bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yttrium Location and Chemical State in the Scale Formed On Y–Implanted 20%Cr/25%Ni/Nb Stabilised Stainless Steel in Carbon Dioxide at 825 C
Authors: Bennett M.J. , Desport J.A. , Labun P.A. 
Published: June 2020

Understanding how the so-called reactive elements improve the protection afforded to alloys by Cr203 and Al203 scales continues to be a major topic of high temperature oxidation research. Considerable progress has stemmed from studies on alloy surfaces modified by the controlled addition of these elements, such as yttrium and cerium, by ion implantation. The influence of yttrium ion implantation upon the oxidation behaviour of the technologically important 20%Cr/25%Ni/0.7%Mn/0.7%Si/Nb stabilised (20/25/Nb) austenitic stainless steel in carbon dioxide at 825°C has been the subject of extensive investigation. The implantation of 1017 yttrium ions cm-2 reduced the overall attack of the 20/25/Nb steel and maintained scale adhesion during extended exposure (6500h). These effects derived from the initial stage (<1h) of scale development.Further mechanistic understanding of the role of yttrium is critically dependent upon ascertaining both its location within the scale and its chemical state. This paper reports the preliminary results from an analytical electron microscopy examination of both back thinned(planar) and transverse sections of scales formed on yttrium implanted 20/25/Nb steel following 775 and 6500h oxidation in carbon dioxide at 825°C respectively.
Low-Voltage SEM Surface Studies of Microhardness and Topography of Ion-Implanted Cemented Carbides
Authors: Hefter J. , Oblas D.W. , Emma T.A. 
Published: June 2020

The modification of metal, ceramic, and composite surfaces by implantation with high-fluence ion beams is an area of active current research. An implantation depth on the order of 200 nm is typical, necessitating specialized techniques for the determination of the physical properties of the surface. For example, microhardness measurements by indentation techniques must be made using low-load conditions. Furthermore, the high fluences required for surface modification produce topographical changes which can affect the sample surface. Low-voltage scanning electron microscopy (LVSEM) has proven to be an excellent approach for evaluating low-load Knoop microindents as well as providing valuable information on the topographic changes due to implantation.EXPERIMENTAL. Samples were WC-6%Co cemented carbides tool inserts implanted perpendicularly to the surface with nitrogen at a fluence of 2x1017N2+/cm2. The implantation voltages were 90, 120, and 180 keV with corresponding implantation depths of 43, 57, and 84 nm. Microhardness measurements were made with a LEC0-M400LF tester at an indentation load of 10 g.
The Effects of Ion Implantation on the Surface Features of Inconel 600
Authors: Rubio John D. 
Published: June 2020

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.
Examination of Penetrable Volumes ("Pores") in A High-Performance Size-Exclusion Chromatography Matrix
Authors: Rigsby W. E. , Lingle W. L. , Kane D. J. O , Lee J. 
Published: June 2020

The separation of proteins by high performance size exclusion chromatography (HPSEC) is based upon the interaction of a protein, having an effective hydrodynamic radius, A, with "pores" in the HPSEC matrix material. Two different theoretical treatments (1, 2) yield widely different estimates of the mean "pore" radius, Ao, and have different prediction errors for A. A given "pore" can be characterized by the radius of the largest molecule that it can accomodate, AiIf A > Ai, the protein is excluded from the "pore".The "pore" diameter value quoted for TSK G3000 SW is 24.0nm (3). This is at variance with A0calculated by either treatment using the same HPSEC data: 28.4 ± 6.3nm (1) and 0.89 ± 5.4nm (2). From a knowledge of the "pore" volume it was calculated that approximately 50% of the total surface area of the HPSEC matrix corresponded to "pore". If Ae= 28.4nm, then ≥ 25% of the total surface area of the matrix should be occupied by "pores" with radii ≥ 28.4nm. These results prompted an investigation of the structure and size of "pores" in the HPSEC matrix material TSK G3000 SW.
Chemical Classification and Particle Sizing of Foundry Sands
Authors: DeMiglio D.S. 
Published: June 2020

Much progress has been made in recent years towards the development of closed-loop foundry sand reclamation systems. However, virtually all work to date has determined the effectiveness of these systems to remove surface clay and metal oxide scales by a qualitative inspection of a representative sampling of sand particles. In this investigation, particles from a series of foundry sands were sized and chemically classified by a Lemont image analysis system (which was interfaced with an SEM and an X-ray energy dispersive spectrometer) in order to statistically document the effectiveness of a reclamation system developed by The Pangborn Company - a subsidiary of SOHIO.The following samples were submitted: unreclaimed sand; calcined sand; calcined & mechanically scrubbed sand and unused sand. Prior to analysis, each sample was sprinkled onto a carbon mount and coated with an evaporated film of carbon. A backscattered electron photomicrograph of a field of scale-covered particles is shown in Figure 1. Due to a large atomic number difference between sand particles and the carbon mount, the backscattered electron signal was used for image analysis since it had a uniform contrast over the shape of each particle.
Planar Defects in Small Particles
Authors: Pérez R. , Avalos-Borja M. 
Published: June 2020

Transmission electron microscope techniques have been extensively used in the determination of the morphology of fine metallic particles. These techniques have been of particular importance in obtaining topographical information during particle growth and sintering. Thus, for example, it has been found that some of the most elementary forms consist of half cubo-octahedral units with (111) faces and (100) basis. Furthermore, full cubo-octahedral units have also been found, some of them showing stacking faults (SF) through the particles.It is important to point out that the characterization of this type of planar defects in small metallic particles has commonly been based on geometrical con. siderations. Additionally, the imaging conditions which have been used are the so-called weak beam (WB) diffraction conditions. Recent investigations have shown, on the other hand, that SF images under WB conditions present serious inconveniences, for example, contrast asymmetries in SF images which are not totally explained. Another difficulty with these WB fault images arises from twin boundaries which display image contrast similar to SF when a common reflection is strongly excited.
“Skeletal” Elements Involved in Prey Capture by the Antrarctic Foraminiferan Astrammina Rara
Authors: Bowser Samuel S. , DeLaca Ted E. 
Published: June 2020

Benthic foraminifera are considered primarily as “grazers” on bacteria, algae and other protozoans. However, in the benthic communities of the Ross Sea, Antarctica, field observations indicated that several species of agglutinated foraminifera (e.g., Astramina rara—shell ca. 2mm diameter) captured and digested larger metazoans (e.g., isopods such as Munna sp.—ca. 1cm in length). During prey capture the foraminiferan's reticulopodia (thin, anastomosing pseudopodia; Fig. 1) withstood the prey's vigorous escape efforts. We have attempted to identify the structural elements which impart the apparently high tensile strength of reticulopodia.To study the reticulopodial cytoskeleton, we fixed specimens of Astramina with 3% glutaraldehyde/0.1M PIPES supplemented with 0.04% tannic acid, followed by brief postfixation with 0.5% 0s04. The reticulopodial surface was examined in specimens fixed with 3% glutaraldehyde/0.1M PIPES supplemented with 1.5mg/ml ruthenium red, followed by 0.5% OsO4 containing 1.5mg/ml ruthenium red.
Na+/Ca2+ Exchange in Plasma Membranes and Microsomal Fraction of Brain Cortex
Authors: Coutinho O.P. , Norton W.N. , Carvalho C.A.M. , Carvalho A.P. 
Published: June 2020

The Na+/Ca2+ exchange system is one of the mechanisms responsible for regulating intracellular Ca2+ concentrations in neurons. However, the precise mechanism of Na+/Ca2+ exchange among synaptic plasma membranes and microsomes of neurons has yet to be resolved. The primary objective of the present investigation was to determine the specific transport properties with regard to Na+/Ca2+ exchange among neural synaptic plasma membranes and the various fractions of a microsomal density gradient separation.Synaptic plasma membranes were obtained by hypotonic disruption of sheep brain cortex synaptosomes (Fig. 1). Enzymatic characterization of the synaptic plasma membranes revealed high Na+/K+ ATPase activity and low RNA content, which suggest that the material is predominantly of plasma membrane origin. The most common constituents consisted of membrane fragments and resealed vesicles (Fig. 2).
Postnatal Development of the Feline End Bulb of Held
Authors: Larsen S. A. , Pappas George D. 
Published: June 2020

Maturation of the end bulb of Held (EBH) in the anteroventral cochlear nucleus (AVCN) was studied to determine what degree of plasticity is found in a synapse undergoing maturation, at the same time that the recipient neuron is increasing in size. Although the normal development of the neurons in the cochlear nucleus has been studied by Larsen and Morest, the normal development of the EBH has not been reported at the EM level.The EBH was studied in kittens ranging in age from birth to 60 days postpartum and in adult cats using electron microscopy and Golgi preparations with light microscopy. At selected developmental ages (birth, alternate days starting at the second day of life and extending throughout the first postnatal month, and adult), serial-sectioned electron micrographs of the EBH and its recipient neuron, the large spherical cell (LSC), were traced using computer-assisted morphometry.
Midgut Endocrine Cells in the Mosouito, Aedes Aegypti
Authors: Brown Mark R. 
Published: June 2020

The ultrastructure of a cell type in the insect midgut resembles that of peptide hormonogenic cells in the vertebrate gut. Also, vertebrate-like peptides such as pancreatic polypeptide (PP), glucagon, and insulin have been detected by immunoassays in insect midguts. Research was initiated to characterize the endocrine cells in the mosquito midgut, determine their immunoreactivity to antisera against vertebrate peptide hormones, and to identify organelles related to secretion of the hormones.Female mosquitos had access to water or a sucrose solution for 7 days. Midguts from the insects were processed for TEM by routine methods. To assess the role of lysosomal enzymes in the secretory process, midguts were incubated in cerium-based medium for acid phosphatase histochemistry. For immuno-cytochemistry, midguts were fixed in a modified Bouin's solution (pH 7.6) and 156 glutaraldehyde for 1 hr and embedded in epon/araldite. Thin sections of midgut on nickel grids were sequencially emersed in filtered rabbit antisera to PP, 1:1000 in 0.05M Tris (pH 7.6); anti-rabbit IgG, 1:20; and PAP, 1:200.
X-Ray Microanalysis of Hooks and Calcareous Corpuscles in Tapeworm Larvae
Authors: Rikihisa Yasuko , Fainter Lily K. , Lin Y.C. 
Published: June 2020

The Taenia taeniaeformis strobilocercus like other metacestodes has a unique hard structure: hooks and calcareous corpuscles. Previous studies on chemical analysis of the isolated hooks and calcareous corpuscles indicated that hooks are made of keratin-like protein and calcareous corpuscles contain calcium, phosphate and magnesium. In this study, x-ray microanalysis and the dot mapping procedure were carried out on these structures.L. taeniaeformis larvae were dissected from the liver of the infected rats. The larvae were fixed in mixture of 1.25% paraformaldehyde, 2.5% glutaraldehyde and 0.02% trinitrophenol in cacodylate buffer, pH 7.2, and postfixed for 1 hr in 1% osmium tetroxide in the same buffer. After dehydration in a graded series of ethanols, larvae were embedded in Poly/Bed 812 (Polysciences, Inc.).
Backscattered Electron Imaging of Colloidal Gold Markers For Leukocyte Surface Antigens
Authors: Harven Etienne de , Soligo Davide 
Published: June 2020

Markers for immuno-scanning electron microscopy had been, so far, selected for easy identification based on their distinctive shape (for example, haemocyanin, bacteriophage T4). These markers were always viewed in the secondary electron imaging (SEI) mode. Their size was not posing much of a problem of resolution for commercially available SEM, but was likely to prevent good labeling efficiency, due to steric hindrance phenomena. Higher labeling efficiency necessitates the use of markers of smaller size which, unfortunately, can rarely be unambiguously recognized in topographical SE images.To correlate antigenic distribution with small cell surface structures like microvilli or coated pits, markers of smaller size (i.e., in the 20 nm range) must be used and clearly identified on the surface of well preserved cells. With the availability of colloidal gold particles complexed with various ligands this became possible, particularly if the labeled cells are viewed in the backscattered imaging (BEI) mode of the SEM, therefore basing the identification of the marker on its atomic number contrast rather than on its topographical contrast.
Application of Backscattered Electron Imaging to the Study of Scavenger Receptor-Mediated Endocytosis by Sinusoidal Cells in Bone Marrow
Authors: Becker R.P. , Geoffroy J.S. 
Published: June 2020

The endothelial cells lining the postcapillary venous sinuses (sinusoids) in bone marrow take up colloidal gold-bovine serum albumin (BSA-Au) conjugates by means of a pathway involving coated pits and vesicles. Endocytosis of BSA- Au by these sinusoidal endothelial cells (sinusoidal cells) is rapid. Within one minute of pulse presentation (5 sec; intraaortic injection) with BSA-Au the probe is internalized and processed through pleomorphic endosomes to dense bodies known to be secondary lysosomes. By this time, 17% of the sinusoidal cell related BSA-Au is associated with the surface, while 83% is internalized, of which 2% is present in lysosomes. By four minutes, less than 8% of the observed BSA-Au is not internalized, the bulk being present predominantly in large pleomorphic vacuoles and dense bodies.That the endocytic process involves coated pits and vesicles prompts the suggestion that it may be receptor mediated. In order to investigate this possibility, biochemical and morphological studies were performed to determine the specificity and saturability of the putative receptor. Morphological analysis of TEM thin sections was aided by viewing large areas of the luminal sinusoidal cell surface in secondary electron (SEI) and backscattered electron imaging (BEI) modes of the scanning electron microscope.
Scanning Microscopy with Soft X Rays
Authors: Jacobsen C. , Kenney J. M. , Kirz J. , Rosser R. , Rarback H. 
Published: June 2020

Among the various forms of soft x-ray microscopy, scanning offers several advantages. It is capable of forming images with the lowest radiation dosage to the specimen. The image is recorded digitally, therefore quantitative information on specimen absorptivity as a function of position is immediately available. In addition it is possible to make quantitative comparisons of images formed at more than one wavelength. Based on such information, elemental maps can be formed.In collaboration with scientists from IBM and the National Synchrotron Light Source (NSLS), we constructed a scanning soft x-ray microscope that is operating on Beamline Ul5 of the 750 MeV VUV storage ring at the NSLS. The schematic diagram of the instrument is shown in Figure 1. The monochromatized beam of x-rays is collimated by a small pinhole. This small source is then further demagnified, using a Fresnel zoneplate, to form a focal spot, The specimen is mechanically scanned across this focal spot, and the x-rays transmitted by the specimen are detected by a flow proportional counter.
System For Producing 3-D Views in Contact Microradiography
Authors: Newberry Sterling P. 
Published: June 2020

Through advances in X-ray Lithography, Contact Microradiography at submicrometer resolution is now commonly practiced. As with other forms of microscopy, eg Projection X-ray Microscopy, a 3 dimensional view can substantially enhance the usefulness of Contact Microradiography. The author wishes to show how this is accomplished by reporting previously unpublished work which demonstrates these possibilities and by projecting how the technique may possibly be applied at submicrometer resolution.In the winter of 1949-50 while doing exploratory work on various forms of X-ray microscopy at General Electric, the author carried out comparative tests in his home laboratory on Contact Microradiography at accelerating potentials from 1.5 to 10 KV. A schematic of the demountable source and camera is shown in fig 1. The electron focusing system, independently discovered at about the same time by Ehrenberg and Spear, is simple and obvious. For this paper we are more concerned with the specimen holder and camera which are separated form the x- ray source by a thin beryllium window.
Use of Electron Microscopy in Plant Pathology: Abiotic Diseases
Authors: Krause C. R. 
Published: June 2020

To the casual observer it seems that abiotic diseases induced by nonliving or noninfectious agents, generally, have been ignored by plant pathologists in lieu of diseases caused by biotic agents (ie. fungi, bacteria, nematodes etc.) or viruses. The apparent lack of interest in abiotic disease problems is not entirely by choice nor by design. Inattention to abiotic disease has been fostered by inadequate techniques and methodologies required to study, characterize and quantify exogenous agents and their effects on host plants.Occasionally plant pathologists have difficulty in defining terms that describe various aspects of disease. In question are terms like healthy, diseased, normal and abnormal, that in the final analysis are concepts to be developed and carefully considered. Webster's Third New International Dictionary defines disease as “impairment of the normal state of the living plant body or of any of its components that interrupts or modifies the performance of the vital function of the organism, being a response to environmental factors, of specific infective agents, to inherent defects of the organism, or to combinations of these factors”. In essence, environmental factors produce environmental stress that, in turn, induce abiotic disease.
The Internal Structure of Coir (Coconut) Fiber
Authors: Barish Leo 
Published: June 2020

The source of commercial coir fiber (actually, a vascular strand) is the massive fibrous husk (3-5 cm thick) surrounding the coconut. This paper reports a SEM study of some aspects of this interesting fiber. The specimens were sputter coated with Au Pd and observed with 4 KV accelerating voltage.A cut cross section of a retted coir fiber is seen in Figures 1 and 2. A high degree of porosity is apparent; a core of the vascular or conductive bundle is seen surrounded by a large area of elongated sclerenchymatous cells which are cemented together into a composite with pectins or hemicelluloses.The sclerenchymatous cells may be separated by a maceration process, in this work a dilute solution of sodium hypochlorite. A bent, partially macerated coir fiber showing the configuration and orientation of the cells is given in Figure 3. A completely separated cell showing its general shape and pits is shown in a light photomicrograph in Figure 4.
The Influence of Suture Tautness on Wound Healing
Authors: Stone I.K. , von Fraunhofer J.A. , Masterson B.J. , Apkarian R.P. 
Published: June 2020

Wound closure by suturing is necessary to achieve continuity of epithelial covering, to prevent infection and to obviate loss of tissue fluids at the surgical site as well as being necessary in a variety of anastomoses and other procedures. The selection of sutures and the knotting regimen are central to this and these factors have been studied in depth by this group and others. An important aspect of suturing, however, is the tautness or tissue apposition force applied during wound closure although this has been largely neglected in the literature.The abdominal fascial muscle of rats was sutured by 00-gauge polydioxanone in a loose and a tight apposition mode. Tight closure was the normal suturing force applied by an experienced surgeon while loose wound apposition was achieved by inserting a 3mm dia. rod within the suture loop prior to securing the first throw and then removing the rod after wound closure was complete. After healing for 7 days, tissue at the wound site was sampled for tensile testing and for microscopic examination.
Analysis of the Structure of Paired Helical Filaments
Authors: Crowther R.A. , Wischik C.M. , Stewart M. 
Published: June 2020

The neurofibrillary tangles that occur in the brain in senile dementias of the Alzheimer type contain a class of filament with a distinctive morphology, the paired helical filament (PHF). Rather little definitive information is available about the structure or biochemical nature of the PHF. We have recently made a detailed ultrastructural analysis of PHFs. We will summarise here the results of that study, as the findings have an important bearing on the interpretation of the image reconstructions presented below.PHF enriched fractions were prepared from brains obtained post-mortem from cases with a clinical diagnosis of senile dementia of the Alzheimer type, confirmed histologically by the presence of large numbers of plaques and tangles in frontal and temporal cortex. The preparative protocol involved a series of differential centrifugations.
The Structure and Function Of Intermediate Filament Networks In Mammalian Cells
Authors: Goldman Robert D. , Goldman Anne , Jones Jonathan , Parysek Linda 
Published: June 2020

Intermediate filaments (IF) are major cytoskeletal components found in most mammalian cells. One of the most intriguing properties of IF is their high degree of variability with regard to their structural subunit proteins. This ariability is most evident when one compares the protein composition of IF from different cell types. For example, nerve cell IF (neurofilaments) contain the so-called neurofilament triplet proteins, while different epithelial cells contain two or more of the family of IF proteins called keratins. Indeed other cell types appear to have primarily a single subunit species such as in fibroblasts (vimentin, decamin) and muscle cells (desmin).In the specific case of the nervous system, there is very little information available on specific functions of neurofilaments, although they are thought to be involved in nerve cell shape formation and maintenance, as well as in axoplasmic transport and flow.