bluuebunny/crossref_metadata_2025 huggingface dataset:
Keratinocyte Cell Membrane of the Freeze-Fractured Human Epidermis
Authors: Hashimoto Ken , Parker Malcolm V.
Published: June 2020

Freeze-fractured keratinocyte membrane of the human epidermis revealed a relatively particle(arrows)-rich A-face (A) and a relatively particlepoor B-face (B)(Fig. 1). However, these so-called membrane-associated particles are not numerous even on the A-face, as compared with those of other tissues.

When the nexus or gap junctions were fractured, in most cases the B-face showed clustered cobblestone particles (c), instead of pits (Fig. 1). Cobblestone particles were 70-135 A in diameter and 0-25 A in height (Fig. 1). Much taller particles (50-70 A in height) were very often admixed (Fig. 1). In some instances. a macule of cobblestone particles (C) was seen in the neighborhood of a macule of depressed particles (D) showing the same dimensions (Fig. 2).
The Fine Structure of Glycocalyx in Human Spermatozoa. A High Resolution Cytochemical Study
Authors: Hernández-Jáuregui P. , Sosa A. , González Angulo A.
Published: June 2020

Glycocalyx is the name given by Bennett to the extracellular glycoprotein coat present in some cell surfaces. It appears to play an important role in cell properties such as antigenicity, cell adhesivity, specific permeability, and ATP ase activity. In the sperm this coat can be directly related to such important phenomena as capacitation and fertilization. The presence of glycocalyx in invertebrate spermatozoa has already been demonstrated. Recently Yanagimachi et al. has determined the negative charges on sperm surfaces of mammalian spermatozoa including man, using colloidal iron hydroxide. No mention was made however of the outer surface coat as composed of substances other than those confering a negative charge. The purpose of this work was therefore to determine the presence of a glycocalyx in human spermatozoa using alcian blue and lanthanum staining.
Neuron-Glia Relationship in the Brain of the Housefly, Musca domestica
Authors: Allison V. F. , Sohal R. S.
Published: June 2020

Relatively little is known regarding the structure and function of glial cells in the brain of invertebrate organisms. Fine structural aspects of the interrelationships between glial cells and neurons in the brain of the housefly are described. Three types of glial cells have been identified in the brain of the housefly. Cell bodies of the neurons and two glial cell types are located at the periphery of the brain and surround a centrally located neuropil. Soma of the neurons are completely surrounded by a single or multiple layers of glioplasm which precludes the existence of synaptic sites on the cell body (Fig. 1). Synaptic sites are restricted to the neuropil region. Thin processes of glioplasm also invaginated the perikaryon.
Ultrastructural Changes in Gonadotrophs of the Albino Male Rat after Castration or Treatment With Cyproterone Acetate
Authors: McArthur N. H.
Published: June 2020

Forty four animals were subdivided into the following groups with three animals per group, except for the intact group which contained five animals: Group 1. Intact; 2. Castrated and injected for 5 weeks with 1.25 mg testosterone beginning on the day of castration; 3-7. Castrated adults killed 1, 2, 3, 4, and 5 weeks postcastration; 8-12. Cyproterone acetate (10 mg daily in benzyl benzoate-castor oil) treated for 1, 2, 3, 4, and 5 weeks duration; 13. Castrated newborns killed as adults, and 14. Castrated new borns killed as adults, after daily injections of 1.25 mg of testosterone for 5 weeks.

Following decapitation the adenohypophyses were rapidly removed and fixed in 0.2M phosphate buffered Acrolein-Glutaraldehyde- Paraformaldehyde, postfixed in osmium tetroxide, stained en bloc with 2% uranyl acetate, and embedded in araldite-epon. Lead citrate stained sections were examined in RCA EMU-3c and RCA EMU-4b electron microscopes.
Comparative Ultrastructural Studies of the Pineal Gland of Rodents
Authors: Matsushima S. , Reiter R. J.
Published: June 2020

Electron microscopic observations of mammalian pineal glands have mainly been made on rodents, especially rats. However, there is no comparative ultrastructural investigation of pineals of various rodent species. In the present experiments several species of rodents were used, but here will be described primarily the results obtained from the mouse and chinchilla pineal glands. Pineals were immersed in ice-cold buffered 6% paraformaldehyde and 2% OsO4 mixture (1: 1) for 5 hours and embedded in the plastic mixture recommended by Spurr. Pinealocytes, the major cell type in the organ, show similar fine structural features in both mouse and chinchilla. These cells have lobulated nuclei and similar cytoplasmic organelles except that mouse pinealocytes contain numerous large granular vesicles of 1200Å in mean diameter. Other types of parenchymal cells are quite different between these animals.
Fine Structural Alterations of the Chief Cells in Hyperparathyroidism in Man
Authors: Thliveris J.A. , Dubé W.J.
Published: June 2020

Primary hyperparathyroidism has been associated with several clinical syndromes, of which recurrent renal calculi is by far the most common. To date, there has been a poor correlation between these clinical syndromes and the cell types of the parathyroid gland. In order to determine whether specific u 11rastructural abnormalities exist for the different hyperparathyroid syndromes, we examined by electron microscopy parathyroid tissue from 8 patients (5 renal calculi only, 2 osteitis fibrosa, 1 duodenal ulcer). All patients had hypophosphatemia (<3.1 mg %); seven patients had hypercalcemia (>10.5 mg %) and increased serum immunoreacti ve parathyroid hormone (PTH) concentrations (<1.7 ng/ml); and one patient had normal serum calcium (8.9-10.5 mg %) and PTH (0.74 ng/ml) levels. Light microscopy of the parathyroid glands from the seven patients with hypercalcemia revealed those features characteristic of parathyroid adenomas.
Cytochemistry of the Golgi Apparatus
Authors: Morré D. James , Vigil E. L. , Keenan T. W.
Published: June 2020

Concepts of membrane flow and membrane differentiation are combined to explain the formation of eukaryotic endomembranes along a sequence of cell components in subcellular developmental pathways. Membrane differentiation is the gradual conversion of membranes from one type to another and is documented by comparisons of enzymatic activities, lipid composition and progressive modification of the proteins and lipids of membranes along the endoplasmic reticulum (ER)-Golgi apparatus (GA)-secretory vesicle-plasma membrane (PM) export route. The biochemical studies show the transitional nature of GA membranes first revealed by morphological studies. Membrane dimensions and staining characteristics change progressively from ER-like to PM-like across the stacked cisternae from the forming to the maturing face of the apparatus. Membrane flow is the physical transfer of membrane from one cell component to another.
The Application of Ultracryotomy to Immunocytochemistry
Authors: Painter R. G. , Tokuyasu K. T. , Singer S. J.
Published: June 2020

A technique for localizing intracellular antigens with immunoferritin conjugates directly on ultrathin frozen sections of glutaraldehyde-fixed tissues has been developed. This method overcomes some of the limitations of previously described procedures, since it avoids drastic fixation, dehydration and embedding procedures which could denature many protein antigens.

Briefly cells or tissues were fixed with glutaraldehyde (0.5 to 2% for 1 hr), and ultrathin frozen sections were cut and mounted on grids covered with carbon-coated Formvar film by the procedure described previously. Such sections were stained with ferritin-antibody conjugates by methods described elsewhere.
Electron microscopy and diffraction studies of polyimides
Authors: de Hodgins O.C. , Lawless K. R. , Anderson R.
Published: June 2020

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.
Structure of crystals in dental enamel and synthetic hydroxyapatite
Authors: McLean J. D. , Nelson D. G. A.
Published: June 2020

Biological apatites in dental enamel, dentine and bone closely resemble, in chemical composition, the mineral hydroxyapatite with the unit cell Ca10(PO4)6(OH)2. Substitutions occur frequently, e.g. fluoride in place of hydroxy groups, carbonate for phosphate, and with other elements such as magnesium, zinc, strontium, and lead instead of calcium. The substituents are known to influence the response of the material to attack by dilute organic acids and are, therefore, of importance in the process of dental caries.

The sub-lattice resolution available with some modern electron microscopes makes it feasible to attempt detection of the effect of substituted groups on the structure of the hydroxyapatite crystals. As a starting point in such a venture we have obtained high-resolution images of apatite crystals and used computer image calculation techniques to interpret the micrographs at near-atomic resolution.
Dislocation dissociation in low-angle spinel boundaries
Authors: Ostyn K.M. , Carter C.B.
Published: June 2020

It is well known that in the spinel structure a perfect dislocation can dissociate into two partial dislocations with collinear Burgers vectors :

(1)

The two partial dislocations, which have the same character as the perfect dislocation, are separated by a stacking fault in the cation sublattice only. In ceramic materials, unlike fcc metals, dissociation of dislocations can occur by a climb mechanism in addition to, or instead of, dissociation by glide. Climb dissociation of perfect dislocations into two or more partials with collinear Burgers vectors has been observed in e.g. yttrium iron garnet and sapphire. Previous studies in spinels, deformed at high temperatures, emphasize climb dissociation and dissociation of mixed character. Dissociation of screw dislocations in stoichiometric MgAl2O4 spinel could not be resolved and hence no experimental measurements of the dissociation width have been reported.
Twinning in γ-Al2O3
Authors: Tucker Dennis
Published: June 2020

The spinel structure is well known for (111) twins. This twinning can be described as a reflection with respect to a (111) plane, as a rotation about a [111] direction by 60° or 180°, or as a rotation of 180° about a <112> axis. According to Hornstra, spinel twins can be bounded by two types of stacking faults (Type I and Type III). These stacking faults are part of an extended dislocation, as shown in Figure 1.

Table 1 shows the extended ABC notation of the spinel lattice. Referring to Figure 2, in Type I twinning, oxygen ion planes shear in [112] directions and result in an ABAB... stacking sequence. Type II twinning, in which the oxygen ion plane shear direction is [011], results in an FCC stacking arrangement. In Type III twinning oxygen ion planes shear in the [121] direction, resulting in an ABAB... stacking sequence. In types I and III, due to electrostatic considerations, the direction the cations move differs by 60° from that which the oxygen ions move.
Electron microscopy studies of plasma-sprayed materials
Authors: Subramanian K.R. , King A.H. , Herman H.
Published: June 2020

Plasma spraying is a technique which is used to apply coatings to metallic substrates for a variety of purposes, including hardfacing, corrosion resistance and thermal barrier applications. Almost all of the applications of this somewhat esoteric fabrication technique involve materials in hostile environments and the integrity of the coatings is of paramount importance: the effects of process variables on such properties as adhesive strength, cohesive strength and hardness of the substrate/coating system, however, are poorly understood.

Briefly, the plasma spraying process involves forming a hot plasma jet with a maximum flame temperature of approximately 20,000K and a gas velocity of about 40m/s. Into this jet the coating material is injected, in powder form, so it is heated and projected at the substrate surface. Relatively thick metallic or ceramic coatings may be speedily built up using this technique.
Irradiation behavior of pyrolytic silicon carbide
Authors: Lauf R. J.
Published: June 2020

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.
Interface morphologies in the polysilicon-SiO2 materials system
Authors: Bravman John C.
Published: June 2020

The fabrication of increasingly complex integrated circuit devices represents one of the most challenging areas of applied materials research. As layout geometries are reduced, device operation becomes more readily influenced both by the presence of various materials defects and by the structural integrity of the interfaces involved. Critical to the manufacture of such devices are the technologies associated with the deposition, doping, and oxidation of thin films of polycrystalline silicon (polysilicon). The strong interrelationship between the last two of these processes can result in the formation of unusual morphologies at the interface between the polysilicon and its thermally grown oxide. Conventional TEM has been applied to establish the nature of several such structures. Because their spatial extent is sometimes extremely small (e.g. 20A), high resolution lattice imaging was utilized in order to gain crystallographic information of a very fine scale.
HREM of interfaces and defects in semiconductors
Authors: Sinclair R.
Published: June 2020

It is recognized that interfaces constitute a most important component in semiconductor-based devices and that lattice defects adversely influence the performance of such materials. A basis for understanding these features requires intimate knowledge of their local structure and chemistry which can be provided to a large degree by high resolution electron microscopy (HREM). This article reviews some recent work in this area and indicates where alternative techniques can supplement the information provided by HREM.

High quality specimens are required for this work. They can be made by traditional means such as ion-beam milling or chemical polishing, although one must take care when using the former to avoid artifacts introduced by the energetic ion beam. Cross-sectioning is necessary to obtain topographic detail of interfaces, the procedure for which is somewhat more involved. Some details of this technique have been described previously.
Voltage contrast: A powerful tool for VLSI circuit diagnosis
Authors: Stivers A. R.
Published: June 2020

The advent of very large scale integration (VLSI) presents many new problems for integrated circuit (I.C.) diagnosis. Some I.C.s have over 100,000 transistors with less than 100 external leads with which the transistors can be tested. The geometries are now as small as 3 μm, smaller than can be probed mechanically. Along with the size, node capacitance and current drive are also reduced making a probe's capacitive load very detrimental to rise-time measurements. New processes have many layers of interconnect, leaving more and more of the circuit below passivation and therefore inaccessible to a mechanical probe, even after the removal of scratch protection. VLSI challenges I.C. diagnosis with more internal circuitry that becomes smaller and less accessible to conventional probes.

Voltage contrast is an electron beam voltage probing technique especially suited to VLSI circuits. A properly modified SEM, used in the voltage contrast mode, provides both high resolution images of circuit voltages and also voltage waveforms of particular nodes.
The high temperature reaction behaviour of biotite in pelitic xenoliths, Mull, Scotland: An AEM study
Authors: Brearley Adrian J. , Champness P.E.
Published: June 2020

Analytical electron microscopy has been used to study the mechanisms of metamorphic reactions in xenoliths of Moinian pelitic schist from a dolerite sill, Mull, Scotland. of particular interest has been the reaction behaviour of biotite mica during this low-P, high-T metamorphism. The biotite (∼k1.77(Mg1.81Fe3.26) Al3.65Si6O20(OH)4) shows a considerable darkening under the optical microscope and is, on occasions, almost completely black. High magnification examination indicated that the biotite had partially reacted and was intergrown with its reaction products on a very fine scale. Attempts to identify the new product phases by electron microprobe were unsuccessful.

Examination of several conventionally ion-thinned foils of biotite has provided important data on the nature of the reaction processes and reaction products involved. It has been shown that the biotite reacts on a highly localised scale and that equilibrium has not been reached. Only at the very edges of the grains is there any evidence of a reaction involving adjacent phases, usually quartz.
Synthetic aluminous goethite investigated by high-resolution transmission electron microscopy
Authors: Dixon J. B. , Golden D. C. , Calhoun F. G. , Buseck P. R.
Published: June 2020

Goethite (alpha-FeOOH) contributes significantly to aggregation and color of soils. Since goethite of soils usually occurs in low concentrations its investigation would be enhanced if it can be synthesized in a pure form especially if it resembles its form in soils by being fine grained and with some Al substitution. This report presents morphological and structural information on synthetic aluminous goethite prepared by a simple laboratory procedure. Aluminum substitution greater than 11 mole % appreciably reduces crystal size and increases the tendency for aggregation.

The surface crust of a botryoidal goethite from Biwabik, MN, USA (Source: Wards Natural Science Establishment, Rochester, NY) was crushed in acetone to a fine powder. A series of pure goethites also was prepared from Fe(CIO4)2 and A1(CIO4)3. The synthetic samples were then digested in a bomb for 17 hr at 150°C. All samples were dispersed in an ultrasonic water bath for 30 minutes prior to dip mounting on Cu grids coated with a holey carbon mesh.
Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results
Authors: Blake D. F. , Allard L. F. , Peacor D. R.
Published: June 2020

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.
Explosive consolidation of amorphous iron-base alloy powder
Authors: Shankar S. , Murr L.E. , Hare A.W.
Published: June 2020

Amorphous metals and alloys, and especially the metallic glass ribbon or Metglas alloys developed by Allied Corporation, have been shown to have very remarkable properties. There is special interest in magnetic iron-base alloy ribbon which is finding commercial uses in electromagnetic laminate applications such as transformers. There is intense interest in fabricating other metal glass structures, but conventional powder metallurgy techniques are intractible even when amorphous powders are available because of the dramatic property degradation when crystallization occurs at elevated temperatures.

Recent research has demonstrated that metal and alloy powders can be efficiently consolidated using explosives. The resulting materials can have unique microstructure and properties, and under certain circumstances, interparticle melting does not seem to occur, and particle bonding is apparently achieved by a kind of “mechanical mixing” similar to that explored earlier by Benjamin, and more recently by Kang. In addition, Murr, et al have also recently demonstrated that the passage of strong shock waves through amorphous (glassy) iron-base ribbon at pressures as high as 30 GPa (and 2 μs pulse duration) did not induce crystallization.
Interpretation of high-resolution TEM images of substitutional systems with a column structure
Authors: Van Tendeloo G. , Van Dyck D. , Amelinckx S.
Published: June 2020

Direct interpretation of high resolution electron microscope images in terms of the projected potential or projected charge density is only possible for very thin specimens and at a properly chosen defocus value. In most of the substitutional alloy systems such as those based on the fee basic lattice in which electron diffraction is strongly dynamical the useful crystal thickness is limited to the order of 1 nm which is rearly met in practice. Furthermore for almost all of the available electron microscopes the Scherzer plateau of the contrast transfer function is not large enough to contain even the first Bragg beams that carry information about the fee lattice. Nevertheless it has been shown in a number of papers on ordering in fcc-based Au-Mn alloys as well as in other heavy metal fee based alloys that under suitable conditions the images represent the structural features of these alloys in a directly interpretable manner. In particular the configuration of the minority atom columns can be imaged as bright dots. We shall indicate here semi-analytically why and under which conditions this conclusion is justified.
A HREM study of the interfacial structure of γ' precipitate plates in an Al-15 wt % Ag alloy
Authors: Howe J.M.
Published: June 2020

The interfacial structure and growth kinetics of γ' and γ (Ag2Al) precipitate plates in Al-Ag alloys have been extensively studied by conventional TEM methods. Although most results have confirmed the predictions of the general theory of precipitate morphology proposed by Aaronson, some new questions have arisen. The present study is an attempt to address the specific points of contention concerning the details of ledge growth in this system.

An Al-15 wt % Ag alloy was solution treated at 500°C for 30 minutes, quenched and aged for 30 minutes at 350°C. Thin foils were jet polished in a nitric acid-methanol solution and lightly ion-beam milled prior to insertion into a JE0L 200 CX microscope. A through focus series of [110] axial lattice images was taken at 200,keV, using a pointed LaB6 filament and an objective aperture of radius 0.64Å-1.

Fig. 1(a) shows twoend-on γ' plates about 200Å thick and lying on {111} planes as evident from the diffraction pattern in Fig. 1(b).
Segregation and domain structure in rapidly solidified Ni3Al
Authors: Horton J. A. , Koch C. C. , Liu C. T.
Published: June 2020

Rapid solidification processing (RSP) in conjunction with microalloying is being used to enhance the ductility of Ni3Al. Boron which strengthens grain boundaries was added for significant improvement in ductility of Ni3Al. Specimens of Ni3Al (24 at. % Al) with additions of 0, 500, and 1000 wt ppm boron were splat-cooled in an arc-hammer apparatus. The specimens without boron were brittle while specimens with boron were ductile for all but the fastest quench rates. Microstructural characterization was performed with a Philips EM400T/FEG and JEM 120CX transmission electron microscopes.

Antiphase boundaries (APB) are not observed in Ni3A1 alloys fabricated from cast ingots, but are present following RSP. The average domain sizes were 50 and 80 nm for specimens with and without boron, respectively, but were independent of solidification rate. Near the surface of the splats the domain size was approximately the same as in the center even though the grain size was much smaller. Regions of small domains which were always in the center of the grains were surrounded by larger domains.
Calculations of Z-Contrast for organic and biological specimens
Authors: Egerton R.F. , Misra M.
Published: June 2020

So-called "atomic-number contrast" is obtained in STEM by displaying a ratio signal formed by dividing the annular-dark-field signal Iadby the inelastic component Iiof the bright-field intensity (isolated by means of an electron spectrometer; see Fig. 1). Originally used for single-atom imaging, the technique has more recently been applied to polymer samples and biological tissue.

We report here estimates of the ratio signal from organic specimens, based on the following assumptions:

(1) That the specimen is amorphous and that phase contrast may be neglected for the electron-optical conditions and specimen features being considered; (2) That atomic cross sections may be used to estimate the amount of elastic and inelastic scattering. Modern calculations differ from simple Lenz theory in predicting that the cross section is not a smoothly-increasing function of atomic number (see Fig. 2), particularly for the 1ighter elements. (3) We assume a slightly idealized detection system in which all elastically scattered electrons contribute to Iad, while all electrons which have been inelastically (but not elastically) scattered contribute to Ii.
Pattern recognition techniques applied to microdiffraction patterns
Authors: Cowley J.M. , Monosmith W.B. , Disko M.M.
Published: June 2020

Electron microdiffraction from regions less than 20Å, and as small as 3Å, in diameter are now readily obtained with a dedicated STEM instrument, especially if an efficient two dimensional detector system is employed. Such patterns may be valuable for detailed studies of small particles, individual crystal defects and small ordered regions within microcrystalline or amorphous materials. A difficulty which often arises in the use of microdiffraction patterns is that of determining to what extent a pattern or collection of patterns is representative of the material under study. For example, for a thin amorphous film, the recording of one pattern showing a well-developed regular array of spots is not significant since the randomness of the structure ensures that any such a pattern will occur with some finite probability. To characterize the nature and extent of the local atomic ordering, statistical analysis of a very large number of patterns would be required.
Instrumentation for detecting channelling radiation in the high-voltage electron microscope
Authors: Butler J. H. , Humphreys C. J.
Published: June 2020

Electromagnetic radiation is emitted when fast (relativistic) electrons pass through crystal targets which are oriented in a preferential (channelling) direction with respect to the incident beam. In the classical sense, the electrons perform sinusoidal oscillations as they propagate through the crystal (as illustrated in Fig. 1 for the case of planar channelling). When viewed in the electron rest frame, this motion, a result of successive Bragg reflections, gives rise to familiar dipole emission. In the laboratory frame, the radiation is seen to be of a higher energy (because of the Doppler shift) and is also compressed into a narrower cone of emission (due to the relativistic “searchlight” effect). The energy and yield of this monochromatic light is a continuously increasing function of the incident beam energy and, for beam energies of 1 MeV and higher, it occurs in the x-ray and γ-ray regions of the spectrum. Consequently, much interest has been expressed in regard to the use of this phenomenon as the basis for fabricating a coherent, tunable radiation source.
Pd/ MgO reaction study
Authors: Warble C.E. , Cowley J.M.
Published: June 2020

It has been known for some years that, under appropriate conditions, palladium will interact with magnesium oxide at temperatures well below the melting point of the metal. Several studies based upon bright field transmission electron microscopy (BFTEM) have already been carried out. This work established the following main points about the reaction.

The phenomenon observed is a reaction.

The reacting phase exhibits characteristics typical of liquid substances.

The reaction proceeds by means of an amorphous phase at a temperature lower than the melting point of either material.

The ceramic remains virtually strain-free during the reaction as well as after normal or quench-rate cooling.

The reaction phase maintains an amorphous structure when cooled slowly or quenched.

X-ray microprobe analysis on the reaction zone indicated that at least 95% of the cations were palladium.

This paper discusses recent findings from further studies made using the VG-HB5 scanning transmission electron microscope (STEM), and the JEOL 200CX (BFTEM).
Quantitative assessment of radiation damage in protein crystal
Authors: Chiu Wah , Jeng T.W.
Published: June 2020

Radiation damage is a well known phenomenon in the electron microscopic study of thin crystals of macromolecules. A quantitative description of radiation damage is essential for at least 3 reasons: (i) it can provide numerical parameters for evaluating the extent of specimen damage at various experimental conditions, (ii) it can provide an indicator as to the maximum number of diffraction patterns and images obtainable from a single crystal before the specimen is significantly altered, and (iii) since the specimen is being altered after the initial hit by the electrons, schemes are needed to make correction of the data prior to its use for structural calculation. This paper primarily deals with the methodology used to evaluate the quantitative aspects of radiation damage of thin protein crystals. The example of crystal used in this study was crotoxin complex embedded in glucose.

A standard set of data recorded in a radiation damage study is a series of electron diffraction patterns from a single crystal. The important experimental variables include the exposure rate, the exposure time and the accumulating exposure between successive patterns.
Assessment of radiation damage using a crystallographic technique
Authors: Misra Manoj , Egerton R.F.
Published: June 2020

Fading of electron-diffraction patterns has provided a convenient method of assessing radiation damage in crystalline biological and organic compounds. The intensity of a diffraction spot is proportional to the square of structure amplitude, and by assigning the correct phases to these amplitudes, one can reconstruct the projected crystal potential. Changes in the reconstructed potentials obtained from successive diffraction patterns (recorded at increasing dose) may then yield information about the redistribution of atoms within the unit cell occurring during electron irradiation. In the absence of phase information (e.g. for compounds of unknown crystal structure), such a Fourier synthesis technique can obviously not be applied. However, a Fourier series can be computed using the intensities of diffraction spots as Fourier coefficients. The function so generated is called the Patterson function, and provides information about the disposition of interatomic vectors within the unit cell. We report here a study of electron irradiation damage in 5-iodouracil based on the Patterson-synthesis method.
The limits of microanalytical information as set by electron-beam damage
Authors: Isaacson M. S.
Published: June 2020

The task given to me was try to address how radiation damage limits the information that we can extract from a sample in the electron microscope and to somehow i11ucidate what is known about the mechanism of the damage itself. I am afraid that the tasks are more formidable than I first realized, and I shall not (in this paper) be able to come to definitive conclusions. However, the attempt will be made to tie together various observations and bits of knowledge from different areas which may not be familiar to the general practitioner of electron microscopy.

The area of radiation damage in electron microscopy tends to be somewhat descriptive. After all, it is really not the main item on the microscopist's agenda, but rather happens to be the unfortunate consequence of the act of viewing the sample. One can liken the electron microscopist to someone who is ill. It is not too important why or how the illness occurred, but rather, how to remedy it.
Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM
Authors: McConville Richard L.
Published: June 2020

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.

These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.
STEM microanalysis of tin segregation in germanium
Authors: Grovenor C.R.M. , Batson P.E. , Smith D.A.
Published: June 2020

STEM investigations using very fine incident electron beam diameters and x-ray analysis facilities provide a powerful tool for determining the segregation levels of solute elements at, or near,grain boundaries. As yet however relatively few studies have made use of this potential. It is particularily interesting to apply the technique to the study of Sn segregation to germanium grain boundaries, because the boundaries can be driven to migrate by being heated in the presence of the Sn. It is proposed that this grain boundary migration is caused by a process called Diffusion Induced Boundary Migration, (DIGM). The suggested mechanism for DIGM is that a grain boundary Kirkendall effect occurs due to the uneven fluxes of solute and solvent atoms down the interface. The resulting net vacancy flux stimulates the movement of grain boundary dislocations, which in turn cause boundary migration. A significant feature of this model is that solute enriched grains will be left behind each migrating boundary.
On-line feature analysis of electron-microscope images
Authors: Krakow William
Published: June 2020

For the last several years size and shape analysis has been performed via small minicomputers which have been attached to television rate video digitizers. These systems often have very limited on-line image processing capabilities and most of the tasks of such systems are associated with bit type images on the computer. Often the analysis software is written in an assembler language for analysis speed which does not make it transferable to other types of computers and it is not readily modified for new applications. To avoid some of the above difficulties, a computer program has been written totally in fortran to run via a large mainframe computer. This program provides size and shape features from electron microscope images in real time via a television digital frame store. For analysis it uses line segment encoding techniques and can analyze hundreds of particles in a few seconds of CPU. Even larger numbers of objects each with any convoluted shape can be analyzed in under one minute of CPU on the mainframe.
Structure of the insect flight muscle Z disk
Authors: J.F. Deatherage , B. Luke , G.M. Sainsbury , B. Bullard
Published: June 2020

The Z disk of striated muscle is a regular planar network of connections linking two sets of oppositely directed thin filaments from adjacent sarcomeres. Ashurst has inspected images of oblique thin sections through insect Z disks, and proposed that parallel overlapping filaments in the Z disk are arranged in hexagonal bundles of six, which alternating filaments enter from opposite sarcomeres. We have now analyzed images of thin-sectioned and negatively-stained Z disks using Fourier filtering and crystallographic image processing methods. Our findings confirm the basic model of Ashurst for the arrangement of filaments inside the Z disk. By evaluating contour maps of crystallographically averaged images at higher resolution, we have obtained additional information about the positions of the filaments and the connections linking them.

We have examined Z disks of flight muscles of three orders of insect, Diptera (blowfly), Hemiptera (Lethocerus) and Hymenoptera (bumble and carpenter bee). Thin sections from Lethocerus whole muscle fibers and negatively-stained isolated Z disks from bumble bee were examined in most detail. The connectivities of thin filaments of one sarcomere through the Z disk to the adjacent sarcomere were traced on Fourier-filtered images of oblique thin-sections. These cut the myofibril at an angle off perpendicular, intersecting it on one side of the Z disk, passing through it, and exiting on the other side. The filaments in the Z disk lattice, and the connections between them, were examined on crystallographically averaged images of transverse sections through the Z disk, and of isolated, negatively-stained Z disks.

The insect flight muscle Z disk is arranged on a hexagonal lattice with unit cell dimensions of about 465Å. Images of both thin- sectioned and negatively-stained Z disks diffract optically to the fifth or sixth order (about 75Å resolution). The projection symmetry of the Z disk is p3m. Contour maps of crystallographically averaged images of thin- sectioned and isolated Z disks show prominent features arranged in roughly hexagonal bundles of six. These features correspond to extensions of the thin filaments into the Z disk, three from each of the opposing sarcomeres. By analysis of oblique sections we have confirmed that the opposed thin filament lattices of the two sarcomeres meet in three-fold to six-fold register (that is, a third of a unit cell out of register along both crystallographic axes). The relative strengths of features in these images are consistent with long overlap of filaments from opposite sarcomeres inside the Z disk.
Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water
Authors: Leino Richard L. , Anderson Jon G. , McCormick J. Howard
Published: June 2020

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.

Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.
A scanning electron microscopic study of the alimentary canal in the grass lizard
Authors: Ooi E. C. V. , Chan C. W.
Published: June 2020

The histology of the reptilian alimentary tract has been described in numerous light microscopic studies. However, no information on surface morphology is available for any species of reptiles. In the present communication, the alimentary canal of the grass lizard, Takydromus sexlineatus, is investigated by means of light and scanning electron microscopy.

Various portions of the alimentary canal were dissected and removed rapidly. While immersed in cacodylate buffer, the inner lining of each portion was exposed and rinsed. The tissues were then fixed in 2% glutaraldehyde in cacodylate buffer, dehydrated in graded ethanol series, and critical point dried with carbon dioxide. After coating with gold, the specimens were examined on a JOEL JSM-35 operated at 35 KV. Tissues for light microscopy were processed routinely.
Ultrastructure of Russell's bodies in plasma cells of normal ovine hemal lymph nodes
Authors: Al-Bagdadi F. , Seger C.
Published: June 2020

Hemal lymph nodes occur in a wide range of animals including ruminants, primates, horses and man. It is generally believed that they are separate lymphatic organs capable of performing hemopoietic and immunologic functions. The plasma cells are the main source of antibody synthesis. They are formed when antigens enter B-lymphocytes and induce their transformation into plasma cells. The plasma cells release immunoglobulins (Russell's bodies) directly into adjacent tissues.Different reports expressed varied opinions on the significance and the fate of Russell bodies in plasma cells. Some of the opinions are that Russell bodies appear in pathological conditions. it is believed that the appearance of Russell's bodies in plasma cells is a cellular defect. They are also considered heterogenous in nature. This report shows that Russell bodies have appeared in plasma cell of healthy ovine hemal lymph nodes.

Hemal lymph nodes were collected from different regions near the viscera of five native Louisiana sheep. Small slices of the nodes were fixed in 3% gluteraldehyde in phosphate buffer (pH 7.4), postfixed in 1% OSO4 and embedded in epon. Ultra-thin sections were examined with a Zeiss 10 electron microscope.
The blood/air barrier as defined by horseradish peroxidase in the normal guinea pig lung
Authors: Ford J.O. , Dodson R.F. , Williams M.G. , Hurst G.A.
Published: June 2020

The blood/air barrier is established by the combined influences of the capillary endothelial cells, the interstitial space and the alveolar epithelial cells. The present study examined the morphological basis of the blood/air barrier as defined by a tracer model. This barrier is altered in many pathological states as reflected by the presence of exudate and/or increased cellularity in the alveoli. This investigation provides comparative data which can be used to assess early changes and potential recovery of barrier integrity whether response is caused by internal physiological alterations or external toxic stimuli.

A small molecular weight protein, horseradish peroxidase (HRP), was used in the guinea pig model to ultrastructurally show the existence of a barrier at the level of the alveolar epithelium. Adult animals were injected intravenously with 300 mg/kg of the tracer in a small volume of saline (4% of total blood volume) and sacrificed at varying intervals by either intratracheal filling or right-ventricular perfusion with a fixative consisting of 3% glutaraldehyde buffered with 0.1M phosphate.
Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica
Authors: Cocks George G. , Leibovitz Louis , Lee DoSuk D.
Published: June 2020

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.

The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.
Fine structure of the tail in the spermatozoa of the Mexican axolotl Ambystoma mexicanum
Authors: Keyhani Ezzatollah
Published: June 2020

The structure of the spermatozoa represents an extreme degree of diversity among the various species of metazoa. This diversity is most probably a reflection of the adaptation to the variable conditions for fertilization. The Axolotl sperm consists of head and tail. The tail is the subject of the present communication. It consists of neck region, intermediary and principal pieces. I. The neck (∼10μm) is inserted in the nucleus and can be designated as a region between immediately above the mitochondria (a construction zone between nucleus and sustained filament) and the upper region of the anterior centriole. In longitudinal section (Fig.l) it consists of a pair of centrioles and a mass of granular fibrillar substance. The anterior centriole (0.26 x 0.5μm) appears free, while the posterior one is continuous with the flagellum. The appearance of two central filaments indicates the transition between posterior centriole and flagellum. In front of the centrioles,there is a mass of granulo-fibrillar substance (Fig.l) which in vertical section (Fig.4) appear to be semi-circular and relatively thick (0.3μm). The granulo-fibriliar substance protrude outward (Fig.l,3,4) and thus the term protuberance seems appropriate. II.