bluuebunny/crossref_metadata_2025 huggingface dataset:
UHV conversion of a 300 kV high-resolution electron microscope
Authors: Swann Peter R. , Jones Joseph S. , Krivanek Ondrei L. , Smith David J. , Venables John A. , Cowley John M.
Published: June 2020

Ultra-high-vacuum high-resolution electron microscopy (UHV-HREM) is a powerful technique for studying the structure of surfaces, and for characterizing the mechanisms and kinetics of surface and interface reactions. It requires an electron microscope capable of atomic resolution, a vacuum of about 10-10torr around the sample, and a range of specimen treatment capabilities. We have replaced the standard specimen chamber of a Philips 430ST high resolution microscope by a special UHV chamber which allows for limited specimen treatment in-situ, and a full range of specimen treatments in a preparation chamber mounted on the side of the microscope column. At 300 kV, the objective lens (Cs= Cc= 1.1mm) of the 430ST has demonstrated a point-to-point resolution of 2.0 Å, and a spatial frequency transfer limit with axial illumination of better than 1.5 Å. A critical specification for the microscope conversion was that this performance should not be compromised even under full UHV operation.
In situ fracture of SiC-whisker-reinforced Al203
Authors: Angelini P. , Becher P. F.
Published: June 2020

Dynamic in situ fracture experiments were performed on SiC-whisker-reinforced Al203 to determine the mechanisms responsible for the observed increase in fracture resistance. Observations of both stationary as well as moving crack tips while the specimen was under load showed that fracture resistance is due to debonding near the whisker matrix interface, crack deflection, pinning, and bridging by SiC whiskers.

Two types of hot pressed specimens were evaluated. One contained 20 vol % SiC whiskers as well as 0.5 wt % MgO and 2.0 wt % Y203 as sintering aids. Another was fabricated with only 5 vol % SiC whiskers with no sintering aids. Specimens were prepared for TEM by cutting the material perpendicular to the hot pressing axis, grinding, polishing, dimpling, and argon ion milling.
Faceting behavior of Al2O3 in the presence of glassy phase
Authors: Kouh Simpson Y.
Published: June 2020

It is well known that A1203 can reach near-theoretical density by a liquid-phase sintering process in which an amorphous glass phase containing SiO2, CaO and Al2O3 helps density Al2O3. Understanding the faceting behavior of Al2O3 in the presence of such a glass phase is important since the movement of the facets and the type of facets that form during the liquid-phase sintering process determine the final microstructure of the grain boundaries that ultimately control the properties of Al2O3 compacts. As a part of a larger study on the role of impurities in the sintering process of Al2O3 compacts, a new investigation has been carried out to examine the nature and the type (e.g. facet planes) of the crystalline Al2O3, / amorphous glass interface in systematic experiments in which densification aids such as SiO2, CaO and MgO are reacted with single crystal Al2O3. Substantial anisotropy, both from an energy consideration and a kinetics consideration, in the Al2O3/ glass interface is to be expected, and has been observed in this investigation.
Energy loss and x-ray analysis of major constituents in silicon oxynitride ceramics
Authors: Braue W. , Skiff W.M. , Carpenter R.W. , Ma H.
Published: June 2020

Silicon Oxynitride (Si2N2O) is an orthorhombic phase that often occurs as a minor phase In Si3N4-base structural ceramics. It is thought to form as a result of oxygen surface contamination of the constituent powder particles, usually exhibits a rod or plate morphology and may react with sintering aids or impurities in the system. The structure of Si2N2O is a network of distorted Si-centered SiN3O tetrahedra in which the tetrahedral environment of the Si is similar to its environment in Si3N4 and SiO2. The average Si-N bond length is smaller, compared to both Si3N4 allotropes, with an Si-0 bond length typical of most silicates. EELS spectra of Si3 N4, and SiO2 are well known.

Here we present the first results of a high resolution EELS study to compare the energy loss core edges of Si, 0 and N in Si2N2O to the corresponding edges in Si3N4 and SiO2.
HRTEM of hydroxyapatite in carious human tooth enamel
Authors: Barry J. C. , Bres E. F.
Published: June 2020

Human dental enamel is composed 98% by weight of small, densely packed carbonated hydroxyapatite (HAP) crystals. These crystals have an unusual morphology and often contain a “central dark line” (CDL) defect. The HAP crystals in carious enamel are preferentially dissolved at the CDL defect. Bres et al. have identified three types of disorder in human tooth enamel crystallites near to the crystal midline: a) regions of lattice buckling and departure from hexagonal symmetry, b) dislocations and c) grain and twin boundaries. Nelson et al. have obtained very clear images of planar defects, similar to the CDL defects in human enamel, at the centers of crystals of certain synthetic carbonated apatites. In this present study HRTEM images have been obtained from carious regions of tooth enamel, and an analysis of the results is attemped in the light of previous work.
In situ transmission electron microscopy study of the paraelectric to ferroelectric (cubic to tetragonal) phase transformation in lanthanum-modified lead titanate ceramics
Authors: Demczyk B. G.
Published: June 2020

Lead titanate (PbTiO3) forms the ferroelectric end of the ferroelectric-antiferroelectric solid solution series PbTiO3-PbZrO3 (PZT), which is of considerable interest in various piezoelectric applications. Above the Curie point (TC), the material is cubic (paraelectric), point group m3m. Below this temperature transformation occurs to the tetragonal (ferroelectric) phase, point group 4mm. The strain generated in this transformation is relieved via the formation of twin-related structural (ferroelectric) domains. Lanthanum is added to polycrystalline lead titanate to aid in the poling operation (alignment of electric dipoles in individual grains via the application of a large electric field), through a reduction of the c/a ratio in the tetragonal phase. This transformation has been observed in this material in-situ via transmission electron microscopy (TEM).
TEM investigation of extended defects in hexagonal BaTiO3
Authors: Eibl O. , Pongratz p. , Skalicky P. , Mazur J.H.
Published: June 2020

Barium titanate is known mostly for the ferroelectric, piezoelectric and dielectric properties of its tetragonal phase. Above 1330°c in strongly reducing atmosphere (pO2 = 10-20 bar) BaTi03 transforms from the cubic to the high temperature hexagonal polymorph preserved at room temperature as a metastable phase containing defects which are a subject of the present investigation. The hexagonal phase consists of close packed (Ba-03) planes and Ti planes stacked along the [001] direction resulting in a ABCACB stacking sequence. In this structure TiO6 octahedra are linked either by common corners or common faces. A high resolution image of the projected structure along [100] is shown in Fig. 1.

Stacking faults are observed on (001) planes. The density of faults is l-2xl06 m-1 and the faults are extending over the whole grain size which is a few hundred microns. Partial dislocations usually 100 nm apart are found in the fault plane.
Near-Field Scanning Optical Microscopy
Authors: Betzig E. , Isaacson M. , Lewis A. , Lin K.
Published: June 2020

The spatial resolution of most of the imaging or microcharacterization methods presently in use are fundamentally limited by the wavelength of the exciting or the emitted radiation being used. In general, the smaller the wavelength of the exciting probe, the greater the structural damage to the sample under study. Thus, the requirements of minimal sample alteration and high spatial resolution seem to be at odds with one another.

However, the reason for this wavelength resolution limit is due to the far field methods for producing or detecting the radiation of interest. If one does not use far field optics, but rather the method of near field imaging, the spatial resolution attainable can be much smaller than the wavelength of the radiation used. This method of near field imaging has a general applicability for all wave probes.
Evidence for ordered Fe3Ni
Authors: Reuter K.B. , Williams D.B. , Goldstein J.I.
Published: June 2020

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.
Doping of vanadium alloys with helium using tritium
Authors: Braski D. N.
Published: June 2020

Vanadium alloys are currently being evaluated for possible future application as a structural first wall for a fusion reactor. Major concerns are the displacement damage and high rates of helium production in a first wall caused by the 14 MeV neutrons from the plasma. To study the effect of helium on the microstructure and to simulate its effect in irradiation experiments, various vanadium alloys have been doped with helium using the “tritium trick” procedure.

Vanadium alloy specimens were heated at 400°C in a stainless steel retort with tritium at 53 kPa (400 torr). Helium concentration was controlled by holding the specimens under these conditions for a predetermined time to allow the tritium, which is quite soluble in vanadium, to diffuse into the material and transmute to 3He. The process was stopped by reducing the pressure and increasing the temperature in the retort to 700°C. This removed the remaining tritium from the specimens and left the insoluble 3He behind in the microstructure.
The effects of ion-implanted Ce and V on transient oxidation of NiCrAl
Authors: Cocking J. L. , Sprague J. A. , Reed J. R.
Published: June 2020

Plasma-sprayed thermal barrier coating systems are receiving considerable attention because of their potential to optimise the capability of gas turbine engines operating in severe thermal or corrosive environments. The coating system generally consists of a metallic bond coat and a ceramic top coat. The ceramic layer in the system is usually not fully dense. One of the critical areas which must be considered in the use of such coatings is the problem of delamination of the ceramic layer as a result of stresses generated by oxidation of the bond coat. Part of the present program is to examine the transient oxides formed on a representative bond coat material and to compare them with oxides formed on the same material after it has been implanted with species such as V which are known to have a detrimental effect on the oxidation behavior of the material and other species such as Ce which have been identified as having the potential for beneficial effects.
The interface between sipos and silicon
Authors: Posthill J.B. , Ozguz V.H. , Mortman J.J.
Published: June 2020

Semi-insulating polycrystalline silicon (SIPOS) is formed by introducing oxygen during the deposition of silicon. SIPOS is currently used as a passivation layer for high voltage devices. More recently, it has also been introduced as an emitter material for bipolar transistors. Electrical properties are expected to be influenced by many factors, some of which are: dopant type and concentration, the grain size and contiguity of the silicon crystals, and the microstructure of the SIPOS/Si interface. This contribution reports cross-section TEM results obtained from samples that have undergone different silicon wafer preparation prior to SIPOS deposition and different post-deposition rapid thermal anneal (RTA) treatments.

One set of silicon wafers was dipped in buffered HF immediately prior to SIPOS deposition in order to remove any oxide. A thin chemical oxide ∼1 nm thick was intentionally left on the other set of wafers.
Microtwin morphology for silicon on sapphire
Authors: Twigg M. E. , Richmond E. D.
Published: June 2020

It is well established that microtwins play an important role in accommodating stresses that accompany the growth of Si on sapphire (SOS) for the (001)Si/(1012)sapphire hetero-epitaxial system. When examined in cross section along the <110> direction by the transmission electron microscope (TEM), microtwins corresponding to two of the four twinning systems are clearly visible. It is also apparent that one of the two twinning systems dominates. For the [110] beam direction, the (111) twinning system accounts for the majority of visible microtwins, whereas the (111) twinning system accounts for the minority. It is thought that the abundance of (111) twins is due to a coincidence between the (111) planes of the Si matrix and the (1232) planes of the sapphire substrate; there is also a coincidence between the (113) planes of the majority twinning system and the (0112) sapphire planes. There are no such coincidences, however, between the minority twinning system in Si and the sapphire substrate.
In-Situ TEM study of the role of secondary grain boundary dislo-cations in grain boundary migration and atom source/sink action
Authors: Babcock S. E. , Balluffi R. W.
Published: June 2020

Over the past several years, a wealth of experimental evidence concerning the structure of simple grain boundaries (GBs) in metals has accumulated which suggests that the GBD/SU description of GB structure is applicable, at least at some level, to GBs in general. According to this model, high-angle GBs contain intrinsic arrays of grain boundary dislocations (GBDs) possessing Burgers vectors (b) which are translation vectors of an appropriate DSC-lattice, arranged in a network which is consistent with Frank's formula.

A special property of secondary GBDs (SGBDs), i.e., GBDs possessing bs which are not lattice vectors of either of the adjoining crystals, is that a step in the boundary plane is often associated with their core.
Substructure Of needle-shaped precipitates in An Al-Ge alloy
Authors: Dahme U. , Westmacot K.H.
Published: June 2020

Dilute Al-Ge alloys provide a good model for metal-semiconductor interface studies because clean interfaces in different orientations can be grown by precipitating Ge from the A1 terminal solid solution. A great variety of orientation relationships and morphologies have been observed in this alloy, including plates, laths, needles and tetrahedral Needle precipitates along <100> A1 which are invariably twinned form in abundance during low-temperature aging. Since <110> Ge is exactly parallel to the needle axis, high resolution microscopy allows direct and accurate analysis of the precipitate orientation relationship, morphology, interface and defect structure.

It was reported earlier that the particle morphology usually conformed to the symmetry of its orientation relationship with the matrix. This rule was broken only by some of the twinning defects observed. In the present contribution we focus attention on the substructure formed by these twins and their relationship to the particle morphology.
Crystallographic orientation of aluminum whiskers formed by electromigration using transmission electron microscopy
Authors: Kitchen D. R. , Linder S. L. , Omlor R. E. , Lloyd P. F.
Published: June 2020

Electromigration is a well known phenomenon in the aluminum films of an integrated circuit and occurs at elevated temperatures under the influence of current densities exceeding 10 amps/cm2. The failure modes are characteristically cracks, voids or hillocks in the metal lines, causing open-circuits. The majority of research in the electromigration of aluminum conductors examines the formation of these voids and hillocks in the linestripes. This is unfortunate since experiments have shown that short-circuits caused by whisker formation between adjacent stripes or between multi-level structures can be equally damaging to device performance. Most previous work has involved examining whiskers grown by annealing, however, very little work has been carried out on whiskers produced by electromigration. In this investigation aluminum whiskers formed by electromigration were studied with a transmission electron microsope to determine their crystallographic orientation.
Palladium silicides above the Pd2Si ⇋ PdSi transformation temperature
Authors: Vanderwalker D. M.
Published: June 2020

There is considerable interest in the formation of intermetallic compounds at metal-semiconductor contacts. The interfacial structure controls the barrier height. In the Pd-Si system, thin film experiments were performed over a range of temperatures. Pd2Si was found in samples annealed at temperatures below 810°C. Above 810°C, Pd2Si was observed to transform to PdSi. Pd2Si seeds were found to form in amorphous Pd80Si20 annealed at 175°C. This paper examines the palladium silicides formed just above the Pd2Si ⇋ PdSi transformation temperature.

A Pd layer was evaporated on Si wafers at the (111) and (001) orientation in a vacuum pressure less than 10-6 torr. The samples were encapsulated in vacuum tubes before annealing at 825°C for one hour. TEM specimens were prepared by mechanical, then chemical thinning from one side with a 6/7 nitric acid 1/7 hydrofloric acid solution. The TEM was performed on the JEM 200CX and Phillips 400.
A distorted 6H structure in an A1-Li-Cu-Mg-Zr- alloy
Authors: Zhang J. P. , Tsurata C. , Marks L. D.
Published: June 2020

The powder extracted from a Al-base alloy containing Li, Cu, Mg and Zr was examined in a H9000 electron microscope equipped with ultra-high resolution polepieces having Cs = 0.9mm at 300 KV for HREM studies.

Figure 1 is a typical electron diffraction pattern of 6H structure: spots are grouped as six neighbours along c direction. For 00ℓ when ℓ = 6n (n = 0, 1, …) the diffraction spots occur with strong intensities while for 10ℓ, the reflections are almost extinct when ℓ = 6n. The stacking sequence of (001) planes is ABCACB composed by 3R, ABC, and anti 3R, ACB, twinned structures with a = 0.27 nm , c = 1.52 nm. Figure 2 is a structure image in the same direction of Fig.l, which shows the (001) stacking clearly. No twinned structure was observed because the stacking sequence is modified to ABCAB'B, where the C of anti 3R is changed to B’ that is close to B but different.
Transmission electron microscopy of polymers
Authors: Thomas Edwin L.
Published: June 2020

Transmission electron microscopy continues to play a major role in micro-structural characterization of polymers. Additionally, as evidenced by the special symposium on electron crystallography at this EMSA meeting, electron diffraction, as applied to polymer crystals, is also a vigorous area of research. Because many of the interesting morphological features of polymer systems are at and below the micron scale, TEM is a most fruitful technique. Applications range from simple assessment of dispersed phase particle size in blends to HREM molecular imaging of defects in crystals. Thus polymer scientists probe structures over about 4 orders of magnitude in size, and the versatility of the TEM in such endeavors is evident from its essentially ubiquitous appearance in all modern physical sciences laboratories.

While there are a host of standard and advanced texts on the application of TEM to metals and to biology, there are only a few review papers on polymer microscopy and one just-published book.
Quantitative Crystal Structure Analysis In The Electron Microscope
Authors: Dorset Douglas L.
Published: June 2020

Electron crystallography is a term which has emerged in the past few years to describe the quantitative structure analysis of microcrystalline preparations in the electron microscope. The field represents the confluence of two techniques, i.e. the ultramicroscopic capabilities of the electron microscope coupled with analytical techniques long in use by X-ray crystallographers. In the area of organic materials, the most visible success of the technique to date has been in the structure analysis of thin protein microcrystals typically to ca20 Å resolution but sometimes out to e.g. 7 Å and, in this field, there has been considerable effort by an increasing number of laboratories.

Although the electron crystallography of small organic molecules and linear polymers has a much longer history than the application to globular proteins, one cannot cite an overwhelming enthusiasm for this technique, despite its promise as a probe for molecules which are not easily crystallized to sample sizes useful for single crystal X-ray diffraction measurements.
Visualization of continuous crystal formation in high-density polyethylene
Authors: Brady J. M. , Thomas E. L.
Published: June 2020

Though chemically simple, polyethylene has proven to be an extremely versatile polymer. Its physical and mechanical properties can be made to cover a broad range of requirements by varying processing, branching, and the molecular weight of the material. In particular, ultrahigh modulus polyethylene (tensile moduli exceeding 200 Gpa) has been made by solid state extrusion (SSE) at 110 C followed by post drawing (PD) at 125 C. The objective of the following study was to investigate the evolution of structure during the SSE/PD process, and to identify those morphological features which give rise to ultimate properties.

The SSE/PD process was mimicked here by deforming thin films of HDPE at high temperature (129 C). High density polyethylene (HDPE) of Mw = 200,000 and Mw /Mn =7-13 was used. As-processed films were highly oriented and displayed a single crystal-like textured shish-kebab morphology.
Structure-property relations of liquid crystalline polymers
Authors: Sawyer Linda C.
Published: June 2020

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.

Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.
High resolution and radiation damage of organic crystals
Authors: Fryer J.R
Published: June 2020

The entities involved in chemical reactions are either atoms or molecules. The imaging of atoms poses problems in resolution and identification but molecules are larger and often have recognisable shapes. Fig.1 shows the calculated images of chlorinated copper phthalocyanine as a function of resolution. Normally specimens are prepared as epitaxial films and there is a specific orientation of the specimen that provides a clear projection of the molecular shape. Fig.2a and Fig.2b illustrate this for a polymeric phthalocyanine-(Al F Pc)n. Fig.2a shows the lattice obtained from non-epitaxial crystals and Fig.2b from an epitaxial film showing a projection of the tetragonal unit cell. These epitaxial films have been used to obtain molecular images of chlorinated copper phthalocyanine brominated copper phthalocyanine, copper phthalocyanine, metal free phthalocyanine, phthalocyanine polymers, the hydrocarbons quaterrylene, anthanthrene, hexabenzocoronene and lattice images from paraffins and phospholipids.
Electron microscopy of polymer blends
Authors: Briber Robert M.
Published: June 2020

Polymer blends have come to play an increasingly important role in materials science as the need for polymeric materials with wider ranging properties has developed. Data will be presented in this paper on two polymer blend systems that have benefited from the use of electron microscopy in understanding the complex morphologies than can occur in polymer systems.

Blends of Poly(vinylidene fluoride) and poly(ethyl acrylate)

Poly(vinylidene fluoride) (PVF2) and poly(ethyl acrylate) (PEA) form a miscible, single phase melt over the composition range of 50% PVF2 (by weight) and less. The melt exhibits phase separation upon heating to 10-50°C above the observed melting point of PVF2, depending on the composition, PVF2 is a semicrystalline polymer, while PEA is an amorphous polymer. The fact that PVF2 is compatible in the melt with PEA has allowed for detailed morphological studies of single crystal lamellae and spherulites of the α crystal form of PVF2 grown at temperatures very close to those found in conventional melt crystallization.
Microstructural studies of glassy polymer deformation
Authors: Henkee C. S.
Published: June 2020

Upon the application of a tensile load, many polymer glasses undergo plastic deformation via the process of crazing. Using transmission electron microscopy (TEM), the nature of the crazing process can be investigated. As shown in Figure 1, a single craze consists of a very localized region of plastic deformation. The craze is delineated from the undeformed amorphous glass by sharp boundaries, and is spanned by a network of fine fibrils. For polystyrene (PS), the fibrils themselves typically range from 5 to 50 nm in diameter and have important load bearing capabilities. Crazing is an important mechanism by which the polymer glass absorbs energy during the failure process; thus improvement in impact toughness is achieved in many polymer glasses through loading the polymer with small rubber particles that readily nucleate crazes. It should also be noted however, the cracks that eventually lead to catastrophic failure generally nucleate within crazed regions.
Optimizing the collector solid angle for the low-loss electron image in the Scanning Electron Microscope
Authors: Wells Oliver C.
Published: June 2020

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is formed by collecting backscattered electrons (BSE) that have lost less than a specified energy. Compared to the secondary electron (SE) image, these images are less affected by specimen charging and show the surface topography clearly when examining uncoated photoresist. However, LLE images sometimes contain dark shadows caused by the limited solid angle of the LLE detector. Here, we describe a way to position the sample (with a given LLE detector) so as to reduce these shadows as far as possible.

The SEM was a Cambridge S-250 Mk. III with a tungsten filament. An experimental LLE detector was added. The SE image was obtained using the SE detector ordinarily present in the SEM.

The LLE detector is shown in Fig. 1. The specimen is mounted close to the lens in the SEM with a glancing angle of incidence of 30°.
Freeze-fracture of cell nuclei for high-resolution SEM and deep-etch tem
Authors: Haggis G.H.
Published: June 2020

The results reported in this paper form a direct extension of the work of Heuser and Kirschner. These authors permeabilized cultured fibroblasts with Triton X-100 prior to rapid freezing, freeze-drying and rotary platinum coating for TEM viewing. We have permeabi1ized 3T3 cells in a stabilization buffer similar to that used by Heuser and Kirschner, rapidly frozen and fractured the permeabilized cells, rotary coated the preparations with platinum after both deep etching and critical-point drying and viewed them by both TEM and high-resolution SEM. By fracturing the cells we obtain an internal view of the nucleus as well as of the cytoplasm.

The 3T3 cells were cultured on a film of fibrin 20 μm thick (for reasons described below). The cells were permeabi1ized at room temperature for 15 min with 0.5% Triton X-100 in Bershadsky buffer (50 mM imidazole 50 mM KC1, 0.5 mM MgCl2, 1 mM EGTA, 0.1 mM EDTA, 1 mM mercaptoethanol, 4M glycerol at pH 6.7).
Quantitative ultrastructural reconstruction of small regions within large volumes by correlative light and high voltage electron microscopy of serial 0.25-0.50 μm sections
Authors: Rieder Conly L. , Miller Frederick J. , Davison Edwin , Bowser Samuel S. , Lewis Kirsten , Sluder Greenfield
Published: June 2020

In this abstract we Illustrate how same-section correlative light and high voltage electron microscopy (HVEM) of serial 0.25-0.50-μm sections can answer questions which are difficult to approach by EM of 60-100 nm sections.

Starfish (Pisaster and Asterlas) eggs are fertilized at meiosis I when the oocyte contains two maternal centrosomes (e.g., asters) which form the poles of the first meiotic spindle. Immediately after fertilization a sperm aster is assembled in the vicinity of the male pronucleus and persists throughout meiosis. At syngamy the sperm aster splits to form the poles of the first mitotic spindle. During this time the functional and replicative properties of the maternal centrosome, inherited from the last meiotic division, are lost. The basis for this differential stability, of male and female centrosomes in the same cytoplasm, is a mystery.
High-voltage electron microscopic study in the syndrome of myalgia and cramps
Authors: Song M.J. , Lazaro R.P. , Principe L. , Parsons D.F.
Published: June 2020

Muscle pain and cramps are neuromuscular symptoms of diverse etiology. When these symptoms are associated with exercise, a biochemical defect in glycolytic or lipid metabolism, a mitochondrial myopathy, or defect in muscle contraction is frequently suspected. Diagnosis is usually established when such defect is demonstrated histochemically or by NMR. In some neuromuscular disorders, these symptoms may not necessarily be induced by exercise and they are usually part of a wide constellation of symptoms. Some of them are distinct enough to be recognized clinically or electrophysiologically, as in peripheral neuropathies, myotonias, or syndromes of continuous muscle activity. However, despite modern histochemical techniques, a number of muscle disorders remain, characterized primarily by muscle pain and cramps, where light microscopy or electrophysiologic studies show either normal or nonspecific findings.
Correlative ultrastructure and immunocytochemistry in small round cell tumors of childhood
Authors: Tsokos M. , Triche T.J.
Published: June 2020

Conventional methods of pathologic evaluation of the undifferentiated solid tumors of childhood, often referred to as “small round cell tumors”, have been notoriously unreliable. Prior to the advent of effective therapy, this was of little consequence. Current treatment methods require precise categorization of these tumors, as tumor response shows wide variation, especially when inappropriate chemotherapeutic agents or radiation therapy are employed. The combination of transmission electron microscopy (TEM) and correlative immunocytochemistry (ICC) has proved to be a powerful tool in deriving precise diagnoses.

The common small round cell tumors of childhood include sarcomas (especially undifferentiated rhabdomyosarcoma), lymphomas (especially lymphoblastic and large cell), neural tumors (neuroblastoma and a variety of apparently related neoplasms), and particularly Ewing's sarcoma, an enigmatic tumor of inapparent histogenesis with which all the above are compared. The treatment and prognosis of each of these groups is quite different, and we have attempted to reliably distinguish each from the other by ultrastructural and immunocytochemical criteria.
200kv superconducting cryo electron microscope
Authors: Iwatsuki M. , Kokubo Y. , Harada Y. , Lehman J.
Published: June 2020

In recent years, the electron microscope has been significantly improved in resolution and we can obtain routinely atomic-level high resolution images without any special skill. With this improvement, the structure analysis of organic materials has become one of the interesting targets in the biological and polymer crystal fields.

Up to now, X-ray structure analysis has been mainly used for such materials. With this method, however, great effort and a long time are required for specimen preparation because of the need for larger crystals. This method can analyze average crystal structure but is insufficient for interpreting it on the atomic or molecular level. The electron microscopic method for organic materials has not only the advantage of specimen preparation but also the capability of providing various information from extremely small specimen regions, using strong interactions between electrons and the substance. On the other hand, however, this strong interaction has a big disadvantage in high radiation damage.
Imaging of the crotoxin crystal in vitreous ice at 3.9 Å resolution
Authors: Degn L. L.
Published: June 2020

The crotoxin complex is a 24,500 dalton neurotoxic protein isolated from the venom of the Brazilian rattlesnake Crotalus durissus terrificus. The crotoxin complex crystallizes as thin crystals suitable for high resolution 3-D reconstruction by electron crystallographic analysis. High resolution imaging of an untilted crotoxin complex crystal embedded in glucose has been reported. Presented here is high resolution (3.9 Å) imaging of an untilted crotoxin complex crystal embedded in vitreous ice.

Several technical problems are involved in the collection of high resolution electron crystallographic data for 3-D reconstruction. First, the specimen should be as flat as possible on the grid since bending due to specimen preparation or due to beam-induced movement may cause smeared reflections in electron diffraction patterns or optical diffractograms, a phenomenon that is particularly noticeable in highly tilted specimens.
The Three-dimensional structure of frozen-hydrated nudaurelia capensis β virus
Authors: Olson N. H. , Baker T. S. , Mu Wu Bo , Johnson J. E. , Hendry D. A.
Published: June 2020

Nudaurelia capensis β virus (NβV) is an RNA virus of the South African Pine Emperor moth, Nudaurelia cytherea capensis (Lepidoptera: Saturniidae). The NβV capsid is a T = 4 icosahedron that contains 60T = 240 subunits of the coat protein (Mr = 61,000). A three-dimensional reconstruction of the NβV capsid was previously computed from visions embedded in negative stain suspended over holes in a carbon film. We have re-examined the three-dimensional structure of NβV, using cryo-microscopy to examine the native, unstained structure of the virion and to provide a initial phasing model for high-resolution x-ray crystallographic studies

NβV was purified and prepared for cryo-microscopy as described. Micrographs were recorded ∼1 - 2 μm underfocus at a magnification of 49,000X with a total electron dose of about 1800 e-/nm2.
Measurement of water content in hydrated cryosections by EELS
Authors: Leapman R.D. , Ornberg R.L.
Published: June 2020

Determination of cellular organelle water content is important in understanding cell volume regulation and also for converting x-ray microanalytical measurements of diffusible ions and elements from dry mass concentration to the biologically more relevant aqueous concentration. It has been proposed that electron energy loss spectroscopy (EELS) can be used to measure mass thickness in frozen hydrated and dehydrated cryosections at low electron dose, and that the method should thus provide a direct estimate of water content. Potentially the EELS inelastic scattering method has a number of advantages over alternative approaches. For example use of the x-ray continuum to measure mass requires much higher doses and cannot be applied at resolutions of 100nm to hydrated samples. Moreover, hydrated cryosections are often too thick to utilize dark field STEM imaging for mass measurement.
Analytical Electron Microscopy in human pathology
Authors: Shelburne J.D. , Ingram P.
Published: June 2020

Analytical electron microscopy and related microprobe techniques such as ion microscopy and laser microscopy have been widely used in scientific investigations of many types. This presentation will review the rapidly expanding body of scientific literature on the application of microprobe techniques solely to problems in human pathology. With this goal in mind the presentation will focus on studies that demonstrate potential for microchemical microscopy in diagnostic and clinical pathology, and not on studies that are primarily research oriented.

Also, it is not the purpose of this presentation to discuss articles primarily devoted to secondary electron imaging - the emphasis is on analytical, not morphological, techniques. A review of sample preparation techniques applicable to the analytical study of human tissue is included, as is also a brief discussion of possible artifacts from these techniques.
STEM/EDS microanalysis of smoker lungs and ferruginous bodies
Authors: Lloyd J. K. , Harris J. H. , Nichols N. T.
Published: June 2020

Previous studies have used digestion techniques with SEM/EDS to identify foreign material in lungs, These studies have identified elements with inclusions of lung tissue exposed to cigarette smoke, and clinical cases having ferruginous bodies. We have established a protocol to examine fixed lung tissue using x-ray microanalysis with STEM. Our technique allowed both localization and elemental analysis of foreign material in tissue. In the present study lung tissue from cigarette smokers and bronchial washings containing ferruginous bodies were examined.

Histological slides of smoker lung tissue were examined to locate dark granular inclusions in cells and the interstitium. Cytology cell block slides of bronchial washings depicting ferruginous bodies were also selected. After locating these granules and bodies, tissues were carefully removed from the paraffin blocks, deparaffinized, and embedded in Spurr. Sections ranging in thickness from 180nm - 500nm were cut with a diamond knife and collected on nylon grids.
X-Ray microanalytical demonstration of osteogenesis after hydroxylapatite/plaster frontal sinus cranioplasty in cats
Authors: Giammara B. , Rawlings C. , Ovelmen-Levitt J. , Wilkins R. , Georgiade N. , Hanker J.
Published: June 2020

The repair of cranial defects with methyl methacrylate is generally successful with the exception of the frontal sinus where infection is a problem due to the connection of the sinus with the nasal cavity.

Composite hydroxylapatite/plaster implants have been used successfully for various jawbone defects in many experimental animals and patients. The plaster prevents the scatter of the hydroxylapatite (HA) particles during, and migration after, the implantation procedure. It also facilitates tailoring of the implant to fit the defect. The plaster is resorbed in a period of weeks and replaced at the same rate by infiltrating fibrovascular tissue which maintains the shape and integrity of the implant. Postoperative infection is rare, and then limited almost exclusively to cases where it had been observed preoperatively. It was, therefore, of interest to study HA/plaster for frontal sinus cranioplasty in cats.
Segregated versus overlapping glycinergic and gabaergic afferent systems at a vertebrate identified neuron
Authors: Triller A. , Seitanidou T. , Cluzeaud F. , Korn H.
Published: June 2020

The excitability of the Mauthner cell (MC), which is directly responsible for the escape reflex of the goldfish is controlled by a powerful inhibition (ref. in 1). As other neurons of the CNS, the cell's membrane is sensitive to both GABA and glycine which activate chloride conductances and have been further characterized on the basis of previous reports. One of the most striking feature of this neuron's innervation appears to be the segregation of the diverse types of terminals at its surface, and correspondingly of iontophoretically activated GABA and glycine receptors. However, immunocytochemical techniques required to explore in a more detailed manner the structural organization of inhibitory connections, have revealed that the respective distribution of glycinergic and GABAergic innervation is somewhat more complex than previously assumed, and that furthermore, some terminals containing GABA can be apposed to receptors for glycine in specific regions of the cell.
Scanning Electron Microscopy of ischemic intestinal mucosa
Authors: Millard Ron W. , Nakajima Y. , Ashraf M.
Published: June 2020

The small intestinal mucosa is known to be sensitive to ischemia. The early changes which are critical to the eventual cellular viability upon restoration of blood flow or other therapeutic intervention have not been investigated thoroughly. This investigation describes the surface alterations of the villous cells in the dog's small intestine. Jejunal segments of 14 anesthetized dogs were subjected to the arterial occlusion for 5, 15, 30, 45, and 60 minutes. At the end of the occlusion period, tissue samples from normal non-ischemic and ischemic (I) zones were fixed in 2.5% glutaraldehyde made in 0.17 M cacodylate buffer, pH 7.4, for four hours, rinsed in the buffer, and dehydrated in a graded series of ethanol. Finally, they were critically point-dried and coated with gold-palladium (60:40) for examination in the ETEC scanning electron microscope.
Two distinct negative staining patterns of halobacterium cell envelopes
Authors: Kessel Martin , Loren Buhle E. , Cohen Simone , Aebi Ueli
Published: June 2020

The cell walls of Halobacteria are comprised of a 200,000MW sulphated glycoprotein, and by shadow casting are seen as a periodic hexagonal lattice of morphological units with a center to center spacing of approximately 140A. Preparations ot virtually salt tree envelopes from Halobacterium volcanii isolated from the Dead Sea, obtained by freezing and thawing the cells and suspension in 10mM CaCl2, have enabled high resolution analysis of the wall morphological units by negative staining.

Envelopes of H. volcanii negatively stained with 1% uranyl acetate or 0.75% uranyl formate both at pH 4.5, have consistently resulted in two different images irrespective ot the stain used: a more prevalent “honeycomb” appearance of strong stain accumulating centers surrounded by regions ot stain exclusion (fig. 1 and fig. 3B); and a less common “true” negative staining with stain excluding rings (morphological units) and their stain accumulating centers lying in pools ot stain (Fig. 2 and 3A).
Application of cross correlation to HREM images of surfaces
Authors: Luzzi D. E. , Marks L. D. , Buckett M. I.
Published: June 2020

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.

We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.
Potential use of Si-labeled colloidal gold for localization of F-actin
Authors: Bozzola J. J. , Peterson R. N. , Kamaph U. , Russell L. , Shriver J.
Published: June 2020

Filamentous actin has been localized in numerous plant and animal species using various immunocytochemical procedures as well as a decoration technique using myosin subfragment 1 (SI). In the latter case, the long F-actin strands appear as herringbones with stacked arrowheads of SI pointing in the same direction. Unfortunately, when the actin filaments occur as shorter oligomers, it may be difficult to discern this pattern against a complex background. Using immunocytochemical procedures, variabilities in labeling patterns encountered may be attributed to the use of polyclonal antibodies or to antibody specificities for various subclasses of actin. In an attempt to localize short segments of F-actin without the use of antibodies, we labeled colloidal gold particles with purified SI.

In order to evaluate the efficacy of this procedure, purified SI and partially purified F-actin were obtained from rabbit skeletal muscle.
New membrane assembly during exocytosis
Authors: Schmauder-Chock Elsa A. , Chock Stephen P.
Published: June 2020

A rapid membrane assembly process has been postulated as an early step in the mechanism of mast cell granule exocytosis. This theory explains how an activated granule can rapidly enlarge prior to contact and fusion with the plasma membrane. Some evidence supporting this theory includes experiments which showed the ability of the purified granule to generate new membrane in an aqueous environment after removal of its perigranular membrane (PGM). The formation and the fusion of these newly assembled membrane vesicles with the PGM has also been observed in mast cells stimulated with saponin. Under physiological conditions, histamine release is triggered by antigen-specific crosslinking of receptor-bound IgE antibodies on the plasma membrane. Thus it is important to see if the process of de novo membrane generation also occurs in this IgE-receptor mediated exocytosis.
Immunogold and immunoblot studies on a cell surface protein found in primary mesenchyme cells and in the cortical secretory vesicles of the sea urchin egg
Authors: Decker G.L. , Valdizan M.C.
Published: June 2020

A monoclonal antibody designated MAb 1223 has been used to show that primary mesenchyme cells of the sea urchin embryo express a 130-kDa cell surface protein that may be directly involved in Ca2+ uptake required for growth of skeletal spicules. Other studies from this laboratory have shown that the 1223 antigen, although in relatively low abundance, is also expressed on the cell surfaces of unfertilized eggs and on the majority of blastomeres formed prior to differentiation of the primary mesenchyme cells.

We have studied the distribution of 1223 antigen in S. purpuratus eggs and embryos and in isolated egg cell surface complexes that contain the cortical secretory vesicles. Specimens were fixed in 1.0% paraformaldehyde and 1.0% glutaraldehyde and embedded in Lowicryl K4M as previously reported. Colloidal gold (8nm diameter) was prepared by the method of Mulpfordt.
Ultrastructure of giant cell tumor of the lung
Authors: Sun C.N.
Published: June 2020

Multinucleated giant cells resembling osteoblasts seen in giant-cell tumors of bone have been described in the thyroid gland, and pancreas. However, a giant cell tumor of the lung with osteoblast-like cells is rare. The present report will describe ultrastructural aspects and histiogenesis of this type of lung tumor.

A 58-year old white male patient was noted by chest x-ray to have a mass in the right lower lobe of the lung. Segmental resection of the superior segment was performed revealing a nodular neoplastic lesion of 3.5 cm in diameter located 4.3 cm from the bronchial resection margin. For EM preparation, the tissue samples were immediately fixed in 4 percent phosphate-buffered glutaraldehyde and postfixed 1 hr with 1 percent osmium tetroxide in phosphate buffer (pH 7.2), dehydrated in ethanol and embedded in Epon 812. The tumor presented a sheet-like growth pattern without evidence of encapsulation.