bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of Solute Trapping During Rapid Solidification of Binary Alloys
Authors: Mackey Terrence M. , Kelly Thomas F. 
Published: June 2020

BACKGROUNDThe very high crystal growth rates which can be produced during pulsed-laser melting provide the opportunity to study non-equilibrium solidification effects under well-defined experimental conditions. In particular, incorporation of solute into the growing crystal in excess of equilibrium solubilities may be achieved. This solute trapping may be pronounced at the highest crystal growth rates and may lead to the absence of microsegregation in non-planar solidification fronts.Crystal/liquid interface kinetics have been treated by considering the diffusive motion of atoms in the liquid. In this treatment, the crystal growth speed can never exceed the maximum diffusive speed of solute in the liquid, hence solute trapping is not possible. More recently, the collision-limited growth model indicates that for metallic and other simple molecular systems, the speed of sound in the liquid should be the upper limit to crystal growth rates. Consequently, in this latter model of solidification, the crystal growth rate can greatly exceed the maximum solute diffusive speed and solute trapping is possible.
Microstructures and Precipitation in a Rapidly Solidified Copper-Beryllium Alloy
Authors: Guha A. 
Published: June 2020

A study of direct strip cast copper-beryllium alloys is of interest to determine if enhanced properties could be obtained from rapidly solidified material compared to those of conventionally processed material. The present investigation was undertaken to characterize the as-cast microstructure of this material and to study the metastable phases which formed in this alloy as a result of precipitation from the rapidly quenched condition.The melt spinning technique was used to produce ribbons of a copper-beryllium alloy of nominal composition Cu-1.90wt% Be containing 0.25 wt% cobalt. The as-cast ribbon was approximately 0.1 mm thick and 12 mm wide. The Metglas Products Division of Allied Corporation provided the material. As-cast specimens were salt bath aged at 370 C for 5 min or 3 hours. Thin foils for transmission electron microscopy (TEM) were prepared from the melt spun ribbons by electrolytically thinning in a twin-jet electropolisher using a solution of 30% nitric acid in methanol at -30 C and 25 volts. The specimens were examined in a Siemens 102 transmission electron microscope operating at 125 kV.
Use of in Situ Delamination to Evaluate Fracture Micromechanisms in Graphite/Epoxy Laminates
Authors: Jordan William 
Published: June 2020

The goal of this research was to better define the deformation and fracture physics of delamination fracture in graphite/epoxy composite materials so that realistic models of the matrix dominated fracture could be developed. A key aspect of this was to develop techniques whereby real time delamination fracture could be observed in a scanning electron microscope.Macroscopic delamination tests were performed on an M.T.S. tensile machine operated in stroke control. The samples were 2.5 cm by 25 cm with a short starter crack in one end that was placed there when the sample was fabricated. This test procedure is described by Cohen. The test was designed so that the specimens could be tested in opening mode (mode 1) and with increasing amounts of shear up to pure mode 2 (in plane shear). Fracture energy results are shown in Table 1.
Identifying Sources of Sulfate Aerosols Reaching Whiteface Mountain, NY
Authors: Webber James S. 
Published: June 2020

INTRODUCTION“Acid rain” and “acid deposition” are terms no longer confined to the lexicon of atmospheric scientists and 1imnologists. Public awareness of and concern over this phenomenon, particularly as it affects acid-sensitive regions of North America, have increased dramatically in the last five years. Temperate ecosystems are suffering from decreased pH caused by acid deposition. Human health may be directly affected by respirable sulfates and by the increased solubility of toxic trace metals in acidified waters. Even man's monuments are deteriorating as airborne acids etch metal and stone features.Sulfates account for about two thirds of airborne acids with wet and dry deposition contributing equally to acids reaching surface waters or ground. The industrial Midwest is widely assumed to be the source of most sulfates reaching the acid-sensitive Northeast since S02 emitted as a byproduct of coal combustion in the Midwest dwarfs S02 emitted from all sources in the Northeast.
Mechanical Microthinning For TEM Specimen Preparation
Authors: Plummer H. K. , Shinozaki S.S. 
Published: June 2020

In two previous papers the technique of TEM specimen preparation using only the mechanical abrasion of boxwood tool and a dispersion of diamond powder in glycerin to thin the specimen has been presented with a number of examples shown. It is the intent of this paper to discuss additional details of the technique and to exihibit further examples where mechanical microthinning has been advantageous in obtaining useful information even in the presence of obvious mechanical damage.A.C.Faberge reported the use of teflon as a fine polishing lap. The grooved surface similar to that shown in Fig.1a, polished exceptionally well but after a short time in use the pocked surface, as seen in Fig.1b, was formed. in Fig.1a, polished exceptionally well but after a short time in use the pocked surface, as seen in Fig.1b, was formed.
Atomic Structure-Sensitive Magnetic Domain Structures of Thin Films
Authors: Tsukahara S. 
Published: June 2020

Transmission electron microscopy, TEM, that can serve for observation of both atomic and magnetic structures is useful to investigate structure sensitive magnetic properties. It is most effective when it is applied to thin films for which direct interpretation of the results is possible without considering additional effects through specimen handling for TEM use and modification of dimension dependent magnetic properties.Transmission Lorentz microscopy, TLM, to observe magnetic domains has been known for a quarter century. Among TLM modes the defocused mode has been most popular due to its simple way of operation. Recent development of TEM made it possible that an average instrument commercially available could be easily operated at any TLM modes to produce high quality images. This paper mainly utilizes the Foucault mode to investigate domain walls and magnetization ripples as the finest details of domain structure.
High-Resolution Observation of Twinning in Fe1-XS Crystals
Authors: Nguyen Thao A. , Hobbs Linn W. , Buseck Peter R. 
Published: June 2020

The ordering of iron vacancies in highly nonstoichiometric iron sulfide compounds (Fe1-xS, 0 ⩽ x ⩽ 0.125) at temperature below 425K give rise to at least two different superstructures and a number of possible planar defect configurations. These ordered iron vacancies and associated planar defects are believed to influence greatly the electrical and magnetic properties of Fe1-xS crystals. Extensive efforts, employing high resolution transmission electron microscopy, to characterize the ordering of iron vacancies and associated planar defects have been carried out by Nguyen and Hobbs, Pierce and Buseck, and Nakazawa, et al. In this paper we report the characterization of twin boundaries in iron sulfide crystal of composition nominally Fe9S10.Many beam lattice images of crushed synthetic Fe9S10 crystals were obtained in a top-entry JEM 200CX transmission electron microscope. Relevant electron optical parameters were Cs = 1.2mm; divergence half-angle α = 0.5mrad; and an objective aperture which allowed electron beams up to 5nm-1 to contribute to the final image.
Structure of the Si-GaAs Interface: Polar on Nonpolar Epitaxy
Authors: Mazur J.H. , Washburn J. , Henderson T. , Klem J. , Masselink W.T. , Fischer R. , Morkoç H. 
Published: June 2020

Possibility of growth of epitaxial lll-V (GaAs, InP, GaP, etc.) compound semiconductors on nonpolar substrates (Ge,Si) is of considerable interest from the view point of monolithic integration of lll-V optoelectronic and Si electronic devices. The growth of GaAs and AIGaAs layers on Si substrates is additionally attractive because of good mechanical strength and low cost of Si substrates. However, a principal difficulty in growing polar semiconductors on nonpolar substrates is that there are no preferential bonding sites for cations and anions in the first layer of growth, which can result in antiphase boundaries (APB’s) in addition to defects due to misfit (∼4% for GaAs on Si).In this work GaAs layers were grown on (100) Si substrates using procedures described elsewhere. The MBE growth started from a first deposition of As as a prelayer on the Si substrate followed by GaAs growth at 580°C. Cross-sectional TEM specimens were prepared using the same procedures as reported earlier for the case of Si-SiO2 cross-sections.
Ultrathin Platinum Crystal Surface Structures
Authors: Hines R. L. 
Published: June 2020

The importance of atom layer terraces or steps on platinum surfaces used for catalysis as discussed by Somorjai justifies an extensive investigation of the structure of platinum surfaces through electron microscopy at the atomic resolution level. Experimental and theoretical difficulties complicate the quantitative determination of platinum surface structures but qualitative observation of surface structures on platinum crystals is now possible with good experimental facilities.Ultrathin platinum crystals with nominal 111 orientation are prepared using the procedure reported by Hines without the application of a carbon backing layer. Platinum films with thicknesses of about ten atom layers are strong enough so that they can be mounted on grids to provide ultrathin platinum crystals for examination of surface structure. Crystals as thin as possible are desired to minimize the theoretical difficulties in analyzing image contrast to determine structure. With the current preparation procedures the crystals frequently cover complete openings on a 400 mesh grid.
Thickness Measurement by EELS
Authors: Egerton R. F. , Cheng S. C. 
Published: June 2020

Electron energy-loss spectroscopy offers a rapid method of estimating the local thickness of a TEM specimen. The best-known procedure requires only measurement of the integrated intensity IOunder the zero-loss peak and of the integral Itunder the whole spectrum (up to some suitable energy loss Δ). The thickness t is obtained from the formula:where λ(β) is the mean free path for inelastic scattering up to some angleβwhich is determined by the collection aperture (e.g. objective aperture in CTEM). In agreement with previous work we find that Eq. (1) is applicable over a wide range of thickness, typically 10-500 nm for EO= 100keV incident energy; see Fig. 1. Some deviation at large thickness might be expected as a result of the angular broadening produced by plural scattering, and because of contributions from electrons elastically scattered through angles greater thanβ.
Electron Beam-Induced Mass Loss in Freeze-Dried Tissue and Protein Samples
Authors: Cantino M.E. , Goddard M.K. , Wilkinson L.E. , Johnson D.E. 
Published: June 2020

Quantification in biological x-ray microanalysis depends on accurate evaluation of mass loss. Although several studies have addressed the problem of electron beam induced mass loss from organic samples (eg., 1,2). uncertainty persists as to the dose dependence, the extent of loss, the elemental constituents affected, and the variation in loss for different materials and tissues. in the work described here, we used x-ray counting rate changes to measure mass loss in albumin (used as a quantification standard), salivary gland, and muscle.In order to measure mass loss at low doses (10-4 coul/cm2 ) large samples were needed. While freeze-dried salivary gland sections of the required dimensions were available, muscle sections of this size were difficult to obtain. To simulate large muscle sections, frog or rat muscle homogenate was injected between formvar films which were then stretched over slot grids and freeze-dried. Albumin samples were prepared by a similar procedure. using a solution of bovine serum albumin in water. Samples were irradiated in the STEM mode of a JEOL 100C.
Mass Loss is Reduced at Liquid Helium Temperature
Authors: Lamvik M.K. , Klatt L.L. , Davilla S.D. 
Published: June 2020

Since mass loss is a fundamental limitation in electron microscopy and microanalysis of biological materials it is very valuable to understand the effect of specimen temperature on the mass loss process. An electron energy loss spectrometer has been added to the Duke University Cryomicroscope (fig. 1) to allow a general study of radiation damage effects in specimens held at liquid helium temperature.The reduction of specimen mass is measured by recording a long series of electron energy loss spectra with a Tracor-Northern TN-5400 analyzer, using the region integration feature of the analyzer to report the number of counts in the zero-loss and inelastic scattering regions of the spectrum.
Ultrastructure of the Cytoskeleton Purified From Macrophages
Authors: Washington L. P. , Browne J. , Igbo T. , Howard G. , Watson C. , Rabon L. 
Published: June 2020

The cytoskeleton of mammalian cells consists of families of protein fibers and networks which include microtubules (MT), microfilaments (MF), clathrin baskets (CB), intermediate filaments (IF), and the microtrabeculae lattice (MTL). The networks function in a coordinated, integrated manner to bring about movement/motility of intracellular organelle and membrane traffic. Although much is known about the structure and function of MT and MF, more knowledge is needed to elucidate the ultrastructure, assembly and function of intermediate filaments in non-keratinized mammalian cells.The objective of this study was to elucidate the ultrastructure of intermediate filaments isolated and purified from cultured mammalian cells.Macrophages were harvested from the peritoneal cavities of mice. Triton- insoluble fractions of IF were isolated from spread cultures using high salt and low ionic strength buffers. Purified IF were analyzed biochemically. Using poly acrylamide gel electrophoresis IF consists of 4-7 major bands in the molecular weight ranges of 14-90Kd3.
Intercisternal Substances of Plant Dictyosomes
Authors: Mollenhauer Hilton H. , James Morré D. 
Published: June 2020

Dictyosome cisternae are separated from one another by a minimum spacing of approximately 10 nm. Maintenance of this minimal spacing is due, presumably, to substances in the intercisternal region that bind one cisterna to the next. However, the intercisternal region appears in thin section much like the generalized ground substance of the cell and no distinct binding substances have been identified. Fibers bridging the intercisternal space have been reported but a role for them in the maintenance of dictyosome form has not been confirmed.The mechanism(s) for binding cisternae together can be broken rapidly by phosphotungstic acid or monovalent salts resulting in the disassembly of dictyosomes and separation of cisternae. Intact, or nearly intact, dictyosomes appear as stacks of highly fenestrated and/or tubular cisternae (Fig. 1). Coated vesicles are associated with the ends of peripheral tubules. Individual cisternae show a broad range of forms from predominantly tubular to predominantly flattened saccular with fenestrae (Fig. 2).
Ultrastructural Study of Rat Colon Following Psyllium Ingestion
Authors: Lightfoot F.G. , Grau L.E. , Cassidy M.M. , Tadvalkar G.R. , Vahouny G.V. 
Published: June 2020

Psyllium hydrophillic mucilloid is a natural gelling fiber consumed by a large population of our society. It is used as a bulk-producing laxative and in the treatment of gastrointestinal disorders such as “Irritable Bowel Syndrome”. The literature pertaining to the ultrastructural effects of this agent is sparse.This study documents morphological changes induced by psyllium. Animals fed a diet containing 2% psyllium for four weeks were subsequently sacrificed and processed for scanning and transmission electron microscopy. The colon contained fecal material combined with psyllium which conformed to the contour of the luminal surface. This mixture formed surface replicas of the intestinal mucosa. These replicas and their related colonic sites were processed for morphologic analysis.
Correlation of Vaginal Smears and Surface Structure in the Normal Estrous Cycle of Rats
Authors: Robert C. Kaufmann , Francis K. Khosho , Kofi S. Amankwah 
Published: June 2020

Few studies regarding the normal estrous cycle of rats exist in the literature. Only the estrous and diestrous portions of the cycle have been studied in any detail in the spontaneous cycle of the rat. Ultrastructural studies of proestrous have been limited to artificially induced cycles. These artificially induced cycles have been unable to account for all the findings on vaginal smears seen in spontaneous cycles. In this study, vaginal smear findings were correlated to surface ultrastructural findings in the four main phases of spontaneous ovulatory cycles in rats.Adult female rats of the Sprague-Dawely strain were used and sacrificed during different phases of their cycles. Daily vaginal smears (8-11 a.m.) of at least two consecutive cycles were used to determine the phase of the normal estrous cycle for each rat.
CTEM and HVEM of Rat Liver After Dosing With MDL 18719, A Serum Lipid Lowering Agent
Authors: Barnard Stephen D. , Barnhart James W. 
Published: June 2020

MDL-18719 which is (E)-3-[5-(1-oxododecyl)-2-furanyl]-2-propenoic acid has been shown to reduce serum cholesterol and triglycerides when administered orally to test animals. It is structurally related to RMI-14,514 a hypolipidemic drug reported to cause quantitative and qualitative alterations of hepatocellular peroxisomes (microbodies) when administered to rats.Male Sprague-Dawley rats were treated for 13 days with 0.125% MDL-18719 in the diet then sacrificed. A portion of the liver from each animal was immersed in cold 0.15 M cacodylate-buffered 4% paraformaldehyde, 0.05% dinitrodifluorobenzene, 4% glutaraldehyde fixative solution. Tissue sections 50μ thick were prepared and treated in catalase localization medium. The specimens were osmicated, dehydrated in graded acetones and embedded in epoxy resin. Additional liver specimens from the same rats were prepared in a similar fashion omitting the enzyme localization step. Thin sections were prepared for conventional transmission EM (CTEM), and 0. 5. thick sections were cut for high voltage EM (HVEM).
Techniques For The Preparation of Tissue Samples Containing Injectable Polymer Microcapsules
Authors: Visscher G.E. , Robison R. L. , Argentieri G. J. 
Published: June 2020

The use of various bioerodable polymers as drug delivery systems has gained considerable interest in recent years. Among some of the shapes used as delivery systems are films, rods and microcapsules. The work presented here will deal with the techniques we have utilized for the analysis of the tissue reaction to and actual biodegradation of injectable microcapsules. This work has utilized light microscopic (LM), transmission (TEM) and scanning (SEM) electron microscopic techniques. The design of our studies has utilized methodology that would; 1. best characterize the actual degradation process without artifacts introduced by fixation procedures and 2. allow for reproducible results.In our studies, the gastrocnemius muscle of the rat was chosen as the injection site. Prior to the injection of microcapsules the skin above the sites was shaved and tattooed for later recognition and recovery. 1.0 cc syringes were loaded with the desired quantity of microcapsules and the vehicle (0.5% hydroxypropylmethycellulose) drawn up. The syringes were agitated to suspend the microcapsules in the injection vehicle.
Heavy Atom Cluster Labeling of Biological Specimens
Authors: Lipka J.J. , Hainfeld J.F. , Wall J.S. 
Published: June 2020

The Brookhaven STEM is capable of resolving single heavy atoms deposited on thin carbon films with a beam dose > 103 el Å-2 Single heavy atoms, therefore, are unsuitable as fiducial markers on unordered biological specimens because of the high beam dose required for direct visualization. Heavy metal-clusters or heavy metal-containing complexes have been resolved at much lower beam doses, as low as 30 el Å-2, and therefore may be useful as directly visible labels.The polyamine undecagold (11-Au) cluster ion, [(p-H2NCH2C6H4)3P]7 Au113+, has been used to covalently label the carbohydrate sites of the glycoprotein complex of human haptoglobin hemoglobin (Hp˙Hb) by a route which should be general for any glycoprotein with oxidizable carbohydrate residues. Proteins with reactive lysine residues have been covalently 11-Au labeled by the reactions noted in Scheme 1.
Alzheimer's Paired Helical Filaments Contain Insoluble Cytoskeletal Elements
Authors: Gambetti P. , Perry G. , Autillo-Gambetti L. 
Published: June 2020

Neurofibrillary tangles (NFT) are one of the major pathologic lesions of Alzheimer's disease. These neuronal inclusions are predominantly composed of paired helical filaments (PHF), which consist of two 10 nm filaments winding around each other with an approximately 80 nm periodicity. Besides PHF, NFT comprise also 15 nm filaments, 10 nm filaments which are probably neurofilaments, microtubules and granular material. At variance with the neuronal cytoskeleton, PHF are insoluble in ionic detergent.Studies at the light microscope level have shown that NFT have unique antigenic determinants as well as determinants in common with elements of the normal neuronal cytoskeleton such as neurofilaments and microtubule-associated proteins. The present study uses immunocytochemistry and cytochemistry at the electron microscope level to assess which NFT component contains these determinants and whether these antigenic determinants are soluble in an ionic detergent.
Electron probe x-ray microanalysis of subcellular ion transportin situ
Authors: Somlyo Avril V. , Somlyo Andrew P. 
Published: June 2020

Electron probe x ray microanalysis [EPMA] provides quantitative information within a single spectrum about elements of biological interest with atomic number of 11 or greater. Therefore, the transport of ions and their accompanying co and counter ions across organelle membranes can be studiedin situby sampling within and adjacent to the intracellular organelle of interest under resting and stimulated conditions.EPMA is based on the fact that the ionization of atoms by fast electrons generates x rays having energies characteristic of the excited atoms. The interaction of incident fast electrons with atomic nuclei generates a background of continuum x rays. Elemental quantitation of ultra thin sections with EPMA is generally based on the linear relationship between elemental concentrations and the ratio of the number of characteristic/continuum. The use of this principle, together with the appropriate standards for calibration, has been the most successful approach for quantitative biological EPMA. The spatial resolution of EPMA at present is better than 10 nm and the practical limit of sensitivity for detecting calcium, (albeit with high electron dose), is approximately 0.3 mmol/kg dry wt. Two modes of data collection are utilized: fixed probe analysis of a region of interest or a scanning probe mode, where an x ray spectrum is collected at each picture point, to obtain quantitative elemental x ray maps. To preserve the morphology and thein vivodistribution of diffusible elements, we prepare specimens by rapid freezing in sub cooled Freon or, more recently with a Lifecell CF100 metal are mirror device; thin sections cut at -130 °C to -160 °C on a Reichert cryoultramicrotome. Msec time resolution of physiological are events can be achieved by freeze trapping.