH, washed in water, critical point dried, and mounted with silver paste for routine SEM examination.
Atomic-Force Microscopy techniques for imaging cells and biological macromolecules in solution
Authors: Marchese-Ragona Silvio P. , Christie Briggs , Bucher Roland
Published: June 2020

The Atomic Force Microscope (AFM) is increasingly being used in the Life-Sciences field. With this increase in usage there has occurred a concomitant increase in the need for both better developed specimen preparation techniques and better defined operational parameters for the AFM instrument. Life-Science AFM methodology can be divided in to three main areas:

Support substrate for the Specimen,

Immobilization techniques for attaching the specimen to the support substrate, and

Optimum instrument scan parameters to ensure reliable transfer of data from the specimen to the image.

Of central importance to Life-Science AFM is the nature of the substrate to be used. The most reliable substrates are those with a well documented surface, whose features are at least an order of magnitude smaller than the specimens of interest. Furthermore, the material should be transparent so that other forms of microscopy can be used (i.e. light, fluorescence, near-field scanning optical, etc.) and the surface chemistry should be both well documented and susceptible to chemical derivitization.
Biomedical applications: Pitfalls in the practice
Authors: Shelburne J. D. , Ingram Peter , Roggli Victor L. , LeFurgey Ann
Published: June 2020

At present most medical microprobe analysis is conducted on insoluble particulates such as asbestos fibers in lung tissue. Cryotechniques are not necessary for this type of specimen. Insoluble particulates can be processed conventionally. Nevertheless, it is important to emphasize that conventional processing is unacceptable for specimens in which electrolyte distributions in tissues are sought. It is necessary to flash-freeze in order to preserve the integrity of electrolyte distributions at the subcellular and cellular level. Ideally, biopsies should be flash-frozen in the operating room rather than being frozen several minutes later in a histology laboratory. Electrolytes will move during such a long delay. While flammable cryogens such as propane obviously cannot be used in an operating room, liquid nitrogen-cooled slam-freezing devices or guns may be permitted, and are the best way to achieve an artifact-free, accurate tissue sample which truly reflects the in vivo state. Unfortunately, the importance of cryofixation is often not understood. Investigators bring tissue samples fixed in glutaraldehyde to a microprobe laboratory with a request for microprobe analysis for electrolytes.
Introduction to electron holography
Authors: McCartney M. R.
Published: June 2020

Electron holography is an imaging method in the transmission electron microscope (TEM) whereby the phase and amplitude of the electron wavefront can be obtained separately, unlike the conventional image which represents the intensity of the electron wave without any direct phase information. In particular, the phase image allows for the possibility of directly imaging the electric and magnetic potentials within a sample on the basis of phase changes produced on the incident electron wavefront. There are many advantages to directly imaging the phase structure and specific examples of the unique information available will be shown. For example, once the phase image is obtained it is possible to correct for the phase changes imposed by the transfer function of the objective lens by directly applying an inverse phase plate.

Electron holography was originally proposed in 1949 by Gabor as a means of improving the resolution of electron micrography by correction of spherical aberration but was never fully utilized due to inadequate electron sources. In recent years, the availability of reliable field emission guns as coherent electron sources has stimulated renewed interest in the technique.
On-line image readout in CTEM
Authors: Herrmann K.-H. , Rau W. D. , Sikeler R.
Published: June 2020

Quantitative recording of electron patterns and their rapid conversion into digital information is an outstanding goal which the photoplate fails to solve satisfactorily. For a long time, LLL-TV cameras have been used for EM adjustment but due to their inferior pixel number they were never a real alternative to the photoplate. This situation has changed with the availability of scientific grade slow-scan charged coupled devices (CCD) with pixel numbers exceeding 106, photometric accuracy and, by Peltier cooling, both excellent storage and noise figures previously inaccessible in image detection technology. Again the electron image is converted into a photon image fed to the CCD by some light optical transfer link. Subsequently, some technical solutions are discussed using the detection quantum efficiency (DQE), resolution, pixel number and exposure range as figures of merit.

A key quantity is the number of electron-hole pairs released in the CCD sensor by a single primary electron (PE) which can be estimated from the energy deposit ΔE in the scintillator,
Morphological characteristics of linear (AB)n multiblock copolymers near the order-disorder transition
Authors: Spontak Richard J. , Laurer Jonathan H. , Smith Steven D. , Ashraf Arman , Samseth Jon
Published: June 2020

Linear (AB)n multiblock copolymers constitute a new class of copolymers which order into periodic morphologies when the A and B blocks are sufficiently incompatible. Unlike diblockcopolymers (n=1), perfectly alternating multiblock copolymers with n>1 possess midblocks which are capable of adopting either looped or bridged conformations (see Fig. 1). Coexistence of looped and bridged midblocks with non-uniformly stretched endblocks poses an intriguing problem with regard to chain packing and elasticity. Previous theoretical and experimental studies of multiblock copolymers in the strongsegregation regime, wherein repulsive A-B interactions dominate, have demonstrated that, due to the 22(n-1) molecular conformations available, linear multiblock copolymers differ considerably from their AB diblock and ABA triblock analogs in terms of phase stability, microstructural dimensions, and macroscopic properties. In the present work, transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) have been employed in concert to study the morphological features of weakly-segregated (AB)n multiblock copolymers near the order-disorder transition.
Effect of random midblock sequencing on the morphological characteristics of symmetric A(A/B)B triblock copolymers
Authors: Laurer Jonathan H. , Spontak Richard J. , Smith Steven D. , Ashraf Arman
Published: June 2020

Significant efforts have been put forth to elucidate the morphological features of strongly-segregated AB diblock copolymers, in which contiguous sequences of A and B monomers are incompatible and order into periodic morphologies. In this regime, interactions between chemically dissimilar blocks are repulsive, and the interphase separating adjacent microdomains is relatively narrow. While the properties of a diblock copolymer can be modified without changing monomer species, introduction of random A/B sequencing into the molecular architecture has received limited attention. The morphological features of diblock copolymers possessing one A/B block have been previously examined, and Smith et al. are currently exploring the morphological behavior of "random" diblock copolymers with two A/B blocks of differing composition. In this work, TEM is used to discern the morphologies of copolymers in which an A/B segment is incorporated between the endblocks (see Fig. 1). Tapered copolymers, wherein the A/B segment possesses a composition gradient, as well as non-tapered copolymers, are considered.
A global electronic imaging and distribution system employing a computer network
Authors: Palatini Dennis J.
Published: June 2020

BACKGROUND Conventional silver halide photography has been used successfully for over one hundred years and remains unsurpassed in quality and fidelity for recording and displaying image information. During the past decade the impact of computers on all fields of information sciences has been both profound and widespread. Recently, personal computers have been acknowledged as effective and efficient tools for assuming the role of conventional photography. A simple, rapid, and well-established system was in place at Unilever to distribute the written word (electronic mail), however, no system was available to manage and distribute scientific images. An inordinate amount of time was elapsing between the time images were formed and when our colleagues viewed them Also, imaging scientists were spending an excessive amount of time in the darkroom developing and printing images. The Unilever Global Electronic Imaging and Distribution System was developed to address these growing problems.

SYSTEM CONFIGURATION The configuration of the Unilever System is depicted in Figure 1. It consists of a restricted LAN (local area network) which isolates imaging traffic for optimal speed. This communication network still allows communication to the site LAN via the hub and Ethernet backbone and vice versa. The hub is an intelligent network controller that isolates network traffic.
Antibiotic impregnated orthopaedic bone cement: Kinetics and impact of teicoplanin on staphylococcal colonization
Authors: Edmiston Charles E. , Goheen Michael P.
Published: June 2020

Previous studies in our laboratory have questioned the efficacy of antibiotic impregnated bone cement to prevent staphylococcal colonization of orthopaedic implants following surgery. Teicoplanin a glycopeptide antibiotic with excellent anti-staphylococcal activity was added to polymethylmethacrylate in concentrations ranging from 2-5 wt%. Five staphylococcal strains recovered from orthopaedic implant infections were chosen for study: 2-Staphylococcus aureus and 3-Staphylococcus eoidermidis. Two of the staphylococcal isolates were identified as producing an exopolysaccharide slime following alcian blue staining with lysine. The in vitro release of antibiotic from the resin surface was determined by biological assay at 0, 12, 24, 48, 96 and 10 days post-study. Mean teicoplanin concentrations ranged from 200 to 430 ug/ml at 0 hour and 22 to 50 ug/ml at 10 days post-study. Teicoplanin impregnated and drug free resin controls were exposed to standardized inoculum (5.0 log10 colony forming units/ml) of the staphylococcal clinical isolates and incubated at 35°C in physiologic buffered saline with 0.25% dextrose.
Ultra-high resolution column for the scanning electron microscope
Authors: Drexel V. , Weimer E. , Martin J.-P.
Published: June 2020

1.Introduction

The demands made on the design of a high-performance SEM column are multiple and contradictory. It should provide outstanding image resolution at all beam energies with samples of all sizes and at any (reasonable) tilt angle. It should also allow excellent signal detection under all operating conditions and a high x ray take-off angle at a working distance suitable for high-resolution microscopy. A novel design concept for the electron optics of the SEM has been implemented in a new high-performance instrument (named DSM 982 GEMINI) in order to meet these goals.

2.Advanced electron-optical column

A Schottky field emission source is used in the new SEM. This gun type exhibits the ideal point-source properties for a high-performance instrument. Optimum conservation throughout the column of the very high beam brightness (107 A/cm2.sr.kV) and the very low beam energy spread (0.4 eV) supplied by the gun is achieved by the implementation of a new electron optical principle: a high beam energy is maintained throughout the column (regardless of of the electron probe energy selected by the operator) and any beam cross-over is avoided (Fig. 1).
Advanced electron optics for micro- and nano-analysis in the TEM
Authors: Benner G. , Bauer R. , Probst W. , Weimer E. , Martin J.-P.
Published: June 2020

1. Introduction

In the materials sciences as well as in the life sciences energy-dispersive x-ray microanalysis (EDX) in the transmission electron microscope (TEM) is now established as a routine investigation method allowing high-sensitivity qualitative and quantitative element detection. The accuracy of the results obtained and the measurement time needed are largely determined by the following properties of the TEM used: shape of the objective lens pole-piece and design of the illumination system, collimation of the beam path and operation flexibility of the illumination system.

2. Optimized X-ray detection

In the EM 910 the design concept of the objective lens allows the x-ray detector to be placed closer to the specimen than usual (Fig. 1). Therefore an extremely high solid angle (i. e. 0.192 sr) of the x-ray signal can be intercepted by a 30 mm2-detector at a take-off angle of 20°. As a result, x-ray spectra can be acquired with a high countrate and a clearly improved signal-to-noise ratio. Element distribution maps with much improved information density can be acquired in the usual registration times.
Performance of the Philips CM200 FEG
Authors: Otten Max T.
Published: June 2020

Since its introduction four years ago the Philips Field Emission 200 kV microscope has undergone a number of changes enhancing its performance. It has also become possible to quantify its performance more accurately.

New developments are the introduction of the SuperTWIN-α and UltraTWIN objective lenses and the CompuStage goniometer. The SuperTWIN-α objective lens has a higher maximum tilt angle (±40° instead of ± 15°) while the point resolution remains 0.24 nm. The UltraTWIN lens has a point resolution of 0.19 nm and a maximum tilt of ±24°. Better specimens for determining the information limit have resulted in proven information limits of < 0.15 nm and ≤0.13 nm for the SuperTWIN-α and UltraTWIN lenses, respectively. The CompuStage, a five-axis motorised and computer-controlled goniometer, improves performance with regard to safety (no danger of damage to specimen holder or pole pieces), maximum accessible tilt, accuracy of movement, control and drift. The accessibility of the CompuStage to external computer control makes this goniometer ideal for developments in automation such as tomography or computer-assisted tilting for diffraction.
X-ray mapping without STEM
Authors: Brock Judith M. , Otten Max T.
Published: June 2020

A knowledge of the distribution of chemical elements in a specimen is often highly useful. In materials science specimens features such as grain boundaries and precipitates generally force a certain order on mental distribution, so that a single profile away from the boundary or precipitate gives a full description of all relevant data. No such simplicity can be assumed in life science specimens, where elements can occur various combinations and in different concentrations in tissue. In the latter case a two-dimensional elemental-distribution image is required to describe the material adequately. X-ray mapping provides such of the distribution of elements.

The big disadvantage of x-ray mapping hitherto has been one requirement: the transmission electron microscope must have the scanning function. In cases where the STEM functionality – to record scanning images using a variety of STEM detectors – is not used, but only x-ray mapping is intended, a significant investment must still be made in the scanning system: electronics that drive the beam, detectors for generating the scanning images, and monitors for displaying and recording the images.
Microscopy of stress-induced morphological development and dislocation nucleation during semiconductor epitaxy
Authors: Jesson D. E. , Chen K. , Pennycook S. J. , Baribeau J.-M. , Houghton D. C.
Published: June 2020

Semiconductor films subjected to misfit stresses are unstable to the formation of surface undulations or waves. Atoms located in close proximity to the peaks of the undulations can relax and significantly lower the elastic energy of the film. Provided that the wavelength of the undulation is sufficiently large, this more than compensates for the associated increase in surface energy, leading to a morphological instability of the flat surface.

An interesting feature of this instability is that although atomic planes near the peaks of the undulations can relax, stress concentrations develop at the undulation valleys. These stresses can be very large, even for rather shallow surface perturbations. The question, therefore, naturally arises as to the subsequent effect of these stresses on the evolving surface morphology and in particular, whether the magnitude of the stress is large enough to influence the nucleation of misfit dislocations. In order to study these issues experimentally, we have utilized Z-contrast imaging , atomic force microscopy (AFM), and plan-view transmission electron microscopy (TEM) to image the stress-induced surface evolution of SixGe1-x alloys which are compressively strained on Si(100).
Pulsed-laser deposition growth of copper oxide on α-Al2O3 and MgO
Authors: Bench Michael W. , Carter C.Barry
Published: June 2020

Copper and its oxides are involved in many electronic materials applications. Cuprous oxide (Cu2O)is a semiconductor finding usage as a thin-film solar-cell material. The copper-oxide-based hightemperature superconductor materials have been extensively investigated. Also, the adhesion andbonding ofcopper to ceramic substrates is of interest for usage in electronic device packaging applications. For the case of alumina substrates, it has been demonstrated that the adhesion properties of thin copper wires is optimized for a ternary bonding environment at the interface. For the growth of oxidematerials, pulsed-laser ablation (PLA) is a viable means of growing films, and allows materials with a wide range of stoichiometrics to be produced. Indeed, this technique has found wide application inthe growth of high-temperature superconductors. In a previous study on PLA growth of CuO and Cu2O, Ogale etal. reported the growth of continuous epitactic Cu2O films on (100) MgO substrates at 700°C, whereas growth onto silicon and zirconia produced polycrystalline films.
Topography studies of magnetic-head pole-tip areas using atomic-force microprobe
Authors: Veisfeld Nina
Published: June 2020

Atomic Force Microscopy (AFM) has made it possible to quantify an important phenomenon regarding magnetic head characterization, known as pole tip recession. The pole tip area of thin film magnetic heads, considered one of the critical regions in the head/disk interaction, became the subject of increasing concern within the past several years because of the rapid decrease of the flying heights (typical present values are ∽300 Å). The area of interest includes plated permalloy pole tips and the surrounding alumina matrix, sputter deposited onto a ceramic substrate. The complex topography of thearea is associated with the hardness differences between the materials in multiple layers compsiring the head.

AFM analysis revealed significant variations in the topography of different thin film heads. Figure 1 presents a typical example of the pole tip area topography. In this AFM image the two pole tips are elevated above the surrounding matrix. A dark area above the upper pole (recessed by ∽190Å vs. the poles) and slightly brighter (elevated by ∽160Å) symmetrically positioned areas on both sides of the poles are clearly outlined.
Thickness dependence of ferroelectric domains in thin ferroelectric crystals
Authors: Tsai F. , Cowley J. M.
Published: June 2020

Transmission electron microscopy (TEM) has been used to study the microstructures, especially the ferroelectric domains and boundaries, of ferroelectric crystals and free-standing thin films because they are closely related to the ferroelectric properties of thin films. But, for a long time observations have been made on the assumption that the properties of ferroelectric domains and domain boundaries are the same as those of the bulk crystal, even though sometimes some evidence may have been shown that ferroelectric domains in thin films could be different from those in the bulk material. In fact, weak ferroelectricity of thin films has been noticed. It was found that the ferroelectric characteristics of thin BaTiO3 ferroelectric films deposited on substrates are different from those of bulk materials. Although in their analysis interfaces and grain boundaries are involved, the mechanism of weak ferroelectricity of thin films and the microstructures which are related to the ferroelectricity of the film remains unclear.
Channeling in and channeling out: The origins of electron backscattering and electron channeling contrast
Authors: Joy D. C.
Published: June 2020

Two techniques are now in common use for obtaining crystallographic information from crystals in the scanning electron microscope (SEM) - electron channeling patterns (ECP) in which variations in the angle of incidence of the beam with respect to crystal produce variations in the backscattering yield; and electron backscattering patterns (EBSP) in which a stationary electron beam impinges on the crystal and anisotropies in the angular distribution of the backscattering profile are viewed on a screen. The ECP and EBSP techniques seem superficially to be very different, but they are in fact closely related through the principle of reciprocity and the concept of Bloch waves. A plane electron wave incident on a crystal can be decomposed into Bloch waves ψi which are the solutions of the Schroedinger equation for waves in a periodic potential. In the simplest case (figure 1) just two waves are present. The maxima in the probability distributions I ψi. ψi*| of these Bloch waves (i.e the chance of finding an electron) are periodic with a repeat distance equal to the lattice spacing, but for wave I these maxima occur half-way between the planes while for wave II the maxima occur on the lattice planes.
Texture measurements in Al2O3 using BEKP
Authors: Vaudin M. D. , Cline J. P.
Published: June 2020

The study of preferred crystallographic orientation (texture) in ceramics is assuming greater importance as their anisotropic crystal properties are being used to advantage in an increasing number of applications. The quantification of texture by a reliable and rapid method is required. Analysis of backscattered electron Kikuchi patterns (BEKPs) can be used to provide the crystallographic orientation of as many grains as time and resources allow. The technique is relatively slow, particularly for noncubic materials, but the data are more accurate than any comparable technique when a sufficient number of grains are analyzed. Thus, BEKP is well-suited as a verification method for data obtained in faster ways, such as x-ray or neutron diffraction. We have compared texture data obtained using BEKP, x-ray diffraction and neutron diffraction. Alumina specimens displaying differing levels of axisymmetric (0001) texture normal to the specimen surface were investigated.

BEKP patterns were obtained from about a hundred grains selected at random in each specimen.
TEM investigations of surface residual stress relaxation in A12O3 and Al2O3-SiC nanocomposite
Authors: Fang J. , Chan H. M. , Harmer M. P.
Published: June 2020

It was Niihara et al. who first discovered that the fracture strength of Al2O3 can be increased by incorporating as little as 5 vol.% of nano-size SiC particles (>1000 MPa), and that the strength would be improved further by a simple annealing procedure (>1500 MPa). This discovery has stimulated intense interest on Al2O3/SiC nanocomposites. Recent indentation studies by Fang et al. have shown that residual stress relief was more difficult in the nanocomposite than in pure Al2O3. In the present work, TEM was employed to investigate the microscopic mechanism(s) for the difference in the residual stress recovery in these two materials.

Bulk samples of hot-pressed single phase Al2O3, and Al2O3 containing 5 vol.% 0.15 μm SiC particles were simultaneously polished with 15 μm diamond compound. Each sample was cut into two pieces, one of which was subsequently annealed at 1300° for 2 hours in flowing argon. Disks of 3 mm in diameter were cut from bulk samples.
AEM characterization of SiC fiber/AIN composites
Authors: Park K. , Sung C.
Published: June 2020

SiC fiber (15 vol. %)/AlN composites were fabricated by hot pressing at 1650°C and 17.6 MPa using a 4Ca(OH)2·Al2O3 sintering aid under vacuum atmosphere. Creep tests for the composites were conducted at compressive stress of 50 MPa and at 1120°C for 48 hours under oxygen atmosphere. Cross-sectional TEM samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector. Selected area diffraction (SAD), convergent beam electron diffraction (CBED), and energy dispersive X-ray spectroscopy (EDXS) were used to identify the microstructure and microchemistry of the matrix, fiber, and matrix/fiber interface of the composites.

Generally, the AIN matrix contained a liquid phase at grain boundaries and a high density of dislocations within the grains (Fig. 1(a)). Most of the additives were present at the grain boundaries. Fig. 1(b) shows a SAD pattern from the liquid phase at the grain boundaries. The liquid phase was identified as Ca12Al14O33 with a cubic structure (a = 1.198 nm).
Study of the growth of TiO2 on A12O3 by pulsed-laser ablation
Authors: Bench M. W. , Carter C.B.
Published: June 2020

There has been an increasing interest in recent years in the growth of epitactic oxide thin films for use in a variety of technological applications, including optical and electronic devices. A number of fundamental aspects of the growth of TiO2 films on alumina substrates by metal-organic chemical vapor deposition have been reported by Chang et al. For the case of MgO, Hesse et al. demonstrated the epitactic growth by pulsed-laser deposition of YBa2Cu3O7-x on (001) MgO passivated by a layer of the inverse spinel Mg2TiO4. The Mg2TiO4 layer was formed directly by a vapor-phase solid-state reaction during the deposition by e-beam evaporation of TiO2 onto heated MgO substrates. In other studies, TiO2 thin films have been grown using a variety of deposition techniques. For the growth of oxide materials in general, pulsed-laser ablation is a viable means of growing films, and allows materials with a wide range of stoichiometrics to be produced.
TEM studies of alumina fiber-reinforced partially stabilized zirconia composites
Authors: Park K. , Sung C.
Published: June 2020

Zirconia has attracted considerable interest for structural applications because of its high fracture strength and fracture toughness. Polycrystalline alumina (PCA) chopped fiber (10 vol. %)-reinforced yttria partially-stabilized zirconia (Y-PSZ) composites have been fabricated by hot pressing at 1550°C and 2200 psi under vacuum atmosphere. The microstructure of the matrix, fiber, and matrix/fiber interface of the composites was characterized using transmission electron microscopy in order to correlate the microstructural and mechanical properties. Cross-sectional TEM samples were prepared by mechanical grinding, dimpling, and ion-milling. The samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector. Selected area diffraction (SAD) and energy dispersive X-ray spectroscopy (EDXS) were used to identify the microstructure and microchemistry of the composites, respectively. The mechanical properties of the composites at room temperature were obtained using four-point bending tests. Creep tests were conducted by four-point bending at 1100°C and compressive stress of 46.3 MPa for 24 hours in air.
Investigation of a washer embedded in an orbiter vehicle tile
Authors: Kim H. S. , Cummings V. J.
Published: June 2020

At NASA’s Kennedy Space Center (KSC), an engineering debris team performs a post-landing inspection of the space shuttle orbiter for debris and for anomalies in the thermal protection system. The areas of inspection and debris sampling include the orbiter windows, lower surface orbiter tiles, reinforced carbon-carbon panels of the orbiter wings, and the external tank (ET)/orbiter umbilicals.

On October 18, 1989, the space shuttle Atlantis was launched from launch pad 39B at KSC. Atlantis landed on runway 23 at Edwards Air Force Base, California on October 23, 1989. During the post-landing inspection performed October 23-24, 1989, a washer, approximately 1/2 inch in diameter, was found embedded in one of the lower surface tiles forward of the LH2 ET/orbiter umbilical area. The washer was oriented perpendicular to the airflow, and approximately half of the washer protruded into the aerodynamic flow.

The washer was submitted to the NASA KSC microchemistry laboratory for examination and elemental and phase analysis.
Quantitative TEM analysis of microstructural anisotropy
Authors: Dahmen U. , Thangaraj N. , Kilaas R.
Published: June 2020

Preferred orientation of grain boundaries or interfaces in solids is an important indicator of anisotropy in boundary energy or kinetics. The present study is part of an ongoing investigation of faceting in thin films with the mazed bicrystal microstructure which possesses several unique features that are difficult to measure with standard parameters such as grain size distribution. One of the important characteristics of this microstructure is the degree and type of anisotropy. Figure 1 shows a micrograph with a typical mazed bicrystal microstructure. Only two grain orientations with about equal volume fraction are seen in black and white contrast, respectively. It is apparent that unlike a normal polycrystalline thin film, individual grains in this microstructure have unusual convoluted shapes with both concave and convex regions.

The standard stereological method to measure microstructural anisotropy is the rose plot generated from a count of intersections with a reference grid overlaid on the micrograph at different angles.
Measuring rigid shifts at interfaces by HREM
Authors: Merkle K. L. , Buckett M. I.
Published: June 2020

The interfacial energy of an internal interface between two solid crystals can be lowered by local atomic relaxations. In addition to such short-range atomic readjustments, the microscopic displacement of the crystals relative to each other, the rigid-body translation, has been known to provide a major relaxation mechanism for the minimization of grain boundary (GB) energy. In particular, the component normal to the interface, the volume expansion, has been directly linked to GB energy, as suggested more than 30 years ago by Seeger and Schottky. More recently, detailed atomistic computer simulations by Wolf have shown a roughly linear relationship between GB energy and volume expansion for a wide range of GB geometries in metals. In ceramic GBs the relationship between volume expansion and energy is less well established theoretically. For these reasons, and also because of possible direct connections of GB excess volume to a range of GB properties, such as segregation, intergranular fracture, and GB diffusion, experimental measurements of GB volume expansion is an important task of electron microscopy.
A method for 3-D structure retrieval of interfaces by quantitative analysis of HRTEM micrographs
Authors: Höche T.
Published: June 2020

An understanding of many properties of polycrystalline materials requires knowledge of the atomistic structure and composition of grain boundaries (GBs). Recently, Kenway developed atomistic GB models for α-Al2O3 by computer simulation. It is most desirable to determine the atomistic three-dimensional (3-D) GB structure experimentally, not only to check the theoretical calculations but also to investigate the possibilities and limitations of quantitative high-resolution electron microscopy (HREM). The 3-D analysis must be performed on the GB along (at least) two different projections and requires specific image processing steps for micrographs taken along each projection. The experimental micrographs must be compared with simulated images of the refined structure until a “best fit” is achieved. So far, only 2-D optimization procedures have been introduced to do the fitting quantitatively for one projected structure. The basic concept of such analyses is to calculate an objective function and subsequently vary free parameters (in this case atomic positions) until a maximum of the objective function in the multidimensional parameter space is found.
Diffraction analysis of HREM images from a plasma-deposited iron carbide film
Authors: Siriwardane H. , Fraundorf P. , Pringle O. A. , James W. J. , Newkirk J. W.
Published: June 2020

The selected area diffraction information in a single HREM image (Fig. 1) of iron carbide, plasma-deposited onto a carbon support film at 300°C is examined. By “selected area diffraction information” we mean power spectra of selectively digitized regions of the negative. The amount of post microscope diffraction analysis that can be done from a single HREM negative is thus illustrated. It is important for us to know whether these crystals belong to a single phase or whether mixtures of phases are present in these films. X-ray characterization of films deposited on glass substrates at the above deposition temperature have always indicated only Fe7C3. Auger depth profiling data from such films on glass and on carbon support films, along with electron diffraction data from these specimens have indicated the presence of some Fe3O4 in these films as well.

Six areas of the negative that showed cross-fringes were digitized and are shown in Fig. 2.
HREM study of tetragonal zirconia in Al2O3/ZrO2 multilayers
Authors: Gajdardziska-Josifovska M. , McCartney M. R. , de Ruijter W. J. , Scanlan C. M. , Aita C. R.
Published: June 2020

The bulk zirconia-alumina system is a model ceramic composite whose fracture toughness is increased via martensitic transformation: i.e. metastable tetragonal zirconia (t-ZrO2) transforms to its stable monoclinic form (m-ZrO2) upon application of stress. To achieve this desirable property it is important to retain a high volume fraction of t-ZrO2 at room temperature. In bulk synthesis this is accomplished by adding dopants, such as yttrium. Recently we have demonstrated that multilayer sputter deposition enables stabilization of tetragonal zirconia without the use of dopants.

Amorphous alumina layers were used as termination and restart surfaces for the polycrystalline zirconia layers, as well as an elastic constraint for the t → m transition which involves an anisotropic volume expansion. Double angle X-ray diffraction (XRD) was used to explore the deposition parameters under which t-ZrO2 is retained in the nanolaminate. The zirconia layer thickness was found to be the crucial parameter. The tetragonal phase was detected in all multilayers with ZrO2 layer thickness <20nm.
High-resolution Electron Microscopy characterization of chemically derived titanium aluminide nanomaterials
Authors: Pan Y.-M. , Paul P. P. , Schwab S. T.
Published: June 2020

Titanium aluminides are a class of intermetallics whose application to a variety of advanced structures may yield substantial improvements in system performance. Before titanium aluminides can realize their full potential, a number of deficiencies such as lack of ductility must be overcome through improved processing. Difficulties inherent in traditional methods have prompted the development of the ultrastructure approach to materials processing. Chemical processing has best potential for ultrastructure control because articles are constructed from atomic level up. The availability of nanostructured materials may be essential to the development of intermetallics with acceptable levels of ductility. The focus of this work is to use high resolution electron microscopy (HREM) techniques to characterize the structure and chemistry of the chemically-derived, nanocrystalline intermetallic powders that have potential to enable ultrastructure processing of advanced intermetallics and alloys.

In an attempt to produce salt-free TiAl3, a dilute hexane solution of Ti[N(SiMe3)2]3 was combined with an excess of (AIH3) at room temperature to yield a very fine, steel-gray powder.
Quantitative in situ hot-stage high-resolution Transmission Electron
Microscopy
Authors: Howe J. M.
Published: June 2020

In situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the dynamics of interfaces at the atomic level. Such information complements detailed static observations and calculations of interfacial structure, and is essential for understanding interface theory and solid-state phase transformations. This paper provides a brief description of particular requirements for performing in situ hot-stage HRTEM and illustrates the use of this technique to obtain quantitative data on the atomic mechanisms and kinetics of interface motion during precipitation of {111} θ phase in an Al-Cu-Mg-Ag alloy.

The specimen and microscope requirements for in situ hot-stage HRTEM are not much different from those of static HRTEM, except that one must have a heating holder and equipment for recording and analyzing dynamic images. At present, most HRTEMs are equipped with a TV-rate camera, possibly combined with a charge-coupled device camera. An inexpensive way to record in situ HRTEM images is to send the output from the TV-rate camera directly into a standard VHS format videocassette recorder (VCR).
Characterization of a monolayer graphitic structure
Authors: Lin X. , Wang X. K. , Dravid V. P. , Ketterson J. B. , Chang R. P. H.
Published: June 2020

For small curvatures of a graphitic sheet, carbon atoms can maintain their preferred sp2 bonding while allowing the sheet to have various three-dimensional geometries, which may have exotic structural and electronic properties. In addition the fivefold rings will lead to a positive Gaussian curvature in the hexagonal network, and the sevenfold rings cause a negative one. By combining these sevenfold and fivefold rings with sixfold rings, it is possible to construct complicated carbon sp2 networks. Because it is much easier to introduce pentagons and heptagons into the single-layer hexagonal network than into the multilayer network, the complicated morphologies would be more common in the single-layer graphite structures. In this contribution, we report the observation and characterization of a new material of monolayer graphitic structure by electron diffraction, HREM, EELS.

The synthesis process used in this study is reported early. We utilized a composite anode of graphite and copper for arc evaporation in helium.