bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the Chromium-Depleted Zone in Sensitized Austenitic Stainless Steel
Authors: Burke M. G. , Butler E. P.
Published: June 2020

To explain the dramatic loss in corrosion resistance of Type 30U stainless steel following heat treatments in the temperature ranges 500-850°C, it has been proposed that the intergranular precipitation of chromium-rich carbides (M2 3 C6) should be accompanied by a local depletion of chromium in the austenite. These depleted zones with chromium contents less than ∼ 12 wt.% may be susceptible to preferential intergranular attack. Grain boundary precipitation of (Cr,Fe) 23 C6 during ageing at ∼ 900°C, however, is not observed to modify the corrosion behavior of the steel, thus implying a dependence of depletion on ageing temperature. With the development of STEM quantitative microanalytical techniques, it is now possible to obtain direct evidence of this depletion. Previous STEM microchemical studies (2,3) appear to have overlooked several significant features of such composition profiles. In this investigation, the existence of asymmetric solute profiles and the dependence of chromium depletion on the ageing parameters as well as local crystallography are reported.
Microanalysis of Prior Austenite Grain Boundaries in Temper Embrittled CR-MO-V Turbine Rotor Steel by Stem-Eds
Authors: Wittig J.
Published: June 2020

The problem of temper embrittlement in rotor steels has received a great deal of attention in recent years. It has been demonstrated that impurity elements such as phosphorous, tin, arsenic, and antimony will segregate at grain boundaries in bainitic steel when the material is subjected to the temperature range of 350°C to 550°C for an extended period of time, thus embrittling the steel. These segregation and embrittlement phenomena are accelerated when these elements are present with others such as silicon, manganese, and nickel. Until recently, the segregation has been analyzed primarily by Auger Electron Spectroscopy (AES) of fractured samples. The fracture path must be intergranular for AES to study the grain boundaries, which is a major limitation. The purpose of this study is to demonstrate the applicability of Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive Spectroscopy (EDS) to the investigation of segregation in rotor steels.
Examination by Electron Microscopy of Osmium Catalysts Supported on Thin Aluminium-Oxide Films
Authors: Tesche B. , Zeitler E. , Delgado E. A. , Knözinger H.
Published: June 2020

It is easy to obtain resolutions of atomic dimensions with current conventional transmission electron microscopes. Hence, in principle, the examination of small metal particles or metal atom ensembles (≤1 nra) in supported catalysts is not limited by the instrumental resolution. However, usually the metal is located on dispersed high-area supports such as silica or alumina and the characterization by electron microscopy of these systems down to the atomic dimension is not directly possible, since the contrast in the micrographs is an unknown combination of phase and amplitude contrast. This uncertainty can result in incorrect determinations of particle size, shape and distribution.
Microdiffraction Patterns of Small Metallic Particles, I Experi Mental Results
Authors: Schabes-Retchkiman P. , Gómez A. , José-Yacamán M. , Ocaña T.
Published: June 2020

Small metallic particles have of ten a crystallographic structure which is different from that of the bulk material. This change of structure contains a great deal of information about the physical processes of nucleation and growth of the particles and also has important consequences in their cataly tic behavior.
Specification of Damage Criteria in Electron Microscopy of Polyethylene Film and Crystals
Authors: Krause S. J.
Published: June 2020

Background. The major problem in electron microscopy of polymers is sample beam damage. Thus, there is a need to clearly specify the criteria for an “end point” of electron dosage, beyond which the sample may be damaged to an extent that artifacts are observed. Definitions of an “end point” dosage vary in the literature with respect to the method of measurement, the instrumental conditions, and the particular point along the decay curve which is chosen as an “end point” dosage. For a clearly defined set of criteria the method of measurement must first be specified and may include loss of diffraction contrast, loss of diffracted spot intensity, mass loss, or bonding changes detected by energy loss spectroscopy. Next, the results must be normalized to a standard accelerating voltage and sample temperature. Finally, the point along the decay curve for “end point” dosage should be stated. Points used in the literature include “first detectable change”, 10% decay, 50%decay, 1/exp decay, 90% decay, and “no further change”. We wish to report here other factors of observation technique, sample morphology, and microscopy preparation technique which must also be considered and should be reported in the criteria which specify an “end point” dosage for beam sensitive materials.
Measurement of Degree of Order in Ordered Alloys by Convergent Beam Electron Diffraction Patterns
Authors: Braski D. N. , Bentley J. , Cable J. W.
Published: June 2020

Long-range-ordered (LRO) alloys, with (Fe, Ni)3V compositions, are being developed at this laboratory for possible use in fusion reactors and other elevated-temperature applications. It would be advantageous to monitor the long-range-order parameter (S) in small samples of these alloys after irradiation, heat treatment, welding, etc. A convenient method which uses convergent beam electron diffraction (CBED) for measuring S has been developed. The technique combines the ability of CBED to detect relatively small changes in lattice parameter (a0) with the fact that the lattice dimensions of an alloy usually change with degree of order. A small change in a0 causes shifts of the holz lines which appear in the central disk of a CBED pattern. In addition, small changes in the accelerating voltage (E) will similarly change holz line positions and are related to changes in a0 by:2 Δa0/a0 = ΔE/2E. The instrumentation used was a Philips EM400T electron microscope equipped with a field emission gun and a continuous accelerating voltage control. This latter device permits the operator to make small, precise changes in E and enables one to measure a0 and S without actually recording the CBED patterns. However, the technique does require the use of calibration standards for which a0 and S are known.
CBED Shadow Images and Cs:Aberration Measurement
Authors: Carpenter R. W. , Chan I.Y.T. , Cowley J. M.
Published: June 2020

Wide-angle convergent beam shadow images(CBSI) exhibit several characteristic distortions resulting from spherical aberration. The most prominent is a circle of infinite magnification resulting from rays having equal values of a forming a cross-over on the optic axis at some distance before reaching the paraxial focal point. This distortion is called the tangential circle of infinite magnification; it can be used to align and stigmate a STEM and to determine Cs for the probe forming lens. A second distortion, the radial circle of infinite magnification, results from a cross-over on the lens caustic surface of rays with differing values of ∝a, also before the paraxial focal point of the lens.
Imaging Mass Spectrometry
Authors: Patkin Adam J. , Morrison George H.
Published: June 2020

In the last few years a number of imaging analytical instrumental techniques have been developed: TEM, SEM, STEM, EM, SAM, RBS, ISS, PIXE, and SIMS. While all of these techniques can produce images describing sample morphology, some also produce chemical and elemental images. A few can produce images containing three-dimensional topographic information (e.g. SEM), or are capable of in-depth sample compositional analysis (SIMS, RBS, PIXE, and AES with ion sputtering). When a series of such two-dimensional images can be acquired as a function of depth, the potential exists to generate three-dimensional reconstructions of morphology and composition. Images produced by some of these techniques, the electron microscopies in particular, have been subjected to computer processing to extract meaningful information.
Deformation Stages and Video Installation for a Philips EM400T
Authors: Horton J. A.
Published: June 2020

A series of specimen stages for a Philips EM400T AEM have been constructed in order to conduct deformation and fracture experiments inside the microscope. These stages utilize interchangeable control systems, outer sheaths, and inner pulling rod assemblies. The specimen geometry is shown in Fig. 1. The guide pins align the specimen grips so that upon tightening, no rotation of the grips occurs. The stages were built primarily of beryllium copper to ensure no residual magnetism. A welded metal bellows provides the vacuum seal on the pulling rod. The stages allow ±45° single-axis eucentric tilting. This tilt range easily yields 5 low order diffraction vectors for performing Burgers vector analysis of dislocations.
Electron Microscopy in Materials Science
Authors: Thomas Gareth
Published: June 2020

The materials scientist is concerned with relating microstructure and properties. In crystals, most of the important imperfections can only be observed by transmission through thin foils (T.E.M.), first accomplished by Heidenreich in 1949. The truly amazing growth of T.E.M. is due mainly to three factors: a) improvements in microscopes, b) techniques for foil preparation, c) interpretation of images using electron diffraction contrast theory. Almost all of T.E.M. has developed since 1955 as a result of the above factors.

The following is a listing of some of the applications of Electron Microscopy.

a) Observation and identification of lattice defects (dislocations, faults, small defect clusters, etc.).

b) Crystallographic data from electron diffraction.

c) Surface investigations, replication, reflection and scanning microscopy; fractography.

d) Qualitative chemical analysis of characteristic x-rays emitted by the foil.

e) Energy analyses for contrast and for identifying elements (by scanning microscopy also).

f) In situ investigations of crystal growth, epitaxy.

g) Examination of specimens at different temperatures; deformation, bombardment in situ.
Exfoliative Cytology of the Lung Alveolus: Preliminary Electron Microscopic Observations on Cells Obtained In Vivo From Human Lungs
Authors: Ladman A. J. , Pratt Susan A. , Finley T. N.
Published: June 2020

Earlier studies using endobronchial lavage of segments of dog lung have established the feasibility of this procedure to assess the physico-chemical nature of lipids lining the lung alveolus and to characterize the functional cytology of cells returned in the effluent fluid. These techniques have been tried in selected normal humans and patients with lung disease in order to establish base-lines of presumed normal values for future biochemical and morphological analyses. The present report illustrates some of the morphological features of cells recovered from “normal” volunteers, both non-smokers and smokers, and a patient having clinically diagnosed rheumatoid lung disease.

Bronchopulmonary segments of human lung were intubated with a 19F Metras retention catheter after appropriate local anesthesia of the upper airway. The cuffed tip was inflated and three 100 ml aliquots of normal saline were lavaged gently in and out through the catheter. The returned fluid was spun at 27,000 xG for 20 minutes at 0°C and the cellular sediment of the lavage was fixed in cold glutaraldehyde and post-fixed in osmium tetroxide. Following rapid dehydration in ethanol, the cells were embedded in Epon 812.
Silver Staining of Pancreatic Islets as Revealed by Electron Microscopy
Authors: Misugi Kazuaki , Misugi Nobuko , Yamada Hiroshi
Published: June 2020

The authors had described the fine structure of a type of pancreatic islet cell, which appeared different from typical alpha and beta cells, and tentatively considered that this third type of granular cell probably represents the D cell (Figure 1).

Since silver staining has been widely used to differentiate different types of pancreatic islet cells by light microscopy, an attempt to examine this staining reaction at the electron microscopic level was made.

Material and Method: Surgically removed specimens from three infants who suffered from severe hypoglycemia were used. The specimens were fixed and preserved in 20% neutral formalin. Frozen sections, 30 to 40 micron thick, were prepared and they were stained by Bielschowsky's method as modified by Suzuki (2). The stained sections were examined under a microscope and islet tissues were isolated. They were fixed in 1% osmium tetroxide in phosphate buffer for one hour and embedded in Epon 812 following dehydration through a series of alcohols and propylene oxide.
Transformation of Myoepithelial Cells into Epithelial Cells in Pregnancy
Authors: Murad T. M. , von Haam E.
Published: June 2020

The origin of the early proliferating cells of the mammary gland during pregnancy has not been determined. The mammary gland of pregnant rats was studied by light microscopy (Jeffers, 1935). The cytology of the lactating mammary gland and its modes of secretion was studied in mice (Hollmann, 1959), in rats (Bargmann, 1961), and in rabbits (Hollmann, 1966). The present investigation, by electron microscopy, was undertaken to determine the earlier changes in the developing breast during pregnancy, since cellular identification is more easily accomplished by this technique.

The mamMary glands of 12 pregnant rats the fifth day following fertilization and every 3 days thereafter until delivery, were studied by electron microscopy. The results show that the myoepithelial cells are the cells responsible for early ductular proliferation. Cytoplasmic processes are seen to project out from these cells into the stromal tissue (Figure 1). Columns of myoepithelial cells may be seen infiltrating the fatty tissue. After this stage the following cellular changes appear: The myoepithelial cells become detached and separated from one another by narrow spaces.
Junction of the Epithelium and Lamina Propria of the Bovine Rumen Mucosa
Authors: Stinson Al W.
Published: June 2020

The stratified squamous epithelium which lines the ruminal compartment of the bovine stomach performs at least three important functions. (1) The upper keratinized layer forms a protective shield against the rough, fibrous, constantly moving ingesta. (2) It is an organ of absorption since a number of substances are absorbed directly through the epithelium. These include short chain fatty acids, potassium, sodium and chloride ions, water, and many others. (3) The cells of the deeper layers metabolize butyric acid and to a lesser extent propionic and acetic acids which are the fermentation products of rumen digestion. Because of the functional characteristics, this epithelium is important in the digestive process of ruminant species which convert large quantities of rough, fibrous feed into energy.

Tissue used in this study was obtained by biopsy through a rumen fistula from clinically healthy, yearling holstein steers. The animals had been fed a typical diet of hay and grain and the ruminal papillae were fully developed. The tissue was immediately immersed in 1% osmium tetroxide buffered to a pH of 7.4 and fixed for 2 hrs. The tissue blocks were embedded in Vestapol-W, sectioned with a Porter-Blum microtome with glass knives and stained with lead hydroxide. The sections were studied with an RCA EMU 3F electron microscope.
Effect of Niacin on Mitochondria of Allium Cepa Root Cells
Authors: Hayat M. Arif
Published: June 2020

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.

Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.
Diplotene Achiasmatic Chromosomes Following Normal Synapsis at Pachynema
Authors: Roth Thomas F. , Parchman L. Gerald
Published: June 2020

Trillium microsporocytes were cultured by normal methods. When strings of meiocytes are explanted from the anther at most stages in meiotic prophase, the chromosomes proceed through an apparently normal prophase. However, if the explantation is carefully chosen at a time just prior to leptonema, prophase is abnormal. In this case, the zygotene and pachytene stages appear similar to control cultures. It is only when the cells reach diplonema that the chromosomes appear to be different.

Normally at diplonema the paired homologous bivalent chromosomes of pachynema, separate except where they are held together by one or more chiasmata. In the cells cultured from preleptonema, however, no chiasmata are evident, and where there were formerly a haploid chromosome number of 5 at pachynema, there now are 10 at diplonema through metaphase I (Fig. 1). Although the chromosomes continue to shorten and form a modified metaphase figure, segregation is random. At anaphase I, the chromatids often separate as though it were already anaphase II. Cell plate formation is aberrant in this case, resulting in a highly variable number of chromosomes being segregated into a random number of nuclei, quite unlike the normal tetrad.
Urea Extraction of Reovirus RNA
Authors: Vasquez C. , Kleinschmidt A. K.
Published: June 2020

The aim of our study was to determine the total length of reovirus RNA and to better understand the breakage of this double-stranded RNA into smaller pieces. The protein-monolayer technique with urea as a denaturative agent was used in the study of reovirus RNA (type 3). In one series of experiments we incubated the purified virus in 4M urea at 4°C for 5 minutes prior to spreading. A spreadable protein (e. g., DFP-chymotrypsin) was then added to the incubation mixture which gave rise to a stable RNA-protein film on a 0.3M ammonium acetate subphase. After transfer to supports, measurement of the contrasted filaments revealed a tri-modal distribution, showing maximaz at 0.35μ, 0.70μ, and 1.15μ. (Figure 1). Filaments longer than 2.8μ were not observed. These results are in agreement with experiments in which phenol or sodium perchlorate extraction was used, but are discrepant from experiments involving urea extraction which show a peak at about 5μ length.
Negative Stain Morphology of Herpesvirus-Type Particles Extracted From Tissue Cultures of Human Cells
Authors: Schidlovsky G.
Published: June 2020

Recent findings of Herpesvirus-type particles in human tissue culture cells originating from “normal” and cancerous individuals have been described. Negative stain studies on the fine structure of these particles (EB-3) indicate that they belong to the herpes group of viruses. However, isolation, immunofluorescence and “coating” tests have ruled out the possibility that this virus is Herpes simplex, Herpes zoster, varicella or cytomegalovirus.

It has recently been suggested that members of the papova virus group, although all having the same number of capsomeres, are distinguished from each other by the type of lattice skew present on their capsid. We attempted to detect a similar morphological distinction between the Herpesvirus-type particles and the virus of Herpes simplex. Figure 1 demonstrates the presence of three six-fold capsomeres located along the edge of a triangular face in between two five-fold capsomeres. Since these five capsomeres are located along a straight line the capsid must have a regular icosadeltahedral lattice and must have 162 capsomeres. This makes it identical to the capsid of Herpes simplex virus. We have also repeatedly observed the presence of dark “furrows” on the surface of particles permeated with phosphotungstic acid (PTA) (Fig. 2). Their disposition is compatible only with a regular icosahedral lattice.
Development of St. Louis Encephalitis Virus in the Central Nervous System of the Mouse
Authors: Murphy F. A. , Harrison A. K. , Gary G. W. , Whitfield S. W.
Published: June 2020

The capacity of St. Louis encephalitis virus to cause destruction of central nervous system tissue is especially well demonstrated in experimental infection of the mouse. Inoculation of the virus intracerebrally rather than peripherally broadens the usual focal distribution of brain lesions; and when neonatal rather than older animals are inoculated intracerebrally, the infection is characterized by a widespread destructive process.

In the present investigation, St. Louis encephalitis virus isolated by the Arbovirus Unit, NCDC, from brain tissue from a fatal human case in Dallas, Texas during an encephalitis epidemic in 1966 was used. A standard laboratory strain of the virus was also studied. Two-day-old Swiss mice were inoculated intracerebrally with approximately 103 LD50 of virus, and brain tissue was harvested from moribund animals 4 days later. Tissue was fixed in glutaraldehyde, post-fixed in OsO4, dehydrated in an ethanol series and embedded in an Araldite-Epon mixture. Sections were stained with lead citrate or uranyl acetate.
The Use of the “Microdiluter” and “Ionized” Carbon Films for Negative Staining
Authors: Stephens R. , Schidlovsky G. , Kuzmic S.
Published: June 2020

When comparing the virus concentration of various samples by negative staining it is necessary to be able to deliver consistently equal but small volumes of virus suspension and phosphotungstic acid solution (PTA). These two components have to be thoroughly mixed prior to deposition on a grid coated with a hydrophilic film.

We have found that the “microdiluter” is a convenient and economical tool for consistent dispensing of known and small equal volumes of virus suspension (0.025 or 0.05 ml). We are quantitating mouse leukemia and herpes-type virus particles suspended in 0.05 M Na Citrate. The metallic tool works by capillary action and must be pre-wetted with buffer and blotted prior to pick-up of the virus suspension for reproducible results. PTA is delivered with a pipette dropper calibrated to dispense 0.025 or 0.05 ml per drop.
Use of Uranium-Labeled Antibodies for Electron Microscopic Localization of Various Antigens in Mammalian Cells
Authors: Petrali J. P. , Donati E. J. , Sternberger L. A.
Published: June 2020

Specific contrast is conferred to subcellular antigen by applying purified antibodies, exhaustively labeled with uranium under immunospecific protection, to ultrathin sections. Use of Seligman’s principle of bridging osmium to metal via thiocarbohydrazide (TCH) intensifies specific contrast. Ultrathin sections of osmium-fixed materials were stained on the grid by application of 1) thiosemicarbazide (TSC), 2) unlabeled specific antiserum, 3) uranium-labeled anti-antibody and 4) TCH followed by reosmication. Antigens to be localized consisted of vaccinia antigen in infected HeLa cells, lysozyme in monocytes of patients with monocytic or monomyelocytic leukemia, and fibrinogen in the platelets of these leukemic patients. Control sections were stained with non-specific antiserum (E. coli).

In the vaccinia-HeLa system, antigen was localized from 1 to 3 hours following infection, and was confined to degrading virus, the inner walls of numerous organelles, and other structures in cytoplasmic foci. Surrounding architecture and cellular mitochondria were unstained. 8 to 14 hours after infection, antigen was localized on the outer walls of the viral progeny, on cytoplasmic membranes, and free in the cytoplasm. Staining of endoplasmic reticulum was intense and focal early, and weak and diffuse late in infection.
An Extemporaneous Lead Citrate Stain for Electron Microscopy
Authors: Fahmy Aly
Published: June 2020

The use of lead stains for thin sections in electron microscopy is widespread. Of the various compounds, lead citrate is commonly employed. However, Reynolds' technique for its preparation from lead nitrate and sodium citrate is time-consuming. With the availability of lead citrate commercially, from at least two suppliers (K & K Laboratories, Inc., Plainview, N. Y. and Polyscience, Inc., Rydal, Pennsylvania, 19046) we have investigated the suitability of this commercial form for the staining of thin sections.

We attempted to develop a technique for the simple and instantaneous preparation of a staining solution to be used fresh each time and then discarded. Following multiple trials at various concentrations, we formulated its preparation in a “cookbook” fashion involving a minimum of weighing and measuring. Previously boiled, cooled, double-distilled, millipore-filtered water, which can be stored in the refrigerator, is used. To 50 ml. of water add one pellet of sodium hydroxide (Merck) and stir until dissolved.
Modification of Pineal Ultrastructure by Exogenous Hormones
Authors: Turner R. A. , Rodin A. E. , Roberts D. K.
Published: June 2020

There have been many reports which establish a relationship between the pineal and sexual structures, including gonadal hypertrophy after pinealectomy, and gonadal atrophy after injection of pineal homogenates or of melatonin. In order to further delineate this relationship the pineals from 5 groups of female rats were studied by electron microscopy:

Controls

Pregnant rats

After 4 weekly injections of 0.1 mg. estradiol benzoate.

After 8 daily injections of 150 mcgm. melatonin (pineal hormone).

After 8 daily injections of 3 mg. serotonin (melatonin precursor).

No ultrastructural differences were evident between the control, and the pregnancy and melatonin groups. However, the estradiol injected animals exhibited a marked increase in the amount and size of rough endoplasmic reticulum within the pineal cells.
The Occurrence of Virus Particles in Hyperplastic Alveolar Nodules and Mammary Tumors of BALB/c Mice
Authors: Sekhri K.K. , Faulkin L.J.
Published: June 2020

It has been well established that the mammary tumors and hyperplastic alveolar nodules of many strains of mice exhibit virus particles (MTV) in thin sections. Similar lesions can be induced experimentally in biologically virus-free animals of BALB/c strain by exogenous hormones, chemical carcinogens and/or X-irradiation. Ultrastructural studies on such nodules and tumors particularly those induced by long term pituitary isografts revealed three distinct type of particles.
Pores in the Plasma Membranes of Myocardial Cells
Authors: Epling Glenwood P.
Published: June 2020

Heart muscle samples were collected from the right ventricles of twelve mature cattle and twelve pigs at slaughter and immediately prepared for electron microscopy by immersion in three different fixatives: 40% OsO4 dissolved in CCl4, 1.5% OsO4 in S collidine buffer, and in 2.5%. glutaraldehyde followed by 1.5%, OsO4. Some tissue from each animal was processed in each fixative and was embedded in either an epoxy resin or in a polyester resin. Sections were cut at 300 to 600 Å in thickness on a thermally advancing microtome, using glass and diamond knives, and were mounted on copper mesh grids. Uranyl acetate and lead citrate stains were used. Tissues were examined in an RCA, EMU-3F electron microscope.

In both the cattle and pigs, some heart samples contained myocardial cells with plasma membranes which invaginated into the cells to form tubular appearing channels. These channels occurred in addition to the transverse sarcotubular system, and in addition to the pinocytotic vesicles. The basement membrane which surrounds myocardial cells did not extend into the invaginations, but bridged over their external apertures.
Macromolecular Pattern in the Cell Envelope of a Bacillus Species
Authors: Carnahan J. , Brinton C. C. , McNary J. E.
Published: June 2020

The presence of a structured external surface layer of the cell envelope from Spirillum serpens was first described by Houwink. This “macromolecular monolayer” consists of a hexagonal array of particles. A few examples of tetragonal patterns in bacterial cell envelopes have been reported but the structural elements have not been chemically characterized. The present study is directed towards the analysis of a tetragonal pattern of a Bacillus species isolated from sewage.

The pattern could be observed on cells from young cultures negatively stained with potassium phosphotungstate (PTA). Cultures stored in the cold for several days or weeks undergo autolysis yielding large sheets of intact pattern. Electron micrographs of overlapping macromolecular monolayers show characteristic Moiré patterns (Fig. l).
Vesicles and Granules in the Retina of a Snail, Helix Aspersa
Authors: Eakin Richard M. , Brandenburger Jean L.
Published: June 2020

Sensory cells in the eyes of pulmonate snails possess extraordinary perinuclear masses of spherical vesicles, each about 800 A in diameter. They typically exhibit a paracxrystalline arrangement. The same pattern is found also in sensory cells of eyes that had completely regenerated following removal of the tip of the tentacle and the original eye several months earlier (Fig. 1). High magnification (Fig. 2) shows that the vesicles are bounded by a single membrane. In sections normal to the surface of the vesicle the inner and outer leaflets appear to have about the same thickness (20 A). The electron lucent space between the osmiophilic layers is approximately 30 A wide, making the total thickness of the membrane about 70 A. The membrane appears to be particulate in both sectional and en face views of vesicles fixed in glutaraldehyde and postfixed in OsO4. And there is a suggestion of cross bridges (arrows) between the two leaflets. The picture resembles that found by various investigators, Sjöstrand for example, in other membranes. Such images have been interpreted as indicating a globular or micellar organization of the membrane rather than a trilaminar (unit membrane) structure. Interpretation is difficult considering the possibility of image overlap artifact in viewing sections through the curved surface of a small vesicle. Faint irregular densities may be seen within the vesicles.
The Presence of Packets of Bio-Adhesives in Sea Cucumbers
Authors: Harrison G. A.
Published: June 2020

Secretory packets have been seen and described in several species of starfish (Class Asteroidea). Since many species of sea cucumbers also possess tube feet with suckers and also adhere to surfaces in the same manner as starfish, it was decided to examine their tube feet for secretory packets. Material for these studies was fixed in 3.5 to 5 % glutaraldehyde in phosphate buffer, post-fixed in osmium tetroxide also in phosphate buffer and embedded in Araldite 502 or Epon 8l2. Material for colloidal thorium studies was dehydrated and embedded in GMA.

Thin sectioning revealed a secretory packet which, although similar in size and shape to that found in starfish, differed radically from it in internal structure. All sea cucumbers investigated have shown these three components, 1) a fibrous area, 2) a light granular area, and 3) a dark granular area. The species differ somewhat in their arrangement of these components. Three of the species resemble “toadstools” and a fourth has an “onyx ring” configuration.
Application of the Short Focal Length Objective to Biological Substances
Authors: Harri W. W
Published: June 2020

Possible improvement in resolving power by use of objective focal lengths of 2 mm in the conventional transmission electron microscope has been described by Heidenreich and Armbruster and by H. Fernandez-Moran. A modified Siemens Elmiskop IA has been used to examine a plasma protein, some polyamino acids, sRNA, 50s ribosome preparations, serum albumin, and myoglobin in unsupported specimens.

Characteristics of the images obtained in defocussed images will be discussed in relation to the molecular structure of these compounds.
Reduced Confusion from Substrate Noise at High Resolution
Authors: Slayter Henry S.
Published: June 2020

The background noise contributed by the superposed images of the structural elements of standard carbon substrate films constitutes an important limitation in obtaining effective contrast in electron micrographs. It can be demonstrated that the apparent separation of noise elements decreases as exact focus is approached. The limiting apparent separation is found to be the resolution limit itself. The contrast of images of noise elements is considerable in the range 5 - 30 A, and thus has the effect of masking contrast produced by the deposition (whether specific or non-specific ) of heavy metal salt in biological objects over the same size range. If, however, the image grain size of the substrate can be reduced well below that of the heavy metal stain aggregates, the signal contributed by the latter can be distinguished from the background noise.
External Photography of the Microscope Image
Authors: Anderson K. , Kenway P. B.
Published: June 2020

It has been shown that the direct exposure of the electron image of the microscope to a photographic emulsion is an almost perfect recording system (Valentine and Wrigley 1964). This method of recording, however, has the disadvantage that it is necessary to introduce the photographic emulsions into the vacuum of the microscope. In order to overcome this difficulty the possibilities of photographing a phosphor screen on which the electron image is displayed have been investigated.

The apparatus used consisted of a transmission phosphor screen located below the normal plate camera of an EM6G electron microscope. The image produced was then photographed using an 35mm camera fitted with an F/I lens. The density - exposure curve for a number of photographic emulsions was obtained. Some of the results obtained are shown in Fig. 1. It can be seen from these results that exposures comparible with the direct exposure of the electrons to a photographic plate can be obtained.
Contrast and Resolution in Scanning Electron Microscopes
Authors: Kimoto Shizuo , Hashimoto Hiroshi , Mase Kiyoshi
Published: June 2020

In scanning electron microscopy, secondary and backscattered electrons play a most important role. When considering these two forms of signal source, it is necessary to treat them separately on the basis of contrast and resolution, since their production processes and energies are different. In practice, the electrons detected by the secondary electron detector consist of secondary electrons excited by a primary electron probe, those excited by backscattered electrons in the specimen and secondary electrons liberated from the specimen's environmental parts during backscattered electron bombardment. Consequently, it is difficult to completely eradicate the effect of backscattered electrons upon the secondary electron image. This paper presents information in regards to the differences in contrast and resolution between the secondary and back- scattered electron image under the condition of optimum secondary/backscattered electron separation. First, it was shown how secondary electron image contrast is affected by secondary electrons liberated by backscattered electrons.
Electron Fractography of Small Specimens
Authors: McMillan William R.
Published: June 2020

Specimens, 0.025 to O.125 mm. in diameter and of suitable length, were fractured and grasped in a vise which has solder-wire inserts in the jaws (Figure l). These inserts flow around both sides of the specimen and hold it with the fractured end just protruding above the surface. Three fiducial lines, scribed at nearly equal angles and radiating from the specimen, allow subsequent finding in the electron microscope of the area of interest on the replicas (Figure 2). At least two of these lines will always be visible in the usual square-meshed specimen screen.
On the Formation of Shock-Twins in Prestrained Armco Iron
Authors: Mahajan S.
Published: June 2020

The formation of a deformation twin can he divided into two stages: nucleation of a twin lamella, and growth of this lamella into an observable twin. However, the second stage can be further subdivided into three sub-headings: (i) propagation of the lamella parallel to its long dimension, i.e., the longitudinal direction, (ii) thickening parallel to its short dimension, and (iii) growth of this nucleus in a direction perpendicular to the plane containing the long and the short dimensions.

The purpose of the present investigation was to study the effect of existing substructure on the formation of mechanical twins in Armco iron. These twins were produced by shock-loading the annealed and prestrained samples to 50 and 100 Kbars, using a plane-wave generator. It should be emphasized that the desired objective can be achieved without resorting to shockloading, but thin foils from an impulsively loaded sample possess the advantage of containing many more twins and twin nuclei than foils from more conventionally stressed material, thus facilitating the analysis of results.
Twinning of Erbium Oxide Single Crystals in the Electron Microscope
Authors: Murr L. E.
Published: June 2020

During the course of investigations directed towards the preparation of concentrated solid solutions of rare earth oxides in MgO host crystals, the occasion arose where polycrystalline hep erbium metal foils vapor deposited onto cleaved NaCl substrates at room temperature (in a nominal vacuum prior to vaporization of 10−8-10−9 Torr) were observed by transmission electron microscopy. It was discovered that when an intermittent flash evaporation technique was used in the vaporization of erbium (99.95%) from high purity tungsten boats, tiny single crystals of various prominent surface orientations were formed in association with the erbium matrix, which differed significantly in structure from the matrix. The surface orientations observed for these crystals, which ranged in size from a few hundred Angstroms to a few microns on a side, were (100), (110), and (111). A rather striking feature of these crystals was the fact that if the electron beam was focused on an individual crystal, particularly in (100) orientation, the crystal began to twin from the edges by the apparent motion of “twinning dislocations” in the {110} planes; with subsequent twinning of the entire crystal taking place after a few seconds exposure at high beam intensity.
Thermal Treatment of Non-Crystalline Calcium Phosphate
Authors: Gerdes R. J. , Weber J. C.
Published: June 2020

The first solid phase of calcium phosphate salts which are prepared "by rapid precipitation from alkaline solutions gives an x-ray diffraction pattern characteristic of amorphous materials. Investigations by methods of electron microscopy show that the aperiodic nature of the atomic structure is reflected in the external morphology of these precipitates; the particles are spheroids with electron.translucent cores. The present study was undertaken to ascertain the influence of heat treatment in the electron microscope on these amorphous calcium phosphates.

The calcium phosphate salt was prepared at 25°C by rapid mixing of alkaline calcium and phosphate solutions of sufficient concentrations to produce instantaneous precipitation. A Ca/P molar ratio of 1.5 indicates that the product obtained is a neutral tricalcium phosphate. The amorphous material was prepared for examination in the electron microscope by suspending the dry solid in distilled water or in benzene or trichlorethylene. A drop of one of these suspensions was evaporated on a carbon film which covered an electron microscope grid.
The Early Stages of Growth in Gold Microcrystals
Authors: Peacock R. G. , Morriss R. H.
Published: June 2020

Thin crystals of colloidal gold exhibiting trigonal symmetry can be grown from solution by the reduction of chlorauric acid with salicylic acid. At room temperature the complete growth process requires approximately 240 hours, and the resulting crystals are about 100 Å in thickness and several microns in width. This system particularly lends itself to an electron microscopic and electron diffraction study of the nucleation and early stages of crystal growth. With this objective in mind samples were extracted from the growth medium at periodic intervals throughout the growth process and examined in the electron microscope. In order to examine the crystals at various stages of development as they actually exist in the growth medium, it was necessary to dilute the extracted samples several thousand to one with distilled water. Since this form of crystal growth is dependent on the gold concentration in the solution, dilution seems to be the most efficient way of halting growth without disturbing the crystal.
Epitaxial Growth of Sodium Chloride Films Evaporated Upon Mica
Authors: Shimaoka G. , Herold J. F.
Published: June 2020

It has been reported by Schulz using an electron diffraction technique that evaporated sodium chloride crystals grow epitaxially upon heated mica. However, several important points, for instance, the temperature at which epitaxial growth is completed and how the deposits nucleate upon the substrate, were not given in the previous reports. The purpose of the present experiment is to study the structure, orientation, shape, size and distribution of sodium chloride deposits evaporated upon mica as a function of the substrate temperature.

Sodium chloride was evaporated onto a freshly cleaved mica substrate heated at a temperature between 24° and 500°C in a vacuum of ∼ 1 × 10-4torr. Average thickness of the evaporated films was about 600Å. The specimens were divided into three parts. The first part was used for reflection electron diffraction observation. The reflection experiment was made using a specimen-charge neutralizer and for several different azimuthal positions of the deposits on the mica surface.
The Preparation of Electron Micrographs for Morphological Analysis of Carbon Black Primary Aggregates
Authors: Heckman F. A. , Medalia A. I. , Harling D. F.
Published: June 2020

Recent electron microscope studies reveal that in most grades of black the so called “primary particles” are thoroughly fused together to form primary aggregates. The size and shape distribution of these aggregates is of great importance in that it affects the color properties of the black and the rheological properties of rubber or other materials in which it is dispersed.

A new technique has been developed for characterizing size and shape distributions of primary aggregates of carbon black by computer analysis of electron micrographs.
Electron Microscopic Techniques for Fluorescent Lamp Phosphor Studies by Single Stage Replication
Authors: Walitsky Paul J.
Published: June 2020

Electron Microscopy has long been utilized in the lamp industry for the study of tungsten and other lamp components. Little information has been published regarding the use of electron microscopy in the study of phosphors, a main component in fluorescent lamps. This study concerns calcium halophosphate phosphors, a primary component of fluorescent lamps.

A modified single stage replica method similar to that of Munch has been adapted for use in the study of phosphors. The samples to be replicated were prepared by depositing the phosphor powder on a clean glass slide. Deposition was accomplished by a dry spray technique using low pressure Freon. A commercially available spray mounter can be utilized for this purpose. The critical parameter in the operation is pressure control, which when properly regulated promotes an even distribution of particles, and appears to facilitate subsequent removal of the evaporated film from the glass slide.
Preparation of Metal Foils by Mechanical Reduction
Authors: Carson K. R.
Published: June 2020

Annealed and unannealed commercially available beaten foils were used for much of the very early transmission electron microscopy of metals. The studies were restricted to the few highly malleable metals, so, when electropolishing and chemical techniques were developed that permitted many other materials to be thinned as well, beating all but disappeared. It has been found, however, that mechanical reduction techniques provide a simple and rapid means to obtain electron transparent foils of a wide variety of metals and alloys.

Tantalum, titanium, platinum, iron, permalloy, silicon-steel, brass, copper, aluminum, cadmium, tin, solder, and lead have all been beaten directly to foil simply by placing a small piece of the material on a polished steel flat and hammering with a steel mallet. The structures observed in the high melting point materials were characterized by high defect densities not unlike those found after explosive loading. Mechanical twins were observed in copper and platinum, and, in many cases structural evidence existed for localized adiabatic heating. Some of the low melting point materials investigated anneal at ambient temperatures and were observed in various stages of polygonization, recrystallization, and grain growth. Electron diffraction revealed a deformation texture in most materials.
A High Performance Energy Analyzer for Use in Electron Scanning Microscopy
Authors: Crewe A. V. , Isaacson M. , Johnson D.
Published: June 2020

A double focusing magnetic spectrometer has been constructed for use with a field emission electron gun scanning microscope in order to study the electron energy loss mechanism in thin specimens. It is of the uniform field sector type with curved pole pieces. The shape of the pole pieces is determined by requiring that all particles be focused to a point at the image slit (point 1). The resultant shape gives perfect focusing in the median plane (Fig. 1) and first order focusing in the vertical plane (Fig. 2).
Electron Microscopy of Superalloy Powders
Authors: Kotval P.S. , Dickey J.S. , Lewis B.E.
Published: June 2020

Argon or water atomized alloy powders for use in powder-metallurgy parts usually have a particle size in the range 20-200µ. Because of this small size and the accompanying difficulty in specimen preparation, studies of metal powders have usually excluded transmission techniques and knowledge of the microstructure is confined to scanning electron microscopy studies.

Fig. 1 shows a scanning electron micrograph of an argon-atomized particle of Haynes alloy 6B. It is clear that the particle is a spherical “microcasting” showing typical dendritic structure. When such particles are mounted and sectioned, the dendritic morphology is still observed (Fig. 2) indicating that there is a solidification structure throughout the particle and not just at the surface.
Combined Scanning Electron Microscopy and Electron Probe Analysis of Biological Tissues
Authors: Tousimis A. J.
Published: June 2020

Electron probe microanalysis of biological specimens since its introduction in 1957 has seen relatively few applications. Most have involved the analysis of inclusions, precipitates, normal and pathological mineralization and, to a limited extent, localization of inorganic ions or organic components associated with cellular structures. Resolving powers of 1 to 3 microns, relatively poor X-ray detectors, and lack of appropriate specimen preparation procedures, which affect both the spatial resolution and quantitative analysis, are some of the reasons for the limited application of this method. The need, therefore, for a higher resolution instrument to render biological structural details visible and the measured X-ray intensity quantitative is obvious.