bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Study of trna, Using the High Resolution Scanning Electron Microscope
Authors: Langmore J. , Wall J. 
Published: June 2020

Individual molecules of yeast transfer RNA have been observed in the elastic dark field, inelastic dark field and “Z contrast” modes of the 5 Å high resolution scanning electron microscope. The operation, and contrast forming abilities of this instrument, are discussed elsewhere.Of particular interest here is the fact that the contrast in this microscope is very high, so that negative staining techniques are not required. This does, however, present a problem in specimen preparation. The single tRNA molecules are approximately 30 Å thick and 50 to 150 Å long and are supported only by a thin carbon film. Difficulties are being experienced at the moment in preserving the structure of the molecules during the specimen preparation stage.
Light Optical Diffraction Studies of Macromolecular Ultrastructure
Authors: Haydon Glen B. 
Published: June 2020

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.
Morphologic Chahges in Testicular Interstitial Tissue of the Rat After Crtptorchidism or X-Irradiation
Authors: J. Niewenhuis Robert , R. Basom Charles , T. Binhammer Robert 
Published: June 2020

Adult male rats were divided into five groups: (1 & 2) those surgically rendered either unilaterally cryptorchid or bilaterally cryptorchid; (3 & 4) those exposed to either unilateral or bilateral testicular x-irradiation and (5) a group of unilaterally cryptorchid animals which were treated with 100 I.U. of human chorionic gonadotrophin (HCG) for 21 days. Control animals were used for all groups. Tissues were fixed with glutaraldehyde using the whole body perfusion technique and post-fixed with osmium tetroxide. Epon 8l2 was used for embedment.Ultrastructural examination of interstitial cells from cryptorchid and irradiated testes revealed basic changes in the amount and organization of the smooth endoplasmic reticulum (SER). In interstitial cells from control animals the SER was arranged primarily in the form of anastomotic tubules.
Measurement of Radial Distortion
Authors: Reisner John H . 
Published: June 2020

Radial distortion is not usually an important problem in electron microscopy, and can in many applications be tolerated in amounts up to ten percent. However, when accurate quantitative results are required, or when a montage of photomicrographs is to be prepared, radial distortion must be taken into account.The scheme described for the measurement of radial distortion grew out of a need for a short procedure simple enough to be described over the telephone, and not requiring special or unusual test specimens. The procedure is undoubtedly not new; but the writer has never seen it published or used elsewhere, and in response to several suggestions has prepared it for publication.
Contrast & Resolution in Scanning Electron Microscopy using Backscattered Electrons
Authors: Ong P.S. 
Published: June 2020

Primary backscattered electrons are not widely used in scanning electron microscopy, despite the fact that they exhibit properties which cannot be duplicated by the use of secondary electrons. Among these are:
The backscatter coefficient depends strongly on the average atomic number of the specimen.The angular distribution of the backscattered electrons is similar to that of light, interacting with a diffuse sample. i.e., it exhibits a cosine distribution for normal incidence and approaching total re flection at grazing angles.By virtue of their high energy, they are not affected by small elec tric and magnetic fields, and thus travel in straight lines.
A Comparison of TEM and SEM Fractography
Authors: Hubbard James L. 
Published: June 2020

For many years now, metallurgists have been using replica techniques for electron micrographic studies of the fracture surfaces of metals. The general features which are indicative of a certain mode of fracture, such as fatigue, overstress, or stress corrosion, have become quite familar in a wide variety of alloys. Although replicas are subject to many artifacts these features are usually recognized as such and disregarded in the analysis of the surface. Also since negative replicas are generally used one must reverse his perspective in order to obtain a true mental picture of the fracture surface.With the scanning electron microscope, micrographs of such samples can now be taken directly with no surface replication or preparation involved. The scanning micrographs, while limited in resolution, present a picture not only true to the surface but with a stereo perspective with which one can relate the surface features to reality.
Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys
Authors: Christou A. , Foltz J. V. , Brown N. 
Published: June 2020

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.
The Ultrafine Structure of Carbon Fibers
Authors: Phillips V. A. , Hugo J. A. , Roberts B. W. 
Published: June 2020

High resolution phase contrast microscopy has been used to study the ultrafine structure of Morganite I and Thornel high modulus carbon fibers. Both are commercial fibers processed at 2800° to 3000°C, the former made from a polyacrylonitrile and the latter from an cellulose (rayon) precursor. Graphitizing is combined with stretching in order to align the basal planes parallel to the fiber axis to secure the high modulus. The ultrafine structures of these fibers have previously proved elusive.The fibers have been looked at in two ways. Since they are irregular in shape it was found possible to direct the electron beam normal to the fiber axis and image the basal planes viewed edge-on at the periphery of a fiber. The image disappears as one moves into the thicker region, so that only the structure near the surface is accessible. The second approach was to fracture the fiber by applying local bending stresses.
Unusual Microstructure in Shock-Compacted Graphite
Authors: Trueb Lucien F. 
Published: June 2020

Crushed and statically compressed Madagascar graphite that was explosively shocked at 425 kb by means of a planar flyer-plate is characterized by a black zone extending for 2 to 3 nun below the impact plane of the driver. Beyond this point, the material assumes the normal gray color of graphite. The thickness of the black zone is identical with the distance taken by the relaxation wave to overtake the compression wave.The main mechanical characteristic of the black material is its great hardness; steel scalpels and razor blades are readily blunted during attempts to cut it. An average microhardness value of 95-3 DPHN was obtained with a 10 kg load. This figure is a minimum because the indentations were usually cracked; 14.8 DPHN was measured in the gray zone.
Preparation of Thin Sections using a Fracture-Extraction Technique
Authors: Emma Thomas A. 
Published: June 2020

The preparation of thin sections for transmission electron microscopy by chemical or electrolytic thinning is time consuming and can introduce contamination. This is a serious problem when inclusions and precipitates in single crystals are being identified. A technique which reduces the likelihood of contamination and has the additional advantage that specimens can be prepared rapidly uses a fracture process followed by physical extraction. The method is also useful for studying defects generated at a fracture plane.The technique is a modification of a method reported previously for preparing thin glass sections. The specimen is fractured in a dry, inert atmosphere such as nitrogen or argon. The fracture surface usually contains fragments that have the proper shape and thickness to serve as thin sections.
Growth and Structure of Germanium Films Evaporated Onto Rock Salt
Authors: Shimaoka G. , Chang S. C. 
Published: June 2020

Recent studies of evaporated germanium films have demonstrated that their structure and epitaxy are greatly influenced by various evaporation parameters such as vacuum pressure, substrate surface conditions, and deposition rate as veil as substrate temperature. The purpose of this study is to investigate growth and structure of germanium thin films evaporated onto a clean rock-salt substrate in ultrahlgh vacuum and to find optimum epitaxial growth condition.High-purity (intrinsic) germanium was evaporated at various deposition rates, 0.1-5Å/sec, and thicknesses, 3O-5OOÅ, onto vacuum-cleaved and air-cleaved (001)NaCl substrates held at 25°-500°C in a vacuum of ∼10-8Torr. Some films were prepared under lateral electric field of dc 100V/cm or an electron-beam irradiation with ∼1015 electrons/cm2/sec, 300-400V, applied to the substrate during evaporation.
Optimum Stereo Tilt Facilities on the AEI Mk II High Voltage Electron Microscope
Authors: Beeston B.E.P. 
Published: June 2020

Stereo-imaging is essential to the full utilization of the increased specimen penetration available in the high voltage microscope. Biological specimens 0.25–5 μm thick, depending upon the density and specificity of staining, and metals and materials 0.1–7 μm thick, depending upon their density can be penetrated at adequate resolution at 1000-1200 kV. However, the considerable amount of overlapping detail observed in such specimens makes stereo-imaging essential for the full elucidation of the internal structure. In order that the final stereo pair of micrographs may be readily ‘fused’ by the observer to reveal optimum specimen ‘depth’, a number of requirements should be met:
1) The stereo tilt axis should be vertical when the two prints are laid side-by-side on the stereo viewer. This requirement is always met in the EM7 Mk II as the microscope incorporates a non-rotational imaging system for magnifications 4,000–1,000,000 X. By balancing the individual image rotations of the four imaging lenses against one another, a total rotation of zero between the specimen and the image is maintained. Now by tilting the specimen in the ±45° front-loading side-entry tilt rod, the image always ‘tilts’ about a vertical axis on the viewing screen, parallel to the long edge of a 6×9 cm sheet in the film camera.2) The magnification of the two micrographs should be as similar as possible.3) The two micrographs should be in as closely similar an orientation as possible.4) The focus of the two micrographs should be as similar as possible. (The deviations in 2), 3) and 4) which can be accepted have been discussed in detail by Willis and Julesz).
Solubility Studies of Flame Retardant Cotton-Polyester Fabric Blends
Authors: Boylston E. K. , Muller L. L. , Goynes W. R. , Babin R. M. 
Published: June 2020

Because of increasing public awareness and strong legislative regulations, the production of nonflammable textile fabrics is essential. Generally, phosphorous-nitrogen polymers are very effective fire retardants, especially when applied to cotton fibers. Since many fabrics marketed today are blends of cotton and synthetic fibers, flame retardants that are compatible with these blends must be developed.Preliminary research on blended cotton-polyester fabrics treated with a mixture of tetrakishydroxyethylphosphonium chloride (THPC) urea, trimethylolmethylglycoluril (TMMGU), and polyvinylbromide (PVBr) has produced a flame retardant finish that is durable through 60 laundry cycles. This mixed emulsion was padded onto the fabric, dried, and heat cured to polymerize in situ on the surface and within the fibers. The polyvinylbromide was added because bromine compounds are known flame retardants and polyester has an affinity for polyvinylbromide.
A New Multiple Specimen Table for Freeze-Etching
Authors: Paik S. K. , Allen J. R. 
Published: June 2020

Considerable progress in freeze etching technique has been made during the last ten years. The purpose of this technique is the preparation of replicas for electron microscopy. The technique consists of four steps. After (a) freeze-fixation, (b) the specimen surface is fractured with a cooled microtome knife in the vacuum chamber, (c) etched by low temperature sublimation, and (d) a replica of the etched surface is produced by evaporation of platinum and carbon.The electron microscopic image obtained with a freeze-etched replica is highly dependent upon the quality of the replìcas. This quality is very easily affected by the thickness of the evaporated layer and the angle of shadowing.
A Detailed Exploration of the Axial Magnetic Field Distribution Within Lens Pole Pieces
Authors: Engler P. E. 
Published: June 2020

Contrast and resolution are the most crucial parameters in biological electron microscopy. These parameters are sensitive functions of spherical aberration and astigmatism. Axial astigmatism is produced by a rotational asymmetry in the axial magnetic field distribution Bz (r, ) in the objective pole piece, and is adjusted with a stigmator that locally compensates for the rotation asymmetry. Spherical aberration is frequently determined from a measurement of the on-axis field distribution only; it is presupposed that the axial field distribution is rotationally symmetric and that the pole piece axes are coliniar straight lines.Commercial probes used to measure axial magnetic fields in conventional electron microscope pole pieces are so large that off-axis fields cannot be measured, and consequently the degree of rotational symmetry cannot be assessed.
An Experimental System Combining Medium Energy Electron Diffraction and Scanning Electron Microscopy
Authors: Cowley J.M. , Koch F.A. , Albain J.L. 
Published: June 2020

The theoretical and experimental advantages of using medium energy electrons (1-10 keV) instead of LEED and RHEED methods for quantitative surface studies were discussed by Moon and Cowley. A highly versatile ultra high vacuum system that exploits some of these advantages was constructed in our laboratory. The purpose of this paper is to describe design details of the instrument and to present initial data obtained.An overall view of the jinstrument is shown in Fig. 1. A commercially available field emission gun was attached to a Varian 240 LEED chamber. The pumping system is oil free and consists of cryosorbtion and Vaclon pumps.
Ultrahistochemical Studies of Mucosubstances : Electron Microscope Observation and Microprobe Analysis of the Chick Embryo Cornea
Authors: Ohkura T. , Iwatsuki H. , Watanabe T. 
Published: June 2020

As described in a previous report, Alcian blue provides the selective contrast enhancement of interfibrillar substances of the mesostroma of the chick embryo cornea. This finding was also verified by the electron probe microanalysis of adjacent sections. In the present study the nature of interfibrillar substances was ultrahistochemically examined by a modified Seligman's method for the demonstration of some oxidizable glycols.Strips of the 4th day chick embryo.cornea were fixed in ice-cold 2.5% glutaraldehyde solution (pH 7.4). Tissue specimens treated with 1% aqueous periodic acid or 0.2% hyaluronidase solution of pH 6.0 for 15 min were transferred into 1% thiocarbohydrazide, followed by a rinse in 1% osmium tetroxide solution (60°C, 50 min).
Cuticular Ridges in a Mite
Authors: Crowe John H. 
Published: June 2020

Many species of arachnids possess cuticular ridges, the function of which is not known. In the present investigation the structural properties of the ridges in a Trombidiform mite, Panonychus citri were studied, with a view towards discovering the function of the ridges.For scanning electron microscopy the animals were mounted on metal pos s previously coated with conducting silver paint. Best results were obtained by examining live animals, mounted on the posts immediately before examination. For transmission electron microscopy the animals were fixed in cacodylate-buffered glutaraldehyde, post-fixed in osmium, embedded in Spurr's low viscosity epoxy resin, and sectioned on diamond knives.
Virus-Like Particles in Leukemic AKR/J Mice as Revealed by Freeze Etching
Authors: Silver Burton B. , Goldstein Allan L. 
Published: June 2020

Leukemic and normal mice of the AKR/J strain, infected with Gross leukemia virus, were examined for electron microscopy using the freezeetch technique. The leukemic mice all had lymphocyte counts in excess of 25,000/mm3 and hyperplastic lymph nodes, spleen and thymus.The lymphatic tissues from normal and leukemic animals were strained through a fine fiberglass screen into phosphate-buffered saline at 4°C. The cells were centrifuged at 200XG at 4°C, the pellet was resuspended in phosphate-buffered saline with 25% glycerol and allowed to incubate in the glycerol solution for two hours before final centrifugation at 500XG. The glycerinated specimen was first frozen in Freon 22 and finally in liquid nitrogen. Freeze etching was carried out in a Denton apparatus at a pressure of 106 TORR and 100°C for one minute.
An Electron Microscopic Study of Mast Cells in Human Kidneys
Authors: Mandal A. K. , Nordquist J. A. , Muehrcke R. C. , VoIini F. I. 
Published: June 2020

Mast cells are widely distributed throughout the body and normally are present in almost every organ. Although mast cells are absent in normal kidneys, large numbers have been reported in kidneys with chronic inflammatory diseases. The granules in cutaneous mast cells show a positive flourescence for dopamine and norepinephrine suggesting that these cells may contain vasopressor substances. The purpose of these studies was to determine the characteristics and frequency of mast cells in the kidneys of patients with renal disease and hypertension.Renal tissues from 25 patients with a variety of renal and urinary tract disorders were studied using electron microscopy (RCA, EMU3H). Tissue was obtained by percutaneous biopsy in 17 cases, by nephrectomy in 6 and by autopsy in 2.
Morphology of Human Amniotic Fluid Cells
Authors: Cutz E. , Conen P. E. 
Published: June 2020

Prenatal diagnosis of many inherited diseases is based on studies using cultured AF cells, and therefore morphologic studies on amniotic fluid (AF) cells have increased in importance. However, the nature, morphology and origin of AF cells which grow in tissue culture remains unsettled. In this study AF cells from the first trimester of pregnancy were examined by light, transmission (TEM) and scanning electron microscopy (SEM).Amniotic fluids (15-20 weeks of gestation) were examined from 11 patients undergoing therapeutic saline abortions and from four intact amniotic sacs with a foetus. Percentages of dead cells were determined using Trypan blue stain, and differential cell counts were made using cytocentrifuge sedimented AF cells stained by Wright's stain and PAP stain.
Fibroblasts During Hypertrophic Scar Formation and Resolution
Authors: Kischer C. W. 
Published: June 2020

The morphology of the fibroblasts changes markedly as the healing period from burn wounds progresses, through development of the hypertrophic scar, to resolution of the scar by a self-limiting process of maturation or therapeutic resolution. In addition, hypertrophic scars contain an increased cell proliferation largely made up of fibroblasts. This tremendous population of fibroblasts seems congruous with the abundance of collagen and ground substance. The fine structure of these cells should reflect some aspects of the metabolic activity necessary for production of the scar, and might presage the stage of maturation.A comparison of the fine structure of the fibroblasts from normal skin, different scar types, and granulation tissue has been made by transmission (TEM) and scanning electron microscopy (SEM).
Preparation of Articular Cartilage for Scanning Electron Microscopy
Authors: Zimny M. L. , Redler I. , Fernandez J. 
Published: June 2020

The relationship between tissue preparation and a scanning electron microscopic image is still somewhat nebulous. For purposes of answering comments about our observations of articular cartilage, we decided to prepare tissue samples from one area of a femoral condyle, obtained at surgery, in several ways. As a result of this investigation we hoped to find the best way to prepare articular cartilage for maximal visual detail and subsequently standardize our procedures for a comparative study of normal and arthritic cartilage.The samples were fixed as follows: (1) no fixative; (2) 2% glutaraldehyde buffered with cacodylate, pH 7.4; (3) 10% buffered formalin; (4) 0.1% glutaraldehyde in Ringer's; and (5) 1% glutaraldehyde in Ringer's.
Electron Microscopy of Simian Lung Mites (Pneumonyssus Simicola)
Authors: Kim James C. S. 
Published: June 2020

Despite the demonstrated high incidence of lung mite infection in Old World monkeys, almost nothing is known of the life history and physiology of the parasite or the pathogenesis or the ecology of the disease. It is recognized that international quarantine regulation would not prevent importation of internal parasite such as lung mite. This raises serious concern as ticks and mites are arthropod which serve as both true reservoir and vectors.There is no published work of the ultrasturcture of Mesostigmata organs or tissues. In addition, urgent needs exist to rule out the possibility of this parasite acting as possible vector of unknown pathogens which has not been introduced to this country.
A Scanning Electron Microscopy Study of Sense Receptors of Cardiochiles Nigriceps (Hymenoptera)
Authors: Norton W. N. , Vinson S. B. , Thurston E. L. 
Published: June 2020

Antennal flagellar chemoreceptors of parasitic Hymenoptera function in such various capacities as courtship, host detection and selection. Chemoreceptors are classified according to the thickness of their cuticular wall as determined by the uptake of dye and monitored by light microscopy. A thickwalled chemoreceptor usually possesses a single small opening at the tip, whereas a thin-walled chemoreceptor possesses many small openings in the cuticle. Slifer employed this morphological distinction in her investigations of the sense organs of the parasitic wasp Nasonia vitripennis.Scanning electron microscopy of C. nigriceps flagellar sense receptors has provided knowledge concerning their morphology, abundance and distribution.