bluuebunny/crossref_metadata_2025_split huggingface dataset:
On The Mechanism of Formation of Stacking Faults in Aged Nickel-Base Alloys
Authors: Rowe G. M. , Rand W. H. , Kear B. H. 
Published: June 2020

The formation of stacking faults upon aging a solution treated and quenched nickel-base alloy has been reported previously. More recent work has revealed a similar behavior in several γ’ precipitation hardened nickel-base alloys aged in the temperature range l400°-1650°F. The faults intersect both γ (nickel solid solution) and γ’ (Ni3Al solid solution) phases, and are of extrinsic type. Fault formation is attributed to a chemical segregation effect involving the climb of Frank partials, similar to that reported for austenitic steels.Fig. 1 shows extrinsic faults associated with a slip band in Udimet 700 lightly deformed at 70°F prior to aging. For the specified [011] normal to the foil, the slip trace is (11), and the faults lie in (111) and (11). Using the g · b = 0 or ± 1/3 (s = 0) criterion for dislocation invisibility, Figs, 1 (a-c) show that the outer partial for a (111) fault must be 1/6 [11] Shockley, or 1/3 [111] Frank.
Residual Gas Reactions in the Electron Microscope: I. Qualitative Observations on the Water Gas Reaction
Authors: Hartman Richard E. , Hartman Roberta S. , Ramos Peter L. 
Published: June 2020

The action of water and the electron beam on organic specimens in the electron microscope results in the removal of oxidizable material (primarily hydrogen and carbon) by reactions similar to the water gas reaction .which has the form:The energy required to force the reaction to the right is supplied by the interaction of the electron beam with the specimen.The mass of water striking the specimen is given by:where u = gH2O/cm2 sec, PH2O = partial pressure of water in Torr, & T = absolute temperature of the gas phase. If it is assumed that mass is removed from the specimen by a reaction approximated by (1) and that the specimen is uniformly thinned by the reaction, then the thinning rate in A/ min iswhere x = thickness of the specimen in A, t = time in minutes, & E = efficiency (the fraction of the water striking the specimen which reacts with it).
Development of Electron Mirror Microscope
Authors: Someya T. , Watanabe M. 
Published: June 2020

Our electron mirror microscope has been improved by adopting magnetic lenses, which enable a wide range of magnification to be obtained. This improved version, known as the JEM-M1 (35kV acceleration) uses the straight design and shadow projection method.The construction of the newly designed instrument is illustrated in Fig. 1 and Fig. 2 shows a sectional view of its electron optical column. The electron gun assembly is located under the console table. Incident beam alignment is carried out by means of the deflection coil knob, the electron gun horizontal movement knob and the condenser lens knob located on the table. The zircaloy crystal located above the screen and on the optical axis enables the alignment procedure to be carried out easily and simply because it radiates light when impinged by the electron beam. The projector lens, having a short focal length, combined with the condenser lens, forms a small source for the shadow projection image on its back focal plane. The intermediate lens, acting on the reflected beam, produces image magnification by changing the excitation current. Magnification in the range x200 – x1500 is possible without any appreciable distortion.
Some Aspects of Contrast in High Voltage Electron Microscopy
Authors: Metherell A. J. F. , Fisher R. M. , Duff W. R. , Buchanan R. 
Published: June 2020

In view of greater penetration at high accelerating voltages, the column approximation method of calculating cartographic plots of image intensity bear examination. Results of theoretical considerations of several aspects of contrast in high voltage microscope will be presented and illustrated with relevant electron micrographs.(1) Column Approximation - In the column approximation for a crystal with a crystal with a small distortion due to a dislocation, stacking fault, etc. two assumptions are made; (a) that the direct and diffracted waves propagating through the crystal do not diverge and (b) that the same value of the Bragg deviation parameter x can be used for the waves excited on the different branches of the dispersion surface, regardless of the angle the local crystal distortion makes with the Brillouin zone boundary. Takagi has obtained differential equations which take into account the divergence of the beams as they pass through the crystal.
Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope
Authors: Welton T. A. 
Published: June 2020

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance andrelativesimplicity, in as much as the problem of enzyme structure seems to be amuchmore difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.
A High Resolution Scanning Microscope
Authors: Crewe A. V. , Wall J. , Welter L. M. 
Published: June 2020

A scanning microscope using a field emission source has been described elsewhere. This microscope has now been improved by replacing the single magnetic lens with a high quality lens of the type described by Ruska. This lens has a focal length of 1 mm and a spherical aberration coefficient of 0.5 mm. The final spot size, and therefore the microscope resolution, is limited by the aberration of this lens to about 6 Å.The lens has been constructed very carefully, maintaining a tolerance of + 1 μ on all critical surfaces. The gun is prealigned on the lens to form a compact unit. The only mechanical adjustments are those which control the specimen and the tip positions. The microscope can be used in two modes. With the lens off and the gun focused on the specimen, the resolution is 250 Å over an undistorted field of view of 2 mm. With the lens on,the resolution is 20 Å or better over a field of view of 40 microns. The magnification can be accurately varied by attenuating the raster current.
The Possibility of Improving Scanning Microscope Images by After-Treatment
Authors: Thomson M. G. R. , Crewe A. V. 
Published: June 2020

The scanning electron microscope is particularly suited to the after-treatment of the image because the information is obtained in serial form, and may be processed using electronic analogue or digital computers. The techniques employed at present include logarithmic amplification, differentiation, and the subtraction of a constant intensity; all of these being intended to render low contrast detail more visible, and so making staining of the specimen less necessary.One further technique is the removal from the final picture of some of the effects of the finite size of the scanning electron beam. Essentially this involves construction of the Fourier transform of the picture, division by the Fourier transform of the scanning spot, and Fourier transformation of this result. It is possible to perform these operations in the case either of a scanning or conventional microscope by digitising the picture, doing the calculations numerically, and reconstructing the improved picture.
Observations in Polycrystalline Ceramics by Electron Transmission Microscopy
Authors: Tighe N. J. 
Published: June 2020

Polycrystalline ceramic compacts can be thinned for transmission electron microscopy by ionic bombardment. The present paper describes this technique and presents some results of studies on ceramic bodies of different composition, grain size and porosity. Thinning was done in an apparatus which was designed by Paulus and Reverchon who used it to thin single crystal specimens. The apparatus uses two ion sources so that specimens placed between them can be thinned from both sides.The polycrystalline specimens were thinned using argon ions at an accelerating voltage of 5 - 8 kV and a beam current of ∼ 100 μA/cm2. The thinning rate depended on the voltage and beam current and varied with the specimens and was 0.1 to 1 μm/hr. The thinning progress was monitored with a microscope mounted on the vacuum chamber and by removing the specimen from the chamber and measuring the thickness with an optical microscope. The specimens were prepared for the ion thinning by mechanical grinding and polishing.
Electron Microfractography Applied to Large Pipe Bending Fatigue Tests
Authors: Wolff Ursula E. 
Published: June 2020

Among the different causes of pipe failures, fatigue cracking has to be considered in any design program. Since the integrity of nuclear reactor piping is of particular importance, an AEC pipe study program includes a task to assess quantitatively the crack propagation rate through pipes for cracks originating at surface flaws. This problem has been attacked theoretically by the use of fracture mechanics, and practically by striation measurements on fracture surfaces produced by full-scale bending fatigue tests. This paper deals with the practical aspect of applying electron microfractography to such fractures as a means to determine crack propagation rates in pipes of different dimensions and materials, and with different flaw locations.Six-inch diameter pipes with a wall thickness of 7.5, 10.8, or 18 mm were notched inside or outside and failed in reverse bending fatigue by growing a crack through the wall thickness. The crack front was marked at intervals by reducing the strain amplitude for a number of cycles.
Identification of Nodules Present on Reduced Iron Ore Particles
Authors: Bailey G. W. 
Published: June 2020

In the fluidized reduction of iron ore, certain operating conditions result in the formation of nodular growths on the ore particles. These growths begin to appear even at very low metallization. The size and number of these nodules have varied with the reducing conditions and have been found to be particularly dependent on reduction time. The nodules are usually only a few microns in size. The structure and composition of these nodules have been investigated using a variety of physical techniques including:∘ Optical microscopy∘ Electron microscopy∘ Electron probe analysis∘ X-ray diffractionNodular growths were detected initially on reduced iron ore particles by optical microscope examination of mounted and polished cross-sections of the partially reduced particles (Figure 1). In an effort to determine the composition of the nodules, electron probe analysis was conducted on the mounted specimens.
Laboratory and in-situ analysis of comet dust
Authors: Brownlee D.E. , Albee A.L. 
Published: June 2020

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.
Nanometer-scale motion analysis of microtubule-based motor enzymes
Authors: Gelles J. , Schnapp B.J. , Steuer E. , Sheetz M.P. 
Published: June 2020

Kinesin and cytoplasmic dynein are mechanochemical ATPases thought to transport vesicular organelles within cells by moving them along microtubules. Molecules from purified enzyme preparations will bind to plastic microspheres (beads) and move them along microtubules in vitro at rates of ∽0.5 μm s-1. Bead movement can be directly observed by light microscopy in an assay that provides an opportunity to study motions driven by small numbers of enzyme molecules. Measurement of such motions with nanometer-scale precision yields information about the molecular events which drive bead movement.We devised a method to measure the relative position o£ an enzyme-driven 150nm bead with a precision better than 1 nm at 30 Hz2. This method is based on digital processing of bead images in differential interference contrast microscopy using a cross-correlation/centroid algorithm.
Techniques for analyzing conventional histologic sections
Authors: Shelburne J.D. , Ingram P. , Tucker J.A. 
Published: June 2020

Despite the many known artifacts attendant to conventional processing and staining, one of the most common types of medical microprobe analysis involves the use of routine histologic sections. Formalin-fixed, paraffin embedded tissue sections are particularly useful for cases involving inorganic particulates or insoluble, tightly bound exogenous metals. These sections are technically easy to prepare and usually offer much greater surface area than is available with plastic embedding for electron microscopy. Figure 1 reviews our approach to the analysis of this type of specimen.After identifying a feature of interest such as unknown particles, the microscopist then must decide if the feature is prevalent and homogeneous or rare and unique. In the former case, serial sections are cut from the paraffin block at 5-10 μm and picked up onto spectroscopically pure, ultrasmooth carbon planchets. Paraffin tissue sections readily adhere to the carbon substrate after heating at 60°C for 30 minutes, followed by deparaffination in xylene and air drying.
3-D imaging of cells using a confocal laser scanning microscope and digital image processing
Authors: Jovin Thomas M. , Robert-Nicoud Michel , Arndt-Jovin Donna J. , Schormann Thorsten 
Published: June 2020

Light microscopic techniques for visualizing biomolecules and biochemical processes in situ have become indispensable in studies concerning the structural organization of supramolecular assemblies in cells and of processes during the cell cycle, transformation, differentiation, and development. Confocal laser scanning microscopy offers a number of advantages for the in situ localization and quantitation of fluorescence labeled targets and probes: (i) rejection of interfering signals emanating from out-of-focus and adjacent structures, allowing the “optical sectioning” of the specimen and 3-D reconstruction without time consuming deconvolution; (ii) increased spatial resolution; (iii) electronic control of contrast and magnification; (iv) simultanous imaging of the specimen by optical phenomena based on incident, scattered, emitted, and transmitted light; and (v) simultanous use of different fluorescent probes and types of detectors.We currently use a confocal laser scanning microscope CLSM (Zeiss, Oberkochen) equipped with 3-laser excitation (u.v - visible) and confocal optics in the fluorescence mode, as well as a computer-controlled X-Y-Z scanning stage with 0.1 μ resolution.
Ceramic sol-gel transformations studied using cryo-microscopy
Authors: Bailey J. K. , Mecartney M. L. 
Published: June 2020

The preparation of ceramics from chemical precursors yields high quality materials. Sol-gel processing, one of these preparation methods, offers controlled purity, low temperature processing, and production of difficult shapes, such as fibers and coatings. Beginning as either a colloidal dispersion or a solution of inorganic monomers, the sol undergoes a gelation or polymerization reaction producing a solid body that incorporates the initial solvent. This body is then dried to remove the solvent and densified to produce either a porous or dense material as desired. In sol-gel processing, control over and understanding of the developing gel microstructure and how this microstructure influences the sintered properties is of vital importance. Furthermore, it has been difficult to determine the structure unambiguously.Using cryo-microscopy, direct observation of the microstructure of colloidal sols and the formation of the gel has been described in previous work.
Structure of Myosin Subfragment-1 from Electron Microscopy and Crystallography
Authors: Winkelmann Donald A. 
Published: June 2020

The primary role of the interaction of actin and myosin is the generation of force and motion as a direct consequence of the cyclic interaction of myosin crossbridges with actin filaments. Myosin is composed of six polypeptides: two heavy chains of molecular weight 220,000 daltons and two pairs of light chains of molecular weight 17,000-23,000. The C-terminal portions of the myosin heavy chains associate to form an α-helical coiled-coil rod which is responsible for myosin filament formation. The N-terminal portion of each heavy chain associates with two different light chains to form a globular head that binds actin and hydrolyses ATP. Myosin can be fragmented by limited proteolysis into several structural and functional domains. It has recently been demonstrated using an in vitro movement assay that the globular head domain, subfragment-1, is sufficient to cause sliding movement of actin filaments.The discovery of conditions for crystallization of the myosin subfragment-1 (S1) has led to a systematic analysis of S1 structure by x-ray crystallography and electron microscopy. Image analysis of electron micrographs of thin sections of small S1 crystals has been used to determine the structure of S1 in the crystal lattice.
Electron Spectroscopic Imaging of DNA and Protein-DNA Complexes
Authors: Bazett-Jones D.P. , Brown M.L. 
Published: June 2020

Elemental distributions in cells and molecular spreads can now be produced at the spatial resolution attainable in the electron microscope by the collection of X-rays or by the collection of and imaging with inellastically scattered electrons. With the latter method, known as Electron Spectroscopic Imaging (ESI), an image is produced with electrons that have lost characteristic amounts of energy from ionizing or exciting specific elements in the specimen. ESI can generate an elemental map of a specimen at a resolution of about 0.5 nm. It can be carried out in a fixed beam microscope equipped with a parallel energy filter inserted into the column of the microscope below the specimen (1,2). An instrument equipped with a prism-mirror-prism electron spectrometer was used in this study to image purified DNA molecules and a complex of the transcription factor TFIIIA with DNA.Transcription of most genes is activated by the binding of transcription factors to promoter elements.
Current State of Biological High-Resolution Scanning Electron Microscopy
Authors: Peters Klaus-Ruediger 
Published: June 2020

A new generation of high performance field emission scanning electron microscopes (FSEM) is now commercially available (JEOL 890, Hitachi S 900, ISI OS 130-F) characterized by an "in lens" position of the specimen where probe diameters are reduced and signal collection improved. Additionally, low voltage operation is extended to 1 kV. Compared to the first generation of FSEM (JE0L JSM 30, Hitachi S 800), which utilized a specimen position below the final lens, specimen size had to be reduced but useful magnification could be impressively increased in both low (1-4 kV) and high (5-40 kV) voltage operation, i.e. from 50,000 to 200,000 and 250,000 to 1,000,000 x respectively.At high accelerating voltage and magnification, contrasts on biological specimens are well characterized1 and are produced by the entering probe electrons in the outmost surface layer within -vl nm depth. Backscattered electrons produce only a background signal. Under these conditions (FIG. 1) image quality is similar to conventional TEM (FIG. 2) and only limited at magnifications >1,000,000 x by probe size (0.5 nm) or non-localization effects (%0.5 nm).
Ultrastructural Study of Peroxisome Proliferation in Hepatocytes by Quick-Freezing and Deep-Etching Method
Authors: Ohno S. 
Published: June 2020

It had been emphasized that luminar continuities between sER and peroxisomes were detected by conventional electron microscopy. However, recent studies ruled out the luminar continuities between sER and peroxisomes. Lazarow et al. reported that peroxisomal proteins were synthesized on free ribosomes and postulated the existence of “peroxisomal reticulum” distinct from the ER. The object of this study is to clarify the proliteration mechanism of peroxisomes after administration of a peroxisome proliferator, DEHP (di-2- ethylhexyl phthalate).Mice treated with 2% DEHP for 1, 3, 5 and 7 days and normal mice were perfused with 2% paraformaldehyde in 0.1M phosphate buffered solution, pH 7.4, (PB) for 5 min. The livers were cut into small pieces, washed in PB to remove cytoplasmic soluble proteins and were fixed again with 2% paraformaldehyde-0.25% glutaraldehyde for 30 min. They were quickly frozen in isopentane-propane mixture (around -190 C) and fractured in liquid nitrogen to remove the damaged surface tissues. They were deeply etched in Eiko FD-3S machine (-95°C, 2-6xl0-7 Torr) and rotary shadowed with platinum.
Freeze-Fracture Observations of Hamster Sperm-Egg Fusion
Authors: Clark Judy , Koehler James K. 
Published: June 2020

A number of TEM and SEM studies have made use of the hamster in vitro fertilization system to observe the process of sperm-egg fusion. We have extended these studies to include observations of freeze fracture replicas at the site of the sperm-egg interactions prior to, during and immediately following their fusion.Zona-free eggs were collected following superovulation of female hamsters according to the methods of Yanagimachi et al. Sperm were capacitated and prepared for incubation with eggs as in Clark et al. Eggs and sperm were co-incubated 5-15 minutes, washed and immediately fixed and prepared for freeze fracture replicas and thin sections as previously reported.In order to investigate the role of lipid components during the fusion process, some preparations were fixed in the presence of filipin, which binds to β-OH sterols in membranes and forms complexes that are visible in freeze fracture replicas. Thin sections were also prepared and viewed to help confirm and support observations of the replicas.