bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of the Yolk (Vitelline) Membrane as an In Vitro Model to Study Yeast Adherence
Authors: Persi M. A.
Published: June 2020

Quantitation of viral, bacterial and fungal pathogenicity has been assessed using the chorioallantoic membrane (CAM) of fertilized chicken eggs, Gall us domestica. Although virulence of pathogens such as Candida albicans can be measured by inoculating the CAM, there are still limitations in controlling various endogenous environmental parameters inside the egg. The in vitro membrane model introduced here, when used to study adherence and how it may lead to pathogenicity, has several advantages. It is simple and inexpensive membrane and membrane holder apparatus which allows for easy membrane removal and isolation; but the best advantage is the ability to control the environmental parameters at the membrane's surface such as CO2/O2 tension, pH and temperature which may play an important role in attachment and which cannot be controlled while the CAM is inside the egg.

The egg shell of a large unfertilized grade A egg was aseptically punctured, the inner and outer shell membranes were removed at the air-sac end of the egg, the egg white was extracted and the unruptured yolk was removed from the egg shell.
A Tetragonal Lattice in Mammalian Lens Junctions
Authors: Robertson J.D. , Zampighi G. , Simon S. , McIntosh T.J. , Costello M.J.
Published: June 2020

A pure fraction of junctional membranes has been isolated in milligram quantities from bovine lens without detergents. SDS-PAGE analysis shows a major band at 27,000 d and a minor one at 21,000 d. Thin section electron microscopy (EM) of this fraction revealed junctions of two closely apposed membranes with an overall thickness of 135-140 Å with a wavy contour and lengths greater than 10 μm. Negative stain and freeze-fracture (FF) EM (only unetched specimens so far) and X-ray diffraction studies of unfixed and unglycerinated specimens were in agreement regarding the structure of the junctions. They consisted primarily of extensive domains of sub-units arranged in a 66 Å tetragonal lattice. Specimens were spun down centrifugally in a Beem capsule and partially dried for the x-ray diffraction studies. The X-ray patterns contained several reflections which indexed on a tetragonal lattice of 66 Å in the equatorial direction parallel to the plane of the membranes and several bands of a continuous transform in the meridional direction consistent with membrane pairs. No diffraction was seen at 85 Å in the equatorial direction.
Microanalysis of Calcium and Phosphorus in Biology Using Electron Energy Loss Spectroscopy
Authors: Leapman R.D. , Swyt C.R.
Published: June 2020

Quantitative microanalysis of the important elements calcium and phosphorus in thin biological samples is normally performed using EDX spectroscopy. Sometimes, however, it is helpful to obtain additional information such as the relative amounts of nitrogen and oxygen present. EELS is sensitive to these low-Z elements and in certain cases can also improve P and Ca detection limits because of the higher EELS counting rate. Here we demonstrate the feasibility of Ca:P:Q:N ratio determinations, though we must be cautious about the N and O ratios because of mass loss.

Fig. 1(a) is a STEM image of isolated dense bodies extracted from human blood platelets by sonication and then centrifuged onto a thin carbon substrate. The dense bodies which are typically 1000 Å in diameter were well separated from other constituents of the cells. Fig. 2(a) shows an EELS spectrum from a dense body about 800 Å in diameter. It was recorded at 100 keV beam energy with a Hitachi spectrometer attached to an H700H electron microscope.
Ultrastructural Morphology of the Plastids in Ferocactus Latispinus (Haworth)
Authors: Rivera E. R.
Published: June 2020

Mature plants of Ferocactus latispinus were divided into the apical meristem, cortical and cambial tissue, and young and mature photosynthetic tissue. Pieces 2x2x4 mm were fixed in 0.075 M PIPES buffered 5% glutaraldehyde and further treated for conventional transmission electron microscopy.

The shoot meristematic cells contained dense cytoplasm with a few small vacuoles. All organelles expected to be found in unspecialized plant cells were present. The proplastids were 1-2 diameters larger than mitochondria. Some of these plastids were elongated and most contained small amounts of lipid globules in the stroma (Fig. 1). In addition, phytoferritin was sometimes found in the stroma. No starch was found in these organelles. The thylakoids were poorly developed, and when there were no inclusions in the stroma, proplastids were difficult to distinguish from mitochondria (Fig. 1).

Cortical cells had very large, well-developed vacuoles. The organelles were restricted to the peripheral cytoplasm of the cell and to a few transvacuolar cytoplasmic strands.
Structured Matrices Associated With Adenovirus-Infected Swine Kidney Cells
Authors: Ritchie A. E. , Norman J. O.
Published: June 2020

Fibrillar matrices (viroplasms) have been described for a number of viruses, mainly from studies of thin-sectioned infected cells. We have recently noted some structured matrices (observed in negatively-stained preparations) that were associated with swine kidney (SK) cells infected with an Adenovirus, infectious canine hepatitis. These cellular fragments may bear some special relationship to the process of viral maturation.

Virus was propagated in primary swine kidney cell monolayers. Cell culture harvests were pooled and clarified by centrifugation at 1000 X g for 20 min at 4 C. The pelleted materials were dispersed in 5 to 10 times their volume of distilled water and sampled directly for phosphotungstate (PTA) negative staining: one drop of the suspension was diluted with ca. 15 drops of 1% PTA which contained a trace of bovine serum albumin (Fr. V); the sample was then applied to carbon-coated collodion-filmed grids with a Vaponefrin all-glass nebulizer (Brenner & Horne. Biochim. Biophys. Acta 34: 103 (1959). The process of nebulizing appeared to rupture those cells that reached the specimen grid permitting examination of cellular fragments in great variety.
Bacteriophage ФX 174
Authors: Bayer M. E.
Published: June 2020

Cultures of Escherichia coli CIA (Bertani) growing logarithmically in nutrient medium were infected with 5 to 200 bacteriophage §X 174 per cell. At various times after infection the cultures were fixed for 1 hour in nutrient medium containing 5% formaldehyde pH 7, then pelleted and resuspended in 1% OSO4 in L-medium pH 7 for 1 hour; the material was pelleted again and resuspended in a mixture of 1% OsO4 and 1% uranyl-acetate in water; in this mixture the cells were fixed for 10 hours at 20° C; after fixation they were dehydrated in acetone and embedded in Vestopal W. In ultrathin sections the first structural changes became visible 15 minutes after infection when some of the cells seemed to swell and round up. In the cells small aggregates of electron dense material were observed in the chromosomal areas, and sometimes virus particles were also seen within the area of the cells’ chromosome.
An Ultrastructural Study of Pericytes
Authors: Murad T. M. , von Haam E.
Published: June 2020

Pericytes are vascular satellites present around capillary blood vessels and small venules. They have been observed in almost every tissue of the body and are thought to be related to vascular smooth muscle cells. Morphologically pericytes have great similarity to vascular endothelial cells and also slightly resemble myoepithelial cells.

The present study describes the ultrastructural morphology of pericytes in normal breast tissue and in benign tumor of the breast. The study showed that pericytes are ovoid or elongated cells separated from the endothelial cell of the capillary blood vessel by the basement membrane of endothelial cell. The nuclei of pericytes are often very distinctive. Although some are round, oval, or elongated, others show marked irregularity and infolding of the nuclear membrane. The cytoplasm shows mono-or bipolar extension in which the cytoplasmic organelles are located (Fig. 1). These cytoplasmic extensions embrace the capillary blood vessel incompletely. The plasma membrane exhibits multiple areas of focal condensation called hemidesmosomes (Fig. 2, arrow). A variable number of pinocytotic vesicles are frequently seen lining the outer plasma membrane. Normally pericytes are surrounded by a basement membrane which is found more consistently on the outer plasma membrane separating the pericytes from the stromal connective tissue.
Post Staining Procedure for Detecting Structural Differences Between Closely Related Bacterial Spores
Authors: Kramer M. J. , Roth Ivan L.
Published: June 2020

The presence of a nap of hair-like projections originating from the exosporium of Bacillus anthracis Sterne spores has been reported by several investigators. A very similar nap has also been observed on spores of the Akashi strain of B. anthracis. The present work was undertaken to determine the minimum post-staining procedures necessary to visualize the nap, as well as those procedures which would result in the best resolution of the nap. In addition to spores of the Sterne strain of the anthrax bacillus (avirulent), we examined spores of the Vollum strain (virulent) and a rough, avirulent variant of the Vollum. It was of interest to us to determine whether the ultrastructure of the nap surrounding the exosporium of the Vollum strain would be similar to that found on the Sterne strain. Discernment of a very different layer on the spores of the former strain may now be reported.
The Fine Structure of Alginic Acid Components
Authors: Inoue S. , Tanaka Y. , Skoryna S.C.
Published: June 2020

Sodium alginate, a brown seaweed polysaccharide, is capable of preventing intestinal absorption of radioactive strontium and its radiotoxicological importance is now well established. Alginic acid was found to be composed of 1,4-linked poly-L-guluronic acid and poly-D-mannuronic acid chains with some glycosidic linkages between these uronic acids.

Polyguluronic and polymannuronic acid were prepared by acid hydrolysis of alginic acid from Laminaria hyperborea followed by fractionation of the partially degraded sodium alginate at pH 2.8. These components consist almost exclusively of a single uronic acid (polyguluronic acid: man/gul = 0.27; polymannuronic acid: man/gul = 10.7). Sodium polyguluronate inhibits absorption of radiostrontium more effectively than sodium polymannuronate.
Drug Induced Changes in Cell Organelles
Authors: Luse Sarah A.
Published: June 2020

In the mid-nineteenth century Virchow revolutionized pathology by introduction of the concept of “cellular pathology”. Today, a century later, this term has increasing significance in health and disease. We now are in the beginning of a new era in pathology, one which might well be termed “organelle pathology” or “subcellular pathology”. The impact of lysosomal diseases on clinical medicine exemplifies this role of pathology of organelles in elucidation of disease today.

Another aspect of cell organelles of prime importance is their pathologic alteration by drugs, toxins, hormones and malnutrition. The sensitivity of cell organelles to minute alterations in their environment offers an accurate evaluation of the site of action of drugs in the study of both function and toxicity. Examples of mitochondrial lesions include the effect of DDD on the adrenal cortex, riboflavin deficiency on liver cells, elevated blood ammonia on the neuron and some 8-aminoquinolines on myocardium.
Ultrastructure of Blood Vessels of the Area Pellucida of Control and X-irradiated Chick Embryos
Authors: Sanderson Margaret H. , Steamer S. Phyllis
Published: June 2020

The chick embryo exposed to lethal doses of ionizing radiations develops a fatal circulatory failure within a few hours. This report describes the blood vessels of the area pellucida (a part of the extra-embryonic membranes of the chick embryo) and the effect of 250 kVp x-radiation upon them.

Three-day chick embryos, x-irradiated in ovo with 1000-1200 R, were fixed 1-2 hours after exposure. The area pellucida is a multi-layered membrane consisting of ectoderm, somatic and splanchnic mesoderm, and endoderm (Fig. 1). The vascular system arises from the splanchnic mesoderm. The walls of small and medium-sized vessels are composed of endothelial cells, an occasional pericyte and processes of adjacent mesenchyme cells. Types of vessels cannot be distinguished at this stage of development; a basement membrane is seen only in isolated areas. The wall appears double or triple-layered, but the endothelium is frequently less than 0.1 micron thick (Fig. 2). Endothelial cells contain a large complement of polyribosomes, mitochondria, rough and smooth endoplasmic reticulum, a Golgi complex, pinocytotic vesicles and several kinds of inclusion bodies. The nucleus has a well-defined nucleolus.
Mitochondria in Cardiomyopathy: Alterations in Size, Number and Internal Structures
Authors: Hug George , Schubert William K.
Published: June 2020

A white boy six months of age was hospitalized with respiratory distress and congestive heart failure. Control of the heart failure was achieved but marked cardiomegaly, moderate hepatomegaly, and minimal muscular weakness persisted.

At birth a chest x-ray had been taken because of rapid breathing and jaundice and showed the heart to be of normal size. Clinical studies included: EKG which showed biventricular hypertrophy, needle liver biopsy which showed toxic hepatitis, and cardiac catheterization which showed no obstruction to left ventricular outflow. Liver and muscle biopsies revealed no biochemical or histological evidence of type II glycogexiosis (Pompe's disease). At thoracotomy, 14 milligrams of left ventricular muscle were removed. Total phosphorylase activity in the biopsy specimen was normal by biochemical analysis as was the degree of phosphorylase activation. By light microscopy, vacuoles and fine granules were seen in practically all myocardial fibers. The fibers were not hypertrophic. The endocardium was not thickened excluding endocardial fibroelastosis. Based on these findings, the diagnosis of idiopathic non-obstructive cardiomyopathy was made.
Specimen Surface Contamination and the Loss of Structural Detail in Freeze-Fracture and Freeze-Etch Preparations
Authors: Kreutziger G. Oscar
Published: June 2020

The presence of particles and the absence of depressions or pits of sizes and numbers corresponding to the particles has raised definite questions on the interpretation of freeze-fracture and freeze-etch preparations. In shadow preparations it is well known that the thickness of the deposited metal can result in the loss of surface detail; holes and pits are filled-in and closed, fine particles are obscured, and the size of large particles increases. A similar sequential loss in specimen surface detail resulting from surface contamination prior to replication is illustrated in freeze-etch preparations of the tight junction of mouse heart muscle. Illustrations have been selected from the developmental period of the simple freeze-etch device and it's further modification.

In the most favorable preparation the intracellular plasmalemma surface has a sparce particle population, it reflects the closer membrane apposition of the tight junction and the surface within the junction proper is particle free but is populated by numerous pits: the intercellular plasmalemma surface is covered with a dense particle population outside the junction and has the packed hexagonal particle array within the junction proper (Fig. 1).
Examination of Rabbit Fc Crystals
Authors: Robinson J. P. , Lenhert P. G.
Published: June 2020

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.

Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.
Release of Neurosecretion in the Crayfish Sinus Gland
Authors: Shivers Richard R.
Published: June 2020

The sinus gland is a neurohemal organ located in the crayfish eyestalk and represents a storage site for neurohormones prior to their release into the circulation. The sinus gland contains 3 classes of dense, membrane-limited granules: 1) granules measuring less than 1000 Å in diameter, 2) granules measuring 1100-1400 Å in diameter, and 3) granules measuring 1500-2000 Å in diameter. Class 3 granules are the most electron-dense of the granules found in the sinus gland, while class 2 granules are the most abundant. Generally, all granules appear to undergo similar changes during release.

Release of neurosecretory granules may be initiated by a preliminary fragmentation of the “parent granule” into smaller, less dense vesicles which measure about 350 Å in diameter (V, Figs. 1-3). A decrease in density of the granules prior to their fragmentation has been observed and may reflect a change in the chemical nature of the granule contents.
Non-Functioning Delta Cell Carcinoma of Pancreatic Islets
Authors: Bencosme Sergio A. , Ramchand S. , Huang S. N.
Published: June 2020

In recent years there has been considerable interest in the identity, structure and function of delta cells of pancreatic islets. Williams states that the Zollinger-Ellison Syndrome is associated with neoplasms of delta cells and that these cells secrete gastrin. However, other functions have also been attributed to these cells. An excellent critical review on the identity, structure and possible function of delta cells has been published by Fujita. Clearly all new criteria for identification of delta cells must refer back to those given by Bloom in his original description in 1931.

The present report deals with a malignant islet cell tumor of the pancreas in a case autopsied twelve hours after death. By light microscopy tumor cells possessed the classical tinctorial properties of delta cells; the tumor was thus classified as a delta cell carcinoma. Considerable confusion exists on the ultrastructural identification of delta cells in man. Hence, it was decided to investigate the fine structure of these tumor cells and to compare them to non-tumor islet cells of the same patient. To best interpret our results in post mortem material the pancreas of three patients autopsied at three, six and twelve hours after death were processed and studied in a similar manner as the pancreas bearing the tumor. By electron microscopy three types of islet cells could be identified in pancreas taken three hours post mortem.
Electron Microscopy in Studies on the Relationship of Viruses to Tumors in Animals and Man
Authors: Dmochowski Leon
Published: June 2020

Both DNA- and RNA-carrying viruses play a part in the origin of many tumors in animals and may be involved in some types of neoplasia in man. Presently only some RNA viruses and neoplasia will be discussed. Electron microscopy, combined with biophysical, biochemical and biological approach, has laid foundation of present-day knowledge of viruses being causative factors of many types of neoplasia in animals. The appearance, size, internal structure, and mode of development of a number of RNA-viruses in neoplasia are now known. Electron microscopy has either followed or preceded biological studies on causation of neoplasia by viruses. In either case its contribution has been invaluable.

Since the observation of virus particles in mammary tumors of mice (Dmochowski, L. : J.Nat.Cancer Inst.15,785 (1954)), they are now known to be the causative agent of this neoplasia. They are widely distributed in milk of various strains of mice and present long before signs of neoplasia appear. Chemical, physical factors and leukemia virus may stimulate mammary tumor virus and lead to mammary neoplasia. Search for similar virus in milk and breast cancer of women revealed structures resembling virus particles.
Surface Treatment in Solar Cell Technology
Authors: Evans J. C. , Evans K. M.
Published: June 2020

In the fabrication of solar cells of both the crystalline and thin film types, surface treatment has been found to play a decisive role. The electron microscope has been used in an attempt to isolate and to optimize those surface features which contribute beneficially towards increased cell performance. From our work thus far it is suspected that surface roughness plays a significant role in the efficiency of light-trapping so basic to this form of energy conversion device. We have observed that etchants used to prepare the semiconductor surfaces often attack these surfaces quite selectively, producing identifiable surfaces determined by the etchant used and the semiconductor so treated. For example, an etch of a cadmium sulfide vacuum evaporated film with hydrochloric acid, one part in three parts of distilled water produced an etch less harsh or rough as a similar dilution of phosphoric acid in the same time period.
The Fine Structure of Replicating Simian Adenoviruses in LLC-MK2
Authors: Pardo Matias , Slifkin Malcolm , Merkow Leonard , Sanchez Marie
Published: June 2020

The simian adenoviruses SV20, SV30 and SA7 have been found to be oncogenic in the Syrian hamster. The growth characteristics and replicative cycle of these viruses in tissue culture therefore appeared appropriate to investigate. Cesium chloride purified simian adenovirus with an infectivity titer of 100 TCID50, was inoculated into monolayers of LLC-MK2 cells. Cells were fixed in osmium tetroxide and embedded for ultrastructural studies at 1, 3, 6, 9, 18, 24, 48, 72, 120 and 192 hours post-infection.

At the first hour post-infection, virus particles were adsorbed to the plasmalemma and found within the peripheral cytoplasm of many LLC-MK2 cells (Fig. 1). Although the first detection of infectious virus occurred at 14 hours and infectivity titers did not reach a maximum until 30 hours, intranuclear virus particles were observed by 3 hours in typical adenovirus crystalline array (Fig. 2) by means of electron microscopy. These typical honeycomb arrayed virus particles at 3 hours provided evidence of significant replication in approximately 5 percent of tissue culture cells examined. Simultaneously, a classical nuclear inclusion manifested by peripheral condensation of nuclear chromatin was evident by light microscopy. As early at 6 to 9 hours, unusual intranuclear concentric membranes formed “tubes” which contained linear arranged virus particles (Fig. 3). In transverse or tangential sections, these “tubes” appeared cochlear-like in shape. In longitudinal section, these intranuclear tubular structures contained individual virus particles at various stages of maturation in a linear arranged order. This arrangement resembled “peas in a pod”.
Electron Microscopy of a Herpesvirus Isolated from Marek's Disease in Duck and Chicken Embryo Fibroblast Cultures
Authors: Nazerian Keyvan
Published: June 2020

A herpes-like virus has been isolated from duck embryo fibroblast (DEF) cultures inoculated with blood from Marek's disease (MD) infected birds. Cultures which contained this virus produced MD in susceptible chickens while virus negative cultures and control cultures failed to do so. This and other circumstantial evidence including similarities in properties of the virus and the MD agent implicate this virus in the etiology of MD.

Histochemical studies demonstrated the presence of DNA-staining intranuclear inclusion bodies in polykarocytes in infected cultures. Distinct nucleo-plasmic aggregates were also seen in sections of similar multinucleated cells examined with the electron microscope. These aggregates are probably the same as the inclusion bodies seen with the light microscope. Naked viral particles were observed in the nucleus of infected cells within or on the edges of the nucleoplasmic aggregates. These particles measured 95-100mμ, in diameter and rarely escaped into the cytoplasm or nuclear vesicles by budding through the nuclear membrane (Fig. 1). The enveloped particles (Fig. 2) formed in this manner measured 150-170mμ in diameter and always had a densely stained nucleoid. The virus in supernatant fluids consisted of naked capsids with 162 hollow, cylindrical capsomeres (Fig. 3). Enveloped particles were not seen in such preparations.
An Electron Microscopic Study of the Acute Effects of Hypothalamic Releasing Factors on the Anterior Pituitary Gland
Authors: Coates P.W. , Ashby E.A. , Krulich L. , Dhariwal A. , McCann S.
Published: June 2020

The morphologic effects on somatotrophs of crude sheep hypothalamic extract prepared from stalk-median eminence were studied by electron microscopy in conjunction with concurrently run bioassays performed on the same tissue samples taken from young adult male Sherman rats.

Groups were divided into uninjected controls and injected experimentals sacrificed at 5', 15', and 30' after injection. Half of each anterior pituitary was prepared for electron microscopic investigation, the other half for bioassay. Fixation using collidine buffered osmium tetroxide was followed by dehydration and embedment in Maraglas. Uranyl acetate and lead citrate were used as stains. Thin sections were examined in a Philips EM 200.

Somatotrophs from uninjected controls appeared as described in the literature (Fig. 1). In addition to other components, these cells contained moderate numbers of spherical, electron-dense, membrane-bound granules approximately 350 millicrons in diameter.
Defects in Crystals
Authors: Lawless Kenneth R.
Published: June 2020

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.

Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.
Studies of Extended Dislocation Configurations in HCP Silver-Tin Alloys
Authors: Ruff A. W. , Ives L. K.
Published: June 2020

Recently we have reported the stacking fault energy in a series of hcp silver-tin alloys as a function of composition. The stacking fault energy was found to increase linearly with composition from 5.5 erg/cm2 for an 11.9 at.% tin alloy to 18.9 erg/cm2 for a 17.2 at.% tin alloy. Measurements were made on extended dislocation nodes and double-ribbons observed in thin foils by means of transmission electron microscopy. During the course of this investigation a number of dislocation configurations were observed as the result of interactions between extended dislocations lying on adjacent basal planes. Many of these configurations were identical to those which have been extensively studied by Delavignette and Amelinckx in hexagonal graphite. The same basal plane faulting pattern is found there as in the hcp structure. We have observed other configurations in these alloys that could be associated with cross-slip of basal dislocations or with their interactions with non-basal dislocations. It is the purpose of this paper to discuss faulting in the hcp structure and to describe several of the dislocation configurations observed in these silver-tin alloys.
Some Dislocation Features in Deformed Copper and Alpha Brass
Authors: Grace F. I.
Published: June 2020

The nature of the dislocation arrays in f.c.c. metals after conventional deformation has been shown to be a function of the stacking fault energy. For metals with high stacking fault energy, such as copper, nickel and aluminum, the dislocations responsible for plastic deformation appear in the form of a cell structure. When the stacking fault energy is low, cell structures are not observed. At present, there are indications that the stacking fault energy may also be important when unconventional means of deformation are encountered, as in the case of shock loading. Nolder and Thomas and Johari and Thomas observed cell structures in nickel and copper while Otte and Holland and Inman, Murr and Rose observed layered-type structures in silicon bronze and 304 stainless steel after shock deformation.
A Review of Methods for Determining the Nature of Small Defect Clusters
Authors: Rudee M. L.
Published: June 2020

When a crystalline material is damaged by fast neutron irradiation, the most common defects encountered are small aggregates of vacancies or interstitial atoms. The images observed range from about 150Å down to the resolution limits of the contrast producing mechanism. An understanding of these defects is quite important to theories of irradiation damage, and a significant effort has been directed towards unraveling their nature. The development of the appropriate diffraction contrast techniques has been marked by a number of controversies. Since many are now resolved, this seems a salutary time to put forward a review of the present state of affairs.

An image of a defect cluster is a result of the strain field, either expansion or contraction, in the surrounding lattice. Calculations of the contrast from such a strain field have been performed by Ashby and Brown, and more recently by Rühle et al., and McIntyre and Brown. These authors used the two-beam wave-optical dynamical theory of diffraction contrast including anomalous absorption, and the images predicted have two-lobes, one darker and the other lighter than the background.
Hitachi Model XMA-5 Electron Probe Microanalyzer
Authors: Tomura  , Okano  , Hara
Published: June 2020

The recent advancement in scientific instrumentation has been phenomenal. This is particularity true in the electron probe microanalyzer field. This paper describes the improvements made in the Hitachi Model XMA-5 Electron Probe Microanalyzer to achieve high performance.

1.

X-ray spectroscopy

1-1.

It is now possible to analyze a wide variety of elements including ultra light elements in minute concentrations with the advent of an increasing number of dispersing elements and high detectability.

1-2.

A linear crystal drive and direct wavelength read-out (with respect to the crystal) is employed in the spectrometer to assure simultaneous analyses of up to three elements by using three of the six crystals provided. For correction of absorbed X-rays and fluorescence excitation and with due consideration of the angular distribution of the characteristic X-rays, an X-ray take off angle of 38° (electron probe is incident vertically on the specimen surface) was adopted.
A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes
Authors: Christov George , Lloyd Bolivar J.
Published: June 2020

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.

The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.
The Oak Ridge Program for High Resolution Microscopy
Authors: Worsham R. E. , Harris W. W. , Welton T. A.
Published: June 2020

In the latter part of 1967, a program began at the Oak Ridge National Laboratory for the development of high resolution microscopy. The immediate design goal is a point-to-point resolution of at least 1 Å, to allow superior delineation of organelle structures, as well to offer a possibility of atomic identification and location in complex biomolecules. The proposed techniques seem to offer in principle the possibility of resolution limited only by random thermal motion in the sample.

Theoretical studies of both lens aberrations and image formation are being actively pursued. The aberration studies are aimed at design of a practical corrector for the primary spherical aberration, along lines first suggested by Archard. The image studies partially described elsewhere in these proceedings are aimed both at optimizing instrument performance and at the development of adequate methods for interpretation of high resolution phase contrast data.
High Voltage Microscopy of Thick Specimens
Authors: Hart Raymond K.
Published: June 2020

The aspect of high voltage electron microscopy which makes it inviting to solve both biological and physical problems is the ability of this technique to probe thicker specimens and at higher resolution than is currently possible with conventional electron microscopes. Naturally, there will be a thickness limit above which an electron beam will cease to be an effective means of obtaining useful microscopical data. The ultimate limit will be determined by the specimen induced chromatic aberration, resolution, contrast processes, and transmitted intensity available for image production.

Recently Uyeda and Nonoyama have determined the maximum usable thickness of molybdenite for operating voltages up to 1.2 MeV. They showed that this thickness is approximately proportional to kβ2, where k is a small constant and β is the ratio of the velocity of an electron to that of light. Aluminum has also been observed to follow this β2 relationship. Even thicker specimens have been viewed with fair clarity, indicating that anomalous transmission effects can occur in crystalline material. These are thought to be due to directional dependence of the absorption coefficient. For aluminum, the thickness of specimens showing anomalous transmission would fall above curve A in Figure 1.
A Field Emission High Voltage Electron Gun
Authors: Eggenberger D. N. , Hart R. K. , Libal A. C.
Published: June 2020

Progress in electron microscopy toward higher resolution and higher voltage has generated new approaches in addition to upgrading conventional methods in instrumentation. For scanning microscopy the resolution is of the order of the focussed beam spot size so progress here depends upon decreasing this size, which in turn may require a smaller source size. A major step has been made by using a cold emission tip source along with an anode system specifically designed for minimizing spherical aberration.

A cold emission tip electron source has several advantages for electron microscopy. The apparent size of the electron source is very small, about 30 Å ideally, compared to conventional thermionic emitters. The energy spread of electrons is about 0.2 eV, a useful fact where energy analysis is part of the system. Also the brightness is several orders of magnitude higher than can be obtained in thermionic emitters.
Observation of {111} Atomic Planes in Silicon and Germanium
Authors: Phillips V. A. , Hugo J. A.
Published: June 2020

The resolution of features with a size scale of lattice dimensions promises to open up a whole new field of physical research. Studies of lattice defects, local strains, grain boundaries, and mechanisms of phase transformations appear feasible. Resolution of atom rows or even individual atoms may prove possible. The new Philips EM300 microscope incorporates a number of special features which facilitate lattice resolution studies. Using this instrument we have successfully resolved the (111) planes of 3.27 Å spacing in germanium (Fig.l) previously resolved by Parsons and Hoelke, and the (111) planes of 3.14 Å spacing in silicon (Fig.2). The image quality was very good, permitting enlargement at up to 25X directly off the plate of acceptable quality.
Thin Film Nucleation and Growth Under Controlled Conditions
Authors: Poppa Helmut
Published: June 2020

Results of controlled in-situ nucleation experiments inside the electron microscope were reported recently. The experimental technique employed permitted detailed quantitative studies of the nucleation kinetics which led to a comparison of test results with nucleation theoretical predictions. However, the background pressures were still of the order of 10-7 to 5x10-8 torr and the experimental arrangement did not provide for producing and maintaining clean single-crystal substrates. It was therefore necessary to limit the choice of substrate-overgrowth material combinations, delete epitaxial studies completely, and defer meaningful investigations of the effect of residual gases on nucleation and growth processes. In addition, the influence on the experimental results of the high-intensity imaging electron beam could only be assessed in a qualitative manner.

A research program involving two methodically different experimental approaches has since been initiated that promises to eliminate most of the previous test restrictions. The two approaches entail the use of a modified low-energy electron diffraction (LEED) system in conjunction with extraction replica electron microscopy, and a newly designed ultrahigh-vacuum (UHV) electron-microscope specimen chamber in combination with a microscope image intensifier system for in-situ deposition studies.
Frozen Sectioning of Porous Polymer Membranes for Electron Microscopy
Authors: Koch E. F.
Published: June 2020

A technique has been devised using a diamond knife ultramicrotome in conjunction with a freezing head to prepare thin sections of porous polymer membranes. The thin sections are examined and photographed in transmission with an electron microscope to reveal the hole sizes in the membranes.

Attempts to microtome a particular type of porous polymer membrane at room temperature proved unsuccessful, since the polymer membrane was not strong enough to support Itself when cut to appropriate viewing thicknesses of about 250 Å to 500 Å. It was thought that some degree of rigidity could be imparted to the polymer by cooling it below room temperature. Therefore, a freezing head was made for the Porter-Blum microtome, similar to the one developed by Crudgington, Fig. 1.
Phase Structure in Blends of Incompatible Polymers
Authors: Brodsky P. H. , Cocks G. G. , Winding C. C
Published: June 2020

Microscopical observations of films made up of two incompatible polymers may provide useful insights into the unusual properties of many polymer blends. In the present study an attempt has been made to determine the factors which control the sizes and shapes of the phases present in solution-cast, two-polymer films. The variables included the ratio of the two polymers, the concentration of the solution from which the films were prepared, and the type of solvent used.

The polymers studied included poly(vinyl acetate), a copolymer containing 85% poly(vinyl chloride) and 15% poly(vinyl acetate), poly(methyl methacrylate, and polystyrene. These will be abbreviated PVAc, PVC copolymer, PMMA, and PS respectively. The solvents included methyl ethyl ketone (MEK), toluene, benzene, and chloroform and the solution concentrations were varied from 0.2 to 1.0 per cent solids by weight.
Orientation Dependence of Deformation Mode in Ti Single Crystals
Authors: Fujishiro S. , Gegel H. L.
Published: June 2020

The deformation mode of Ti single crystals by plane-strain compression has been studied at room temperature by means of transmission electron microscopy. Rectangular specimens (l/4x 3/8 x 1/2″) were cut from a large single crystal grown by the transformation annealing method. The surfaces of the specimens were flattened by No. 0 Emery papers and subsequently polished by an electrochemical method in order to remove the mechanically affected zone by at least 5 microns. By an etch pit technique the dislocation density of the specimen thus prepared was found to be of the order of 106/cm2. The oxygen impurity level, which has been reported to drastically change the ratio of the resolved shear stresses on (0001) and ﹛100﹜, was 300 ppm. The plane normals of the specimens, determined by x-ray Laue method, are plotted in Fig. 2(A). It was found that twinning played a nominal role in specimen S1 01 whereas in S1 02 and S1 03 a great number of ﹛102﹜ were predominantly observed at the early stage of deformation (up to 2%). By attributing the catastrophic yield drop in S1 02 to twinning, the resolved shear stress for ﹛102﹜< 011> twins was derived to be 5.25 kg/mm2, which is roughly twice that of the prismatic slip.
Grain Boundary-Surface Energy Ratios in Vapor-Deposited Copper and Silver Films
Authors: Sefton L. R. , Kaufman S. M.
Published: June 2020

The ratio of grain boundary energy (γ gb) to surface energy (γs) has been measured for copper by Gjostein and Rhines and for silver by Winslow and Shewmon using the “thermal grooving” technique. “Thermal grooving” is normally performed under inert or reducing atmosphere on bicrystals of carefully controlled misorientation often requiring lengthy anneals in order to obtain measurable groove angles at the grain boundary-surface intersection. Values of this angle at the root, or tip, of the groove are then used to calculate (γ gb/γ s). In this investigation similar experiments were performed using a Phillips EM200 equipped with a goniometer hot stage and copper and silver film specimens. The purpose of these experiments was to evaluate whether this type of measurement can be made more efficiently on submicron particles due to the proliferation of boundaries intersecting free surfaces as well as the enhanced kinetics resulting from high surface to volume ratios.
Effects of Hydrogen on Cathodically Charged 6Al-4v and 6Al-6v-2Sn Titanium Alloys
Authors: Danovich J. F. , Sipes W. A.
Published: June 2020

The αβ-Ti-alloys, like the high strength steels, show a susceptibility to delayed fracture and to hydrogen embrittlement. These similar modes of failure suggest that the same failure mechanism, i.e. diffusion and concentration of hydrogen, is active in both materials. To establish base line information for such a comparison, the replication technique of electron microscopy was used to study the fracture surfaces and microstructures of candidate αβ-Ti alloys cathodically charged with hydrogen. As-received mill annealed samples were studied in addition to cathodically charged specimens so as to eliminate spurious results due to artifacts.

Figure la shows the normal microstructure of the as-received 6Al-4V alloy near the surface of the specimen. Figure 1b shows the effect of hydrogen in an approximately 1/128″ deep sub-surface zone of a cathodically charged specimen. Here the matrix substructure was affected while the beta phase became clearly delineated. Beyond 1/128″ from the surface, the matrix interior was unaffected.
Grain Size and Physical Properties of Co-Evaporated Cr-Cu Thin Film Alloys
Authors: Anderson Ronald M. , Beaudouin Pierre L.
Published: June 2020

Experiments were carried out to determine resistivity and stress as a function of grain size and composition in co-evaporated Cr-Cu alloys. The films were evaporated from two adjacent sources which were selected for their reliability. The Cu was melted in a radiantly heated Mo crucible. The Cr was sublimated from an arc-melted high-purity Cr bar which provides an exceptionally constant evaporation rate. The depositions took place in a standard evaporator with a liquid nitrogen-cooled stainless steel bell jar in the range of 10-7 Torr. Substrate temperatures were maintained at 200°C.

The evaporated film thicknesses were between 1000A and 4000A and, when required, were thinned by RF sputter etching. The compositional analysis was performed by x-ray fluorescence and complemented by electron microprobe techniques.
Fractographic Observations of Sapphire Whisker Reinforced Alumina
Authors: Hermann R. A. , Divecha A. P. , Lare P. J. , Hahn H.
Published: June 2020

Fiber reinforcement of ceramics has generally been limited to metallic fibers. Metallic fibers have improved the thermal properties of ceramics but have generally been ineffective in promoting increased strengthening. Discontinuous ceramic fiber reinforced ceramics have demonstrated increased strenghtening both in flexure and impact. This investigation was limited to studying reinforcement of an alumina matrix with sapphire whisker fibers.

In an attempt to correlate the morphology of the fracture faces of the sapphire whisker reinforced ceramic composites with fabrication and composition parameters; two-stage replicas, cellulose acetate film—carbon film -30° chromium shadow, were prepared from the samples utilized for mechanical testing. The mode of fracture of the samples was generally intergranular as shown in Fig. 1. Trans-granular fracture of the samples was, however, observed and its occurrence became more frequent as firing time and whisker content were increased. Fig. 2 is a fractograph of a twenty percent 3B sapphire whisker-alumina composite which was hot-pressed and subsequently fired at 1315°C.
Interface Studies of Porcelain Enamel on Aluminum
Authors: Ballard D. B. , Gugeler A. L.
Published: June 2020

Aluminum and aluminum alloys can be coated with porcelain enamel slip which is fired at 1000°F for approximately 10 minutes. This produces a material with a surface layer (about 0.1 mm thick) which has the properties of porcelain and the basic mechanical properties of a light ductile metal. A problem termed spalling may arise after weathering or exposure to a corrosive salt solution, if the base metal is not chosen carefully or pretreatment of the metal is not correct. A typical failure of this type on a test panel is illustrated in Fig. 1. The spalling failure initiates at pin holes, scratches and edges, then spreads laterally by attack at the interface between the enamel and base metal. An electron fractograph at the edge of a circular spalled area on a test panel of an improperly pretreated 6061 alloy is shown in Fig. 2. The corroded metal is on the bottom and the porcelain on the top. The narrow band through the center is the fracture edge of the porcelain enamel adjacent to the interface.
Formation of Single Microcrystal of Colloidal Selenium
Authors: Chiang Y. S.
Published: June 2020

Single microcrystals of colloidal selenium have been grown by reducing 2 ml. 1% methanol solution of selenous acid (H2SeO3) with 2 ml. 1% methanol solution of hydroxylamine hydrochloride in the presence of 20 ml. chloroform at room temperature. After about forty hours, selenium microcrystals can be found among numerous amorphous polyhedral shaped particles. Similar selenium microcrystals can also be formed in the presence of ethyl acetate or trichloroethylene, but with considerable less efficiency.

The selenium microcrystals are usually present in the form of trigonal shaped platelets or aggregates of them as shown in Fig. 1. Most of the lamellar crystals are about 1000 to 2000 Å in thickness and several microns in width. The flaky habit surface is usually that of the (0001) plane of trigonal selenium (Fig. 2 and 3).