bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructure and defects of antigorite
Authors: Spinnler G. E. , Veblen D. R. , Buseck P. R. 
Published: June 2020

Antigorite, one of the three species of the serpentine group of minerals is characterized by a corrugated structure made up of layers composed of tetrahedrally and octahedrally coordinated sheets (Fig. 1). This modulated structure model was proposed by Kunze in 1956, and since that time has generally been accepted to account for the x-ray diffraction features of antigorite. Typically, diffraction patterns of antigorite yield an a dimension of ∽40 to 50A, whereas the same dimension of lizardite, the flat serpentine mineral, is ∽5.3A. HRTEM images confirm the basic corrugation of the structure of antigorite. This study reveals both the modulation of the antigorite structure as well as several previously unrecognized nonperiodic features of a particular antigorite.Classically the serpentine group of minerals has been divided into three distinct species based on their structures: lizardite, antigorite, and chrysotile, a cylindrical structure (Fig. 1). The compositional range of lizardite and chrysotile overlap, whereas antigorite has a small but significant deficiency in octahedral cations and OH owing to the reversal of polarity of the tetrahedral sheets.
Carbon analysis in reactor pressure vessel steels
Authors: de Hodgins O.C. , Shriver B.L. , Lawless K.R. 
Published: June 2020

The effect of neutron irradiation on the notch ductility transition temperature (NDTT) of A533B steel is known to be affected by the activity of the carbon atom which would be affected by its nearest neighboring substitutional atom, that is, silicon, manganese, etc. The high carbon activity resulting from increased nickel and silicon promotes the formation of vacancy complexes which produce irradiation hardening and, therefore, higher NDTT shifts.The present study has been undertaken to clarify the role of carbon and impurities in A533-B steel in the mechanism of neutron embrittlement, two specimens of A533-B pressure vessel steels differing in radiation sensitivity have been examined using transmission electron microscopy. The study showed that the carbon-vacancy complex in iron (ferrite) has a carbon atom positioned a finite distance from the vacancy along a <100> line. In some cases martensite was found, in others, a combination of martensite with ferrite.
Phase changes in a laser-alloyed Fe-5Cr steel
Authors: Padmanabhan R. , Wood W. E. 
Published: June 2020

Laser surface alloying is a relatively new method to modify metal surfaces. A suitably applied metal coating and an underlying metal substrate are rapidly melted by a high power, continuous laser beam. The resultant melting, mixing and rapid solidification can be controlled to form an alloyed fusion zone at the surface with the desired mechanical properties.In this work, Ni-Cr and Ni-Cr-WC metal powders were thermally deposited on a Fe-5Cr steel. Coating parameters were adjusted to achieve desired coating thicknesses. Laser processing was carried out with a continuous CO2 laser beam capable of power densities up to 108 watts/sq.cm. to alloy the metal powder with the base material. Power density, scan rate, spot size and other parameters were all controlled to produce penetration depths of up to 850μm (Table 1). Interpass steps were adjusted to produce both overlapping and discrete fusion zones.
Comparison of residual microstructures in stainless steel after very high pressure shock deformation
Authors: Murr L.E. , Staudhammer K.P. , Johnson K.A. , Olinger B.W. 
Published: June 2020

It is now well documented that the explosive shock hardening of 304 and other 300-series stainless steels (which has been reported over a period of nearly two decades) is due in large part to the formation of deformation twins or twin faults. It has been shown in fact that for plane-wave shock loading where the sample is subjected to a pure, compressional shock wave, the hardening saturates with pressure and declines at pressures near or above 1 megabar (>100 GPa) due to thermal effects.In experiments involving plane-wave shock loading and which employed a flyerplate technique, each test at a specific pressure or pulse duration involved a separate explosive event and required difficult and elaborate experimental arrangements. In some respects this was a convenient arrangement because thin sheets could be sandwiched in these assemblies, providing a convenient regime for transmission electron microscopy of the shock-induced microstructures.
In situ precipitation of θ on A1 in the Al-Cu system
Authors: Clark W.A.T. , Smith D. A. 
Published: June 2020

Precipitation in the Cu-Al system can be in several forms, some of which, such as the θ	", θ', and θ phases of CuAl2, have been extensively investigated by both X-ray and TEM methods (see e.g. 1). In general, the precipitation sequence has been systematically controlled by ageing supersaturated solutions of Cu in Al for specific times at temperatures chosen to lie within the upper and lower solvus lines of the required phase. Specimens for TEM were then prepared by standard techniques. In cases where precipitation was carried out in situ, using a hot-stage in the TEM, nucleation at the foil surfaces has appeared to play a prominent role, and precipitation within the foil is, for the most part, suppressed. In this investigation an additional feature is incorported, namely surface diffusion of Cu into a pure Al film, which then leads to the formation of CuAl2 θ-phase precipitates.
The 'well-known' theory of electron image formation
Authors: O'Keefe M.A. , Saxton W.O. 
Published: June 2020

A recent paper by Kirkland on nonlinear electron image processing, referring to a relatively new textbook, highlights the persistence in the literature of calculations based on incomplete and/or incorrect models of electron imageing, notwithstanding the various papers which have recently pointed out the correct forms of the appropriate equations. Since at least part of the problem can be traced to underlying assumptions about the illumination coherence conditions, we attempt to clarify both the assumptions and the corresponding equations in this paper, illustrating the effects of an incorrect theory by means of images calculated in different ways.The first point to be made clear concerning the illumination coherence conditions is that (except for very thin specimens) it is insufficient simply to know the source profiles present, i.e. the ranges of different directions and energies (focus levels) present in the source; we must also know in general whether the various illumination components are coherent or incoherent with respect to one another.
High-resolution observations of PbS adsorbed structures on Mg (00.1) surface
Authors: Tanaka N. , Mihama K. 
Published: June 2020

Characteristic surface structures and adsorbed structures of metals and semiconductors have been elucidated by reflection electron diffraction techniques such as LEED and RHEED. These techniques, however, can not give the information about the atomic arrangements or adsorbed sites in a direct way. The present work is the first trial of observing the adsorbed structures of PbS grown on Mg (00.1) surfaces with atomic resolution by using transmission electron microscopy. For such trials, the specimen preparation is the most important problem which decides the success of the observations. Especially, clean, flat and thin (∽10nm) substrates should be prepared.The present specimen substrates are Mg‐platelike particles prepared by gas evaporation technique. The procedure of the specimen preparation is as follows: Mg-platelike particles (thickness ∽ 20nm) are prepared by the evaporation of Mg ribbon in 10 Torr of argon and gathered on a perforated carbon films. After re-evacuation down to 1 × 10-8 Torr of the chamber, PbS of less than 1 nm in mean thickness is deposited on the Mg-plates.
Development of ultra high resolution analytical electron microscope ISI-EM-002A
Authors: Yanaka T. , Yonezawa A. , Oosawa K. , Iwaki T. , Suzuki S. , Nakamura O. , Watanabe M. 
Published: June 2020

Total design concept of EM-002A is to realize the following essential performance, that is, 1) attainment to ultimate high resolution as the conventional electron microscope, 2) complete compatibility of the high resolution mode and the analytical mode, 3) identification of the analyzed region and the observed image with atomic-level resolution, 4) observation of ultra fine structure of the biological specimen with maximum high contrast and so on.[Electron source] Accelerating voltage ranges from 20kV to 120kV in 6 steps Double Cockroft-Walton circuit is used as the high voltage generator and the high frequency ripple voltage is reduced to 0.1V. Electron gun assembly is composed of high voltage alumina insulator, whose shape is so well designed as to suppress micro-discharge to the negligible order.[Objective lens and specimen chamber] The objective lens is a strong symmetrical lens where the specimen chamber is located between the symmetrical upper and lower objective lens magnetic circuits. The objective lens has two powerful pole pieces, one being used for the ultra high resolution mode and the other for the standard mode.
Analytical electron microscopy of zeolites
Authors: Lyman C. E. 
Published: June 2020

Zeolites are crystalline aluminosilicates with regular arrays of uniform pores or channels ranging in size from 0.3nm to l.Onm depending on the specific structure and composition. Synthetic zeolites are an important class of technological materials with a wide range of selective adsorption, ion exchange, and catalytic properties. Catalytic properties of zeolites are often related to the silicon-- ttoo-aluminum atomic ratio; however, conventional microprobe analysis of zeolites has been limited to crystals much larger than the l-5μm size used in practice.Zeolite A is known to have a Si/Al ratio near unity since it contains the maximum aluminum content possible in a tetrahedral aluminosilicate framework. Particles of zeolite Na-A were embedded in epoxy and 80nm-thick sections were cut with a diamond knife and collected on carbon coated Cu grids. Analyses across zeolite particles were performed in a Vacuum Generators HB-501 STEM fitted with a Kevex x-ray detector. Because this material damages in the electron beam, x-ray spectra were taken while scanning the beam in a raster about l00nm x l00nm.
Compositional and structural characterization of isolated Pb-Bi microcrystals co-vapor deposited onto amorphous carbon
Authors: Gile W. W. , Jesser W. A. 
Published: June 2020

Recent interest in heterogeneous nucleation of binary alloys requires a knowledge of the structure and composition of deposits. Analytical electron microscopy and x-ray microanalysis is well suited to obtaining such information and has already been applied to the overall characterization of a collection of isolated microcrystals. The methods for performing this characterization are well documented; however, the application of the technique to the determination of composition of individual microcrystals as a function of crystal size is less well documented. In addition to the fundamental interest such information provides, it is of practical importance in such disciplines as supported alloy catalysts where a size-dependent composition and/or structural behavior may change both the selectivity and reactivity of a catalyst.The specimens in this investigation were prepared by co-vapor deposition of Pb and Bi onto hot amorphous carbon substrates between 150°C and 250°C. The Pb and Bi were co-evaporated from separate filaments of Mo and Ta, respectively, or an alloy of PbBi was evaporated from a single filament of tantalum with no significant difference occurring in the deposits prepared by either method.
Three-dimensional image reconstruction of rigor crossbridges in insect flight muscle (IFM)
Authors: Taylor K. , Cordova L. , Reedy M.C. , Reedy M.K. 
Published: June 2020

Dorsal longitudinal IFM from the water bug Lethocerus indicus, was rigorized by glycerination. Fiber bundle 958 retained a good rigor x-ray diffraction pattern after a 5 step fixation embedding sequence which included glutaraldehyde-tannic acid fixation, OsO4-UrAc staining, ethanol dehydration and Araldite embedding.The MYAC single filament layer of insect flight muscle contains alternating thick and thin filaments and is found isolated within longitudinal sections about 250Å thick. For our 3-D reconstruction we selected a MYAC region which appeared homogenous (both sides equal) over nearly 3/4 of a half sarcomere. Two tilt series ranging through ±60° of tilt in 10° steps were obtained, with tilt axis parallel to the filament axis in one and perpendicular in the other. Fourier transforms were calculated from 256x256 point arrays.The tilt data were combined using procedures similar to those used for 2-D crystalline arrays except that we obtain both amplitudes and phases from the image data.
Secretory activity of the gallbladder epithelium
Authors: MacPherson B. R. , Scott G. W. 
Published: June 2020

Evidence of secretory activity in gallbladder epithelial cells has been accumulating since the initial TEM observation by Johnson et al. in the dog. The presence of mucocoeles in human gallbladder, as will as histochemically demonstrable apical material, has long suggested the secretion of mucoid substances by these cells. Apocrine-like secretory processes have been documented by various investigators in the dog, fetal human and rabbit, mouse, guinea pig, trout, tench and other teleosts using light microscopy, TEM and SEM. Fujita et al. have indicated their belief in various stages of a secretory cycle in the epithelial cells of rabbit gallbladder. Our continuing biliary research has noted the occurrence of surface alterations suggestive of this secretory activity in the gallbladder epithelium of the dog, rabbit and man.Freshly excised tissue was rinsed in oxygenated Kreb's to remove excess mucoid and biliary deposits, pinned relatively flat on cork and floated face-down in either gluteraldehyde in Millionig's buffer (pH 7.4) or Karnovsky's buffered in 0.2M cacodylate (pH 7.4).
Induction of adhesion and spreading of Ehrlich ascite tumor cells in culture by dextran
Authors: E.C. Chew , T.K. Lam , H.J. Hou-Chan 
Published: June 2020

Ehrlich ascites tumor (EAT) has been maintained in our laboratory for about ten years. It has been reported that under normal conditions, EAT cells attach very weakly and do not spread on substrata. Cieslak et al. discovered that EAT cells coated with dextran T-500 adhere and spread on glass in serum-free media. The present communication reports the fine structural changes of EAT in the process of adhesion and spread induced by dextran.The EAT cells in ascitic fluid were collected from tumor-bearing mice and washed several times in DMEM medium. Dextran (MW.2,000,000), at a concentration of 5% was added to EAT cell suspension and cultured for 3 hours, 5 hours, 1 day and 3 days. Specimens were fixed in 2.5% glutaraldehyde for 1 hour at different time intervals after incubation, dehydrated, critical point dried and coated with gold. The coated specimens were examined with a Jeol JSM-35CF scanning electron microscope at 15 kV.
Evidence for extracellular matrix stimulation of neural crest cell migration
Authors: Jönsson L. , Löfberg J. , Mccoy Anita Nynäs 
Published: June 2020

The purpose of this experiment was to study if extrinsic factors regulate initial neural crest cell migration. Recent experiments suggest that a crucial extrinsic factor may be the embryonic extracellular matrix (ECM).The initiation of neural crest cell migration begins in the anterior trunk segments and follows gradually in more posterior ones. If the surrounding ECM has a migration-stimulating capacity, one would expect a decrease in the amount of ECM anterior-posteriorly at the initial migration stage.Epidermal grafts from the 3rd trunk somite level of Stage 25 axolotl embryos (Ambystoma mexicanum) were transplanted to the 9th trunk somite level of Stage 25 embryos (Fig. 1). At Stage 25, initial migration is soon to begin at the 3rd trunk somite level. In the controls, epidermal grafts were transplanted between the 9th trunk somite levels of Stage 25 embryos. The operated embryos were incubated for 48 hr at 15°C, fixed and prepared for light microscopy studies.
Localization of IgA and IgG within granules in mucous cells of the human endocervical epithelium
Authors: Sowinski J.M. , Mackay R.L. , Nicosia S.V. 
Published: June 2020

The human cervical canal is lined by three epithelial cell types: mucous, ciliated and reserve cells. The origin of immunoglobulins within the endocervix has not been clearly defined. In 1968, Pozzuoli et al presented immunoelectrophoretic and immunofluorescent evidence for the existence of IgA and IgG within both human cervical mucus and plasma cells which were present beneath the endocervical epithelium. Masson, Heremans and Ferin in 1969 analyzed pooled samples of cervical mucus by chromatography on DEAE-cellulose columns and were able to identify IgA and IgG as well as several other soluble proteins. In 1970 Lippes et al were able to identify IgA and IgG in the human cervix by immunocytochemical localization at the light microscopic level.Using a direct peroxidase conjugated antisera to human IgA and IgG, we have been able to confirm the presence of these immunoglobulins at the ultrastructural level and to localize both IgA and IgG within the granules of endocervical mucous cells.
Intercelular adhesion of teratocarcinoma STEM cells
Authors: Grabel L. B. , Martin G. R. , Rosen S. D. 
Published: June 2020

A major research interest is the identification of the cell surface molecules responsible for the selective intercellular adhesion of various cell types. Initially it was believed that cell-cell adhesion was mediated by tissue specific lock and key molecules present on adjacent cells; a single molecular recognition system would be sufficient to generate the desired selectivity. In the past few years it has become apparent that although specific recognition molecules are certainly involved in mediating intercellular adhesion, the idea of each cell type having a single unique molecular system of recognition is an oversimplification. The available data suggest that multiple systems of adhesion function simultaneously in any given cell type, and that the same or similar molecules may be involved in adhesion within different tissues.We have been studying the intercellular adhesion of teratocarcinoma stem cells, and review here evidence that at least two separable components are involved in their intercellular adhesion; one requiring the presence of divalent cations, and the other one involving recognition by a cell surface fucan/mannan specific lectin.
Low atomic number imaging of cells by electron energy loss spectroscopy
Authors: Leapman R.D. , Ornberg R.L. 
Published: June 2020

Recent advances in electron microscopy and analytical electron microscopy now make it possible to obtain elemental images of biological samples. In particular, electron energy loss spectroscopy is sensitive to the low Z elements, carbon, nitrogen, and oxygen which constitute most of the mass of a cell. Since the relative numbers of these atoms vary from one cellular compartment to another, significant information should be contained in C, N, and O images. The resolution in such images will clearly depend on the susceptibility of biological compounds to radiation damage. In order to learn how low Z imaging can be applied to cell physiology, we have obtained and describe here some preliminary carbon and nitrogen maps of the well characterized bovine adrenal chromaffin cells.Dissociated 3-day old bovine chromaffin cell cultures were quick frozen, freeze substituted in tetrahydrofuran, and embedded in Lowicryl HM20 resin as previously described. Energy loss images were obtained with recently developed instrumentation consisting of a Hitachi H700H TEM-5TEM and a magnetic sector electron spectrometer interfaced to a Digital Equipment Corporation PDP 11/60 and LSI 11/23 computer system. During image aquisition the computer steps the probe (∽10 nm dia.) across the sample and acquires several spectrum channels around selected core edges at each image point (pixel).
Negative staining versus rotational evaporation
Authors: Schmiady H. , Kreuzfeldt C. , Reuber E. , Tesche B. 
Published: June 2020

This comparative study demonstrates the salient differences between the two most common methods of contrasting subcellular particles, using the 40S ribosomal subunit from saccharomyces cerevisiae as test specimen because its socalled beak-like L (left) and R (right) particle projections can be unequivocally distinguished.The negative staining method produces images which are not artifact-free because it is a combination of fixation and chemical staining and, therefore, not neutral towards the object. For three-dimensional reconstruction it is unsatisfactory because:(1) The affinity of the support film to the negative stain solution differs so greatly that sometimes undesired positive staining effects occur.(2) The rendition of the structure depends on the embedding--that is, on the level of the negative stain; fluctuations in the level lead to a loss and/or change of the structure, and thus to difficulties in interpreting the stain distribution, especially when reconstruction of the object by means of tilt series is planned.
Electron crystal structure analysis of biomembrane lipids
Authors: Dorset Douglas L. 
Published: June 2020

Because of the well-known sample crystallization difficulties which often hinder the X-ray crystal structure analysis of many long-chain lipids, Parsons and Nyburg were the first to attempt the crystallographic elucidation of a phospholipid structure using electron diffraction intensity data from more readily-available microcrystals. Subsequent electron diffraction studies of various lipids in this laboratory over the past decade have revealed a number of peculiar features of such data-particularly if these are expected to resemble X-ray data. These observations have led to a physically reasonable overview of the problem based on well-established diffraction theory and have permitted the derivation of useful analytical procedures for electron crystal structure determination. It is interesting to note that the appropriate procedure is dependent on the method used for specimen crystallization.Lipid crystals grown from solution are typically plate-like with long alkyl chains packing with axes more or less perpendicular to the best developed crystal face ; an incident electron beam thus parallels the longest unit cell axis.
A neuronal mechanism for the control of latero-frontal ciliary activity in the fingernail clam, Musculium transversum
Authors: Paparo Anthony , Murphy Judith A. , Dean Robert 
Published: June 2020

Extensive studies have dealt with the transport of particles on the gill of suspension feeding bivalves, but our knowledge of the mechanisms involved is still incomplete. There is, however, physiological evidence that each of the ciliated cell systems in bivalve molluscs may be individually controlled. Three types of ciliated cells are distinguished on the gill of fingernail clams: frontal (FC); latero-frontal (LFC); and lateral (LC).For the most part in studies involving ciliary control mechanisms, LFC are neglected. It is thus the purpose of this study to present data which begin to elucidate a neuronal mechanism for LFC control.Gill preps were isolated with an intact nerve supply in a dish which was placed in a holder fastened to an adjustable stage of a microscope. In fields of view of 50 gill filaments, ciliary motility, chemical perfusion and electrical stimulation were observed and/or performed.