bluuebunny/crossref_metadata_2025 huggingface dataset:
“In-Situ” Dislocation Channeling Studies in Neutron-Irradiated Molybdenum
Authors: Narayan J. , Noggle T. S.
Published: June 2020

Dislocation channels in neutron-irradiated molybdenum were first observed by Mastel, et al. (l) and later studied in more detail by Brimhall (2). Both of these studies were carried out on material deformed in bulk in which the channels were formed prior to preparation of microscope specimens. The present study employed Mo specimens which had been irradiated and deformed as bulk specimens, leading to dislocation channel structures of the type studied earlier, however, additional deformation has been introduced “in-situ” in the electron microscope to obtain information on the basic processes associated with dislocation channeling.

Fig. 1(a-c) shows the growth of the original channels Al and A2 with deformation in the microscope. The channels are widened by the passage of dislocations of one type, b=a/2[111], indicating that cutting mechanisms are not solely responsible for the removal of the dislocation loops since the dislocations cannot eliminate loops of all possible Burgers vectors by cutting reactions.
Sem Examination of an Overheated Aluminum Wired Electrical Receptacle
Authors: Clark E. J. , Ballard D. B. , Embree E. J.
Published: June 2020

The contact surfaces of an electrical receptacle that overheated during current cycling tests were examined by SEM and energy dispersive X-ray analysis. This was part of a study in the causes of overheating that occasionally occur in household electrical receptacles wired with aluminum cable. The 15 amp, 125 V duplex receptacle having brass wire-binding screws and brass terminal plate had been installed in a steel box with cover plate in a simulated wall. The aluminum wire used was No. 10 AWG NM Type. Each wireto-receptacle connection was made by stripping 2.5 cm of poly (vinyl chloride) (PVC) insulation from the end of the wire, making a planar 3/4 loop, inserting the loop between the screw head and the terminal plate and tightening the screw to 2 in lb torque (0.23 N.m). A thermocouple was attached to the break-off tab on the black wire (hot) terminal. The test cycle consisted of a 120 VAC, 15 amp load, ON for 3 1/2 h, OFF for 1/2 h. Two cycles were completed each work day.
The Use of Diffraction Pattern Information In Stem
Authors: Cowley J. M. , Jap Bing K.
Published: June 2020

For each position of the incident beam in a STEM instrument, a convergentbeam diffraction pattern is produced in the detector plane. Except in the idealized, impracticable case of single isolated atom specimens, the intensity distribution in this diffraction pattern contains information regarding the relative positions of atoms within the volume element of the specimen illuminated by the beam. If this intensity distribution is recorded, for example by use of a two-dimensional detector array (Fig. 1) rather than a single detector which integrates the intensity, the additional data available should allow additional information to be derived concerning the specimen. When radiation damage is not a problem, this should allow an improvement in resolution. For radiation sensitive specimens, this should allow the incident beam intensity to be spread over a larger area so that radiation damage is reduced.
Image Contrast for Dark-Field Stem
Authors: Cowley J. M.
Published: June 2020

It has been stated or argued by a number of authors that the image contrast for dark-field scanning transmission electron microscopy, using an annular detector, may be interpreted as for an incoherent imaging process in that the image intensity is given by convolution of the square of a specimen scattering function with a beam intensity distribution function:

IDF(r) = ϕ2 (r) * |g(r)|2 (1)

It has further been stated that this "linear" relationship applies even for strong phase objects (1).

It is necessary to evaluate the approximations on which these conclusions are based in order to determine their validity as a basis for quantitative image evaluation and image processing procedures. A straightforward analysis reveals that the most important limitations to the assumption of a relationship such as equation (1) arise because (a) it is valid only for weakly scattering objects and (b) it assumes that the intensity detected by the annular detector is proportional to the total scattered intensity.
Proposed Scheme for a Directional Low-Loss Detector
Authors: Wells Oliver C.
Published: June 2020

The conventional low-loss electron detector (1,2) is shown in Fig. 1. The electron beam strikes the specimen with a glancing angle of typically between 30° and 45°. The input grid G1 is held at +200V. The filter grid G2 is held at +200V to collect secondary electrons or at -19.8kV for low-loss work with an incident beam energy of 20keV. The scintillator is held at +10kV for secondary electron detection or at -10kV for low-loss work. Comparison pairs of micrographs are obtained by recording one image in each mode. The signalto- noise ratio is approximately the same in each case.

We are proposing to replace the single scintillator/light-pipe/photomultiplier system with a pair of such assemblies separated by a partition, such that an input electron will reach one or other of the scintillators, depending on which part of the input aperture it enters. The video waveform will be obtained using a sum-or-difference unit connected to the two photomultipliers.
Observations of Direct Non-Vertical Interband Transitions in Al and Si by Electron Energy-Loss Spectroscopy.
Authors: H. Chen C. , Silcox J.
Published: June 2020

Electron energy-loss spectra (at 75keV) of single crystal aluminum and silicon foils of [001] orientation were obtained by using an electron microscope (Hitachi HU-11A)-electron spectrometer (Wien filter) system. The operation of this apparatus has been described previously. In the present experiment, the microscope was operated in the selected-areadiffraction mode and the energy-loss spectra were recorded on photographic plates and subsequently obtained data by microdensitometry.

Figure 1 shows the loss spectrum in aluminum with momentum transfer q in the <100> direction. In addition to the usual bulk plasmons at 15eV and surface plasmons at 6.7eV, two dispersive peaks below the bulk plasmon peak are also observed. The first peak which is relatively sharp starts linearly from 1.5eV at q∼0 and levels off around 9eV at the zone boundary (q = 1. 55 Å-1) . This peak is due to the excitation of direct non-vertical interband transitions along the X-W-X direction of energy bands in Al. The second peak, broad and diffuse with energy higher than the first one, has approximately linear dispersion which extends beyond 12eV and shows no sign of leveling off at large q.
Development of a Field Emission Stem and its Application to Element Analysis
Authors: Nomura S. , Todokoro H. , Komoda T.
Published: June 2020

The Scanning Transmission Electron Microscope (STEM) has made possible specimen observation with a number of advantages such as high signal collection efficiency. In addition, STEM also permits element analysis of micro-areas, when it is used in conjunction with X-ray and/or electron spectrometers. These advantages become more effective by using a high brightness electron gun.

The authors have developed a field emission STEM. The schematic diagram of the instrument is shown in Fig. 1. Electrons emitted from the tungsten tip are focused on a specimen by one electro-static and two magnetic lenses. The field emission tip is surrounded by ion pumps, and the vacuum of the gun chamber is maintained at better than 5xlO-10torr.
A Liquid Helium Cryostat for a Superconducting Objective and Cold Stage
Authors: Worsham R. E. , Mann J. E.
Published: June 2020

In the design of the 150 kV High-Coherence Column, it was considered essential that the specimen be in ultra-high vacuum at liquid helium temperature for minimum radiation damage. It followed that the simplest solution was to make the entire region about the specimen at liquid helium temperature and to make the objective lens with a superconducting winding.

For mechanical rigidity, two things were considered essential. First, a strong support structure for the liquid helium vessel and the objective lens. Second, the use of no liquid nitrogen but rather the use of helium vapor cooling for the radiation shields, leads and supports. The drawing, fig. 1, shows the helium vessel, 9-1/2-inches diameter by 5-inches tall, surrounded by two concentric radiation shields. The entire assembly is rigidly supported on four posts one of which is shown. These posts consist of cylinders of epoxyglass (G-10) spacing the components between their different temperatures.
Magnetic Material Observation Assembly for Tem with a Eucentric Goniometer
Authors: Shi rota K. , Yonezawa A. , Shibatomi K. , Yanaka T.
Published: June 2020

As is well known, it is not so easy to operate a conventional transmission electron microscope for observation of magnetic materials. The reason is that the instrument requires re-alignment of the axis and re-correction of astigmatism after each specimen shift, as the lens field is greatly disturbed by the specimen. With a conventional electron microscope, furthermore, it is impossible to observe magnetic domains, because the specimen is magnetized to single orientation by the lens field. The above mentioned facts are due to the specimen usually being in the lens field. Thus, special techniques or systems are usually required for magnetic material observation (especially magnetic domain observation), for example, the technique to switch off the objective lens current and Lorentz microscopy. But these cannot give high image quality and wide magnification range, and furthermore Lorentz microscopy is very complicated.
Practical Means for Enhancing the Contrast of Carbon Black Aggregates in Electron Micrographs for Quantitative Image Analysis,
Authors: Heckman F. A. , Connolly J. E. , Redman E.
Published: June 2020

The first goal of the work described below was to investigate and establish means for producing ultra high quality photographic images for automated image analysis. This procedure was absolutely mandatory because no reliable quantitative automated image analysis can be done with images which are deficient in any one of a number of essential properties. The second goal was to achieve a high degree of reproducibility in preparing the image. In order to achieve these goals we set out to optimize our image characteristics heuristically.

We have found that high contrast is the most important factor in attaining superior image quality in electron micrographs of carbon blacks. The individual factors which affect image contrast in electron micrographs have been discussed in the literature.
Weak Beam Imaging and Diffraction Studies of Stacking Faults in Silicon
Authors: Tan T. Y. , Tice W. K.
Published: June 2020

In studying ion implanted semiconductors and fast neutron irradiated metals, the need for characterizing small dislocation loops having diameters of a few hundred angstrom units usually arises. The weak beam imaging method is a powerful technique for analyzing these loops. Because of the large reduction in stacking fault (SF) fringe spacing at large sg, this method allows for a rapid determination of whether the loop is faulted, and, hence, whether it is a perfect or a Frank partial loop. This method was first used by Bicknell to image small faulted loops in boron implanted silicon. He explained the fringe spacing by kinematical theory, i.e., ≃l/(Sg) in the fault fringe in depth oscillation. The fault image contrast formation mechanism is, however, really more complicated.
The High Intrinsic Creep Strength of Non-Stoichiometric Ni2Alti
Authors: Polvani R. S. , Strutt P. R. , Tzeng Wen-Shian
Published: June 2020

It has been demonstrated (1) that the creep strength of the B2-type structure alloy NiAl (β-phase) can be enhanced to a remarkable degree by the addition of Ti which promotes the formation of the Heusler-type structure phase Ni2AlTi(β’). This phenomenon was attributed to the stabilization of dislocation networks at the semi-coherent (∼1%mismatch) phase interfaces. Now, recent observations are presented suggesting that this strengthening actually arises from the high intrinsic creep strength of the non-stoichiometric β and β’ phases.

Fig. 1 shows creep strength at 1000°C as a function of Ti content for a series of alloys along the NiAl-Ni2AlTi tie-line; creep strength is defined as the stress to maintain a steady state rate of 10-7 sec-1. The phase regions along the tie-line were determined from precise lattice parameter measurements.
Changes In The Distribution And Morphology of γ' Precipitate In Neutron Irradiated Pe-16
Authors: Sklad P. S. , Bentley J.
Published: June 2020

Nimonic PE-16 is a γ' hardened, austenitic alloy which has been chosen as a candidate for fuel element cladding and structural component applications in future breeder reactors due to its attractive high temperature strength properties and swelling resistance. The γ' phase is an ordered fee structure of LI2 symmetry having a Ni3(Al, Ti) composition, and is generally found as a finely distributed, spherical, coherent precipitate.

Cylindrical (∽6 mm diam x ∽10 mm length) specimens were machined from rod and then solution treated at 1313 K for 2 hr followed by an aging treatment of 2 hr at 1073 K plus 16 hr at 973 K. Specimens were irradiated in the EBR-II at temperatures in the range 650 to 823 K and to fluences in the range 1.2 to 4.0 x 1026 n.m-2 (E >0.1 MeV). Details of the swelling and mechanical properties will be reported elsewhere.
Precipitation in Partially-Stabilized Zirconia
Authors: Porter D. L. , Heuer A. H.
Published: June 2020

Precipitation in commercial partially-stabilized zirconia (PSZ) has been studied in order to facilitate "alloy design" in these materials. The commercial material used in this study is a 2.8 wt. % MgO alloy and has the cubic flourite structure at its sintering temperature. Upon cooling, a nearly MgO-free ZrO2 phase with tetragonal symmetry precipitates, which on further cooling inverts martensitically to a phase with monoclinic symmetry. At room temperature, commercial PSZ's therefore consist of a cubic solid solution matrix containing monoclinic precipitate; size, morphology, and distribution of the precipitate phase strongly influence mechanical properties.

Figures I and II show typical microstructures of the material as it is commercially produced. Both large and small precipitates are present (Figure I), indicative of precipitation over a range of temperatures during slow cooling through the two-phase region. Figure II shows heavily-twinned monoclinic particle; such large particles produced during commercial fabrication are believed to be deleterious to the mechanical behavior.
Effect of Steroids on Uterotubal Junction: An Ultrastructural and Cytochemical Study
Authors: Nayak R. K. , Wu A. S. H.
Published: June 2020

The morphology, and histology of mammalian uterotubal junction have been extensively studied. Only a limited number of electron microscopic studies on this organ have been published. Furthermore, adequate data on the fine structure and ultracytochemistry of this organ are not available. Investigation of this subject, therefore, was initiated on the tubal junction of the intact prepubertal and ovariectomized rabbit to delineate changes induced by near physiologic levels of exogenous estrogen and progesterone. Experimental procedure is the same as reported previously.

Two distinctive cell types, namely ciliated and secretory, are observed in the epithelia. The most obvious change after hormonal stimulation is the regeneration of cilia and basal bodies in the ciliated cells and the frequent extrusion of mucin-like granules into the tubal lumen (Figs. 1,3,4). Polysomal associations and fibrous granules are frequently seen in the cytoplasm of ciliated cells.
Z Bands in Developing Heart Muscle of the Mexican Salamander, Ambystoma mexicanum
Authors: Lemanski Larry F.
Published: June 2020

Electron-dense plaques, often seen in association with the plasma membranes of pre-heartbeat salamander myocardial cells, appear to be directly involved in early Z band formation. In differentiating myocardial cells of higher vertebrates, Z band material has been observed in close proximity to the plasma membranes and as isolated electron-dense material in the deep cytoplasm. The present study explores the fine structural features of Z band formation in salamander myocardium from early tailbud embryos (Harrison stage 25) through the adult. Hearts were fixed In a 0.1 M phosphate buffered formaldehyde-glutaraldehyde-picric acid-styphnic acid mixture and were post-fixed and embedded using standard methods.
Structural Organization and Distribution of Fiber Types in Extraocular Muscles of Cats
Authors: Nag Asish C. , Peachey Lee D.
Published: June 2020

Cat extraocular muscles consist of two regions: orbital, and global. The orbital region contains predominantly small diameter fibers, while the global region contains a variety of fibers of different diameters. The differences in ultrastructural features among these muscle fibers indicate that the extraocular muscles of cats contain at least five structurally distinguishable types of fibers.

Superior rectus muscles were studied by light and electron microscopy, mapping the distribution of each fiber type with its distinctive features. A mixture of 4% paraformaldehyde and 4% glutaraldehyde was perfused through the carotid arteries of anesthetized adult cats and applied locally to exposed superior rectus muscles during the perfusion.
Morphometric Analysis of the Slow-Twitch Fibers of the Guinea Pig
Authors: Eisenberg Brenda R. , Kuda Aileen , Peter J. B.
Published: June 2020

The soleus muscle of adult guinea pigs is composed entirely of slow-twitch fibers which stain moderately for oxidative enzymes and lightly for myofibrillar ATPase. The homogeneity of fiber type allows a quantitative ultrastructural study to be made by the point counting stereological method of Weibel. Longitudinal sections of well-fixed muscle fibers were used to obtain the preliminary morphometric data. This analysis excludes the region within 1 µ of the sarcolemma where there may be a higher volume fraction of mitochondria. Transverse sections were taken to provide additional anatomical information.

The mitochondria, which are elongated, are not uniformly distributed along the length of the fiber but tend to lie on either side of the Z disc (Figs. 1 and 4) and are sparse in the A band (Figs. 1 and 3).
Changes in Light and Dark Adapted Planarian Photoreceptors
Authors: Carpenter Kay S. , Morita Michio
Published: June 2020

The planarian Dugesia dorotocephala was used as the experimental animal to study the ultrastructure in the photoreceptor cell under different light parameters. The experimental groups studied were nine days dark adapted (DA), nine days natural light cycle (LA), and nine days dark adapted followed by ten minutes light exposure (DA + LE). A red light was used for feeding and cleaning the dark adapted animals. Fixation was in 2.5% glutaraldehyde followed by 1% OsO4.

The most noticeable changes occured in the stalk area of the receptor cell located directly below the rhabdomeric microvilli. The mitochondria in light adapted animals were observed to exist in both swollen and contracted conditions.
Comparative Scanning Electron Microscopic Study of Inner Ear Sensory Hair Cell Regions of the Lemon Shark
Authors: Rauchbach Erol , Arenberg I. Kaufman
Published: June 2020

There are five discreet regions of sensory epithelia within the membraneous labyrinth of the inner ear of the lemon shark, Negaprion brevirostris: The macula utriculus, macula sacculus, macula lagena, macula neglecta, and crista ampullaris. These five regions were studied by SEM to determine the population distribution, polarization, and for direct comparison of their particular hair cell types. Intravital perfusion of the membraneous labyrinth was performed with shark buffered:4% glutaraldehyde, 1% OsO4, or Parducz fixative and the various sensory regions were isolated during microdissection.
Structural-Functional Correlations in Inner Ear Receptors
Authors: Lewis Edwin R.
Published: June 2020

Transduction mechanisms are only partially understood in the sensory organs of the inner ear; and the roles of the receptor cells themselves with their magnificent elaborations of microvilli (stereocilia) and true cilia (kinocilia) are almost completely unknown. Certain clues are available, however. For example, scanning and transmission electron micrographs strongly suggest that the directional sensitivity known to be present in these receptors is imparted to them by the mechanical properties of the anisotropic array of stereocilia. Another clue may lie in the length and shape of the kinocilium.

In bullfrog, Hillman found that, almost every receptor of the saccular macula has a kinocilium that is expanded at its distal end to form a large bulb (Fig. 1) which is connected to the tips of the several longest stereocilia and to the membrane supporting the otolith. Thus the entire kinocilium is no longer than the longest stereocilia.
The Electron Microscope in Clinical Diagnosis
Authors: Lee John C.
Published: June 2020

Electron microscopic examination of surgical biopsy material is occasionally used in teaching hospitals as an aid to tissue diagnosis. Although the value of ultrastructural studies in a surgical pathology laboratory is undisputed in some instances, electron microscopy often merely serves to satisfy scientific curiosity and has little advantage over good light microscopy.

In 1967 an electron microscope service unit was installed as part of the surgical pathology laboratory of the University of California, San Francisco, and has been utilized for ultrastructural studies on a fee-for-service basis. Some of the income of this laboratory is derived from fees paid from research grants for the examination of various experimental animal tissues. A large proportion, however, stems from fees for examining human biopsy material. Hospital insurance carriers are willing to pay reasonable amounts for this service when it benefits the patient.
Structural Changes in Animal Lungs Exposed to Low Concentrations of Ozone
Authors: Boatman E.S. , Sato S. , Frank R.
Published: June 2020

There is considerable interest and speculation about the possible effects of ozone on the function and structure of the lung. Evidence is accumulating that ozone attacks the respiratory system at many levels including the larger more central airways, the smaller peripheral airways, components of the blood-air barrier and alveolar macrophages.

The present study is concerned with the functional, morphological, and ultrastructural changes in the respiratory system of animals exposed to low concentrations (either 0.25, 0.5, or 1.0 ppm) of O3 for 3 hours. Both cats and rabbits were used.
Alveolar Surface Structure in Induced Acute Respiratory Insufficiency
Authors: Liss Robert H. , Molokhia Farouk A. , Daly Benedict D.T. , Ballantine Thomas V. N. , Norman John C.
Published: June 2020

Death among patients following trauma, shock or sepsis is frequently attributable to a secondary episode of acute respiratory insufficiency. Initial hemodynamic problems may be successfully managed only to be followed by progressive, irreversible pulmonary failure.

In this study, scanning electron microscopy has been used to assess alveolar surface topography in a canine model of induced respiratory insufficiency (ARI). Mongrel dogs were infused with saline intermittently, continually and continually with intermittent furosemide treatment. Ultrastructural and pathophysiologic correlates of ARI were seen only in dogs which were fluid-loaded continually at 100 ml/kg/hr for 4-6 hours, and not treated with furosemide.

In acute pulmonary edema produced by continuous fluid overloading, the alveolar cell-air interface was altered. Scanning electron microscopy revealed focal pathology in edematous areas.
Structure and Transfer of Spermatozoa in Phoronopsis viridis
Authors: Zimmer Russel L.
Published: June 2020

Spermatozoa of members of the phylum Phoronida are usually of a highly atypical V-shaped morphology and are characteristically packaged into spermatophores by the male. Neither the submicroscopic organization of the spermatozoa nor the functional significance of the spermatophore has been reported previously.

Phoronopsis viridis were collected intertidally at Morro Bay, California. Spermatophores collected after release from the males were fixed in bicarbonate-buffered osmium tetroxide, dehydrated, embedded in epon, and sectioned for light and electron microscopy. Additionally, fresh spermatophores were placed on the lophophores of adults in EDTA-treated sea water; stages in the lysis of the spermatozoan mass through the tentacular wall were prepared at various intervals using the above procedure.
Accessory Nuclei in Hymenopteran Oocytes
Authors: Aggarwal Surinder K.
Published: June 2020

The ovary of Monomorium pharaonis (Hymenoperta: Myrmicidae) consists of a group of ovarioles, each consisting of an anterior germarium region formed of some cells that are undifferentiated or are in the process of differentiation and a more posterior vitellarium region consisting of a series of well differentiated polytrophic chambers. Each polytrophic chamber consists of a complex of 28-31 nurse cells interconnected by ring canals to a single oocyte and surrounded by a layer of follicle cells. In each ovariole the polytrophic chambers are lined up in a linear growth fashion determined by the amount of yolk deposited in the oocyte. In the previtellogenic stages the oocyte can be easily distinguished from the rest of the nurse cells by a less electron dense nucleus with synaptinemal complexes and a less pronounced nucleolus (Fig. 1).
Observations on Membranous Structures in Developing Mouse Oocytes
Authors: Dyer Robert F. , Ruby John R. , Skalko Richard G.
Published: June 2020

Ultrastructural studies designed to investigate oocyte development in ICR mice revealed the presence of membranous structures within certain oocytes. These structures are initially observed 18 days after fertilization. Morphologically the membranous structures are elongate and are characterized by increased density relative to other membrane structures in the cell. They may be found in the oocyte nucleus (Fig. 1) or cytoplasm (Fig. 2). The length and organization of the structures are variable, but one type of morphologic arrangement is seen more frequently than others. This type is characterized by a slightly bowed appearance and a thin membranous middle section that is vesiculated at each end (Figs. 1 and 2, arrow).
Fixation Induced Structural Changes in Chlamydomonas reinhardi (Wild Type) Chloroplast Membranes
Authors: Kretzer Frank
Published: June 2020

The light reactions of photosynthesis (photolysis of water, photophosphorylation, and electron transport) require the structural integrity of the chloroplast membrane. This work attempts to chemically fix the chloroplast membrane of Chlamydomonas reinhardi (wild type) with minimal protein denaturation and lipid extraction. The molecular structure of these membranes can then be analysed in terms of their well defined biochemical functions.

Previous work by others on chemically fixed chloroplast membranes demonstrated either a unit membrane or a membrane composed of a small uniform repeat subunit. However, if the molecular structure of these membranes is to be preserved, the protein must not be denatured and lipids must not be extracted. This rules out the classical fixatives (OsO4. KMnO4, high percentages of glutaraldehyde) and acetone or ethanol dehydration.
Glutaraldehyde-Urea, Copolymerized with Glycol Methacrylate by Ultraviolet Radiation, As An Embedment
Authors: Pease Daniel C.
Published: June 2020

The proteins of tissues, embedded either in glutaraldehyde-urea polymerized under acidic conditions, or in glutaraldehyde-ammonia at neutrality, are poorly differentiated by conventional stains. In seeking an improved cytological image of protein systems in a water-containing embedment it was discovered that the glycol methacrylates (particularly hydroxyethyl methacrylate - HEM) can be truly copolymerized with a suitable glutaraldehyde-urea mixture. This was achieved by ultraviolet polymerization in the presence of trace amounts of benzoin, and with substantial water in the system. The chemistry involved is not yet understood.

The resin mixture is freshly prepared before use, and consists of 6 ml HEM, 5 ml 50% glutaraldehyde, 1.5 gm urea, plus a trace of benzoin, with the pH adjusted to 6.0-6.5 with drops of strong NaOH.
Chloroplast Ultrastructure Preserved by a Water-Containing Glutaraldehyde-Urea Embedment
Authors: Nir Izhak , Pease Daniel C.
Published: June 2020

Conventional techniques for preparing aldehyde-fixed chloroplasts for electron microscopy result not only in the loss of their lipids, but also their chlorophyll so that they become obviously bleached. This extraction is prevented by embedding in glutaraldehyde polymerized with urea in the presence of substantial quantities of water. Glutaraldehyde-fixed tissue then retains its green color into the final sections. As a consequence of these factors, ultrastructural arrangements and details of the grana membranes are thought to be preserved with unusual precision.

The thylakoids appear in precisely ordered arrays, individually separated by uniform translucent gaps 15-20Å wide, particularly well seen in sections stained with OsO4, vapor (Fig. 1).
Hepatopancreatic Secretions in the Isopod, Oniscus ascellus
Authors: Roberts John W. , Witkus E. R.
Published: June 2020

The hepatopancreas of the isopod, Oniscus ascellus, is comprised of two pairs of blind-ending diverticula which empty into the straight-line digestive system posterior to the foregut. The functional differentiation of the regenerative cells in the tip of each lobe was studied with the light and electron microscope by making alternate thick and thin sections from the blind-ending tip throughout the length of each lobe. Two types of cells specialized from the regenerative cells: B-cells, specialized for secretion and S-cells which function in absorption and storage of nutrients.

In the B-cells, the secretory vesicles first appear in association with rough endoplasmic reticulum and Golgi apparatus in the transitional region of the lobe, between the regenerative and mature glandular cells (Fig. l).
Electron Microscopy of Mitochondrial DNA From Rat Brain
Authors: Chowdhury R. Paul , Misra D. N. , Sadhukhan P.
Published: June 2020

The presence of deoxyribonucleic acid (DJNA) in the mitochondria of cells and tissues of vertebrates, invertebrates and plants is now well-established. The conformation of DNA has been extensively studied from highly purified preparations of mitochondria from liver, heart muscle and flight muscle and rarely from brain tissue. The present work has been conducted to study the structural form and length of DNA molecules of mitochondria from brain of albino rats.
Studies on the Ultrastructure and Mechanism of Secretion of the Salt Gland of the Grass Spartina
Authors: Levering C. Alice , Thomson William W.
Published: June 2020

As previously reported the basal cell of the salt gland in Spartina is partitioned by a system of paired membranes (Fig. 1, arrows). These membranes are infoldings of the plasmalemma which extend inward from the wall protuberances located on the wall between the basal and cap cell (Fig. 1, p). The long extracellular channels between the partitioning membranes are open to the wall protuberances and thus open in the direction of secretion. The channels are closed at the terminal ends deep within the cell. The partitioning membranes appear to be analogous geometrically to surface membranous channels in absorptive and secretory cells in animal tissues. Because of this remarkable similarity we have suggested that the standing-gradient flow system of solute linked water transport elucidated by Diamond and his associates 2-3 is the probable mechanism of fluid transport and secretion in the salt glands of Spartina.
Fine Structure of Pollen Grain Ektexine of Maize, Teosinte and Tripsacum
Authors: Banerjee Umesh C. , Barghoorn Elso S.
Published: June 2020

Using light microscope (LM) it was found very difficult to distinguish the ektexine (outer sculptured layer of exine) pattern of maize (Zea mays L.) pollen grains from that of its wild relatives teosinte (Euchlaena mexicana Schrad.) and tripsacum (Tripsacum spp.). At the magnifications obtained by LM, the pollen grain ektexine is faintly granular or netted. By the use of electron microscopy, however, it is possible to characterize their pollen ektexine patterns.

For scanning electron microscopy (SEM) acetolysed pollen grains were used. After acetolysis the pollen samples were washed several times in glass-distilled water to remove traces of acids. Each sample was dispersed in a drop of distilled water placed on specimen holders.
Application of the Analytical Electron Microscope EMMA-4 in Evaluation of Cellulase Activity
Authors: Weavers Barry A. , Bal Arya K.
Published: June 2020

In an attempt to localize cellulase activity at the electron microscope level, in aging quiescent root meristems of Allium cepa L, the end product (reducing sugar) of the substrate was allowed to reduce cupric salts into cuprous oxide, which resulted in localized dense deposits in the cell walls. In the absence of any data regarding the elemental composition of these deposits, it was necessary to use the facilities provided by the Analytical Electron Microscope, EMMA-4. This instrument, by the combination of conventional transmission images and X-ray microanalytical facilities, allows unambiguous identification of elements in cell components. The analytical devise of EMMA-4 consists of two fully focussing crystal spectrometers capable of high resolution wavelength dispersive analysis and either a gas flow non-dispersive detector or a solid state Si (Li) non-dispersive detector for energy dispersive analysis.
The Core Particles of Herpes and Adenoviruses
Authors: Henry Claude J. , Merkow Leonard , Pardo Matias , McCabe Carol
Published: June 2020

Electron microscopy of cells infected with either herpes simplex virus (HSV) or adenovirus type 2 (Ad 2) revealed small homogeneous particles in addition to mature virions in the nucleus of the cell. The size of HSV associated core particles was 35 nm (Fig. 1) while those found in adenovirus infected HeLa or Vero cells were 22 nm (Fig. 2). The 22 nm particles observed in Ad 2 infected cells aggregated in the nucleus and perinuclear area of the cells resulting in the formation of large crystalline structures as large as 20µ. By studying the antigenic and histo-chemical nature of the crystals, it was possible to determine the composition and nature of these particles.
Spontaneous Production of Type C Virus Particles in a Culture Derived from Rat Embryo Cells
Authors: Priori Elizabeth S. , Shigematsu T. , Myers B. , Dmochowski L.
Published: June 2020

Spontaneous release of type C virus particles in long-term cultures of mouse embryo cells as well as induction of similar particles in mouse embryo cell cultures with IUDR or BUDR have been reported. The presence of type C virus particles in cultures of normal rat embryos has not been reported.

NB-1, a culture derived from embryos of a New Zealand Black (NB) rat (rats obtained from Mr. Samuel M. Poiley, N.C.I., Bethesda, Md.) and grown in McCoy's 5A medium supplemented with 20% fetal calf serum was passaged weekly. Extracellular virus particles similar to murine leukemia particles appeared in the 22nd subculture. General appearance of cells in passage 23 is shown in Fig. 1. Two budding figures and one immature type C virus particle may be seen in Fig. 2. The virus particles and budding were present in all further passages examined (currently passage 39). Various stages of budding are shown in Figs. 3a,b,c,d. Appearance of a mature virus particle is shown in Fig. 4.
Artefacts Occurring During Freeze-Etch Preparation
Authors: Maul Helmut M. , Maul Gerd G. , Wessing Armin
Published: June 2020

Much effort has been put into the process to obtain undistorted biological specimens for use in electron microscopy. It has been well accepted that the main advantage of the freeze-etching method is to obtain cells stabilized in the living state. This method has proved to be a useful tool to study membrane structures. This communication deals with a number of artefacts which occur during the freeze-etching preparation.

The effect of glycerol treatment as an anti-freeze agent on the cellular membranes has not yet been completely solved. The interpretation of results must take into account the physical treatment during the steps of preparation. In order to avoid decreased viability others have added glycerol incrementally; however, in some cases alterationsin cellular structure have been reported.
Loss of Absorbed Lipid During Processing of Intestine for Electron Microscopy
Authors: Buschmann Robert J.
Published: June 2020

Since considerable, although variable, amounts of absorbed lipid are lost from intestinal epithelium during processing for electron microscopy, the following experiments were carried out to evaluate this loss during various, relatively new processing procedures.

Everted sacs of rat jejunum were incubated in a micellar solution of oleic acid-3H (1.0 mM), monoolein (0.5 mM), and sodium taurocholate (15.0 mM) for 30 min at 37°C. Samples of these everted sacs were processed for electron microscopy by four different procedures which are outlined in TABLE I. The radioactivity lost to the processing solutions and remaining in the infiltrated tissue was monitored by liquid scintillation counting.

Routine Processing included a single OSO4 fixation followed by ethanol (EtOH) dehydration, propylene oxide (PO) and Epon infiltration. The total loss of 3H-lipid was 67% of the total absorbed oleic acid-3H (TABLE II).
Electron Microscopic Observations on the Effects of Polymixin B Sulfate to Cell Walls of Chlamydia Organisms
Authors: Matsumoto Akira
Published: June 2020

Cell walls of the both types of bodies, mature elementary body(EB) and developmental reticulate body(RB) of Chlamydia psittaci appear the triple layered membrane in thin section. However, in the preparations shadowcast or stained negatively EB cell wall shows hexagonally arrayed structure composed of subunits, 180A in diameter on the inside surface, whereas RB cell wall does not have this structure. Chemical analysis demonstrated that EB cell wall contained a similar amino acid composition with the cell walls of gram-negative bacteria, such as E.coli. The bactericidal effect of polymixin group against gram-negative bacilli is understood that the drug affects to the cell wall and destroys its osmotic regulation. Electron microscopy on the effects of the drug against the gram-negative bacteria revealed the formation of numerous number of projections on the cell wall surface and leakage of cell content through the projections. The present report is concerned with further studies on the fine structure of EB cell walls based on the observation on their response to polymixin B sulfate.
Incorporation of Cholesterol into Peripheral Nerve Myelin
Authors: Rawlins Frank A.
Published: June 2020

Several speculations exist as to the site of incorporation of preformed molecules into myelin. The possibility that an autoradiographic analysis of cholesterol-1,2-H3 incorporation at very short times after injection might shed some light in the solution of that problem led to the present experiment.

Cholesterol-1,2-H3 was injected intraperitoneally into 24 tenday old mice. The animals were then sacrificed at 10,20,30,40,60,90,120 and 180 min after the injection and the sciatic nerves were processed for electron microscope autoradiography. To analyze the grain distribution in the autoradiograms of cross and longitudinal sections from each sciatic nerve myelin sheaths were subdivided into three compartments named: outer 1/3, middle 1/3 and inner 1/3 compartments.

It was found that twenty min. after the injection of cholesterol -1.2-H3 (Figs. 1 and 2), 55% of the total number of grains (t.n.g) found in myelin were within the outer 1/3 compartment, 9% were within the middle 1/3 and 36% within the inner 1/3 compartment
An Electron Microscopic Study of the Human Gastric Epithelia with Special Reference to the Cardinal Morphological Changes of the Chief Cells Induced by Insulin Stimulus
Authors: Saito Hiroshi , Asano Goro , Aihara Kaoru , Fukushi Katsunari , Yoshida Minoru , Kimura Ken
Published: June 2020

This short communication is dealt with the ultrastructural changes of the chief cells in insulin stimulus in chronic gastritic condition. The bio gastro-endoscopic biopsy was obtained and pepsin activity of the gastric juice was measured in respective cases. Regular insulin of 0.15U/kg was administrated intra-muscularly and in pre-administration of insulin, 10 minutes, 20 minutes and 30 minutes after administration, biopsied specimens were subjected for electron microscopic studies.

In the pre-treated chief cells, extensive development of the cysternal structures of the granular endoplasmic reticulum in basal aspect of the cytoplasm and spherical or oval shaped, light homogeneous zymogen granules in supranuclear region and especially apical aspect of the cytoplasm were featured. Moreover, other type of the chief cells as the one characterized by their fragmented and saccular dilated granular endoplasmic reticulum in basal aspect of the cytoplasm, also exist.
Ultrastructural Changes in Three Different Mammalian Cells Following Ultraviolet Laser Irradiation
Authors: Shankar Narayan K. , Gupta Kailash C. , Okigaki Tohru
Published: June 2020

The biological effects of short-wave ultraviolet light has generally been described in terms of changes in cell growth or survival rates and production of chromosomal aberrations. Ultrastructural changes following exposure of cells to ultraviolet light, particularly at 265 nm, have not been reported.

We have developed a means of irradiating populations of cells grown in vitro to a monochromatic ultraviolet laser beam at a wavelength of 265 nm based on the method of Johnson. The cell types studies were: i) WI-38, a human diploid fibroblast; ii) CMP, a human adenocarcinoma cell line; and iii) Don C-II, a Chinese hamster fibroblast cell strain. The cells were exposed either in situ or in suspension to the ultraviolet laser (UVL) beam. Irradiated cell populations were studied either "immediately" or following growth for 1-8 days after irradiation.

Differential sensitivity, as measured by survival rates were observed in the three cell types studied. Pattern of ultrastructural changes were also different in the three cell types.
Application of Electron Optics to Characterization of Particulate Pollutants
Authors: Moran J. B. , Miller J. L.
Published: June 2020

The Clean Air Act Amendments of 1970 provide the basis for a dramatic change in Federal air quality programs. The Act establishes new standards for motor vehicles and requires EPA to establish national ambient air quality standards, standards of performance for new stationary sources of pollution, and standards for stationary sources emitting hazardous substances. Further, it establishes procedures which allow states to set emission standards for existing sources in order to achieve national ambient air quality standards. The Act also permits the Administrator of EPA to register fuels and fuel additives and to regulate the use of motor vehicle fuels or fuel additives which pose a hazard to public health or welfare.

National air quality standards for particulate matter have been established. Asbestos, mercury, and beryllium have been designated as hazardous air pollutants for which Federal emission standards have been proposed.
Dynamic Focusing Techniques for Enhancing SEM Images
Authors: Yew Nelson C.
Published: June 2020

There are two major areas where Dynamic Focusing techniques can be used to enhance SEM image qualify and micrograph information content. When used in conjunction with the final condenser lens in the electron-optical column, it increases the effective depth of focus associated with an inclined specimen in the SEM. When used with an ultra-high resolution recording cathode ray tube it provides exceptional corner-to-corner sharpness on the micrograph.

Most commercial scanning electron microscopes use a tilted specimen positioned close to the final condenser lens with the secondary electron collector system located in the tilting direction to facilitate efficient electron collection. electron beam pivoting through the center of the principle plane of this lens to minimize distortion and off-axis aberration problems. As a result, the final electron beam is truly focused only along a portion of the spherical surface with its center located at the pivoting point.
Ultrahistochemical Analysis of the Chick Embryo Cornea Using A Non-Dispersive X-Ray Detector
Authors: Ohkura T. , Takashio M. , Watanabe T.
Published: June 2020

The experiments which we report here were performed to show qualitatively the presence or abscence of Cu in the mesostroma of the chick embryo cornea stained with alcian blue 8GS. Strips of the cornea were fixed in a buffered glutaraldehyde solution (2.5%, pH 7.4) and coloured with alcian blue 8GS at pH 2.5. Tissue specimens were postosmicated, dehydrated and embedded in Epon. Tissue blocks for the conventional transmission electron microscopy were prepared without alcian blue treatment, and the thin sections were stained with uranyl acetate and/or lead citrate. Fig. la shows the mesostroma of 3rd day chick embryo cornea; filaments run in various directions, and reveal no visible periodicity. Interfibrillar substances can not be demonstrated by the conventional method of the electron staining. The alcian blue treatment reveals the interfibrillar substances, which stand out in contrast as shown in Fig. lb.
X-Ray Safety of Electron Microscopes
Authors: Parsons D. F. , Phillips V. A. , Lally J. S.
Published: June 2020

This investigation was initiated to provide the first assessment, from the users viewpoint, of the health hazards of X-ray leakages from conventional (40-200 Kv acceleration voltage) electron microscopes. Scanning microscopes were not considered at this point.

X-rays are produced in the electron microscope when the beam strikes metal parts of the instrument. The degree of X-ray leakage depends on two factors--the intensity of the X-ray source and the amount of metal shielding surrounding it. The efficiency of total (continuous and characteristic) X-ray production is approximately proportional to the atomic number of the metal and to the acceleration voltage (platinum apertures are three times as efficient as the iron of pole pieces). However, the fraction of beam striking the metal has to be taken into account and the efficiency of the shielding. The thickness (number of Half Value Layers), the effect of absorption edges on X-ray transmission, and the cracks or openings in the shielding all have to be taken into account.
Scanning Transmission Microscopy Applied to Thick Specimen
Authors: Koike H. , Matsuo T. , Ueno K. , Suzuki M.
Published: June 2020

Since the identification of single atoms was achieved by Crewe et al, scanning transmission microscopy has been put into pratical use. Recently they applied this method to the quantitative mass analysis of DNA.

As pointed out previously the chromatic aberration which decreases the image contrast and quality, does not affect a scanning transmission image as it does a conventional transmission electron microscope image. Thus, the STEM method is advantageous for thick specimen. Further this method employs a high sensitive photomultiplier tube which also functions as an image intensifier. This detection method is effective for the observation of living specimens or easily damaged specimens. In this respect the scanning transmission microscope with high accelerating voltage is necessary.

Since Uyeda's experiments of crystalline materials, many workers have been discussed how thick specimens can be observed by CTEM. With biological specimens, R. Szirmae reported on the decrease in the image contrast of rabbit psoas muscle sections at various accelerating voltages and specimen thicknesses.