bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear microtubular invaginations in acute lymphoblastic leukemia cells
Authors: Ahearn M.J. , Yee G.S. , Trujillo J.M. 
Published: June 2020

Intranuclear "mitochondrion-like" bodies have been described in the neoplastic cells of both the Sezary syndrome and mycosis fungoides. (2) These cytoplasmic structures are hypothesized to be trapped in the nucleus during mitotic division and to represent another example of the abnormalities of the Sezary cell.We have recently observed identical nuclear inclusions in lymphoblasts from pediatric acute lymphocytic leukemia (ALL) patients, Figs. 1 and 2. In each instance, the malignant cells represent an abnormal variant of thymus-derived lymphocytes. They display a common feature in the pronounced maturation asynchrony between the nucleus and the cytoplasm. Our continuing studies of ALL blasts have revealed the presence of an apparent longitudinal and cross-sectional presentation of the "mitochondrionlike" body, Fig. 3. In this conformation, the similarity between the structure's outer membranes and the double-walled nuclear membrane becomes apparent.
Structural investigation of frozen-hydrated Omp C specimens prepared by the fatty acid monolayer technique
Authors: Chang Chung-Fu , Glaeser Robert M. 
Published: June 2020

Omp C (M.W. ∽36,000) is one of the major proteins in the outer membrane of E. coli. Trimeric Omp C forms a pore allowing small hydrophilic molecules to diffuse across the membrane. Specimens we have studied are prepared by reconstituting purified Omp C trimers with lipid A (the core structure of the outer membrane 1ipopolysaccharide). These specimens form 2-D periodic arrays with a size of ∽0.5 μm on edge.Initial structural investigations on negatively stained Omp C specimens have been reported by Grano et al. We now present a preliminary structural analysis of frozen-hydrated Omp C, using specimens prepared by a modification of the stearic-acid monolayer technique of Hayward et al. Stearate monolayers can successfully "squeeze out" the bulk water on the surface of the EM grid only at relatively high concentrations of Ca++ and high pH. In the current study, we replaced the stearic acid with behenic acid, CH3(CH2)20COOH, which can adhere to a suitably prepared EM grid from a subphase of distilled water.
Electron microscopic localization of sulfated glycosaminoglycans and proteoglycans in pleomorphic adenomas
Authors: Lam Ronald 
Published: June 2020

Although “myoepithelial” cells in pleomorphic adenomas have been implicated by several ultrastructural studies as responsible for the production of myxomatous and chondroid stroma, the cellular source of stromal glycosaminoglycans and proteoglycans has yet to be demonstrated histochemically by electron microscopy.Three major salivary gland pleomorphic adenomas were examined by electron microscopy after fixation in 2.5% glutaraldehyde and in 0.2% ruthenium red-glutaraldehyde. Routine ultrastructural preparations revealed a spectrum of cells with epithelial and mesenchymal features. The mesenchymal cells in the myxoid region displayed intracytoplasmic 70-80Å microfilaments, prominent Golgi complex, RER, and secretory vesicles. The fine structural appearance with ruthenium red stained tissue was similar to that of routine preparations. However, with ruthenium red staining, proteoglycans of the myxoid stroma could be visualized as numerous extracellular 250-500Å polygonal matrix granules with fine projecting filaments (Fig. 1A). Similar positive ruthenium red stained intracellular granules were observed within the cytoplasmic vacuoles of the mesenchymal cells, a feature not present in cells with epithelial differentiation (Fig. 1B).
Computer Simulation of the Imaging of Atomic Defects in Metals
Authors: Fields P. M. , Cowley J. M. 
Published: June 2020

Localized defects in metals, such as vacancies and interstitials, should have scattering powers for electrons comparable with those of the single heavy atoms which have been imaged in recent years by use of high resolution electron microscopes. It should therefore be possible to obtain appreciable contrast from such defects with current lOOkV electron microscopes. However in order to distinguish the intensity variations due to these defects from those due to specimen surface structure, contamination or other causes, it may be necessary to use the improved resolution of high voltage microscopes so that the characteristic shapes of the defects and their local strain fields can be recognized.In order to test these speculations, we have made computer calculations of the images and diffraction patterns to be expected from split interstitials in thin crystals of gold and aluminum for bright-field and dark-field imaging with a lOOkV microscope with an objective lens having Cs = 1.8mm and for a l000kV microscope, Cs = 1.8mm.
Computer Indexing of Electron Diffraction Patterns Including the Effects of Lattice Symmetry
Authors: Lally J. S. , Lee R. J. 
Published: June 2020

In the 50 year period since the discovery of electron diffraction from crystals there has been much theoretical effort devoted to the calculation of diffracted intensities as a function of crystal thickness, orientation, and structure. However, in many applications of electron diffraction what is required is a simple identification of an unknown structure when some of the shape and orientation parameters required for intensity calculations are not known. In these circumstances an automated method is needed to solve diffraction patterns obtained near crystal zone axis directions that includes the effects of systematic absences of reflections due to lattice symmetry effects and additional reflections due to double diffraction processes.Two programs have been developed to enable relatively inexperienced microscopists to identify unknown crystals from diffraction patterns. Before indexing any given electron diffraction pattern, a set of possible crystal structures must be selected for comparison against the unknown.
Clustering of Atomic Defects in Copper during In situ Annealing in the High-Voltage Electron Microscope
Authors: Jäger W. 
Published: June 2020

The migration of atomic defects (interstitials, vacancies) introduced by electron irradiation of metals at low temperatures during subsequent thermal annealing may lead to mutual annihilation, to annihilation at sinks, or to an agglomeration of atomic defects of the same species into clusters. In the past this has been investigated in copper mainly by resistivity experiments and diffuse x-ray scattering methods. In-situ annealing experiments in a high-voltage electron microscope may yield additional information about the formation and nature of clusters and therefore may contribute to the understanding of the annealing stages in metals. This paper summarizes the most important results of a detailed investigation of the formation of clusters in copper during in-situ annealing between 10K and 470 K.Thin copper foils (nominal purity 99.999%, foil thickness,~200nm) were irradiated with 650 keV electrons at 10 K to a total dose of 8 x 1019e cm-2 in a Hitachi HU 650 microscope equipped with a helium-cooled specimen stage.
An Application of High Brightness LAB6 Cathode Gun to JEM-100CX
Authors: Yonezawa Akira , Nakagawa Seiichi , Suzuki Mikio 
Published: June 2020

The LaB6 cathode gun, which is noted for its high brightness and long life, is highly expected to improve the image quality of CTEM,STEM and secondary electron images. But, in order that the LaB6 gun may stably attain its maximum performance, it is necessary to solve big prblems concerning the vacuum pressure around the tip and with tip holding and heating.Here, we shall introduce excellent data and CTEM and secondary electron images, obtained by a clean high vacuum EM, the JEM-100CX with aid of a LaB6 emitter assembly1)commercialized as an option for the JSM-35. The instrument also used a high resolution scanning device, ASID-4D to obtain the secondary electron images. The JEM-100CX can easily attain, even in the gun chamber, a 10-7 torr clean high vacuum which is high enough for a LaB6 tip, because it employs the “CASCADE” differential pumping system2). We shall discuss the gun assembly.
In situ Investigation of Field and Temperature Effects on the Surface of Metal Tips
Authors: Colliex C. , Sudraud P. , Van de Walle J. 
Published: June 2020

For the achievement of high brightness ion sources, field evaporation, desorption and ionization effects constitute very attractive solutions (1,2). All theses mechanisms are promoted in a very small area on the apex of metal tips. The interpretation of field ionization images is often made uncertain because of the lack of accurate information concerning the topography and the crystallographic structures of the emitter.Several authors (3,4,5) have associated electron microscope visualization of tungsten tips either with CTEM (at standard or high voltages) or with SEM, with the study of field emission or ionization patterns. But very few of these works have coupled these observations to the determination of the fundamental parameters (electric field, tip temperature) which control the emission. For instance, in the scanning microscope, the thermally emitted electrons disturb heavily the working conditions preventing from dynamic in-situ observations.
Lattice Imaging of Grain Boundary Precipitation Reactions
Authors: Gronsky R. , Thomas G. 
Published: June 2020

Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Materials Science and Mineral Engineering, University of California, Berkeley, California 94720.Grain boundaries are known to catalyze a wide variety of solid state phase transformations which drastically affect metallurgical properties. The study of these reactions has traditionally required transmission electron microscopy, particularly when the transformation products are only partially developed. In the present paper, an application of lattice fringe imaging to the study of grain boundary reactions in Al-Zn alloys is described. The technique has proven to be far superior to conventional TEM methods in providing information on not only the detailed structural configuration of lattice planes at boundaries, but also the compositional changes, to within ∽10Å of the boundary plane, accompanying the transformations.
The Strain Dependent Accommodation Behaviour of Extrinsic Grain Boundary Dislocations
Authors: Jones A.R. , Ralph B. 
Published: June 2020

Previous work on a fully austenitic stainless steel has shown that the nucleation and growth of Niobium Carbide (NbC) particles at grain boundaries can be substantially affected by deformation introduced prior to ageing (1). The present investigation which is, in part, an extension of the above work was instigated to examine the accommodation behaviour of extrinsic grain boundary dislocations as a function of deformation and temperature. The alloy investigated contained 20% chromium, 25% nickel, 0.6% niobium, 0.02% carbon + nitrogen, balance iron. Solution treated specimen material was cold rolled by 2%, 5% and 13% prior to annealing for times between 5 and 15 minutes at temperatures ranging from 650°C to 1000°C.Figures la and b show typical grain boundaries in the as-worked 2% and 5% materials; extrinsic dislocations appearing as linear features in the grain boundaries. However, grain boundaries in specimen material deformed by 13% contained such large numbers of these defects that the clear resolution of the individual dislocations was frequently impossible.
Characterization Of Flaws Produced By Mechanical Grinding Of Si3N4
Authors: Tighe Nancy J. 
Published: June 2020

The flexure strength of silicon nitride is related to the size of flaws at or below the surface. These flaws typically are cracks which nucleate at ground surfaces or at internal inclusions. One crack from the population of flaws grows under the applied stress and causes failure. Recent mechanical testing experiments in this laboratory showed that high temperature (1200°C) exposure can either increase or decrease the strength of silicon nitride depending on the time of exposure and the testing temperature (1). Because this material oxidized readily at 1200°C, both oxidation and heat treatment changed the flaw population. The change in flaw population can be determined after nature of the initial population is established.The initial flaw population produced by grinding is being characterized by examining thin foils made from silicon nitride samples which had different surface treatments.
Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism
Authors: McKee Thomas R. , Buseck Peter R. 
Published: June 2020

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).
Crystal Structures Of L-Nb205 AND L-Ta205
Authors: Iijima Sumio 
Published: June 2020

Although structures of tantalum pentoxides have been extensively studied, they have not been fully understood because of the complex nature of their X-ray diffraction patterns. In this study we made some observations on crystals of L-Ta2O5 and L-Nb2O5 using a high resolution electron microscope. The latter structure has been believed to be isostructural with L-Ta2O5. The samples were prepared by Dr. Roth at NBS and were parts of the products used for determining phase relationships in niobium pentoxides (1) and the Ta2O5-Ta2WO8 system (2).According to the X-ray data both structures have orthorhombic unit cells with a = 6.2, b = 29.3, c = 3.9Å. The structures are based on the U03-type and the b spacings are nearly 8 times those of the subcell. Electron diffraction (E.D.) patterns of L-Nb2O5 and L-Ta3O5 crystals showing a*-b* reciprocal sections confirmed generally the results of X-ray works (Figs, la and lc).
Image Contrast Of Amorphous Carbonaceous Materials
Authors: Iijima Sumio 
Published: June 2020

We have previously reported a method for preparing extremely thin films of graphite single crystals for use as support films (1). Usefulness of these films, in particular, for obtaining high resolution images of phase objects, was demonstrated by imaging (with bright field mode of CTEM) surface steps with heights of less than 10Å on graphite films (2) and also single atoms of tungsten (3). In this study using the same graphite substrates we have made some observations of amorphous materials to understand the image contrasts in terms of microstructure.Although image contrasts of thin evaporated carbon films, even if prepared as thin as possible, do not show measurable dependence on film thicknesses, we chose as test objects the extremely thin films of contamination which grew discontinuously on the substrate films during specimen observation (4). Image contrasts of these films were then compared with those of known structures such as surface steps and a single layer of graphite crystal.
Microstructural Changes in 900°C Heat Treated Ti-6A1-4V After Deformation
Authors: Imam M. Ashraf , Fraker Anna C. , Gilmore Charles M. 
Published: June 2020

It has been shown that the mill annealed form of Ti-6A1-4V has improved fatigue resistance after it has been heat treated at 900°C for 10 minutes and water quenched, some of the increased fatique strength of this material may result from microstructural adjustments to deformation. The present study deals with the general microstructure of the material and specifically with that of the martensite before fatigue, at the fracture surface after fatigue and at distances away from the fracture surface. In addition, microstructural changes which are brought about by annealing this heat treated material at 500°C for 8 hours are discussed.Thin foil specimens were prepared from bulk materials by spark cutting and planing. This was followed by electropolishing in a solution of 62.5% methanol, 31% butanol and 6.5% of 70% perchloric acid at 13.9 volts at -40°C. Fatigue testing was conducted at ±0.020 shear strain with a constant axial stress of 2.12 x 107 N/M2.
The Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Solid Solution
Authors: Marti Jordi , Stulga John E. , Tien John K. 
Published: June 2020

A recent development in powder metallurgy technology, known as mechanical alloying (1), can find applications in alloys which cannot be manufactured by conventional processes, due to high melting temperatures, chemical incompatibility of constituents in the melt, or high reactivity. The process has been utilized in the production of a nickel-base superalloy and a nickel-base solid solution which contain dispersions of fine and inert oxide particles for high temperature strength. As part of a study of the creep and stress rupture behavior of these alloys, the as-received and crept microstructures have been examined using the transmission electron microscope. This note discusses the fine-scale microstructure of the mechanically alloyed oxide dispersion strengthened (ODS) nickel-base solid solution.The alloy has a nominal chemical composition in weight percent of Ni - 20Cr - 0.5Ti - 0.3A1 with O.6Y2O3oxide particles.
Annealing Temperature and Grain Size Effect on the Grain Boundary Ledge (Density) Structure in Nickel
Authors: Venkatesh Eswarahalli 
Published: June 2020

In recent years many researchers have shown great interest in understanding the structure of grain boundaries1,2 and their influence on the mechanical properties of metals and alloys3-5. It has been shown that the structure of grain boundaries can be changed by appropriate thermomechanical treatments6. There are many experimental parameters that can influence the grain boundary ledge structure. The influence of annealing temperature and grain size are considered here.In the present work, pure (99.98%) nickel sheet mill rolled (hot) to 0.022 in. thick was used. One batch of sample was cut and rolled to 40% reduction in thickness and annealed at 800-1125°K in argon,and air cooled to achieve a constant grain size of 50 μm in all samples. A second set of samples was cut and rolled 10-70% reduction in thickness and similarly annealed at 800-1325°K so as to obtain different samples with grain size of 2, 30, 50, and 150 μm.
Metallurgical Problems with Orthopaedic Joint Prostheses
Authors: Jendrzejewski John P. , Paulson Gary G. 
Published: June 2020

Metallic joint prosthetic devices are used to replace the skeletal structure of the human body which has been destroyed by disease or accident. These surgical implants are intended to remain in place for the rest of the patients' life, but often they fail. Subsequent removal and replacement is both expensive and painful. We have had the opportunity to examine numerous joint prosthetic devices which have fractured in use. The scanning electron microscope and energy dispersive X-ray spectrometer used in conjunction with conventional metallography have proven very useful for these failure analyses.The primary failure mode of joint prostheses is metal fatigue. Shown in Figure 1 is a femoral component of a hip prosthesis which failed in the stem portion. Fractographic analysis reveals that reverse bending stresses initiated fatigue cracks at the distal and proximal portion of the stem as pointed out in Figure 2.
Void Growth in the Early Stages of Electromigration
Authors: Lloyd J. R. , Nakahara S. 
Published: June 2020

Recently, a TEM study has shown that a high density(l010 to 1012/cm2) of small(<50A) voids are present in both as-deposited(l), and annealed(2) evaporated gold films. Using the defocus contrast technique, Lloyd and Nakahara(1) were able to make void size measurements which allowed a systematic study of the dependence of void formation on deposition parameters.In order to study the role of pre-existing voids in electromigration(EM) damage, ^lOOOA-thick gold films with initial void densities of lO10and1011/cm2 were obtained by evaporation onto KC1 substrates held at 280°C and 80°C, respectively. This choice of substrate temperatures was based on our previous study (l) of the effect of deposition parameters on void density.All films studied were found to contain many small voids which were revealed with the use of defocus contrast. EM-induced void growth was studied by comparing two films deposited onto a substrate held at 80°C during the same evaporation.
Brittle Grain Boundary Fracture in Iridium
Authors: Rohr D. L. , Hecker S. S. , Murr L. E. 
Published: June 2020

Iridium is a most interesting fee metal with a high melting point (2443°C) and extremely high elastic moduli (Young's modulus of 76 million psi). Single crystals of Ir fail by brittle cleavage and polycrystalline Ir fails by brittle intergranular fracture at temperatures below 1000°C. We have previously shown that both modes of fracture are intrinsic and not impurity related. (1)The present study was undertaken to study the grain boundary structure of Ir by transmission electron microscopy. Sheet specimens of Ir-0.3%W (used in space nuclear power applications) were recrystallized at temperatures above 1300°C. Thin foils were prepared by spark planing and electropolishing with an acidified CaCl2 solution in a jet polisher and were examined in a JEOL 200 B electron microscope operated at 200 kv.We examined a large number of foils and found the most interesting grain boundary features to be ledges (2) (Fig. la).
Molecular Structure of the Outermost Cell Wall Component of Spirillum Serpens
Authors: Chiu Wah , Grano David 
Published: June 2020

The periodic structure external to the outer membrane of Spirillum serpens VHA has been isolated by similar procedures to those used by Buckmire and Murray (1). From SDS gel electrophoresis, we have found that the isolated fragments contain several protein components, and that the crystalline structure is composed of a glycoprotein component with a molecular weight of ∽ 140,000 daltons (2). Under an electron microscopic examination, we have visualized the hexagonally-packed glycoprotein subunits, as well as the bilayer profile of the outer membrane. In this paper, we will discuss some structural aspects of the crystalline glycoproteins, based on computer-reconstructed images of the external cell wall fragments.The specimens were prepared for electron microscopy in two ways: negatively stained with 1% PTA, and maintained in a frozen-hydrated state (3). The micrographs were taken with a JEM-100B electron microscope with a field emission gun. The minimum exposure technique was essential for imaging the frozen- hydrated specimens.