bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copper-Beryllium Microstructures
Authors: Tanner Lee E. , Laughlin David E. 
Published: June 2020

Recently, the late R. Shiromizu carried out studies to establish the limits of metastability in the Cu-Be system. Con-currently, we engaged in parallel research, but with a broader emphasis on the microstructures concomitant with quenching, aging and reversion. A complete report covering 0.16 to 2.1 wt.% Be will be published elsewhere; certain unique structures are presented below.Alloys of >0.8 wt.% Be quenched from the α (f.c.c.) region exhibit weak {110} tweed strain contrast. Direct lattice imaging did not detect discrete particles in this condition, whereas rather high densities of {100} G.P. Zone plates in regular stairstep array were revealed after aging at temperatures well below the G.P.Z. solvus.
The Effect of Deformation Twins on the Microhardness in a Two-Phase Alloy Steel
Authors: Staudhammer K.P. , Murr L.E. 
Published: June 2020

The close correlation of strength properties with twin density in 304 stainless steel and manganese steel, has suggested indirectly that twin boundaries act as significant hardening mechanisms by acting as dislocation barriers. The presence of twins can be regarded as a grain-size refinement which can be viewed in terms of the Hall-Petch relation as producing an increase in the flow stress.In the present study, 60 mil thick sheets of Uniloy 326, having a residual grain size of 1 to 2 μ were explosively shock loaded. The shock loading was performed in sandwich assemblies containing 304 and 316 stainless steels as reference materials utilizing techniques previously described.
An Analytical Scanning Transmission Electron Microscope
Authors: von Harrach H. , Lyman C.E. , Walker A.R. , Joy D.C. , Booker G.R. 
Published: June 2020

A scanning transmission electron microscope (STEM) with a field emission gun has been developed for quantitative microanalysis. The high brightness source combined with X-ray analysis, electron diffraction and electron energy loss analysis provides a technique of microanalysis from regions of thin specimens as small as a few hundred angstroms.The electron optical lay-out of this microscope is shown in Figure 1. A triode field-emission gun is mounted in a U HV chamber with mu-metal walls for screening. The gun which can be operated at up to 100kV provides a virtual source; the position of this source is largely independent of the ratio of the acceleration voltage to extraction voltage.
A Study of Shock-Induced Point Defect Concentrations in Molybdenum by Transmission Electron and Field-Ion Microscopy
Authors: Morales Albert A. , Murr L. E. , Inal O. T. 
Published: June 2020

The passage of a shock wave through a metal is particularly conducive to the production of point defects in the form of vacancies behind the shock front. Vacancies in the metal can be considered a form of relief for the high stresses associated with the shock wave. The amount of data covering the effect of high strain rates on lattice defects (vacancies) is small. Although previous research work has supported the existence of vacancies in shock loaded metals, vacancies have not actually been observed, nor have the concentrations of vacancies or vacancy clusters been studied quantitatively in relation to shock deformation.In the present investigation, annealed molybdenum wires (3 mil diameter)(1250°C for 10 min. in high vacuum) and molybdenum foils (1 mil thick)(1250°C for 15 hrs. in high vacuum) were prepared and placed in sandwich assemblies for shock loading.
Imaging of Amorphous Objects by Tilted Beam Bright Field Illumination
Authors: Goldfarb W. , Krakow W. , Ast D. , Siegel B. 
Published: June 2020

Bright field tilted beam illumination is commonly used to demonstrate the resolution of a transmission electron microscope by forming lattice fringes.The unscattered and diffracted beams are symmetrically positioned on either side of the optic axis so that the spherical, defocus and chromatic abberations will cancel. The cancellation of chromatic aberration is particularly important. However, the balancing of aberration occurs not only for the one diffraction direction across the axis from the unscattered beam but for an entire hollow cone of scattering vectors centered on the microscope axis and passing through the unscattered beam. This hollow cone projects as a circle in the back focal plane (BFP) of the microscope with zero net aberrations for one sideband of the scattering. Because the image amplitude is squared to form the image intensity, the single ring of cancelled aberrations in the BFP corresponds to a symmetrical pair of rings in the spatial power spectra of the micrograph. These ring pairs show up strongly in the experimental diffractograms, Figures 1, 3 and 4.
Computer-Aided Indexing and Simulation of Transmission Electron Diffraction Patterns
Authors: Rao Prakash , Goehner R. P. 
Published: June 2020

The process of indexing electron diffraction patterns is well established and reasonably straightforward. However, in the more complicated crystal systems (e.g. hexagonal, rhombohedral, orthorhombic and monoclinic), indexing and orientation determination is not always simple. In order to considerably ease the tedium of routinely indexing such electron diffraction patterns, automation of the procedure has been carried out in our laboratory by the use of two computer programs written in conversational Fortran.Simplified flow diagrams of the two programs are shown in Figure 1. The first program (Figure 1a) indexes diffraction spots whose x and y coordinates are obtained from an experimental pattern and supplied, along with crystal structure, lattice constants, space group restrictions, camera constant, and the position and angle errors allowable.
The Wet Replication Technique
Authors: Parsons Donald F. , Basu Samarendra 
Published: June 2020

This report explains the physical aspects of the wet replication technique using a differentially pumped hydration chamber. These relate to the flow of evaporating gases through saturated water vapor, to selecting an evaporant material andfinally, to the shape replicating ability of the technique.Fig. 1 explains how the present method of wet replication differs in principle from conventional replication in high vacuum. In conventional dry replication, the replica material is evaporated on top of the specimen at normal incidence. This may either preceed or follow angular shadowing by a heavy metal. In the present method the wet specimen inside the hydration chamber is first replicated by SiO vapor at normal incidence from the bottom, and then shadowed with pt-c at 30°-35° angle as shown on the right on Fig. 1, for dry replication.
Cathodoluminescence-Mode Scanning Electron Microscopy of GaAs Alloys and Diodes
Authors: Levin E. R. , Ettenberg M. 
Published: June 2020

Cathodoluminescence (CL)-mode scanning electron microscopy studies were made on n-type GaAs substrate crystals, and on liquid (LPE)- and vapor-phase-epitaxial (VPE) GaAs. The observations were carried out in a Stereoscan S4-10 equipped with a separate CL detector and signal processing channel. Broad-band detection was employed, with the CL radiation from the specimen focused directly onto a photomultiplier (RCA type 7102) with S-l spectral response. The CL was excited by 30 kV electrons, with beam currents typically about 10 nanoamperes.Figure 1 shows a low dislocation-density (˜103/cm2) substrate crystal. The CL image contains only heavy horizontal striations, which may be attributed to varying concentrations of dopant formed during growth, and a few contrast effects related to surface features (cf., emissive-mode (SE) image).The high dislocation-density (˜105/cm2) GaAs substrate in Figure 2 shows in addition a distribution of discrete dark spots and short line segments, identified as emerging dislocations: Dislocation etching of the specimen revealed a distribution and density of dislocations comparable to the CL-image dark spots.
Three-Dimensional Structure Reconstruction by High Voltage Electron Microscopy of Biological Specimens
Authors: Peachey Lee D. 
Published: June 2020

A major advantage of the high voltage electron microscope (HVEM, accelerating voltage 1000 kV) is its ability to produce high quality images of slices of enbedded biological tissue or whole mounts of cells 1 μm or greater in thickness. Several workers have been trying to exploit this feature in studies of cell structures using the HVEM facility at the University of Colorado. When the right combination of thickness and contrast has been obtained, the resulting micrographs can be quite remarkable both for the quantity of information they contain and for the directness and clarity with which the three-dimensional information can be seen.For purposes of discussion, one can group the kinds of biological specimens and HVEM approaches to their study into three classes. First there are isolated cells or cell parts that can be fixed, mounted directly on support films, dried by the critical point or other appropriate method, and examined immediately without embedding or other treatment.
Autophagy Involves the Golgi Complex in a Two Step Process
Authors: Locke M. , Sykes A.K. 
Published: June 2020

The role of the Golgi complex as a distributing center for membranes and their contents has been studied by observing the origin of the membranes and lytic enzymes involved in autophagy. Friend's hot osmium staining method implicates the outer region of the Golgi complex as the source of the isolation membranes that sequester organelles in preparation for their destruction in autophagic vacuoles. The localization of acid phosphatase suggests that the inner secretory region of the Golgi complex is the source of the lytic enzymes carried to autophagic vacuoles by primary lysosomes.In addition to packaging material for secretory vesicles to make blood proteins, the Golgi complex (GC) has two separate roles in the organelle destruction which takes place when insect fat body cells change their activities during metamorphosis from the larva to the pupa. The process by which organelles are sequestered from the rest of the cell is temporally and spatially distinct from the addition of lytic enzymes.
Cytomegalovirus in Wild Mice
Authors: Rongey R. , Officer J.E. , Estes J.D. , Coffey G. , Gardner M.B. 
Published: June 2020

The inadvertant dissemination of otherwise latent or chronic herpes virus, especially cytomegalovirus (CMV), is an important consideration in humans given immunosuppressive treatment for renal or cardiac transplantation. It is desirable to have an animal model of chronic CMV infection that does not require experimental virus inoculation. Laboratory mice are unsuitable in this regard since they have a low prevalence (2-3%) of naturally occurring chronic CMV infection. However, chronic CMV infection with shedding of virus in saliva is apparently ubiquitous in wild mice (Mus musculus), suggesting that feral mice might be an appropriate model for studying the effects of immunosuppression upon natural CMV infection. We have found that wild mice immunosuppressed with antithymocytic sera (ATS) show a high incidence of disseminated virulent CMV infection.We confirmed the presence of chronic indolent subclinical CMV infection in high prevalence in healthy wild mice.
Studies of Epstein-Barr Virus Antigens Using Immunoperoxidase and Immunofluorescence Techniques
Authors: Stephens R. , Traul K. , Woolf D. , Gaudreau P. 
Published: June 2020

A number of antigens have been found associated with persistent EBV infections of lymphoblastoid cells. Identification and localization of these antigens were principally by immunofluorescence (IF) techniques using sera from patients with nasopharyngeal carcinoma (NPC), Burkitt lymphoma (BL), and infectious mononucleosis (IM). Our study was mainly with three of the EBV related antigens, a) virus capsid antigen (VCA), b) membrane antigen (MA), and c) early antigens (EA) using immunoperoxidase (IP) techniques with electron microscopy (EM) to elucidate the sites of reactivity with EBV and EBV infected cells.Prior to labeling with horseradish peroxidase (HRP), sera from NPC, IM, and BL cases were characterized for various reactivities by the indirect IF technique. Modifications of the direct IP procedure described by Shabo and the indirect IP procedure of Leduc were made to enhance penetration of the cells and preservation of antigen reactivity.
Stereo Electron Microscopy of Freeze-Fractured Cells Reveals the Three-Dimensional Continuity of Tobacco Mosaic Virus Crystals
Authors: Steere Russell L. , Erbe Eric F. 
Published: June 2020

The large hexagonal crystals which develop in cells of some plants infected with tobacco mosaic virus (TMV) have been shown to consist of ordered arrays of TMV virions. The virions of one layer are parallel to each other but usually tilted with respect to adjacent layers within the crystal to form a "herringbone" pattern if cut or fractured in a certain plane. The hexagonal outline of crystals containing numerous layers leads one to suspect that these are true three-dimensional crystals with a specific orientation of virions, not only within each layer but also between adjacent layers.Recent improvements in freeze-fracture techniques made it practical to reinvestigate these crystals. Epidermal strips from tobacco plants systemically infected with the common strain of TMV were placed in a gradient consisting of 0 to 25% sucrose and 0 to 25% glycerol in 0.2 M phosphate buffer of pH 7.
Skin Vascular Ultrastructure During Thermal Injury, Hypertrophic Scarring and its Resolution
Authors: Kischer C. W. 
Published: June 2020

The usual result of deep thermal injury of the skin in children is hypertrophic scarring. The dynamics of revascularization have been implicated as integral to development and resolution of hypertrophic scarring. Thus, special attention is being directed toward examining vessels at different stages after injury.In vessels from normal skin endothelial cells do not contain many organelles; Golgi membranes are sometimes observed, a few mitochondria and occasional profiles of rough endoplasmic reticulum. Pinocytic vesicles are present on both tissue and blood side of the endothelial cells and in the perivascular satellite cells. Infrequently multivesicular bodies are observed. A thin basement membrane underlies endothelial cells and their satellites (Fig. 1).In the post-injury granulation tissue pinocytic vesicles and multivesicular bodies are seldom seen. The endothelial cells contain a marked increase in rough endoplasmic reticulum, often dilated, and intracytoplasmic filaments (Fig. 2).
Ultrastructural Features of Normal and Diseased Hair Revealed by Ion Beam Etching and Freeze Fracture
Authors: Spector M. , Brown A. C. 
Published: June 2020

Ion beam etching and freeze fracture techniques were utilized in conjunction with scanning electron microscopy to study the ultrastructure of normal and diseased human hair. Topographical differences in the cuticular scale of normal and diseased hair were demonstrated in previous scanning electron microscope studies. In the present study, ion beam etching and freeze fracture techniques were utilized to reveal subsurface ultrastructural features of the cuticle and cortex.Samples of normal and diseased hair including monilethrix, pili torti, pili annulati, and hidrotic ectodermal dysplasia were cut from areas near the base of the hair. In preparation for ion beam etching, untreated hairs were mounted on conducting tape on a conducting silicon substrate. The hairs were ion beam etched by an 18 ky argon ion beam (5μA ion current) from an ETEC ion beam etching device. The ion beam was oriented perpendicular to the substrate. The specimen remained stationary in the beam for exposures of 6 to 8 minutes.
The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice
Authors: Johnson J.E. 
Published: June 2020

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).
Formation of Centrioles in Some Endocrine Adenomas
Authors: Horvath E. , Kovacs K. 
Published: June 2020

Centrioles, known to play a fundamental role in mitotic division, are regarded as representing self-replicating organelles. They occur with varying frequency in different normal cells and exhibit uniform appearances showing no signs indicative of duplication such as budding or division. In order to obtain a deeper insight into centriole formation and evolution, cases of parathyroid and pituitary adenomas with a high centriole population were investigated by electron microscopy.The material used for the present study consisted of 4 chief cell adenomas of the parathyroid gland, 7 sparsely granulated pituitary growth hormone cell adenomas and 1 mixed cell pituitary adenoma composed of sparsely granulated growth hormone cells and prolactin cells. These adenomas were selected from a large number of cases (26 parathyroid adenomas and 49 pituitary adenomas). All specimens were obtained by surgery from various patients with hyperparathyroidism or acromegaly. Small pieces of tissue were fixed immediately after removal in 2.5 per cent glutaraldehyde in Sorensen's buffer, postfixed in 1 per cent osmium tetroxide in Millonig's buffer, dehydrated in graded ethanol and embedded in Epon 812.
Ultrastructural Evaluation of Bone, Parathyroid and Ultimobranchial Glands in Lizards with Nutritional Osteodystrophy
Authors: Anderson M. P. , Capen C. C. 
Published: June 2020

Lizards in captivity are commonly afflicted with an osteodystrophy related to dietary imbalances in calcium, phosphorus and vitamin D. Young green iguanas (Iguana iguana) were fed beef heart based diets either low (0.2%) in calcium (experimental group) or adequate (2.7%) in calcium (control group). Both diets were unsupplemented with vitamin D and contained 1.1% P, 82% protein and 14% fat on a dry weight basis. Beginning with the sixth month iguanas of the experimental group developed progressive hypocalcemia (8.0 to 3.2 mg/100 ml plasma) resulting in secondary hyperparathyroidism. Progressive osteoporosis, detected radiographically,with osteomalacia was apparent from the seventh month until termination of the experiment at 9 months.Parathyroid chief cells of iguanas in the experimental group were primarily in the active stage of the secretory cycle. Lamellar and circular aggregations of rough endoplasmic reticulum were extensive and Golgi apparatuses were prominent (Fig. 1). Mitochondria often were displaced peripherally in chief cells by the large arrays of endoplasmic reticulum.
Ultracytochemical Localization of Potassium-Dependent NPPase in Rat Choroid Plexus
Authors: Davis D. A. , Milhorat T. H. , Hammock M. K. 
Published: June 2020

From a morphological standpoint, the choroid plexus epithelium appears ideally suited for the task of transporting fluid and electrolytes. However, until recently, a suitable method for demonstrating enzyme systems associated with these functions has been unavailable. In 1972, Ernst reported a technique for specifically localizing Na-K-ATPase. This technique was used in the following study on rat choroid plexus.The choroid plexuses from the lateral ventricles of adult male Wistar rats were fixed intraventricularly with 3% depolymerized paraformaldehyde in 0.1M cacodylate buffer at pH 7.3-7.4. The tissue was excised and placed in a vial where pre-fixation continued for 90 minutes at room temperature. Subsequently, choroid plexus tissue was incubated according to the method of Ernst. Control experiments consisted of: 1) omitting either potassium or magnesium from the incubation medium; 2) omitting the substrate p-nitrophenyl phosphate (NPP) from the incubation medium; and 3) adding lOmM ouabain to the incubation medium.
Cytochemical Specializations on the Luminal Surface of Blood Vessels in the Developing Rat Central Nervous System
Authors: Hannah R. S. , Rosenquist T. H. 
Published: June 2020

Developing blood vessels in the rat central nervous system exhibit several unusual luminal features. Hannah (1975) used high voltage electron microscopy to demonstrate numerous ridges of endothelium, some near junctional complexes. The ridges produced troughs (which may appear as depressions) in the endothelial surface. In some areas ridges extended over the troughs, removing them from direct contact with the luminal surface. At no time were the troughs observed to penetrate the basal laminae. Fingerlike projections also extended into the lumina.To determine whether any chemical specializations accompanied the unusual morphological features of the luminal surface, we added 0.1% Alcian blue (Behnke and Zelander, 1970) to the 3% glutaraldehyde perfusate (cacodylate buffer, pH 7.4). After Alcian blue had reacted with the luminal glycocalyces, the dye was dissociated with MgCl2 via critical electrolyte concentration method of Scott and Dorling (1965). When these methods are applied together, it is possible to differentiate mucopolysaccharides (glycosaminoglycans or GAG) with the electron microscope.
High Resolution Cytochemical Demonstration of Electrical Charges in Synaptosome Surface Coat
Authors: Feria-Velasco Alfredo , Sánchez Salvador , Magdaleno Víctor 
Published: June 2020

Electrophoretic mobility studies in synaptosomes from rodent brain have shown that approximately a third of their mobility towards to the cathode is conferred by sialic acid exposed to neuraminidase. On the other hand, it is known from biochemical works that sialic acid is one of the carbohydrate residues present in glycoproteins and gangliosides at the nervous tissue elements.The present work deals with the identification and distribution pattern of electrical charges at the synaptosome surface by means of cytochemical techniques for electron microscopy and correlative biochemical methods.Synaptosome fraction was obtained from mice brain homogenates in 0.32M sucrose according to a previously described method (3). After glutaraldehyde fixation, the samples were stained with dialyzed colloidal iron solutions, at pH 1.8 [(+)Fe] or 4.0 [(-) Fe] respectively (4), postfixed in osmium tetroxide and further processed for electron microscopy. With (+)Fe, homogeneous fine electrondense deposits were seen at the synaptosome surface (Fig. 1).
Ultrastructural Changes in Hamster Retina Following Injection of 5-Hydroxy-Tryptophan
Authors: Taylor R. , Gerodetti M. , Blystone R.V. , Smith P. 
Published: June 2020

It has been proposed that 5-hydroxy-tryptamine (5-HT) may function either as a neural transmitter or as a neural regulator within the central nervous system. Upon administration of adequate amounts of 5-hydroxy-tryptophan, the level of 5-HT within the central nervous system is significantly increased. 5-hydroxy-tryptophan is actively transported from the blood into the central nervous system where it is decarboxylated to form a mobile pool of 5-HT which is presumably stored and concentrated within the synaptic vesicles of the nerve endings.Hamsters were administered 100-150 mg/kg of body weight injections of 5 hydroxy-tryptophan. Within 15 to 30 minutes post injection, the hamsters began experiencing massive tremors and loss of coordination but were observed entering a more tranquil state after an hour and a half. At two hours post injection, the hamsters were sacrificed by cervical dislocation, the eyes removed, and retinal tissue obtained.