bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ TEM sample preparation for surface-sensitive plane view imaging
Authors: Ai R. , Dunn D.N. , Savage T.S. , Zhang J.P. , Marks L.D.
Published: June 2020

The recent development of ultra high vacuum high resolution electron microscopes has made it possible to use an electron microscope to study surface structures with atomic resolution. Although surface images of Au(110) 2x11 and Si(111) 7x72 reconstructions have been obtained, no standard TEM sample preparation technique for surface imaging has been developed for routine uses. In conventional surface science, the common method of producing an UHV clean sample is a combination of ion sputtering and annealing; can this process be used to produce TEM samples for surface imaging. Our studies show that clean, well order TEM samples can be achieved by this approach.
Computer analysis of side-band holography in STEM
Authors: Gribelyuk M.A. , Cowley J.M.
Published: June 2020

Recently the use of a biprism in a STEM instrument has been suggested for recording of a hologram. A biprism is inserted in the illumination system and creates two coherent focussed beams at the specimen level with a probe size d= 5-10Å. If one beam passes through an object and another one passes in vacuum, an interference pattern, i.e. a hologram can be observed in diffraction plane (Fig.1).
Calculated image contrast of vacancies in silicon crystal and representation of their contrast anomalies
Authors: Awaji M. , Hashimoto H. , Kinoshita T.
Published: June 2020

Images of small lattice defects have been observed as a contrast anomaly recently by HREM. However, the observed images are generally mixed with the contrast anomalies which come from the quantum noise, contamination etc. Therefore, it seems to be useful to know the calculated image and to compare with the observed ones. In this paper, calculated image contrast of Si containing vacancies is studied.

The stress field due to a stacking fault tetrahedron (SFT) proposed by Yoffe has been extrapolated to that of a vacancy. Since the atomic structure around the vacancies is not yet clearly known, it is assumed that a pair of vacancies in Si behaves like single vacancy in f.c.c. crystals. Figure 1 shows a pair of vacancies position (®-®) in a large unit cell with 0.38nm thickness of Si crystal projected to [110]. It is necessary for this calculation to have the large unit cell because the stress field effects on the atom positions at an infinite distance.
High-angle annular dark-field STEM imaging of doped semiconductor layers
Authors: Perovic D.D. , Paterson J.H.
Published: June 2020

With the development of crystal growth techniques such as molecular beam epitaxy (MBE), it is now possible to fabricate modulation-doped superlattices consisting of alternating ultrathin layers of n-and/or p-type material abruptly separated by undoped material. At sufficiently high dopant concentrations these abrupt layers may be imaged in cross section by electron microscopy. Pennycook et al. and Treacy et al. have used high angle annular dark-field (HAAD) imaging in the scanning transmission electron microscope (STEM) to image low levels of dopants (∼1 at. %) in semiconductors. This work is concerned with imaging boron and arsenic doped layers in silicon at levels « 1 at.%.

Fig. 1 shows a HAAD image of a B-Si superlattice at the <110> zone-axis orientation taken at 100 kV using a VG HB501UX STEM. The bright vertical layers are the B-doped regions, containing ∼4 x 1020 B/cm3. The horizontal lines are due to beam instability while the image was recorded. Fig.2 shows a line scan across the same superlattice, recorded by scanning the beam across the specimen in a direction perpendicular to the layers.
An example of spectrum imaging used for comparison of EELS quantitative analysis techniques on Al-Li
Authors: Hunt John A.
Published: June 2020

Spectrum-imaging is a useful technique for comparing different processing methods on very large data sets which are identical for each method. This paper is concerned with comparing methods of electron energy-loss spectroscopy (EELS) quantitative analysis on the Al-Li system. The spectrum-image analyzed here was obtained from an Al-10at%Li foil aged to produce δ' precipitates that can span the foil thickness. Two 1024 channel EELS spectra offset in energy by 1 eV were recorded and stored at each pixel in the 80x80 spectrum-image (25 Mbytes). An energy range of 39-89eV (20 channels/eV) are represented. During processing the spectra are either subtracted to create an artifact corrected difference spectrum, or the energy offset is numerically removed and the spectra are added to create a normal spectrum. The spectrum-images are processed into 2D floating-point images using methods and software described in [1].
An AEM characterization of interfacial reactions in Al-MMC's reinforced with as-received and oxidized SiC particles
Authors: Legoux J.G. , L'Espérance G. , Suéry M.
Published: June 2020

Interfacial reactions in MMC's can affect the mechanical properties of the material by changing the composition of the matrix and by forming new compounds at the matrix/ceramic interfaces. These reactions depend on the surface chemistry of the reinforcement, such as the presence of SiO2 produced by air oxidation of raw SiC particles. These reactions also depend on the processing route, particularly the thermal history of the material (fabrication or subsequent heat treatment or remelting). This paper presents results of an analytical transmission electron microscopy investigation of interfaces observed in Al-1% Mg alloys reinforced with 10 vol. % SiC particles. The composites were produced by the compocasting technique (semi-solid route) using as-received and oxidized SiC particles. The particles were oxidized in air at 1100°C for various times to produce oxidation levels ranging from 0-16 wt % measured by wet analysis.
Massive icing of a high-purity Ge EDS detector with an ultrathin window
Authors: Foitzik A.H. , Sears J.S. , Heuer A.H. , Zaluzec N.J.
Published: June 2020

High Purity Germanium (HPGe) EDS detectors are now commercially available. Their main advantage over the commonly used Si(Li) EDS detectors is the increased absorption at higher energies due to the higher mass density of germanium. As a result, in modern medium voltage TEMs the K-shells of even heavy elements can be utilized for analytical electron microscopy. In addition, in order to increase the detector performance in the low energy range, an ultrathin window is used instead of a beryllium window. While detectors with a beryllium window are baked, evacuated and then sealed during the manufacturing process (the detecting crystal, therefore, being in a closed environment), our detector with an ultrathin window is not sealed and when in use, is constantly pumped by the microscope vacuum system. While not in use, the detector is retracted behind a valve, at which time it is not pumped.
Silicon vibration amplitude determined by energy-filtered CBED
Authors: Xu Peirong , Loane Russell , Silcox John
Published: June 2020

The frozen phonon method was recently developed to include the effects of thermal vibrations in the multislice calculation. In this method, each atom in the simulated specimen is displaced by a random amount which follows a Gaussian distribution with a standard deviation equal to the atomic vibration amplitude. Convergent beam electron diffraction (CBED) patterns calculated by this technique contain Kikuchi bands and a thermal diffuse background which were matched quantitatively to experimental Si (100) CBED patterns for scattering angles up to the first order Laue Zone. In this paper, we report the measurement of the room temperature silicon vibration amplitude from comparison of energy filtered CBED with frozen phonon calculations.

The energy filtered Si (100) patterns were obtained with a VG HB501A STEM in microdiffraction mode by fixing a convergent probe (7.5mrad half angle, probe size ≈ 40Å) on the specimen and scanning the post specimen electrons over a small axial collector aperture (1.6mrad).
TEM characterization of metallization systems in VLSI
Authors: Mitwalsky A. , Oppolzer H.
Published: June 2020

Detailed knowledge of the properties of metallization systems used in silicon VLSI technolgy is essential to evaluate application and to achieve stable device operation. The progressively shrinking device dimensions require analytical techniques allowing to detect interfacial reactions or precipitation with nanometer resolution, particularly for the development of new processes. Transmission electron microscopy (TEM) of thin cross sections represents a powerful tool for obtaining such information directly. In addition to imaging analytical TEM allows phase and element identification with high spatial resolution.

The interaction during processing between silicides of various metals (Ti, Co, Ta and W) and different dopants (B, As) in silicon was investigated since possible metal dopant reactions may lead to dopant depletion in the silicon. In the case of Ti and Ta silicide the formation of metal dopant compounds during heat treatment was indeed observed by scanning electron microscopy and TEM.
The effects of deposition and annealing condition on the microstractural evolution of Al-Cu and Al-Cu-Si thin films
Authors: Park M. , Krause S. J. , Wilson S. R.
Published: June 2020

Aluminum alloys (Al-Cu and Al-Cu-Si) are the most extensively used metals for interconnects in integrated circuits. Cu additions enhance electro-thermal migration resistance, but may increase corrosion susceptibility in both reactive ion etching and wet processing due to the formation of Al2Cu (θ) precipitates. Si was originally added to minimize erosion in contact windows, however it was recently found that the addition of 1.5% or 0.5% Si in Al-Cu alloy improves its corrosion resistance. θ precipitates in binary alloys have been found to occur at the Al/sublayer interface during high temperature (>200°C) deposition due to the fast surface diffusion of Cu. For the higher temperature deposition in the Al solid solution region, platelike θ precipitates were also formed at the interface and grain boundaries during a fast cooldown of wafers. However, it has not been well understood how the addition of Si in Al-Cu alters the thin film microstructure and increases the corrosion resistance. In this work, the effects of Si addition and deposition temperature on the film microstructure were studied for different alloy compositions and sublayers. The effects of thermal annealing on the interaction of Al films with Ti-W sublayer were also studied.
Chemical mapping of materials at the atomic level
Authors: Ourmazd A. , Baumann F. , Bode M. , Kim Y. , Rouviere J.L.
Published: June 2020

Under appropriate conditions, a conventional lattice image is a map of the sample structure, because the dominant reflections used to form lattice images are relatively insensitive to compositional changes in the sample. However, certain reflections, such as the (200) in the zinc-blende structure, owe their existence to chemical differences between the various atomic species present on the lattice sites. Such chemical reflections arc sensitive to compositional changes in the sample. For fundamental reasons such reflections are often weak; they come about because of incomplete cancellation of out of phase contributions from different sublattices. “Chemical lattice imaging” exploits dynamical scattering to maximize the intensity of such reflections, and uses the objective lens as a bandpass filter to enhance their contribution to the image.
Defects in MBE-grown In AsXSb1-X strained layer superlattices
Authors: Chadda S. , Datye A. K. , Dawson L. R.
Published: June 2020

III-V alloy devices are being considered for applications as infrared detectors, by several research groups due to processing advantages over II-VI alloy devices. InAs0.4Sb0.6 has the lowest band gap at 77 K among all III-V compounds, which corresponds to a cut off wavelength of 9 μm. The use of strained layer superlattices (SLS) was first proposed by Osbourn for lowering the band gap and achieving absorption at wavelengths greater than 12 μm at 77 K. A schematic diagram of the device is shown in figure 1. It was grown by Molecular Beam Epitaxy (MBE) at 425 °C and it consists of a p-n junction embedded in a InAs0.15Sb0.85/InSb SLS with layers of equal (110 Å) thickness. The n and p type dopants were S (PbS) and Be respectively. The active device SLS was grown on a composition graded strain relief buffer on the (100) face of an InSb substrate. The samples were sliced, thinned, polished, dimpled and ion milled for making cross-section Transmission Electron Microscope (TEM) samples.
Characterization of homoepitaxial diamond films by Electron microscopy
Authors: Malta D.P. , Willard S.A. , Rudder R.A. , Hudson G.C. , Posthill J.B. , Thomas R.E. , Markunas R.J.
Published: June 2020

Semiconducting diamond films have the potential for use as a material in which to build active electronic devices capable of operating at high temperatures or in high radiation environments. A major goal of current device-related diamond research is to achieve a high quality epitaxial film on an inexpensive, readily available, non-native substrate. One step in the process of achieving this goal is understanding the nucleation and growth processes of diamond films on diamond substrates. Electron microscopy has already proven invaluable for assessing polycrystalline diamond films grown on nonnative surfaces.

The quality of the grown diamond film depends on several factors, one of which is the quality of the diamond substrate. Substrates commercially available today have often been found to have scratched surfaces resulting from the polishing process (Fig. 1a). Electron beam-induced current (EBIC) imaging shows that electrically active sub-surface defects can be present to a large degree (Fig. 1c). Growth of homoepitaxial diamond films by rf plasma-enhanced chemical vapor deposition (PECVD) has been found to planarize the scratched substrate surface (Fig. 1b).
TEM characterization of SiGe heterolayers grown on SIMOX
Authors: David Theodore N. , Fejes Peter , Tomozane Mamoru , Liaw Ming
Published: June 2020

SiGe heterolayers are of interest for use in heterojunction transistors, infrared detectors and field-effect transistors. SIMOX (Separation of silicon by IMplanted OXygen) is useful for fabrication of silicon-on-insulator (SOI) structures (electrically isolated from the substrate). SIMOX could potentially be used for isolation of SiGe structures from the substrate. Epitaxial-Si grown on SIMOX (required for some device structures) can have grown-in dislocations that arise due to STMOX-related damage. If SiGe heterolayers were grown on silicon, dislocations could interact with the strain fields associated with the SiGe layers. Such interaction could possibly lead to a reduction in defect densities in upper layers of the structures. In the present study, SiGe heterolayers grown on SIMOX by chemical vapor deposition were characterized using TEM. The structures consisted of epi-silicon grown on a Si/Sii-xGex superlattice which was in turn grown on a Si/SiO2 (SIMOX) structure. The behavior of defects in the structures was of interest.
Amorphization in Intermetallic Compounds FeTi and CoTi Under 1-MeV Electron Irradiation
Authors: Xu Genbao , Meshii M. , Okamoto P. R.
Published: June 2020

Electron irradiation induced amorphization of FeTi and CoTi was studied by high voltage electron microscopy (HVEM) from 10 to 160°K. The complete amorphization was observed in both compounds, with the critical dose at 10°K and the critical temperature being about 1.7 dpa and 110°K for FeTi, and about 1.3 dpa and 90°K for CoTi. The onset of amorphization occurred in both compounds after substantial chemical disordering when irradiated below Tc, while the point defect clusters formed above Tc. In addition, the pseudo ten fold symmetry (PTEFS) diffraction spots were observed in selected area diffraction (SAD) pattern of both compounds prior to complete chemical disordering and thus complete amorphization.
The Microstructure of Ceramic Whiskers
Authors: Allard L. F. , Nolan T. A.
Published: June 2020

The internal structure and surface crystallography of ceramic whiskers are of interest because of their increasing importance as second phase reinforcements in a variety of matrix materials. Whiskers are typically 0.5 to 5 um in diameter with aspect ratios of 10 to 100 or more. Silicon carbide whiskers are the best known; they are usually grown by vapor-liquid-solid (VLS) or other processes from either natural (e.g. rice hulls) or synthetic materials. Titanium nitride whiskers are also of interest because of their potential for applications where SiC whiskers are not suitable (e.g. ferrous alloys). This paper highlights some of the details of SiC and TiN whisker ultrastructure.
Crystallization Behavior of Chemically Synthesized LiNbO3
Authors: Joshi Vikram
Published: June 2020

Lithium niobate is a material of interest for electro-optic and nonlinear optical applications. Conventional processing of lithium niobate involves the relatively coarse scale of mixing of lithium carbonate and niobium oxide powders, which makes it difficult to obtain a chemically homogeneous, single phase product. In recent years, sol-gel processing of lithium niobate has been investigated as a method of producing high purity, homogeneous material of stoichiometric composition. This processing technique permits easy and precise control over composition, intimate mixing of the constituent elements, and the use of relatively low processing temperatures. This present study investigates the crystallization behavior of gels formed by the hydrolysis of mixed alkoxides of lithium and niobium in low molecular weight alcohols. Crystallization was found to be initiated at temperatures as low as 200°C and could be completed by 450°C.
A Microscope-Compatible Auger Electron Spectrometer
Authors: Ai R.
Published: June 2020

With the recent development of ultra-high vacuum high resolution electron microscopes (UHV-HREM), electron microscopes have become valuable tools for surface studies. Techniques such as surface profile image, surface sensitive plane view, and reflection electron microscopy have been developed to take full advantage of the atomic resolution of HREM to study surface structures. However a complete surface study requires information on both the surface structure and surface chemistry. Therefore in order to turn an electron microscope into a real surface analytical tool, the challenge is to develop a microscopecompatible, surface sensitive tool for in-situ surface chemical analysis.
Fresnel fringe contrast in the TEM: Application to study the microstructure of amorphous silicon
Authors: Kannan V. C.
Published: June 2020

Amorphous silicon-hydrogen (α - Si:H) alloy films deposited by plasma enhanced chemical vapor deposition (PECVD) of silane exhibit a remarkable property; namely, the films are practically insulators in the as deposited state. When sandwiched between two metals or highly conductive refractory metal silicides, the films can be converted to near conductivity state by “programming” the sandwich structure to complete dielectric breakdown of the insulator. Such α - Si:H films are used in permanently programmable integrated circuits such as PGA (Programmable Gate Arrays) as “antifuse” materials.

TEM technique has, usually, limited application to study the microstructure of amorphous materials since they do not exhibit the well understood diffraction contrast as seen in crystalline materials. However, Fresnel fringe contrast due to electron interference effects at either sides of interfaces or at the edges can be used to provide the sort of information needed to characterize amorphous films. The profiles of Fresnel fringes are often complex for interface thickness of <100 A and their shape and contrast are very sensitive to compositional changes on either sides of the interfaces.
Analysis of pure tilt grain boundary in silicon by Fresnel fringe technique
Authors: Das Chowdhury K. , Kim M. J. , Chen Y. L. , Carpenter R. W.
Published: June 2020

One of the main emphases of research on interfaces is to characterize them both structurally and chemically. The atomic structure of interfaces and the existence of thin interfacial glassy phases are being investigated mainly by HREM imaging methods. In addition, a few other methods including dark field diffuse imaging and Fresnel Fringe techniques have been developed to identify the interfacial films and quantify their width. Fresnel fringe profiles from the interface images have been used to deduce the mean inner potential of thin interfacial films. In our research the Fresnel fringe contrast behavior of a tilt grain boundary in silicon whose structure and chemistry were previously characterized by HREM and high spatial resolution AEM was analyzed by comparing the experimental Fresnel fringe profiles with computer simulations of these images.
HREM and EDX studies of layered bimetallic colloids
Authors: Bovin Jan-Olov , Malm Jan-Olle
Published: June 2020

Bimetallic clusters and colloids are interesting for several reasons. They may serve as objects for studies of the formation of different alloys, furthermore novel catalytic activities are to be expected. It is also possible to save precious metal, like Pt, by optimizing the synthetical conditions so that only very thin surface layers occur. This paper describes the identification of the shell structure of such particles by high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray (EDX) microanalysis.

Gold colloids with a diameter of 18 nm can be covered with platinum or palladium shells, in aqueous solution. The new layered colloid shows a metallic luster. The HRTEM studies were performed in a JEM-4000EX with a structural resolution of 0.16 nm and the EDX analysis was done in a JEM-2000FX equipped with a LINK 10000 system.
Improved stability of alkali metals on catalysts during analytical electron microscopy
Authors: Reuter Kathleen B. , Lyman Charles E.
Published: June 2020

Determination of the location and quantity of poison or promoter elements on catalyst surfaces is an ideal application for the high spatial resolution available on the analytical electron microscope (AEM). However, these elements are often unstable under an electron beam making them difficult to detect consistently. This paper describes a method to enhance the stability of cesium, a mobile alkali metal, on the surface of a catalyst using a thin coating of chromium.

The catalyst in this study was MoS2 doped with 5.3 wt% CsOOCH (4.8 mol% Cs) which is used for alcohol synthesis. After grinding with a mortar and pestle and spreading between glass slides, the Cs/MoS2 was supported on a carbon coated Cu grid. The Cs/MoS2 particles were coated with 10nm of Cr using a VCR Group, Inc. ion beam sputterer model IBS/TM200. During sputtering, the vacuum produced by a turbo pump and LN2 cold trap was better than 10-5 torr and the sample was continuously rotated and tilted.
High-resolution imaging of ordered structure in thin polyimide films
Authors: Chuang S. -F. , Kuan T. S. , Pomerantz M.
Published: June 2020

Polyimides are excellent insulating materials for use in microelectronics because of their high thermal stability, low dielectric constant, good mechanical strength, and resistance to moisture. The molecule main chain of polyimides consists of a rigid, planar structure of aromatic and/or heterocyclic rings. These polymers are usually highly disordered, but local crystallization is feasible between these regular and strongly interacting planar ring groups. In principle, it is possible to synthesize polyimides in crystalline form, with the exception of crosslinked materials, or those with long and bulky side groups. Spin-on technique is most often used to apply polyimide films onto substrates in semiconductor industry. This technique, however, is not suitable for preparation of smooth films with thickness less than a few hundred angstrons. Recently, monolayer-by-monolayer depositions of polyamic acids (precursors to polyimides) onto substrates using the Langmuir-Blodgett technique have been reported. This technique offers more precise control of film thickness and may allow highly ordered polymer films to be synthesized.
Electron microscopy on biaxially oriented PET films
Authors: Gohil Ramesh M.
Published: June 2020

In order to understand properties of biaxially oriented PET films, it is necessary to understand the genuine morphology of the films. Inspite of previous extensive studies, our knowledge of the exact nature of PET crystals, their reorganization during heat treatment, and their relevance to the properties is not clearly understood. Therefore, the present study was undertaken to investigate characteristics of PET crystals using modified transmission electron microscopic (TEM) techniques which are providing interesting and valuable insight into the structure of PET film and its changes.

Films were prepared by simultaneous biaxial stretching (SBS) of amorphous cast films at 95°C with the rate of 9000 %/min. and draw ratio of 3.5 X. The films were heat-set in die temperature range of 100-240°C. The studies were carried out using three TEM techniques by observation of (a) surface structure by a modified two stage replication method, (b) bulk structure in the film plane by a typical microtomy method, and (c) bulk structure by etching with a mixture of 60% propylamine and 40% water.
Observations on the growth of YBa2Cu3O7-δ thin films on MgO by pulsed-laser ablation
Authors: Grant Norton M. , Barry Carter C.
Published: June 2020

Pulsed-laser ablation has been widely used to produce high-quality thin films of YBa2Cu3O7-δ on a range of substrate materials. The nonequilibrium nature of the process allows congruent deposition of oxides with complex stoichiometrics. In the high power density regime produced by the UV excimer lasers the ablated species includes a mixture of neutral atoms, molecules and ions. All these species play an important role in thin-film deposition. However, changes in the deposition parameters have been shown to affect the microstructure of thin YBa2Cu3O7-δ films. The formation of metastable configurations is possible because at the low substrate temperatures used, only shortrange rearrangement on the substrate surface can occur. The parameters associated directly with the laser ablation process, those determining the nature of the process, e g. thermal or nonthermal volatilization, have been classified as ‘primary parameters'. Other parameters may also affect the microstructure of the thin film. In this paper, the effects of these ‘secondary parameters' on the microstructure of YBa2Cu3O7-δ films will be discussed. Examples of 'secondary parameters' include the substrate temperature and the oxygen partial pressure during deposition.
Kikuchi map of YBa2Cu3O7-δ crystal and its application
Authors: Zhu Yimei , Suenaga Masaki
Published: June 2020

Relative crystallographic orientation of adjacent grains has been shown to affect the transport current in YBa2Cu3O7-δ polycrystalline superconductors. In order to determine a large number of crystallographic orientations of YBa2Cu3O7-δ quickly and precisely, the complete Kikuchi map which consists of six standard triangles covering all stereographic projections of this crystal, was computer generated. However, for relatively small value of N [N=h2+k2+(l/c/a)2] in this complex crystal, a geometrically calculated Kikuchi pattern [Fig.1(a)] usually can not be matched with the observed pattern [Fig.1(c)] . To obtain a good match, Kikuchi lines up to sufficient high indices must be generated and weak and kinematically forbidden Kikuchi lines must be eliminated.
Localization and Function of Central Noradrenergic Synapses
Authors: Bloom F. E.
Published: June 2020

The goal of determining the functional properties of central neurons transmitting through the release of norepinephrine (NE) has motivated multiple attempts to identify the structures in the CNS containing NE through selective and sensitive cytochemical methods. In our studies on the cellular effects of NE in the cerebellar and hippocampal cortices (reviewed in 1, 2, 3), my colleagues and I placed great reliance on the presumptive evidence that NE-containing boutons made contact mainly with cerebellar Purkinje cells and hippocampal pyramidal cells. Our cytochemical observations were obtained by a variety of methods ranging from formaldehyde-induced fluorescence histochemistry of endogenous catecholamines or on actively accumulated related structural analogs with greater histochemical reactivity, to electron microscopic autoradiography of sites labeled with H3-NE or to detection of axons and boutons which degenerate after acute exposure to intracisternal injections of 6-hydroxydopamine.
Membranes of Mammalian Sperm and Capacitation
Authors: Gordon M.
Published: June 2020

Capacitation prepares the mammalian sperm for interaction with the ovum. It occurs in the female genital tract and involves a change in the properties of the membrane over the head. The head membranes are morphologically specialized in different regions. The portion overlying the acrosome is loose and not linked to a cytoplasmic substratum (Fig. 1). It is differentiated from the tight membrane apposed to the post acrosomal cap (PAC) (1). Following capacitation, the periacrosomal segment fuses with the outer membrane of the acrosome allowing escape of the acrosomal contents, the “acrosome reaction”. The fertilizing sperm contacts the vitellus at the PAC. Thus the outer membrane is separated into a portion concerned with the loss of the acrosome and another with ovum contact. The outer membrane of the acrosome is distinguished from the inner since it participates in the acrosome reaction. Cytochemical analysis of the cell membrane supports the concept that the stimulus for capacitation is a change in the properties of the plasmalemma induced by fluids of the female tract.
Fine Structure of Lipid Droplets in Sertoli Cells
Authors: Chen I-li , Gravis Curtis J. , Yates Robert D.
Published: June 2020

Lipid droplets synthesized within a cell do not exhibit a typical trilaminar limiting membrane but rather a half-membrane. Lipid droplets in Sertoli cells have been implicated as sources of building materials for steroid hormone synthesis and may be derived from phagocytized residual bodies cast off by maturing spermatids. If this is the case, lipid droplets free in the cytoplasm of the Sertoli cells are provided with a typical unit membrane derived from the plasma membrane of the Sertoli cell. The present studies were concerned with the fine structure of Sertoli cell lipid droplets in normal and experimentally induced (hypoxia and adrenalin treated and cryptorchidized) degenerating seminiferous tubules of Syrian hamsters with special reference to the limiting membrane and their relationship to primary lysosomes. The cytochemical identification of the lipid content was based on chloroformmethanol or acetone extraction of glutaraldehyde fixed tissue slices prior to osmic acid postfixation and lipase digestion.
Electron Microscopy of A New Plant-Pathogenic Spiroplasma Isolated From Opuntia
Authors: KONDO F. , MCINTOSH A. H. , PADHI S. B. , MARAMOROSCH K.
Published: June 2020

Thin section electron micrographs of phloem from the ornamental cactus Opuntia tuna monstrosa revealed the presence of wall-less prokaryotic cells earlier described as mycoplasma-like bodies (1). Isolation and growth of the microorganism in liquid media yielded cultures of a spiroplasma, as ascertained by darkfield microscopy. Negatively stained spiroplasmas (Fig. 1) were reminiscent of Spiroplasma citri (2) and of corn stunt spiroplasma (3). The spirals observed in negatively stained preparations seemed attached to blebs. PAGE analysis showed distinct differences between the three species of microorganisms. Serological tests confirm ed that the spiroplasma isolated from the ornamental cactus differed from S. citri and from corn stunt spiroplasma. On agar media, “fried-egg” colonies were formed (Fig. 2).
Effect of Vinblastine Sulfate on Visceral Epithelial Cells of Rat Renal Corpuscle (Scanning Electron Microscopy)
Authors: Tyson G. E.
Published: June 2020

Visceral epithelial cells (podocytes) of the rat renal corpuscle are highly branched -in shape (1-3) and contain numerous cytoplasmic microtubules (4). In a previous study of podocytes by Tyson and Bulger (4), microtubule loss was induced by intravenous injections of vinblastine sulfate, and then renal tissue was examined by routine transmission electron microscopy. With a vinblastine treatment that resulted in nearly complete absence of microtubules in podocytes, examination of ultrathin sections yielded no evidence that loss of microtubules was accompanied by a change in cell shape. Similar experiments, described below, have now been performed using scanning electron microscopy, in order to facilitate recognition of subtle shape changes that would not be readily apparent in sectioned material.
Birefringence and Ultrastructure of Isolated, Stabilized Spindles
Authors: LaFountain James R. , Evans Robert L.
Published: June 2020

Previous investigations on the spindle apparatus in primary spermatocytes of the crane fly, Nephrotoma suturalis, with polarizing optics have shown that chromosomal fibers can be detected as positively birefringent bands extending from the chromosomes to the poles (1). Chromosomal fiber birefringence reaches a maximum at metaphase when five distinct fibers can be seen in each half spindle. An obvious question raised by these results was what is the ultrastructural basis of birefringence?

Initial attempts to characterize the ultrastructure of crane-fly spindles showed that there were hundreds of microtubules (MTs) in these spindles, but there was no evidence that they were distributed in a pattern that corresponded to the pattern of birefringence (2,3).
Morphological Alterations of the Blood-Brain Barrier in Experimental Serum Sickness (ESS)
Authors: Donald A. Davis , Thomas H. Milhorat
Published: June 2020

Information concerning the effects of systemic diseases on the blood-brain barrier is limited. Lampert and Carpenter (1) and Lampert et al. (2) have shown that experimental lead encephalalopathy produces a toxic vasculitis which permits intravascularly injected thorotrast to escape from cerebral capillaries into the perivascular and extracellular spaces. Other experiments (summarized in 3) have demonstrated an increased permeability of cerebral capillaries as a consequence of cerebral trauma, chemically induced vasculitis, hypertension, and radiation.

Acute serum sickness was produced in adult male Wistar rats according to the “one shot” technique of Kniker and Cochrane (4). After seven to eight days the animals were decapitated and tissue samples from the cerebral cortex and periventricular white matter were quickly excised and placed in vials for prefixation in 1% depolymerized paraformaldehyde and 31 purified glutaraldehyde in 0.1M phosphate buffer (pH 7.5) for 24 hours at 4C.
Oligodendrocytes in Developing Hameter Cerebral Cortex
Authors: Tank Buschmann MB.
Published: June 2020

Development of oligodendrocytes in rat corpus callosum was described as a sequential change in cytoplasmic density which progressed from light to medium to dark (1). In rat optic nerve, changes in cytoplasmic density were not observed, but significant changes in morphology occurred just prior to and during myelination (2). In our study, the ultrastructural development of oligodendrocytes was studied in newborn, 5-, 10-, 15-, 20-day and adult frontal cortex of the golden hamster (Mesocricetus auratus).

Young and adult hamster brains were perfused with paraformaldehyde-glutaraldehyde in sodium cacodylate buffer at pH 7.3 according to the method of Peters (3). Tissue samples of layer V of the frontal cortex were post-fixed in 2% osmium tetroxide, dehydrated in acetone and embedded in Epon-Araldite resin.
Ultrastructural Features of the Oral Apparatus of Stentor
Authors: Howell Elizabeth F.
Published: June 2020

The ultrastructure of the normal oral apparatus of Stentor has not been extensively studied. I report here on the ultrastructure of the buccal cavity of Stentor coeruleus.

Stentor coeruleus was fixed in either a buffered mixture of osmium tetroxide and glutaraldehyde, or in buffered glutaraldehyde alone. Cells were then dehydrated and embedded in a mixture of Epon and Araldite.

An extensive adoral zone of membranelles surrounds the anterior of the cell, and each membranelle consists of 2 parallel rows of cilia. These extend down into the buccal cavity. Two microtubular root fibers, or nemadesmata (Figs. 2 and 5), extend deeply into the cytoplasm from the base of each ciliary kinetosome. Mitochondria are usually closely associated with the root fiber bundles, and small vesicles are present between the nemadesmata of adjacent kinetosomes (Fig. 5). In the cytopharyngeal, non-ciliated areas of the buccal cavity, microtubular ribbons which extend into the cytoplasm are aligned perpendicular to the plasma membrane of the buccal cavity (Figs. 1 and 2).
The Fine Structure of Irradiated Mouse Heart
Authors: Yang Vivian V. , Phyllis Stearner S.
Published: June 2020

The heart is generally considered a radioresistant organ, and has received relatively little study after total-body irradiation with doses below the acutely lethal range. Some late damage in the irradiated heart has been described at the light microscopic level. However, since the dimensions of many important structures of the blood vessel wall are submicroscopic, investigators have turned to the electron microscope for adequate visualization of histopathological changes. Our studies are designed to evaluate ultrastructural changes in the mouse heart, particularly in the capillaries and muscle fibers, for 18 months after total-body exposure, and to compare the effects of 240 rad fission neutrons and 788 rad 60Co γ-rays.

Three animals from each irradiated group and three control mice were sacrificed by ether inhalation at 4 days, and at 1, 3, 6, 12, and 18 months after irradiation. The thorax was opened and the heart was fixed briefly in situwith Karnofsky's fixative.
Cytosomal and Neuronal Changes During Photoreception as Related to Ionic Permeability and Ciliary Activity in Mytilus Epulis
Authors: Murphy Judith A. , Paparo Anthony A.
Published: June 2020

The lateral ciliated cells in the bivalve, M. edulis are controlled by the nervous system. Ultrastructural studies reveal pigment granules (cytosomes) occurring in the nerve endings under these cells. In response to light, there is a gradual lateral cilioinhibition coupled with a change in morphology of these pigment granules. The purpose of this study was to examine lateral ciliary activity during photoreception as related to both, changes in the pigment granules, and neuronal Ca/K shifts.

Gill preparations were isolated and subsequent stroboscopic measurements of lateral cilia were made. Specimens were exposed to light or darkness. The following drugs were added by perfusion: 10-100 mM Ca and 10-6 M ethylene glycol-bis(amino-ethyl-ether)-N,N'-tetraacetic acid (EGTA). Measurements of the orange yellow fluorophore were made on a Leitz MPV system.
Ultrastructural Surface Characterization of Cultured Intracranial Tumors
Authors: Liszczak T. , Jacobson S. , Kornblith P.
Published: June 2020

One property of a malignant cell is its decreased intercellular adhesiveness in vivo(l), and in vitro(2). In an attempt to visualize any morphological correlates associated with this phenomenon we utilized the replica technique to examine cell surfaces and cell to substrate attachment regions in cultured intracranial tumors, tumors from other sites and reactive cells.

Cells were explanted onto glass coverslips in Leighton tubes, cultured to approximately 50%confluency, buffer rinsed, 2.5% glutaraldehyde fixed, chrome-osmium postfixed, critical point dried with Freon 13 and 113, and replicated with platinum carbon. The cells and coverslips were dissolved away by hydroflouric acid.
Development of the Foramen Secundum in the Chick as Observed by Scanning Electron Microscopy
Authors: Hendrix M.J.C. , Morse D.E.
Published: June 2020

Atrial septal defects are considered the most common congenital cardiac anomaly occurring in humans. In studying the normal sequential development of the atrial septum, chick embryos of the White Leghorn strain were prepared for scanning electron microscopy and the results were then extrapolated to the human heart. One-hundred-eighty chick embryos from 2 to 21 days of age were removed from their shells and immersed in cold cacodylate-buffered aldehyde fixative . Twenty-four embryos through the first week post-hatching were perfused in vivo using cold cacodylate-buffered aldehyde fixative with procaine hydrochloride. The hearts were immediately dissected free and remained in the fixative a minimum of 2 hours. In most cases, the lateral atrial walls were removed during this period. The tissues were then dehydrated using a series of ascending grades of ethanol; final dehydration of the tissues was achieved via the critical point drying method followed by sputter-coating with goldpalladium.
Acidophil Stem Cell Adenoma of the Human Pituitary: A New Entity
Authors: Horvath E. , Kovacs K. , Ezrin C.
Published: June 2020

Electron microscopy and immunocytochemistry have been applied to determine the origin of 3 pituitary adenomas found among 70 surgically removed hypophysial tumors, which did not correspond to any tumor type classified so far.

The tumors were surgically removed from 3 male patients between 38 - 66 years of age. Clinically, no signs indicative of hormonal hypersecretion were evident. The patients complained of decreased libido and progressing visual disturbances. Blood prolactin levels were markedly elevated in 2 cases, and were normal in one case. Blood growth hormone levels were normal. Additional endocrine laboratory tests failed to provide contributory data.

By histology, the tumors corresponded to sparsely granulated acidophilicchromophobic adenomas. The cytoplasm of adenoma cells stained neither with PAS, nor with aniline blue, lead hematoxylin. Negative staining was obtained by various acid dyes, such as eosin, phloxine, orange G or light green, except for occasional granules in a few adenoma cells.
Banded Structures in the Connective Tissue of Meningioma
Authors: Sun C. N. , White H. J.
Published: June 2020

Previously, we have reported on extracellular cross-striated banded structures in human connective tissues of a variety of organs (1). Since then, more material has been examined and other techniques applied. Recently, we studied a fibrocytic meningioma of the falx. After the specimen was fixed in 4% buffered glutaraldehyde and post-fixed in 1% buffered osmium tetroxide, other routine procedures were followed for embedding in Epon 812. Sections were stained with uranyl acetate and lead citrate. There were numerous cross striated banded structures in aggregated bundle forms found in the connecfive tissue of the tumor. The banded material has a periodicity of about 450 Å and where it assumes a filamentous arrangement, appears to be about 800 Å in diameter. In comparison with the vicinal native collagen fibrils, the banded material Is sometimes about twice the diameter of native collagen.
Ultrastructural Change in Muscle Biopsy From a Case of Progressive Ophthalmoplegia
Authors: Dodson R. F. , Patten B. M. , Chu L. W-F.
Published: June 2020

Progressive external ophthalmoplegia is a disease which is classifiable as a “mitochondrial myopathy” (1). Mitochondrial changes have been reported as giant mitochondria with swirls of cristae, giant mitochondria with paracrystalline structures, and in extreme instances, abnormal mitochondria were reported to be replaced by dense rectangular inclusions and occasionally showed complete transition to crystalline structures (2). Presently we are reporting ultra structural findings from muscle biopsies obtained from a 51 year old man who had been clinically and histochemically diagnosed as having chronic external ophthalmoplegia. Histochemical findings indicate the presence of abnormal mitochondria as a component of the “ragged-red fibers” (3).

Specimens from open biopsy of biceps muscle were dissected in a 1 cm long muscle clamp and immediately placed in a 3% glutaraldehyde in 0.1M phosphate buffered fixative.
Possible Strain Related Variations in Mouse Mammary Tumor Virus Envelope Glycoproteins aas Detected by Ferritin Conjugated Wheat Germ Lectin
Authors: Hixson D. C. , Bowen J. M. , Scanlon M. , Nash M. , Dmochowski L.
Published: June 2020

The role of envelope glycoproteins in the infectivity and host range of different mouse mammary tumor viruses (MMTV) has been the subject of extensive investigation by many laboratories. Although strain related antigenic differences have been observed, these differences do not appear to be directly related to infectivity and host range and are thus different from type specific antigenicities observed in avian and C-type virus systems. Blair (1) has hypothesized that these antigenic differences in MMTV may result from selective pressures causing configurational or compositional alterations in viral glycoproteins that enhance survival of a particular strain of MMTV in its natural host. The present studies were initiated to determine if strain specific variations in MMTV envelope carbohydrate composition could be detected by ferritin conjugated plant lectins with different carbohydrate binding specificities. The present communication describes results of labeling studies using ferritin conjugated wheat germ lectin (Ft-WGA) specific for 2-acetamido-2-deoxy-D-glucose.
Electron Diffraction Studies in Mercury Neuropoisoning
Authors: Shelton W. W. , Chatterjee T. K.
Published: June 2020

Mercurials have been shown to accumulate in the vertebrate cerebellum and ultimately induce cytological pathology, especially in the granule cell layer, under conditions of experimental poisoning (1). This report describes some preliminary results of electron diffraction and electron microscopy (Philips EM300) studies on cerebellar tissue of rats poisoned with mercuric bichloride (MB) (Fisher Scientific Co.) and phenylmercuric acetate (PMA) (Eastman). One group of male albino Sprague Dawley rats was treated with single subcutaneous injections of 10 mg. MB per kg. body weight and observed for one week, and another group intraperitoneally with 2 mg. PMA per kg. body weight three times a week for two months. The animals were anesthetized and perfused intracardially with 3% glutaraldehyde in 0.1M cacodylate buffer and the selected tissue samples were further processed according to standard methods, terminating with uranyl acetate and lead citrate staining.
Tannic Acid as a Mordant for Heavy Metal Stains
Authors: Wagner Roger C.
Published: June 2020

Tannic acid used concomitantly with glutaraldehyde fixation results in an increase in the electron-density and apparent thickness of the outer leaflet of cell-surface membranes (1,2). This effect has been attributed to binding of tannic acid to cell-surface proteins and subsequent chelation of heavy-metal ions (2). In isolated capillary endothelium (3), the localization and degree of this enhanced density varies according to the point at which cells are treated with tannic acid during fixation and staining and with selective omission of stains and fixatives

Treatment of cells with tannic acid(2%) and glutaraldehyde (2%)followed by osmium(l%) and counterstaining of sections (saturated uranyl acetate-10 min., Reynold's lead citrate-3 min.) results in an increase in thickness and electron density of the outer leaflet of all surface membranes including those comprising micropinocytic caveolae (fig. 1). When cells are fixed with glutaraldehyde prior to tannic acid treatment, both inner and outer leaflets of both surface and intracellular membrane systems exhibit an increase in density and apparent thickness (fig. 2).