bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibration Isolation for Ultramicroscopy
Authors: Ackerman L. D. , Cocks K. A. , Caughey R. C. 
Published: June 2020

Ultramicrotomy remains a rather indefinite but necessary art for electron microscopists. One of the many factors which affects ultramicrotomy is extraneous vibration. Due to the construction of our facilities, difficulties were encountered. Upon the addition of more lab space it was desired to eliminate this problem. In conjunction with this goal several experiments were carried out in an attempt to assess the results quantitatively.Two standard laboratory cabinets were used to make a tabletop by bridging them with a 24" x 60" x 2" slab of soapstone. A smaller slab, 12" x 24" x 2", was centered on this tabletop with vibration damping rubber between the two. An ultramicrotome (Sorvall MT-2B) was placed on this smaller slab. The new laboratory is one story above ground, so four deep, independent footings were poured to support four beams each which in turn supports a concrete platform in the sectioning area.
Tissue Processing of Mammalian Vascular Endothelium for Scanning or Scanning-Transmission Electron Microscopy
Authors: Robertson Abel L. , McKalen Anne 
Published: June 2020

Samples of mammalian vascular endothelium,processed for surface scanning electron microscopy in the secondary electron emission mode or for transmission-scanning electron microscopy, were found to be susceptible to considerable artifacts during specimen preparation resulting in severe distortions in shape, size and spatial relationships.Of all methods tested, freeze-drying or freeze substitution induced most severe artifactual problems due to differential shrinkage rates of underlying elastic layers. While critical point drying with carbon dioxide or Freon 13 proved to be consistently superior to the above methods, significant cellular lipid losses during processing were unavoidable. Use of nitrous oxide as suggested by Koller and Bernhard reduced delipidation but was found to give inconsistent results.As an alternative, the following processing technique was developed and found to reduce morphological artifacts to a minimum while still preserving surface lipids and intercellular relationships.
Structure-Function Relationships in Mycobacteriophage R1
Authors: Soloff B. L. , Rado T. A. 
Published: June 2020

Mycobacteriophage Rl, a lipid-containing virus lytic for Mycobacterium smegmatis, was propagated and purified according to methods described previously. The lipid component of this bacteriophage is essential for its survival, but the studies of Fay and Bowman indicated that treatment of the virus with organic solvents resulted in no release of DNA and suggested that no morphological alteration of the nucleocapsid occurred. More detailed analysis of the lipid moiety reveals two components which are present in the virus but absent in extracts of uninfected host. One of these appears related to esterified cholesterol and the other acts like a free fatty acid in chromatographic studies.Treatment of phage on the grid with chloroform-saturated phage buffer caused little change in the appearance of the virus particles. By the same technic, treatment with a chloroform:methanol (2:1) solvent mixture resulted in disruption of the nucleocapsid and loss of DNA.
Alignment of Stereo Electron Micrographs for Projection
Authors: Mohr D. , Wray G. 
Published: June 2020

Stereoscopic presentation of electron micrographs by means of a polarized light projector and polarizing glasses requires carefully aligned slides. Each stereo pair should be aligned so that little if any projector adjustment is required when going from slide to slide. Proper and consistent alignment allows the audience to grasp the stereoscopic information more readily.Figure one shows a photograph of an alignment device for stereos. The two pictures can be moved in four ways: each film can be rotated, and one film translated both horizontally and vertically. The films are held in place by means of a vacuum. This leaves the front open so that the films can be easily transferred to a stereo mask by means of double-sided sticky tape once they are aligned.
In practice, a blank slide is first projected and the projector aligned so that the two images of the mask superimpose. The projector controls for horizontal and vertical movement remain fixed and the two films are then projected and moved until they are aligned.
Copper Storage Bodies in the Hepatopancreas of the Isopod, Oniscus Asellus
Authors: Roberts John W. , Witkus E.R. 
Published: June 2020

The hepatopancreas of the Isopod, Oniscus asellus consists of two pairs of blind-ending diverticula. Two types of mature cells are found: secretory cells (B-cells) and storage cells (S-cells). Both differentiate from a common stock of regenerative cells located at the blind end of each lobe.The appearance of what Weiser (1968) calls copper-storage bodies in the S-cells first occurs in the area of each lobe where the transitional cells differentiate into either mature secretory (B) cells or storage (S) cells. Figure 1 shows a basophilic S-cell sandwiched between two acidophilic B-cells. Figure 2 shows an electron micrograph of S-cell storage bodies with different affinities for electron-dense stain.By employing the method of Scheuer-et al (1967) copper localization was demonstrated only in S-cells. No copper was adsorbed into the B-cells but was actively absorbed into adjacent S-cells. This might indicate a mechanism for selective copper absorption in S-cells and no such mechanism in B-cells.
Scanning, Transmission and Electron Probe Analysis of the Cat Tapetum
Authors: Turnbill C. E. 
Published: June 2020

The tapetum lucidum or “bright carpet” of the cat eye is an adaptation for vision in limited light. The tapetum is of particular interest to our laboratory in that it might be used as a visual maker for cosmic “heavy primary” radiation. Since this marker would be located rear the retina, it would provide close correlation between high energy particle trajectories and related retinal damage. In preparation for this task, the cellular tapetune of adult cats were examined as controls.Adult cats were perfused with 2% glutaralderhyde, 2% paraformaldehyde and placed in cacodylate buffer. The tapetune was separated from the retina and choroid and processed for either scanning or transmission microscopy.Material for the transmission microscope was postfixed in 1% osmium tetroxide and examined both stained, with uranyl acetate and lead, and unstained for microprobe analysis. The stained sections (Fig. 1) cut parallel to the axis of the retinal rods, show layers of cells filled with electron dense rod-like structures approximately 10 microns by .1 micron.
TEM/STEM Characterization of Rapidly Solidified Aluminum Alloys
Authors: Kar R. J. , McHale T. P. , Kessler R. T. 
Published: June 2020

Low-density and high strength-type rapidly solidified (RST) aluminum alloys offer promise for structural aerospace applications. At Northrop, as part of a continuing program to establish structure-property relationships in advanced materials, detailed transmission electron microscopy (TEM)/scanning transmission electron microscopy (STEM) of candidate RST aluminum-lithium (Al-Li) and high strength (7XXX-type) aluminum-copper-magnesium-zinc (Al-Cu-Mg-Zn) alloys is routinely performed. This paper describes typical microstructural features that we have observed in these alloys.Figure 1 illustrates the microstructure of an inert-gas atomized RST Al-Li-Cu-Mg-Zr alloy. Frequently the grain boundaries are decorated with continuous or semi-continuous stringers of oxide that are relatively opaque to the incident electron beam. These have been identified to be Al-,Mg-, and Li- containing oxides present on powder particle surfaces prior to consolidation, and which have not been adequately broken up and dispersed by post-consolidation processing. The microstructures of these alloys are generally characterized by unrecystallized grains and equiaxed sub-grains pinned by fine (0.2μm) precipitates. These have been identified to be Al3Zr dispersoids using a combination of selected area diffraction/energy-dispersive x-ray (SAD/EDX) methods.
Alternative Crystallization Phases in Sub-Micron Droplets of Fe-Ni Alloys
Authors: Kim Yeon-Wook , Kelly Thomas F. 
Published: June 2020

When a liquid becomes highly supercooled, the crystal phases that nucleate from it may be one of several alternatives other than the primary crystallization phase. Even though these crystal phases would be metastable at the liquidus temperature of the primary crystallization phase, they may or may not be the most stable crystal phase at the nucleation temperature. Thus the term “metastable phase” is not generally applicable and the name “alternative crystallization phase” (ACP) is used.In order to determine whether a particular crystal phase may nucleate in a supercooled liquid, it is not sufficient to determine simply which phase has the greater liquidus temperature. The effect of liquid supercooling (relative to the liquidus temperature of each phase) on the nucleation of each possible phase must be considered. For a given situation (eg. liquid volume, cooling rate,…), the propensity of a given phase for nucleating from the supercooled liquid can be gauged by calculating a nucleation temperature for that phase [1].
Effects of the Elements Ni, V, Co on Ultrastructure of the Heart Muscle
Authors: Kovach A.G.B. , Balogh I. , Rubanyl G. 
Published: June 2020

The finding of altered distribution of metallic elements in the infarcted myocardium and the demonstration of elevated serum Ni concentration in patients with myocardial infarction, burns, shock and toxemia have indicated that elements, like Ni, V, Co etc. may play important role in cardiovascular and obstetrical pathology, This report explains cardiovascular effects of nickel, vanadium, and cobalt ions at elevated concentration and gives valuable information about the possible physiological and pathological significance of these elements.METHODIsolated rat hearts were perfused by Krebs-Ringer bicarbonate solution for 15 minutes at room temperature. Various doses of nickel chloride, sodium vanadate and cobalt chloride (1-100 uM) were then added to the Krebs solution.
Development of a New TEM With an Image Rotation System
Authors: Isakozawa S. , Kobayashi H. , Ohashi T. , Tomita M. , Kamimura S. 
Published: June 2020

We have developed a new 125KV TEM (Fig. 1). It incorporates an electron gun operable up to 125KV, 3-stage illumination lens system, and 5-stage imaging lens system. Microprocessors are used to control the high voltage, electron optics and vacuum system.In the high voltage system, accelerating voltage is variable from 10KV to 125KV with increments of 100V/step. In the low voltage operation at 10KV and 25KV,the anode to wehnelt distance is automatically controlled for optimum gun brightness. Filament and bias voltage supplies are also precisely regulated to give stable emission currents at all accelerating voltages.Imaging lens system is free of image rotation during magnification change from 100x to 500,000x. In addition, a new image rotation system is built in. This image rotation system utilizes the individual lens data such as rotation angle, focal length, etc. When a required image rotation angle is given, the computer determines excitation condition of each lens for a selected magnification.
The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis
Authors: Tousimis A.J. 
Published: June 2020

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.
Practical Aspects of Preparing Thin Sections From Catalyst Specimens
Authors: Chan I. Y. , Cain J. H. , Rea T. M. 
Published: June 2020

Transmission electron microscopy is an important technique for catalyst characterization. The thin-sectioning technique has been recognized as the preferable specimen preparation method in most cases. The merit of this technique has been discussed in a number of publications. It has been applied to catalysts containing alumina, carbon, silica, and zeolites. In this paper, we present the practical aspects we have found for obtaining high quality thin sections consistently.Requirements1.The sections should be mechanically and electrically stable under the electron beam.2.They should be as thin as possible in order to achieve the highest image resolution permitted by the instrument.3.The results should be readily reproducible so that comparison between similar samples can be made easily.4.The number of artifacts (e.g., those arising from shatter marks, knife marks, and thickness variations) should be minimized.
Crystal Site Occupancy of Alloying Elements in Polycrystalline Nb3Sn Superconductors By Electron Channeling
Authors: Tafto J. , Sabatini R. L. , Suenaga M. 
Published: June 2020

Many of the crystallographic problems encountered in materials science require techniques that can be used on small volumes of materials, e.g., in VLSI semiconductors, thin films, and the composite materials used in high magnetic field superconductors. In recent years several sensitive and accurate microcrystallographic techniques, based on diffraction of 100-keV electrons, have been developed. For example, convergent beam electron diffraction is a powerful technique to determine the symmetry of microcrystals and electron channeling techniques for the location of dilute elements in the crystal unit cell.We shall here deal with the application of the electron channeling technique called ALCHEMI (Atom Location by Channeling Enhanced Microanalysis) to study composite materials by determining the crystal sites of small amounts of alloying elements in Nb3Sn made by the bronze process. This is a problem of considerable interest in conjunction with the development of high magnetic field superconductors, because small amounts of certain alloying elements increase the upper critical magnetic field significantly.
Microcracks and Micro-Twins in Partially Stabilized Zirconia Alloys (PSZ)
Authors: Lu Y.N. , Tighe N.J. 
Published: June 2020

Three commercial magnesia-doped partially stabilized zirconia ceramics (Nilsen MS and TS and Coors TT), have been examined before and after aging for 100 hours at 1000°C The proposed use of these ceramics for components in diesel engines requires long term reliability at temperatures up to 1000°C. The microscopy is being used to identify the microstructural changes that can result during high temperature tests carried out in this laboratory.Pure zirconia exists in three polymorphs which on cooling transform from cubic to tetragonal (at -2200°C) to monoclinic (at -950°C). With MgO additions and under appropriate conditions of temperature and time, the tetragonal to monoclinic transition can be controlled to produce partially stabilized magnesia zirconia alloys with grains and intergranular phases that are mixtures of monoclinic, tetragonal and cubic phases. The morphology of the grains and intergranular phases is readily distinguished in polished sections; however, the phase distributions can be confirmed only with electron microscopy. For example, the intergranular phase is predominantly monoclinic and grains can have: transgranular monoclinic plates in a cubic matrix; twinned monoclinic plates in a cubic matrix; distributions of tetragonal precipitates in a cubic matrix. The microcracks are found by examining interfacial regions at high magnifications.
Weak-Beam Imaging of Coherent Twin Boundaries After High-Temperature Deformation
Authors: Rajan Krishna 
Published: June 2020

Weak beam dark field microscopy has been used extensively to study deformation induced intragranular defects in materials. However as noted by Tones et al weak beam imaging is also an asset in examining intergranular defects. The localisation of strain contrast close to the defect core by weak beam imaging allows the interaction of matrix dislocations with the boundary (to form extrinsic dislocations) to be studied more easily. Also, the reduction in extinction distance with weak beam microscopy produces a higher density of extinction contours, which allows topographical discontinuities associated with long range strain fields to be more readily observed.Thus in the present study, where we were interested in interfacial phenomena during high temperature deformation processing of a cobalt base alloy (Co-Cr-Mo), weak beam imaging was used to obtain a better understanding of the role of intergranular defects.
AEM of Grain-Boundary Precipitation in Type 304 Stainless Steels Containing N
Authors: Betrabet Hemant S. 
Published: June 2020

A systematic analytical electron microscope (AEM) study was conducted on a series of 18Cr-8Ni stainless steels in order to determine the effect of N additions on sensitization. This phenomenon is associated with intergranular carbide (Cr23C6) precipitation, and the subsequent Cr depletion of the surrounding region, and leads to susceptibility to intergranular corrosion and intergranular stress corrosion cracking. Sensitization can be retarded by reducing the C content of the steels, but this causes an unacceptable loss of mechanical properties. A better solution is to replace much of the C by N.A series of steels with varying N (0.04-0.25 wt%) and C (0.02-0.07 wt%) contents were studied in the AEM, and the results compared with electrochemical potentiokinetic reactivation (EPR) test data used to measure the degree of sensitization (DOS). EPR tests indicate that N additions up to 0.16 wt% retard sensitization, but above 0.16 wt% promote it, a result which does not agree with thermodynamic calculations of carbide precipitation which show that N slows the Cr23C6 growth kinetics, even at levels above 0.16 wt%.
Three-Dimensional Algebraic Reconstruction From Three Mutually Orthogonal Projections
Authors: Jiye Ximen , Zhifeng Shao 
Published: June 2020

The classic reconstruction problem is that of reconstructing a 3D object from its 2D projections /1-5/. It is also well known that the principal difficulty in solving this problem in electron microscopy is that a very large number of independent projections are normally required. Recently it has been shown /3,4/ that if we restrict our attention to binary or Boolean objects, far fewer projections are needed in order to obtain an approximate solution. 2-dimensional solutions of ID projections were demonstrated using only four views and 3-dimensional reconstruction of 2D projections were obtained by dividing the projections into identifiable slices.In the present paper, an algebraic reconstruction technique (ART) has been studied which uses three mutually orthogonal projections.
Cryo-Electron Microscopy and Image Analysis of SV40
Authors: Baker T. S. , Drak J. , M. Bina  
Published: June 2020

The discovery that the T=7 icosahedral capsid of polyoma virus is composed of 72 pentameric capsomers rather than 12 pentamers and 60 hexamers as predicted by constraints of quasi-equivalence has prompted an examination of SV40 virus by electron microscopy to determine whether the capsids of other members of the papovavirus family are similarly constructed.Thin layers of buffered aqueous solutions (∼4 mg/ml) of Simian virus 40 (strain WT776) were prepared for cryo-microscopy using recently developed procedures. Images of virus particles suspended in thin layers of vitreous ice over holes in the carbon support film and maintained at -170°C were recorded using minimal irradiation conditions. Figure 1 shows a typical field in which the frozen solution is similar in thickness to the virus particles (∼49 nm diameter). Particles appear to be excluded or squeezed away from the thinnest regions of solution (e.g., the clear region bordered by particles at the top of Fig. 1).
Identification Of G-Phase In Aged Cast CF 8 Type Stainless Steel
Authors: Bentley J. , Miller M. K. , Brenner S. S. , Spitznagel J. A. 
Published: June 2020

The microstructure of as-cast and aged CF 8 type stainless steel, used for the primary coolant pipes in pressurized light-water nuclear reactors, is being studied by analytical electron microscopy (AEM) and atom probe field-ion microscopy (APFIM). The phase transformations of the ferrite (∼19 vol % of the duplex structure) that occur after aging at 673 K for 7500 h are described by Miller et al. The present work deals with the identification of G-phase (prototype compound Ni16Ti6Si7) observed in the ferrite of aged material.In FIM images the precipitates had bright contrast, appeared roughly spherical, were ∼10 nm in diameter, and were present at a concentration of ∼1023 m-3. Atom probe selected area microchemical analyses of the central portion of five precipitates revealed that they were alloy silicides, Table 1.
TEM Investigation Of Hydrogen-Induced Phase Transitions In Stainless Steel
Authors: Minkovitz E. , Eliezer D. 
Published: June 2020

The role of martensitic phase transitions in the embrittlement of stainless steels by hydrogen has been one of persistent controversial theme studied during recent years. The unresolved question, concerns the role of hydrogen in hydrogen induced phase transformation of the γ(fcc) austenite to α‘(bcc) and ɛ (hcp) martensite phases in the fracture mechanisms. The purpose of this study is to report the results of a TEM analysis of martensitic phase transitions under conditions of high hydrogen fugacities such as cathodic polarization in the absence of any externally applied stress.The results demonstrate the appearance of hydrogen induced ɛ-phase in 316L steel (Fig. 1(b)). No evidence of the appearance of α'-martensite phase after hydrogen charging was found within the grains, however, α'-martensite was found in front of the crack tip and along the crack surfaces as a very fine-grained polycrystalline structure (Fig. 1(c)).
High-Resolution Electron Microscopy Studies of Supported Platinum Particles on ZSM-5 Zeolites
Authors: N. Acosta , E. Dominguez 
Published: June 2020

Supported small metallic particles (SMP) on zeolitic materials influence the catalytic properties of zeolites in several ways. Pt/ ZSM-5 containing 1.81 Pt in weight, were observed at high resolution conditions. The images of thin zeolite crystals were obtained and morphological and structural details were characterized. From the diffraction patterns some variations of the ratio c/a were found, caused possibly by local changes in Al concentration.The metal particles were found mostly distributed on the support crystalline phase as well as in areas presenting some structural defects; however the population of small metallic particles was greater in the crystalline zones. In addition, some contrast differences between particles seating on the same zeolite crystal were observed. These effects are attributed to different orientations for a given number of particles having the same diameter but different contrast (see figures 1a and 1b, particles A and B). Another interesting aspect, is the relative “transparency” of some particles such that crystalline planes of the zeolite (i.e. support) are visible trough the metal particle without any apparent perturbation of crystalline planes below them (see picture 3a).