bluuebunny/crossref_metadata_2025_split huggingface dataset:
STEM microanalysis of precipitates in a nickel-base superalloy
Authors: Craven A.J. , Menzies R.G. , Bricknell R.H. 
Published: June 2020

In a powder compacted nickel-base superalloy used in high temperature applications, a group of metal carbides (MC) 200-600nm in diameter were observed. Many of these precipitates contained an inner particle (20-60nm in diameter) which will be referred to as the nucleus. In addition to the commercial interest in such a metallurgical system, the identification of the two types of particles provides an interesting problem in microanalysis. Currently two analytical techniques are available on the VG Microscopes HB5, scanning transmission electron microscopes (STEM); energy dispersive X-ray analysis (EDX) and transmission electron energy loss spectroscopy (TEELS).When analysing thinned foils there is the problem of interference from a layer of matrix on the precipitate or from the outer precipitate surrounding the nucleus. Even if the foil is thinned to the extent that layering effects are removed EDX still suffers two drawbacks; (i) Inadequate collimation leads to system peaks following general specimen illumination; (ii) X-rays and electrons leaving the area analysed generate characteristic peaks from adjacent regions.
Micro Auger analysis using a field emission source
Authors: Bovey P.E. , Wardell I.R.M. , Williams P.M. 
Published: June 2020

The use of a high brightness field emission source holds clear promise in the area of micro Auger analysis of surfaces. The high current density and small probe diameter obtainable from the field emitter (30 n A into 300Ǻ, for example) offer the possibility of recording Auger spectra from areas less than 300Ǻ, as previously demonstrated . Furthermore, the ultra high vacuum technology necessary for a reliable field emission source, is wholly compatible with the type of vacuum experimental vessel customary in surface analysis applications.We describe here results obtained with an HB50A Auger Microprobe in which an environmental cell, introduced on a bellows movement into the experimental vessel, permits heating to 800°C in an atmosphere of 0.1 torr of gas. The sample under study was pure polycrystalline iron.This was reacted with methane at 750°C in situ for 12 hours. The carbon resulting from cracked methane, dissolved in the iron to such an extent that, on cooling to 600˚C, precipitation occured. Figure 1 shows an SEM image of a characteristic precipitate, recorded with the sample held at 600˚C at a magnification of 2,000 X.
A quantitative approach to inner shell losses
Authors: Leapman R.D. , Rez P. , Mayers D.F. 
Published: June 2020

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as
Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy
Authors: Zaluzec N. J. 
Published: June 2020

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation
Plastic deformation of θ ' in Al-4%Cu alloy
Authors: Bhat Shrikant P. 
Published: June 2020

deformation behavior of Al-Cu alloys aged to contain θ ' has been the subject of many investigations (e.g., Ref. 1-5). Since θ ' is strong and hard, dislocations bypass θ ' plates (Orowan mechanism) at low strains. However, at high strains the partially coherent θ ' plates are probably sheared, although the mechanism is complex, depending on the form of deformation. Particularly, the cyclic straining of the bulk alloy is known to produce gross bends and twists of θ '. However, no detailed investigation of the deformation of θ ' has yet been reported; moreover, Calabrese and Laird interpreted the deformation of θ ' as largely being elastic.During an investigation of high temperature cyclic deformation, the detailed electron-microscopic observation revealed that, under reversed straining conditions, θ ' particles are severely distorted--bent and twisted depending on the local matrix constraint. A typical electronmicrograph, showing the twist is shown in Fig. 1. In order to establish whether the deformation is elastic or plastic, a sample from a specimen cycled at room temperature was heated inside the microscope and the results are presented in a series of micrographs (Fig. 2a-e).
Application of an analytical electron microscope to surface deformation and wear research
Authors: Carpenter R.W. 
Published: June 2020

A primary objective of surface deformation and wear research is the correlation between surface deformation and wear made under different loading and environmental conditions with the near-surface deformation substructure in the material. The multiple imaging modes of an analytical electron microscope, TEM/STEM and SEM, together with single surface thinning methods should permit direct examination of both the external worn surface and immediately underlying deformation substructure in one instrument.This method eliminates the inconvenience of using two instruments to characterize surface and subsurface regions and the problem of disregistry between areas examined in two instruments. This paper presents first results using the method to examine stylus tracks on aluminum.Annealed, flat 3-mm-dia disks of commercial purity (1100 grade) A1 were electropolished to a flat specular surface on one side and then put in a ruling device for surface deformation. Straight wear tracks were ruled on the polished surface using a smooth hemispherically shaped stylus having a 2.5μm radius.
Observation of initial cracking in hydrogen-charged pure iron
Authors: Takeyama T. , Takahashi H. 
Published: June 2020

It is considered that hydrogen atoms in iron dissolve interstitially in the matrix, segregate at some lattice defects, are absorbed at the interface of foreign atoms or inclusion, and/or precipitate as a gas phase. This precipitation of gaseous hydrogen in iron causes the formation of void, microcrack and blister, which affects the mechanical properties of the iron. Fracture due to hydrogen embrittlement may be caused by a crack initiation and growth, and propagation. It is obvious that this fracture depends on the diffusion of hydrogen atoms through the iron. However, the mechanism of hydrogen embrittlement cracking has not been fully explained.The aim of the present work was to investigate the microcrack and microvoid generated by the precipitation of hydrogen charged by cathodic method.Pure iron was cold-rolled to a sheet of 0.5mm thickness. After cutting, specimens were annealed at 700°C for one hour in a vacuum of 10-5torr. The grain size was l0̴20 μm. The specimens were charged with hydrogen by applying cathodic potentials in electrolytic cells containing O.1N-H2SO4 with the addition of 250 mg/ℓsodium arsenite to act as a recombination poison.
Freeze-fracturing and replication at -260 C
Authors: Gross H. , Müller T. , Wildhaber I. , Winkler H. , Moor H. 
Published: June 2020

In order to quantify the information contained in metal replicas we chose periodic test specimen. The so-called HPI-layer (a sheet-like protein monolayer) of the bacterium Deinococcus radiodurans was examined by freeze-drying (“surfaces“) and the paracrystalline regions of the plasmalemma of baker's yeast were studied by means of freeze-fracturing (“fracture faces“). 2-D periodic structures allow the application of digital image processing (Fourier filtration, correlation averaging, analysis of the granularity) which greatly facilitate assessment of methodological processes.After freeze-drying and Pt/C- and Ta/W-shadowing we achieved image averaged details at the molecular level on both surfaces of the HPI-layer (Figs. 1-5). Unidirectional shadowing (Figs. 1-3) gives information about the surface properties (mainly in the third dimension) whereas rotary shadowing (Figs. 4,5) provides information about the lateral arrangement and the symmetry of the lattice subunits. When the specimen is thin and a relatively large proportion of its surface is accessible to the evaporated material, as in the case of the HPI-layer, a 3-D model can be produced easily by combining the shadowing data obtained on both surfaces (Fig. 7).
A simple procedure for obtaining clean sections for TEM
Authors: Chien K. , Van de Velde R. , Heusser R. 
Published: June 2020

After ultrathin sections are cut, contamination can result not only from the staining and rinsing solutions but also from improper handling technique. A new procedure is described which is simple to perform and enables one to obtain cleaner sections for EM examination.Commercially available instruments and materials (Ted Pella, Inc.) are used for this procedure: A Pelco Vacuum Device (fig. 1) is connected by flexible plastic tubing to an adaptor which can accept various sized metal needles. The vacuum can be finger-tip controlled at the aperture within the adaptor. Cohen-Pelco Tabbed Grids are used for section support. A flat, silicone rubber grid holder is used for staining and rinsing of several grids at one time.
Nucleoprotein: DNA hybridization as a preparative method to isolate specific eukaryotic genes as chromatin
Authors: Workman J.L. , Langmore J.P. 
Published: June 2020

Determining the structure and protein composition of chromatin in different states of genetic activity is critical for understanding eukaryotic gene expression. Very little is known about the dependence of chromatin structure upon the sequence or transcriptional activity of the DNA, except in the 2 cases in which particular genes can be isolated from the remainder of the chromatin. In the first case, active ribosomal RNA genes have been shown by EM to contain structurally altered nucleosomes. EM has also shown that SV40 minichromosomes possess a DNA sequence that is devoid of nucleosomes. Clearly, EM is capable of resolving sequence and activity specific features of chromatin, but is limited by the number of genes that have been purified.We have adapted methods of nucleic acid enzymology and hybridization in order to isolate specific genes as intact chromatin. Our methods are DNA sequence specific and thus are generally applicable to isolating a chosen gene at different points in development, differentiation and growth.
High-voltage electron microscopy of insect capsule viruses
Authors: Mazzone H.M. , Wray G. 
Published: June 2020

The High-Voltage Electron Microscope (HVEM) affords the researcher an opportunity to study insect virus inclusion bodies, intact, without resorting to physical thin-sectioning or chemical degradation procedures. In this manner polyhedral inclusion bodies, isolated from insects infected with nuclopolyhedrosis viruses (NPVs) were observed with the HVEM, and the numerous viruses lying internally, clearly delineated.In the present report we used the HVEM to study, in whole mount, another type of insect virus inclusion body, that from the capsule (granulosis) viruses of two hosts, the fall webworm, Hyphantria cunea (Drury) and the yellow wollybear, Diacrisia virginica (Fabricius). The insect capsule viruses, like the NPVs, are characterized by a crystalline protein matrix which occludes enveloped, rod-shaped virus particles. Whereas the inclusion bodies of NPVs contain a number of virus particles in each inclusion body, those of the capsule viruses contain, generally, only one virus particle in each capsule or granule.
Morphometric SEM study of the effects of ACTH on endothelial fenestrae in the rat adrenal cortex
Authors: Curtis J. , Schwartz K. S. , Apkarian R. P. 
Published: June 2020

A scanning electron microscope (SEM) study was made of the effect of adrenocorticotropic hormone (ACTH) on the size and numbers of fenestrae/unit area in the capillary endothelium of the zona fasciculata (ZF) of the rat adrenal. The stimulatory effect of ACTH on cholesterol uptake via high density lipoproteins in the rat and evidence for the secretion of glucocorticoids by exocytosis of lipid droplets described by Rhodin suggest that endothelial change may accompany these transport phenomena.Twelve rats received two Dexamethasone (DEX) ip injections (25 μg DEX/100 g body wt.), the first at 8 PM and the second at 8 AM the next day, to inhibit the release of endogenous ACTH by the anterior pituitary. The animals were then divided into two groups. Six animals received only saline vehicle and six rats received ACTH (100 ng/100 g body wt.).
Scanning electron microscope observation of the endings of the odontoblast process in human and animal dentin
Authors: Chernecky R. , Smith D.C. 
Published: June 2020

Recent SEM studies have demonstrated that the odontoblast process occupies the dentinal tubules of fully formed dentin, up to the dentinal-enamel junction (Maniatopoulos and Smith, 1982, 1983; Yamada et al, 1983). There is however, still debate on how the processes end at the dentinal-enamel or dentinal-cementum junction. It was the purpose of this study to investigate the endings of the odontoblast process in these areas.Materials and Methods:Freshly extracted human and rat teeth were a) split mechanically by the use of a mallet and a chisel, b) decalcified in 18% E.D. T.A. for 6 hr, c) washed in PBS for 1 hr, d) digested with bacterial collagenase for 2 hr at 37°C, e) fixed in 2% glutaraldehyde with 0.1M cacodylate buffer for 12 hr, f) post-fixed in 1% osmium, g) dehydrated in a graded series of aqueous alcohol. All solutions had 0.1M sucrose added to maintain almost near physiological osmolarity, ph was 7.4. Then specimens were routinely processed for scanning electron microscopy (ISI-60).Results:Odontoblast processes were observed in the inner, middle and outer part of dentin, up to the dentin-enamel or dentino-cementum junction, in all specimens examined. These observations verify the findings of previous workers in the field. At the area of mantle dentin the odontoblast processes were observed to be divided, giving two or more terminal branches (schematically shown in fig 1-3). In this area the processes were observed to end forming spherical structures (fig 1-9). These spherical endings of the odontoblast processes were observed after the total removal of the enamel and part of the mantle dentin through demoralization. These structures were observed on the surface of the dentin in close relation to the openings of the dentinal tubules (fig 4,5,8 and 9) and presenting a true continuation to the odontoblast processes (fig 6,7). In some specimens (fig 5,6) spheres were collapsed probably due to specimen dehydration following fracture and SEM preparation, whereas in other specimens they appeared intact (fig 8,9). Some endings (fig 8,9) showed smaller spherical projections on the main sphere body. The spherical endings of the odontoblast processes were observed in both crown and root mantle dentin.Conclusions:The results suggest that i) the odontoblast processes occupy the full length of fully developed dentin in both human and rat teeth, up to the dentino-enamel or dentino-cementum junction, ii) The odontoblast processes end in the mantle dentin in the form of spherical structures.Acknowledgement:The authors are grateful to Dr. M. Sigal for the initial preparation of the specimens.
Scanning electron microscopy of freeze-fractured prescapular lymph node of caprine
Authors: Faroon O. , Al-Bagdadi F. , Snider T. G. , Titkemeyer C. 
Published: June 2020

The lymphatic system is very important in the immunological activities of the body. Clinicians confirm the diagnosis of infectious diseases by palpating the involved cutaneous lymph node for changes in size, heat, and consistency. Clinical pathologists diagnose systemic diseases through biopsies of superficial lymph nodes. In many parts of the world the goat is considered as an important source of milk and meat products.The lymphatic system has been studied extensively. These studies lack precise information on the natural morphology of the lymph nodes and their vascular and cellular constituent. This is due to using improper technique for such studies. A few studies used the SEM, conducted by cutting the lymph node with a blade. The morphological data collected by this method are artificial and do not reflect the normal three dimensional surface of the examined area of the lymph node. SEM has been used to study the lymph vessels and lymph nodes of different animals. No information on the cutaneous lymph nodes of the goat has ever been collected using the scanning electron microscope.
Heavy-metal compartmentalization by algal cells
Authors: Jensen T.E. , Rachlin J.W. , Baxter M. , Warkentine B. , Jani V. 
Published: June 2020

A key question in biology is to understand how cells exposed to heavy metals mitigate the metal's toxic effects. In an attempt to answer this question we have been investigating the effects of heavy metals on cells, especially the possible compartmentalization or sequestering mechanism they may have which would reduce the toxic effect.A variety of cyanobacteria (Cyanophyceae) and eukaryotic algae (Chlorophyceae and Bacillarophyceae) were studied to determine if metal binding takes place and if so if the metal is compartmentalized in the cells. Metals used in the study included Ba, Cd, Co, Ca, Hg, Mg, Mn, Ni, Pb, Sr and Zn. Cells were exposed to different concentrations of the metal for varying time periods and then air dried onto formvar coated nylon grids. Cells were located using the STEM mode (dark field setting but with a bright field image) of a JOEL U-3 SEM. The SEM was operated at 25 KV and 4X10-10 A beam current.
Measurements of the range of secondary electrons in low-Z materials
Authors: Muray A. , Isaacson M. , Kirkland E. 
Published: June 2020

Previously, calculations of the resolution of SEM secondary electron images due to the escape depth of these electrons utilized Monte-Carlo calculations to simulate the “edge brightness effects” seen in high resolution magnification images obtained with small probe sizes (e.g.,). Similar Monte-Carlo calculations have been made to try to deduce the energy dissipation profiles in PMMA due to secondary electrons. We are trying to develop a simple analytical model which might allow us to get a better feel for the salient features with which the secondary electrons limit the pattern size in microfabrication and spatial resolution in the SEM.For our initial measurements, we have fabricated the structure shown in figure 1. The thickness of both the PMMA and Si substrate are less than one mean free path for inelastic scattering (of 100 keV electrons) thick. A 10 Å diameter beam of convergence angle of 15 mrad is incident normal to the sample surface.
Filler material in medical-grade silicones
Authors: Greer R. T. 
Published: June 2020

Medical-grade silicone rubber is a widely utilized biomaterial. As is the case for most rubbers, fillers are used to give additional strength to the polymer. The nature of the filler is of interest in the development, fabrication and improvement of medical devices where blood and tissue compatibility may be altered by submicroscopic structure and phase distribution. The medical-grade silicone rubbers are of two types, heat-vulcanizing and room-temperature-vulcanizing (RTV).The filler used in heat-vulcanizing types is fumed silica of a small particle size of the order of 0.03 µm and smaller (0.007 µm; 0.012 µm; Cab-0-Sil®, Cabot Corp., Boston, MA 02110). It is made by a vapor phase process (hydrolysis of silicone tetrachloride at 1100° C ), producing a colloidal amorphous silica (SiO2). It is generally classified as a fumed silica due to its production at a high flame temperature. Fume-process silicas give the highest degree of reinforcement of silicone rubber compared with finely divided silicas made by a wet process (aerogels), or with diatomaceous earth.
Cleavage of layer crystals
Authors: Hines R. L. 
Published: June 2020

Layer crystals such as graphite, molybdenite and mica have a variety of uses in electron microscopy when lamella can be easily prepared with clean surfaces, uniform thickness, high crystal perfection and tolerable waviness. The most common use of thin crystals is as a featureless support for high resolution microscopy. Crystals can also be used as phase plates and to reduce radiation damage. Crystals have long been used to display high resolution images and can be used to accurately characterize electron microscope operational parameters.Crystals for any of the uses described above can in principle be prepared by any technique although their usefulness may be severely limited by nonuniform thickness, surface contamination and sparse fields. Crystals prepared by cleavage with pressure sensitive tape give useful supports with simple equipment and require less than 20 minutes of preparation time for the crystal lamellae mounted on one grid.
AEM investigation of ZrO2 solid solution formation in ZrO2/mullite composites
Authors: Dinger T. R. 
Published: June 2020

Zirconia (ZrO2) is often added to ceramic compacts to increase their toughness. The mechanisms by which this toughness increase occurs are generally accepted to be those of transformation toughening and microcracking. The mechanism of transformation toughening is based on the presence of metastable tetragonal ZrO2 which transforms to the monoclinic allotrope when stressed by a propagating crack. The decrease in volume which accompanies this transformation effectively relieves the applied stress at the crack tip and toughens the material; microcrack toughening arises from the deflection of a propagating crack around sharply angular inclusions.These mechanisms, however, do not explain the toughness increases associated with the class of composites investigated here. Analytical electron microscopy (AEM) has been used to determine whether solid solution effects could be the cause of this increased toughness. Specimens of a mullite (3Al2O3·2SiO2) + 15 vol. % ZrO2 were prepared by the usual technique of mechanical thinning followed by ion beam milling. All observations were made in a Philips EM400 TEM/STEM microscope fitted with EDXS and EELS spectrometers.