bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Specimen Preparation Using Microwave Energy
Authors: Baldwin F. , Diocee M.S.
Published: June 2020

In recent years the feasibility of using microwave energy to fix tissue and expedite histologic staining has been tested. The technique has proven to be particularly valuable for shortening staining time of light microscopy preparations', thus enabling more rapid diagnosis which may be critical to patient care.

Rapid preparation of tissue for electron microscopy is often desirable in diagnostic ultrastructural pathology but with techniques commonly in use several hours may elapse before epoxy resin blocks reach a consistency suitable for ultrathin sectioning.

In this laboratory, microwave energy has been used to polymerise epoxy resin and the usefulness of the technique has been evaluated.

Kidney, liver and lung from male Wistar rats were fixed in phosphate buffered glutaraldehyde, cacodylate buffered glutaraldehyde and universal fixative.
A Polytungstate as a Potential Label For Electron Microscopy
Authors: Varkey Jacob , Beer Michael , Keana John F. W. , Ogan Marc
Published: June 2020

Many important structural problems in biology can be approached if particular components in an assembly can be labeled with a reagent that is detectable in an electron microscope. The development of the high resolution STEM, able to image single heavy atoms, raised the possibility of using individual atoms as labels. However, the imaging of single atoms requires very high dosages which are damaging to the specimen. To avoid this the undecagold cluster compound was introduced by Bartlett et al. (1978).
Rapid Processing for Diagnostic Electron Microscopy Using an Epon Replacement-Embed 812
Authors: Woods William J. , Ucci Angelo A.
Published: June 2020

Shortened turnaround time is a definite advantage in a diagnostic laboratory. It has been our experience that following a good initial fixation we can and do routinely rapid process our biopsies and surgical specimens for electron microscopic study. Surgical residents and consulting hospital personnel are instructed to send to our laboratory 1-2mm slices of appropriate areas of tissue (not necrotic) in Trumps 4CF-IG fixative. Specimens can be held in this solution without appreciable loss of ultrastructural detail until we can process them further. The processing schedule is listed below.

The specimen after at least 15 minutes in fixative is minced into cubes, slightly smaller than 1mm on a side, and processed according to the following shortened time schedule.
An Isolated Cytoskeletal Framework From Reticulomyxa: A New Model System For Intracellular Transport
Authors: Koonce Michael
Published: June 2020

Pharmacological and correlative light and electron microscopic studies suggest that the two major cytoskeletal systems, the microtubules (MTs) and microfilaments (MFs), are involved in the directed transport of intracellular organelles. However, the details of organelle-cytoskeletal interactions and force generation are not known, nor is it clear whether transport is solely a MT or MF-based phenomenon, a coordinated effort, or if each system supports different classes of motility. Here I describe an isolated cytoskeletal “framework” derived from an unusual species of freshwater amoeba that provides a model system in which to examine these questions. We are intending to use this preparation to study the interactions with and movement of both isolated native and artificial organelles.
Ultrastructural Kinetics of Electrically Induced Fusion of Human Erythrocytes
Authors: Stenger D.A.
Published: June 2020

Conditions for electrical breakdown and subsequent fusion of biological membranes have been reported for a variety of eukaryotic cell systems. Large fusion yields may be obtained by first causing cells to form pearl chains parallel to the electric flux lines in a high frequency a.c. field by a process known as dielectrophoresis. The dielectrophoretic force affords close positioning of the cells and facilitates maintenance and expansion of intercellular membrane and cytoplasmic contiguity initiated by one or more sharp square pulses directed through the pearl chains. Reversible disruption of the cell membrane occurs when the compressive electrical force caused by the square pulse exceeds a critical value.

This investigation focused on elucidating the ultrastructural kinetic mechanism(s) involved in the electrically-induced fusion of human erythrocytes. In this case, rapid freeze copper sample holders for freeze-fracture were incorporated as electrodes into a circuit capable of performing the type of protocol described above (Fig. 1). Washed human erythrocytes were suspended in 0.3 M sucrose containing 25.7 μm latex beads for electrode separation.
Is Smooth Endoplasmic Reticulum Involved in Hepatic Glycogen Synthesis in the Fetal Mouse?
Authors: Breslin Joanette S. , Robert R. Cardell
Published: June 2020

Considerable evidence suggests that hepatic smooth endoplasmic reticulum (SER) functions in both glycogen deposition and depletion and is closely associated with glycogen particles during both processes in the adult rodent liver. In this study we have investigated the time course of hepatic glycogen deposition and examined the association of SER with glycogen particles during fetal glycogen synthesis, i.e., from day 15 to day 19 of gestation (plug day = day 1).

Livers were removed from fetal ICR mice and processed for either light (LM) and electron microscopy (EM) or biochemical determination of glycogen. Biochemical analysis of glycogen concentrations in each liver revealed an average of 0.1% glycogen in day 15 and day 16 fetal livers, 0.6% in those from day 17, 2.0% on day 18 and nearly 5.0% by day 19. Light microscopic analysis of periodic acid-Schiff (PAS) stained semi-thin (1.0μm) sections confirmed the presence of increasing amounts of glycogen beginning on day 16 and reaching a maximum on day 19 of gestation.
SEM Observations on the Germination of Euonymous Americanus
Authors: Hill D.R. , McCurry J.R. , Elliott L.P. , Howard G.
Published: June 2020

Germination of Euonymous americanus in the laboratory has previously been unsuccessful. Ability to germinate Euonymous americanus. commonly known as the american strawberry bush, is important in that it represents a valuable food source for the white-tailed deer. Utilizing the knowledge that its seeds spend a period of time in the rumin fluid of deer during their dormant stage, we were successful in initiating germination. After a three month drying period, the seeds were placed in 25 ml of buffered rumin fluid, pH 8 at 40°C for 48 hrs anaerobically. They were then allowed to dry at room temperature for 24 hrs, placed on moistened filter paper and enclosed within an environmental chamber. Approximately four weeks later germination was detected and verified by scanning electron microscopy; light microscopy provided inadequate resolution. An important point to note in this procedure is that scarification, which was thought to be vital for germination, proved to be unnecessary for successful germination to occur. It is believed that germination was propagated by the secretion of enzymes or prescence of acids produced by microorganisms found in the rumin fluid since sterilized rumin failed to bring about germination.
Extracellular Cylindrical Rod Structures in a Sparganum, Tape Worm Larva, of Human Host Origin
Authors: Sun C. N.
Published: June 2020

Banded and laminated structures have been reported in human and animal tissues in the extracellular space. To my knowledge, extracellular cylindrical laminated rod structures have not been previously reported in the animal tissues. In the study of a sparganum (spirometra Sp) this unusual structure was found.

A sparganum in a nodule from the outer aspect of the right thigh of a 30 year old male in Arkansas has recently been described which is believed to be either S. mansonoides or S. mansoni. The worm, which was 90 mm long and 1 mm wide, was fixed in neutral buffered formalin and post-fixed with buffered 2 percent osmium tetroxide. The tissues were then dehydrated in serially increasing concentrations of ethanol and embedded in Epon 812. Sections were stained with uranyl acetate and lead citrate.
Isolation, Electron Microscopy, and Computer Processing of Chromosomes
Authors: Mazzone H.M.
Published: June 2020

Computer processing of electron microscope images has been of great value in the delineation and correlation of structural characteristics. An appropriate system for such study is that which enhances the high spatial frequency components in an image, thereby assisting in the observation of its fine structure. The present study reports on the isolation of intact chromosomes from a mammalian cell culture and their examination in the transmission electron microscope. The images of the chromosomes were then enhanced by computer processing.

Isolation of the chromosomes and their examination in the electron microscope was done in the Dept, of Biology of the Massachusetts Institute of Technology. A mammalian cell line, STR-T, was maintained under standard conditions. Fresh cultures were prepared and when the cells were in log phase, colchicine was added to arrest the chromosomes at metaphase. After chemical fixation with ethanol-acetic acid (3:1), the cells were mechanically dislodged by scraping the vessel surface with a rubber policeman. The cells were place in a test tube and gently homogenized by hand.
The Effect of Benzene on Bluegill Olfactory Lamellae
Authors: Mattie D.R. , Fisher J.W.
Published: June 2020

Jet fuels such as JP-4 can be introduced into the environment and come in contact with aquatic biota in several ways. Studies in this laboratory have demonstrated JP-4 toxicity to fish. Benzene is the major constituent of the water soluble fraction of JP-4. The normal surface morphology of bluegill olfactory lamellae was examined in conjunction with electrophysiology experiments. There was no information regarding the ultrastructural and physiological responses of the olfactory epithelium of bluegills to acute benzene exposure.

The purpose of this investigation was to determine the effects of benzene on the surface morphology of the nasal rosettes of the bluegill sunfish (Lepomis macrochirus). Bluegills were exposed to a sublethal concentration of 7.7±0.2ppm (+S.E.M.) benzene for five, ten or fourteen days. Nasal rosettes were fixed in 2.5% glutaraldehyde and 2.0% paraformaldehyde in 0.1M cacodylate buffer (pH 7.4) containing 1.25mM calcium chloride. Specimens were processed for scanning electron microscopy.
From Frozen Section to HVEM: Prospects For Enhanced Pathologic Characterization of Single Invading Cells With Ultrastructural Information
Authors: Vernon King Murray , Parsons Donald F.
Published: June 2020

Identification of single cells in frozen sections of tissue in the light microscope (LM) with subsequent reprocessing for examination in the high-voltage electron microscope (HVEM) for ultrastructural characterization offers an expedient route for studying such processes as the dissemination of cancers by single-cell invasion. The HVEM combines a high resolution that enables more certain identification of a cell and assessment of its activity at the instant of fixation with the convenience of an allowed thickness range (0.25-2.0 μm) close to that employed by the pathologist using the LM.

Employment of frozen sections allows adequate ultrastructural preservation, while at the same time enabling recognition of specific cell types by immuno-histochemistry or enzyme histochemistry. Only very brief aldehyde fixation is required—about four minutes. After reembedding, tissue containing marked cells is dissected out for reprocessing for the HVEM. Ultrastructural examination in turn enables more detailed identification and characterization of cell types. The LM staining process is illustrated with results from immuno-histochemical recognition of single invading squamous carcinoma cells in head-and-neck cancer.
Nanosecond Exposure Time Soft X-Ray Contact Imaging
Authors: Rosser R. J.
Published: June 2020

Soft x-ray contact microscopy has been pursued for many years because of the potential advantages of 1 to 10 nm electro-magetic radiation for imaging biological materials. These are the lower damage and greater penetration than electrons and considerably higher resolution than visible light microscopy, both possible without exotic optics.

The technique is similar to contact printing. The object to be viewed is placed as close as possible to the recording medium which is then exposed to a suitable x-ray source.. The sample is removed from the recording medium which is then chemically developed. The result is map of the x-ray opacity of the original specimen.

The high resolution has only become reality in recent years with the use of x-ray photo-resists as the recording material. These were origionally developed for use in the electronics industry but have been used for contact images of biological material.
Experimental Absorption Coefficients of Resists and Biological Materials
Authors: Shinozaki D.M. , Cheng P.C. , Tan K. , McGowan J. Wm.
Published: June 2020

The technique of soft x-ray contact imaging involves irradiating a polymer resist (the image recording medium) through a specimen with a microstructure of interest. The x-ray flux transmitted through the specimen is attenuated by the constituents of the microstructure, and the polymer resist and biological component and tissue suffer varying amounts of radiation damage. The amount of radiation damage in the resist depends on the absorbed energy and therefore is a function of the absorption coefficient of the resist and the flux incident on the resist. An understanding of the image formed in the resist, and the use of images for microchemical analysis depends on a quantitative measurement of absorption coefficients of both the resist and biological materials. It is possible to estimate the absorption behavior of materials using data from experiments on the gas phase of nitrogen, oxygen, etcetera. However direct measurements are particularly necessary near absorption edges such as at the carbon K edge where chemical effects are significant, and towards the long wavelength side of the soft x-ray region where the radiation damage mechanism is strongly affected by the molecular structure.
Scanning Electron Microscopy of Trophozoites of Naegleria Species
Authors: Lattyak M. , Cabral G. , Marciano-Cabral F.
Published: June 2020

The genus, Naegleria, includes four species of amebae which are either free-living or opportunistic pathogens. Naegleria fowleri, is the causative agent of Primary Amebic Meningoencephalitis, a rare but almost always fatal disease in man. Naegleria australiensis is an environmental isolate which is moderately pathogenic in mice. Naegleria lovaniensis and Naegleria gruberi are nonpathogenic environmental isolates. The four species were examined by scanning electron microscopy in order to determine whether membrane surface extensions, called food cups, could be correlated to pathogenicity. Food cups have been previously identified on the surface of Entamoeba histolytica and N. fowleri. It has been suggested that the food cups or stomas, are associated with internationalization of liquid and particulate components.
Surface Changes in Vaginal Epithelial Cells During Persistent Estrous Rats
Authors: Francis K. Khosho , Robert C. Kaufmann , Kofi S. Amankwah
Published: June 2020

Light exerts a major influence on the reproductive functions of the female rat, and the presence of constant light results in an aberrant vaginal cycle, leading to infertility associated with polycystic ovary (PCO) syndrome. In the present communication, we have utilized scanning electron microscopy (SEM) to study changes on the surface epithelium of persistent estrous (PE) rats with PCO.

Sprague-Dawely female rats were exposed to constant light for 50-150 days according to protocol that has been previously described. Rats in normal estrous, as determined by vaginal smears, were used as controls. Nembutal- anesthesized rats were perfused through the aorta with 2.5% gluteraldehyde in 0.1M sodium cacodylate buffer (pH 7.3). The mucosa of the upper third of the vagina from PE and control rats were microdissected, processed for SEM studies by a modified 0T0T0 technique, dehydrated, and critical point dried with C02- The specimens were examined in a Hitachi scanning electron microscope Model S-500.
Paracrystalline Aggregates of Psoriatic Keratin and Their Relation to Normal Keratin Structure
Authors: Trachtenberg S. , Steinert P.M. , Trus B.L. , Steven A.C.
Published: June 2020

During terminal differentiation of vertebrate epidermis, certain specific keratin intermediate filament (KIF) proteins are produced. Keratinization of the epidermis involves cell death and disruption of the cytoplasm, leaving a network of KIF embedded in an amorphous matrix which forms the outer horny layer known as the stratum corneum. Eventually these cells are shed (desquamation). Normally, the processes of differentiation, keratinization, and desquamation are regulated in an orderly manner. In psoriasis, a chronic skin disease, a hyperkeratotic stratum corneum is produced, resulting in abnormal desquamation of unusually large scales. In this disease, the normal KIF proteins are diminished in amount or absent, and other proteins more typical of proliferative epidermal cells are present. There is also evidence of proteolytic degradation of the KIF.
Teratogenic Effects of Maternal Coffee Consumption on Retinal Layers of Neonatal Mouse Eyes
Authors: Amankwah K. S. , Weberg A. D. , Gillott M. A. , Kaufmann R. C.
Published: June 2020

Concern has been raised about the possible harmful effects upon the fetus of caffeine and freshly brewed coffee consumed during pregnancy. Caffeine has been linked to spontaneous abortion, small-for-dates babies, and congenital malformations in humans and to fetal resorption and fetal death in rodents. Animal studies with caffeine have demonstrated definite teratogenic effects upon fetuses exposed in utero. Caffeine and freshly brewed coffee have been used in animal experiments in which varied methods were employed to dose animals at specific gestational ages, but results from these studies proved inconclusive, particularly in regard to development of the eye. The current study, therefore, was undertaken to determine the effects, if any, of the maternal consumption of freshly brewed coffee upon the development of the retinal layers of the fetal eye.
Changes in Retinal Morphology and Transport in the Diabetic Rat
Authors: Panessa-Warren B.J. , McGarvey E.A. , Brennan L.
Published: June 2020

The eyes from 7 sibling BB/W albino rats (5 diabetic,2 non-diabetic) and the eyes from a new strain of spontaneously insulin dependent pigmented BB/Zucker rats (3 diabetic, 3 non-diabetic) were studied. Alterations in the functional morphology of the diabetic versus normal eyes were analyzed by x-ray fluorescence spectrometry, light and electron microscopy using horse radish peroxidase (HRP) and lanthanum (La) as diffusion tracers, and ion ic La as a marker for calcium binding sites. The albino BB/W rat exhibits spontaneous acute hyperglycemia, ketosis and hypoinsulinemia in 40-60% of sibs, as well as an immune deficiency. The newly developed BB/Zucker strain produces the same spontaneous symptoms of diabetes mellitus seen in the BB/W, with the advantage of providing a larger animal which is not albino but normally pigmented.
Sinusoidal Cells in Bone Marrow Take Up BSA-Au Conjugates in the Presence of an Artificial Blood Substitute
Authors: Geoffroy J.S. , Becker R.P.
Published: June 2020

The pattern of BSA-Au uptake in vivo by endothelial cells of the venous sinuses (sinusoidal cells) of rat bone marrow has been described previously. BSA-Au conjugates are taken up exclusively in coated pits and vesicles, enter and pass through an “endosomal” compartment comprised of smooth-membraned tubules and vacuoles and cup-like bodies, and subsequently reside in multivesicular and dense bodies. The process is very rapid, with BSA-Au reaching secondary lysosmes one minute after presentation. (Figure 1)

In further investigations of this process an isolated limb perfusion method using an artificial blood substitute, Oxypherol-ET (O-ET; Alpha Therapeutics, Los Angeles, CA) was developed. Under nembutal anesthesia, male Sprague-Dawley rats were laparotomized. The left common iliac artery and vein were ligated and the right iliac artery was cannulated via the aorta with a small vein catheter. Pump tubing, preprimed with oxygenated 0-ET at 37°C, was connected to the cannula.
Ultra-Rapid Epoxy Embedment Using Microwave Energy
Authors: Giammara B.
Published: June 2020

The successful use of microwave energy for fixation procedures since 1970 led recently to very rapid staining procedures (3; see Hanker et al, these Proceedings). In this study, its use for embedding procedures using epoxy resins was investigated. The epoxies were mixed according to the resin/DDSA:NMA/DMP-30 system reported by Luft and Burke and Geiselman using the weight per epoxide equivalent (WPE) values calculated for good cutting properties. Kiefer has shown variations in the properties of polymers commercially available for use in electron microscopy. Those epoxies used in our study were Epon 812, TAAB 812, Polybed 812, Maraglas, Araldite 502 and a new polymer, C5048. After proper mixing, the resins were placed in flat embedding molds and placed in a microwave oven at low power settings for 4 to 11 minutes.
Gene-Specific Labeling For An Electron Microscopic Study of Chromosomal Proteins
Authors: Varkey Jacob , Hannibal Mark , Brantley John , Stewart Brian , Beer Michael
Published: June 2020

With the aim of understanding the control of gene expression we are developing techniques to study the proteins bound to particular genes at various stages of activity. To accomplish this we have worked out a gene specific labeling procedure and are testing it with the 5S RNA genes of Xenopus.

Our approach is based on the gene specific purification proposed by Workman and Langmore (1984). Chromatin is digested with a suitable restriction enzyme followed by lambda exonuclease to yield a protruding 3’ end. DMA from the same gene is cut with the same restriction enzyme and nick translated with biotin-dUTP. Then it is digested with exonuclease III to produce a protruding single strand complementary to that of the chromatin. Probe and chromatin are annealed to each other under gentle conditions (0. 1m NaCl; 37°C), Avidin linked to Ferritin is added to decorate the biotin containing regions of the probe and the material is examined in the electron microscope. The chromatin pieces of interest can be recognized by the attached Ferritin labeled probe.
Electron Microscopy and cell biology in the 20th century
Authors: Porter Keith R.
Published: June 2020

The recent history of cell biology cannot be recorded without generous reference to electron microscopy. After all, it was this instrument and the enormous increase in resolution it provided that gave cell biologists access to information that even the most imaginative of investigators had not submitted to the printed page. This paper will record highlights that a few investigators introduced into specimen preparation. This pursuit has contributed more to the progress, i.e. history, of the field than is generally recognized. The first images of cells that can be said to reveal something new were published in 1945. They were micrographs of thinly spread cells grown in tissue culture on surfaces coated with formvar and thence with evaporated carbon. After the suitability of a cell or group of cells had been established by light microscopy, they were freed of culture medium with balanced salt solution and fixed with OsO4. Thereafter, and before drying, the selected cells were washed in distilled water, and to get the cells onto a grid, a small flap of the formvar film was separated from the glass surface and floated over the grid. Subsequently, the preparation was drained of H2O on filter paper and allowed to dry. Cells that resided in open areas between the wires of the grid were available for examination.
Study of Ni/Ni3Al diffusion-couple interface by AEM and HREM
Authors: Watanabe M. , Horita Z. , Smith David J. , McCartney M.R. , Sano T. , Nemoto M.
Published: June 2020

The interface between the Ni-rich solid solution phase (γ phase) and the intermetallic phase (γ'phase) with the Ll2-ordered Ni3Al structure plays an important role in the strengthening of Ni-based two-phase alloys such as superalloys. In this study, we have examined microstructure and diffusional phenomena across the ϒ/ϒ' interface by analytical electron microscopy (AEM) and high resolution electron microscopy (HREM).

Fully annealed high-purity Ni (99.9%) was coupled with Ni-25mol%Al and subjected to diffusion anneal at temperatures of 1073 and 1173K. Thin specimens were prepared from these diffusion couples by careful cutting, grinding, electro-polishing and ion-milling, details of which are described elsewhere. We used three different types of electron microscopes: (a) JEM-2000FX (at 200kV) for measurements of the overall concentration gradient with a probe size of ∼20nm, microstructure observations and selected area diffraction analyses, (b) EM400T-FEG (at 100kV) for high spatial resolution micro-chemical analysis with a probe size of ∼3nm, and (c) JEM-4000EX (at 400kV) for observations of lattice images at the interface. Characteristic x-ray lines of Ni Kα, Al Kα, and Ni La were measured by energy dispersive x-ray spectrometers with a Be-type window which were attached on both JEM-2000FX and EM400T-FEG. Ni Kα and Al Kα lines were used for the determination of compositions, and Ni Kα and Ni Lα lines were for the determination of local thicknesses. X-ray absorption corrections were made by the differential x-ray absorption (DXA) method when determining concentration gradients and by the extrapolation method when determining k-factors.
Phase transformations in rapidly solidified Nd33Fe77 alloy
Authors: Zaluska A. , Liao L.X. , Chen X. , Altounian Z. , Ström-Olsen J.O.
Published: June 2020

Nd-Fe alloys are important for high performance permanent magnets (usually in combination with B, C or N) and a knowledge of the metastable and stable phases of the system is necessary for the development of these new materials. An effective way to investigate such phases is by crystallizing an amorphous precursor.

Amorphous ribbons of the binary alloy Nd33Fe77 were produced by melt-spinning. The phase transformations induced by heat treatment of the as-quenched ribbons is complex involving first the production of metastable phases followed by subsequent transformation into stable phases and finally eutectic melting.
Analysis of ceramic-metal braze alloy systems by EPMA
Authors: Hefter J. , Werber G. , Kang S.
Published: June 2020

The development of advanced material systems for brazing silicon nitride-based ceramics to various metallic substrates (e.g. Incoloy 909 Fe-based superalloy) depends strongly upon the structural and chemical nature of a number of interfaces (ceramic-braze and braze-metal) as well as on the braze microstructure. Such systems are being considered for joining ceramic rotors to metal shafts in automotive applications. Coatings may be deposited on the ceramic surface prior to brazing to promote braze adhesion and wetting. These materials further complicate the resulting microstructure of the system.

Electron probe microanalysis can play a substantial role in the elucidation of the resulting braze microstructures since both phase morphology, distribution, and chemistry may be obtained. Here, a PY-6 silicon nitride ceramic was brazed to Incoloy 909 by using a Mo interlayer brazed between the two materials, Figure 1. The braze is a Au-5Ni-2Pd solid solution system and was used as a 50 μm thick foil. Brazing was accomplished by holding the specimen at 1080 °C for 10 min in a vacuum furnace. A cross-section for EPMA analysis was obtained by normal metallographic methods. All EPMA data were collected using a JEOL JXA-840 coupled with a Noran 5402 EDS system. Digital, background-subtracted maps (256x256, 0.1 s/point) were collected using “IPP” software.
Complete HREM autotuning using automated diffractogram analysis
Authors: Krivanek O.L. , Fan G.Y.
Published: June 2020

Complete autotuning of a high resolution electron microscope (HREM) aligns the electron illumination along the true axis of the objective lens (autoalignment), corrects the astigmatism (autostigmation) and sets the focus to a user-selected value (autofocusing). We have developed a new method which performs complete autotuning with just 3 images, and is faster and more accurate than the best human operators.

Our method uses diffractograms of images of amorphous materials recorded with a slow-scan CCD camera (SSC) at magnifications of 200-800 kx. Diffractograms computed from SSC images have better quality than diffractograms formed in an optical bench from a micrograph recorded on film, and are the perfect starting point for the autotuning procedure. The diffractograms are analyzed by an automatic routine described previously. The analysis yields the defocus, astigmatism, and astigmatism direction, and the computer then applies the needed corrections to the microscope. A single image recorded in typically 0.5 - 1.0 sees plus about 8 sees of processing time on a Macintosh Quadra are therefore sufficient for complete autostigmation and autofocusing. This time is likely to decrease in the future simply because of the increasing power of new generations of computers.
Defocus ramp correction in spot-scan imaging
Authors: Downing Kenneth H.
Published: June 2020

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.

We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.
Measurement of residual stresses in B4C-Al cermets by CBED
Authors: Kim C.H. , Sarikaya M. , Aksay I. A.
Published: June 2020

Ceramic-metal composites (cermets) are designed for improved toughness and strength over monolithic ceramic or metal components alone. They are used for structural applications where either metal or ceramic component cannot be employed separately, such as in impact- or wear- resistant structures which require high hardness and toughness. A well-known example is the WC-Co system (density 14.00 g/cc). We have been successful in developing a low-density (2.65 g/cc) B4C-Al cermet system having fully dense cermet structures that are both tough, KIC up to 16 MPa-m1/2 in 3-pt SENB tests, and strong, 700 MPa in 4-pt bending tests, for ambient temperature applications (impact resistant). In these cermets, B4C (with a composition range from 60-85 v/o) and Al form a three-dimensional network as depicted in the BF/DF pair in Fig. 1.
Deformation mechanisms at epitaxial semiconductor interfaces studied by in situ TEM
Authors: Hull R. , Bean J.C. , Ross F.
Published: June 2020

We have studied deformation mechanisms at epitaxial semiconductor interfaces, primarily in the GexSi1-x/Si and InxGa1-xAs/GaAs systems, by in-situ annealing of metastably strained films in the transmission electron microscope (TEM). This allows direct, real-time, observation and recording of dynamic strain relaxation phenomena such as misfit dislocation nucleation, propagation and interaction mechanisms. This geometry also allows considerable insight into fundamental dislocation physics, as we are able, for example, to accurately quantify dislocation propagation velocities as functions of well-defined effective stresses (in the 108 - 109 pa regime)in the epitaxial layers, and to vary dislocation structure and character by varying the orientation of the epitaxial interface. Comparison with measurements of dislocation velocities in bulk semiconductors and with models of dislocation motion via kink propagation, allows extension of existing measurements and models to the thin film, high stress regime.
In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers
Authors: Nguyen Tai D. , Gronsky Ronald , Kortright Jeffrey B.
Published: June 2020

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.
Probing molecular organization of liquid crystalline polymers by electron and other microscopies
Authors: Stupp Samuel I.
Published: June 2020

Over the past decade many polymers have been synthesized which organize into nematic and smectic mesophases analogous but not identical to those formed by small molecules. It is clear that the phenomenon of liquid crystallinity in polymers is not limited to chains of a specific chemical structure and that self ordering behavior of macromolecules in states of intermediate order is in fact not uncommon. The study of self ordering behavior of polymers into orientationally ordered phases or one dimensional density waves will make important scientific as well as technological contributions. This lecture will discuss a number of problems pertaining to molecular organization in liquid crystalline phases of polymers in which the use of microscopies has played a critical role. The approach is therefore to present the work from a user's perspective emphasizing molecular aspects rather than the techniques themselves.
Low-voltage high-resolution SEM investigations of novel macromolecular liquid crystals
Authors: Adams W.W. , Vezie D.L. , Thomas E.L.
Published: June 2020

The ability to visualize detailed 3-dimensional surface topology with SEM at low voltage and high resolution holds profound promise for analyzing liquid crystal textures, both in polymers and other macromolecular forms. Director textures, domain boundaries, and defects such as inversion walls, disclinations and dislocations can now be easily visualized with this technique. Studies concerning the effects of shear flow and magnetic fields on these defects are currently under way.

Resolution of 4.0 nm at 1.0 keV is now possible with commercial SEM's, which incorporate the latest advances in lens design optimized for low voltage operation, and use high brightness, low energy spread field emission electron guns. The low energy spread of the field emission gun reduces chromatic aberration effects and facilitates successful operation at low keV. Low voltage operation provides dramatically improved image contrast due to the smaller beam/sample interaction volume and also greatly reduces sample charging artifacts. By operating at near crossover conditions, the need for coating nonconducting specimens with a conducting layer of metal or carbon is greatly reduced or eliminated.
TEM study of Si surfaces
Authors: Yagi K. , Sato H. , Kobayashi K. , Nishiyama Y. , Tanaka Y.
Published: June 2020

UHV TEM studies of surfaces have been successfully applied in surface science. Low resolution TEM can characterize surface atomic steps, monolayer adsorbate, reconstruction of surfaces and surface structure domains. TED from surfaces of thin films can be used to analyze surface atomic structure. On the other hand high resolution TEM can seen atomic structure of surfaces either in profile or in plan view modes. The profile mode is effective for surfaces with short periods along the beam direction and is sensitive to displacements of surface atoms normal to the surface and along a direction parallel to the surface and perpendicular to the beam direction. Image contrast of high resolution plan view images is very weak except cases of heavy adsorbed atoms on a substrate of light atoms. The present paper shortly reviews recent studies of Si surfaces done with use of a low resolution UHV TEM and high resolution TEM.
Surface reactions observed by photoemission electron microscopy (PEEM)
Authors: Rotermund H.H.
Published: June 2020

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.
Rotations and transformations in quasimelting
Authors: Narayanaswamy D. , Marks L.D.
Published: June 2020

Morphological fluctuations of a quasimolten particle have been analyzed using high resolution electron microscopy (HREM) to determine the order and relative importance of rotations, translations and morphological transformations.

Small gold particles evaporated onto a holey silicon monoxide support were examined in a conventional 300kV HREM at an electron beam flux of 25A/cm2. Single particles were observed over a period of time. The particle behavior was recorded in real time onto a Sony 8mm videotape recorder, at the rate of 30 frames per second, via a Gatan TV camera. The acquired images were further processed using SEMPER software on an Apollo workstation. The image frames were analyzed by employing a data reduction scheme. A basis set of good images were selected from the entire recording, and completely characterized on the lines of earlier workers. The set was found to consist of four distinct morphologies in various orientations. Samples of the morphologies isolated are shown in Fig. 1.
Theory and practice of energy-filtered electron diffraction using the HB5 STEM
Authors: Qin L.C. , Garratt-Reed A.J. , Hobbs L.W.
Published: June 2020

Electron diffraction patterns obtained in TEM have long been an important part of microstructural characterizations. Certain materials, such as crystalline silicas, are amorphized in the fast electron beam of the TEM, and their aperiodic (metamict) structure is of interest. For amorphous materials, both elastically and inelastically scattered electrons contribute to the diffuse diffraction pattern. Analysis of aperiodic structure, however, requires intensity data from only elastically scattered electrons, and it is therefore it is necessary to obtain energy-filtered electron diffraction patterns. With the energy-filtered electron diffraction technique, the background intensity that is mainly due to inelastically scattered electrons is removed. This makes possible the derivation of radial distribution functions (RDFs) from collected electron diffraction intensity data for uniform aperiodic structures.
Observation of ferroelectric domain boundaries in BaTiO3 with REM
Authors: Tsal Feng
Published: June 2020

The earlier work of transmission electron microscopy(TEM) on ferroelectric domains have been concentrated on the studies of domain configurations and contrast theory, Scanning electron microscopy(SEM) is also used to study ferroelectric material surfaces and has revealed various domain boundaries on the chemical-etched surface of BaTiO3. However, the method is destructive and largely dependent on the etching technique. Reflection electron microscopy (REM) has recently been developed to study crystal surfaces, especially the surface defects such as surface steps and emerging dislocations. This paper presents the observation of 90° domain boundaries in BaTiO3 single crystal with REM and concentrates on the contrast of 90° domain boundaries.
Crystallization of barium hexaferrite
Authors: Lee Chung-kook , Berta Yolande , Speyer Robert F.
Published: June 2020

Barium hexaferrite (BaFe12O19) is a promising candidate for high density magnetic recording media due to its superior magnetic properties. For particulate recording media, nano-sized single crystalline powders with a narrow size distribution are a primary application requirement. The glass-crystallization method is preferred because of the controllability of crystallization kinetics, hence, particle size and size distribution. A disadvantage of this method is the need to melt raw materials at high temperatures with non-reactive crucibles, e.g. platinum. However, in this work, we have shown that crystal growth of barium hexaferrite occurred during low temperature heat treatment of raw batches.
Observation of frozen hydrated oil sands fine tailings: Freezing effects and interparticle forces
Authors: Mikula R.J. , Lam W.W. , Payette C. , Munoz V.A.
Published: June 2020

It is well known that kaolinite clay platelets can align positive edges with negative faces to build a so called “card-house” structure. Although kaolinite is a major component of oil sands fine tailings or sludge, this idealized structure is unlikely due to the presence of other components. The modification of the ideal card house suggested by Scott et al is more likely to exist in sludge. Freeze fracture preparation and subsequent direct observation of frozen hydrated samples in an electron microscope were used to characterize the morphology and composition of oil sands sludges, in order to directly determine the interactions between the various components. In these cryogenic techniques, the rate of freezing is critical in minimizing the creation of artifacts.
Irradiation damage in OHAP studied by HREM
Authors: Wen Shulin , Feng Jingwei , Smith D.J.
Published: June 2020

Hydroxyapatite (OHAP) with chemical composition Ca10(PO4)6(OH)2is a very promising biomaterial. OHAP has been found to be incorporated in bone and tooth tissue. Both sintered OHAP compact implant and OHAP-coated implant are used as prostheses in surgery. Recent irradiation damage studies show that very complicated physical and chemical process may occur to both the synthetic OHAP and natural OHAP (human enamel), during the electron irradiation in TEM analysis. So the irradiation damage investigation is very important for TEM study of OHAP.
The search for a ‘materials science’ knife in ultramicrotomy
Authors: Malis Tom
Published: June 2020

Specimen preparation problems in analytical electron microscopy relating to phase differences, specimen geometry or microanalytical requirements have spurred increasing usage of diamond knife sectioning. Since many of these materials are quite hard and/or tough, many material scientists assume (hope?) that there must be a knife specifically designed for ‘hard’ materials. The fact that such a knife has not been developed is due to the fact that conventional (biological) knives have performed so well, with somewhat vague recommendations to use a 35° knife angle for reduced section compression, 45° for general usage and 55° for very hard materials such as embedded catalyst particles.
Electron crystallographic studies onE.coli- expressed variants of bacteriorhodopsin
Authors: Mitra Alok K , Miercke Larry J. W. , Betlach Mary C. , Shand Richard F. , Stroud Robert M.
Published: June 2020

Bacterorhodopsin (BR) is an integral membrane protein present in the purple membrane (PM) ofHalobacterium halobiumwhere it is arranged in a highly ordered 2-dimensional hexagonal P3 lattice. BR contains a single retinylidene chromophore bound via a protonated Schiff base to Lys-216 and functions as a light-driven proton pump. Upon absorption of a photon, BR cycles through a series of photointermediates resulting in a vectorial pumping of a proton from the intracellular side to the extracellular side. Site-directed mutagenesis has identified residues whose substitution affects the chromophore environment in BR and those that are involved in the proton transport. Specifically Asp-85, Asp-212, and Arg-82 are involved in the proton release pathway, whereas Asp-96 is involved in Schiff base reprotonation.
Immunolocalization of vault particles in cultured cells
Authors: Kedersha Nancy L. , Rome Leonard H.
Published: June 2020

We first reported on the existence of vault ribonucleoprotein particles in 1986, and since this study we have demonstrated that these unusual RNPs are ubiquitously expressed and highly conserved among diverse eukaryotes. These particles are quite large (65 x 35 nm) and distinctly regular in shape and dimensions. The polypeptide composition of vaults is also similar between species, dominated by a∼100 Kd protein which makes up >70% of the particles mass. The RNA component of vaults, which has been sequenced and characterized from both rat and bullfrog, does not appear to serve a structural role, and due to the strong conservation of its secondary structure could serve a functional role.
Density-based discrimination of protein and RNA in the ribosome
Authors: Frank Joachim
Published: June 2020

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.