bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Oak Ridge Program for High Resolution Microscopy
Authors: Worsham R. E. , Harris W. W. , Welton T. A. 
Published: June 2020

In the latter part of 1967, a program began at the Oak Ridge National Laboratory for the development of high resolution microscopy. The immediate design goal is a point-to-point resolution of at least 1 Å, to allow superior delineation of organelle structures, as well to offer a possibility of atomic identification and location in complex biomolecules. The proposed techniques seem to offer in principle the possibility of resolution limited only by random thermal motion in the sample.Theoretical studies of both lens aberrations and image formation are being actively pursued. The aberration studies are aimed at design of a practical corrector for the primary spherical aberration, along lines first suggested by Archard. The image studies partially described elsewhere in these proceedings are aimed both at optimizing instrument performance and at the development of adequate methods for interpretation of high resolution phase contrast data.
High Voltage Microscopy of Thick Specimens
Authors: Hart Raymond K. 
Published: June 2020

The aspect of high voltage electron microscopy which makes it inviting to solve both biological and physical problems is the ability of this technique to probe thicker specimens and at higher resolution than is currently possible with conventional electron microscopes. Naturally, there will be a thickness limit above which an electron beam will cease to be an effective means of obtaining useful microscopical data. The ultimate limit will be determined by the specimen induced chromatic aberration, resolution, contrast processes, and transmitted intensity available for image production.Recently Uyeda and Nonoyama have determined the maximum usable thickness of molybdenite for operating voltages up to 1.2 MeV. They showed that this thickness is approximately proportional to kβ2, where k is a small constant and β is the ratio of the velocity of an electron to that of light. Aluminum has also been observed to follow this β2 relationship. Even thicker specimens have been viewed with fair clarity, indicating that anomalous transmission effects can occur in crystalline material. These are thought to be due to directional dependence of the absorption coefficient. For aluminum, the thickness of specimens showing anomalous transmission would fall above curve A in Figure 1.
A Field Emission High Voltage Electron Gun
Authors: Eggenberger D. N. , Hart R. K. , Libal A. C. 
Published: June 2020

Progress in electron microscopy toward higher resolution and higher voltage has generated new approaches in addition to upgrading conventional methods in instrumentation. For scanning microscopy the resolution is of the order of the focussed beam spot size so progress here depends upon decreasing this size, which in turn may require a smaller source size. A major step has been made by using a cold emission tip source along with an anode system specifically designed for minimizing spherical aberration.A cold emission tip electron source has several advantages for electron microscopy. The apparent size of the electron source is very small, about 30 Å ideally, compared to conventional thermionic emitters. The energy spread of electrons is about 0.2 eV, a useful fact where energy analysis is part of the system. Also the brightness is several orders of magnitude higher than can be obtained in thermionic emitters.
Thin Film Nucleation and Growth Under Controlled Conditions
Authors: Poppa Helmut 
Published: June 2020

Results of controlled in-situ nucleation experiments inside the electron microscope were reported recently. The experimental technique employed permitted detailed quantitative studies of the nucleation kinetics which led to a comparison of test results with nucleation theoretical predictions. However, the background pressures were still of the order of 10-7 to 5x10-8 torr and the experimental arrangement did not provide for producing and maintaining clean single-crystal substrates. It was therefore necessary to limit the choice of substrate-overgrowth material combinations, delete epitaxial studies completely, and defer meaningful investigations of the effect of residual gases on nucleation and growth processes. In addition, the influence on the experimental results of the high-intensity imaging electron beam could only be assessed in a qualitative manner.A research program involving two methodically different experimental approaches has since been initiated that promises to eliminate most of the previous test restrictions. The two approaches entail the use of a modified low-energy electron diffraction (LEED) system in conjunction with extraction replica electron microscopy, and a newly designed ultrahigh-vacuum (UHV) electron-microscope specimen chamber in combination with a microscope image intensifier system for in-situ deposition studies.
Frozen Sectioning of Porous Polymer Membranes for Electron Microscopy
Authors: Koch E. F. 
Published: June 2020

A technique has been devised using a diamond knife ultramicrotome in conjunction with a freezing head to prepare thin sections of porous polymer membranes. The thin sections are examined and photographed in transmission with an electron microscope to reveal the hole sizes in the membranes.Attempts to microtome a particular type of porous polymer membrane at room temperature proved unsuccessful, since the polymer membrane was not strong enough to support Itself when cut to appropriate viewing thicknesses of about 250 Å to 500 Å. It was thought that some degree of rigidity could be imparted to the polymer by cooling it below room temperature. Therefore, a freezing head was made for the Porter-Blum microtome, similar to the one developed by Crudgington, Fig. 1.
Phase Structure in Blends of Incompatible Polymers
Authors: Brodsky P. H. , Cocks G. G. , Winding C. C 
Published: June 2020

Microscopical observations of films made up of two incompatible polymers may provide useful insights into the unusual properties of many polymer blends. In the present study an attempt has been made to determine the factors which control the sizes and shapes of the phases present in solution-cast, two-polymer films. The variables included the ratio of the two polymers, the concentration of the solution from which the films were prepared, and the type of solvent used.The polymers studied included poly(vinyl acetate), a copolymer containing 85% poly(vinyl chloride) and 15% poly(vinyl acetate), poly(methyl methacrylate, and polystyrene. These will be abbreviated PVAc, PVC copolymer, PMMA, and PS respectively. The solvents included methyl ethyl ketone (MEK), toluene, benzene, and chloroform and the solution concentrations were varied from 0.2 to 1.0 per cent solids by weight.
Effects of Hydrogen on Cathodically Charged 6Al-4v and 6Al-6v-2Sn Titanium Alloys
Authors: Danovich J. F. , Sipes W. A. 
Published: June 2020

The αβ-Ti-alloys, like the high strength steels, show a susceptibility to delayed fracture and to hydrogen embrittlement. These similar modes of failure suggest that the same failure mechanism, i.e. diffusion and concentration of hydrogen, is active in both materials. To establish base line information for such a comparison, the replication technique of electron microscopy was used to study the fracture surfaces and microstructures of candidate αβ-Ti alloys cathodically charged with hydrogen. As-received mill annealed samples were studied in addition to cathodically charged specimens so as to eliminate spurious results due to artifacts.Figure la shows the normal microstructure of the as-received 6Al-4V alloy near the surface of the specimen. Figure 1b shows the effect of hydrogen in an approximately 1/128″ deep sub-surface zone of a cathodically charged specimen. Here the matrix substructure was affected while the beta phase became clearly delineated. Beyond 1/128″ from the surface, the matrix interior was unaffected.
Grain Size and Physical Properties of Co-Evaporated Cr-Cu Thin Film Alloys
Authors: Anderson Ronald M. , Beaudouin Pierre L. 
Published: June 2020

Experiments were carried out to determine resistivity and stress as a function of grain size and composition in co-evaporated Cr-Cu alloys. The films were evaporated from two adjacent sources which were selected for their reliability. The Cu was melted in a radiantly heated Mo crucible. The Cr was sublimated from an arc-melted high-purity Cr bar which provides an exceptionally constant evaporation rate. The depositions took place in a standard evaporator with a liquid nitrogen-cooled stainless steel bell jar in the range of 10-7 Torr. Substrate temperatures were maintained at 200°C.The evaporated film thicknesses were between 1000A and 4000A and, when required, were thinned by RF sputter etching. The compositional analysis was performed by x-ray fluorescence and complemented by electron microprobe techniques.
Fractographic Observations of Sapphire Whisker Reinforced Alumina
Authors: Hermann R. A. , Divecha A. P. , Lare P. J. , Hahn H. 
Published: June 2020

Fiber reinforcement of ceramics has generally been limited to metallic fibers. Metallic fibers have improved the thermal properties of ceramics but have generally been ineffective in promoting increased strengthening. Discontinuous ceramic fiber reinforced ceramics have demonstrated increased strenghtening both in flexure and impact. This investigation was limited to studying reinforcement of an alumina matrix with sapphire whisker fibers.In an attempt to correlate the morphology of the fracture faces of the sapphire whisker reinforced ceramic composites with fabrication and composition parameters; two-stage replicas, cellulose acetate film—carbon film -30° chromium shadow, were prepared from the samples utilized for mechanical testing. The mode of fracture of the samples was generally intergranular as shown in Fig. 1. Trans-granular fracture of the samples was, however, observed and its occurrence became more frequent as firing time and whisker content were increased. Fig. 2 is a fractograph of a twenty percent 3B sapphire whisker-alumina composite which was hot-pressed and subsequently fired at 1315°C.
Formation of Single Microcrystal of Colloidal Selenium
Authors: Chiang Y. S. 
Published: June 2020

Single microcrystals of colloidal selenium have been grown by reducing 2 ml. 1% methanol solution of selenous acid (H2SeO3) with 2 ml. 1% methanol solution of hydroxylamine hydrochloride in the presence of 20 ml. chloroform at room temperature. After about forty hours, selenium microcrystals can be found among numerous amorphous polyhedral shaped particles. Similar selenium microcrystals can also be formed in the presence of ethyl acetate or trichloroethylene, but with considerable less efficiency.The selenium microcrystals are usually present in the form of trigonal shaped platelets or aggregates of them as shown in Fig. 1. Most of the lamellar crystals are about 1000 to 2000 Å in thickness and several microns in width. The flaky habit surface is usually that of the (0001) plane of trigonal selenium (Fig. 2 and 3).
Visualization of small displacement of atoms in crystals by the processing of atom resolution images
Authors: Hashimoto H. 
Published: June 2020

Detection of small displacement of atoms was carried out using diffuse and irregular diffraction spots and Aberration Free Focus (AFF) imaging.Fig. 1 (a) shows the position of atoms of a Ti-Mo alloy where white and black discs represent the position of atoms in β-phase and ω-phase respectively. Namely, the ω-phase is formed by the displacement of atoms in B and C positions.Fig. 1 (b) is an electron diffraction pattern of an as-quenched alloy that contains 16 diffuse diffraction spots due to the displacement of atoms. The corresponding electron micrograph photographed with AFF condition is shown in (c). The images of displaced atoms are rather difficult to see. (d) is the processed image formed by using only diffuse spots in the Fourier Transform (FT) of (c). The bright spots correspond to the shaded displaced atom regions shown in (a) and not to the atom positions which are not displaced [1].Charge Density Waves (CDW) occur as periodic modulations of conduction electrons and produce the periodic lattice distortions.
Cuticular sensilla in the chelate periopods of the red banded coral shrimp Stenopus hispidus
Authors: Trabanino Salvador , Baerwald R. J. 
Published: June 2020

The knowledge of structure and function of crustacean cuticular receptors, especially chemoreceptors, is still scant at the present due to an emphasis on the study of arthropod cuticular sensilla from the Insecta. This report describes by TEM and SEM the structure of sensory pegs along the cutting edge of the chelate periopods of the red banded coral shrimp, Stenopus hispidus, a cleaner shrimp in coral reefs.Stenopus hispidus were collected from the Florida Keys and maintained in marine aquaria. Autotomized chelate periopods for SEM study were fixed in 4% glutaraldehyde in Na-cacodylate buffer, pH = 7.4; sonicated; placed in ethanol; critical point dried; and coated with gold-palladium with a Hummer V sputter coater. The material was then examined in a JEOL 35C SEM. Autotomized chelate periopods within 24 hrs post-molt were fixed for TEM in Karnovsky's fixative in 0.1 M Na-cacodylate buffer, pH = 7.4; post fixed in 1.0% OsO4 in the same buffer; dehydrated through a graded series of ethanols; embedded in Epon-Araldite; and examined in a Philips 300 TEM.
Analysis of 3-d molecular distribution with the digital imaging microscope
Authors: Carrington W.A. , Fay F.S. , Fogarty K.E. , Lifshitz L. 
Published: June 2020

Advances in digital imaging microscopy and in the synthesis of fluorescent dyes allow the determination of 3D distribution of specific proteins, ions, GNA or DNA in single living cells. Effective use of this technology requires a combination of optical and computer hardware and software for image restoration, feature extraction and computer graphics.The digital imaging microscope consists of a conventional epifluorescence microscope with computer controlled focus, excitation and emission wavelength and duration of excitation. Images are recorded with a cooled (-80°C) CCD. 3D images are obtained as a series of optical sections at .25 - .5 μm intervals.A conventional microscope has substantial blurring along its optical axis. Out of focus contributions to a single optical section cause low contrast and flare; details are poorly resolved along the optical axis. We have developed new computer algorithms for reversing these distortions. These image restoration techniques and scanning confocal microscopes yield significantly better images; the results from the two are comparable.
Scanned aperture light microscopy
Authors: Ellis Gordon W. 
Published: June 2020

Scanned aperture microscopy is a new form of light microscopy which allows unprecedented latitude in spatial filtering and/or contrast enhancement without sacrifice in either depth discrimination or resolution. This method which utilizes synchronous scanning at the condenser entrance pupil and the objective exit pupil should not be confused with confocal scanning light microscopy which scans the object and image planes.In operation a point source of illumination, conveniently supplied by a light fiber, is scanned over the desired portion of the condenser entrance pupil while a spatial frequency selective and/or phase altering mask is synchronously scanned over a corresponding portion of the objective exit pupil in register with the image of the source. At each point in the scan, the image is the coherently filtered result of illumination along a unique direction relative to the specimen. Each of these incremental images is added in to create a final image which has the selectivity of coherent filtering with the depth discrimination and low noise characteristic of large aperture incoherent illumination.
Cryo-SEM of particulate suspensions
Authors: Sheehan J. G. , Scriven L. E. 
Published: June 2020

Advances in particulate coatings for paper products and high-density recording media require an understanding of orientation, clustering, and cluster aggregation of submicron particles suspended in high volume fractions in liquid. Particles for paper coatings are typically platelets; for magnetic coatings, acicular, tabular, or compact metal oxide or composite grains. One goal is to visualize the dynamic microstructures behind the rheological properties of these suspensions.Fixation of liquid calls for cryo-techniques. Replication for TEM examination is difficult because clusters and cluster aggregates adhere to carbon support films in such a way as to interfere with imaging and even disrupt replicas. The best technique we have found is cryo-SEM with freeze-fracture and deep etching.A procedure similar to that for freeze-fracture replication for TEM was used. For each sample, a small drop was flattened between two copper sheets (Balzers BU 012 056-T and BU 012 054-T).
Ultrastructural Investigation of Human Atrial Myxoma
Authors: Siew S. , Leistikow E. 
Published: June 2020

Atrial myxomas are the most common cardiac tumor in the adult and they account for about one half of all primary tumors of the heart. The growth of the myxoma results in the formation of an intracavitary mass which encroaches upon the capacity of the chamber leading to impedance with both the inflow and outflow, with subsequent damming back of blood and diminution of cardiac output. In addition, myxomas often extend to the atrioventricular orifice and may interfere with valve function. The tumors are accessible to surgical resection, therefore, a correct clinical diagnosis may result in a complete cure.Eight atrial myxomas were studied by means of transmission electron microscopy. Scanning electron microscopy was performed on one of these cases. Five of the patients were female and 3 were male. The age range was 40 - 77 years with an average age of 56.6. Five of the myxomas were from the left atrium and 3 from the right. All of the tumors had been attached to the atrial septum.
Cytotoxic Effects of Diethylnitrosamine on Renal Tissue of Medaka Embryos
Authors: Norton W. N. , Gardner H. S. 
Published: June 2020

The use of specific species of fish as bioassay systems for carcinogenicity studies is a relatively new approach to the investigation of cellular transformation. As a result, there are considerable voids in our basic knowledge of the biochemical, cytochemical and ultrastructural manifestations of exposure to selective carcinogens. The Japanese medaka, Oryzias latipes, has served as a popular fish model for carcinogenicity studies, many of which have included diethylnitrosamine (DENA), a site-specific carcinogen for hepatic neoplasms. The primary objective of this investigation was to obtain ultrastructural information on the cytotoxic effects of a carcinogen demonstrated at a location other than the normal site of cellular transformation.Embryos of medaka were exposed to 3000 mg/L DENA for 48 hours, rinsed and held in clean water at 30°C. An additional group of embryos was maintained at 30°C in a tank of tap water and functioned as a control. At 50 weeks subsequent to the exposure, several fishes from each tank were removed, anaesthetized with tricaine methanesulfonate and the kidneys excised and processed for electron microscopy. Pronounced manifestations of cytotoxicity were evident in the epithelium of the proximal convoluted tubule.
Neural Degeneration in the Spiral Ganglia of C57BL/6 Mice
Authors: Cohen Glenn M. , Grasso Joseph S. 
Published: June 2020

C57BL/6 mice, along with several other mouse genotypes, have served as models for human presbycusis (age-related hearing losses). C57BL/6 mice and their genetic substrain C57/bl6 show progressively severe hearing losses, starting as early as 30 days postnatally. The hearing losses result from sweeping sensory (hair cell) and neural degeneration that begins in the basal end and advances apically. For the initial study of the spiral ganglia C57BL/6 mice, our two objectives were to develop criteria for identifying the different degenerative stages and determine Whether the same degenerative stages repeat themselves in both young and old mice.Female C57BL/6 mice of seven ages, ranging from 1 1/2 to 32 months, were examined. The ears were exposed to the fixative (3.5% glutaraldehyde [GA]) within cne min after sacrifice. The cochleae were decalcified in 5% EDTA in 3.5% GA, postfixed in 1% osmium tetroxide, and embedded in Araldite 502 epoxy. Semithin (1μ) sections were stained with toluidine blue or p-phenylenediamine; thin sections were stained with uranyl acetate and lead citrate.
Neutrophil Myeloperoxidase Destruction by Ultraviolet Irradiation
Authors: Hanker J. , Giammara B. , Strauss G. 
Published: June 2020

Only a fraction of the UV radiation emitted by the sun reaches the earth; most of the UVB (290-320nm) is eliminated by stratospheric ozone. There is increasing concern, however, that man-made chemicals are damaging this ozone layer. Although the effects of UV on DNA or as a carcinogen are widely known, preleukemia and acute myeloid leukemia (AML) have only rarely been reported in psoriasis patients treated with 8-methoxypsoralen and UV (PUVA). It was therefore of interest to study the effects of UV on the myeloperoxidase (MP) activity of human neutrophils. The peroxidase activity of enriched leukocyte preparations on coverslips was shown cytochemically with a diaminobenzidine medium and cupric nitrate intensification.Control samples (Figs. 1,4,5) of human bloods that were not specifically exposed to UV radiation or light except during routine handling were compared with samples which had been exposed in one of several different ways. One preparation (Fig. 2) was from a psoriasis patient who had received whole-body UVB phototherapy repeatedly.
Alpha Helices of TMV Visualized by Cryo-Electron Microscopy
Authors: Jeng T.-W. , Crowther R.A. , Stubbs G. , Chiu W. 
Published: June 2020

Tobacco mosaic virus (TMV) is a helical particle, the structure of which has been determined by X-ray diffraction. We chose it as a test specimen to investigate whether cryo-electron microscopy and computer image processing could reveal internal structure at high resolution in a non-crystalline specimen.Low dose images of TMV embedded in a thin layer of vitreous ice were recorded at 60,000 magnification in a JEOL100CX electron microscope equipped with a cold stacje at -148°C. The best images were selected for processing on the basis of their optical diffractograms. The defocus was determined from the image of the carbon film adjacent to the hole over which TMV particles were suspended. The defocus values of processed images ranged from 5000 to -10000 Å. The initial processing steps included masking out the selected segment of a particle, interpolating the image to make the axis of a selected particle segment parallel to the transform array, straightening the particle segment by a real space correlation and re-interpolation procedure. The computed structure factors from the straightened particle segment were corrected for the effects of defocus by applying a Wiener filter function.