bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces
Authors: Giggins C. S. , Tien J. K. , Kear B. H. , Pettit F. S.
Published: June 2020

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.

The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.

The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).
Interface Microstructures in Boron-Aluminum Composites
Authors: Hancock J. R. , Shaw G. G.
Published: June 2020

High-resolution studies of interface microstructures provide unique information on the role of interfaces in the mechanical behavior of boron-aluminum composites; some results related to diffusion kinetics, phase transformations, and bond integrity are presented below. Composite specimens were thinned for transmission electron microscopy by ion-bombardment.

The degradation of boron filaments in aluminum alloys is the result of chemical interaction over distances estimated to be < 2000 A (angstroms). Figure 1a shows a representative interface microstructure in a boron-6061 aluminum composite which was degraded during diffusion bonding at 500°C, 1 hr, 4000 psi. Aluminum boride(s) formed at intermittent sites at interfaces and reduced the ultimate tensile strength to only ≲ 60% of predicted values. A comparable interface is shown in Figure lb in a composite which was fabricated at 475°C; interface reaction products did not form and mechanical properties indicated that no degradation occurred.
The Effect of Inelastic Scattering on Aperture Contrast, Phase Contrast, and Electron Diffraction of Biological Objects
Authors: Turner J. N.
Published: June 2020

It has become increasingly obvious to all biological electron microscopists that staining and shadowing techniques must be eliminated, and the rapidly advancing technology of water trapping devices demands it. If we are to view biological systems at the molecular level or in a condition approaching the physiological state, contrast must be enhanced by electron optical means, not by specimen alteration.

Therefore, we have investigated Zernike type phase contrast, the principle of which is shown in Fig.1. Our phase plates consist of a carbon film carried on a 30μ objective aperture and are centrally drilled with a laser microscope made available by the American Optical Co. Because our phase plates incorporate a 30μ aperture the results are expressed as a ratio of phase contrast to 30μ aperture contrast. Fig.3 shows the early results of Dr. H. M. Johnson, previously of this laboratory.
Transmission Electron Analyzing Microscope (Team) and Scanning Transmission Eiectron Analyzing Microscope (Steam)
Authors: Melvin C. D. , Sprys J. W.
Published: June 2020

After much difficulty in attempting to measure accurately electron intensities in a conventional transmission electron microscope, it was decided that a quantitative electron analyzing capacility should be designed. Such an instrument should be capable of analyzing both the number and energy of electrons at any point in an image or diffraction pattern. Such a system was developed in the following manner: a set of deflection coils was mounted between the objective lens and viewing screen, an interchangeable aperture was placed in the center of a grounded screen, a retarding grid of variable voltage was positioned behind the aperture, and an electron detector was placed behind the grid, as shown in figure la. Many different types of detection devices can be used. A Faraday cup is useful for quantitative measurements and a light pipe-photomultiplier system is useful for high sensitivity and fast response time with good counting accuracy.
Closed Circuit TV Microscopy
Authors: Marsh Peter A. , Price L. Dale , Mullens Troy J.
Published: June 2020

We recently installed a fiber optics TV display system made by N. V. Philips Gloeilampenfabrieken, Eindhoven, Holland, on our EM-300. The TV chain consists of a highly efficient transmission fluorescent screen deposited onto a fiber optics disc. In direct contact with this disc is a fiber optics window on a special Plumblcon tube in the TV camera. The camera signal is viewed on a 12-inch monitor having an EIA scanning system, 525 lines/sec, 30 frames/sec, 2:1 interlace. Horizontal resolution is 135 lines with a band width of 5 MHz.

The camera and fiber optic adaption piece is fitted at the bottom of the microscope column in place of the 70 mm camera. Normal use of the 35 mm and plate cameras remains possible. If desired, the TV system and the 70 mm camera can be interchanged in less than 30 minutes. Cables connect the camera to a control unit and control box.
Annealing Twins in Pure Aluminum
Authors: Murr L. E. , Wong G. I.
Published: June 2020

While aluminum is perhaps one of the most commonly available pure fee metals, it is relatively unresearched with regard to grain boundary energetics. By comparison with other fcc pure metals, annealing twins are rarely observed in Al. and annealing twin bands identified by two parallel {111} planes separating a twinned crystal portion from matrix grain - while common to essentially all other fcc pure metals - have never been unambiguously observed in pure Al. Additionally, grain corner twins prominent in other fcc metals (and alloys) and consistent with the twin- formation theory of Fullman and Fisher, have never been observed in g pure Al. Finally, of all the studies of Al grain boundary structures cited only the work of Sargent employed the techniques of transmission electron microscopy and selected-area electron diffraction to identify the twinning plane as (111).
Hydrogen-Assisted Cracking by Microscopic Plasticity Mechanisms
Authors: Beachera C. D.
Published: June 2020

The recently proposed model for hydrogen-assisted cracking (hydrogen “embrittlement”) which states that such cracking in steels occurs by hydrogen diffusing into the metal ahead of the crack and lowering the local resistance to plastic flow has been further substantiated in other steels.

The term hydrogen “embrittlement” was coined long before electron fractography, and it is based on the observation that many steels that normally show considerable ductility when tested in the absence of hydrogen, frequently lose this macroscopic ductility when the steels contain hydrogen and are maintained under a high stress. Electron fractography has shown that, while this macroscopic plasticity is minimized, it still persists on the microscopic scale. This plasticity may be seen in Figs. 1 and 2, for two different steels. Figure 1 is from the fracture surface of a 13Cr-8Ni-Mo steel and Fig. 2 is from a 250 ksi yield strength grade of maraging steel.
Ion Etching of TMV
Authors: Rizk Nabil , Bendet Irwin
Published: June 2020

Carbon films can be made hydrophilic, and therefore more suitable for supporting preparations of proteins or nucleic acids, if they are first subjected to an AC glow discharge in vapors of amyl amine (E. Kellenberger, personal communication). In our laboratory, we have observed that grids lose their carbon film if they are placed close to the cathode in a DC glow discharge apparatus. Further investigation of this phenomenon has shown that positive ions will affect the surface in the same way as a milling machine. Fig. 1 is a schematic of the ion gun built and used in our studies. Shown are the relative positions of the fixed cathode, movable anode and rotatable target which supports the grids. The extent of etching of the biological material being investigated can be varied, and is a function of the time, voltage, and angle which the specimen presents to the ion beam.
The Atom Probe and Its Application to Steels
Authors: Brenner S. S. , Miller M. K.
Published: June 2020

Solute atoms, even in minute quantities, often markedly influence the processing and properties of solids. To understand these effects requires the analysis of highly localized regions. Many techniques have been developed to make such measurements. Among these is the atom probe (AP) which is unique in its atomic-dimensioned spatial resolution and its mass-independent sensitivity.

The AP consists of a field-ion microscope (FIM) and a time-of-flight mass spectrometer, Fig. 1. The needle-shaped specimen is mounted on a cryogenically-cooled goniometer stage facing a CEMA and phosphor screen. A central hole in the imaging assembly serves as the entrance aperture to the spectrometer flight tube which is typically 1-2 mm in length. The only focusing lens is an Einzel lens which converges the trajectories of the ions entering the drift tube. Ancillary equipment includes power supplies to provide the specimen with short (20 ns) high voltage pulses superimposed on a DC potential of up to 30 kV.
Cryoprotection of Electron-Irradiated Organic Crystals
Authors: Müller K.-H. , Zemlin F. , Zeitler E.
Published: June 2020

There is an urgent interest in analyzing the structure of biomolecules by EM imaging. In order to reduce the quantum noise under the level of the inherent contrast C of the structure imaged, a minimum dose Dm=4/C2r2is required when a structure detail of size r is to be detected. (The factor 4 is just the square of the signal-to-noise ratio, justified by experiments.) Setting r to about .4 nm and C to about 10% the required minimum dose amounts to 2000 e/nm2. Unfortunately at room temperature this minimum dose destroys most biomolecules. One way out of this dilemma seems to be cooling the specimen to He temperature.

Experiments in an improved superconducting electron microscope (Siemens system 2) have been performed with the aim of confirming and/or refuting measurements by others in this very well defined experimental situation. The fading of diffraction patterns was used to characterize the radiation damage (Fig. 1), yet the implication for the image formation was introduced by the size of the pixel.
Precipitate Anisotropy in RSR 197 Superalloy
Authors: Kersker M. M. , Aigeltinger E. A. , Hren J. J.
Published: June 2020

With the possible exception of Au-Cu alloys, no ordering system has been explored as intimately as the Ni-rich Ni-Mo system. The ordered intermediate metastable phases that form in this binary have been extensively reviewed. One binary intermediate, the Ni3Mo metastable DO22 phase, also appears in RSR 197 alloy (Al-13, Mo-9, Ta-2, Ni at.%) and in many other Ni-Mo-Al-X alloys as well. The most obvious difference (beyond compositional differences) between Ni-Mo binaries and the higher order systems is the presence of a second phase, γ', Ni, Al, a Dl2 superlattice, in addition to the disordered γFCC phase. This stable Dl2 phase is present before the intermediate metastable DO22 phase and has an due to the high ratio of Mo partitioned to the γ phase, in contrast to most γ/γ' superalloys where . The presence of this Dl2 phase has interesting effects on the precipitation morphology and crystallography of the subsequently formed DO22 phase.
Cobalt Effect on Creep Behavior of Nickel Solid Solution Alloys
Authors: Lin L. S. , Law C. C. , Blackburn M. J.
Published: June 2020

To understand the role of cobalt in nickel-base superalloys, multicomponent nickel solid solutions with various amounts of cobalt were studied. Alloys A, B, C and D which contain cobalt at 30, 17, 8 and 0, respectively, and constant concentrations of Cr(25), Mo(5), Al(0.5), Ti(0.5), Nb(0.4), Hf(0.1), all in weight percent, were produced by casting. Compressive creep tests of these alloys were conducted at temperatures between 650°C and 810°C. Table 1 shows the minimum creep rates at 704°C at a stress of 120% of their respective yield strengths. It can be seen that the alloy without cobalt (Alloy D) creeps at a rate 20 times faster than Alloy A with 30 wt.% cobalt and the values for Alloys B and C with intermediate cobalt contents fall between Alloys A and D. Thin foil studies have revealed that the differences can be attributed, in part, to (i) change of stacking fault energy with cobalt, (ii) precipitation of fine gamma prime particles during creep.
Defect Structure and Composition of Fe1-xO
Authors: Lebreton C. , Hobbs L. W.
Published: June 2020

Wüstite, Fe1-xO, is the principal oxide scale formed on iron above 843 K. Wüstite exhibits a broad range of non-stoichiometry (0.05 < x < 0.15), and even in equilibrium with iron maintains a minimum 5% iron deficiency. Its large departures from stoichiometry are accommodated by octahedral iron vacancies which associate into tetrahedral complexes about ferric ion interstitials. Despite a great many studies, further details of the defect structure have been slow in coming. We report here additional defect microstructure information for wüstite in equilibrium conditions and after annealing below the 843 K eutectoid, as revealed by electron diffraction, high-resolution dark-field and lattice-imaging techniques.

Single crystals, prepared by a floating-zone method, were equilibrated within the wüstite phase field in CO/CO2 atmospheres providing controlled oxygen fugacity. Samples were oil-quenched so that they reached room temperature within a few seconds and are therefore expected to have retained the initial equilibrium structure.
The Direct Identification of Stacking Sequences in ZnS Crystal by High Resolution Electron Microscopy
Authors: Kang Zhen Chuan
Published: June 2020

An infinite variety of stacking sequences between that of the ideal 2H and 3C end-member structure is possible. More than 150 ordered ZnS phase (polytypes) have been reported, the majority of them in synthetic ZnS. Some degree of stacking disorder is very common, and completely disordered structures have also been reported. No direct identification of stacking sequence has been published, although Hashimoto reported structure image of synthetic ZnS. High resolution lattice imaging at the 2.5Å level with tilted-beam illumination established that essentially one-dimensional information about individual stacking sequences was directly obtainable. It has been possible to identify directly the detailed stacking sequence in longer period polytypes and around the vicinity of stacking faults, without recourse to any confirmatory calculations based on postulated trial structures. We have applied this method to the direct identification of stacking sequences in disordered ZnS crystals.
High Resolution Imaging of Semiconductor Interfaces
Authors: Sinclair R. , Ponce F. A. , Yamashita T. , Bravman J. C.
Published: June 2020

One of the most important commercial areas in contemporary materials science concerns the miniaturization of integrated circuits. As the size of such devices decreases, their operation becomes more critically influenced by the presence of defects and by the nature of the interfaces involved. High resolution TEM can play an important role in determining fundamental aspects of the structure of these materials. The present article describes some of our recent work on this problem.

The first important step in this business is the fabrication of good specimens. It is necessary to arrange for the interface or defect in question to be parallel to the electron beam for obtaining the maximum degree of structural information. This requires making “cross-section” TEM specimens which is achieved by the following procedure. Firstly, several circuits are sandwiched together using an appropriately strong glue (e.g., “Micromeasurements 610”). They are then sliced into thin slabs (approximately 1 mm thick) using a diamond saw, cut into 3 mm diameter discs, mechanically polished to reduce the thickness and finally ion-beam milled to electron transparency. The composite is generally fragile and so careful handling is required in each of these stages. The yield of high quality specimens for high resolution work is often low and perfection of the experimental approach is necessary before it becomes routine.
The Morphology and Crystallography of Diesel Particulate Emissions
Authors: Stevenson R.
Published: June 2020

A study has been made of the morphology and crystallography of particulate emissions from indirect injection diesel engines. This particulate matter consists substantially of carbon (although hydrocarbons can be extracted with solvents). Samples were collected in a diluted exhaust stream on amorphous carbon films and examined in a JEM-200C electron microscope operated in the TEM mode with an accelerating voltage of 200 KV.

The morphology of the diesel particles, as shown in Fig. 1, markedly resembles carbon blacks and consists of an agglomeration of quasispherical subunits arranged in chains or clusters. Only limited changes in morphology were observed as the number of subunits in the particle increased (although larger particles tended to be more cluster-like than the extended chain shown in Fig. 1). However, a dramatic effect of the number of subunits was observed on the character of the diffraction pattern. Smaller particles yielded a diffraction pattern consisting of very diffuse rings typical of turbostratic carbon; the diffraction patterns from the larger particles, however, although qualitatively similar, exhibited much sharper and less diffuse ring patterns.
Preliminary Characterization of Pacific Ocean Manganese Nodules
Authors: Huggins C. W. , Haynes B. W. , Virta R. L.
Published: June 2020

For the past year the Bureau of Mines, Avondale Research Center, has been doing extensive characterization on Pacific Ocean nodules from the Clarion-Clipperton fracture zone, which extends from off the coast of Mexico and Central America in a general east-west direction toward the Hawaiian Islands. These nodules are a potentially valuable new source of Ni, Co, Cu, and Mn. All of these metals are essential to the U.S. economy. Three million tons of nodules would produce about 75 percent of the domestic need for Mn, 10.0 percent for Ni, 1.2 percent for Cu, and 45 percent for Co.

Manganese nodules (figure 1) are basically concretions of hydrous manganese oxides and appear to have a simple concentric layer growth structure forming around a nucleus. The growth rate ranges from 1 to 10 mm per million years depending on surrounding conditions. After deposition, only minor changes occur in a layer. These changes include replacement of some Mn by other metals such as Co, Ni and Cu in the water circulating through pores in the nodule. Some of the minerals deposited initially have partial replacement by oxides.
Direct Electron Beam Fabrication of a Photo-Conductor
Authors: Joy David C. , Schmidt Paul H. , Kaplan M. L.
Published: June 2020

Electron beam irradiation of organic molecular crystals almost invariably leads to a rapid loss of crystallinity, followed by gross mass loss at higher doses. One interesting exception to this sequence of events was described, by Jones, Thomas and Williams who showed that the irradiation of p-terphenyl, at temperatures below 130°K, converted the stable triclinic phase to the characteristic room temperature monoclinic structure. For doses above 0.16 coulomb.cm-2 this transformation was permanent and could not be reversed by thermal cycling. We report here another electron-beam induced transformation, the end product of which has technologically useful properties.

3,4,9,10-Perylenetetracarboxylic di-anhydride, C24H8O6 (PTCDA), the structure of which is shown in figure 1, when vapor deposited to a thickness of a few thousand angstroms forms a red transparent organic film. In this form it is stable to relatively high temperatures (300°C) does not appear to degrade after several months of room temperature storage and is electrically insulating.
A Practical Method for Removing Plural Scattering from Core Edges in EELS
Authors: Leapman R.D. , Swyt C.R.
Published: June 2020

Core edges in electron energy loss spectra are generally complicated by thickness effects involving plural inelastic scattering. The fine structure can be modified and errors can be caused in quantitation based on measured edge intensities. Sometimes plural scattering can confuse even identification of elements. In this paper we describe a practical method for eliminating these difficulties.

We derive the single scattering distribution, assuming valence electron excitation is small in the core loss region, a reasonable approximation for edges above 100 or 200 eV and for thicknesses of a few hundred Å. We can then separate the spectrum into a “high loss” region H(E) consisting of core edges (less background) and a “low loss” region L(E) containing the zero loss peak, plasmons and one-electron excitations.
Imaging and Analysis of Surfaces Using Diffracted Electrons
Authors: Cowley J. M.
Published: June 2020

Electrons diffracted from the surfaces of crystals have recently been used very effectively for the imaging of the structure of the surfaces in both TEM and STEM instruments. With an ultra-high vacuum TEM instrument the group at Tokyo Institute of Technology have demonstrated the value of the technique for imaging monatomic surface steps, dislocations and surface superlattices on silicon. With a STEM instrument it is possible to combine imaging with a lateral resolution of 10A or better, and microdiffraction and microanalysis of small areas of the surface. In this paper we report further STEM observations illustrating some characteristics of these modes of surface study.

Figure 1 shows two views, with different magnification, of the surface of a bulk MgO crystal, having dimensions 0.5 to 1mm, formed by cleaving a larger crystal. In order to mount such crystals with a minimum of handling and without adhesives which might introduce impurities they were enclosed in precleaned folding grids for mounting in the high resolution goniometer cartridge. The images were obtained using the (600) reflection with the beam close to the [010] direction.
Experiments in Bright-Field Imaging with Hollow-Cone Illumination
Authors: Kunath W. , Weiss K. , Zeitler E.
Published: June 2020

Bright-field images taken with axial illumination show spurious high contrast patterns which obscure details smaller than 15 ° Hollow-cone illumination (HCI), however, reduces this disturbing granulation by statistical superposition and thus improves the signal-to-noise ratio. In this presentation we report on experiments aimed at selecting the proper amount of tilt and defocus for improvement of the signal-to-noise ratio by means of direct observation of the electron images on a TV monitor.

Hollow-cone illumination is implemented in our microscope (single field condenser objective, Cs = .5 mm) by an electronic system which rotates the tilted beam about the optic axis. At low rates of revolution (one turn per second or so) a circular motion of the usual granulation in the image of a carbon support film can be observed on the TV monitor. The size of the granular structures and the radius of their orbits depend on both the conical tilt and defocus.
The Selection of Beams for Multi-Beam Dynamical Theory Calculations Used for Weak-Beam Dark Field Image Interpretation
Authors: Avalos-Borja M.
Published: June 2020

The use of computers as aid for TEM image interpretation has increased considerably during the recent years. In particular, the interpretation of weak-beam dark field (WBDF) equal thickness fringes for the determination of the habit of nanometer-size crystallites has been emphasized to be dependent on the concomitant ability of image intensity calculations using the many- beam dynamical theory (DT). On the other hand, some researchers have been using simple 2-beam kinemathical theory (KT) calculations for similar image interpretations. No attempt has been reported to quantify the necessity and the limitations of either approach. We are now reporting first results of comparative DT and KT calculations, emphasizing the definition of the number and selection criterion of the beams that should be included in DT calculations which are intended to be superior in accuracy to KT calculations.

We modified a program developed by Yacamán, following the n-beam dynamical theory principles, to accept up to 100 beams at various selection criteria, and studied the influence of the number and selection criterion of the beams included in the calculation on the extinction distance and its dependence on the crystal thickness.
A Relatively Inexpensive Microprocessor-Linked Digital Plamimeter for Electron Microscopic Morphometry
Authors: Peachey Lee D.
Published: June 2020

Stereology provides a theoretical basis for powerful morphometric methods for the estimation of three-dimensional structural parameters from two-dimensional electron micrographs of cells and tissues. These methods assume at the start that one has a sufficiently large set of micrographs containing valid structural data. The task of obtaining from these micrographs the large quantity of data needed to get statistically valid results has been eased in two general ways. Sampling of data in the micrograph can be done rapidly by point and intersection counting methods. An alternate method, planimetry, obtains all the data in the micrograph, but in general is more time-consuming than point and intersection counting. Some of the relative inefficiency of planimetry is compensated when a digital planimeter is coupled with a computer. Areas and lengths can be computed simultaneously as fast as profiles are traced. Furthermore, rapid and numerically accurate compilation and statistical analysis of the data can be done automatically as the planimetry is done, not as a separate step after the data have been obtained.
Analytical Microscopic Analysis of Precipitates in Hastelloy Alloy C-276
Authors: Raghavan M. , Berkowitz B. J. , Scanlon J. C.
Published: June 2020

The present investigation was conducted to characterize the second phase particles in Hastelloy C-276 using an analytical Scanning Transmission Electron Microscope in order to understand their effect on the mechanical and Stress Corrosion properties of the alloy. Investigation in our 1aboratoryO) and previous published reports(2-4) have identified two types of precipitation reactions in this alloy. At temperatures in the range of 300-650°C, the alloy precipitates an ordered phase of the type Ni2(Cr, Mo)(1,2). This precipitation reaction is homogeneous with no preferential precipitation at the grain boundaries or twin boundaries. At temperatures above 650°C, several precipitate phases were observed to nucleate heterogeneously at boundaries and using X-ray diffraction techniques, the precipitates were previously identified as the μ, M6C and P phases(3-4). The present investigation was carried out to determine the composition of these second phase particles and this article describes the characterization of these precipitates using X-ray microanalysis and microdiffraction techniques.
Grain Boundary Segregation of Bismuth in Copper
Authors: Michael J. R. , Williams D. B.
Published: June 2020

Bismuth is known to segregate to grain boundaries in copper resulting in embrittlement and intergranular failure at low stress levels. This segregation has been studied primarily by Auger Electron Spectroscopy (AES). The applicability of scanning transmission electron microscopy (STEM)and Energy Dispersive Spectroscopy (EDS) to the study of equilibrium grain boundary segregation has already been demonstrated and the aim of this study is to determine the degree of segregation as a function of time and temperature. The major advantage of STEM over AES is that STEM does not require fracturing of the specimen, so the boundaries to be studied are left undisturbed. Thus, this technique is also applicable to systems which do not exhibit intergranular fracture.

Cu-Bi specimens were prepared by evaporating Bi onto both sides of 3mm Cu discs, which were then heated for 1 week at 400°C to allow the Bi to diffuse into the Cu. The samples were then aged at 450, 550, 600, 650, and 700°C for 3 days and 12 days, ion-thinned and then examined in a Philips EM 400T TEM/STEM with an EDAX detector and EDAX 9100 analyzer. If necessary, the specimens were tilted such that the boundaries were parallel to the electron beam.
Applications of Computers in Electron Microscopy
Authors: Fisher M. , Lee R. J. , McCarthy J. J.
Published: June 2020

During most of the fifty years since the invention of the electron microscope, the primary hands-on operating role of the microscopist has been scanning specimens, selecting, and recording fields/features of particular interest. Now, microscopy is entering a new era. The advent of microcomputers and microprocessors is about to modify the customary role of microscopists.The new technology will enable them to respond to a growing need for more quantitative data than can be generated by conventional methods based on manual control of data acquisition and processing.

During the last 20 years, attention was devoted to the physics of image formation in terms of electron-solid interactions, interference phenomena, and lens performance. During this same period, considerable effort was also put into elucidating the specific nature of many newly discovered structures including crystal defects, interfaces, membranes, second phase particles, and numerous other perturbations of the specimen “matrix.” Sophisticated mathematical descriptions of image contrast, i.e., intensity as a function of position, are now available to predict the appearance of most structures of interest.
Dual Column Wafer Inspection SEM
Authors: Buchanan Robert
Published: June 2020

With the trend in the semiconductor industry towards smaller and smaller IC structures, there is a growing requirement for visual inspection systems with resolution beyond that of the optical microscope. Further requirements are that wafers up to 6" can be handled, and that any part of the wafer be viewed at normal incidence and tilted at angles up to about 60° with a provision for rotating the specimen about the center of the field of view. The system must neither contaminate the wafer, nor damage it in any way.

General purpose scanning electron microscopes have found limited application in wafer inspection for a number of years. These instruments, however, have satisfied only some of the requirements listed above. In particular, the requirement to tilt large wafers to angles as high as 60° has required operation at long working distances with resultant poor image resolution, especially at low accelerating voltage. A further major limitation has been the inability to rotate the wafer about the center of the field of view at all viewing locations.
Morphologic Evidence Suggesting that Bacteria Producing Choriogonadotropin-Like Factor are Revertants of Intracellular Cell-Wall-Deficient Variants
Authors: Acevedo H.F. , Pardo M. , Campbell-Acevedo E.A. , Slifkin M. , Domingue G.J. , Koide S.S.
Published: June 2020

Bacteria capable of synthesizing and incorporating in their cell membranes a material with immunological, physicochemical, and in vitro and in vivo biological properties similar to those of the human trophoblastic hormone, chorionic gonadotropin (CG), have been isolated from human tissues and urine. The findings are of great biological importance since to date, each one of the strains of bacteria demonstrating the capability to express the CG-like material was isolated from a patient with clinical cancer, and also because it is the first demonstration of biosynthesis of a biologically active “glycoprotein hormone-like” material by procaryotes.

In order to establish if morphologic and/or ultrastructural differences exist between a bacterium that synthesizes CG-like material (CG-producer) and those that do not, transmission electron microscopy studies have been done in eight strains of CG-producers. There were five strains of Staphylococcus epidermidis and single strains of Staphylococcus simulans, Streptococcus faecalis, and a bacterium tentatively identified as aerobic “coryneform-like.”
Morphology and Ultrastructure of Mastigocladus Laminosus
Authors: Nierzwicki S. A. , Maratea D. , Balkwill D. L. , Mehta V. B. , Stevens S. E.
Published: June 2020

Mastigocladus laminosus is a filamentous cyanobacterium (blue-green alga) with a complex morphology. It is the only thermophilic cyanobacterium known to fix atmospheric nitrogen. Relatively little is known of the detailed morphology and ultrastructure of this organism, especially in regard to its nitrogenfixing abilities. The purpose of this study was to characterize the morphology and ultrastructure of M. laminosus, using SEM and TEM respectively.

The complex morphology of M. laminosus is shown in Fig. 1. Young filaments had a diameter of ∼2.2 μm and consisted of relatively uniform, rod-shaped cells. The uniformity of these filaments was interrupted only by the occasional appearance of heterocysts (nitrogen-fixing bodies) about 4 μm in diameter (not shown). As young filaments elongated and aged, the older sections increased in diameter to 10-12 μm. Their cells became rounder and less uniform with respect to size and shape. Branches often formed in the older sections, giving rise to new young filaments.
Structure of Freeze-Fractured, Deep-Etched F-Actin
Authors: Ruben G.C. , Allen N.S. , Travis J.L.
Published: June 2020

High resolution electron microscopic images of F-actin, which had been rapidly frozen, freeze-fractured and deep-etched, have been compared with conventional negatively stained images. Our methods permit the stereoscopic visualization of native actin filament substructure

F-actin, prepared by the method of Spudich and Watt (1) was dialized against 2 mM MgCl2and 5 mM Tris at pH 7. F-actin was then negatively stained (1% uranyl acetate at pH 4.5) on 10 nm carbon films (2) or frozen on Balzer's gold pedestals in liquid propane at -190°C. After placing the specimen in a Balzer's 300 freezing microtome, both electron beam guns were out-gassed for two minutes at a current setting of 5. During this process the knife arm (-196°C) covered the sample. The specimen was freeze-etched for 3 minutes at -97°C under the knife arm. Then the sample stage was cooled (-120°C) for two minutes (5xl0-7torr) before the Pt-C was evaporated at a 45° angle to a preset thickness of 2.5 and 2.9 nm on a QSG quartz crystal thin film monitor.
A Scanning Electron Microscopy Study of the Structure of Human Mitotic Chromosomes
Authors: Adolph Kenneth W.
Published: June 2020

The organization of the fundamental 200-300A chromatin fibers in metaphase chromosomes has been investigated by various techniques of electron microscopy. Thin sectioning studies have suggested that a primary mode of fiber packaging is a radial distribution of loops. In these sectioning studies, the arrangement of fibers was observed by adjusting the concentration of divalent cations (Mg2+, Ca2+) in resuspension buffer to slightly expand the chromosomes and separate the fibers. Scanning electron microscopy has now been applied to obtain information about the surface organization of isolated chromosomes. As with thin sectioning, the degree of expansion of the chromosomes was controlled in a defined and reproducible manner by adjusting the concentration of divalent cations.

Chromosomes were prepared from metaphase-arrested suspension cultures of HeLa cells. The isolation buffer contained 50 mM NaCl, 5 mM HEPES pH 7.4, 5 mM MgCl2, 0.5 mM CaCl2, 0.1 mM PMSF, and the mitotic cells were disrupted in a Dounce homogenizer with the aid of detergents.
Filipin-Sterol-Complexes in Finch and Mouse Cardiac Muscle
Authors: Sommer J. R.
Published: June 2020

We have recently reported that in frog skeletal muscle the plasma membranes, including the transverse tubules, are densely populated by filipin-sterol-complexes (FC), and that in the sarcoplasmic reticulum (SR) the FC are found much less commonly than in the plasma membrane, but that they have a predilection for the junctional SR (terminal cisterna) which in skeletal muscle are very large cisternae that are in close proximity to the plasma membrane. The analogous junctional SR of cardiac muscle shares all anatomical and topographic features with the junctional SR of skeletal muscle, except that in the latter the junctional SR is much larger. Ue have considered the possibility that the proximity of the junctional SR to the plasma membrane, the latter being replete with FC, may be related to the predilection of the FC for junctional SR in skeletal muscle.
The Role of Intracellular Membranes in Protein Processing
Authors: Shields Dennis , Warren Thomas G. , Roth Sara E. , Green Reza F.
Published: June 2020

Most polypeptides destined for secretion are synthesized on polyribosomes bound to the membrane of the endoplasmic reticulum (E.R.), in contrast, cytosolic proteins are made on free ribosomes. When the messenger RNA (mRNA) for a secretory protein is translated in a cell-free protein synthesizing system, the product is usually larger than the mature protein by about 3,000 daltons. Numerous studies have demonstrated that the higher molecular weight of the cell-free translation product can be attributed to an amino terminal extension of about 20-30 amino acids termed the “signal peptide”. This signal peptide is thought to mediate binding of ribosomes bearing the nascent polypeptide chain to the membrane of the endoplasmic reticulum. Upon interaction with the E.R., the polypeptide chain is translocated across the membrane usually resulting in proteolytic removal of the signal peptide and segregation of the “processed” polypeptide into the ER. cisternae. This series of reactions can be followedin vitroby supplementing the cell-free protein synthesizing system with heterologous microsomal membranes which have been stripped of their endogenous ribosomes.
Freeze Fracture Morphology of Some Synthetic and Naturally Occurring Triacylglycerols
Authors: Rigler Mark W.
Published: June 2020

The technique of freeze fracture works well for studying intact lipids since conventional dehydration and resin embedding steps for thin sectioning may extract enormous quantities of lipid. It would be advantageous to the investigator who utilizes freeze fracture as a method to be able to identify lipid droplets in preparations of natural or commercially contrived food stuffs, as well as, tissue preparations. The following questions may arise in such studies: a) what type morphological features are present, if any, b) what effect does saturation vs unsaturation have on morphology, and c) is it possible to predict structure on the basis of natural vs synthetic triacylglycerol (TG)?

Emulsions of oils were prepared by sonicating mixtures of 10% gum arabic (pH 7.10) and the sample oil (2:1 w/w). Sonicates were cryoprotected with 30% glycerol and fractured at -120°C in a Balzers 360M freeze etch unit.
Ultrastructural Observations on Induced Retraction of the Reticulopodial Network of Allogromia SP. (Foraminifera)
Authors: Koury S. T. , Bowser S. S. , McGee-Russell S. M.
Published: June 2020

Allogromia sp. (strain N.F. Lee) provides a convenient model system for studying intracellular transport. We have been examining ultrastructural changes which occur in the reticulopodial network (RN) and cell body (CB) of Allogromia at various stages in the retraction response stimulated by 0.4M MgCl2 solution. As retraction proceeds, microtubules (MT) disassemble and form areas of regularly packed cytoplasm (TP-tigroid patterning) resembling vinca alkaloid induced paracrystals of tubulin. TP is first seen in the RN, and later in the CB. TP consists of dark filamentous material 12.5 nm in width separated by a light spacing of 8 nm when plane of section gives a perfect repeat pattern (arrow-fig. 6). TP may fill the entire profile of a reticulopod and in early stages of retraction is seen in close juxtaposition to MT. In the CB, TP occurs in patches 0.3-2.0 μm in diameter. TP is seen with great frequency in retracting Allogromia, but also, it can be seen occasionally in animals with fully extended RN.
Element Fluxes in Ischemic Mouse Brain Nuclei
Authors: Mehard C. W. , Akers G. D. , Breeze R. , Ignelzi R. J.
Published: June 2020

Cerebral edema resulting from cerebral ischemia is an unsolved problem of modern medicine. Perturbations, such as restricting cerebral blood flow, results in severe disturbances in the distribution of Na, K and other inorganic ions and organic molecules between extracellular and intracellular compartments and correlates with ischemic brain swelling (Ignelzi, 1980; Ignelzi and Wickham, 1980). The technique of x-ray microanalysis (STEM-EDS) has permitted us to èvaluate in vivo compartmental element fluxes which occur prior to and during ischemic insult. We report here the preliminary studies on element shifts from mouse brain cortical nuclei under anoxic-ischemic conditions.

Cerebral cortex tissue from Swiss-Webster mice was rapidly dissected and frozen at zero time “control” (within 15 seconds) and at four minutes of ischemia. Tissue pieces (1 mm3) were placed on small wooden dowels and rapidly frozen by plunging into an isopentane slush cooled by liquid nitrogen.
The Function of Calmodulin in the Regulation of Smooth Muscle Actomyosin
Authors: Harts home D. J. , Persechini A.
Published: June 2020

It is known that the contractile activity of all muscle types is regulated by the intracellular concentration of Ca2+ and further it is accepted that the actomyosin systems in these cells contain regulatory proteins which can sense the level of available Ca2+ and cause the muscle to either contract or relax. In skeletal and cardiac muscle this role is fulfilled by the troponintropomyosin complex. However, in smooth muscle the identity of the regulatory components is the subject of controversy. The most popular theory is based on the phosphorylation of the myosin molecule: in the phosphorylated state the Mg2+ -ATPase activity of myosin is activated by actin, whereas in the dephosphorylated state no activation occurs. The alternative theory, proposed by Ebashi and his colleagues, is that regulation is achieved by a thin filament-based regulatory complex, termed leiotonin.

Calmodulin is involved only with the phosphorylation scheme and it was shown that the myosin light chain kinase is composed of two subunits, an apoenzyme of molecular weight approximately 100,000 daltons and the regulatory protein, calmodulin. The molar stoichiometry is 1.
Cytochemistry and Electron Microscopy: ACYL Hydrolase and Transferase Reactions
Authors: Barrnett Russell J. , Higgins Joan A.
Published: June 2020

The use of enzyme cytochemistry with electron microscopy depends on the compromise solution of combining the rigid requirements of both fields. The ability to make the combination has limiting as well as definitive conditions.

In illustration of some of the above problems, thiol substituted carboxylic acids should be satisfactory substrates for the demonstration of carboxylic acid esterase activities with Pb++ as the capture reagent. However, utilizing thioacetic acid which is hydrolized by acetylcholinesterase, sites of hydrolysis other than those of carboxylic acid esterases (not affected by the usual inhibitors of esterase activity) are revealed. Among these sites are synaptic vesicles of the myoneural junction, and endoplasmic reticulum and mitochondria of a variety of cells. Contrary to expectations, thiobutyric acid was not split by serum cholinesterase but it, as well as longer chain substrates (thiohexanoic and thio-octonoic acids), was also hydrolysed by enzymes in mitochondria and in the endoplasmic reticulum.
Electron Microscopic Radioautography: The Sites of Nuclear RNA Synthesis in Early Embryonic Cells
Authors: Karasaki Shuichi
Published: June 2020

The relationship between RNA synthesis and ultrastructural organization of chromatin fibrils was examined in the interphase nuclei of the sea urchin embryos (Arbacia punctulata). The embryos at various stages of development were treated for 1 or 3 hours in sea water with 50 μC/ml of 3H-5-uridine. The samples were fixed in OSO4 or glutaraldehyde (GTA) and embedded in Epon or glycol methacrylate (GMA). Radioautographs were made by applying a thin film of Ilford L4 emulsion directly from an expandable wire loop to thin sections mounted on grids. Following exposure of 10 to 20 weeks, they were developed in Microdol-X or physical developer.

In the cleavage and early blastula embryos, each interphase nucleus contains diffusely distributed chromatin and shows only very low incorporation of 3H-uridine into RNA (Fig.1). During these periods, many nucleolus-like bodies occur within the nucleus although they are not labeled with the isotope.
Electron Microscopy of Foot-and-Mouth Disease Virus Crystals and Ferritin-Tagged Antibodies
Authors: Breese S. S.
Published: June 2020

The interaction of ferritin-tagged antibodies with crystals of foot-and-mouth disease virus (FMDV) has been examined with a homologous and a heterologous antibody. Methods for crystal formation in primary swine kidney cells have been established on a more reproducible basis.

The FMDV strain used in these experiments, A1, had been stored at -20°C as the sixth bovine kidney cell passage from the original bovine tongue tissue suspension. It was subsequently inoculated into primary swine kidney cultures for two more passages. The preparation used to inoculate cultures for the experiments reported here was therefore designated BK6PK2. Two-tenths ml of this virus passage was inoculated into each drained prescription bottle. After incubation at 37°C for 90 min, 5-10 ml of maintenance medium was added and the bottles returned to the incubator. Five to six hr after infection, the cell sheets were examined for cytopathic effect.
Fine Structure of a Transplantable Avian Lymphoma
Authors: Clawson C. C. , Dent P. B. , Good R. A.
Published: June 2020

Avian lymphoid leukosis is induced by an RNA virus for which the strain RPL-12 has been considered a prototype. This virus was developed from the transplantable lymphoid tumor originally studied by Olson. As part of our studies of the pathogenesis of the RPL-12 induced lymphoid leukosis we have examined another transplantable lymphoma similar to Olson's original tumor. A solid tumor specimen (#3878) was obtained from Dr. B. R. Burmester, USDA Reg. Poultry Res. Lab., East Lansing, Mich. This tumor was the origin of virus strain RPL 16 which produces a lymphoid leukosis thought to be dependent upon the bursa of Fabricius. The solid transplantable tumor is similar in growth and histology to the Olson tumor.
One-Step Release of DNA Rings From Polyoma Virions
Authors: Vasquez C. , Kleinschmidt A. K.
Published: June 2020

A tightly packed regularly coiled DNA ring is assumed to be present inside the polyoma virion. Applying the “one-step” technique of nucleic acid extraction from virions while being adsorbed to a protein monolayer, we studied the configurational changes of the DNA.

Intact polyoma virions were mixed with DFP-trypsin (100μg/ml) and spread onto a subphase of a mixture of urea and sodium perchlorate (6M and 2M, or 3M and 1M respectively), at pH 8.2 and room temperature. After spreading the film, aliquots were transferred to grids at different periods of time, and the DNA stained by acetonic uranyl acetate.

The length distribution of the DNA molecules measured from electron micrographs is shown in Fig. 1. The number of twists present at different times after spreading were also counted. At 12 minutes, with 3M urea and 1M sodium perchlorate in the subphase, the DNA was found to be 85% supertwisted (Fig. 2); 12% was opened to rings, and 3% existed as linear filaments.