bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Backthinned Ceramic Specimens
Authors: Fisher A. T. , Angelini P.
Published: June 2020

Analytical electron microscopy (AEM) of the near surface microstructure of ion implanted ceramics can provide much information about these materials. Backthinning of specimens results in relatively large thin areas for analysis of precipitates, voids, dislocations, depth profiles of implanted species and other features. One of the most critical stages in the backthinning process is the ion milling procedure. Material sputtered during ion milling can redeposit on the back surface thereby contaminating the specimen with impurities such as Fe, Cr, Ni, Mo, Si, etc. These impurities may originate from the specimen, specimen platform and clamping plates, vacuum system, and other components. The contamination may take the form of discrete particles or continuous films [Fig. 1] and compromises many of the compositional and microstructural analyses. A method is being developed to protect the implanted surface by coating it with NaCl prior to backthinning. Impurities which deposit on the continuous NaCl film during ion milling are removed by immersing the specimen in water and floating the contaminants from the specimen as the salt dissolves.
Microstructural Development in Nb-Ti Multifilamentary Superconductors During Processing
Authors: West A. W.
Published: June 2020

The influence of the filament microstructure on the critical current density values, Jc, of Nb-Ti multifilamentary superconducting composites has been well documented. However the development of these microstructures during composite processing is still under investigation.

During manufacture, the multifilamentary composite is given several heat treatments interspersed in the wire-drawing schedule. Typically, these heat treatments are for 5 to 80 hours at temperatures between 523 and 573K. A short heat treatment of approximately 3 hours at 573K is usually given to the wire at final size. Originally this heat treatment was given to soften the copper matrix, but recent work has shown that it can markedly change both the Jc value and microstructure of the composite.
Transmission Electron Microscopy of Superconducting A15 Compounds
Authors: Pande C. S.
Published: June 2020

Unlike many other branches of materials science, there have been relatively few applications of electron microscopy in the study and development of superconducting materials, the principal application being in the study of microstructure in ductile-superconductors such as Nb-Ti and Nb-Zr. However, in recent years this trend has changed, and TEM is now being applied to technologically important high transition temperature compounds with the A15 structure, e.g., Nb3Sn, Nb3Ge, V3Ga, V3Si. Main areas of study are the role of grain boundary structure and segregation on critical currents, nature of the radiation damage, and the possibility of directly imaging the flux line lattice. Analytical scanning transmission electron microscopy (STEM) is now increasingly being used to investigate the first two areas mentioned above. However, a direct imaging of flux line lattice remains the biggest challenge in this field. In this paper the author's studies of superconducting compounds using TEM are briefly reviewed.
HREM Studies of Interfaces in Zr02/Al203 Ceramics
Authors: Kraus S.
Published: June 2020

Because of its unusual mechanical and electrolytic properties, zirconia (Zr02) finds a wide variety of uses, such as refractories, oxygen sensors, heaters and extrusion dies. Zr02 exists in three polymorphic forms; the high temperature phase is cubic and is isostructural with CaF2 (fluorite); below 2350°C (in pure ZrO2 ), a tetragonally-distorted version of the fluorite structure exists. At still lower temperature, the tetragonal form (t-Zr02) transforms martensitically to a monoclinic structure (m-Zr02). This t→m transformation gives rise to the phenomenon of transformation toughening in ZrO2 -containing-ceramics, and thus provides ceramics with potential for high
TEM Observation of a Mechanically Thinned SiC Material
Authors: Plummer H. K. , Shinozaki S.E. , Juterbock B.N. , Williams R.M.
Published: June 2020

When SiC materials are sintered or heat-treated at 2100°C or higher, abnormal morphological development occurs, due to exaggerated grain growth, decomposition of SiC and of second phase zones. A detailed study of the graphite and other second phase formations is important to correlate the microstructure to mechanical properties of SiC materials at high temperature. Large graphite formations have been observed with SEM and optically, but confirmation of these second phase formations has been hindered due to preferential etching of these regions using normal ion beam thinning techniques. In addition, once a small hole is formed in the second phase regions, the hole is quickly blunted by the ion beam. In this study mechanical thinning equipment designed and built by us(2) has been used to prepare electron transparent specimens for TEM analysis.
TEM Study of Secondary Grain Boundary Dislocations in Near-∑13, Near-∑17 and Near-∑29 [001] Twist Boundaries in Gold
Authors: Babcock S.E.
Published: June 2020

In 1970, an extensive search by transmission electron microscopy (TEM) for evidence of ordered structure in high-angle [001] twist boundaries helped to establish the credibility of the DSC/CSL description of grain boundary structure. In this work, square grids of line contrast were found in boundaries for which the twist misorientation (Θ) was very near the special Σ5+ Σ13 and Σ17 Θ. The lines ran parallel to the primitive translation vectors (b(1) and b(2)) of the appropriate low-Σ DSC lattice, and their spacing correlated well with the spacing predicted by Frank's formula for dislocations with Burgers vectors b(1) and b(2). The images were interpreted as secondary grain boundary dislocation (SGBD) networks. Only for the near-Σ5 case was g•b analysis carried out to show that the line contrast was characteristic of b= 1/10 <310> type screw SGBD's.
Surface Plasmons: a Sensitive Diagnostic Tool for Characterizing Interfaces
Authors: Scheinfein M. R.
Published: June 2020

There has been considerable interest in characterizing the electronic and chemical properties of interfaces and grain boundries at high spatial resolution. This abstract describes a technique which utilizes the energy dispersion of surface plasmons in the transmission electron energy loss spectrum to evaluate the local dielectric constant variation across interfaces. This technique is shown to yield extremely high spatial resolution.

We have been conducting studies of interfaces in a VG HB-5 STEM located at NRRFSS which is equipped with a high resolution electron energy loss analyzer. In STEM, using small probes, a typical surface plasmon excited by 100 keV electrons (Al for example) reaches its asymptotic energy value at a scattering angle between.3 and.4 mr. Since we are convoluting the incident angular distribution with the surface plasmon intensities integrated over a collection aperture, the surface plasmon excitation energies are given by their asymptotic (in k-space) energy values. These asymptotic energy excitations are very sensitive functions of the thickness and dielectric constant [eg, 2-5] of the surrounding medium.
Transmission Electron Microscopy Studies of Aluminum Oxidation
Authors: Lee J.Y.
Published: June 2020

In the oxidation of metals and alloys, microstructural features at the atomic level play an important role in the nucleation and growth of the oxide, but little is known about the atomic mechanisms of high temperature oxidation. The present paper describes current progress on crystallographic aspects of aluminum oxidation. The 99.999% pure, polycrystalline aluminum was chemically polished and oxidized in 1 atm air at either 550°C or 600°C for times from 0.5 hr to 4 weeks. Cross-sectional specimens were prepared by forming a sandwich with epoxy, followed by mechanical polishing and then argon ion milling. High resolution images were recorded in a <110>oxide zone-axis orientation with a JE0L JEM 200CX microscope operated at 200 keV.
Analytical Electron Microscopy of Surface-Modified Ceramics
Authors: Sklad P. S.
Published: June 2020

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.

While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.
Computer Reconstructions of Normal Human Alveoli From Serial Sections
Authors: Parra Saundra C. , Burnette Ricky , Takaro Timothy
Published: June 2020

Portions of two adjacent normal human alveoli were reconstructed from serial sections in order to examine normal alveolar organization, including anatomical relationships among the different cell types, the connective tissue matrix and gaps in the alveolar septum. Computer reconstructions were prepared from montaged electron micrographs of serial sections. Rotation of these reconstructions in the x, y or z axes allowed examination of the alveoli from many different aspects other than the actual plane of sectioning. Anatomical relationships “between Type I and Type II epithelial cells, alveolar macrophages, and pores of Kohn that could not he deduced from a single plane of the section (random sections) were revealed.
Hardness and Microstructure Change During Annealing Process of a Modified Inconel-718
Authors: Hu Chen-Ti , Syu Yau-Tsurng
Published: June 2020

A modified Inconel 718 alloy with a higher content of Mo and lower was prepared from metals of electrolytic grade purity with a L-H IS 8/III vacuum induction melting furnace. The results of chemical analysis were shown in Table 1. After about 80 pet reduction in thickness with hot forging, material was then subjected to 1200°C solution treatment for one hour, air cool and 720°C ageing treatment for 16 hour, air cool. An uniformly dispersed γ’ and γ” precipitates was obtained.

Material was plastically deformed to 70 pet reduction in thickness by cold rolling treatment. Then all specimens were divided into four groups and annealed in salt baths with temperatures of 750°C, 850°C, 920°C and 1060°C, respectively. 850°C was chosen to conduct a complete investigation of interior microstructures of different time periods: (1) 2 sec (2) 5 sec (3) 10 sec (4) 30 sec (5) 1 min (6) 5 min (7) 10 min (8) 20 min (9) 35 min (10) 1 hr (11) 2hr. Hardness of all thermomechanically treated specimens were examined with a Rockwell Hardness machine, using RC and RB scales.
Dislocations Motion in Alloys with Periodic Antiphase Boundaries
Authors: Vanderschaeve G. , Faress A.
Published: June 2020

Plastic deformation of L12 ordered alloys (Cu3Au type) occurs by slip of dislocation pairs. In alloys with periodic APB's however, dislocations moving through the crystal are continually crossing APB's and mechanical properties of these alloys are affected by conditions governing the propagation of dislocations through them.

This paper describes some peculiarities of the interaction of moving dislocations with periodic APB's in a Cu 20.3at%Pd alloy, where the average distance between periodic APB's is Ma∼7.6a. The frequently observed configuration (Fig. 1) consisting of dislocation pairs followed by alternatively widely extended and unsplit unit dislocations can be understood if one analyzes the effective surface tension acting on each Shockley partial.
Energetic Cluster Ion Impacts on Carbon and Gold/Carbon Films
Authors: Ledbetter M.C. , Matthew M.W. , R.J. Beuhler  , Friedman L.
Published: June 2020

Mass analyzed beams of accelerated cluster ions have been used to study energy transfer processes on impact with solid surfaces. Singly-charged water molecule clusters containing between 20 and 150 water molecules and one proton have been accelerated to kinetic energies as high as 300 kV and collided with 10 nm films of carbon or carbon covered with 2 μg/cm2 evaporated gold. Alterations in the structure of these films have been studied by transmission electron microscopy.

Carbon films bombarded with water clusters of 25 and 100 molecules accelerated to 300 kV are shown in Fig. 1. The use of 100 water molecules produced craters about 7-8 nm in diameter and even 50 molecules produced craters about 1.5-2 nm in diameter; however, 25 molecules failed to produce any detectable alterations in the film. The bombardment of a gold-covered film by similar clusters is shown in Fig. 2. In these cases, gold grains were removed to form voids about 10-20 nm in diameter, even by the clusters as small as 25 molecules, which produced no craters in pure carbon.
A Novel Method of Immuno-Gold Staining For TEM and HVEM
Authors: Cohen-Gould Leona , Robinson Thomas F.
Published: June 2020

Advances in Immunochemistry allow for labelling of various tissue components with highly specific antibodies, that in turn may be labelled with marker substances such as flourescein for light microscopy, or any of a number of electron-dense substances, such as ferritin and colloldal gold, for localization with scanning and transmission electron miscroscopy. The methods used for transmission electron microscopy are designed to minimize damage to antigenic sites while preserving ultrastructure. The methods include embedding of the tissue in resins with low-temperature curing characteristics such as Polyethylene glycol (PEG) or Lowicryl K4M (Chemische Werke Lowl, F.R.G.). The tissue is embedded, sectioned, and mounted on grids. The Immuno-reactions are then carried out on these mounted sections.
The Use of Gach Technique in Stabilizing Biological Specimens For X-Ray Microanalysis
Authors: Gunning W.T. , Crang R.E.
Published: June 2020

An alternative SEM preparative technique is proposed for biological specimens in which cellular diffusible constituents may be retained that are otherwise lost during conventional specimen preparation involving critical point drying. The technique utilizes the copolymerization of glutaraldehyde with carbohy-drazide, and is designated “GACH”. Surface morphology with GACH preparations is as good as, or better than, that preserved using critical point drying. Bulk specimen preparation for elemental analysis has been limited heretofore to frozen-hydrated, freeze drying, freeze substitution, unfixed air dried, and critical point dried specimens. All such techniques offer particular advantages, but with certain limitations. The GACH technique is not being proposed as a superior routine replacement for present biological bulk specimen preparation methods, but rather as a viable alternative technique that allows both the retention of bound ions and acceptable surface morphology without elaborate instrumentation.
The Microscopy of Compatibility and Incompatibility in Ulmus
Authors: Redmond B. L. , Bob Christopher F.
Published: June 2020

The American Elm (Ulmus americana L.) has been plagued by Dutch Elm Disease (DED), a lethal disease caused by the fungus Ceratocystis ulmi (Buisman) c. Moreau. Since its initial appearance in North America around 1930, DED has wrought inexorable devastation on the American elm population, triggering both environmental and economic losses. In response to the havoc caused by the disease, many attempts have been made to hybridize U. americana with a few ornamentally less desirable, though highly DED resistant, Asian species (mainly the Siberian elm, Ulmus pumila L., and the Chinese elm Ulmus parvifolia Jacq.). The goal is to develop, through breeding efforts, hybrid progeny that display the ornamentally desirable characteristics of U. americana with the disease resistance of the Asian species. Unfortunately, however, all attempts to hybridize U. americana have been prevented by incompatibility. Only through a firm understanding of both compatibility and incompatibility will it be possible to circumvent the incompatibility and hence achieve hybridization.
Contrast Enhancement of Spermatozoa in Seminal Stains
Authors: Ward Dennis C. , Hall Robert W.
Published: June 2020

The localization and visualization of intact spermatozoa in dried stains confirms the presence of semen in cases of suspected rape. Even though the average human male ejaculate contains over 240 million spermatozoa, current searching methods are often inefficient and tedious. These methods include the light microscopic search for spermatozoa following either: extraction of the stain components in aqueous buffer, destruction of the stain substrate, or the in situ staining of the suspected area.

The extraction technique is most commonly employed even though it is inefficient in cell recovery. Spermatozoa apparently bind tenaciously to the support medium during the drying of the seminal plasma. The extraction process often fails in extracting complete cells. The number of spermatozoa collected from a stain may be further reduced by dilution of the semen with other body fluids, dilution of stain components with extraction medium, limited stain size, or a low sperm count due to physiological and/or elective (vasectomy) reasons.
Freeze-Fracture Imaging of Solutions of Ordered Rigid Rods
Authors: Zasadzinski J. A. N. , Sammon M. J. , Meyer R. B.
Published: June 2020

Solutions of rigid rods display orientational and/or positional order at appropriate concentrations. Model systems of rigid rods are formed by Tobacco Mosaic Virus (TMV) in water or dilute salt solutions. In pure water, TMV particles are strongly negatively charged and electrostatic repulsion orders the virus into three-dimensional crystals with both orientational and positional order. When salt is added to the system, electrostatic repulsion is screened and the TMV particles lose much of their positional order, but retain their orientational order and form a nematic liquid crystal phase.

The long and short-range order of TMV solutions is best studied using freeze- fracture replication TEM. Each virus, which is the equivalent of a single molecule in a normal crystal or liquid crystal, is easily visualized as a discrete particle (TMV are approximately 300 nm long and 18 nm in diameter).
Colloidal Gold Markers: Preparation and Cell Labeling for Transmission and Scanning Electron Microscopy
Authors: Molday Robert S.
Published: June 2020

Colloidal gold particles have become one of the most widely used markers to detect, localize and, in some cases, quantitate cell surface and intracellular antigens and receptors since their introduction as transmission electron microscopic (TFM) markers by Faulk and Taylor in 1971 and as scanning electron microscopic (SEM) markers by Horisberger et al. in 1975. This interest in colloidal gold markers for cell labeling is based on their versatile properties for detection under the electron microscope. Colloidal gold particles are highly electron-dense which enables them to be seen under the TEM in thin sections of heavily stained cells. They can be prepared in a wide range of highly uniform sizes for visualization at different magnifications and for multiple labeling studies. Under the SEM, gold particles emit a high quantity of secondary electrons, backscattered electrons and characteristic X-ray signals and as a result, with the appropriate detectors, they can be readily distinguished from cell surface structures having a similar morphological appearance. The successful application of colloidal gold particles as markers for TEM and SEM however requires (i) careful preparation and characterization of both the gold markers and the ligand (protein)-gold conjugates, (ii) utilization of specific labeling techniques employing necessary controls to confirm the specificity of labeling, and (iii) critical evaluation of results in relation to the conditions used in labeling. These aspects of gold labeling will be considered here. Additional information can be obtained from recent reviews dealing specifically with gold markers and more generally with cell labeling techniques.
Detection of Small (5-15 nm) Gold-Labelled Surface Antigens by Back- Scattered Electrons
Authors: Walther Paul , Müller Martin
Published: June 2020

In contrast to thin section transmission electron microscopy, scanning electron microscopy (SEM) permits “three dimensional” analysis of events occurring at the cell surface. Since it is now generally recognized that many important cellular functions are initiated and regulated via interactions taking place at the cell surface, SEM studies of surface antigens have become an area with increasing applications. Surface antigens have been visualized using antibody coupled phages, latex spheres, colloidal gold, i.e. markers that are recognized in the SEM either by their specific shape or because of their uniform size. An ideal marker, however, should be as small as possible to reduce the problems of sterical hinderance. All known markers smaller than approx. 15 nm (colloidal gold, ferritin) are round particles which in the secondary electron mode (SE) are hardly discerned from surface structures or contaminants of similar size. Therefore the markers must be amenable to verification using additional information such as backscattered electrons (BSE).
Ultrastructure of Bronchopulmonary Lavage Cells From B0vines Administered 3-Methylindole: III. 72 Hours Post-Treatment
Authors: Singh Amreek , Atwal Onkar , Eyre Peter
Published: June 2020

Introduction. It is well-documented that a morphologic analysis of free cells contained in the airways can contribute to the functional pathology of respiratory disease processes. The mechanism of certain lung conditions, for example, pulmonary edema and emphysema of bovines is known to a limited extent. We have studied the disease by means of 3-methylindole (MI), a rumen metabolite of L-tryptophan, which induces the pulmonary edema and emphysema in cattle. Ultrastructure of the bronchopulmonary lavage (BL) cells 72 hr following MI oral administration to calves is presented in this report. The 12 hr post-treatment results were described earlier.
Hepatic Glycogen Synthesis in Adrenalectomized Rats After Short- and Longterm Stimulation by Dexamethasone Observed by Light and Electron Microscopic Radioautography
Authors: Michaels J.E. , Garfield S.A. , Smith S.S. , Hung J.T. , Cardell R.R.
Published: June 2020

The effects on glycogen synthesis of short- and long-term stimulation with dexamethasone (DEX) were studied in adrenalectomized, overnight-fasted rats by light (LM) and electron microscopic (EM) radioautography (RAG). Rats were injected with DEX 3 hr (short-term) or 14 hr (long-term) prior to labeling by intravenous injection of 2 mCi 3H-galactose, a glycogen precursor. Liver was prepared for LM and EM RAG by routine procedures.

Short-term rats were sacrificed 1, 6 and 12 hr after labeling. One hr after injection of label (Fig. 1) equal percentages (44%) of heavily (> 10 grains/100 μm2 hepatocyte cytoplasm) and lightly (<10 grains/100 μm2 cytoplasm) labeled hepatocytes were evident. Six hr after labeling, heavily labeled cells increased slightly as labeled and unlabeled glycogen became evident. The appearance of unlabeled glycogen was evidence that glycogen synthesis continued between 1 and 6 hr, as circulating label fell to a level below that necessary for radioautographic labeling to occur. Twelve hr after labeling (Fig. 2) the percentage of heavily labeled hepatocytes (31%) decreased to less than at one hour as unlabeled glycogen increased. These results indicated that although glycogen synthesis had continued, some loss of label had occurred.
Blood/Material Interactions on Silicone Rubber-Hydrogels
Authors: Greer R. T. , Schwen K. , Cyr M. , McAllister P. , D. T. Zhang
Published: June 2020

The composition and structure of a polymer surface in contact with flowing blood are major factors determining the extent of thrombus and embolus formation. Use of scanning electron microscopy (SEM) provides temporal information on morphology of thrombi and cells on polymer surfaces exposed to blood, and associated Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) measurements aid in characterizing protein buildup.

Medical grade silicone rubber-filler formulations (0,2,12 and 24 weight percent cristobalite filler contents; source material Silastic 382) were polymerized to form substrates. These were subsequently coated with five different hydrogels by radiation grafting (y-rays) to provide samples with a range of hydrophilicity characteristics.
Perineurium: Ultrastructure in Rodent and Fowl Peripheral Nerves
Authors: Uzmari Betty G. , Irish Pati S. , Villegas Gloria M.
Published: June 2020

Ultrastructural characteristics of perineurium have been compared in mouse, Japanese guail (Coturnix coturnix) and chicken peripheral nerves - median, ulnar, peroneal and tibiai. Certain features are noteworthy. In nerves of the sizes studied in ail 3 species, nerve fiber bundles are separated from epirieurium by a multi-layered perineurium composed of alternating perineurial cells and collagenous matrix, with quail perineurium exhibiting complex cellular interdigitatious that breach the matrix to connect successive layers of cells. Tight junctions are more extensive and numerous in mouse than in fowl and are rare in quail. Pinocytotic vesicles are abundant along cell surfaces and in cytoplasm of perineurial cells and collagen fibrils of perineurium are thinner than those of epirieurium in all 3 species. Basal lamina and extracellular matrix vary in electron density and amount: coturnix nerves exhibit a dense, amorphous extracellular matrix which often obscures the basal laminae, whereas the basal laminae of the mouse perineurial cells are quite distinct with the amorphous matrix present in lesser amounts and with less electron density.
Fluorescent and Immuno-Electron Microscopy of Detergent Extracted Cytoskeletal and Associated Antigens
Authors: Basgall E.J. , Soong M.M. , Tompkins W.A.F.
Published: June 2020

Triton X-100 detergent extraction has been shown to be a relatively simple method for revealing the internal architecture of cultured cells. This method has proven valuable in studies of cytoskeleton-associated proteins and their functions in regulating cell activities. Exposed cytoskeletal elements can be examined using either transmission or high-resolution scanning electron microscopy. Immunochemical studies at the electron microscopic level have been simplified by the availability of Protein A-colloidal gold as a high affinity marker for immunoglobulins, specifically IgG.

Several investigators have reported an association between the cytoskeleton and viral antigens. Evidence has indicated that, in some systems, the cytoskeleton plays a significant role in virus infection. Immunofluorescent studies on canine distemper virus infected, extracted cells have revealed altered cytoskeletal staining patterns, as compared to non-infected controls. In our laboratory, immuno-electronmicroscopy studies of extracted NIH/3T3 cells infected with Maloney-murine leukemia virus have indicated an association between cytoskeletal actin and the viral antigens gp70 and pl5E.
Morphological Characterization of the Vestibular Nerve
Authors: Fermin C. D. , Igarashi M.
Published: June 2020

One of the goals of our research is to understand the mechanisms of vestibular compensation following labyrinthectomy; a surgical procedure used to alleviate vertigo and dizziness. Labyrinthectomy involves obliteration of the vestibular end organs with subsequent severance to the peripheral dendrites of the vestibular nerve. The nerve degenerates toward the brain, but subjects usually compensate for the deficit. Since behavior has an underlying anatomical counterpart, we are characterizing the normal and pathological vestibular system of this primate morphologically. Normal values are used to properly evaluate the morphological appearance of operated specimens. Correlations between morphological appearance of pathological specimens and behavioral performance postoperatively will allow us to evaluate some aspects of the vestibular compensatory process.
A Scanning Electron Microscope Study of Mature Aspergillus Flavus Sclerotia
Authors: Neck K.F. , Stack J.P. , Neck J.S. , Caceci T.
Published: June 2020

Raw or processed foodstuffs contaminated with the mycotoxin-producing fungus Aspergillus flavus Link ex Fries may present serious health hazards to humans and animals. Practices aimed at reducing A. flavus contamination of food and feed are being developed. These attempts would be facilitated by an understanding of the life cycle and the survival of the fungus. The formation of sclerotia in culture or on plant tissue by several isolates of A. flavus prompted this morphological study. Sclerotia are broadly defined as aggregations of vegetative hyphae of determinate growth that are capable of surviving adverse environmental conditions. To our knowledge, this is the first SEM study of the sclerotia of A. flavus.
Ultrastructural Observations on Microspore Development in Rice Anther Culture
Authors: Ren S. S. , Chen J. C. , Chen Y. R.
Published: June 2020

The plants produced from rice anther culture varied in ploidy level. Genetic analysis of anther-derived plants indicated genome multiplication occurred in microspore development in vitro. Cytological studies on early roicrospore division suggested endoreduplication and nuclear fusion may be related to the production of nonhaploid plants. In the present study, fine structures of callus ontogeny in anther culture were emphasized.

Anthers of rice(Oryza sativa L. c. v. Hsinchu 4, 2n=24) containing mid-uninucleate microspores were excised and cultured in Ng liquid medium, supplimented with 60 g/l sucrose, 1 mg/l kinetin and 2 mg/l naphthalenacetic acid. Cultured anthers were collected at 2 days intervals for 20 days and fixed in 2.5% glutaraldehyde in 0.1M cacodylate buffer(pH=7.0), postfixed in osmium tetraoxide, and then embedded in Spurr's resin. Thin sections were stained with uranyl acetate and lead citrate, observed under Hitachi H-600 at 75 KV.
Ultrastructure of Baboon Zygotes Produced By Microinjection of Spermatozoa
Authors: Caceci T. , Shaikh A.A. , Kraemer D.C.
Published: June 2020

Five baboons were treated during seven menstrual cycles with 5.0 mg of FSH-P for five days, starting on either day 3 or day 5 of the cycle. On day 5 of the treatment, the ovaries were examined by laparoscopy to evaluate follicular development. All animals exhibited multiple preovulatory follicles and at that time 100 mg GnRH was administered intramuscularly to induce LH release. Between 24 and 30 hours after injection of GnRH, laparoscopic follicular aspiration was used to collect oocytes. These were matured in vitro (determined by extrusion of the first polar body) and fertilized by microinjection with frozen-thawed baboon spermatozoa. Male and female pronuclei were observed in 32% of the resulting zygotes within 24 hours. These zygotes were compared to a zygote in the same stage that had been fertilized in vivo and obtained by laparoscopy and flushing of the oviduct.
Ultrastorcture of Cerebellar Purkinje Cells in Rats Subjected To Partial Global Cerebral Ischemia
Authors: Dimlich R.V.W. , Biros M.H.
Published: June 2020

In severe cerebral ischemia, Purkinje cells of the cerebellum are one of the cell types most vulnerable to anoxic damage. In the partial (forebrain) global ischemic (PGI) model of the rat, Paljärvi noted at the light microscopic level that cerebellar damage is inconsistant and when present, milder than in the telencephalon, diencephalon and rostral brain stem. Cerebellar injury was observed in 3 of 4 PGI rats following 5 minutes of reperfusion but in none of the rats after 90 min of reperfusion. To evaluate a time between these two extremes (5 and 90 min), the present investigation used the PGI model to study the effects of ischemia on the ultrastructure of cerebellar Purkinje cells in rats that were sacrificed after 30 min of reperfusion. This time also was chosen because lactic acid that is thought to contribute to ischemic cell changes in PGI is at a maximum after 30 min of reperfusion.
Alterations in Ultrastructure of Skeletal Muscle From Newborn Guinea Pigs Following in Utero Exposure to Ethanol
Authors: Uphoff C. , Nyquist-Battie C. , Cole T.B.
Published: June 2020

Ultrastructural alterations of skeletal muscle have been observed in adult chronic alcoholic patients. However, no such study has been performed on individuals prenatally exposed to ethanol. In order to determine if ethanol exposure in utero in the latter stages of muscle development was deleterious, skeletal muscle was obtained from newborn guinea pigs treated in the following manner. Six Hartly strain pregnant guinea pigs were randomly assigned to either the ethanol or the pair-intubated groups. Twice daily the 3 ethanol-treated animals were intubated with Ensure (Ross Laboratories) liquid diet containing 30% ethanol (6g/Kg pre-pregnant body weight per day) from day 35 of gestation until parturition at day 70±1 day. Serum ethanol levels were determined at 1 hour post-intubation by the Sigma alcohol test kit. For pair-intubation the Ensure diet contained sucrose substituted isocalorically for ethanol. Both food and water intake were monitored.
Observation of pseudo 10-fold symmetry in the ordered iron-zinc delta phase
Authors: Giannuzzi L. A. , Ramani A. S. , Howell P. R. , Pickering H. W. , Bitler W. R.
Published: June 2020

The δ phase is a Zn-rich intermetallic, having a composition range of ∼ 86.5 - 92.0 atomic percent Zn, and is stable up to 665°C. The stoichiometry of the δ phase has been reported as FeZn7 and FeZn10 The deviation in stoichiometry can be attributed to variations in alloy composition used by each investigator. The structure of the δ phase, as determined by powder x-ray diffraction, is hexagonal (P63mc or P63/mmc) with cell dimensions a = 1.28 nm, c = 5.76 nm, and 555±8 atoms per unit cell. Later work suggested that the layer produced by hot-dip galvanizing should be considered as two distinct phases which are characterized by their morphological differences, namely: the iron-rich region with a compact appearance (δk) and the zinc-rich region with a columnar or palisade microstructure (δp). The sub-division of the δ phase was also based on differences in diffusion behavior, and a concentration discontinuity across the δp/δk boundary. However, work utilizing Weisenberg photographs on δ single crystals reported that the variation in lattice parameters with composition was small and hence, structurally, the δk phase and the δp phase were the same and should be thought of as a single phase, δ. Bastin et al. determined the average cell dimensions to be a = 1.28 nm and c = 5.71 nm, and suggested that perhaps some kind of ordering process, which would not be observed by x-ray diffraction, may be responsible for the morphological differences within the δ phase.
Defect structures of Nb1+αS2 sulfidation scales
Authors: Zhou Chuxin , Hobbs L. W.
Published: June 2020

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.

Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.
Analytical Electron Microscopy of rapidly solidified Pt-Co-B alloys
Authors: Wittig J.E. , Qiu N. , Evans N.D.
Published: June 2020

Compared to binary Pt-Co materials, the ternary Pt42Co45B13 (at.%) alloy exhibits major improvements in hard magnetic behavior. Although rapid solidification processing (RSP) of the Pt-Co-B alloy is necessary to produce a refined distribution of the boron, this RSP condition does not constitute a strong magnetic material. To achieve the optimum hard magnetic properties requires subsequent annealing steps. Upon annealing the RSP ternary alloy, boron combines with Co to form magnetically anisotropic Coborides and the presence of boron has been observed to increase the rate of the transformation from the disordered FCC Pt-Co phase to the L1o superlattice. Understanding these phase transformations and their influence on the magnetic properties demands characterization of both the metastable RSP and annealed conditions.
HREM study of crystal-amorphous transformation of Cu-Ti multilayers by cold-rolling
Authors: Chiou W. A. , Lin C. S. , Meshii M.
Published: June 2020

Amorphous alloys have been of scientific interest for more than three decades because of their improved properties (physical, mechanical, magnetic, corrosion, etc.) as compared with those of the same alloys in the crystalline states. Recently, solid-state reactions have been shown to be a potential technology for synthesis of amorphous metallic alloys. While different mechanisms of amorphization have been proposed, the real process is still in debate. To study the amorphization process in more detail, information of structural transformation from crystalline to amorphous states during the processing (e.g., mechanical alloying) is essential. This paper presents an interfacial study of Cu and Ti foils by cold-rolling.
Precipitation at α/γ interfaces in duplex stainless steel
Authors: Burke M.G. , Kenik E.A.
Published: June 2020

Duplex (austenite/ferrite) stainless steels are used in a variety of applications in the nuclear industry, particularly for coolant pipes, valves and pumps. These materials may become embrittled after prolonged ageing in the temperature range ∼350 - 550°C due to precipitation of G-phase, an FCC-based Ni silicide, and the formation of a Cr-rich α' phase in the ferrite. In addition to the intragranular G-phase precipitates, preferential precipitation of other phases is often observed at grain boundaries, particularly α/γ interfaces. In this examination, the precipitates formed in a Nb-containing duplex stainless steel have been identified using analytical electron microscopy.
FEG - TEM: The route to HREM
Authors: Coene W. , de Jong A.F. , Lichte H. , Op de Beeck M. , Tietz H. , Van Dyck D.
Published: June 2020

Several technological improvements in TEM have nowadays been realized which offer possibilities for ultra-high resolution electron microscopy at intermediate voltages. These improvements include new objective lens polepieces, field emission gun (FEG) TEMs and slow-scan CCD camera's. A project has been initiated for the period 1990-1994, for the development of ultra-HREM, which combines know-how both from industry (Philips, Tietz) and university (Antwerp, Tübingen, Delft, Arizona). The project is partly sponsored by the European Community (Brite-Euram program nr. 3322). The goal of the project is to achieve 0.1 nm structural resolution by using the information limit rather than the point resolution of the instrument. The information limit is extended towards the 0.1 nm range (at 300 kV) by the much better spatial and temporal coherence of the FEG as compared with LaB6 sources.
Structures and defects identified by dark-field HREM
Authors: Zhang J.P.
Published: June 2020

The tilted illumination dark field high resolution imaging technique was applied to structures and defects of semiconductors and superconductors. We used a Hitachi-H9000 top entry microscope with a high resolution pole-piece of Cs=0.9 mm, operated at 300 Kv. Proper apertures, tilting angle and imaging conditions were chosen to minimize the phase shift due to aberrations. Since the transmitted beam was moved outside the aperture, the noise ratio was greatly reduced, which resulted in a significant enhancement of image contrast and apparent resolution. Images are not difficult to interpret if they have a clear correspondence to structure - information from image simulations in bright field mode can be used to assist in dark field image interpretation.

An example in a semiconductor, GaAs/Ga0.49In0.51P2 superlattice imaged along [110] direction is shown in Figure 1. In this dark field image the GaAs and GaInP layers can be easily distinguished by their different contrast, and the difference in quality between both sides of interfaces is clear. An enlarged image in Figure 1 shows the defective area on the rough side of interface. Since this image shows the same pattern as the [110] projection of an fee structure, the major structural information about {111}, {200}, {220} planes can be obtained from this zone. Note that in bright field mode, [110] is not a good zone for imaging such multilayers.
Use of EDS mapping to characterize thermochemical stability of fibers in intermetallic matrix composites
Authors: Porter John R.
Published: June 2020

New ceramic fibers, currently in various stages of commercial development, have been consolidated in intermetallic matrices such as γ-TiAl and FeAl. Fiber types include SiC, TiB2 and polycrystalline and single crystal Al2O3. This work required the development of techniques to characterize the thermochemical stability of these fibers in different matrices.

SEM/EDS elemental mapping was used for this work. To obtain qualitative compositional/spatial information, the best realistically achievable counting statistics were required. We established that 128 × 128 maps, acquired with a 20 KeV accelerating voltage, 3 sec. live time per pixel (total mapping time, 18 h) and with beam current adjusted to give 30% dead time, provided adequate image quality at a magnification of 800X. The maps were acquired, with backgrounds subtracted, using a Noran TN 5500 EDS system. The images and maps were transferred to a Macintosh and converted into TIFF files using either TIFF Maker, or TNtolMAGE, a Microsoft QuickBASIC program developed at the Science Center. From TIFF files, images and maps were opened in either NIH Image or Adobe Photoshop for processing and analysis and printed from Microsoft Powerpoint on a Kodak XL7700 dye transfer image printer.
The microstructure of an oxidized γ-TiAl+Cr alloy
Authors: Sutliff J.A. , Huang S.C. , McKee D.W.
Published: June 2020

Alloys based on the intermetallic phase γ-TiAl are considered good candidates for some high temperature aircraft engine applications. While a tremendous effort has been made to understand the mechanical properties of γ-TiAl, relatively little effort has been made to understand its oxidation behavior. Two of the authors have studied oxidation of several γ-TiAl alloys containing ternary and quaternary additions including Cr, Mn, Nb, Ta, and W. In this paper, we present some of the microstructural observations on an oxidized γ-TiAl alloy.

An oxidized γ-TiAl alloy with a nominal composition of 50 at% Al and 2 at% Cr was examined using analytical electron microscopy. Oxidation of polished pieces occurred in air at 850°C for 6 hours. The pieces were ground from the unpolished side to a thickness of ∼75 μm and 3 mm disks were punched. The disks were electropolished in a perchloric/methanol solution. Electropolishing was done from the metal side only until “perforation” of the metal substrate. This resulted in a sample with an oxide ‘window’. The samples were further thinned by ion beam milling (5kV/500μA Ar+) from the oxide surface toward the oxide/metal interface. The sample was examined in a Philips EM430 TEM operated at 300 kV and x-ray spectra collected with an EDAX energy dispersive x-ray spectrometer having a windowless Si(Li) detector.
An atom-probe field ion-microscope investigation of γ-γ' interfaces in a model nickel-based superalloy
Authors: Jayaram Raman , Miller M.K.
Published: June 2020

Nickel-based superalloys are of great technological interest because of their attractive mechanical properties at high temperatures. Their ability to maintain high strength under extreme conditions of thermal cycling makes them highly suitable for applications such as turbine blade material for aircraft engines. Single crystal nickel-based superalloys containing refractory elements such as Mo, Ta and Re have received considerable attention on account of their high creep strength at elevated temperatures. In these materials, the Ll2-ordered γ' phase is initially present as discrete cuboids in the disordered γ matrix. During high temperature creep, with the stress applied along the <100> direction, these cuboids directionally coarsen to form continuous γ' lamellae perpendicular to the applied-stress axis. The improvement in creep strength that occurs as a result of this change in the γ' morphology has been attributed to a number of different possible mechanisms. One mechanism suggested is the segregation of molybdenum to the γ-γ' interface which could impede dislocations producing increased creep strength.
Microstructure and properties of Al-Cu-Li-Ag-Mg-Zr alloy
Authors: Kim M.J. , Lee C.S. , Catalano M. , Shin K.S.
Published: June 2020

Weldalite™ 049 is an ultrahigh strength weldable Al-Cu-Li based alloy containing minor amounts of Ag, Mg and Zr, developed at Martin Marietta. Additions of Ag and Mg seem to stimulate precipitation in this alloy, but the exact role of these elements in promoting the precipitation of strengthening phases is as yet unclear. In this paper, we report the characteristic microstructure of the Weldalite™ 049 alloy in the near peak aged T8 temper condition and its effect on the measured tensile properties of this alloy.

The alloy used in this study was prepared by the Reynolds Metals Company. Measured alloy composition was Al-4.36 Cu-1.25 Li-0.39 Mg-0.35 Ag-0.14 Zr (wt.%). Tensile tests were performed at both room and cryogenic temperatures. The samples for TEM observations were cut from the mechanical testing specimens and then thinned to electron transparency by polishing and ion milling. Liquid nitrogen cooled specimen holder was used for ion milling to avoid local specimen heating. Diffraction contrast and tilting experiments were performed at 200kV in a JEM-2000FX. HREM was done in an ISI-002B at 200kV, with an interpretable resolution limit of 0.18 nm.