bluuebunny/crossref_metadata_2025 huggingface dataset:
“Preparation of Single Crystalline Gold Films for ED Studies”
Authors: Peng Joseph D. C.
Published: June 2020

The relative intensities of the ED spots in a cross-grating pattern can be calculated using N-beam electron diffraction theory. The scattering matrix formulation of N-beam ED theory has been previously applied to imperfect microcrystals of gold containing stacking disorder (coherent twinning) in the (111) crystal plane. In the present experiment an effort has been made to grow single-crystalline, defect-free (111) gold films of a uniform and accurately know thickness using vacuum evaporation techniques. These represent stringent conditions to be met experimentally; however, if a meaningful comparison is to be made between theory and experiment, these factors must be carefully controlled. It is well-known that crystal morphology, perfection, and orientation each have pronounced effects on relative intensities in single crystals.

The double evaporation method first suggested by Pashley was employed with some modifications. Oriented silver films of a thickness of about 1500Å were first grown by vacuum evaporation on freshly cleaved mica, with the substrate temperature at 285° C during evaporation with the deposition rate at 500-800Å/sec.
A Many-Beam Technique for Enhanced Resolution of Partial Dislocations
Authors: Oblak J. M. , Kear B. H.
Published: June 2020

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.

A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.
Effect of Prior Microstructure on Neutron Damage in Stainless Steel
Authors: Laidler J.J. , Mastel B.
Published: June 2020

It has been found that cold-working prior to irradiation reduces the tendency for void formation in austenitic stainless steels irradiated to high fast neutron fluences at elevated temperatures. Reductions in cross-sectional area of the order 20%, for example, result in an order-of-magnitude decrease in the volume expansion of Type 316 stainless steel at fluences of about 3 x 1022 n/cm2. Little is known about the mechanism whereby the reduction in volume expansion is achieved, but it is generally assumed that the increased dislocation density in cold-worked stainless steel simply provides an increased concentration of sinks for point defects.

Foil specimens of Type 316 stainless steel were solution-annealed at 1100°C and then strained in tension 0.5, 1, 2, 4, 6, 10, and 15% Disc specimens 3mm in diameter were punched from the strained foils, the discs were coded and then encapsulated in helium-filled capsules. The capsules were irradiated in EBR-II at a temperature of 425°C to a fluence of 2.0 x 1022 n/cm2 (E > 0.1 MeV). The irradiated specimens were examined with the HEDL JEM- 1000 electron microscope at an accelerating voltage of 1,000 KV.
Radiation Damage Studies with the HVEM
Authors: Laidler J. J. , Mastel B.
Published: June 2020

One of the major materials problems encountered in the development of fast breeder reactors for commercial power generation is the phenomenon of swelling in core structural components and fuel cladding. This volume expansion, which is due to the retention of lattice vacancies by agglomeration into large polyhedral clusters (voids), may amount to ten percent or greater at goal fluences in some austenitic stainless steels. From a design standpoint, this is an undesirable situation, and it is necessary to obtain experimental confirmation that such excessive volume expansion will not occur in materials selected for core applications in the Fast Flux Test Facility, the prototypic LMFBR now under construction at the Hanford Engineering Development Laboratory (HEDL). The HEDL JEM-1000 1 MeV electron microscope is being used to provide an insight into trends of radiation damage accumulation in stainless steels, since it is possible to produce atom displacements at an accelerated rate with 1 MeV electrons, while the specimen is under continuous observation.
Effect of Accelerating Voltage and Specimen Temperature on Radiation Damage of Hexadecachloro Copper Phthalocyanine
Authors: Harada Y. , Taoka T. , Watanabe M. , Ohara M. , Kobayashi T. , Uyeda N.
Published: June 2020

In order for the single atoms in organic molecules to be resolved, considerably high magnification would be needed up to 100 to 200 thousand times. A highly bright illumination of electron beam is an essential requirement for this purpose, consequently giving rise to the serious problem of radiation damage. In the course of electron microscopy of organic crystals in respect to their epitaxial growth, it was found that Cuhexadecachloro-phthalocyanine (Cu-Cl16PC), which is wholly chlorinated Cu-phthalocyanine (Cu-PC), is remarkably resistant to radiation damage. This report is to show semiquantitatively the resistivity of the materials against the beam at various accelerating voltages and different specimen temperatures.

The specimen were thin crystalline films of Cu-PC and Cu-Cl16PC (Fig.1), all being prepared through epitaxial growth in an ultra high vacuum evaporator. The film thickness was carefully controlled to 200-300A by the use of a quartz crystal oscillator microbalance. The films were supported on carbon microgrid with small holes 1 or 2 microns in diameter as shown in Fig.2.
Re-Embedding of Specimens for Maximum Orientation
Authors: Brundage Margot , Dunn Robert F.
Published: June 2020

Re-embedding of plastic impregnated tissue blocks is easily accomplished when a combination of carnuba and Tenax dental waxes is used. This method is particularly helpful when combined with capsule flat end embedding, because the entire orientation range of the microtome can be utilized for final exact positioning of the specimen. A demonstration of both techniques will be given.

The advantages of re-embedding are: 1, complete freedom in orientation of the tissue, and 2, multiple segments of the same block can be used for various orientations. Re-embedding involves: 1, removal of a tissue block from the surrounding plastic (Fig. 1), and 2, orientation and embedding of the tissue into wax which has suitable support properties for sectioning.

Equipment and materials needed for re-embedding include: dissecting microscope; wax mixture ( carnuba 35%, Tenax 65%); empty gelatine capsules; dental carvers; dissecting needles; #7 Dupont forceps; Pasteur pipettes; specimen holders; razor blades; and gas flame.
Electron Microtomy Training: A Self-Contained Learning Package
Authors: Hopkirk Junarden W. , Glaeser Robert M.
Published: June 2020

An electron microtomy training program has been prepared and tested at junior college, state college and university levels. This program consists of 5 basic units: fixation, dehydration, embedding, sectioning and staining. The materials, planned and prepared by utilizing modern educational theory, are designed to be largely self-instructional. Both theoretical and laboratory materials are presented by various styles of programmed instruction. or fixation, dehydration, embedding and staining, the theoretical materials carry on a “dialog” with the student. Concepts or tasks are presented to him in a stepwise manner. He is then asked to interact with the materials by responding to questions which test his grasp of what has been taught. His correct responses are reinforced by the presence of the correct answer, either on an answer sheet at the end of the programmed lesson or immediately following the space provided for his answer.
The Application of Atom-Probe Techniques in Materials Science and Technology
Authors: Ralph Brian , Waugh A.R. , Hill S.A. , Southon M.J. , Thomas M.P.
Published: June 2020

This brief review attempts to summarize the main uses to which the atom-probe field-ion microscope and its variants have been put in the examination of materials. No attempt is made to produce a comprehensive list of all the studies made to date, rather the type of application is illustrated from recent studies.

The original form of the field-ion microscope was really limited to the acquisition of geometrical and crystallographic information on the fine scale distribution of defects and phases (e.g. 1). Even in these early applications, the study proved considerably more fruitful when other microstructural techniques, such as transmission electron microscopy, were applied in parallel. The advent of the atom-probe (AP) and imaging atom-probe (IAP) instruments allowed precise microchemical information to be obtained and these instruments have now been used for a number of detailed investigations of materials. In the main, these have divided into (I) studies of surface process and films (e.g. 2) and (II) investigations of phase distributions and segregation in the bulk (e.g. 3).
Radiation Damage of Support Films
Authors: Cohen H.A. , Chiu W.
Published: June 2020

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.

Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.
Imaging a Protein α-Helix by Dark Field Electron Microscopy
Authors: Andrews D. W. , Ottensmeyer F. P.
Published: June 2020

Elucidation of the fine structure of a protein, beyond its gross conformation, requires images of better than 10 Å resolution. In order to achieve such a resolution the normal techniques of staining the molecule must be avoided by substituting a technique such as dark field electron microscopy. However, to form a dark field image of such high resolution requires an exposure of approximately 1500 e/Å2. Exposures of this magnitude are so high that serious doubt has been expressed regarding the extent to which an image formed under these circumstances is an accurate representation of the molecule. Images of myokinase, protamine, glucagon, secretin, and ACTH indicate that reproducible 5-10 Å detail is present in the micrographs. Furthermore, for bacitrin, valinomycin, and the growth stimulators LMW-CSA N and B, biologically relevant information of 3-5 Å is present in averages prepared from a collection of images or even in single molecular images. Visual recognition has been used as a criterion to assess radiation damage in images of isolated molecules of protamine.
Crystal Packing ofE.ColiPorin (Matrix Protein)
Authors: Dorset D.L. , Engel A. , Garavito R.M. , Rosenbusch J.P.
Published: June 2020

Porin, a pore-forming protein spanning the outer membrane of E. coli (MW 36,500) has been isolated in homogeneous form after extraction in detergent. Electrical measurements on planar lipid membranes containing this protein indicate that it may be regarded as a paradigm of pore-forming transmembrane proteins. Therefore, a structural elucidation appears to be useful for correlating the pore geometry with the electrical measurements.

Extraction of cells with ionic detergents, with or without removal of the peptidoglycan layer, has been monitored by Steven et al. using high resolution electron microscopy. Optical and computer reconstructions of the images indicated a trimeric structure packing in plane group p3 (a = 77 Å). Three dense patches of negative stain were tentatively assigned to the pores, an arrangement corroborated later by strong interactions among triplet channels observed in the conductance studies.
Microstructural Studies of Laser-Melted Titanium-Rare-Earth and Titanium-Boron Alloys
Authors: O'Neal J. E. , Peng T. C. , Sastry S. M. L.
Published: June 2020

The feasibility of producing super-saturated solid solutions with small grain sizes and fine, stable, incoherent dispersoids was determined in laser-surface-melted Ti-rare-earth (RE) (RE = Er, Y, Gd, Nd, or Sc) and Ti-B alloys. Titanium specimens, coated with 0.02 to 1-μm thick electron-beam-evaporated rare-earth metal films or with a 10 to 25-μm thick boron slurry, were surface melted using a 1.5 kW continuous-wave CO2 laser beam at specimen traversing speeds of 0.5 to 40 cm/s. The microstructures of the laser-melted regions, determined by scanning and transmission electron microscopy, were correlated with the laser-processing parameters.

Figures 1a-1c are scanning electron micrographs of transverse sections of the laser-melted Ti-Y alloy at traversing speeds of 0.5, 10, and 30 cm/s respectively. The positions of the solid-liquid interfaces match the theoretically predicted melting isotherms for a specimen-beam coupling efficiency of 25%. Constant cooling-rate curves, calculated from the heat-transfer model for a rapidly moving, high-power, Gaussian source, are included in Figures 1a-1c. In the laser-melted Ti-RE alloys with the 0.2-μm thick rare-earth films, the microstructure consists of fine 10-20 nm dispersoids. The dispersoid size decreases with increasing specimen traversing speed as well as with increasing distance from the specimen surface. The volume fraction of the dispersoids increases with increasing film thickness and with melt depth. The equilibrium, coarse, constituent particles, which are generally observed in conventionally cast Ti alloys containing corresponding amounts of rare-earth elements, were completely absent in the laser-melted alloy.
Nucleation and Growth of Oxides on Iron
Authors: Kuroda K. , Mitchell T. E.
Published: June 2020

The growth of oxide nuclei on iron has been investigated both in situ and ex situ by electron microscopy using a Hitachi HU-650B HVEM and a Philips EM400T. Thin specimens of large grained polycrystalline 99.99% Fe were electrochemically polished and oxidized at temperatures in the range of 600 to 700°C and 10-5 torr air. At high temperatures (>600°C), it is well known that wustite (Fe1-xO) , magnetite (Fe3O4) and hematite (αFe2O3) form on iron. Previous TEM work (1) indicates that wustite and magnetite have a fixed epitaxy with (001) parallel to the iron substrate in the early stages of oxidation.

The shapes of oxide nuclei are often irregular with straight edges: triangular, rectangular and hexagonal, and sometimes circular. Figure 1 shows numerous oxide islands formed in situ at 650°C in the microscope column vacuum of 2 x 10-5 torr air. Black/white strain contrast observed across an island indicates that formation of oxide nuclei is similar to the nucleation of coherent precipitates on the surface.
Oxide Microstructure and Composition in Fe-Cr Alloys
Authors: Labun P. A.
Published: June 2020

Microstructure and microchemistry of oxides in Fe-Cr alloys have been investigated with a Philips EM400T equipped with an energy dispersive x-ray detector and a secondary electron detector.

Cold-rolled strips of Fe-Cr with 3, 9, 12, 18 wt.% Cr were vacuum annealed, electropolished to a thickness of about 0.1mm and punched into 3mm discs. Some of these discs were jet-polished for low pressure oxidation studies while other discs were oxidized first and then back-thinned. Pressures of 10-5 Torr (air) and 20 Torr (dry O2) were used at oxidation times of 5 and 30 minutes at temperatures in the range of 600° to 800°C.

Microstructures characteristic of alloys oxidized at the lower pressure (10-5 Torr of air) is shown in Fig. 1. Rectangular shaped light patches are seen in the alloys containing higher than 9%Cr. Energy dispersive analysis on these light patches gave high Cr concentrations relative to the starting matrix. When the electron beam was placed on the dark areas, quantitative analysis revealed concentrations the same as in the bulk alloy.
Analytical Electron Microscopy Characterization of Electric Arc Furnace Dust
Authors: Porter J. R. , Goldstein J. I. , Williams D. B.
Published: June 2020

Alloy scrap metal is increasingly being used in electric arc furnace (EAF) steelmaking and the alloying elements are also found in the resulting dust. A comprehensive characterization program of EAF dust has been undertaken in collaboration with the steel industry and AISI. Samples have been collected from the furnaces of 28 steel companies representing the broad spectrum of industry practice. The program aims to develop an understanding of the mechanisms of formation so that procedures to recover residual elements or recycle the dust can be established. The multi-phase, multi-component dust particles are amenable to individual particle analysis using modern analytical electron microscopy (AEM) methods.

Particles are ultrasonically dispersed and subsequently supported on carbon coated formvar films on berylium grids for microscopy. The specimens require careful treatment to prevent agglomeration during preparation which occurs as a result of the combined effects of the fine particle size and particle magnetism. A number of approaches to inhibit agglomeration are currently being evaluated including dispersal in easily sublimable organic solids and size fractioning by centrifugation.
Transmission Electron Microscopy of Fine Powder Samples
Authors: Koch E. F. , Walter J. L.
Published: June 2020

There is increasing interest in the possible use of parts fabricated from fine powders of metallic alloys for structural purposes because of possible improvements in strength both at low and high temperatures. Since powders can experience very high solidification rates, alloys prepared in powder form by rapid quenching may achieve a degree of homogeneity not obtainable by any other means. Also, these high solidification rates might make it possible to produce amorphous powders.

Determination of the microstructures of such powders may require transmission electron microscopy of either replicas or thin foils. This report describes a relatively simple method of preparing thin foils of powders, and illustrates the microstructures of fine powders of a nickel-base superalloy and of an amorphous alloy. The method involves incorporating the powders into a metal matrix, and thinning matrix and powder by ion-milling or by electropolishing.
In-Situ Formation of Clean, Single Crystal, and Electron Transparent Sapphire Substrates
Authors: Heinemann K. , Anton R. , Poppa H.
Published: June 2020

The availability of clean and thin substrates with micron-size single crystalline areas and a low defect density is a prerequisite for meaningful in-situ TEM epitaxial nucleation and growth studies. We are now reporting two related techniques for producing such electron transparent films of α-Al2O3 (sapphire). They have the added advantage of exhibiting grains of various crystallographic orientations.

A 1000 Å thick film of amorphous Al2O3, obtained by electrolytic oxidation of aluminum foil and subsequent chemical separation from the metal, was mounted on a 200 mesh W grid in the hot stage of the uhv specimen chamber of a 100 KV TEM equipped for in-situ experimentation. Electron-beam flash-heating with a 5-50 μm diameter beam at several A/cm2 current density (by removing the condenser 2 aperture and turning condenser 1 off) produced sapphire regions of 5-100 μm in size with several large grains. The size of the recrystallized areas increased with increasing duration of the flash (0.1 sec. to 1 sec.) and increasing beam current and diameter. According to Chang and our in-situ nucleation results with metal deposits, the sapphire surface is atomically clean after such high temperature treatment. The example of Fig. 1 shows recrystallization to a single grain. Thermal preheating of the amorphous film up to 800°C produced very fine polycrystalline Al2O3, but had no apparent effect on the result of subsequent e-beam recrystallization.
In-Situ Annealing of Metal Thin Films on Silicon
Authors: Chen L. J. , Mayer J. W.
Published: June 2020

In-situ dynamical experiments in the transmission electron microscope (TEM) have long interested electron microscopists. In designing and performing the experiments, it is important to minimize the influences of the factors, which include the specimen thickness, electron beam heating, electron irradiation and specimen environments that may affect the validity of in-situ experiments. Comparisons of the results with those of other experiments are also very desirable.

In microelectronic device fabrication process, it has become increasingly common to react a few hundred Å in thickness metal films with silicon substrate to form silicide contacts. Ni thin films on silicon have been chosen for in-situ annealing study since this system has been extensively investigated by Rutherford backscattering and glancing angle x-ray experiments. In-situ annealing of Co, Mo, Ti, Pd and W thin films on silicon have also been performed.

Ni films, 300 and 400 Å thick, were electron gun deposited on (001) n-type silicon. Thin foils for TEM examination were chemically polished from silicon side. A JEOL 100B microscope equipped with a side entry, single tilt hot stage was used for TEM study.
∣ḡ • b∣ = 0 Images of Small Precipates
Authors: Sykes L. J. , Hren J. J.
Published: June 2020

The authors have previously reported that small platelike precipitates formed during neutron irradiation of an Al-Cu alloy (A1 + 100 ppma Cu, irradiated to a fluence resulting in 0.26 dpa) produced ∣g•b∣ = 0 images similar to small dislocation loops. The precipitate images, however, contain detail indicating structures more complex than a simple dislocation loop. These observations were made as a continuation of the work of Farrell and Houston, who surveyed the radiation damage behavior of a large number of aluminum alloys. Our most recent work, using a refined model, suggests that much additional information can be derived about the nature of the precipitate from dynamical two-beam images.

Computer simulation of images was used to test models for the strain around the precipitates. EDS measurements, electron diffraction and SAXS failed to give useful clues as to the nature of the precipitates and so our model had to be based on a postulated relationship between the two-beam image and the strain field of small defects. Our results indicate that the defect in Figure 1 is a disc-shaped precipitate whose thickness is less than, and whose radius is greater than, the matrix material it replaces.
Dislocation Dipole Annihilation in Pure Sapphire (Al2O3)
Authors: Lagerlöf K.P.D.
Published: June 2020

Dislocation dipoles are often formed during deformation of sapphire (Al2O3) undergoing basal slip by edge-trapping of 1/3<1120> dislocations. Tne dipole concentration remains constant with increasing plastic deformation because the formation of new dipoles due to increasing plastic strain is offset by dipole annihilation by diffusive processes. Dipole annihilation in sapphire occurs in five distinguishable steps:(1) the dipole width fluctuates by self-climb, forming narrower and wider segments; (2) narrow segments transform into faulted dipoles by self-climb; (3) both perfect and faulted dipoles pinch off to form prismatic loops, primarily by self-climb; (4) faulted loops and dipoles rotate into edge orientation; and (5) loops grow or annihilate by climb. The kinetics of dipole annihilation thus depends on both self-climb and climb, that is, on both pipe-diffusion and bulk-diffusion kinetics, and so quantitative analysis of these changes during annealing will give valuable information on diffusion in sapphire. The objective of this paper is to present a brief qualitative analysis of the kinetics of dislocation dipole annihilation in pure sapphire.
Interfacing of a TEM/STEM System to a Computer
Authors: Hagemann P.
Published: June 2020

The use of computers in the analytical electron microscopy today shows three different trends (1) automated image analysis with dedicated computer systems, (2) instrument control by microprocessors and (3) data acquisition and processing e.g. X-ray or EEL Spectroscopy.

While image analysis in the T.E.M. usually needs a television chain to get a sequential transmission suitable as computer input, the STEM system already has this necessary facility. For the EM400T-STEM system therefore an interface was developed, that allows external control of the beam deflection in TEM as well as the control of the STEM probe and video signal/beam brightness on the STEM screen.

The interface sends and receives analogue signals so that the transmission rate is determined by the convertors in the actual computer periphery.
Micro-Computer Control for a HB501 STEM
Authors: Joy David C.
Published: June 2020

Micro-computers conveniently provide the basis of a powerful data collection, display and storage system for an electron microscope. In the example described here a Vacuum Generators HB501 STEM has been interfaced with an APPLE II micro-computer. The APPLE, with 48k of available core memory and a single mini-diskette system of 256k. byte capacity, was fitted with 16 input channels of analog-to-digital conversion (Interactive Structures AI-Ø2) and 8 output channels of digital-to-analog conversion (Interactive Structures AO-Ø3).

Figure (1) shows a block diagram of the system and its interconnections to the microscope. ADC channels Ø to 5 monitor the excitations of the six lenses (two condenser, one objective and three post specimen) of the HB501. These inputs are taken directly from the feedback shunt resistors in the lens power supply and fall directly in the range 0 to +5 volts required for the ADC. Channels 6 to 9 measure the X,Y coordinates and X,Y tilt-coordinates of the specimen stage, by monitoring the voltages derived from the position-sensing potentiometers on the stepping drive motors. These signals in the range ±0.5V are converted to the required 0 to + 5V level by operational amplifiers.
Small Computer System for Micrograph Analysis
Authors: Hainfeld J. F. , Wall J. S.
Published: June 2020

Cost reduction and availability of specialized hardware for image processing have made it reasonable to purchase a stand-alone interactive work station for computer aided analysis of micrographs. Some features of such a system are: 1) Ease of selection of points of interest on the micrograph. A cursor can be quickly positioned and coordinates entered with a switch. 2) The image can be nondestructively zoomed to a higher magnification for closer examination and roaming (panning) can be done around the picture. 3) Contrast and brightness of the picture can be varied over a very large range by changing the display look-up tables. 4) Marking items of interest can be done by drawing circles, vectors or alphanumerics on an additional memory plane so that the picture data remains intact. 5) Color pictures can easily be produced. Since the human eye can detect many more colors than gray levels, often a color encoded micrograph reveals many features not readily apparent with a black and white display. Colors can be used to construct contour maps of objects of interest. 6) Publication quality prints can easily be produced by taking pictures with a standard camera of the T.V. monitor screen.
Microchemical Analysis in the HB5 STEM
Authors: Houghton D.C.
Published: June 2020

The microchemical analysis of small extracted precipitates well dispersed on thin carbon support films has been carried out in a vacuum generators HB5 STEM, Particles in the size range ∼ 2 nm to several microns have been analyzed by a combination of simultaneous EDX and microdiffraction techniques. The major significance of this precipitate characterization is the high spatial resolution ∼ 5 nm and low detectability limit 5.10-20 g demonstrated by the EDX technique. However, a disturbing and frequently recurring feature of precipitate microanalysis was the detection of steep concentration gradients even within ∼ 10 nm precipitates.

The McMaster HB5 is equipped with a virtual objective aperture, a modified x-ray collimator(1) and a double tilt berylium specimen holder, which minimize continuum and instrumental contributions to EDX spectra and have allowed high precision microchemical analysis. EDX data was obtained from a region of interest by first imaging at 25.106 to attain thermal stability, then stopping the probe and simultaneously monitoring the microdiffraction pattern during EDX acquisition.
Microstructure and Chemistry of Grain Boundaries in Sensitized Low-Carbon High-Nitrogen Type 316 Stainless Steel
Authors: Hall E. L.
Published: June 2020

The resistance of stainless steel to sensitization can be increased by reducing the carbon content, since sensitization is caused by the formation of chromium-rich carbides at grain boundaries which depletes the boundary region of chromium. The reduction in carbon content also lowers the strength of the steel, but this can be counteracted by adding nitrogen, leading to a series of low-carbon high-nitrogen alloys which are promising candidates for applications in the nuclear industry. However, the effect of nitrogen on the phase relationships in stainless steel are complex, and the purpose of this study is to examine these effects.

Samples of 316 stainless steel with 16 w/o Cr, 9.8 w/o Ni, 2.5 w/o Mo, 0.03 w/o C, and 0.06-0.16 w/o N which had been solutionized and then aged at 600-700°C for 3-300 hours were used. Grain boundary phases were identified using electron diffraction, and grain boundary chemistry was measured using X-ray spectroscopy with a 10nm probe, either positioned directly on the boundary or stepped across the boundary with a spatial resolution of 50nm. The Cliff-Lorimer method was used to quantify the x-ray results.
TEM Observations of Dislocation Emission at Grain Boundaries in Response to Uniaxial (Tensile) Straining
Authors: Murr L.E.
Published: June 2020

Although it now seems to be generally recognized that grain boundaries and other interfaces are sources for dislocations, there are only scant few observations which tend to show convincing evidence for this. Murr earlier suggested that dislocation pile-ups in deformed metals and alloys (especially of low stacking-fault free energy) were primarily dislocation emission profiles, and more recent quantitative studies tend to unambiguously confirm this for uniaxial tensile deformation. Some of these features are illustrated in Fig. 1(a) and (b) which show a systematic increase in the number of dislocation profiles associated with grain boundary ledges at increasing tensile strains; observed in a Hitachi H.U. 200 F transmission electron microscope.

The results shown in Fig. 1(a) and (b) were obtained as part of a systematic study of dislocation emission following the straining of 304 stainless steel sheet samples in separate, conventional tensile tests. Consequently these observations, while qualitatively and even quantitatively convincing, lack the force of direct, in-situ observations.
Digital Fine Control for the Objective Lens Current of the EM-7
Authors: Pawley James B.
Published: June 2020

The lens currents of the AEI EM-7 are ganged to the ten (or twelve on the Mk II) operating voltages by reducing the reference voltage in proportion to V½. As a result, the most-used focus controls (Medium, Fine and Vernier) need cover a range of less than 10% of the total current. These controls each act by applying a fraction of the reference voltage through an appropriate scaling resistor to the input of the error amplifier where it is summed with a fraction of the actual lens current and a current from the magnification switch which compensates for changes in focus with magnification. Although our system has a measured total ripple and instability of <1 X 10-6 over 5 min, this performance is often compromised in practice by the poor performance of the 50 position switches which provide the Medium and Fine control voltages. Several users have replaced the original switches with others of superior performance (Muirhead D520/IM, Beckenham, Kent, U.K.) or by magnetically operated reed switches of their own design.
Microstructure and Magnetic Domain Wall Motion
Authors: Lin I. N.
Published: June 2020

MnZn-ferrites and Li-ferrites are soft magnetic materials used in telecommunication and entertainment electronics because of their high magnetic permeability and low magnetic loss characteristics. The magnetic properties of these materials are very sensitive to composition and microstructure. In the present paper, results of an investigation of the interaction of magnetic domains with the microstructural features are presented and the significance of such studied on microstructure-property relationships is discussed.

Lorentz microscopic technique in TEM has been used to study the domain wal structure and its interaction with grain boundaries, precipitates, pores, cracks, etc. in situ. Electron transparent specimens from bulk samples were prepared by ion beam milling technique and were examined in a Philips EM301 microscope operating at 100kV. The motion of domain walls was studied in situ by tilting the specimen so that there is a magnetic field applied to the plane of the specimen.
Transmitted Electron Detector and Grid Holder for a JEOL-U3 SEM
Authors: Smucker R. A. , Taylor M. E.
Published: June 2020

Energy dispersive x-ray microanalysis has become widely used as a supportive technique in studies of biological tissues. Installation and use of the x-ray detector in many instruments such as the JEOL-U3 S.E.M. is a relatively simple task. Microanalysis of bulk specimens is likewise relatively easy to accomplish in the JEOL-U3 S.E.M. However, in order to perform microanalysis on single cells or small areas within a tissue it is desirable to examine thin sections of embedded or cryo-sectioned cells and tissues. Until the present, there hasn't been a transmission electron detector available for the JEOL-U3 except for an expensive unit available from JEOL.

A prototype transmission electron detector was obtained for less than $1,000.00. The detector (Fig. 1) was constructed of a quartz light pipe and epoxied to an aluminum base which was mounted, in place of the normal secondary electron detector. A detector was made by forming an optical grade quartz rod to the appropriate geometry. The detection end and the PMT side were ground and polished as needed.
Three-Dimensional Model of Actin to 1.5 NM Resolution Determined by Electron Microscopy and Image Reconstruction
Authors: Fowler W.E. , Smith P.R. , Aebi U.
Published: June 2020

The highly conserved protein actin is found in all eucaryotic cells and is credited with a wide variety of functions, many of which requires its polymerization into double-helical filaments. Three-dimensional reconstructions from electron micrographs of negatively stained actin filaments have revealed structural detail of the molecule to about 3nm. Recently it has been found that the trivalent cation Gd+++ induces rabbit muscle actin to form microcrystals and tubes. We have modified and optimized these conditions to obtain large crystalline sheets made of Acanthamoeba actin suitable for high resolution structure determination. Depending on the ionic strength used, these sheets can assume three different polymorphic forms - ‘cylinders’, ‘square type’ and ‘rectangular type’ sheets - all of which can be derived from a common ‘basic’ sheet. The basic sheet is made of a two-dimensional near-rectangular lattice with lattice constants a=6.5nm and b=5.6nm; it is one actin molecule (4nm) thick and contains two molecules per unit cell which are related to one another by a two-fold axis of symmetry normal to the sheet plane.
Alkaline Dissociation Products ofLumbricus TerrestrisHemoglobin Viewed with the STEM
Authors: Kapp O. H. , Ohtsuki M. , Robin N. , Vinogradov S. N. , Crewe A. V.
Published: June 2020

Annelid extracellular hemoglobins are among the largest known proteins (M.W = 3.9 x 106), and together with the hemocyanins are the largest known oxygen carriers. They display oxygen affinities generally higher than those o vertebrate hemoglobins with Hill coefficients ranging from slightly higher than unity to values as high as 5-6. These complex molecules are composed of multiple copies of as many as six different polypeptides and posse: approximately 150 hemes per molecule.

The samples were diluted to 100-200 μg/ml with distilled water just before application to a thin carbon film (∽15 Å thick). One percent (w/v) uranyl acetate solution was used for negative staining for 2 minutes and dried in air. The specimens were examined with the high resolution STEM. Their general appearance is that of a hexagonal bilayer (Fig. 1), each layer consisting of six spheroidal subunits. The corner to corner hexagonal dimensic is approximately 300 Å and the bilayer thickness approximately 200 Å.
SSB Protein—Its Interaction with DNA and Use as a Tool in Studying Genome Structure
Authors: Chrysegelos Susan , Dunn Kathi , Griffith Jack , Manning Marcia , Moore Claire
Published: June 2020

A protein which binds tightly to single stranded DNA but not duplex DNA was first isolated from Escherichia coli (E. coli) by Sigal et. al and is called SSB for single stranded DNA binding protein. Together with SSB the gene 32 protein of T4 infected E. coli cells, and the gene 5 protein of phage M13 infected cells, are the best characterized members of the helix destabilizing family of proteins. They all share the properties (reviewed by Kbrnberg) of binding very tightly and cooperatively to single stranded DNA, of binding somewhat less well to single stranded RNA, and of binding poorly if at all to duplex DNA or RNA. In binding single stranded polynucleotides these proteins disrupt all secondary structure yielding a linear nucleoprotein complex. The details of binding however are very different from one protein to another and must reflect their functional roles in vivo.

Physical studies of SSB have showi it to exist as a 75,000 dalton tetramer in solution which is assumed to be the active unit.
A Quantitative Ultrastructural Study of Peripheral Blood Lymphocytes Containing Parallel Tubular Arrays in Epstein-Barr Virus and Cytomegalo-Virus Mononucleosis
Authors: Payne C. M. , Tennican P. M.
Published: June 2020

In the normal peripheral circulation there exists a sub-population of lymphocytes which is ultrastructurally distinct. This lymphocyte is identified under the electron microscope by the presence of cytoplasmic microtubular-like inclusions called parallel tubular arrays (PTA) (Figure 1), and contains Fc-receptors for cytophilic antibody. In this study, lymphocytes containing PTA (PTA-lymphocytes) were quantitated from serial peripheral blood specimens obtained from two patients with Epstein -Barr Virus mononucleosis and two patients with cytomegalovirus mononucleosis. This data was then correlated with the clinical state of the patient.

It was determined that both the percentage and absolute number of PTA- lymphocytes was highest during the acute phase of the illness. In follow-up specimens, three of the four patients' absolute lymphocyte count fell to within normal limits before the absolute PTA-lymphocyte count.In one patient who was followed for almost a year, the absolute PTA- lymphocyte count was consistently elevated (Figure 2). The estimation of absolute PTA-lymphocyte counts was determined to be valid after a morphometric analysis of the cellular areas occupied by PTA during the acute and convalescent phases of the disease revealed no statistical differences.
Melanosomes in Paget's Disease of the Human Nipple
Authors: Brinkhous A.D. , Seigler H.F. , Georgiade N. , Woodard B.H. , Ferguson B.J. , McCarty K.S.
Published: June 2020

Paget's disease of the nipple is a distinct pathologic entity associated with intraductal and/or invasive carcinoma of the breast. Paget's change in the nipple is observed in 2.5% of breast malignancies. It is associated with progressive clinical changes corresponding to progressive microscopic infiltration of the nipple epidermis by “Paget” cells. The underlying intraductal carcinoma typically involves the lacteriferous sinuses and is often multifocal. Theories regarding the histogenesis of Paget's disease include: 1) ductal carcinoma cells migrating into the nipple epidermis; 2) melanocytes; 3) squamous cells of the nipple; and 4) keratinocytes which differentiate into glandular malignant cells. The histologic characteristics of Paget's disease include nests of large pale cells with granular cytoplasm and hyperchromatic nuclei with prominent nucleoli, in the epidermis of the nipple. The tumors may show continuity with underlying carcinoma of the lacteriferous ducts. Paget cells are characterized ultrastructurally by an electron lucent cytoplasm with numerous polyribosomes, extensive rough endoplasmic reticulum and golgi, numerous large mitochondria, lysosome-like inclusions, lipid bodies, and glycogen particles.
Dupuytren's Contracture and Microvessels
Authors: Klscher C. W. , Speer D.
Published: June 2020

Dupuytren's Contracture is a nodular proliferation of the longitudinal fiber bundles of palmar fascia with its attendant contraction. The factors attributed to its etiology have included trauma, diabetes, alcoholism, arthritis, and auto-immune disease. The tissue has been observed by electron microscopy and found to contain myofibroblasts.

Dupuytren's Contracture constitutes a scar, and as such, excessive collagen can be observed, along with an active form of fibroblast.

Previous studies of the hypertrophic scar have led us to propose that integral in the initiation and sustenance of scar tissue is a profusion of microvascular regeneration, much of which becomes and remains occluded producing a hypoxia which stimulates fibroblast synthesis. Thus, when considering a study of Dupuytren's Contracture, we predicted finding occluded microvessels at or near the fascial scarring focus.

Three cases of Dupuytren's Contracture yielded similar specimens, which were fixed in Karnovskys fluid for 2 to 20 days. Upon removal of the contracture bands care was taken to include the contiguous fatty and areolar tissue which contain the vascular supply and to identify the junctional area between old and new fascia.
Control of Transcription of tRNA Genes
Authors: Sprague K.U. , Morton D. , Larson D.
Published: June 2020

Our laboratory is interested in the regulation of gene expression during eukaryotic development. Among the genes we are currently studying are those coding for alanine tRNA in the silkworm, Bombyx mori. These genes are particularly interesting because one Bombyx alanine tRNA species is constitutive -- that is, it is found in a variety of cell types -- while the other major alanine tRNA appears only in the silkgland. The silkgland-specific tRNA predominates when the highly specialized cells of this tissue are synthesizing large amounts of the alanine-rich silk protein, fibroin. The nucleotide sequences of the two alanine tRNAs indicates that they are encoded by different genes.

Our goal is to understand the molecular mechanisms governing the differential expression of Bombyx tRNAAla genes. Our approach is to isolate the genes with molecular cloning techniques, and to transcribe and process them in vitro. We have cloned 14 different genomic DNA fragments containing tRNAAla genes, and have developed faithful transcription systems from several different Bombyx tissues, including silkgland.
Increased Digitonin-Reactive Sterol in Myocardium from Rhesus Monkeys Given High Fat Diets
Authors: Barnard S.D. , Barnhart J.W. , Caldwell W.J. , Thompson C.F.
Published: June 2020

It is known that high fat, high cholesterol diets produce aortic lesions in monkeys similar to those seen in human atherosclerosis. Furthermore, through the use of digitonin-aldehyde fixation, subcellular sites of cholesterol accumulation have been discovered in atheromatous cells. However, little has been reported regarding the effect of such diets on the primate heart. The intent of the present study was to examine digitonin-aldehyde fixed ventricular myocardium from fat-fed rhesus monkeys for unusual sterol localizations. Test animals were maintained for 5 to 7 weeks on fat-enhanced diets which included either 21% coconut oil and 0.5% cholesterol or 11% butter oil, 11% coconut oil and 1.7% cholesterol. A rhesus monkey given a conventional monkey chow diet was used for comparative evaluations. The monkeys were sacrificed via exanguination while under ketamine anesthesia. Specimens from both the left and right ventricles were excised and immersed in the triple fix of Corbett et al. modified by the addition of digitonin to make 0.2%.
Prenatal Development of Muscle Spindles in the Mouse
Authors: Kozeka Kenneth
Published: June 2020

A closely spaced, serial, light and electron microscopic technique has permitted determination of the patterns of distribution, three dimensional cytoarchitecture and ultrastructural characteristics of developing muscle spindles in the fetal mouse extensor digitorum longus muscle (Figs. 1-6).

Spindle development begins at 15 daysin utero, when unmyelinated afferent nerves contact large, primary myotubes, located at the muscle's neurovascular hilum. By 17 daysin uterothe adult number of spindles containing one or two myotubes, can be identified in serial ultrathin sections through the myotube's sensory innervated region. While the primitive capsule of the spindle surrounds the intrafusal myotubes, it is initially confined to the sensory area and does not extend the length of the myotube. At this stage the peripheral regions of the intrafusal myotubes are morphologically indistinguishable from neighboring extrafusal myotubes.It is in this peripheral region that fusimotor innervation will develop.By following the spindles in serial, spaced (i.e., 15μm intervals), ultrathin transverse sections along their length, it is possible to establish the continuity of the sensory innervated region with the peripheral regions of the intrafusal myotube and to determine that fusimotor innervation is not present at 17 daysin utero.
Experimental Dissection of the Cellular Machinery Involved in Receptor Mediated Endocytosis and Translocation
Authors: Salisbury J.L.
Published: June 2020

The cultured human lymphoblastoid cell line WiL2 is a model system of choice for studies on receptor mediated endocytosis (RME). These cells display antigen receptor immunoglobulin of the IgM class (rIgM) as integral plasma membrane proteins which are present in diffuse cell surface distribution in unstimulated cells. Initially, rIgM occurs over uncoated regions of the plasma membrane. Crosslinking rIgM with multivalent antibody (ligand) results in the entry of ferritin-labelled ligand-rIgM complexes into the RME pathway (Figure 1). Stimulation of RME by ligand challenge results in an approximately three-fold increase in cell surface area displaying clathrin coats on the cytoplasmic face of the membrane. The newly formed coated pits are located directly beneath ferritin-labelled ligand-receptor complexes and their appearance is sensitive to the calmodulin directed drug trifluoperazine dihydrochloride (TFP). Calmodulin is a calcium dependent regulatory protein which recognizes local transient fluxes of cytoplasmic Ca+2 and activates a wide variety of enzymes and other protein systems. In addition, antibodies raised against calf brain calmodulin were used in indirect immunofluorescence studies.