bluuebunny/crossref_metadata_2025 huggingface dataset:
Visibility of Partial Dislocations for g·b = ± 2/3, ± 4/3
Authors: Kear B. H. , Oblak J. M.
Published: June 2020

The customary criterion for invisibility of partial dislocations is g·b=0, ± 1/3. However, Silcock and Tunstall (2) have shown that when s > 0 a partial is visible for g⋅b = + 2/3 but not for g·b = -2/3. This is demonstrated in Fig. la,b where partial 1 is visible for g = 200 and invisible for g = . Partial 4 behaves in an opposite manner. This dislocation configuration was found to lie on the plane with the partials also invisible for g = and g = (Fig. 1c,d). Thus the partial dislocations have Burgers vectors parallel to , the zone axis defined by the latter two diffraction vectors. It follows that the Burgers vector for partial 1 is 1/3 and for partial 4, 1/3 . Such dislocations allow the Ll2 γ' precipitate in this nickel-base alloy to be sheared without violation of nearest neighbor order.
Heterogeneous Precipitation at Dislocations
Authors: Eikum A. K.
Published: June 2020

Precipitation phenomena in concentrated aluminum-base silver alloys have been studied with a variety of techniques including electron microscopy. The purpose of the present work was to investigate the dislocation reactions that occur as silver atoms precipitate (or segregate) under a relatively low supersaturation. Specimens (0.1 mm thick) of Al-1 at. % Ag were quenched from ~500°C into an oil bath at room temperature and aged 30 min. at 265°C. The initial configurations available as sites for heterogeneous precipitation will therefore include perfect prismatic dislocation loops, Frank sessile loops and random segments of grown-in dislocations.
A Scanning Electron Microscope from Hitachi
Authors: Onuma Yoshirou , Hujiyasu Tatsuo , Kakinuma Yukio
Published: June 2020

Hitachi, Limited has recently completed the development of a commercial scanning electron microscope, the features of which are discussed herein. Fig. 1 is an external view of the instrument.

Lens System

A three-stage reduction lens system is employed to obtain a short electron beam path. This minimizes the effects of any external electromagnetic or stray electrical fields as well as mechanical vibration or shock. Axial alignment is easily accomplished by transverse adjustment of the electron gun and lens system. Aperture plates with different hole sizes are provided in the condenser lens, deflection coil, and on the principal plane of the objective lens. The apertures are easily removed for cleaning. The electromagnetic stigmator is located outside the objective lens to facilitate removal for cleaning. Resolution of 200Å~250Å is guaranteed.
Recent Results from the 500-KV Virginia High Voltage Electron Microscope
Authors: Lawless Kenneth R. , Geiss Roy H.
Published: June 2020

The installation of the RCA 500-kV electron microscope in the Department of Materials Science at the University of Virginia was completed during the summer of 1968. An overall view of the microscope is shown in Fig. 1. The microscope was designed for operation by a single operator in a manner as similar as possible to that of the conventional 100-kV microscope.

The microscope contains a number of unique features. The high voltage is provided by an insulated core transformer and is fed to the accelerator on top the microscope column by an overhead cable. Voltages from 100 to 500-kV in 10-kV steps are available. The vacuum system consists of a combination of a high speed diffusion pump for initial pumpdown, and three ion pumps for normal operation Of the microscope.
Stacking Faults in Vanadium at 400-KV
Authors: Geiss Roy H. , Lawless Kenneth R.
Published: June 2020

A 500-kV electron microscope manufactured by RCA was recently installed in the Department of Materials Science of the University of Virginia. During the course of evaluation of the instrument, electrochemically thinned foils of recrystallized, high-purity vanadium were studied. The thinning process was carried out combining the window technique with the twin semi-circular cathode arrangement described by Gidley and Davies. The foils produced were completely transparent at 4-500-kV over dimensions at least 2mm on a side. It is estimated that tfye foil thickness exceeded 2µ in thicker regions.
Electron Optical Micro Recording at Tübingen
Authors: Möllenstedt Gottfried , Speldel Rumold , Schief Rudolf , Koops Hans , Holl Peter
Published: June 2020

Some progress in the electron-optical recording of micro structures has been made using the following three principles:

1) A micro structure is recorded by a fine electron probe of constant current magnetically deflected according to the desired pattern.

2) The probe scans the recording plane with constant velocity and line distance while its intensity is controlled by the signal from a vidicon pick-up tube.

3) A stencil is electron-optically demagnified using a wide stationary beam.

The recording mechanisms are

a) Decomposition of a collodion foil.

b) Chemical changes in photoresist materials.

c) Surface contamination by polymerides on carbon, beryllium, silver, and other substrates.
Foil Thickness Determination from Single Crystal Diffraction Patterns
Authors: Bell W. L. , Thomas G.
Published: June 2020

Foil thickness measurements are necessary for determining crystal volumes, which in turn are needed to calculate defect densities for dislocations or point defect clusters or for determining interparticle spacings. The most generally applied technique for obtaining the foil thickness is the trace method wherein the trace of a known plane (slip trace, stacking fault, grain boundary, etc.) must be determined, its projected width on a micrograph measured, the precise crystal orientation calculated from a diffraction pattern and the thickness calculated from simple trigonometric relationships. If no traces are obtainable on an image, an alternate method uses extinction contours: a perfect wedge-shaped crystal is set at the Bragg angle, and the number of white fringes from the edge of the foil in a bright-field micrograph (or dark fringes in a dark-field micrograph) counted and multiplied by the extinction distance (which must be accurately known) for the particular reflection involved.
Characteristic Geometry and Diffraction Contrast of Dispersed ThO2 Crystals
Authors: Horylev R. J. , Murr L. E.
Published: June 2020

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.
Point Cathode Electron Sources
Authors: Wiesner J. C. , Everhart T. E.
Published: June 2020

The use of pointed cathodes in electron guns provides certain advantages over thermionic hair-pin cathodes. This is true both for the heated point operating in Schottky emission and for the cold cathode field emitter. In particular, much higher beam current density for a given solid angle of convergence or divergence is obtainable as well as much smaller source sizes. A recent simplified analysis has given expected values of current densities, total useable current, source size, and aberration characteristics of a gun using a pointed cathode.
Bacteriophage-Like Entities Associated with a Leptospire
Authors: Ritchie A. E. , Ellinghausen H. C.
Published: June 2020

We have fortuitously observed phage-like structures in cultures of an unclassified leptospire. This report presents their morphology and evidence that they probably originate within the leptospire. We are unaware of any previous report of leptospiral phages although Hoogenraad et al. (J. Gen. Virol. 1:575-576, 1967) have observed a small phage associated with an anaerobic spirochete in sheep rumen contents.
Development of Microfibers in the Peritrophic Membrane of a Mosquito Larva
Authors: Richards A. Glenn , Richards Patricia Ann
Published: June 2020

The peritrophic membrane (PM) of insects (and some other invertebrates) is a secreted sheet that lines the midgut, encases the food in the manner of a sausage casing, and hence prevents the food from making direct contact with the midgut epithelium. Chemically the PM is composed of chitin and protein with at least a portion of the chitin organized into microfibers in some species at some stages of development. In some groups of insects the PM is produced by the entire midgut epithelium but in some groups it is secreted at a particular area at the anterior end of the midgut and extruded posteriorly. The latter situation was chosen as a favorable one to investigate the origin of chitinous microfibers and possible tempiating versus extracellular aggregating for their development.
Demonstration of Peroxidase Activity in Microbodies with a Modified Benzidine Procedure
Authors: Goldfischer Sidney , Essner Edward
Published: June 2020

Microbodies of liver and kidney can be visualized by light and electron microscopy (fig.5) with an alkaline modification of the Graham and Karnovsky peroxidase method, based on oxidation of 3—3' diaminobenzidine (DAB). The reaction does not occur in the presence of 3-amino-1, 2, 4 triazole, an inhibitor of catalase, suggesting that staining is due to peroxidatic activity of catalase.
Microtubules in Specialized Cardiac Cells
Authors: Baziuk M.D. , Challice C.E.
Published: June 2020

The atrioventricular funnel in the toad heart (Bufo marinus) has been examined with a view to determining the structure of those cells which conduct the contractile impulse markedly slower than myocardial cells found elsewhere in the heart. A general picture of the characteristic morphology of the cells of the various regions is becoming established and will be described elsewhere. However, one observation which is of some interest is that of microtubules in some of the cells which contain clear myofibrillar development.
The Transfer of Carbon Particles Through the Lymph Node-Venous Communication
Authors: Dunn Robert F. , Burtz M.V. , Ward Paul H.
Published: June 2020

In an effort to demonstrate the passage of particulate matter through the lymph node-venous communication, colloidal carbon particles (shellac-free India ink) were injected through the afferent lymphatic channels into the cervical lymph node of dogs. The lymph nodes were removed immediately after injection, and at 15, 30, 45 and 60 minute intervals after injection of the tracer. The lymph nodes were then quartered, and immersed in 2.5% glutaraldehyde fixative. Subsequently, the tissue was processed for embedding in Epon 812 by standard techniques after post-fixation with osmium tetroxide.
A Resorcinol-Formaldehyde Resin as an Embedding Material for Electron Microscopy of Membranes
Authors: Robertson J. G. , Parsons D. F.
Published: June 2020

The extraction of lipids from tissues during fixation and embedding for electron microscopy is widely recognized as a source of possible artifact, especially at the membrane level of cell organization. Lipid extraction is also a major disadvantage in electron microscope autoradiography of radioactive lipids, as in studies of the uptake of radioactive fatty acids by intestinal slices. Retention of lipids by fixation with osmium tetroxide is generally limited to glycolipids, phospholipids and highly unsaturated neutral lipids. Saturated neutral lipids and sterols tend to be easily extracted by organic dehydrating reagents prior to embedding. Retention of the more saturated lipids in embedded tissue might be achieved by developing new cross-linking reagents, by the use of highly water soluble embedding materials or by working at very low temperatures.
Bimolecular and Monomolecular Lipid Films: Selected Area Electron Diffraction
Authors: Glaeser Robert M. , Deamer David W.
Published: June 2020

In the investigation of the molecular organization of cell membranes it is often supposed that lipid molecules are arranged in a bimolecular film. X-ray diffraction data obtained in a direction perpendicular to the plane of suitably layered membrane systems have generally been interpreted in accord with such a model of the membrane structure. The present studies were begun in order to determine whether selected area electron diffraction would provide a tool of sufficient sensitivity to permit investigation of the degree of intermolecular order within lipid films. The ultimate objective would then be to apply the method to single fragments of cell membrane material in order to obtain data complementary to the transverse data obtainable by x-ray diffraction.
Stereography of Freeze Etched Replicas
Authors: McAlear James H. , Shatos Marie , Demsey Anthony , Donovan Anita
Published: June 2020

The frequent analogy made between the appearance of freeze etch replicas and the lunar landscape is appropriate in the sense that both are best viewed as if they were opaque irregular surfaces illuminated from behind and to the side of the observer. Replicas are actually illuminated by a transmitted electron beam and the illusion of a lighted opaque surface arises from the heavy metal shadow which appears light when viewed as a negative.

Stereography adds to the perspective provided by shadowing and reveals remarkable differences in elevation which would be unnoticed in single micrographs. This technique now seems essential to the proper interpretation of freeze etched replicas. It further aids in the detection of artifacts due to the electron density of the replica itself.
Information Content of Electron Microscope Images: Color and Depth Information as Vehicles for Subjective Information Transfer
Authors: Hayes T. L. , Glaeser R. M. , Pawley J. B.
Published: June 2020

It may be valuable to add subjective modes of information transfer to the usual objective or analytic modes. Subjective modes are not neat and vary from person to person but they can become increasingly important as the systems under study become more complex. By limiting ourselves to the digital information (words, numbers) that is the same for all people we would be neglecting a significant part of each individual. In order to utilize as much as possible of the entire person of the observer, we wish to build up an image that corresponds to experienced vision. Not all images contain the kinds of information necessary for this correspondence and certainly not all information that is received via the eye can-be compared to experienced vision. It is only when an image contains the parameters of experienced vision that the confidence associated with terms like “direct visualization” is justified. High resolution alone does not guarantee a useful image. We must also consider the kinds and levels of information that is transmitted to the observer.
Albumins as Embedding Media for Electron Microscopy
Authors: Farrant J. L. , McLean J. D.
Published: June 2020

For electron microscope techniques such as ferritin-labeled antibody staining it would be advantageous to have available a simple means of thin sectioning biological material without subjecting it to lipid solvents, impregnation with plastic monomers and their subsequent polymerization. With this aim in view we have re-examined the use of protein as an embedding medium. Gelatin which has been used in the past is not very satisfactory both because of its fibrous nature and the high temperature necessary to keep its solutions fluid. We have found that globular proteins such as the serum and egg albumins can be cross-linked so as to yield blocks which are suitable for ultrathin sectioning.
An Early American Electron Microscope
Authors: Cohen Arthur L. , Steever R. G. E.
Published: June 2020

An interest in the historical aspects of electron microscopy has been shown by several recent publications on the subject. As early as 1936 Dr. Paul Anderson and the late Mr. Kenneth Fitzsimmons were experimenting with an electron microscope in the Physics Department of Washington State University (then Washington State College). The instrument (see illustrations) was constructed somewhat on the designs of Knoll and Ruska. The electron source was a heated filament, and accelerating voltage was 30 KV. The microscope has three electromagnetic lenses; condenser, objective, and projector. External rectangular Helmholz coils (see illustration) corrected for the earth's magnetic field and permitted beam shift. The column is brass. The camera magazine held six lantern slide plates which could be successively exposed without breaking vacuum. Particularly interesting is the attempt to measure beam current at the fluorescent screen in order to determine photographic exposure.
Electron Holography and the Correction of Spherical Aberration
Authors: Crewe A. V. , Saxon J.
Published: June 2020

Division of wavefront electron holograms have been recorded using a field emission source and electrostatic biprism to get an off axis reference beam. A schematic diagram of the apparatus used is shown in Fig. 1. The electron beam is focused to a point above the specimen and biprism fiber by a specially designed electron gun. With positive potential applied to the fiber the Fresnel diffraction pattern of the specimen is superimposed on the interference pattern of the two effective sources forming the hologram. Two standard magnetic projector lenses are used to magnify the hologram which is recorded outside the vacuum system directly on film in contact with a phosphor-coated fiber optic faceplate. A He-Ne laser is used for the reconstruction as shown in Fig. 2. Following Meier's analysis it is found that when a parallel beam is used to reconstruct the wavefront, the real image will be in focus a distance

in front of the hologram where m is the total magnification of the hologram and μ is the ratio of the illuminating to recording wavelengths.
Scanning Electron Microscopy of Hot and Electron Emitting Specimens
Authors: Ahmed H.
Published: June 2020

The conventional, scintilator-photomultiplier type of electron collection system cannot be used satisfactorily to examine hot orelectron emitting specimens. The main difficulties are: a) light from the specimen or heater can reach the pm tube and produce a spurious output, b) heat from the specimen can damage the plastic scintillator used in the collector assembly, and c) electronemission from the specimen must be kept substantially below the beam current of about 10-11 A.
New Design for a Differentially Pumped Hydration Chamber for a Siemens IA
Authors: Moretz R. C. , Hausner G. G. , Parsons D. F.
Published: June 2020

Electron microscopy and diffraction of biological materials in the hydrated state requires the construction of a chamber in which the water vapor pressure can be maintained at saturation for a given specimen temperature, while minimally affecting the normal vacuum of the remainder of the microscope column. Initial studies with chambers closed by thin membrane windows showed that at the film thicknesses required for electron diffraction at 100 KV the window failure rate was too high to give a reliable system. A single stage, differentially pumped specimen hydration chamber was constructed, consisting of two apertures (70-100μ), which eliminated the necessity of thin membrane windows. This system was used to obtain electron diffraction and electron microscopy of water droplets and thin water films. However, a period of dehydration occurred during initial pumping of the microscope column. Although rehydration occurred within five minutes, biological materials were irreversibly damaged. Another limitation of this system was that the specimen grid was clamped between the apertures, thus limiting the yield of view to the aperture opening.
Electron Microscopy in Radiation Damage: Current Trends
Authors: Chadderton Lewis T.
Published: June 2020

1970/71 has seen widespread use of the electron microscope in studies of void formation in materials potentially useful as fast breeder nuclear reactor fuel cladding. Whereas the gas bubble was ten years ago the major object of study now it is the void, supposed to contain no gas at all. Yet traces of rare gas, produced by neutron transmutation, evidently play a key part in void nucleation. Experimental simulations of the intense vacancy concentrations produced by high neutron fluences (<1022 ), using charged ions, show that samples of alloys preinjected with helium ions in trace quantities have immensely higher void concentrations than otherwise. The influences of alloy temperature, dispersion hardening, flux etc. are being exhaustively studied in both Europe and the USA. No acceptable growth/fluence relationship is yet available, however, partly because of the large number of parameters involved, and, in spite of the existence of satisfactory diffraction and absorption contrast theories for voids, partly because of the errors associated in measuring volume changes. Voids in fcc material are essentially octahedral, though multiple extensions and truncations can occur. Much less work has been reported on bcc material. For molybdenum the observation of a remarkably regular array of voids is described (see fig. 1). This suggests that one source of voids might be charged gas bubbles of minute size which by mutual repulsion form a crystallographic superlattice. The nucleation mechanism is the critical process to be studied here.
Displacement Rate Effects in Heavy Ion Bombardment of Stainless Steel
Authors: Laidler J. J.
Published: June 2020

The effectiveness of heavy ion bombardment as a technique for the simulation of high fluence fast neutron irradiation effects depends on the significance of the widely differing displacement rates prevailing with the two types of bombarding particles. Previous experiments have established the qualitative equivalence of microstructures in neutron-irradiated and ion-bombarded stainless steel, but most current theories of defect nucleation and growth in irradiated metals are explicitly rate-dependent. Hence, the present work was performed to determine in a quantitative manner any effects ascribable to a difference in atom displacement rate.

Type 316 stainless steel specimens were bombarded at 425°C with 5 MeV Ni++ ions, using the Ion Physics Corporation tandem Van de Graaff accelerator.
The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels
Authors: Cluthe C. E. , Cocks G. G.
Published: June 2020

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.

The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.
A Technique for Displaying Theoretical Transmission Electron Microscope Images
Authors: Fillingham P. J. , Leamy H. J. , Maher D. M.
Published: June 2020

Since the earliest work on computer simulation of electron microscope images, it has been realized that a technique for producing a high quality image would facilitate analysis of the information content of theoretical intensity data. In particular, this would be an aid in image analysis and testing approximations used in electron diffraction theory.

A technique has been developed for producing a semiglossy print from data on magnetic tape using a commercial facsimile device. In the present application only the receiver of the facsimile device is used to produce a simulated electron micrograph. An array of intensities corresponding to the light or dark field image of a defect is computed. A simple two-dimensional interpolation scheme gives an enlarged array (on magnetic tape) which is then converted to analog form and transmitted to the receiver of the facsimile device.
Microdensitometers and Data Processing for Electron Microscopy
Authors: Bender Robert , Rowe James E.
Published: June 2020

Most of the information obtainable from transmission electron microscopy is lost in the course of normal ‘print and look’ handling -or at least made difficult to retrieve. Not only is there an actual degradation of information, but operations such as the measurement of areas etc. are then carried out manually at great cost in time, and loss of accuracy. One of the main causes of loss of accuracy is the understandable reluctance of competent persons to do a great deal of highly repetitive work. Unfortunately in order to get good error bounds in most cases of interest multiple measurements must be made. Data processing technology is now sufficiently developed to make automatic picture processing an attractive and realizable goal. While this is not specifically a paper on image processing, some simple and possibly generally useful algorithms will be presented.

The first step in any data processing schema is data acquisition. In the case of transmission electron microscopy several methods are available, some with advantages in unique situations.
On the Rate Controlling Mechanism Operative During Superplastic Flow
Authors: Gecklini E. , Anderson L. J. , Barrett C. R.
Published: June 2020

This investigation is concerned with a determination of the rate controlling mechanisms operative during superplastic flow. The experimental technique involves the deformation of Pb-Sn eutectic samples in a scanning electron microscope. Surface observations of grain shape changes and grain boundary shearing are used to assess the importance of the various deformation mechanisms. As described below, the experimental observations are consistent with a model of grain boundary sliding in association with localized deformation near grain boundaries to maintain coherency.

Experiments are carried out using a specially designed tensile stage in an AMR 900 microscope. The gage section of the tensile sample is 3 mm long, 2 mm wide and 0.5 mm thick. The grain size range investigated is 2 - 5μ and deformation is carried out at room temperature. The tensile stage is designed such that the ends of the sample are translated in opposite directions.
Electron Metallography of Spinodally Decomposed (Cu-Mn)3Al Alloys
Authors: Bouchard M. , Thomas G.
Published: June 2020

Alloys along the composition tie line Cu3Al-Cu2MnAl were found to rapidly order during quenching from 850°C. First the disordered bcc structure orders to the B2 structure and at lower temperatures it further orders to a structure closely related to the DO3 superstructure of an A3B alloy and to the L21 superstructure of an A2BC alloy. Below the critical temperatures for B2 ordering, Cu atoms occupy sublattices I and III and the sublattices II and IV are occupied by a random mixture of the remaining atoms. At lower temperatures, the sublattice II is occupied by Al atoms and the sublattice IV is occupied by a mixture of Cu and Mn atoms. The composition of the sublattice IV depends on the atomic composition of the alloy; it is 100% Cu in Cu3Al and 100% Mn in Cu2MnAl. The lattice parameters of these two ordered phases are 5.833A and 5.95A respectively.
Studies of Fracture in the High Voltage Electron Microscope
Authors: Bauer R. , Geiss R. H. , Lyles R. L. , Wilsdorf H. G. F.
Published: June 2020

Experimental techniques for the study of in-situ crack propagation and fracture have been developed for use in the 500 kV electron microscope at the University of Virginia. The investigations are concerned with the problems of defining the mechanism of crack propagation on a microstructural scale and the relationship of thin film vs bulk behavior. By restricting ourselves to ductile fracture, the features to be seen if bulk behavior dominates are necking, shear, and hole formation in front of the propagating cracks.

In-situ straining of the specimens was accomplished using a hydraulically loaded tensile stage designed and built for use with one of the radial access ports provided in the microscope.

Two types of specimens have been investigated: (i) single crystal ribbons of silver grown from solution using an ionic reduction technique and (ii) annealed polycrystalline sheet stainless steel. The former served primarily for studying the fundamental aspects of ductile fracture while with the latter the influence of grains and grain boundaries on fracture was investigated.
Disappearance Voltage Determinations Using a Convergent Beam
Authors: Bell W. L.
Published: June 2020

Disappearance voltages for second order reflections can be determined experimentally in a variety of ways. The more subjective methods, such as Kikuchi line disappearance and bend contour imaging, involve comparing a series of diffraction patterns or micrographs taken at intervals throughout the disappearance range and selecting that voltage which gives the strongest disappearance effect. The estimated accuracies of these methods are both to within 10 kV, or about 2-4%, of the true disappearance voltage, which is quite sufficient for using these voltages in further calculations. However, it is the necessity of determining this information by comparisons of exposed plates rather than while operating the microscope that detracts from the immediate usefulness of these methods if there is reason to perform experiments at an unknown disappearance voltage.

The convergent beam technique for determining the disappearance voltage has been found to be a highly objective method when it is applicable, i.e. when reasonable crystal perfection exists and an area of uniform thickness can be found. The criterion for determining this voltage is that the central maximum disappear from the rocking curve for the second order spot.
Thin Pyrolytic Graphite Films for Electron Microscope Substrates
Authors: Riddle George H. N. , Siegel Benjamin M.
Published: June 2020

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.

The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.
Nerve Cells and Fibers in the Optic Lobe Cortex of Octopus
Authors: Case Norman M. , Gray E. G.
Published: June 2020

Montages of electron micrographs from the outer portion of the cortex of the optic lobe of Octopus are shown. Sheets of dark cytoplasm which originate from glial cells in the outer granular layer form a basement layer separating the outer granular layer from the deeper plexiform layer.

Optic nerve fibers from the retina entering the optic lobe around its periphery must pass between the amacrine cells composing the bulk of the outer granular layer. Here they are the darker of the two fiber types that can be identified. Passing through the basement layer they expand into large “carrot” shaped terminal endings easily identified by their dark appearance caused by the extremely high content of synaptic vesicles they contain.

Fibers in the neuropil press tightly against and indent the “carrots” and occasionally make synaptic contact with them. Some fibers penetrate deeply into the “carrots” where they branch and terminate in grape-like clusters that show many synaptic contacts with the enveloping bag.
Ultrastructure of the Actinomycele Ceodermatophilus Obscurus
Authors: da Fonseca A. Freitas , Edwards M. R.
Published: June 2020

Geodermatophilus, a new generic taxon of the Dermatophylaceae (Actinomycetales), was first described by Luedemann and shown to display close similarities to Dermatophilus congolensis, previously described in our laboratory.

Although Geodermatophilus has been studied by electron microscopy, the present investigation was undertaken to clarify further some ultrastructural aspects of this organism in relation to those of D. congolensis. Standard procedures for chemical fixation, as well as recently developed methods for physical fixation, were chosen but the present report is concerned only with results of thin sections. Cells from 16 hr. to 15-day-old cultures, in the medium described by Luedemann, were fixed with cacodylate buffered glutaraldehyde followed by osmium tetroxide in veronal acetate buffer, or according to Kellenberger et al. Dehydration was in ethanol and embedding in Epon 812.
Electron Microscopy of Mycoplasma Pneumoniae
Authors: Boatman E. S. , Kenny G. E.
Published: June 2020

Information concerning the morphology and replication of organism of the family Mycoplasmataceae remains, despite over 70 years of study, highly controversial. Due to their small size observations by light microscopy have not been rewarding. Furthermore, not only are these organisms extremely pleomorphic but their morphology also changes according to growth phase. This study deals with the morphological aspects of M. pneumoniae strain 3546 in relation to growth, interaction with HeLa cells and possible mechanisms of replication.

The organisms were grown aerobically at 37°C in a soy peptone yeast dialysate medium supplemented with 12% gamma-globulin free horse serum. The medium was buffered at pH 7.3 with TES [N-tris (hyroxymethyl) methyl-2-aminoethane sulfonic acid] at 10mM concentration. The inoculum, an actively growing culture, was filtered through a 0.5 μm polycarbonate “nuclepore” filter to prevent transfer of all but the smallest aggregates. Growth was assessed at specific periods by colony counts and 800 ml samples of organisms were fixed in situ with 2.5% glutaraldehyde for 3 hrs. at 4°C. Washed cells for sectioning were post-fixed in 0.8% OSO4 in veronal-acetate buffer pH 6.1 for 1 hr. at 21°C. HeLa cells were infected with a filtered inoculum of M. pneumoniae and incubated for 9 days in Leighton tubes with coverslips. The cells were then removed and processed for electron microscopy.
An Electronmicroscopic Study of Collateral Nerve Sprouts
Authors: Jew J. , Williams T. H.
Published: June 2020

One of the major limitations of classical regeneration is that an axon may have to grow a long way before it can re-establish contact with the denervated cells. Fortunately, however, an alternative and more rapid mechanism exists to secure functional recovery. In this process - collateral nerve sprouting - side branches grow out from surviving axons closest to the denervated elements.

Collateral nerve sprouting was recognized by Exner before the turn of the century, though at the time his concept went unnoticed. It was shown that collateral sprouts could restore apparently normal function to skeletal muscle. More recent studies have indicated that collateral sprouting is a general property of peripheral nerves both motor and sensory, somatic and autonomic; but its occurrence in the central nervous system is controversial Structural study of collateral nerve sprouts requires the observation of processes having morphological characteristics beyond the resolution capability of the light microscope. In the absence of information about collateral sprouting at the electronmicroscopic level, and because of its clinical relevance, we set ourselves the task of studying the natural history of this process. The present work will serve as a basis for quantitative studies, including those aimed at controlling the rate and extent of collateral nerve sprouting.
Spherical Arrangement of Osmiophilic Cylindrical Bodies in Trophozoites of Entamoeba histolytica
Authors: Feria-Velasco Alfredo , Treviño Norberto
Published: June 2020

A special arrangement of electrondense cylindrical bodies has been observed in the cytoplasm of trophozoites of Entamoeba histolytica. In a previous report we communicated its presence in trophozoites of E. histolytica cultivated in monoxenic medium. We called this structure “centriole-like body”, which seems to be inadequate in base of the present work. In the progress of this study and examining large amounts of trophozoites cultivated in mixed, monoxenic and axenic culture media, we have observed the spherical structure of cylindrical bodies in the cytoplasm of the trophozoites, regardless the nutrient elements present in the medium. In order to see the detailed structure of the components of this organelle, very thin sections, lightly stained with lead citrate of osmium-fixed material were examined. Some sections were observed unstained and other trophozoites were fixed in glutaraldehyde and incubated in Gomori's medium for acid phosphatase. Electrondense cylindrical units scattered throughout the cytoplasm were seen in all trophozoites examined.
The Effect of Sodium Hydroxide Swelling on Fibrillar Size in Cotton Cellulose
Authors: Hebert J. J. , Hensarling T. P. , Jacks T. J. , Berni R. J.
Published: June 2020

It is known that the cellulose layers in cotton fibers are made up of filament-like units termed fibrils. With the advent of electron microscopical techniques, an extensive effort has been put forth to arrive at a size for these units. The currently accepted value for the diameter of these elementary fibrils is approximately 35 A. U.

In this report an indirect staining technique for electron microscopy has been employed to study the effect of mercerizing strength sodium hydroxide on the size of the elementary fibrils in cotton fibers. The method involves the addition of an unsaturated carbon-carbon double bond to the cellulose within the fibril and further reacting the double bond with osmium tetroxide. The compound used in this investigation was acrylic acid which not only has the osmium reactive bond but, because of its short molecular length, allows the osmium to situate itself at a close proximity to the structure under study.
The Role of the Internal Coating in the Ultrastructural Architecture of Pinocytic Vesicles and its Significance in Vesicular Transport
Authors: Shirahama T. , Cohen A. S. , Rodgers O. G.
Published: June 2020

Forty-micron nonfrozen sections of myocardium from several healthy young adult New Zealand white rabbits, without pretreatment or 10-15 minutes after an intravenous ferritin injection (100 mg ferritin/100 gm. body weight), were double fixed with 2% formaldehyde - 2.5% glutaraldehyde in 0.1M cacodylate buffer and 2% OSO4 in 0.1M cacodylate buffer in the presence of 1000, 100, 50 or 20 ppm ruthenium red (RR), and embedded in Epon. Thin sections of small blood vessels including capillaries, unstained or stained with uranyl acetate and/or lead citrate, were photographed at initial magnifications of 40,000 or 80,000. The results were analysed to delineate the ultrastructural relation of mucopolysaccharides (MPS) in the architecture of pinocytic vesicles and the MPS role in pinocytosis.
Comparative Examination Between the Chemical and Physical Methods to the Demonstration of the Ionic Localization in the Tissues. I. In the Case of Potassium Antimonate Method
Authors: Mizuhira V. , Shiina S. , Miake K. , Ishida M. , Nakamura H. , Yotsumoto H. , Namao T.
Published: June 2020

The results involved in the histochemical technique for the detection of sodium(Na) ion have been analysed. Nonspecific precipitation occurs when potassium(K) antimonate reacts with the ethanol used for dehydration, and also may occur when the pH is below 6.8 during fixation. Since calcium(Ca) and magnesium(Mg) ions can form precipitates with antimonate(Sb) there is a possibility of interference by Ca and Mg ions in tissues. There nonspecific reactions must not be confused with the specific histochemical reaction. The K-phosphate and collidine buffer used to control the pH seems to inhibit the precipitation reaction of K-antimonate with Na ion. The reduced formation of precipitate with K in preserve of these buffers might be caused by an altered ionic balance between the dissociated antimonate and other correlating ions, such as K, H( pH below 6.8 ), or collidine. The non-buffered fixative, however, seems to good results at the electron microscopic observation. On the other hand, Legato et al reported on the Ca-ion localization in the cardiac muscle using the same method for the Na-detection.
Inclusions of the Tegument and Subtegument in the Developmental Stages of the Blood Fluke, Schistosoma Mansoni
Authors: Shannon W. Allen
Published: June 2020

Inclusions observed are designated as types I1 through I6(Figs. 1, 2, 3, and 4). Type I1 (Figs. 2 and 3) is an elliptical structure, 1000 to 2000 Å in length and 200 to 250 Å in width, which contains homogeneous, electron-dense material and is bounded by a trilaminate membrane. The I1 inclusions are few in number and are observed in the teguments of primarily the swimming cercariae and schistosomula. None are observed in the sporocysts. Type I2 (Figs. 1 and 3) comprises trilaminate membrane-bound, spherical inclusions each measuring 1000 to 2000 Å in diameter and exhibiting a central, dense core usually connected to the outer membrane by thin strands. The I2 inclusions are found in all stages except the sporocysts. They often appear to have an intimate relationship to invaginations of the superficial plasmalemma which are observed in close proximity to prominent invaginations of the tegument. The I3 type inclusion (Figs. 1, 2, and 4) is a trilaminate membrane-bound, multilaminated, spherical structure measuring 1000 to 2000 Å in diameter and exhibiting a dense core.
Transmission Electron Microscopy of Protein Macromolecules
Authors: Slayter Henry S.
Published: June 2020

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.
A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits
Authors: Nisbet John H. , Slayter Henry S.
Published: June 2020

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.

At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.
Surface Structure in Microtomed Sections Caused by Glass and Diamond Knives
Authors: Black J. Temple , Boldosser William G.
Published: June 2020

Ultramicrotomy produces plastic deformation in the surfaces of microtomed TEM specimens which can not generally be observed unless special preparations are made. In this study, a typical biological composite of tissue (infundibular thoracic attachment) infiltrated in the normal manner with an embedding epoxy resin (Epon 812 in a 60/40 mixture) was microtomed with glass and diamond knives, both with 45 degree body angle. Sectioning was done in Portor Blum Mt-2 and Mt-1 microtomes. Sections were collected on formvar coated grids so that both the top side and the bottom side of the sections could be examined. Sections were then placed in a vacuum evaporator and self-shadowed with carbon. Some were chromium shadowed at a 30 degree angle. The sections were then examined in a Phillips 300 TEM at 60kv.

Carbon coating (C) or carbon coating with chrom shadowing (C-Ch) makes in effect, single stage replicas of the surfaces of the sections and thus allows the damage in the surfaces to be observable in the TEM. Figure 1 (see key to figures) shows the bottom side of a diamond knife section, carbon self-shadowed and chrom shadowed perpendicular to the cutting direction. Very fine knife marks and surface damage can be observed.
Plastic Deformation in Microtomed Sections
Authors: Black J. Temple
Published: June 2020

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.