bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of Longitudinal Sections of Sickle Hemoglobin Fascicles
Authors: Bradlow Ann R. , Carragher Bridget , McDade William A. , Josephs Robert 
Published: June 2020

In vivo, deoxyhemoglobin S fibers associate into bundles, or fascicles. It is the formation of these bundles within red blood cells which leads to the clinical manifestations of sickle cell disease. A similar phenomenon is observed in vitro. Fascicles are initially small and poorly ordered but, with time, become progressively larger, more tightly packed and more highly ordered. The most tightly packed fascicles display crystalline order and form “crystals of fibers”. We have constructed computer generated models of longitudinal projections of crystalline fascicles of sickle hemoglobin (HbS) fibers. A comparison of the models with electron micrographs provides a means of accurately determining the three dimensional packing arrangement of fibers and the nature of the fiber-fiber interactions within fascicles.Electron micrographs of longitudinal sections of well ordered fascicles reveal a number of characteristic views, one of which is shown in figure 2a. The different views observed in the micrographs arise because of differing orientations of fascicle sections relative to the angle of projection. This was demonstrated by experiments in which the specimen was tilted about its long axis. Different views could be interconverted by varying the angle of tilt.
Further Observations on the Fine Structure of “Tubular Aggregates”
Authors: Montpetit V.J.A. , Dancea S. , Skinner C.R. , Kawahara H. 
Published: June 2020

Accumulations of densely packed long straight tubules, usually at the periphery of skeletal muscle fibers, have been referred to as “tubular aggregates”. They have been described mainly in type II muscle fibers and do not appear to be associated with a specific disease entity. The nature and origin of the abnormal tubular structures remain enigmatic. Some authors have postulated that they arise from lateral sacs of sarcoplasmic reticulum while others maintain that a mitochondrial or sarcolemmal origin is more plausible. This unsettled dispute over their origin prompted us to pursue a more detailed ultrastructural study of their components.A fifty-three year old male presented with a short history of pains in the quadriceps muscles and bitemporal areas. A chronic periarteritis of uncertain etiology was present in the temporal artery and quadriceps muscle. Cryostat sections of the latter revealed numerous subsarcolemmal masses of material which stained basophilic with hematoxylin and eosin, bright red with modified trichrome and intensively with the NADH tetrazolium reductase reaction.
Quality films from carbon fiber evaporation for thorough coverage of TEM grids
Authors: Tempel N. , Ledbetter M. C. 
Published: June 2020

Carbon films have been a support of choice for high resolution electron microscopy since the introduction of vacuum evaporation of carbon. The desirable qualities of carbon films and methods of producing them has been extensively reviewed. It is difficult to get a high yield of grids by many of these methods, especially if virtually all of the windows must be covered with a tightly bonded, quality film of predictable thickness. We report here a method for producing carbon foils designed to maximize these attributes: 1) coverage of virtually all grid windows, 2) freedom from holes, wrinkles or folds, 3) good adhesion between film and grid, 4) uniformity of film and low noise structure, 5) predictability of film thickness, and 6) reproducibility.Our method utilizes vacuum evaporation of carbon from a fiber onto celloidin film and grid bars, adhesion of the film complex to the grid by carbon-carbon contact, and removal of the celloidin by acetone dissolution. Materials must be of high purity, and cleanliness must be rigorously maintained.
Formation process of silicide at Pt-Si (111) interface
Authors: yokota Y. , Hashimoto H. 
Published: June 2020

The initial stage of the reaction process forming the platinum silicide at Pt/Si (111) interfaces have been investigated by a high resolution electron microscope in both “flat-on” [1] and “cross-sectional” mode.First, platinum of 11 nm thickness was deposited on a Si (111) wafer. For observing the specimen in “flat-on” mode, the top surface and edge of the specimen were covered by paraffin and etched chemically using CP-4 reagent from backside. The specimen for observing in “cross-sectional” mode was prepared as follows. The Si wafer was cut into slips of 3mm width. After stacking 4 to 6 slips together with epoxy resin, the stacks were sliced to a thickness of 0.3-0.4mm by a diamond saw. The slices were mechanically polished to a thickness lower than 0.05mm and then thinned by Ar ion beam.The formation process of platinum silicide (PtSi) was observed in a cross-sectional specimen.
The formation of a gold/silicon alloy by electron-beam heating of codeposited thin films
Authors: Sharma R. , Robison W. , Eyring L. 
Published: June 2020

Studies of metal-semiconductor interactions have been of great interest in recent years because of the need to understand the behavior of semiconductor device junctions. The gold-silicon system has been studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). An amorphous gold si 1icide is assumed to form at the metal-semiconductor interface. Different Au silicides are reported to be formed after heat treatment of Au films on a silicon substrate in ultra-high vacuum. Similar results have been observed for bulk samples by x-ray diffraction. The exact process of the diffusion of reactants and structure of the silicides formed is still being debated. Studies of the system by electron diffraction and high resolution microscopy is reported here.Thin films of Au/Si (200-300 Å) were deposited on a (100) NaCl crystal face by evaporating Au and Si simultaneously at the same rate in a vacuum of 10-9 Torr at room temperature.
The interaction between basal-twin boundaries and a glassy phase in α-Alumina compacts
Authors: Simpson Yonn Kouh , Carter C. Barry 
Published: June 2020

Understanding the nature of glass/crystalline interfaces is not only of fundamental scientific interest but is directly relevant to the liquid-phase sintering of polycrystalline ceramics such as α-alumina. Faceting behavior of alumina in the presence of SiO2 glass has been of much interest in the field of sintering with respect to the grain growth and the grain boundary mobility during sintering. The study of grain boundaries containing a glassy phase in alumina compacts is difficult however, since many of the TEM techniques presently available for the identification of a glassy phase at grain boundaries can give ambiguous results due to grain boundary grooving. A method for systematically studying glassy / crystalline interfaces without such ambiguity is therefore needed. Part of this study of the interaction of grain boundaries in alumina with an anorthite-based glassy phase is presented here.Previous systematic studies4 of different low-index surfaces of single crystal alumina showed that there is strong anisotropy in the faceting behavior of alumina and in the mobility of these facets in the presence of an anorthite-based glassy phase.
Cross-section TEM observation of Ba2YCu3O7-x thin film on SrTiO3
Authors: Tomita Masato , Hayashi Takayoshi , Takaoka Hidetoshi , Ishii Yoshikazu , Enomoto Youichi , Murakami Toshiaki 
Published: June 2020

The structure of Ba2YCu3O7-x(BYCO) has been almost completely analyzed using neutron,x-ray, and electron diffraction techniques. However, most of these analyses have studied bulk polycrystallinites or single crystals of BYCO, not the thin film structure. In this study, cross sections of thin annealed films on SrTiO3 substrate are observed using transmission electron microscopy (TEM). The crystal structure near the film/substrate interface is examined.The samples for TEM observation were cut from the same film which showed an onset temperature of 80 K. Samples for cross-sectional TEM observation were prepared by the ordinary method without using water. Milling was performed using a 4 kV Ar+ beam at an incident angle of about 15°. Observation was performed using a JEOL JEM 4000EX microscope at an accelerating voltage of 400 kV.A low magnification cross-sectional image of the BYCO annealed film is shown in Fig. 1. The film thickness is about 0.7 μm.
An external photographic system for electron microscopes
Authors: Guetter E. , Menzel M. 
Published: June 2020

In commercial electron microscopes documentation of the electronmicroscopic image is realized by direct exposure of the photographic emulsion by the image-forming electrons. Exchange of the photographic material loads the vacuum system by gassing when brought in the vacuum. This impairs the operating vacuum, interrupts photography, and increases the danger of contamination.These disadvantages are overcome by a photographic system outside the vacuum chamber of the electron microscope.It requires an image transmission element which provides a vacuum-tight closure of the microscope column, and transmits the image from the vacuum at minimum loss of energy and information content. A fiber plate of 6 μm fiber diameter and a numerical aperture of 1 proved to be the best solution. In vacuo an image converter layer is provided in close contact with the fiber plate. It converts the electron image into a visible image. A high-resolution polycrystal fluorescent screen of high luminous efficiency is deposited on the fiber plate.
Calculation of structure images of crystalline defects
Authors: O'Keefe M.A. , Iijima Sumio 
Published: June 2020

We have extended the multi-slice method of computating many-beam lattice images of perfect crystals to calculations for imperfect crystals using the artificial superlattice approach. Electron waves scattered from faulted regions of crystals are distributed continuously in reciprocal space, and all these waves interact dynamically with each other to give diffuse scattering patterns.In the computation, this continuous distribution can be sampled only at a finite number of regularly spaced points in reciprocal space, and thus finer sampling gives an improved approximation. The larger cell also allows us to defocus the objective lens further before adjacent defect images overlap, producing spurious computational Fourier images. However, smaller cells allow us to sample the direct space cell more finely; since the two-dimensional arrays in our program are limited to 128X128 and the sampling interval shoud be less than 1/2Å (and preferably only 1/4Å), superlattice sizes are limited to 40 to 60Å. Apart from finding a compromis superlattice cell size, computing time must be conserved.
Computer simulation of high resolution images of crystal defects
Authors: Rez Peter , Krivanek Ondrej L. 
Published: June 2020

During the last two years, the cores of several lattice defects in elemental Si and Ge have been directly imaged by high resolution electron microscopy The 3Å resolution images necessary for such work are even more sensitive to microscope defocus, astigmatism and other imaging parameters, and the specimen thickness and orientation, than the 4Å resolution images of complex oxides. Comparison of experimental results with computer-simulated images is therefore essential. The need for matching with theoretical simulations will increase for the coming generation of the 1-2Å point-to-point resolution microscopes.The presently used image simulation programs are based on the multi-slice formulation of the dynamical scattering theory. They are very adequate for thin specimens and a few hundred beams but at larger specimen thicknesses and a greater number of beams the computation times required to simulate one image may be an hour or more.We are therefore investigating the suitability of alternative computational approximations and formalisms such as neglecting diffuse-diffuse scattering in the multi-slice method and the matrix diagonalization formulation of the dynamical scattering theory.
Characterization of neutron irradiation damage in zirconium alloys—an international “round-robin” experiment
Authors: Northwood D.O. , Gilbert R.W. , Kelly P.M. , Madden P.K. , Faulkner D. , Adamson R.B. 
Published: June 2020

Over the past few years there has been disagreement between laboratories on the exact nature of the damage in irradiated zirconium alloys. The main disagreement has centred on whether or not dislocation loops with c-component Burgers' vectors are formed during the irradiation. Since the presence of c-component loops was required in one of the current theories of irradiation growth and is considered in many other models, it was desirable to clear up this point and others relating to the nature of the damage such as loop size, loop concentration and the nature of the loop population, i.e. vacancy or interstitial. To this end a ‘round-robin’ series of transmission electron microscopy (TEM) examinations of neutron irradiated zirconium alloys was organized and the results are reported herein.The participants in the ‘round-robin’ included laboratories who had previously claimed to have seen evidence for c-component damage. The materials examined included zirconium and Zircaloy-2 irradiated at temperatures from 250-400°C, Table 1, the materials irradiated at 400°C providing samples with dislocation loops large enough to determine the interstitial/vacancy nature by inside/outside contrast techniques.
In situ TEM studies of NaCl-gas reactions
Authors: Chung T.T. , Dash J. , O'Brien R.J. 
Published: June 2020

The electron microscope is an important instrument for studying the structure and morphology of particulates collected from the atmosphere, but its potential for direct observation of the interactions between atmospheric aerosols and gases has not been explored previously. A cell with thin film windows and ports to permit the passage of gases was constructed for this purpose, Fig. 1. This cell is designed for use in the tilting stage of a Hitachi HU125 TEM. The thin film windows (manufactured by E. F. Full am, Inc. (1) ) consist of a composite film of formvar and evaporated SiO on 400 mesh Cu grids.In the first experiments with this cell, particles of NaCl were collected from a modified De Vilbiss nebulizer on the lower window of the cell and observed continuously during passage through the cell of either (1) water vapor or (2) water vapor and NO2.The image was recorded continuously on video tape and intermittently on sheet film.
Deposited emulsion particles in the pores of aluminum oxide film
Authors: Ashida Michio , Ueda Yasukiyo 
Published: June 2020

An anodic oxide film is formed on aluminum in an acidic elecrolyte during anodizing. The structure of the oxide film was observed directly by carbon replica method(l) and ultra-thin sectioning method(2). The oxide film consists of barrier layer and porous layer constructed with fine hexagonal cellular structure. The diameter of micro pores and the thickness of barrier layer depend on the applying voltage and electrolyte. Because the dimension of the pore corresponds to that of colloidal particles, many metals deposit in the pores. When the oxide film is treated as anode in emulsion of polyelectrolyte, the emulsion particles migrate onto the film and deposit on it. We investigated the behavior of the emulsion particles during electrodeposition.Aluminum foils (99.3%) were anodized in either 0.25M oxalic acid solution at 30°C or 3M sulfuric acid solution at 20°C. After washing with distilled water, the oxide films used as anode were coated with emulsion particles by applying voltage of 200V and then they were cured at 190°C for 30 minutes.
Formation of carbides by C-diffusion in Cr-Fe-Ni alloys
Authors: Peignier P. , Demel O. , Degischer H.P. 
Published: June 2020

MATERIAL: Cr-Fe-Ni alloys, casted in air, treated at 1150°C, 20 mn/water quenched. Cr constant 15%, Ni range 15 to 70%, 0,011 to 0,017% C, 0,03-0,07% N, 0,22-0,54% Mn. The C-diffusion experiments were realized at 850 °C/53 h in pure argon. The carburizing profile is known from tracer experiments (1). The penetrating carbon forms carbides to be investigated.METHODS: Optical metallography and T.E. microscopy on carbon replicas (etching agent: Br-ethanol 10%) were performed to identify the precipitates and to determine their distribution and morphology. The crystal structure was investigated by SAD using a rotation-tilt stage (± 55° tilt) : a low indexed g-vector is rotated into the tilt axis,from there the specimen is tilted to obtain the characteristic diffraction patterns of the inclusion and thus it is possible to reconstruct the reciprocal lattice. X-ray structure analysis was performed to find the exact lattice parameters and to get an indication of the amount of the different phases.
Electron microscopic examination of mast cells and nerve processes in hepatic portal areas of the rat
Authors: Dimlich R. V. W. 
Published: June 2020

Neural mechanisms are important in the regulation of numerous hepatic functions including hepatic blood flow, carbohydrate metabolism and biliary flow. The innervation of the liver is species specific and in the rat, light microscopic data indicated that catecholamine and cholinergic nerves were present in portal areas. (1,2) Electron microscopic studies described the presence of nerve endings in the connective tissue adjacent to blood vessels and bile ducts as well as limiting plate hepatocytes. (2) A previous study in this laboratory reported unmyelinated nerve processes near mast cells. (3) The present study was undertaken to quantify the appearance of nerves and their relationship to mast cells in hepatic portal areas in rats.Hepatic tissue from 8 rats was removed and fixed in 2% glutaraldehyde and 2% paraformaldehyde in a 0.1M Na cacodylate buffer (pH 7.3), postfixed in 1% osmium tetroxide, and embedded in Epon. Sections stained with uranyl acetate and lead citrate were viewed on a Philips 301 electron microscope. A minimum of 3 sections per rat and a total of 30 portal areas were analyzed.
The cytochemical localization of glucose-6-phosphatase and catalase in cells comprising the root cap of corn
Authors: McClelen C.E. 
Published: June 2020

The root cap of corn (Zea mays) is comprised of several different types of cells, each having a unique structure and function. For example, columella cells in the center of the cap are responsible for perceiving gravity. These cells subsequently differentiate into peripheral cells, which are located at the edge of the cap and function in the production and/or secretion of mucopolysaccharides (mucilage). Differences in enzymatic activity and location in cells of the root cap provide key evidence for the nature and site of the functional changes that accompany differentiation.The cytochemical localizations of glucose-6-phosphatase (G-6-Ptase) and catalase were undertaken to define the modifications of enzyme localization associated with cellular differentiation in root caps of Zea mays. G-6-Ptase and catalase were localized using procedures described by Hall. Cytochemistry as performed in this study was consistently specific for the designated enzyme and gave precise ultrastructural localization. Enzymatic precipitate was absent in all controls. Sections were not counterstained to allow for positive identification of staining due to enzymatic activity.
Interpretation of irradiation-induced changes in electron diffractograms and images of extinction contours at low temperatures
Authors: Knapek E. , Formanek H. , Lefranc G. , Dietrich I. 
Published: June 2020

A few years ago results on cryoprotection of L-valine were reported, where the values of the critical fluence De i.e, the electron exposure which decreases the intensity of the diffraction reflections by a factor e, amounted to the order of 2000 + 1000 e/nm2. In the meantime a discrepancy arose, since several groups published De values between 100 e/nm2 and 1200 e/nm2 /1 - 4/. This disagreement and particularly the wide spread of the results induced us to investigate more thoroughly the behaviour of organic crystals at very low temperatures during electron irradiation.For this purpose large L-valine crystals with homogenuous thickness were deposited on holey carbon films, thin carbon films or Au-coated holey carbon films. These specimens were cooled down to nearly liquid helium temperature in an electron microscope with a superconducting lens system and irradiated with 200 keU-electrons. The progress of radiation damage under different preparation conditions has been observed with series of electron diffraction patterns and direct images of extinction contours.
High-performance transmission electron microscopy of cryospecimens
Authors: Hezel U. B. , Zellmann E. , Hoffmeister D. 
Published: June 2020

Chemical fixation, resin embedding and subsequent staining with heavy metals can both produce artefacts and limit the resolution in the electron microscopic specimen /1-5/. The objective is thus to observe the specimens in the electron microscope in the frozen-hydrated state, the one most similar to the native state.All preparation steps such as cryofixation, cryosectioning and cryotransfer to the cryo-transmission electron microscope (CryoTEM) should be performed below 145K /5/ in order to observe the specimen in a matrix of vitrified ice avoiding any crystallization artefacts. In the CryoTEM itself the temperature of the frozen-hydrated specimen should be kept much lower to avoid devitrification caused by the electron beam /1/. - To meet all these requirements a special cryotransfer system and cryostage for the Zeiss transmission electron microscopes have been developed /7/.
Structural changes induced by fluoride in rat bones
Authors: Reid A. D. , Grynpas M. D. , Pritzker K. P. H. , Harrison J. E. 
Published: June 2020

Fluoride is an essential trace element for normal skeletal growth and maintenance. As fluoride intake can lead to increased skeletal mass, fluoride in the form of NaF is being used clinically in the treatment of osteoporosis. The mechanisms by which fluoride affects bone is poorly understood. NaF administration has been found to increase the rate of bone formation along with an increase in the number of osteoblast cells. Fluoride has been also shown to increase the crystallinity of bone apatite by substituting for hydroxylions in the apatite lattice, rendering bone mineral less soluble and more stable.In our study we undertook to elucidate further the effects of fluoride on bone mineral. Eight mature female rats (250-300 g) were divided into control and fluoride-treated groups with 4 rats in each group. The fluoridetreated rats were given a fixed amount of supplemental NaF in their water and food: the control group was given distilled water and no supplemental fluoride. The animals were sacrificed 7 weeks later.
Scanning Electron Microscopy Study of Porous Anodic Films on Aluminum
Authors: Phillips V. A. , Meyerhoff M. 
Published: June 2020

If aluminum is anodized in a bath, such as sulfuric acid, in which the anodic oxide coating has appreciable solubility, then the oxide layer may grow to a thickness of many microns. The resulting film can be regarded as consisting of two layers, a thin barrier layer adjoining the surface of. the metal, and an outer thick film containing pores. The latter convey the electrolyte to the barrier layer, permitting continued oxidation.We have examined the structure of a number of sulfuric acid anodized films to assess the applicability of the two principal models of the pore structure. The older model represented the pores as rather regularly spaced, uniform channels running nearly normal to the oxide surface, separated by walls of amorphous alumina. Although conceived as starshaped rather than circular in cross-section, experimental evidence has pointed to the latter. In this ideal model, the porous film was made up of hexagonal cells of amorphous alumina, each containing a central pore.