bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specimen Collection Effect in Scanning Electron Microscopy Images
Authors: Temple Black J. , Guerrero Jose 
Published: June 2020

In the SEM, contrast in the image is the result of variations in the volume secondary electron emission and backscatter emission which reaches the detector and serves to intensity modulate the signal for the CRT's. This emission is a function of the accelerating potential, material density, chemistry, crystallography, local charge effects, surface morphology and especially the angle of the incident electron beam with the particular surface site. Aside from the influence of object inclination, the surface morphology is the most important feature In producing contrast. “Specimen collection“ is the name given the shielding of the collector by adjacent parts of the specimen, producing much image contrast. This type of contrast can occur for both secondary and backscatter electrons even though the secondary electrons take curved paths to the detector-collector.Figure 1 demonstrates, in a unique and striking fashion, the specimen collection effect. The subject material here is Armco Iron, 99.85% purity, which was spark machined.
Modification of the High Voltage Supply of an Electron Microscope for Improved Stability
Authors: Gauldin R. E. , Wittry D. B. 
Published: June 2020

The high voltage power supplies of older transmission electron microscopes lack the feedback regulation that provides the exceptional voltage stability found in modern instruments, A method has been devised to apply feedback control to an existing high voltage supply. The modification requires few changes in the original power supply circuitry and uses relatively inexpensive, commercially available components.A stable accelerating voltage is required to achieve high resolution in transmission electron microscopy; an analysis of the chromatic aberration for a resolution of 2 Å leads to a required voltage stability of about one part in 105 over the period of exposure A stable accelerating voltage is also required when the microscope is used with a magnetic prism electron spectrometer for “selected area“ electron spectrometry. The stability of the accelerating voltage should be significantly better than the thermal energy spread of the electrons if the full resolution of the spectrometer is to be realized.
Cellulose Acetate Reverse Osmosis Membrane Structure
Authors: Plummer H. K. , Eichen E. , Melvin C. D. 
Published: June 2020

Much of the work reported in the literature on cellulose acetate reverse osmosis membranes has raised new and important questions with regard to the dense or “active” layer of these membranes. Several thickness values and structures have been attributed to the dense layer. To ensure the correct interpretation of the cellulose acetate structure thirteen different preparative techniques have been used in this investigation. These thirteen methods included various combinations of water substitution, freeze drying, freeze sectioning, fracturing, embedding, and microtomy techniques with both transmission and scanning electron microscope observations.It was observed that several factors can cause a distortion of the structure during sample preparation. The most obvious problem of water removal can cause swelling, shrinking, and folds. Improper removal of embedding materials, when used, can cause a loss of electron image contrast and, or structure which could hinder interpretation.
Contrast in High Resolution Images of Crystals
Authors: Fejes P. L. 
Published: June 2020

An attempt is made to understand experimentally observed high resolution electron microscope images. Iijima has obtained images that are good representations of the crystal potentials for a resolution of about 3Å using a defocus corresponding to the “optimum defocus condition”. This is to be expected for a thin phase object. However, Iijima's images are obtained from crystals having thicknesses of 100Å and greater for which the maximum phase change is more than 10 radians, and so the thin phase object approximation is not expected to be valid. These images must therefore be explained by other means.Many beam calculations have been made on thick crystals using a trial crystals structure as shown in Fig. 1. A metal atom sits at the centre of each octahedral site with oxygen atoms at the corners. This structure contains blocks of 3 x 3 octahedra of the type found in disordered samples of Ti2Nb10O29 as shown in Fig. 2.
Reconstruction of Two-Dimensional Projections of GP 32*I
Authors: Cohen H.A. , Chiu W. , Hosoda J. 
Published: June 2020

GP 32 (molecular weight 35000) is a T4 bacteriophage protein that destabilizes the DNA helix. The fragment GP32*I (77% of the total weight), which destabilizes helices better than does the parent molecule, crystallizes as platelets thin enough for electron diffraction and electron imaging. In this paper we discuss the structure of this protein as revealed in images reconstructed from stained and unstained crystals.Crystals were prepared as previously described. Crystals for electron microscopy were pelleted from the buffer suspension, washed in distilled water, and resuspended in 1% glucose. Two lambda droplets were placed on grids over freshly evaporated carbon, allowed to sit for five minutes, and then were drained. Stained crystals were prepared the same way, except that prior to draining the droplet, two lambda of aqueous 1% uranyl acetate solution were applied for 20 seconds. Micrographs were produced using less than 2 e/Å2for unstained crystals or less than 8 e/Å2for stained crystals.
Precipitation in Al-Li-Cu Alloys
Authors: O'Neal J. E. , Sankaran K. K. 
Published: June 2020

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.
The Microstructure of Mechanically Alloyed Al-4Mg Alloy
Authors: Kang Sung K. 
Published: June 2020

The mechanical alloying of powders by high-energy ball milling is one of the recent technologies for the production of heat-resistant oxide-dispersion-strengthened (ODS) alloys. This technique has been successfully applied to Fe-, Ni-, and Al-base alloys. The microstructure and properties of mechanically alloyed (MA) materials are quite different from those produced by conventional ingot metallurgy. Many questions remain unanswered about the structure-property relations of MA materials. The study of these relationships is difficult because of very small grain size and the presence of dispersoids, precipitates, dislocation substructure, and texture.A detailed investigation of the microstructure is necessary to understand the unique properties of these materials. In the present paper, some of the microstructural information about a MA Al-4%Mg alloy is reported. A study of the structure of the MA powders and the structure of the consolidated MA alloys is required in order to relate the processing parameters to the alloy properties. Various electron-optical and X-ray diffraction techniques have been employed for this purpose.
The Study of Ordered Alloys by Means of Electron Diffraction and High Resolution Electron Microscopy : Application to Au4-xMn
Authors: Van Tendeloo G. , Amelinckx S. 
Published: June 2020

The study of ordered alloys by means of conventional X-ray diffraction methods is hampered by the fact that even single crystals of such alloys are invariably fragmented in symmetry related domains; unscrambling of such combined patterns into mono domain patterns is usually not straightforward. In electron diffraction it is on the other hand often possible to select a single domain on the image and obtain a mono-domain diffraction pattern.The use of suitable high resolution imaging techniques allows often to derive a trial structure, for which the image and the diffraction pattern can be calculated and compared with the observations. It is our intention to demonstrate how the combined use of both techniques allows the determination of crystal structures of rather complicated alloys in the gold-manganese and gold-magnesium systems.
Analytical Microscopic Investigation of Commercial Oxide Dispersion Strengthened Alloys
Authors: Raghavan M. , Klein C. , Petkovic-Luton R. 
Published: June 2020

Oxide particles in three commercial Yttria Dispersion Strengthened alloys were analyzed using an analytical electron microscope. The following are the alloy compositions:Both thin samples and extracted residue of oxides were used for electron microscopic analysis. These samples were prepared by conventional electropolishing followed by ion thinning. Extraction of oxides was conducted in a conventional electrolyte. The extract was centrifuged, cleaned and supported on carbon film for examination. Analysis of particles in the range of 200-700 Å was conducted on the extracted residue while particles in the range of about 750-1500 Å were analyzed in the thin sample. The X-ray microanalysis data were corrected for absorption, including oxygen where necessary, using techniques described before (1).X-ray microanalysis and microdiffraction analysis indicated that besides aluminum oxide, these alloys could contain up to four distinct aluminum-yttrium oxides.
A Method for Computing Electron Microscope Images with Partial Coherence, Hollow Cone Illumination and Virtual Apertures
Authors: Krakow William 
Published: June 2020

Image formation in the electron microscope when the illumination is partially coherent has been studied in some detail and partial coherence envelope functions have also been developed for axial illumination and weak phase objects. These envelope functions have been applied to crystalline strong phase objects where the effect of the Ewald sphere was discounted. The effect of axial beam divergence has been considered explicitly for crystalline materials where separate dynamical diffraction and image computations were performed for each beam inclination and the resultant image was a summation of these separate images.Computer programs have been designed which calculate image intensities not only for axial illumination partial coherence but for titled beam illumination, cone illumination or any arrangement of incident beam inclinations where there is partial coherence (virtual apertures). Here the effect of the beam tilt on dynamical diffraction is neglected so that repeated multislice computations are avoided.
Scanning Transmission Electron Microscopy (STEM) of Annelid Extracellular Hemoglobins
Authors: Kapp O. H. , Ohtsuki M. , Vinogradov S. N. , Crewe A. V. 
Published: June 2020

Scanning transmission electron microscopy (STEM) was used to study the structure of the extracellular hemoglobin of the annelid Lumbricus terrestris. These are giant molecules possessing a molecular weight of approximately 3.9 x 106and appear in electron micrographs as a hexagonal bilayer, The samples for this study were diluted to 100 μg/ml with distilled water and applied to a thin ( ∽15 Å) carbon substrate supported on a microgrid. One percent (w/v) uranyl acetate solution was used for negative staining for 2 minutes and dried in air. STEM images were recorded using both a high resolution CRT with 1024 x 1024 picture elements and an on-line computer recording with 512 x 512 pixels. The images were rotated in on-line fashion with the computer to enhance contrast.The hemoglobin of Lumbricus assumes three common positions on the substrate (Fig. 1). The top view (Fig. la) demonstrates that the 1/12th subunits possess an approximately pentagonal shape with a central region of low protein density.
Electron Microscopic Characterization of Insect Hemocytes
Authors: Wittig Gertraude 
Published: June 2020

The fine structure of insect hemocytes has been the subject of very few investigations. In particular, the hemocytes of Lepidoptera have received almost no attention. The study presented here was carried out on the armyworm, Pseudaletia unipuncta. Hemocytes of the larva were fixed 2 to 4 days after molt to the sixth instar and studied in ultrathin sections.Microplasmatocytes (Fig. 1) were the most important phagocytes of army-worm hemolymph. They were relatively small, spherical cells with a small, round or lobed nucleus. Distensions of the perinuclear cisterna (p) were frequent and sometimes continuous with the rough endoplasmic reticulum (e). The latter formed greatly distended cisternae which almost filled the whole cytoplasm. The cisternae contained an amorphous material which appeared to be condensed in certain sacs (at e). Mitochondria (m) were rare, and they had tubular cristae. Up to four Golgi complexes (g) were identified in a microplasmatocyte section. Structured granules (sg) were specific for this cell type. Microfibrils (f) traversed the whole cytoplasm but were most frequent around the nucleus (N) and under the cell membrane.
Fine Structure of Cytochalasin Induced Polyploid Cells
Authors: Krishan Awtar , Bohonos Nestor 
Published: June 2020

Cytochalasin B, a mould metabolite from Helminthosporium dermatioideum has been shown to interfere with specific cell activities such as cytoplasmic cleavage and cell movement. Cells undergoing nuclear division in the presence of cytochalasin B are unable to complete the separation of the resulting daughter cells. In time-lapse studies, the daughter cells coalesce after an initial unsuccessful attempt at separation and form large multinucleate polyploid cells. The present report describes the fine structure of the large polyploid cells induced in Earle's L-cell monolayer cultures by exposure to cytochalasin B (lγ/ml) for 92 hours.In the present material we have seen as many as 7 nuclei in these polyploid cells. Treatment with cytochalasin B for longer periods of time (6 to 7 days, with one medium change on the 3rd day) did not increase the number of nuclei beyond the 7 nuclei stage. Figure 1 shows a large polyploid cell with four nuclei. These nuclei are indistinguishable in their fine structure from those of the cells from control cultures but often show unusually large numbers of cytoplasmic invaginations and extensions of the nuclear surface (Figure 2).
Daunomycin Nephrosis with Special Reference to Cross-Striated Fibrils in Glomeruli
Authors: Sternberg Stephen S. 
Published: June 2020

Daunomycin, a glycosidic antibiotic isolated from cultures of Streptomyces peucetius, consists of a chromophor (daunomycinone) linked to an amino sugar (daunosamine). It is inhibitory to the growth of He La and KB cells in culture, and has antitumor activity in rodents and man. Daunomycin complexes with DNA and has been shown to inhibit both DNA and RNA synthesis.Rats given a single intravenous injection of 20 mg/kg (ca LD50)rapidly develop severe bone marrow depression, and damage to lymphoid tissues and intestinal crypts. Recovery from the initial toxicity to proliferative tissues takes place within several days but shortly, thereafter, a nephrotic syndrome develops. The renal phase of intoxication is manifested by proteinuria, hypoalbuminemia, elevation of α1 globulin, anarsarca, hyperlipemia, and hypercholesterolemia.
Lattice Defects in Stainless Steel Shock-Loaded to Pressures Above 1 Megabar
Authors: Murr L. E. , Rose M. F. 
Published: June 2020

Previous investigations of defect structures in 304 stainless steel shock loaded in the pressure range 120-425 kilobars by the authors have indicated a consistent increase in the specimen residual microhardness with pressure; and direct observations of specimen microstructures by transmission electron microscopy revealed a consistent increase in deformation twin-fault density with increasing shock pressure. Recent extensions of this research in the very high pressure range have indicated that the residual microhardness continues to rise to a maximum of 384(VHN-200 gm load) at about 750 kilobars in comparison with a starting (annealed sample) microhardness of 161. At pressures above 800 kilobars, the hardness decreases; and at 1200 kilobars the microhardness is observed to be 312.Shock loading at 1.2 megabars was accomplished by employing 0.007 in. thick specimens of 304 stainless steel (measuring 1 in. on a side) in a sandwich assembly recently described by Rose and Grace. A flying plate, explosively initiated by a plane-wave generator and an HMX-95-5 main charge imparted a plane shock pulse of approximately 2 microseconds duration to the sandwich. Thin samples for examination by electron transmission were prepared by electropolishing the recovered samples² as previously described by Murr
Improvements & Performance of the Hitachi 200KV Electron Microscope
Authors: Katagiri S. , Akahori H. , Ueno S. , Iwama A. 
Published: June 2020

1.Electron gun - A new high voltage cable and porcelain insulator has been developed. A successful study of superior surface treatment of the insulator and improved means of sealing the cable resulted in eliminating surface discharge of the insulator. Since an electrode discharge and surface discharge of an insulator cannot be completely eliminated in a vacuum of the order of 10-5 to 10-6 torr, an high capacity vacuum system is employed to assure high vacuum and a discharge free system. Further, small quantities of inert gases such as N2, Ar, He etc. is introduced into the gun chamber to maintain a vacuum of 1 to 2 x 10-4 torr.2.Evacuating system.At 200KV it is necessary in a single stage electron gun to provide greater insulating distance to inhibit discharges. Consequently, the electron gun chamber is inevitably larger. The gun chamber volume of this electron microscope is 32 liter. A 4″ diameter single manifold and 1200 liter/sec. oil diffusion pump comprise the evacuating system.
Hitachi Scanning Electron Microscope
Authors: Fujiyasu T. , Hara K. , Tamura H. 
Published: June 2020

The demand for scanning electron microscopes is growing rapidly and exciting new fields of application have developed for this type of instrument. Hitachi, Ltd. has developed this type of instrument the details of which are described in this paper.A three stage demagnification lens system is used in the instrument. External magnetic and electrical disturbances and mechanical vibrations have been reduced.Aperture plates with different bore diameters are located above the condenser lens and deflection coil and the objective lens to reduce contamination by the fixed apertures in these lenses. An electromagnetic stigmator is provided in the objective lens field.The specimen stage permits X-, Y- and Z- axes movements as well as rotational tilting. The rotational tilting is such that its central axis is always coincident with the optical axis independent of the X-, Y- and Z- axes movements. Terminals are also provided which permit voltage measurements and to observe the electrical potential distribution of semi conductors.
Cytoskeletal control of neuronal geometry: A serial EM analysis
Authors: Stevens John K. , Trogadis Judy 
Published: June 2020

The cytoskeleton plays a direct role in controlling neurite shape. To quantitatively study both the three dimensional shape and the sub-micron structure of the cytoskeleton requires complete serial reconstruction at the Electron Microscopic level. We have devised a computer reconstruction system specifically for this purpose.The system uses a 35mm film copy of 3.25 x 4.00 inch EM negative as the data source. The film is placed into a high speed film transport (15 frames/second), which is mounted on a X,Y and rotation stage controlled by stepping motors. The 35mm film is viewed through a stepping motor controlled zoom lens mounted on a high resolution (1119 x 1024) video camera. A high resolution frame grabber controlled by the computer can store one complete frame. Thus, the live image and a stored image may be displayed alternately on a high resolution monitor. Finally, a graphics overlay and mouse connected to the computer can be used to align successive sections via the stepping motors, as well as to trace the outlines of a profile, or of a microtubule.
The application of video-enhanced constrast/differential interference constrast microscopy in conjunction with whole mount electron microscopy to the study of organelle transport
Authors: Hayden J. H. 
Published: June 2020

In a previous study, Allen video-enhanced constrast/differential interference constrast (AVEC-DIC) microscopy was used in conjunction with immunofluorescence microscopy to demonstrate that organelles and vesicle move in either direction along linear elements composed of microtubules. However, this study was limited in that the number of microtubules making up a linear element could not be determined. To overcome this limitation, we have used AVEC-DIC microscopy in conjunction with whole mount electron microscopy.Keratocytes from Rana pipiens were grown on glass coverslips as described elsewhere. Gold London Finder grids were Formvar- and carbon coated, and sterilized by exposure to ultraviolet light. It is important to select a Formvar film that gives a grey reflection when it is floated on water. A silver film is too thick and will detract from the image in the light microscope.
Quantitative recovery of virus from blood plasma using a polycarbonate filter purification procedure
Authors: Miller M. F. , Gagne G. D. , Lesniewski R. , Peterson D. A. 
Published: June 2020

Polycarbonate filters (Nuclepore Corporation, Pleasanton, CA) have beep used for sizing particulates such as virus particles and liposomes. Unlike nitrocellulose, polyester and other types of filters which are comprised of a relatively thick meshwork of interwoven fibers, polycarbonate filters are thin and contain precisely sized, straight-bore holes (Fig. 1). These features suggest that loss of particles due to nonspecific adsorption or entrapment in the filter matrix might be less for polycarbonate filters. In the present study, we have devised a purification technique based on the sequential filtration of blood plasma through a series of polycarbonate filters. The technique was evaluated by seeding chimpanzee blood plasma with human rotavirus (65-70 nm dia.) and determining recovery of purified virus using a sensitive electron microscope virus particle counting technique.Whole normal blood plasma (10 ml) was seeded with highly purified rotavirus to a final concentration of about 1010 particles per ml.