bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractography of Polytetrafluorethylene (PTFE)
Authors: Nerren Billy H.
Published: June 2020

The need to know how and why materials fail is increasing each year. It is universally known and accepted that failure modes of metals can be determined by studying the topography of the fracture surfaces. The need for understanding failures of non-metals has recently been dramatized by the failure of a PTFE seal in a Saturn V LOX fill and drain valve that resulted in a liquid oxygen leak. In an effort to bridge this gap in our knowledge, a study was designed to determine the applicability of fractographic analysis to non-metals, in particular, to PTFE.

Initial work was performed using both the direct carbon and the two stage acetate replication techniques. However, the two stage acetate replica technique was later selected for all work because of the difficulty in removing a direct replica from PTFE.
Phase Separation in Vanadate Glasses
Authors: Luehrs Fred U. , Anderson Gordon Wood
Published: June 2020

To unambiguously interpret studies of physical properties of nonperiodic solids, structural characterization, often neglected, must be done. This investigation was made along with electrical and optical measurements of the V2O5-P2O5 system. Because the electrical conductivity of amorphous materials is often sensitive to the existence of a second phase, it was essential to determine if the V2O5-P2O5 system is a glass and if it contains more than one phase, a glass being defined as an isotropic material of viscosity greater than 1014 poise with no three dimensional periodicity of dimension greater than 20 Å. Over 300 samples from 15 batches were prepared including single dtage platinum shadowed carbon replicas of freshly fractured surfaces, ground chips, and blown thin films of compositions 70.0, 80.0, and 87.5 mole % V2O5. The replication technique's limited resolution and inability to distinguish between crystalline and noncrystalline inhomogeneities made it useless. Although sandwiched between conducting films and placed in a cooling stage, bulk chips melted during examination and thus gave meaningless results. Blown thin films were stable, did not melt, and thus gave useful results.
Initial Stages of the Oxidation of Tantalum
Authors: Geiss R. H. , Lawless K. R.
Published: June 2020

Pre-thinned high purity tantalum sheet was oxidized in high purity oxygen at 500°C in an ultra high vacuum reactor vessel at pressures of 10 to 100 microns for 30 to 90 minutes. Transmission electron microscopy revealed changes in the microstructure as the oxidation progressed and electron diffraction showed many different sub-oxide phases and marked ordering effects.

For the lowest oxygen exposure, 10 microns for 30 minutes, a microstructure showing both large and small domains was found, Figure 1. As can be seen the size and shape of the domains varied considerably. The long narrow domains are near the edge of the foil and all have boundaries along ﹛100﹜ In intermediate regions, about one micron in from the edge, the domains have a peculiar “air plane” shape with boundaries along both ﹛100﹜ and ﹛110﹜ and “wings” adjacent to the ﹛100﹜ boundary. Interspaced among the airplane shaped domains and in regions up to 3 microns from the edge are very small, interconnected nuclei.
Moire Fringes in Alpha Plates Within a Beta Titanium Alloy
Authors: Banerjee Bani R.
Published: June 2020

When the beta phase isothermally transforms to alpha upon aging, the lenticular alpha precipitate frequently exhibits fine parallel markings, as shown in Figure 1, but the nature of the markings remains unexplained, although microtwins and oxide epitaxy have been suggested. Therefore, 25μ thick foil specimens of the alloy (14.0V, 11.5 Cr, 3.2 Al, bal Ti) were solution annealed 1/4 hr. at 788C, and aged 24 and 72 hr. respectively at 482C — using a predessicated Argon atmosphere. The heat-treated foils were electrolytically thinned in a 6% perchloric acid, 59% methanol, 35% ethylene glycol monobutyl ether electrolyte, at 15-18 volts, using a Bollmann electrode arrangement.

Because of the absence of twin reflections and the lack of evidence of an oxide film by electron diffraction from foils exhibiting parallel markings in the alpha plates (Figure 1), the markings were suspected to be Moiré fringes produced by double diffraction from the alpha precipitate and the beta matrix respectively.
The Effect of Oxidation on the Electron Fractographic Interpretation of Fractures in Steel
Authors: Russ J. C. , Miller G. A.
Published: June 2020

Most investigators who use electron fractography are aware of the desirability of avoiding oxidation of the fracture surface or at least ignoring any corroded areas present. While this can usually be done in laboratory situations, in the case of service failures it is frequently impossible to protect fractures from oxidation and the alternate approach is to remove the oxide by one of several methods available. The tacit assumption in applying this technique has been that while heavily pitted areas on a microscale must be ignored, any characteristic fracture markings visible are representative of the true fracture surface. In other words, any artifacts produced by the oxidation or cleaning process are assumed to be distinguishable from the details of the fracture. The experiments reported here showed that this assumption is not always valid and also established, under controlled conditions, the maximum amount of oxidation that can be removed and still permit interpretation of the original fracture details.
The Reaction of Carbon Black and Thoria
Authors: Mercer H. N.
Published: June 2020

As a result of a reported “dispersal of carbon black to individual crystallites” by K. J. Notz, we decided to investigate this phenomenon. We have observed a somewhat different reaction in that portions of the carbon particles are removed instead of complete breakdown to individual crystallites.

Carbon black is particulate matter composed almost entirely of carbon. The particles are somewhat spherical and fuse together during manufacture to form chains of varying length. These particles and chains retain their same shape during most reactions and when incorporated into rubber. Oxidative attack on normal furnace blacks occurs from the inside out due probably to more random orientation of the crystallites at the center of a particle. Many chemical reactions of the functional groups at the surface of the carbon particle are also known. The observation that the simple mixing of carbon black with finely divided thoria removes only a portion of the particle, constitutes a new type of carbon black reaction.
Analysis of Silicon Carbide Deposits Formed on Silicon Single Crystals by Surface Reaction With Acetylene at Elevated Temperature
Authors: Tufts Charles F. , Emma Thomas A.
Published: June 2020

Electron optical methods assisted by light microscopy were used to describe crystal geometry and structure of two deposits formed on (110) surfaces of high-purity, n-type Si grown by Czochralski methods and having resistivities of 120-250 ohm cm. Average dislocation density was <104/cm2. Specimens were 10 mm x 3 mm x 0.75 mm thick as cut by an inside diameter-type diamond saw. A 10 mm x 3 mm face was used for substrate and prepared by a sequence of mechanical lapping, mechanical-chemical polishing and chemical polishing in 3%HF(48%)-HNO3 (conc.). Surface reaction that produced epitaxy lasted two hours at 900°C in C2H2, with partial pressure of ∼5 x 10-7 torr. Prior to introduction of C2H2, specimens were annealed for ∼20 minutes at 900°C in vacuum of 1.6 x 10-9 torr. Average “as calculated” deposit thickness was ∼1000Å.
Contributions of ultrastructural cytochemistry to the analysis of stimlus-response patterns in neutrophils
Authors: Karnovsky M. J.
Published: June 2020

Upon stimulation neutrophils undergo a complex series of biochemical and morphological changes. Phagocytosis by polymorphonuclear leukocytes (PMN) is accompanied by enhanced cyanide-insensitive respiration and hexose monophosphate shunt activity. H2O2 and O2 free radicals, such as superoxide O2-, are produced in increased amounts. H2O2, myeloperoxidase, and halide ions constitute a potent microbicidal system (Klebanoff system), via halogenation, e.g., chlorination, of microorganisms. Intermediate reaction products of oxidation, e.g., aldehydes, might themselves be microbicidal, or act as substrates for further H2O2 production. We have examined these aspects of phagocytosis with specially developed techniques of oxidative cytochemistry and correlated cytochemical, biochemical, and functional data.

Utilizing diaminobenzidine (DAB) as a substrate for myeloperoxidase, we were able to confirm, at the EM level, that myeloperoxidase, present in the azurophil granules, enters the phagosome upon degranulation. We also showed, using a modified DAB reaction, that endogenous H2O2 was present in the phagosome. Intracellular halide, probably chloride, is presumed to be freely available.
Three-dimensional reconstruction studies of mitotic spindle ultrastructure
Authors: Rieder C.L. , Rupp G. , Alexander S.P. , Nicklas R.B.
Published: June 2020

The mitotic spindle is composed chiefly of microtubules (MTs) and functions to equally distribute the replicated chromosomes to daughter cells. Spindles are generated from an interaction between the spindle poles and kinetochores. The former are responsible for generating spindle MTs while the latter act as sites for attaching the chromosomes to the MTs. As noted by McIntosh the emphasis of most mitotic investigations is structural “because the spindle is a kind of machine, and numerous structural questions are obvious as one tries to understand a device which converts chemical energy into mechanical work.”

During the course of our mitosis studies it was frequently necessary to reconstruct the three-dimensional (3D) ultrastructure of spindles from serial sections. To do this we utilized the STERECON system developed at the Albany HVEM facility. Briefly, prints of serial sections are enlarged to an optimum final magnification. For each section, profiles are drawn on clear plastic sheets outlining the chromosomes, mitochondria, and spindle MTs.
The spindle stage: A powerful optical tool
Authors: Gunter Mickey E. , Bloss F. Donald
Published: June 2020

A single, reasonably homogeneous, nonopaque 30-to-300 μm crystal, mounted on a spindle stage and studied by immersion methods under a polarizing microscope, yields optical data frequently sufficient to identify and characterize a substance unequivocally. The data obtainable include (1) the orientation of the crystal's principal vibration axes and (2) its principal refractive indices, to within 0.0002 if desired, for light vibrating along these principal vibration axes. Spindle stages tend to be simple and relatively inexpensive, some costing less than $50. They permit rotation of the crystal about a single axis which is parallel to the microscope stage. This spindle or S-axis is thus perpendicular to the M-axis, namely the microscope stage's axis of rotation.

A spindle stage excels when studying anisotropic crystals. It orients uniaxial crystals within minutes and biaxial crystals almost as quickly so that their principal refractive indices - ɛ and ω (uniaxial); α, β and γ (biaxial) - can be determined without significant error from crystal misorientation.
Scanning laser imagers with large working distances
Authors: Webb Robert H.
Published: June 2020

The confocal Scanning Laser Ophthalmoscope exemplifies the new and exciting images available with scanning techniques, and particularly with a confocal arrangement. An ophthalmoscope might be considered a microscope whose objective is the cornea and lens of the eye. As such, it has a working distance of about 23 mm , a spherical object surface, and a resolution of 10 μm . With an external lens, the instrument can be configured as a general microscope of long working distance. We have made this change to facilitate viewing the convex surface of the eye's conjunctiva, benefitting from the great depth of focus available in a scanning system, and for observing melanotic skin lesions with the extreme rejection of scattered light available in a confocal arrangement.

Scanning microscopes illuminate only one resolution element of the object at a time. Thus they encode the image information temporally - as a sequence of voltage pulses from an electro-optical detector.
Differential polarization microscopy: Theory and applications
Authors: Finzi Laura , Beach David , Bustamante Carlos , Garab Gyozo
Published: June 2020

In Differential Polarization Microscopy two images of an object obtained usina orthogonal incident polarizations are subtracted from each other. The resulting difference image can display both magnitude and sign whose values will vary according to location in the image and the value of the local optical anisotropy of the object.Thus, Linear Dichroism and Circular Dichroism images of an object can be obtained.

a) In-situ studies of the polymerization of Hb S in red blood sickle cells.-Mutant hemoglobin Hb S, present in sickle cell anemia, tends to aggregate at low pressures of oxygen forming polymers. Furthermore various polymers can align side by side. Using differential polarization image we can detect the angle of alignment and amount of polymerized HbS inside a red blood cell. We have also developed a supra-vital method for following the reversible process of polymerization and alignment inside a red blood cell, as a function of the oxygen pressure.
Cryopreservation of cystic fibrosis nasal epithelium
Authors: Herlong J. R.
Published: June 2020

Cystic fibrosis (CF) is the most common lethal genetic disease which affects Caucasians. The respiratory system is almost universally affected in CF patients, and the basic defect in this organ system as well as in others appears to be an abnormality of the regulation of chloride ion transport; the transport of other ions may also be either primarily or secondarily affected. Both the nasal mucosa and the lower respiratory tracts of CF patients exhibit this defect, but the nasal mucosa is free of the infectious complications common in the lower tract regions. Electron probe x ray microanalysis (EPXMA) promises to be a useful tool in the investigation, at the cellular and subcellular levels, of this ion transport defect as well as possible defects in the transport of other ions. This report documents the development of techniques for obtaining well-preserved cryosections of human nasal mucosa which are suitable for subsequent EPXMA.
Confocal laser microscopy of impregnated central nervous system tissue
Authors: Turner J.N. , Siemens M. , Szarowski D. , Collins D.N.
Published: June 2020

A classic preparation of central nervous system tissue (CNS) is the Golgi procedure popularized by Cajal. The method is partially specific as only a few cells are impregnated with silver chromate usualy after osmium post fixation. Samples are observable by light (LM) or electron microscopy (EM). However, the impregnation is often so dense that structures are masked in EM, and the osmium background may be undesirable in LM. Gold toning is used for a subtle but high contrast EM preparation, and osmium can be omitted for LM. We are investigating these preparations as part of a study to develop correlative LM and EM (particularly HVEM) methodologies in neurobiology. Confocal light microscopy is particularly useful as the impregnated cells have extensive three-dimensional structure in tissue samples from one to several hundred micrometers thick. Boyde has observed similar preparations in the tandem scanning reflected light microscope (TSRLM).
Cryo-SEM of liquid-bearing rock
Authors: Sutanto E.
Published: June 2020

Scanning electron microscopy has been used to examine microstructure of dry soils, sedimentary rocks and other porous materials for three decades. There are many studies of sand grain surface texture, pore morphology, and clay swelling. However, pore geometry and surface topography are only part of the story of how two or more fluids flow through porous media, whether they be unconsolidated or consolidated. The other part is how the fluids distribute in the pore space. Fluid distribution in pore space is largely governed by relative wettability of pore walls. Wetting fluid tends to reside on walls as a thin film and to occupy small pores totally, whereas nonwetting fluid tends to occupy the center of larger pores. Which fluid is more strongly wetting depends on the local nature of the wall. Contact angles indicate wettability of planar, homogeneous solid surfaces, but roughness and compositional heterogeneity, which seem to be common in sedimentary rock, complicate matters.
Arrangement of Acetylcholine Receptor Subunits in Different Physiological States
Authors: Toyoshima Chikashi , Unwin Nigel
Published: June 2020

The nicotinic acetylcholine receptor (AChR) is a ligand-gated membrane ion channel consisting of 5 subunits (α, δ, γ, α and β). It exists in at least three different physiological states, namely, resting, desensitized and open states. Our goal is to elucidate the mechanism of ion gating by visualizing the three-dimensional structures of the receptor in different physiological conditions. We have been extending the previous electron image analysis on AChR embedded in ice to obtain the 3D density maps in the native (resting) and desensitized states at better than 20 Å resolution.

There are two possible ways to analyse tubular crystals of AChR from Torpedo marmorata postsynaptic membranes. One is to treat them as superimposed 2D crystals by selecting wide flattened tubes embedded in very thin ice (Fig. 1a); the other is to utilize native helical symmetry preserved well in narrow tubes embedded in thick ice over holes (Fig. 1b). Analysing the same objects in two different ways will allow us to obtain reliable data on possibly small structural changes.
Voltage Measurement by Electron-Beam Probing
Authors: Reimer J.D.
Published: June 2020

Ihe voltage measurement technique, commonly used to probe internal nodes to determine signal delays or voltage levels in integrated circuits (ICs), is undergoing a fundamental change. Until recently, fine tungsten needles have been used almost exclusively to carry out these measurements. Advances in IC processing technology have allowed IC interconnection linewidth of 2 μm or less to become a reality. Ihis has caused the tungsten needle to remain at a disproportionate, unsuitable size (Fig. 1), typically causing substantial mechanical damage to the device surface being probed. In anticipation of this dilemma, an alternative technique has been developed, which uses an electron probe instead of a tungsten needle. Since the electron beam (e-beam) does not make contact, no physical damage occurs. Furthermore, it does not present the detrimental loading effect, as does the needle probe, which causes delays or possible device malfunction. Strategies for e-beam probing have been reviewed extensively.
The Return of SEM Beam-Tilt Stereo
Authors: Pawley J. B.
Published: June 2020

Stereo images add much to an accurate interpretation of surface images produced by the scanning electron microscope (SEM). Although the secondary electron (SE) signal contains considerable information about the micro-topography of the specimen, various non-topographic information may also be present. Because the process of binocular stereopsis by which we "see" in stereo depends chiefly on pattern recognition rather than on brightness, it discriminates against brightness artifacts and conveys a more accurate and if necessary, fully quantitative, impression of the actual micro-topography of the specimen surface.

Stereo-pairs are normally produced by photographing a first view, tilting the specimen about 8 deg and then translating it so that the prominent features are again found in about the same position of the screen and finally recording the second image. The two images are viewed using one of a variety of devices designed to present each image only to the appropriate eye so that the two images can be fused and processed by the brain to produce a 3-D image.
Striated Muscle in the Intestine of Shrimp
Authors: Liu K. C. , Tsay S. F. , Yu Y. L.
Published: June 2020

The shrimp, Penaeus monodon, commonly known as grass shrimp by local people. It has been cultured in large quantity and became one of the important aqua- cultural species in recent years. The morphology and histology of penaeid shrimps has been studied by many researchers (1). In our pathological study of the structural aspects of the digestive system, striated muscle was found in the area equivalent to the muscularis mucosa of tunica mucosa and tun.ica muscularis of vertebrates where smooth muscle is the basic structural element. This information is new to us , and to the best of our knowledge, there is no similar report among other Crustacea (2). This report is to present some of our evidence.

Shrimps, Penaeus monodon, 50 g. in average body weight, were bought live from the market. Their intestines were disssected out and processed for both light electron microscopic studies. For electron microscopic observation a JEOL 100 CX electron microscope was used at 60 KV. attention was primarily concentrated on the circular muscle of the muscularis mucosa region.
Structure of “Sensory” Surface Nerve Endings in Schistosoma Mansoni Miracidia
Authors: Jones Betty Ruth , Chi-Tung Pan Steve
Published: June 2020

Schistosomiasis has been described as “one of the most devastating diseases of mankind, second only to malaria in its deleterious effects on the social and economic development of populations in many warm areas of the world.” The disease is worldwide and is probably spreading faster and becoming more intense than the overall research efforts designed to provide the basis for countering it. Moreover, there are indications that the development of water resources and the demands for increasing cultivation and food in developing countries may prevent adequate control of the disease, and thus, the number of infections are increasing.

Our knowledge of the basic biology of the parasite causing the disease is far from adequate. Such knowledge is essential if we are to develop a rational approach to the effective control of human schistosomiasis. The miracidium is the first infective stage in the complex life cycle of schistosomes.
The Fine Surface Structure of the Male Genital Bulb of the Dwarf Spider Catabrithorax Plumosus
Authors: Cady C , Cyrus R. V. , Kaspar J. L.
Published: June 2020

The spider Catabrithorax plumosus (Emerton) family Linyphiidae, subfamily Erigoninae is a member of an abundant yet reclusive group known as the dwarf spiders. Collectively, these are the smallest spiders in North America. Most measure only 1-3 mm in length, creating difficulties in indentification. The morphology of the male genital bulb, located on the distal pedipalp, is of great importance to the taxonomist in identifying spiders to the species level. This study examines the complex male genital structure in both the expanded and unexpended condition by means of the Scanning Electron Microscope (SEM).

Pedipalps were removed at the trochanter-femur articulation, dehydrated in 70% ethanol and expanded by Immersion in lactic acid for 6-8 h. After complete expansion a graded amyl acetate series preceeded critical point drying. Unexpanded palps were dehydrated in an ethanol series followed by a graded amyl acetate series in ethanol. Specimens were critical point dried from CO2 and given an evaporated coating of carbon-gold. Specimens were examined in a Hitachi HHS-2R Scanning Electron Microscope operating at an accelerating voltage of 10 kV.
A study of geotropism in roots of pisum sativum through the use of transmission and light microscopy
Authors: Karas J. G.
Published: June 2020

A current theory of graviperception in roots is the settling of starch grains in the columella tissue of the root cap. This settling against the endoplasmic reticulum or other cell components may induce calcium release along the lower cell membrane, which sets up an auxin sink; thereby allowing differential growth on that wall. In order to more thoroughly elucidate the role of starch grains (staloliths) in the graviperception mechanism knowledge of the structures and subcellular organelles found in the pea root tip in and adjacent to the region of graviperception in newly differentiated cells under conditions of gravitational change is needed. This presentation addresses some of these areas.

Seeds of Pisum sativum - Dwarf Gray Sugar were surface sterilized in one percent sodium hypochlorite for twenty minutes followed by a twenty minute rinse in running tap water. The seeds were placed on two sheets of filter paper in one hundred mm plastic petri dishes containing five ml of free water. They were dark germinated for three days. One to one and one-half mm tips were harvested and dropped into solution A which contained twenty-five mis each of 8% Paraformaldehyde, 0.2 M cacodylate buffer adjusted to pH 7.6, and distilled water 1-1/2 hours at 4° C.
Effect of different colchicine concentrations on microtubules and membranes in tomato root tip cells
Authors: Jensen T.E.
Published: June 2020

The effect of colchicine on microtubules has been investigated in numerous cell types. In this present study we have used different concentrations of colchicine to determine if the two major groups of microtubules in plant cells, plasma membrane associated and mitotic, are differentially sensitive to this drug.

Tomato seeds “Michigan forcing” were germinated on filter paper saturated with distilled water. Radicles 1.5 to 2.0cm were selected and placed into either distilled water or colchicine, 0.001, 0.01, 0.03, 0.04, 0.05, 0.1%, for 20 hrs. During this time they were kept at 20°C in dim light. Root tips were fixed in 3% glutaraldehyde in phosphate buffer at pH7.2 for lh at 4°C. After 5 rinses in buffer they were placed in 1% OsO4 in phosphate buffer at pH7.2 for 1h at 4°C. Root tips were then dehydrated in ethanol, treated with propylene and embedded in Epon.

No growth occurred in any of the colchicine treated radicles. Observation of thin sections of control cells revealed many plasma membrane associated microtubules, many cells in division stages and the usual arrangement of cell organelles.
Ultrastructure of feline calicivirus-infected crandell's feline kidney (CRFK) cells in culture
Authors: Dick C. P. , Johnson R.P. , Bast T. , Yamashiro S.
Published: June 2020

Viruses frequently are difficult to visualize using routine transmission electron microscopy (TEM) of tissues collected from infected animals. Using cell cultures infected with viruses as in vitro models, viral replication and their resultant cytopathic effects can be more easily examined.

Feline calicivirus (FCV), a common upper respiratory pathogen in cats has been successfully propagated in Crandell's Feline Kidney (CRFK) cells and a number of ultrastructural viral inclusions noted (1-4). This study represents further investigation of FCV infected CRFK cells using strain 255. The similarities and differences in our findings as compared to those of previous investigations have been explored.

Confluent monolayers of CRFK cells in 80 cm2 plastic flasks were inoculated with 105 median cell culture infectious doses of FCV strain 255. When approximately 60 percent of cells exhibit FCV cytopathic effect the medium was decanted and the cells scraped from the surface using a rubber policeman. The cell suspension was centrifuged at 5000 rpm for 20 minutes at 4°C. Details of the procedure have been reported previously (5).
Ultrastructural morphology of the epidermis of the dog with generalized demodectic mange
Authors: Al-Bagdadi F. , Foil C.
Published: June 2020

The canine skin is considered a normal environment for the Demodex mite (Scott et al, 1974). The parasite dwells in the hair follicles and sometimes the sebaceous glands of the skin (Muller et al, 1983) and occasionally inhabits the apocrine sweat glands (Scott, 1979). No mention of the mite nesting within the epidermis has been made. The life cycle of the mite and the eruption of the disease is an unresolved puzzle. The majority of the articles written on the subject deal with the treatment of the disease. No mention of the epidermal changes in infected dogs has been made. It is necessary to explore the ultrastuctural changes of the skin for the hope of a better understanding of the disease and the mites inhabitation of the epidermis which has not been documented nor mentioned in the literature.

Three short haired dogs with canine generalized Demodectic mange (CGDM) have been studied at the School of Veterinary Medicine clinic at L.S.U. and were treated during 1981-1985.
Evaluation of blocking agents in protein A-gold immunocytochemistry
Authors: Komuves L. G. , King E. J.
Published: June 2020

Various blocking agent solutions are used in protein A-gold immunocytochemistry to prevent or reduce nonspecific attachment of antibodies and/or protein A-gold particles to tissue sections. In our study of intracellular antigens present at low levels, the inadequacy of some commonly used blocking solutions became evident. We, therefore, compared several blocking solutions by exposing L929 cell cultures, at 4 °C, to a hapten-labeled lectin (dinitro-phenol-labeled wheat germ agglutinin, DNP-WGA) that binds specifically to the plasma membrane. We then used the protein A-gold method to locate the bound DNP-WGA. Since endocytosis had been prevented, gold particles not associated with the plasma membrane were regarded as nonspecific.

The cells were incubated with DNP-WGA for 2 h at 4 °C, and were then fixed with 2% glutaraldehyde and 2% paraformaldehyde in 0.1 M cacodylate buffer, pH 7.2. Some samples were also postfixed with osmium tetroxide.
Computer-assisted morphometry of synaptic terminal density in the aging brain
Authors: Casey M. A.
Published: June 2020

In studying the circuitry of a given region of the brain, some knowledge of the density of synaptic terminals is useful. Such data is especially valuable when studying the brain under pathological or experimental conditions. The methods outlined in this paper have been used to detect axosomatic synaptic terminal loss in the aging rat brain, but they would be applicable to other experimental paradigms.

The methods in the present paper have been described elsewhere, and were recently used in our study of the lateral superior olivary nucleus (LSO), a well-characterized cell group in the rat superior olivary complex, and a key component of the rat lower auditory pathway. Virtually all synaptic terminals ending on the cell bodies of LSO principal cells originate in the medial nucleus of the trapezoid body (MTB), which undergoes a significant loss of neurons with age in rats. Thus, we wanted to determine whether loss of MTB cells resulted in a significant loss of axosomatic terminals in the LSO.
characterization of amorphization in Ni-Ti multilayers
Authors: Alexander K. B. , Walker F. J. , McKee R. A. , List F. A.
Published: June 2020

The formation of amorphous alloys through the solid-state reaction of crystalline multilayers has recently been studied by several groups. In each of these studies, the multilayers were entirely amorphous when there were less than 4-10 planes in each layer. Layer thicknesses larger than this resulted in crystalline layers, presumably separated by an amorphous film approximately 4-10 layers thick. Our intent was to measure the thickness of the amorphous film in Ni-Ti multilayer specimens with a wavelength (thickness of Ni + Ti layers) of 20 nm, or approximately 40 planes per elemental layer. In situ Reflection High Energy Electron Diffraction (RHEED) was performed during the film deposition and transmission electron microscopy of cross-sectional specimens was used to examine the as-deposited films.

Nickel and titanium layers were sequentially deposited onto a 50 nm amorphous Ni-Ti codeposit on an unheated (001) silicon substrate in the ORNL Molecular Beam Epitaxy (MBE) facility with a vacuum < 10-9 torr.
Crystallization of Zr-Ni metallic glasses
Authors: McKamey C. G. , Kroeger D. M. , Easton D. S. , Horton J. A.
Published: June 2020

In a previous paper the results of a study of the crystallization of Zr-Ni metallic glasses of compositions between 55 and 70 at. % Zr were reported. Data from differential scanning calorimetry (DSC) and x-ray diffraction (XRD) were presented and discussed with respect to the phase transformations occurring during the crystallization process. A metastable crystalline phase, shown by DSC and XRD results to appear between 57 and 63.2 at. % Zr, was the first phase to appear upon heating the amorphous metal. (Evidence indicates the stoichiometric composition for this phase is approximately 60% Zr.) This metastable phase transforms to the equilibrium crystalline phases (ZrNi and Zr2Ni) upon further heating. For compositions of 55-57 and 63.5-70% Zr only the equilibrium phases appear upon heating. It was noted that phase separation and chemical short range ordering (SRO) are believed to play an important role in the crystallization of these alloys.
Precipitation in S-ion implanted Si
Authors: Herring R.A.
Published: June 2020

Using ion implantation for doping semiconductor materials can provide solute concentrations far exceeding the dopant solubility limit. Subsequent annealing of the implanted material produces a high density of dislocation loops. Although the number of dislocations can be reduced by annealing at higher temperatures the material cannot retain the solute in solid solution.

We have examined this dilemma by implanting Si with high-energy (6-MeV) S ions to concentrations of ∽ 1020 cm-3, and then heat treating the implanted Si by rapid thermal annealing (RTA) as part of a fabrication procedure for making extrinsic-Si detectors. The maximum solubility limit of S in Si is ∽ 3 x 1018 cm-3. At RTA temperatures < 1000°C faulted dislocation loops formed in the implanted region [1], Above 1000°C the dislocation loops unfaulted and coalesced to form a dislocation network and what appear to be small dislocation loops or small cluster-like structures with maximum diameters of < 100 Å (Fig. 1).
Elemental imaging of thin specimens with an energy filtering electron microscope (EFEM)
Authors: Bauer R. , Probst W. , W.I. Miller
Published: June 2020

In conventional TEM (CTEM), image contrast is determined by scattering absorption contrast, diffraction contrast and phase contrast. Phase contrast is produced by the interference of unscattered electrons and elastically scattered electrons. Scattering absorption contrast and diffraction contrast are produced by angle selection of the scattered electrons using an objective aperture diaphragm for brightfield, darkfield and diffraction images.

In an EFEM, with an integrated imaging electron energy-loss spectrometer, angle selection is used as in CTEM, but, additionally, it is possible to perform energy selection. This is done from the energy-loss spectrum obtained for the specimen area imaged. Energy selection permits the elimination of all inelastically scattered electrons to improve contrast for brightfield, darkfield and diffraction images. This technique also permits imaging of selected, e.g. e1ement-characteristic, ine1astica11y scattered electrons. Images obtained in this way display object- specific or e1ement-specific contrast and are termed electron or element-spectroscopic images (ESI).
Energy-filtered STEM imaging of thick biological sections
Authors: Colliex C. , Mory C. , Olins A. L. , Olins D. E. , Tencé M.
Published: June 2020

Energy filtered imaging of thick biological specimens offers an excellent alternative to HVEM or IVEM. In order to explore the physical parameters which effect the energy loss spectra and the images formed by various energy loss windows we undertook a quantitative study using a dedicated STEM (VG-HB501) fitted with an energy loss spectrometer and interfaced with sophisticated data acquisition capability. Our mathematical analysis is useful in predicting the quality of bright field thick specimen images formed with energy filtered electrons.

Our specimen was the salivary gland of Chironomus tentans which contains giant polytene chromosomes. Conventional preparative methods included fixation, epon embedding, and cutting 0.5 μm sections. Digital images were formed at plasomon (∼25 eV) multiples (n = 0 to 7). For each image the mean (I), maximum and minimum intensities and the standard deviation (σ) were determined.
High-resolution x-ray imaging of small copper-rich precipitates in steels
Authors: Michael J. R. , Taylor K. A.
Published: June 2020

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.
The observation of solutions in Ni3Nb
Authors: Wang Z.M. , Zhang J.P.
Published: June 2020

High resolution electron microscopy reveals that antiphase domain boundaries in β-Ni3Nb have a hexagonal unit cell with lattice parameters ah=aβ and ch=bβ, where aβ and bβ are of the orthogonal β matrix. (See Figure 1.) Some of these boundaries can creep “upstairs” leaving an incoherent area, as shown in region P. When the stepped boundaries meet each other, they do not lose their own character. Our consideration in this work is to estimate the influnce of the natural misfit δ{(ab-aβ)/aβ≠0}. Defining the displacement field at the boundary as a phase modulation Φ(x), following the Frenkel-Kontorova model [2], we consider the boundary area to be made up of a two unit chain, the upper portion of which can move and the lower portion of the β matrix type, assumed to be fixed. (See the schematic pattern in Figure 2(a)).
Measurement of solute segregation to grain boundaries in the AEM: A review
Authors: Williams D. B. , Romig A. D.
Published: June 2020

The segregation of solute or imparity elements to grain boundaries can occur by three well-defined processes. The first is Gibbsian segregation in which an element of minimal matrix solubility confines itself to a monolayer at the grain boundary. Classical examples include Bi in Cu and S or P in Fe. The second process involves the depletion of excess matrix solute by volume diffusion to the boundary. In the boundary, the solute atoms diffuse rapidly to precipitates, causing them to grow by the ‘collector-plate mechanism.’ Such grain boundary diffusion is thought to initiate “Diffusion-Induced Grain Boundary Migration,” (DIGM). This process has been proposed as the origin of eutectoid transformations or discontinuous grain boundary reactions. The third segregation process is non-equilibrium segregation which result in a solute build-up around the boundary because of solute-vacancy interactions.

All of these segregation phenomena usually occur on a sub-micron scale and are often affected by the nature of the grain boundary (misorientation, defect structure, boundary plane).
Evidence from in situ TEM straining studies for the mechanism of transfer of slip across a grain boundary
Authors: Robertson I.M. , Lee T.C. , Rozenak P. , Bond G.M. , Birnbaum H.K.
Published: June 2020

The bulk mechanical properties of a material will primarily be determined by the integrity of the grain boundaries which depends on the local chemistry and the boundary structure. Changes in the composition of the boundary may affect the strength of the atomic bonds through a redistribution of the electrons; this effect has been predicted from theoretical calculations1 but not determined experimentally. The structure of the boundary will be determined by the mismatch between the adjoining grains and it will affect the mechanism by which strain is transferred through the boundary. From static observations of the interaction between matrix and grainboundary dislocations the following scenario has been constructed for the transfer process through random boundaries; The interaction between the incoming matrix dislocation and those in the grain boundary cause the emission of a dislocation from a grain-boundary dislocation source into the adjacent grain. To preserve the contiguity of the grain boundary a residual dislocation will be created within the grain boundary.
Mechanical twinning and subgrain formation in ordered Ti50Ni47Fe3
Authors: Moberly W. J.
Published: June 2020

TiNi is an intermetallic compound with the B2(CsCl) crystal structure. As temperature decreases, it undergoes a martensitic transformation from cubic B2 to monoclinic B19', the reversibility of which is responsible for shape memory properties. Ordered intermetallics generally have limited ductilty, however, >50% elongation of TiNi has been produced by either warm or cold working. Consequently, thermomechanical processing has resulted in improved mechanical properties. TEM is required to characterize the deformation mechanisms (mechanical twinning and slip) and resulting substructures.

Substitution of 3%Fe for Ni into the binary TiNi alloy (Ti50Ni47Fe3) depresses the martensitic transformation, such that room temperature working does not stress induce the martensitic transformation. In order to improve the mechanical properties of this B2 intermetallic, fully annealed (875°C/2 hrs) bars have been cold swaged 10%,20%,30% and 40%, followed by different recovery annealing treatments. Additional samples have been warm swaged at 500°C. The structure is observed optically and by TEM, utilizing Philips' EM 400 twin and EM 430 super twin microscopes.
Progress in parallel-detection electron energy loss spectroscopy
Authors: Krivanek Ondrej L.
Published: June 2020

Parallel-detection electron energy loss spectrometers improve the detection efficiency by several hundred times compared to the traditional serial-detection spectrometers, but they have their own set of difficulties, such as the limited dynamic range of solid state detectors, the possibility of stray reflections of the intense zero loss beam giving rise to spurious background, and channel-to-channel gain variation. Fortunately, none of these difficulties is turning out to be insoluble. Here we report on improvements of the Gatan 666 parallel detection electron spectrometer in the areas of increasing the dynamic range of the detector, and in eliminating stray reflections.

The increase in the dynamic range of the detector was needed especially for low energy losses (high spectral intensities), which usually saturated the detector even at the minimum acquisition time of 12 msecs. Accordingly, we have developed an electron attenuator which uses a magnetic dipole to sweep the spectrum across the detector perpendicular to the dispersion direction (Fig. 1).
Structural control with ultrafine particles
Authors: Liu Jun , Sarikaya Mehmet , Aksay I. A.
Published: June 2020

Interest has increased in using ultrafine particles for structural control at the nanometer scale in making materials with improved properties. This study illustrates the possibility of controlling the structural development of nanosized particle aggregates by using surfactants to monitor the surface characteristics of particles. Both conventional and high resolution TEM are used to characterize the morphology of packing and the interfacial structures of particles. Experiments are carried out using both gold and silica particles, and the microscopy is performed with a Philips EM 430T at 300 kV.

Stable colloidal gold suspensions are produced by reducing gold chloride with sodium citrate at 100°C which produces gold particles that are approximately spherical with diameters of about 15 nm2. High resolution images reveal that they are not single crystals, but contain fine substructures, including low angle grain boundaries and twins (Figs. 1 and 2).
Microstructural development during heat treatment and deformation of an aluminum-silicon carbide composite
Authors: Mahon G. J. , Howe J. M.
Published: June 2020

Aluminum-SiC reinforced composite alloys are currently being considered for structural applications in the aerospace industry as a result of their increased strength and stiffness and reduced density when compared with their monolithic counterparts. However, the main drawback of these materials is their lack of tensile ductility and a decrease in fracture toughness. By deforming Al-SiC composites under hydrostatic pressure the tensile ductility can be increased. This enables changes in microstructure to be investigated after a few percent strain, thus providing information about deformation mechanisms in this class of materials. Conventional TEM techniques have been applied to study microstructural development during both heat treatment and deformation.

The material studied was AA2124 with 13vol.%SiC, commercially manufactured by ARCO Chemicals using a process of hot compaction and extrusion. The material was solutionized at 504°C for 4 h, quenched and aged at 177°C for 8 h.
HREM of carbon/metal and ceramic/metal interfaces in composite materials
Authors: Ishida Y. , Ichinose H. , Wang J. , Suga T.
Published: June 2020

As examples of interfaces between crystals of different type of bonding, interfaces of carbon fibre reinforced metal matrix composite and ceramic/metal diffusion-bonded interface are examined. It is our fundamental interest to understand the nature of hetero-bonding. Various problems originate from the difference of the nature of bonding. A difference in the thermal expansion coefficient alone produces internal stress accumulation that can lead to the fracture of the interface during cooling of the specimen. Stress relief by plastic deformation of metal would operate if no reaction layer is present at the interface. Otherwise, the fracture of the brittle component would result after the fracture of the reaction product itself or the interface between the brittle non-metal components. High resolution electron microscopy of the interface structures should give information useful for the assessment of the mechanism.

The first part is the observation of interface between carbon fibre and aluminium. Figure 1 shows the cross sectional view.
HREM studies of Al2O3 precipitates in Nb
Authors: Kuwabara M. , Spence J. C. H. , Rühle M.
Published: June 2020

High resolution electron microscopy (HREM) studies are, in principle, capable of determining the atomic structure of defects, such as interfaces,in crystalline materials. A quantitative evaluation of the defect structure requires, however, that the examined specimen fulfills certain conditions, e.g. low-indexed zone axes of both materials adjacent to the interface must be parallel to each other and to the electron beam. Well defined geometrical characteristics exist between a metallic matrix and oxide precipitates formed by internal oxidation of a metallic alloy.

Results will be reported on structure and defects at Nb/Al2O3 interfaces formed by internal oxidation of a Nb-2.9 at % Al alloy (oxidation conditions: 30 min. at 1820 K, po2 ∽6.10-5mbar). In addition, information on growth mechanisms of the Al2O3 precipitate can be extracted from the HREM studies. An extended paper of the research will be published separately.

Most Al2O3 precipitates possess a plate-like shape with dimension of (200...600) x (200...600) x (10...40) nm3.