bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thin section microanalysis of zeolite Y
Authors: Hall J. B. 
Published: June 2020

Zeolite Y, a remarkably stable zeolite widely used in catalyst formulations, is a synthetic aluminosilicate with the faujaslte structure. It is distinguished from zeolite X by having fewer Al atoms per unit cell and greater stability. Y can be made even more stable by further reducing the number of Al atoms per unit cell to form ultrastable Y (U.S.Y). Because the Al/Si ratio of a zeolite is an important parameter affecting its properties, knowledge of the Al and Si distribution across individual particles is also important. A study of that distribution was therefore undertaken by electron microscopy. A catalyst preparation of 40% U.S.Y and 60% alumina was also analyzed.The samples were prepared for electron microscopy by embedding the particles in epoxy and cutting thin sections using an ultramicrotome. The thin section microanalysis was performed on a Philips 400T electron microscope equipped with a Tracor Northern TN2000 x-ray analyzer with digital beam control.
Surface structure effects of small particles
Authors: Castaño V. , Gömez A. , José-Yacamán M. 
Published: June 2020

Small particles of noble metals have been widely used in catalysis. In the past, very little has been known about crystal structure of this kind of particles. However, STEM microdiffraction patterns can now provide a great deal of information concerning the morphological characteristcs of these particles. In this comunication we report microdiffraction studies of small gold particles (∼ 100 Å) grown by evaporation onto KCl substracte. This investigation was carried out by comparing theoretical diffraction patterns from wedgeshaped crystals (with and without surface vacancies) with experimental microdiffraction patterns. The theoretical calculations have been based on the multislice formulation of Dynamical Theory.Fig. 1 shows a diffraction pattern of a gold particle. In addition of the (111) FCC zone, six forbidden reflections are clearly seen. These reflections have been observed in the past in films of gold and large gold particles.
Ultrastructural changes resembling nemaline body in congestive cardiomyopathy
Authors: Peng S.K. , Dickman P.S. , Abrams H.F. , French W. , Zamboni L. 
Published: June 2020

Transvenous endomyocardial biopsy, first introduced by Konno in 1962, has been an important tool for evaluation of disease of the myocardium, and frequently provides clinically useful information. This study reports a very unusual case of congestive cardiomyopathy in which endomyocardial biopsy tissue showed ultrastructural changes resembling those of nemaline body skeletal myopathy (2).A 60 year old man was admitted to the hospital with progressive dyspnea. He had a history of labile hypertension but was otherwise in generally good health. After admission, acute pulmonary edema developed after several days of progressive paroxymal nocturnal dyspnea. A congestive cardiomyopathy was diagnosed, as well as mild coronary artery disease. The ventricular ejection fraction was 20-30% by both echocardiogram and cardiac catheterization. There was also complex ventricular ectopy including nonsustained ventricular tachycardia. An endomyocardial biopsy was performed during transvenous catheterization.
Three-dimensional reconstruction from serial, electron microscopic autoradiographs of dividing rod precursors in the goldfish retina
Authors: Raymond Pamela A. , Rivlin Patricia K. 
Published: June 2020

When larval goldfish hatch, their retinas contain postmitotic, undifferentiated cones but no rods. Cones rapidly differentiate during the first few days of larval life. Meanwhile, rods begin to appear; they are produced by dividing, specialized progenitors - rod precursors - scattered across the retina. Rod precursors continue to divide throughout larval and into adult life, adding new rods to the growing retina. These dividing cells, intercalated among differentiated retinal neurons, are unique and have not been described previously. The purpose of this study was to identify rod precursors in the larval retina, to characterize them ultrastructurally and to reconstruct their morphology.Dividing rod precursors were labeled by 3H-thymidine injections in late larval/early juvenile goldfish (26-51 days posthatch). Survival times ranged from 1 to 48 hours; fish were decapitated, the corneas were punctured with an insect pin and the eyes (or whole heads) were fixed by immersion in a mixture of 3% glutaraldehyde, 3% paraformaldehyde, 0.1% picric acid, 1 mM calcium chloride, 0.1 M phosphate buffer (pH 7.4) with 5% sucrose.
Parallax stereograms obtained by using the Nimslo© process
Authors: Wittry D. B. 
Published: June 2020

Although popular interest in stereophotography has waxed and waned several times since the introduction of the Holmes stereoscope in the 1850's, the importance of stereophotography in scientific and technical applications has steadily increased. It has been of great value for contour mapping in geophysics and cartography, for displaying crystal and molecular structures, for locating and viewing internal structures in radioscopy, and for presenting 3-dimensional images obtained by optical microscopy, by x-ray projection microscopy and by electron microscopy.A persistent problem limiting the wider use of stereophotography has been the problem of viewing the image. Because stereo viewers are awkward to use, other methods of stereo viewing have been developed, including the following: 1) “reading in 3-D” with the use of eye training; 2) the use of a stereo pair with one image printed backwards and viewed with a plane mirror between the images; 3) the hologram method and 4) the parallax stereogram method.
The RS layer of a Pseudomonas species
Authors: Fraser G. H. , Hall M. , Murray R. G. E. , Whippey P. W. 
Published: June 2020

A Pseudomonas species, isolated from a feeder culture for Euglena viridis, shows an unusual form of tetragonal array on the external surface of the cell wall in negatively stained preparations. These regular surface [RS] layers have been demonstrated on a variety of gram positive and gram negative bacteria and form the primary interface between the cell wall and its environment. It is thought to function as a protective barrier layer against predators and other deleterious agents such as enzymes.Ammonium molybdate was the most effective negative stain at relatively high concentrations (4-8% w/v); uranyl acetate did not display the RS layer. The micrographs were investigated with the aid of optical diffraction and digital image enhancement. Areas of micrographs that were free from obvious irregularities such as stacking faults and uneven staining were selected visually, Fig. 1(a).
Spermatogenesis in Aeolidia papillosa (Nudibranchia)
Authors: Berlo Robert 
Published: June 2020

Spermatogenesis was studied in Aeolidia papillosa by disection of the ovotestis. Morphologically, developing spermatogonia and accessory cells are similar to those described in Spurilla neopolitana except for spermatid development. Sperm also were examined for the presence of carbohydrates. The reproductive tissue comprises the posterior two thirds of adult nudibranchs in the form of an ovotestis, divided into acini that contain both male and female follicles. The male follicles develop in the proximal half of the acinus. Accessory cells and early spermatocytes are attached to the basal laminal wall demarking each acini (Fig.1).Germinal spermatogonia give rise to large primary spermatocytes. The nucleus is spherical in shape, with an occasional eccentric nucleolus and scattered condensed chromatin, mostly located peripherally. The cytoplasm contains some mitochondria. The primary spermatocytes give rise to smaller trapezoidal secondary spermatocytes. These cells have nuclei with one or two large irregular nucleoli and scattered clumps of chromatin. The cytoplasm contains several Golgi complexes and mitochondria (Fig.1).
Phase Transformations in the Zirconium-Aluminum-Hydrogen System
Authors: Faulkner D. , Cameron D. J. 
Published: June 2020

Zr-Al alloys based on the intermetallic compound Zr3Al are presently being considered as structural materials for use in nuclear environments. Theoretically, the single-phase Zr3Al alloy should contain 8.97% Al, but in practice single phase material is not produced, and alloys containing approximately 8.0 to 8.5% Al contain a dispersion of α-Zr solid solution in the Zr3Al matrix (fig. 1). At higher Al concentrations Zr2Al may also be present.In this paper we describe the structures observed in a Zr-8.3% Al alloy containing up to 1300 μg/g hydrogen. Hydrogen was introduced into the alloy in two ways. The first technique involved the exposure of a weighed sample, at 650°C to a known volume of hydrogen at a predetermined pressure. The pressure was monitored during hydriding until it dropped to a value corresponding to the required uptake of hydrogen.
An Electron Microscope Study of Deformation-Strain Cycling Effects in 304 Stainless Steel
Authors: Staudhammer K.P. , Murr L.E. 
Published: June 2020

While there have been numerous experiments concerned with the effects of cold rolling and shock deformation on stainless steel residual structure, there have been no systematic attempts to investigate the effect of sequencing of these deformation modes for any material.In the present experimental program, type 304 stainless steel sheet was cold rolled (CR) 15 and 30% and incorporated (along with annealed, undeformed specimens) in a sandwich assembly for shock loading (SL), utilizing a flyerplate technique as previously described (at shock pressures of 150, 250, and 350 kilobars, and at a constant shock pulse-duration of 2.0 μ sec.
In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.
Authors: Louchet F. H. , Kubin L. P. 
Published: June 2020

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.
Conversion of an EM-200 to a Dual-Gun Electron Microscope for TEM and SEM
Authors: Brewer A. W. , Gold C. L. , Ong P. S. 
Published: June 2020

A Philips EM-200 electron microscope has been modified to incorporate two electron guns as described by Ong and Gold, for operation in the conventional (TEM) and scanning (SEM) mode.The second gun, the SEM gun, is mounted below the viewing chamber and uses the imaging system of the microscope as the probe forming electron optic. The electrons follow essentially the same path as the image forming electrons for TEM, only in the opposite direction.The modifications to the microscope column are designed to provide the space for the scanning coil assembly, the various detectors, and the second gun. A spacer is located above the objective lens to house the transmission electron detector, another spacer, below the objective lens, incorporates the scanning coil and a secondary electron detector.
A SEM Attachment for the Corinth Electron Microscope
Authors: Anderson K. , Brookes K.A. , Watson J.M. 
Published: June 2020

A scanning attachment has been designed for the Corinth electron microscope enabling either standard transmission images of thin specimens (TEM) or reflection scanning images of bulk specimens (SEM) to be obtained from the one instrument.At the heart of the modified instrument is a lens which acts as both the final projector lens for the TEM and also as the objective lens for the SEM with a working distance of 5mm. Thus even when used as a SEM the whole length of the Corinth column is traversed by the beam and this presents the choice of two possible modes of operation, namely, a two lens mode in which only the first condenser and final projector are excited, or a three lens mode in which the TEM objective lens is also excited. The three lens mode provides a range of much higher gaussian demagnifications.
A 10,000 Lines/Field Scanning Electron Microscope System
Authors: Jones G.A.C. , Ahmed H. , Nixon W.C. 
Published: June 2020

A special type of post-lens single deflection coils have been developed for use in various applications of micro electron beam technology. The coil geometry has been chosen to give small values of the uncorrectable aberrations and to correct for field curvature by dynamic focusing. With this system 10,000 lines/field may be used in scanning electron microscopy leading to electrical raster shift only to search a specimen. The same type of system could be used to produce high resolution special purpose displays or for direct electron beam photographic recording.In Figure 1 the lettered grid is 3 mm in diameter and the scanned circle is 9 mm in diameter.
The Unipotential Foil Lens
Authors: Wittels N. D. , Jacobsen E. H. 
Published: June 2020

We are investigating theoretically and experimentally the optical properties of an electrostatic unipotential lens whose center electrode is an aperture and whose outer electrodes are electron-transparent foils. This lens is potentially useful as a spherical aberration corrector for a high-quality magnetic lens.The electrostatic field inside the lens is calculated analytically from a Bessel-Fourier series expansion of the potential. This method gives results that are accurate in all regions of the lens, including those near the conducting foils, and readily allows the lens boundaries and excitation to be varied. The equations of motion are integrated numerically to determine the lens' optical properties. Since we are specifically interested in the aberrations of this lens, considerable effort has been made to assure the validity of the non-paraxial ray calculations.
Superior 2X2 Slides
Authors: Schaefer Harry , Wetzel Bruce 
Published: June 2020

High resolution 24mm X 36mm positive transparencies can be made from original black and white negatives produced by SEM, TEM, and photomicrography with ease, convenience, and little expense. The resulting 2in X 2in slides are superior to 3¼in X 4in lantern slides for storage, transport, and sturdiness, and projection equipment is more readily available. By mating a 35mm camera directly to an enlarger lens board (Fig. 1), one combines many advantages of both. The negative is positioned and illuminated with the enlarger and then focussed and photographed with the camera on a fine grain black and white film.Specifically, a Durst Laborator 138 S 5in by 7in enlarger with 240/200 condensers and a 500 watt Opale bulb (Ehrenreich Photo-Optical Industries, Inc., New York, NY) is rotated to the horizontal and adjusted for comfortable eye level viewing.
On Distinguishing between Small Vacancy and Interstitial Dislocation Loops Using a Non-Conventional Weak Beam Dark Field Technique
Authors: Wu Wei-Kuo 
Published: June 2020

It is well known that both the burgers vector and the habit plane of dislocation loops are needed in order to determine their type, e.g. vacancy or interstitial. The conventional bright field and dark field techniques give a dislocation image width ⋍300Å or an image shift from the core position even larger than the true size of a small dislocation loop. This makes loop type determination very difficult.In this paper, the newly developed weak beam dark field technique, which decreases the effective extinction distance, ξg, has been used to reduce the dislocation image width (∽1/3 ξg), so that the shape (habit plane) and loop types of small dislocation loops (<500Å) can be determined unambiguously.
Theory of Topographical Image Contrast
Authors: Nakahara S. , Cullis A. G. , Maher D. M. 
Published: June 2020

It has been shown recently that image contrast arising from specimen topographical structure may be obtained using the transmission electron microscope (TEM). The contrast was produced with an adaptation of the Foucault technique in which electrons suffering deviations of typically 10-4 to 10-3 rad were selected by the lateral displacement of a standard objective aperture. The mechanism of image formation was discussed in terms of electron refraction within the specimen inner potential, the contrast being amplitude in nature.In the present paper the imaging process is described by a detailed mathematical formulation.The theoretical treatment is based upon the concept of information theory for image transfer, in which successive Fourier transforms are utilized to derive the wave function of the image from an appropriate object.
Topographical Imaging in the Transmission Electron Microscope
Authors: Cullis A. G. , Maher D. M. , Nakahara S. 
Published: June 2020

A technique which employs an adaptation of the Foucault method for direct topographical imaging in the transmission electron microscope (TEM) was described recently. Image contrast is produced by selection, with a displaced objective aperture, of electrons which have been deflected through small angles within the specimen inner potential. In this manner, the aperture is employed effectively as a half-plane which, to a first approximation, removes half the spectra in the back-focal plane of the objective lens. The purpose of the present article is to illustrate the mechanism of image formation and also to demonstrate applications of the technique.Crystallites of MgO, formed by the combustion of Mg in air, are useful test objects since they have regular cubic geometry. When these were examined in the J EM 200 TEM under kinematical conditions and using an objective aperture in the half-plane position, they yielded images (after astigmatism correction) which exhibited topographical amplitude contrast.
The Accurate Measurement of the Energy Dependence of Radiation Damage Rates in Organic Materials
Authors: Howitt D. G. 
Published: June 2020

In electron microscopy and radiation damage studies in organic materials it is important to be able to make an accurate assessment of the rate at which the damage processes proceed.Approximate values for these radiation damage rates have been calculated using solid state detectors in order to measure the appropriate beam current densities, however the strong intensity dependence of these devices (Fig. 1) and their susceptibility to radiation damage imposes large errors when any consistency in their efficiency is assumed.A Faraday cup has been constructed (Fig. 2) which is capable of measuring currents down to 10-15 amperes cm-2 from the final image plane of an electron microscope, with an error of less than 1%. The cup, being positioned beneath the final viewing screen is therefore capable of distinguishing local incident intensities in the object plane.
Stereomicroscopy for Phase Objects by Use of Defocus Contrast
Authors: Nakahara S. 
Published: June 2020

The principles for obtaining stereomicrographs by transmission electron microscopy (TEM) with crystalline as well as non-crystalline specimens are well-established and are based on the introduction of parallax between two exposures by tilting a specimen inside a microscope. Previous applications of the technique have only been made to objects which give rise to amplitude contrast (provided by the elimination of electrons scattered outside the objective aperture). Recently, the technique has been further extended to objects, the images of which originate from phase contrast.The method employs defocus contrast for imaging such phase objects in combination with the conventional tilting operation. This paper describes the principle of the method and discusses a field of potential application.
Boron Precipitates in Ion Implanted Silicon
Authors: Wu Wei-Kuo , Washburn Jack 
Published: June 2020

Long rod-like defects are observed in ion implanted silicon when boron is present either as a prior dopant addition or as the implanted species. For many years, these rods have been described variously as precipitates, lines of point defects, dislocation dipoles, or elongated dislocation loops. The diffraction contrast from the defects has been difficult to interpret unambiguously because of their very narrow spacing. Our recent work indicates that they have the characteristics of narrow extrinsic dipoles or elongated dislocation loops and that there are two different types along each of the six <110> directions.In this paper, an alternative method, annealing kinetics, has been used to identify the nature of these defects formed during post-implantation annealing in boron ion (100 keV) implanted silicon irradiated at room temperature to a dose of 2x1014/cm2.
The Microstructure of Xe Implanted GaAs
Authors: Hills C. R. , Thomas G. J. , Stein H. J. 
Published: June 2020

Previous investigators have shown that the surface regions of GaAs samples implanted at room temperature with 40-100 keV Ne ions become amorphous after a dose of the order of 1x1014ions cm-2. Their study also indicated that implantation above room temperature (35°-200°C) results in the retention of crystallinity even with fluences two to three orders of magnitude higher. Investigators using ion backscattering and optical absorption have shown that ion dose rate is also an important variable in ion implantation. In the present investigation, transmission microscopy has been used to further study the temperature and dose rate effects of ion implantation in GaAs. A number of {111} and {l00} single crystal GaAs samples have been implanted with 275 keV Xe ions to doses of 1015 and 1016 ions cm-2 at dose rates ranging from 2.5x1012 to 8.1xl012ions cm-2 sec-1.Low dose (1015ions cm-2) implantations at room temperature produced amorphous layers at all dose rates.
Electron Microscopy of Frozen, Hydrated Biological Specimens
Authors: Taylor Kenneth A. 
Published: June 2020

Recently, a method has been developed in this laboratory for maintaining the hydration of biological materials by using frozen specimens. With this technique specimens are prepared using folding grids on which are mounted composite support films of carbon and SiO. The technique essentially embeds the biological material in a thin aqueous film between the two supporting films. The sandwiched specimens are then frozen directly in liquid nitrogen. While it was thought at first that freezing directly in liquid nitrogen might cause disordering of periodic or crystalline biological specimens, this has been shown not to be the case. High resolution electron diffraction patterns have been obtained from frozen unstained catalase crystals.The microscopy of frozen specimens depends on their resistance to damage by electron irradiation. The critical exposure for fading of the electron diffraction intensities from frozen unstained catalase crystals has been measured.
Morphological Observations on the Granule Types in Rabbit Extra-Adrenal Chromaffin Cells.
Authors: Mascorro Joe A. , Yates Robert D. 
Published: June 2020

Extra-adrenal chromaffin organs (abdominal paraganglia) constitute rich sources of catecholamines. It is believed that these bodies contain norepinephrine exclusively. However, the present workers recently observed epinephrine type granules in para- ganglion cells. This report investigates catecholamine containing granules in rabbit paraganglia at the ultrastructural level.New Zealand white rabbits (150-170 grams) were anesthetized with 50 mg/kg Nembutal (IP) and perfused with 3% glutaraldehyde buffered with 0.2M sodium phosphate, pH 7.3. The retroperitoneal tissue blocks were removed and placed in perfusion fluid for 4 hours. The abdominal paraganglia were dissected from the blocks, diced, washed in phosphate buffer and fixed in 1% osmic acid buffered with phosphate. In other animals, the glutaraldehyde perfused tissue blocks were immersed for 1 hour in 3% glutaraldehyde/2.5% potassium iodate buffered as before. The paraganglia were then diced, separated into two vials and washed in the buffer. A portion of this tissue received osmic acid fixation.