bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural improvements in melt-textured YBa2Cu3O7 bulk superconductors
Authors: Sabatini R.L. , Zhu Yimei , Wang Y.L. , Suenaga Masaki
Published: June 2020

In spite of its known high intragranular current density Jc, bulk YBa2Cu3O7(123) superconductors presently have a limited commercial viability due to their low current carrying capacities. Thus the problem with the bulk superconductors is widely attributed to its weak coupling at the grain boundaries. One possible solution, based on work by Jin and others, is to “melt texture” the sample so that grains align to provide a high current path through the material. But melt texturing produces other problems such as microcracking and shape distortion.

To investigate the problems associated with producing high Jc bulk superconductors from the melt texturing process, we have studied the effects of modifying composition and processing conditions of the samples and examined the resulting microstructure and electrical properties.
Possible flux pinning centers in YBa2Cu3O7-x
Authors: Kulik J. , Huang Z.J. , Bechtold J. , Xue Y.Y. , Hor P.H.
Published: June 2020

The critical current density Jc of a superconductor is one of its most important properties for the purposes of applications. Various investigators have made numerous attempts to increase the value of Jc in the high temperature superconductor YBa2Cu3O7-x (Y123) through the introduction of defects into the crystal structure. References 1, 2, and 3 provide a few examples of some of the more recent efforts. In general, defects of an appropriate size should act as flux pinning centers in the material.

We have attempted to increase Jc in Y123 samples both through bulk processing techniques and through irradiation by fast neutrons. In an attempt to correlate the microstructures of the materials with the superconducting properties we have studied the materials using TEM. Here, we report on results from two samples. The first is an Y123 sample prepared by the decomposition of YBa2Cu4O8 (Y124). The decomposition process results in Y123 material with a value of Jc which is enhanced by approximately a factor of 10 at low magnetic field at 77 K as compared with Y123 prepared by standard processes. The second sample is one which was irradiated with fast neutrons (> 0.1 MeV) to a fluence of 6.0 x 1017 cm-2. This sample also shows an increase in Jc.
Ordering in rare earth doped Bi2(Sr or Ca)3-xRxCu2O8+δ superconductors
Authors: Beesabathina D. P. , Nahm S. , Salamanca-Riba L. , Green S. M. , Jiang W. , Greene R. L.
Published: June 2020

The crystal structure of Bi2Sr2Can-1CunO2n+6+δ compounds with Tc's up to 115 K has been studied extensively. Bi2Sr2CaCu2O8+s (Bi2212) with Tc ≈ 90 K has modular layered structures in which Cu and O sheets, typical of all the high Tc superconductors, are separated by layers of alkaline earth cations, and interleaved with Bi2O2 layers. It has been reported that the structures are complicated by incommensurate modulations, cation disorder, layer stacking faults and other nonperiodic behavior which in turn may be related to the superconducting properties. In this work we use high resolution electron microscopy (HRTEM) to investigate the crystal structure, and defect structure of two families of related Bi2212 superconductors. Namely, 1) Bi2Ca3-xRxCu2O8+δ and 2) Bi2Ca3-xRxCu2O8+δ, where R is a rare earth element.
A new type of defect structure in 124-superconducting oxide revealed by HREM
Authors: Sharma R. , Ramakrishna B.L. , Thadhani N.N. , Hianes D. , Iqbal Z.
Published: June 2020

After materials with superconducting temperatures higher than liquid nitrogen have been prepared, more emphasis has been on increasing the current densities (Jc) of high Tc superconductors than finding new materials with higher transition temperatures. Different processing techniques i.e thin films, shock wave processing, neutron radiation etc. have been applied in order to increase Jc. Microstructural studies of compounds thus prepared have shown either a decrease in gram boundaries that act as weak-links or increase in defect structure that act as flux-pinning centers. We have studied shock wave synthesized Tl-Ba-Cu-O and shock wave processed Y-123 superconductors with somewhat different properties compared to those prepared by solid-state reaction. Here we report the defect structures observed in the shock-processed Y-124 superconductors.
Characterizing AEM sections: Ultramicrotomy ‘quality control’
Authors: Steele D. , Malis T.
Published: June 2020

The wide variety of modern materials (alloys, ceramics, composites, layered structures) and the strict demands of microanalytical techniques (energy dispersive and energy loss spectroscopies) has resulted in a growing use of mechanically-based techniques for preparation of AEM specimens. One of these techniques is ultramicrotomy or diamond knife sectioning, which is seeing increasing usage in the materials science community. A recent review of the field has pointed out a number of significant factors affecting section quality such as knife wear and uniformity when sectioning ‘hard’ materials. As materials ultramicrotomy diversifies and matures, more information is required concerning the detailed nature of such factors in order to understand the artifacts peculiar to the technique and ultimately produce sections of suitable AEM quality in a consistent fashion.
A sample preparation technique for cross-sectional AEM of thin films on hard materials
Authors: Ostreicher Kim , Sung Changmo
Published: June 2020

Hard materials such as tungsten carbides which contain ceramic protective coatings (from 30 nm to several microns in thickness) present unique electron-transparent sample preparation challenges for TEM observations. A cross-sectional sample would allow one to observe the coating, matrix and related interface between the two. Variations in the hardness as well as differences in the compositions of the coating and substrate make this preparation more difficult. Discs of the material cannot simply be core drilled out and mechanically or ion beam prepared since it is the surface or edge of the material containing the coating which must be retained. Ion milling also causes preferential removal of one phase in relation to others leaving a sample which is not uniformly thin or truly representative of the microstructure. A preparation technique used for many semiconductor materials involves gluing together pieces with surface layers or coatings thus forming a stack which can be further processed to yield thin, electron transparent specimens.
Angular lapping for preparation of electron-transparent areas of materials using a commercial grinding/polishing machine
Authors: Shaapur F. , Pan M. , Crozier P.
Published: June 2020

A single step mechanical procedure can produce thin sections of material samples with a tapered edge containing areas adequately thin for transmission electron microscopy (TEM). Essentially, a tapered section of a solid terminates with two intersecting planes which generate zero bulk thickness at the edge. It is conceivable that, extending from the edge inward into the bulk, the thickness remains below that required for electron transparency. It has been shown that this concept is feasible in practice and a variety of applications have been reported. Among the work published more recently, Benedict et al. have developed a wedge-grinding technique including the related hardware for preparation of specimens from microelectronic components. Desport and Bennett have built and used a precision machining system for this purpose. The wedge-shaped specimens are most useful when a) ion thinning is not practical, e.g., due the to preferential milling of one phase in a multi-phase material system, or b) the microscopy is to be performed in an extended one dimensional mapping mode.
Mechanism for radiation damage in borosilicate glasses
Authors: Dascomb S.D. , Howitt D.G.
Published: June 2020

Oxygen bubble formation has been observed in sodasilicate glasses during irradiation. Although the irradiation always produces a consistent microstructure of oxygen microbubbles and an amorphous phase decomposition, there is a substantial difference between the rate at which the damage occurs. When a sample has been previously gamma irradiated, the damage occurs at much greater rates when compared to in situ irradiation in the electron microscope. It has been suggested that it is not the radiation damage rate that is responsible for this behavior but rather the presence of an electric field

Figure 1 illustrates the microstructure found in a sodasilicate glasses showing the characteristic bubble formation on the perimeter of the area illuminated by the beam and the phase separation within the interior.
The Structural Basis of Synaptic Transmitter Release
Authors: Pfenninger Karl H.
Published: June 2020

For intercellular transfer of signals, neurons form long processes to contact and form junctions with selected target cells or specific parts thereof. At these sites, they release in a quantal fashion neurotransmitter substances which interact with the receptors of the target cells. Thus, synaptic ultrastructure bears the characteristics of a secreting cellular region combined with those of a junctional complex.

Synaptic junctional structure consists of a set of cytoplasmic and cleft (i.e., extracellular) elements which are formed by proteinaceous and (in the cleft) carbohydrate-bearing components anchored in the joined plasma membranes. The synaptic cleft is filled with two layers of material that can be stained with cytochemical techniques such as ethanolic phosphotungstic acid (E-PTA) and bismuth-iodide (BIUL; for review, see 1).
Investigations of the Relationship Between Acetylcholine Synthesis and the Recycling of Synaptic Vesicles
Authors: Benes Francine M. , Barrnett Russell J.
Published: June 2020

It is well established that synaptic vesicles fuse with the pre-synaptic membrane during stimulation, and are reformed during a period of rest. These events have been correlated with the depletion and resynthesis of stores of acetylcholine (Ach) in the frog neuromuscular junction. Thus, choline acetylase (ChAc) activity appears to be a key factor in the metabolism of the transmitter Ach pool. The present work inquires into the possible interrelationship of the above events; that is, whether the reformation of vesicles after depletion by stimulation is associated with the activity of ChAc. Therefore, a series of experiments on frog neuromuscular junctions were performed in which the data from biochemical analyses of acetylcholine synthesis and from the morphometric determination of vesicle numbers were compared.
The Influence of Antifertility Agents on the Fine Structure of the Male Reproductive Tract
Authors: Flickinger Charles J.
Published: June 2020

The effects of antifertility agents on the histology and fine structure of the male reproductive tract have been studied, with the objective of understanding the basis of the antifertility action. Certain agents were chosen for study as representatives of classes of compounds that affect the reproductive tract by different mechanisms. These include: 1) a progestin and progestin plus androgen, which are steroids that suppress gonadotropin release; and 2) cyproterone acetate, a representative of the antiandrogens, which are compounds that interfere with the action of testosterone on target cells.

The combination of a progestin and androgen is currently believed to show promise as a male contraceptive. The progestin is thought to reduce gonadotropin secretion and suppress spermatogenesis. However, the Leydig cells of the testis are also suppressed and their secretion of testosterone is diminished.
Alkaline Phosphatase Localization in Testicular Degeneration Induced by Epinephrine Treatment
Authors: Gravis Curtis J. , Chen I-li , Yates Robert D.
Published: June 2020

Young adult male Syrian hamsters (80-130g) were used in these studies. Six control animals received daily intraperitoneal injections of sterile saline (0.1 ml) for a period of ten days. Six experimental animals received daily intraperitoneal injections of the vasodilator papaverine (60 mg/kg) five minutes prior to an intraperitoneal injection of epinephrine (1.0 mg/kg) for 10 days. After treatment testes were fixed by retrograde perfusion into the abdominal aorta with 3% cacodylate buffered glutaraldehyde and then processed for electron microscopic localization of alkaline phosphatase. In control animals electron microscopic investigations (Fig. 1) demonstrated marked reactivity in the basal laminae of the seminiferous tubules and in both the internal and external basal laminae of the myoid cells.
Filaments Associated With the Human Erythrocyte Membrane: A Scanning Electron Microscope Study
Authors: Hainfeld J. F.
Published: June 2020

A reticulum of filaments covering the cytoplasmic surface of human erythrocyte membranes was visualized at a resolution of 50-100 Å using a scanning electron microscope. This network was visible in ghosts split or torn open to reveal their interior space; in Triton X-100 extracted ghost residues; and even in intact cells, where the contour of the outer surfaces appeared to reflect an underlying meshwork. In addition to filaments, annular figures and nodes were seen in the reticulum. Since the Triton X-100 extraction leaves insoluble a residue that is predominantly spectrin and actin, the residues observed may be assumed to be composed of these proteins. Also, since the reticulum seen inside ghosts appears morphologically similar to the Triton residue reticulum, it may be tentatively concluded that this, too, is made up of spectrin and actin.
Surface Coating of Germinal Apertures of Pollen and Evolution of Apertures
Authors: Rowley John R. , Skvarla John J.
Published: June 2020

Following meiosis of sporogenous cells in anthers of vascular plants the four male gametophytes, some in permanent diads or tetrads, become disassociated from the cell wall--vascular system translocation network typical for plant tissues. The highly specific and extensive plasma membrane surface coatings (glycocalyces) of these free cell surfaces guide deposition of sporopollenin in the exine (6), which because of its specific form and resistance is used in pollen analysis and other fields. During early development of the male gametophyte uptake and secretion probably occur more or less equally throughout the free cell surface, but after the exine is formed there are reasons for considering that germinal apertures may have a special, although not exclusive, role in nutritive transfer.
Structure of the “Core” Particles from 50S IS. coli Ribosomes Depleted by LiCl.
Authors: Spiess E. , Roth H.E. , Hellmann W. , Jenkins F. , Boublik M.
Published: June 2020

Involvement of ribosomes in protein synthesis is well established. Also substantial data about the roles of both ribosomal constituents, proteins and ribonucleic acids, in this process are known. However, the detailed mechanism of the function of ribosomes remains obscure, mainly because of our limited knowledge of the interactions and structural arrangement of ribosomal components.

One of the approaches to study ribosome structure involves progressive depletion of proteins and correlation of the protein-depleted ribonucleoprotein cores with function. High resolution electron microscopy has been applied for direct imaging of the changes in the fine structure of depleted ribosomes.
Acridine Orange Staining Reaction in Bone Marrow Colony Forming Units Incubated with Phytohaemagglutinin
Authors: Ahearn M. J. , Trujillo J. M. , Dicke K. A.
Published: June 2020

It has recently been demonstrated that bone marrow cells from acute leukemia patients in active disease will form colonies in vitro in soft agar if pre-incubated in phytohaemagglutinin (PHA). This finding is contrary to evidence obtained from the Robinson System of in vitro culture utilizing a leucocyte stimulating factor to promote significant colonies of marrow cells only from haematologically normal individuals.

In the present investigation the effects of the PHA incubation on human bone marrow cells from leukemia patients in the acute and remission phases of their disease, as well as normal controls, are studied utilizing Frenster's acridine orange reaction product to delineate the active extended euchromatic portion of the cell nucleus.
Structural Alterations of Lymphocytes and Macrophages by Tobacco Smoke Products
Authors: B. Silver , C. V. Jacob , G. Stelzer , J. H. Wallace
Published: June 2020

Previous work from these laboratories (Jacob,Stelzer,Wallace) has shown that a water soluble condensate (WSC) of tobacco smoke, prepared from experimental cigarettes by the Kentucky Tobacco and Health Research Institute, exerts profound immunosuppressive effects. Immunosuppression is demonstrable in intact C57B1/6 mice subsequent to WSC treatment, as well as in an in vitro antibody induction system when participating cells are obtained from WSC treated animals, or are treated with WSC in vitro. The present study was undertaken in an attempt to determine the nature of ultrastructural changes exhibited by immunoreactive cells subsequent to their exposure in vivo or in vitro to levels of WSC capable of modifying their biological activity. Consequently, populations of B lymphocytes, T lymphocytes, and macrophages have been isolated from WSC treated mice or, have been obtained from normal animals and exposed to non-toxic levels of WSC in vitro.
Fine Structure of Rat Extraocular Muscle in Myotonia Induced by 20,25- Diazacholesterol
Authors: Pachter Bruce R. , Davidowitz Jacob , Breinin Goodwin M.
Published: June 2020

Rats administered with 20,25-diazacholesterol manifest physiological and clinical signs characteristic of human myotonic dystrophy, i.e., prolonged contraction and bizarre electromyographic discharges which are not abolished by curare or peripheral nerve block, in association with prominent ptosis, cataract formation and testicular atrophy. The extraocular muscles (EOM) are prominently involved in human myotonic dystrophy but have not been studied on the electronmicroscopic (EM) level; the present study examined the EOM of rats with induced myotonia as a possibly suitable model of the human syndrome.

Wistar rats (125 gms.) were injected with 13mgAg of 20,25-diazacholesterol, daily for 2-3 weeks. These animals were perfused with 1% paraformaldehyde- 1% glutaraldehyde. The superior rectus muscle was dissected free and prepared by standard EM procedures, embedded whole in Epon 812 and serially sectioned at 15 microns.
Morphometric Underestimation of Narrow Interstitial Spaces
Authors: Loud Alden V. , Trubatch Janett
Published: June 2020

In morphometric measurements of the interstitial spaces surrounding cells, which are usually identified in microscopic sections with those areas that do not show any cellular structures, the volume fraction (VV) of interstitial space in tissue is equated with the area fraction (AA) of sections occupied by such clear regions between cells. Because of the random oblique orientation of its bounding cell membranes and cytoplasm, however, these narrow extended spaces are partially obscured, leading to an underestimate of their volume fraction. This effect is particularly evident in tissue from the neuropil as illustrated in Figure 1, in which many fine dendritic and axonal elements are separated by a complex meshwork of interstitial spaces.
The Application of Quantitative Stereology to the Study of Adenohypophyseal Cells
Authors: Poole Max C. , Mahesh V.B. , Costoff Allen
Published: June 2020

Quantitative stereology of liver parenchymal cells has previously been reported (1,2), but there have been few studies of morphometry applied to a heterogenous tissue (3). Due to the presence of several different cell types, it is difficult to study the synthesis and secretion of hormones in cells of the anterior pituitary by conventional biochemical means. In this study prolactin cells were analyzed using morphometry during different times of the rat estrous cycle, and were correlated with changing levels of prolactin in the serum and pituitary gland.

Vaginal smears of 60 day old Holtzman rats were monitored through three estrous cycles, and only four day cycling rats were used. Groups of six animals were decapitated at 4 P.M., 6 P.M., 10 P.M. and 12 midnight of proestrus and one half of the pituitary was processed for electron microscopy and the other half for assay.
Electron Microscopy and X-Ray Photoelectron Spectroscopy of Oxygen Plasmaetched Bacterial Spores and Cells
Authors: Thomas Richard S. , Millard Merle M. , Scherrer René
Published: June 2020

Low-temperature, oxygen plasma etching (OPE) is a useful technique in electron-microscopic (EM) morphological studies of mineral-containing organic polymers and biological structures. OPE gently and cleanly etches away the organic matrix at the surface of the specimen, leaving behind oxides and salts of exposed mineral elements. X-ray photoelectron spectroscopy (XPS) is widely used for macroscopic chemical analysis of the surfaces of polymers and inorganic specimens. The XPS signal originates from a surface depth of less than 100 Å. Combined application of the three techniques, OPE, EM and XPS to dispersible, macroscopic specimens which are microscopically homogeneous should allow correlation of fine structural features with surface and subsurface chemical composition. The present, preliminary study explores this possibility on bacterial spores and cells. Further details, and similar studies on tissue culture cells will be reported elsewhere.
Aspects of Endocytosis in the Ciliate Tetrahymena Pyriformis
Authors: L. J. Brenner  , D. G. Osborne  , B. L. Schumaker
Published: June 2020

The ciliate, Tetrahymena pyriformis, is an excellent cell for studying endocytic processes. It ingests particulate matter like bacteria and latex particles by way of the buccal apparatus. Soluble material entering by pinocytosis and the coalescing of pinocytic vacuoles to form larger vesicles also occurs. It is not uncommon to see autophagic vacuoles containing recognizable cytoplasmic structures like mitochondria. The visualization of the formation of a food vacuole in the cytopharyngeal region has not been accomplished. Some observations reported in this paper may cast additional light on this and other endocytic processes.

Static cultures of log phase cells of strain WH6 were generally used. Most of the preparations studied were of control animals suspended in dilute NaCl solution. Chance bacterial contaminants frequently served as valuable reference points.
Structure and Interaction of Protamine by Dark Field Electron Microscopy
Authors: Bazett-Jones D.P. , Ottensmeyer F.P.
Published: June 2020

It has been shown for some time that it is possible to obtain images of small unstained proteins, with a resolution of approximately 5Å using dark field electron microscopy (1,2). Applying this technique, we have observed a uniformity in size and shape of the 2-dimensional images of pure specimens of fish protamines (salmon, herring (clupeine, Y-l) and rainbow trout (Salmo irideus)). On the basis of these images, a model for the 3-dimensional structure of the fish protamines has been proposed (2).

The known amino acid sequences of fish protamines show stretches of positively charged arginines, separated by regions of neutral amino acids (3). The proposed model for protamine structure (2) consists of an irregular, right-handed helix with the segments of adjacent arginines forming the loops of the coil.
Scanning Electron Microscopy of Normal and Dehydrated Keratinized Epithelia
Authors: Uptgraft G.
Published: June 2020

Recent Scanning Electron Microscope studies of the surface characteristics of keratinized epithelia indicate that considerable variation exists in the dimensions and distribution of microvilli and surface folding (1, 2) . These surface structures have been implicated in the cell to cell contact, which in the case of the stratum corneum, are partially responsible for its structural integrity. As these dimensional characteristics seem to vary, depending on the state of hydration and thickness of the stratum corneum, the present investigation was conducted to determine any systematic differences between the dimensions and distribution of microvilli in thick and thin stratum corneum in both normal and dry skin.
Evidence for a Unique Intercellular Communication in the Thymic Cortical Capillaries of the Mouse
Authors: DAVENPORT WM. D.
Published: June 2020

Thymic tissue from 24-56 day old mice was examined with respect to the ultrastructure of the endothelial cell junctions of the cortical capillaries. These junctions have been described as being desmosomes, desmosome-like, or tight junctions. Data obtained from the present study suggest that these junctions are unique.

The morphologically mature thymic cortical capillary (TCC) endothelial cell junction in the present study is considered to be a pentalaminar structure consisting of: (1) a cytoplasmic density, 800-1500 Å in length and 200-500 Å in width, against the inner leaflet of the unit membrane of the endothelial cell process; (2) a space or area of decreased density adjacent to the outer leaflet of the unit membrane of the same endothelial cell process;
The Effect of Viewing Angle on the Appearance of Trilaminar Structures of Desmosomes
Authors: Neal Richard J. , Paulson Joy L.
Published: June 2020

Examination of desmosomes in the spinous region of the epidermis of human skin reveals that the trilaminar structure, usually associated with desmosomes, is not always observed. Desmosomes were examined utilizing serial sectioning and tilting techniques to determine if the trilaminar structure is consistant throughout the desmosome. Concomitantly, information concerning the size and shape of the spinous layer desmosomes was obtained from examination of serial sections that completely transversed many desmosomes.

Figures 1 and 2 are from a serial section series and demonstrate that the trilaminar structure of desmosomes (Dl and D2) can be observed in one section (figure 1) and not observed in an adjacent section (figure 2). Figure 3 thru Figure 6 are micrographs of the same section seen in Figure 2. These micrographs show the effect on the appearance of desmosomes Dl and D2 when they have been tilted about their longitudinal axes 5, 10, 20, and 30 degrees, respectively.
The Use of Scanning Electron Microscopy to Study Hepatic Pathology
Authors: Nopanitaya Waykin , Grisham Joe W. , Lesesne Henry R.
Published: June 2020

Three dimensional views of the surfaces of tissue components of normal liver have recently been described by investigators from several laboratories, including this one (1-2). These studies have provided new insights into the comparative surface ultrastructure of hepatocytes, sinusoidal endothelial cells, Kupffer cells, bile ducts, and fat storing cells, and into the disposition of collagen fibers in normal livers. Results of SEM studies of normal liver promise to allow useful correlations between hepatic ultrastructure and physiology to be made. SEM has also been used to elucidate some aspects of cholestasis following extrahepatic biliary obstruction or administration of cholestatic bile acids. Preliminary studies by us on experimental and human hepatic diseases have indicated that SEM is also helpful for the examination of lesions in which there are abnormalities in the conformation of hepatic plates (especially the periportal limiting plate), bile ducts and canaliculi, vessels (including the lining endothelium of sinusoids), and the disposition of connective tissue.
Microvillar Ultrastructural Alterations in the Human Duodenal Mucosa - a SEM-and TEM Study
Authors: Perrins N.M. , Turner J.N. , Brown M.R. , Lillibridge C.B. , Stowe S.P.
Published: June 2020

Biopsies from the second and third portions of the human duodenum have been studied by both SEM and TEM. The biopsies taken for SEM were immediately placed in a rinse solution of Millonigs buffer and 1% urea for 30 minutes with mild agitation at 4°C. The specimen was then fixed in 2% gluteraldehyde in Millonigs buffer overnight at 4°C. Postfixation was OsO4 for 30 minutes at 4°C. The specimen was then examined under a dissecting microscope, and if still covered with mucus, was rinsed for 1 minute in 1% HC1 with mild agitation. The sample was then dehydrated through a graded ethanol series, and critically point dried from CO2. The transmission samples were immediately fixed in 2% gluteraldehyde, postfixed in OSO4, and processed in the usual way.
Effect of Thyroxine and Estrogens on Collagen Synthesis in Rats: A Transmission and Scanning Electron Microscopy Study
Authors: Lupulescu A. , Habowsky J.E. , Milkintas J. , Birmingham D.
Published: June 2020

Recent light and electron microscopic studies showed that corticosteroids and testosterone induced changes in the structure of fibroblasts and collagen synthesis. Our previous investigations demonstrate that also calcitonin significantly interferes with collagen synthesis and fibroblast growth in wounded rabbits.Conflicting findings were reported by using biochemical and light microscopic studies following estrogens and thyroxine administration. This report concerns some investigations with regard to the role of estradiol and thyroxine on collagen synthesis in rats.

Adult male rats were used in these experiments. They were divided in three groups of 10 rats each. A) Thyroxine-treated rats: each rat received intramuscularly (im) 100 μg thyroxine (Synthroid), every other day, for one month. B) Estrogen-treated rats: each rat received 500 μg estradiol dipropionate, every other day, for one month. C) Controls, received only the diluent.
Electron Microscopic Analysis of Myonecrosis Induced by a Pure Component Isolated From Rattlesnake Venom
Authors: Ownby Charlotte L. , Cameron David , T. Tu Anthony
Published: June 2020

In the United States the major health problem resulting from snakebite poisoning is local tissue damage, i.e. hemorrhage and myonecrosis. Since commercial antivenin does not usually prevent such damage to tissue, a more effective treatment of snakebite-induced myonecrosis is needed. To aid in the development of such a treatment the pathogenesis of myonecrosis induced by a pure component of rattlesnake venom was studied at the electron microscopic level.

The pure component, a small (4,300 mol. wt.), basic (isoelectric point of 9.6) protein, was isolated from crude prairie rattlesnake (Crotalus viridis viridis) venom by gel filtration (Sephadex G-50) followed by cation exchange chromatography (Sephadex C-25), and shown to be pure by electrophoresis. Selection of the myotoxic component was based on light microscopic observations of injected mouse muscle.
Scanning Electron Microscopy of Chondrocytes from Fracture Callus Cartilage
Authors: Jafri A.M. , Ketenjian A.Y. , Arsenis C.
Published: June 2020

There is little information available in the literature on scanning electron microscopy of cartilage tissue. Most of the available information deals with articular cartilage (1,2). More specifically, there are no studies reported on the scanning electron microscopy of differentiating callus cartilage. This preliminary report is part of our studies on the differentiation and eventual calcification of rabbit callus cartilage.

Closed fractures were produced in the tibias of white rabbits by acute angulation. Seven days after fracture, the callus was dissected into homogenous cartilage sections corresponding to the fibrous, hypertrophic and calcified cartilage types of the epiphyseal plate (3). The cartilage specimens were dehydrated by ascending acetone series or freeze-dried. Some acetone dried specimens were freeze-dried while others were critical point dried. All specimens were mounted on Cambridge specimen stubs and coated with carbon and gold.
The Significance of Contraction Bands in the Normal Heart
Authors: Adomian Gerald E. , Laks Michael M. , Swan H.J.C.
Published: June 2020

Contraction bands are a cardiac histological alteration found in many experimental and pathological conditions--such as ischemia, cardiomyopathies, electric shock, hemorrhagic shock, catecholamine infusion, and open heart surgery. Of importance, contraction bands have also been considered by some investigators as an artifact of preparation. We have frequently observed contraction bands in normal dog heart tissue obtained by endocardial biopsy. In order to study the determinants for the production of contraction bands, we utilized the rat, a less expensive animal in order to more fully investigate the various possible mechanisms operational. The aim of the present study was to investigate the determinants of contraction band formation in normal hearts.
Fine Structure of the Elastic Fibers and the Elastin Crystalloids by Means of Tannic Acid Fixation Method
Authors: Mizuhira V. , Futaesaku Y. , Nakamura H.
Published: June 2020

It is well known that the elastic fibers do not stain well with conventional electron fixation and staining methods. However some investigators have tried to demonstrate elastic fibers as a stained structure under the electron microscope. Greenlee et al.(1966) and Ouintarelli et al.(1973) reported a phosphotaungstic acid staining method for elastic fibers; Albert (1970 & 1971) reported his results using a metalic tetraphenylprophine staining method.

In the contrast to these staining methods for elastic fibers, Mizuhira et al (1971,'72, ‘75) have succeeded in demonstrating elastic fibers very clearly using an improved fixation method for proteins with glutaraldehyde containing tannic acid, followed by the osmium tetraoxide method.

This new fixation method is very simple. Aorta, ear cartilage, intestine or skin are fixed with 2.5 % glutaraldehyde, containing 0.5 % to 4 % tannic acid buffered with veronal acetate or phosphate at pH 6.8 to 7.2 for 1.5 hrs to overnight.
Electron Probe Analysis of Vertebrate Smooth Muscle: Distribution of Ca and Ci
Authors: Somlyo Avril V. , Shuman H. , Somlyo A.P.
Published: June 2020

This is a preliminary report of electron probe analysis of rabbit portal-anterior mesenteric vein (PAMV) smooth muscle cryosectioned without fixation or cryoprotection. The instrumentation and method of electron probe quantitation used (1) and our initial results with cardiac (2) and skeletal (3) muscle have been presented elsewhere.

In preparations depolarized with high K (K2SO4) solution, significant calcium peaks were detected over the sarcoplasmic reticulum (Fig 1 and 2) and the continuous perinuclear space. In some of the fibers there were also significant (up to 200 mM/kg dry wt) calcium peaks over the mitochondria. However, in smooth muscle that was not depolarized, high mitochondrial Ca was found in fibers that also contained elevated Na and low K (Fig 3). Therefore, the possibility that these Ca-loaded mitochondria are indicative of cell damage remains to be ruled out.
Quantitation in thin Sections Within the Electron Microscope
Authors: Edie J.
Published: June 2020

In TEM image formation, the observed contrast variations within thin sections result from differential electron scattering within microregions of varying mass thickness. It is possible to utilize these electron scattering properties to obtain objective information regarding various specimen parameters (1, 2, 3).

A pragmatic, empirical approach is described which enables a microscopist to perform physical measurements of thickness of thin sections and estimates of local mass, volume, density and, possibly, molecular configurations within thin sections directly in the microscope. A Faraday cage monitors the transmitted electron beam and permits measurements of electron beam intensities.
Stem Examination of a Protein
Authors: Hainfeld J. , Cooley J.
Published: June 2020

Glyceraldehyde-3-phosphate dehydrogenase (G3PD) was viewed by darkfield microscopy in the STEM using several specimen preparations including the use of negative stain, positive stains and no stain. Some of the resultant images have been subsequently compared with projections of the molecule computed from atomic coordinates (coordinates provided by M. G. Rossmann, Purdue University). G3PD is a glycolytic enzyme of molecular weight approximately 140,000, exists as a tetramer and is approximately 75 Å in diameter.

Fig. 1 shows a negatively stained protein on the left compared to a computed, projected view of the protein on the right. The stain used was methyl amine tungstate. 5-10 Å detail is visible in micrographs taken with this type of preparation. 10 Å detail seems to reproducibly correspond to the known structure. A 5 Å strand, presumably part of the polypeptide from the unfixed protein, is visible in Fig. 2.
Quantitative Energy-Dispersive Analysis
Authors: Reed S.J.B.
Published: June 2020

INTRODUCTION. Quantitative analysis is possible with an E.D. system, provided its performance is adequate (stability especially). Such a system may be fitted to an electron probe, SEM, TEM, or STEM and used for the analysis of either thick or thin specimens, of which the former are considered primarily here, though in many respects the procedures discussed are equally applicable to thin specimens. Elements in the range Z = 11-30 are primarily of interest (i.e. those with K peaks in the energy range 1-10 keV), though heavy elements with L or M peaks in this energy range can be treated by the methods discussed as well.

PEAK IDENTIFICATION. Often the analyst knows the elements present in the specimen. If not,a procedure for identifying peaks in the recorded spectrum is necessary. Various mathematical techniques are available for this purpose (e.g. cross-correlation with a gaussian).
High Resolution Sem Fractography of Te-Embrittled Hastelloy-N
Authors: Braski D. N.
Published: June 2020

Hastelloy-N (16%Mo-7%Cr-4%Fe-0.55%Mn-0.06%C-bal Ni) has long been a leading candidate material for a molten salt reactor. However, it was recently discovered that small amounts of Te, created by the fission process, caused grain boundary embrittlement in the structural material. Consequently, an alloy development program at this laboratory has directed considerable efforts towards modification of Hastelloy-N to improve its resistance to Te embrittlement and still retain excellent resistance to radiation damage. In this investigation, a JEOL 100C TEM with an energy dispersive x-ray spectrometer (EDX) and high resolution (50 Å) SEM attachments have been used to characterize the grain boundary surfaces of various Hastelloy-N alloys embrittled by Te.

Samples of Hastelloy-N were exposed to the tellurium source, Cr3Te4, in a molten salt (LiF + BeF2 + ThF4) or to the vapor above Cr3Te4 in a closed quartz system. All corrosion tests were at 700°C. The samples were subsequently tensile tested to failure at room temperature.
Study of Diffuse Scattering by Means of High Resolution Structure Images
Authors: Iijima Sumio , Anstis G. R.
Published: June 2020

Disorders in crystals with relatively simple structures which gave diffuse scattering have been extensively studied by X-ray or neutron diffraction methods. All these investigations were based on traditional diffraction methods and observations were made in reciprocal space (note observable diffraction intensities can be considered only in terms of interatomic vectors) and therefore the results obtained there leaves considerable ambiguity, particularly when we try to derive an actual model of the disordered crystals. A solution of this problem will be given only by knowing all atom positions in an assembly of atoms and for this case the observable diffracted intensity is given by

where (xi,yi) and (xj,yj) represent position vectors of the i th and j th atoms with scattering factors fi and fj from an arbitrary origin. On the other hand, a crystal containing imperfections can be defined by
Determination of the Signal and Noise Power Spectra for Wiener Filtering
Authors: Frank J.
Published: June 2020

Object restoration from bright field electron micrographs by Wiener filtering has been attempted by several authors (1-4). The linear filtering approach implies that the usual weak phase object assumption is made. In the notation used by Welton and Harris (3), the filter function has the form

where the power spectra of noise and object, N2(k) and S2(k) and the instrumental transfer function P(k) have to be obtained from measurements. The object power spectrum can be estimated from the atomic scattering factor of the dominating atomic species (3) , from electron diffraction measurements (5), or from the measured image power spectrum
Absolute Structure Determination using Electron Microscopy
Authors: Van der Biest O.
Published: June 2020

When the symmetry operations, which constitute the space group of a structure, do not include an inversion or a reflection operation, then the structure can exist in two forms, a right-handed and a left-handed one, called enantiomorphs. The presence of the two enantiomorphs coexisting within a sample can be verified in the electron microscope by imaging in dark field in a multi-beam orientation, with the electron beam parallel with a zone axis, along which the crystal does not show a center of symmetry in projection (1). One takes advantage here of violations in Friedel's Law (2), which may cause a difference in background intensity between the two structures. An example is shown in Fig. 1, where an inversion boundary runs through a thick wedge-shaped crystal of lithium ferrite. Ordered lithium ferrite may occur in two enantiomorphic forms P43 32 (right-handed screw axis), and P41 32 (left-handed screw axis). In this paper it will be shown that it is possible to determine uniquely the configuration of the structure using the results of the dynamical theory.
Specimen Charging: Effect on Beam Voltage
Authors: McMillan W. R. , Russ J. C.
Published: June 2020

Users of electron column instruments have long known of the mischievous results of charging of non-conductive specimens. The consequences can range from slight image degradation to complete chaos, and in the case of reflection electron diffraction sometimes produces images of expanding and collapsing bubbles instead of steady concentric rings.

The cure for this trouble has usually been to vacuum coat the specimen with a conductive layer: carbon, gold, and to a limited degree, fine graphite spray-coated on the surface (1,2). Charge neutralizing with alpha-emitting isotopes or electron guns where a general spray of electrons with a few hundred volts of energy is aimed at the entire specimen also have been used to allow incipient charging to leak off to ground.
Observations of Surface Diffusion at the Atomic Level by Means of Microcinematography in the Stem
Authors: Isaacson M. S. , Kopf D. , Parker N. W. , Utlaut M.
Published: June 2020

We have previously indicated the potential application of the STEM for studying surface phenomena on an atomic scale and noted that direct measurements of atom motion in the STEM could be of use in obtaining an improved understanding of a variety of surface processes. In this paper we would like to present some further observations concerning the motion of heavy atom containing molecules on thin carbon substrates due to thermal diffusion.

A typical example of heavy atom containing molecules migrating on a carbon substrate is shown in Fig. 1. The specimen is uranylchloride molecules on an ∼ 20 Å thick carbon film. The dark field micrographs have been taken with 17 second exposures. The beam is not irradiating the field of view between exposures. In this set of micrographs it appears that the uranium atom “spot” is migrating towards the large cluster in the lower portion of the field.
The Microstructure of Fe-Cr-Co-Nb-Al Permanent Magnet
Authors: Okada M. , Homma M. , Kaneko H. , Thomas G.
Published: June 2020

Fe-Cr-Co permanent magnet alloys are known to be commercially potential magnets, the energy products of which are comparable to those of Alnico V, with good ductility (1). It was recently found that the addition of Nb and A1 to the Fe-Cr-Co alloy system facilitated heat treatments to produce good magnetic properties (2).

The present paper describes the microstructure of an Fe-Cr-Co-Nb-Al permanent magnet. An effect of a thermomagnetic treatment on the microstructures is also discussed since a thermomagnetic treatment plays an important role in producing good magnetic properties in this alloy.

The magnetic hardening of the alloy is performed by tempering after solution treatment. Upon tempering, a a phase spinodally decomposes into two phases, an iron-rich phase (α1) and a chromium rich phase (α2) (1).

The microstructure shown in Fig. 1 results after the Fe-28wt%Cr-15wt%Co-lwt%Nb alloy is tempered at 640°C for 20 min. The decomposition process appears to be isotropic in the alloy. No satellites are observed in the corresponding diffraction pattern.
Electron Microscopy of Lunar Dunite 72417
Authors: Lally J.S. , Nord G.L. , Christie J.M. , Heuer A.H.
Published: June 2020

Lunar dunite 72417 is a brecciated dunite thought to be an original cumulate from the primary lunar differentiation and crustal formation. The complex olivine deformation structures and fine matrix material have been studied by high voltage transmission electron microscopy to augment geochemical and petrographic studies of other researchers. Our specimen, 72417,9009 is predominantly olivine "clasts" of variable size, set in a "matrix," also of olivine. The clasts and matrix of this breccia are essentially distinguishable only by size. Minor orthopyroxene, plagioclase and metal are also present. The angular "clasts" (largest is 0.3 mm) contain planar boundaries with misorientations of a few degrees (unlike boundaries in olivine tectonites). The finer-grained matrix has a few percent porosity and shows no optical evidence of recrystallization.

Substructures in Large Clasts. Several large clasts were examined and show a variable subgrain structure (Fig. la); smaller subgrains tend to be equiaxed and μlpm in size, while the larger subgrains are elongate and up to lOum long.
Analysis of Microgram Tungsten Carbide-Cobalt Cemented Carbides
Authors: Emma T.A.
Published: June 2020

When small quantities of a grain growth inhibitor are added to starting powders containing submicron WC and Co, the sintered product is a high strength, high hardness alloy. The microstructure of the carbide is quite similar to that of the macrograin variety. For the purposes of this study WC with 10-20% Co alloys containing small amounts of a grain growth inhibitor were examined with the electron microscope to determine grain size and shape, general composition, identification of possible undesirable species, and the disposition of the grain growth inhibitor.

During the initial stages of the investigation, fractured surfaces were examined using an RCA-3F microscope converted to operate as a high resolution diffraction instrument with 50 cm camera. Reflection patterns from fractured surfaces showed that the major phase was cobalt with a weaker pattern from WC, indicating that fracture took place inside the cobalt cement. These same surfaces were then treated electrolytically in concentrated sulfuric acid at a temperature in the range between 3 and 8°C to remove the cobalt binder.