bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution transmission electron microscopy: A structural and chemical probe of semiconductor systems
Authors: Ourmazd A.
Published: June 2020

High Resolution Transmission Electron Microscopy (HRTEM) is now a powerful probe for the structural analysis of semiconductor systems. Lattice images can be obtained in a number of orientations, in at least three of which the individual atomic columns can be resolved. However, there exits an important class of problems, whose resolution requires chemical as well as structural information. The identification of individual atomic columns in compound semiconductors, and the atomic configuration of semiconductor/semiconductor interfaces are two important examples.

In general, most reflection used to form a lattice image are not particularly sensitive to chemical changes in the sample. The information content of a typical lattice image is therefore strongly dominated by structural details. On the other hand, reflections such as the (200), which are normally forbidden in the diamond structure, come about in the zinc-blende system because of the chemical differences between the occupants of the two sublattices, and are thus highly chemically sensitive. In the “kinematical” thickness region, where simple image interpretation is possible, such reflections are relatively weak and their contribution to the lattice image is dominated by the stronger and chemically insensitive, allowed reflections.
Coprecipitation of barium sulfate and barium carbonate at 80°C
Authors: Takiyama K.
Published: June 2020

The coprecipitation of two sparingly soluble compounds in the aqueous solution has been studied by means of electron microscopy and x-ray diffraction techniques, and the properties of the particles produced by the coprecipitation were discussed as an issue in crystal chemistry. In the present investigation the coprecipitation of barium sulfate and barium carbonate was studied. Both crystals belong to the orthorhombic system. The lattice constants of barium sulfate are ao=8.878, bo=5.450 and co=7.152 Å. Those of barium carbonate are ao=5.314, bo=8.902 and co=6.430 Å. The ratio of the lattice constants of barium sulfate is different from that of barium carbonate. In this investigation, the relation of the morphological properties of the particles with the crystallographic properties of the component compounds was discussed. As the particles became very small when the precipitation was carried out at room temperature, in the present investigation the coprecipitation was done at 80°C to produce larger particles to study the morphological properties of the particles.
The usefulness of high index low symmetry zone axes for holz line analysis
Authors: Sung C. M. , Williams D. B.
Published: June 2020

Researchers have tended to use high symmetry zone axes (e.g. <111> <114>) for High Order Laue Zone (HOLZ) line analysis since Jones et al reported the origin of HOLZ lines and described some of their applications. But it is not always easy to find HOLZ lines from a specific high symmetry zone axis during microscope operation, especially from second phases on a scale of tens of nanometers. Therefore it would be very convenient if we can use HOLZ lines from low symmetry zone axes and simulate these patterns in order to measure lattice parameter changes through HOLZ line shifts. HOLZ patterns of high index low symmetry zone axes are shown in Fig. 1, which were obtained from pure Al at -186°C using a double tilt cooling holder. Their corresponding simulated HOLZ line patterns are shown along with ten other low symmetry orientations in Fig. 2. The simulations were based upon kinematical diffraction conditions.
The core cylinder of the JSR of frog skeletal muscle in cryosections
Authors: Sommer J. R. , High T. , Ingram P.
Published: June 2020

Electron-lucent regions in the junctional sarcoplasmic reticulum (JSR) were first observed in frog skeletal muscle treated with ruthenium red and other exotic cations. Next, they were pointed out in Epon sections of freeze-substituted muscle following quick-freezing both in the presence and absence of cryoartifacts. Whereas their nature and function remain obscure, the so-called “core cylinders” (CCs) are now considered invariant components of the normal anatomy of frog skeletal muscle JSR.

Following quick-freezing, part of the single intact frog skeletal muscle fiber was freeze-substituted, embedded in Epon and sectioned (Fig. 1). Cryosections were cut from an immediately adjacent fiber region with a diamond knife specially mounted for that purpose with two free edges (courtesy Diatome-US), on a Reichert Ultracut FC-4D at -150°C, put on the carbon film on 100 mesh nickel grids, freeze-dried in a Balzers FDU 010 fitted with a turbomolecular pump (vac 10-6 torr) against a liquid N2 trap (geometry 14 mm) for 15 hrs with 3 temperature steps, each 3 hrs apart, at -100, -85, and -50°C, respectively (Fig. 2).
SEM of polymer materials
Authors: Sawyer Linda C.
Published: June 2020

Scanning electron microscopy (SEM) has become an analytical tool widely used in universities, industrial laboratories and modern plants in applications ranging from fundamental research and applied research to quality control. The SEM provides important and insightful observations, in the form of three dimensional images of bulk materials and surfaces, which provide input to conduct process-structure-properties studies of polymer materials. SEM analysis requires knowledge of the instruments, image formation and specimen preparation methods.

Consideration must be given to the interaction of the electron beam with the specimen, image formation and the effect of the electron beam on the specimen, e.g. beam damage. Scanning electron microscopy has been described and SEM of polymers has been reviewed. The essential feature of a scanning microscope is that the image is formed point by point, by scanning a probe across the specimen. The probe of an SEM is a focused electron beam and a detected signal is displayed as a TV type image.
Relationships between hierarchical structure and properties in macromolecular systems
Authors: Baer E.
Published: June 2020

The most advanced macromolecular materials are found in plants and animals, and certainly the connective tissues in mammals are amongst the most advanced macromolecular composites known to mankind. The efficient use of collagen, a fibrous protein, in the design of both soft and hard connective tissues is worthy of comment. Very crudely, in bone collagen serves as a highly efficient binder for the inorganic hydroxyappatite which stiffens the structure. The interactions between the organic fiber of collagen and the inorganic material seem to occur at the nano (scale) level of organization. Epitatic crystallization of the inorganic phase on the fibers has been reported to give a highly anisotropic, stress responsive, structure. Soft connective tissues also have sophisticated oriented hierarchical structures. The collagen fibers are “glued” together by a highly hydrated gel-like proteoglycan matrix. One of the simplest structures of this type is tendon which functions primarily in uniaxial tension as a reinforced elastomeric cable between muscle and bone.
Structure and properties of crystalline polymer fibers
Authors: Grubb D. T.
Published: June 2020

Most polymer fibers studied by TEM have been semi-crystalline or more recently liquid crystalline, both because the majority of technically interesting fibers are ordered and because scientific interest lies in the polymer morphology. The obvious common feature of fibers is that they are "fibrous" that is to say, they have long and narrow features aligned along the fiber direction. The basic unit obtained by a very local deformation of a crystal is called a micro-fibri l . [1,2] Fibrils may or may not be clear in the TEM, either because the structure itself is not well defined or because of superposition of several small fibrils within the sample.

The large plastic deformation in fiber drawing will make any heterogeneity in the material appear fibrous. While zone drawing gels of poly(vinyl alcohol) recently we obtained porous fibers when residual ethylene glycol solvent boiled at just below the draw temperature.
A priori crystal structure analysis: layer structure
Authors: Scaringe Raymond P.
Published: June 2020

Advances in the theoretical prediction of molecular structure based on molecular mechanics and in the calculation of the lattice energy of molecular crystals with the use of atom-atom potentials have prompted us to examine the problem of a priori crystal structure analysis (i.e., the prediction of crystal structure without the use of diffraction data). A practical solution to this problem would not only represent a significant new tool for theoretical crystallography, but would also open the way to the rational design of molecular solids with engineered structural properties. Potential applications in the areas of solid-state chemistry, optics, and electronics are numerous. In this paper we will describe a complete model for predicting the structure of a 2-dimensional crystal (i.e., a layer). Although the prediction of layer structure is important as a preamble to treating the full 3-dimensional case, molecular layers are also of intrinsic interest.
Applications Of TEM and image analysis in impact-modified thermoplastics
Authors: Chen R.T.
Published: June 2020

Polymers can be blended to produce improved properties appropriate for a wide range of applications. For example, rubbers when added to rigid thermoplastic polymers produce blends with improved impact properties. Generally, the properties of blends are dictated by phase morphology, which can be controlled by processing conditions and chemical composition.

This study demonstrates that TEM/image analysis can be used to study deformation of dispersed rubber particles in a matrix and to quantify phase morphologies for process optimization. For TEM, ultrathin specimens were produced by microtomy and stained with heavy atoms to enhance contrast between the different phases. In the present examples, thin film samples were embedded in epoxy and sectioned on a LKB Ultramicrotome. For bulk samples, cryogenic thin sectioning was performed using a Reichert Cryo Ultramicrotome. The thin cross-sections were then vapor stained with OsO4. and carbon coated. Electron microscopy was performed on a JEOL 100CX TEM.
Electron beam range effects in SEM/EDX: Application to scratch-testing of coated carbides
Authors: Hefter J.
Published: June 2020

The use of protective coatings to enhance the chemical and mechanical properties of materials is widely practiced in industry. For example, in cutting tool technology, the use of strongly adhering, specialized coatings has expanded the lifetime and performance of cutting tools. The most widely used technique for checking coating adherence is the scratch-test. Investigation of the scratch regions by SEM via both electron and x-ray imaging may assist in the determination of the failure mode region, i.e., within the coating, at an interface, or within the substrate.

As an example of this approach, a cemented carbide was coated first with TiC (6 μm) and then with Al2O3 (2 μm). A scratch-test was carried out and the sample was analyzed using the JEOL JSM-840 analytical SEM at an electron beam energy of 20 keV. All secondary electron (grayscale) and x-ray images (256x256x8 pixel resolution) were taken using digital imaging hardware on a Tracor Northern TN-5500 system.
Chromatic aberration and low-voltage SEM
Authors: Shao Zhifeng , Crewe A.V.
Published: June 2020

For scanning electron microscopes, it is plausible that by lowering the primary electron energy, one can decrease the volume of interaction and improve resolution. As shown by Crewe /1/, at V0 =5kV a 10Å resolution (including non-local effects) is possible. To achieve this, we would need a probe size about 5Å. However, at low voltages, the chromatic aberration becomes the major concern even for field emission sources. In this case, δV/V = 0.1 V/5kV = 2x10-5. As a rough estimate, it has been shown that /2/ the chromatic aberration δC should be less than ⅓ of δ0 the probe size determined by diffraction and spherical aberration in order to neglect its effect. But this did not take into account the distribution of electron energy. We will show that by using a wave optical treatment, the tolerance on the chromatic aberration is much larger than we expected.
Three-dimensional reconstruction of cell morphology using intermediate voltage electron microscopy and computer graphics
Authors: Heath Julian P. , Ho Ming Hsiu , Peachey Lee D.
Published: June 2020

The Intermediate Voltage Electron Microscopy and Biomedical Image Analysis facility at the University of Pennsylvania is a National Resource supported by NIH and provides users with facilities for transmission electron microscopy and digital image processing. The facility comprises a JEOL 4000EX transmission electron microscope with a 360 degree goniometer specimen holder, a VAX 11/750 computer, and a Raster Technologies Inc. Model One/380 Graphics work station with two high resolution 1280x1024 pixel color video display monitors for stereoscopic display. We are using this facility to examine the morphology of fibroblasts migrating through fibrillar collagen gels: these matrices closely model the environments encountered by migratory cells during embryonic morphogenesis.

The identification and three dimensional localization of structures in stereoscopic electron micrographs of thick sections of cells can be hampered by diffuse boundaries and by the superposition of details with similar electron density.
Electron microscopy in the community hospital
Authors: Pearl Gary S.
Published: June 2020

A common misconception exists that a diagnostic electron microscopy laboratory can not succeed fiscally in a community hospital. This has not been the case in our institution. An electron microscopy laboratory was established in 1982 and the initial investment by the hospital was recovered within four years. Billings have remained relatively constant during the past several years. In addition to financial considerations, the laboratory has been beneficial diagnostically, allowing for rapid, easy access to this valuable tool. In fact, the presence of an electron microscope in the hospital has probably encouraged further utilization of this technology. The electron microscopy laboratory has also been an asset in our teaching program, not only for the demonstration of the ultrastructural findings themselves, but also for the consultative material sent from other institutions. Finally, the laboratory has opened up research possibilities not otherwise available.
The fine structure of dementing illness: Alzheimer's disease and AIDS
Authors: Mirra S. S. , Miles M. L. , del Rio C. , Ellisman M. H.
Published: June 2020

Electron microscopy has made important contributions to our understanding of dementing illnesses. The fine structure of neurofibrillary tangles and neuritic plaques, the pathologic hallmarks of Alzheimer's disease, was first described in the early 1960's. Yet, the nature of paired helical filaments, constituents of neurofibrillary tangles and some plaque neurites, has remained an enigma. Recent studies indicate that a major component of paired helical filaments is an atypically phosphorylated form of the microtubule-associated protein, tau. The finding of tau, normally an axonal protein, within neurofibrillary tangles of cell body and apical dendrite suggests that abnormalities in segregation and modification of this microtubule-associated protein may be defective in Alzheimer's disease.

The availability of brain biopsy specimens from five cases of neuropathologically confirmed Alzheimer's disease provided the opportunity for study of well-preserved tissue. Thin and thick sections (0.25-0.75 um) viewed on conventional and high voltage electron microscopes revealed sidearms or extensions projecting at irregular intervals along the paired helical filaments.
Postsynaptic neuronal geometry and synaptic effectiveness
Authors: Wilson C.J.
Published: June 2020

Most central nervous system neurons receive synaptic input from hundreds or thousands of other neurons, and the computational function of such neurons results from the interactions of inputs on a large and complex scale. In most situations that have yielded to a partial analysis, the synaptic inputs to a neuron are not alike in function, but rather belong to distinct categories that differ qualitatively in the nature of their effect on the postsynaptic cell, and quantitatively in the strength of their influence. Many factors have been demonstrated to contribute to synaptic function, but one of the simplest and best known of these is the geometry of the postsynaptic neuron. The fundamental nature of the relationship between neuronal shape and synaptic effectiveness was established on theoretical grounds prior to its experimental verification.
Ultrastructural effects of acute exposure of diethylnitrosamine to hepatic tissue of medaka, Oryzias latipes
Authors: Norton W.N. , Gardner H.S.
Published: June 2020

Recent interest has been expressed in the phenomenon of tumor initiation and development in poikilothermic animals. A number of fish model systems have demonstrated sensitivity to a variety of known carcinogens. The medaka Oryzias latipes, a small aquarium fish native to Japan, represents one of the model systems which has been employed frequently in carcinogenicity studies. The primary objective of this investigation was to determine the ultrastructural manifestations of acute exposure of the carcinogen diethylnitrosamine to hepatic tissue of medaka. Diethylnitrosamine is aproven hepatic carcinogen for several species of small fish including medaka.

A group of 14 day old fry was selected from a stock population and exposed to diethylnitrosamine at a concentration of 200 mg/L for 48 hours. The fish were rinsed and held in clean water at 25°C. An additional group of fry was maintained at 25°C in a tank of tap water and functioned as a control.
Acetaminophen: Neonatal hepatotoxicity due to late pregnancy exposure
Authors: Miranda G.A. , Arroyo M.A. , Lucio C.A. , Mongeotti M. , Poolsawat S.S.
Published: June 2020

Exposure to drugs and toxic chemicals, during late pregnancy, is a common occurrence in childbearing women. Some studies have reported that more than 90% of pregnant women use at least 1 prescription; of this, 60% used more than one. Another study indicated that 80% of the consumed drugs were not prescribed, and of this figure, 95% were “over-the-counter” drugs. Acetaminophen, the safest of all over-the-counter drugs, has been reported to induce fetal liver necrosis in man and animals and to have abortifacient and embryocidal action in mice. This study examines the degree to which acetaminophen affects the neonatal liver and kidney, when a fatty diet is simultaneously fed to the mother during late pregnancy.

Timed Swiss Webster female mice were gavaged during late pregnancy (days 16-19) with fat suspended acetaminophen at a high dose, HD = 84.50 mg/kg, and a low dose, LD = 42.25 mg/kg; a control group received fat alone.
Structural analysis of sickle hemoglobin fibers
Authors: Bluemke David A. , Carragher Bridget , Gabriel Barbara , Potel Michael J. , Josephs Robert
Published: June 2020

We have used helical reconstruction and electron density modeling techniques in our analysis of the structure of sickle hemoglobin (HbS) fibers. The formation of HbS fibers in red blood cells under conditions of deoxygenation is responsible for the clinical manifestations of sickle cell disease. Fibers have a helical pitch of about 2700 Å and an average diameter of about 210 Å. The subunit of structure in fibers consists of two half-staggered strands of HbS molecules termed double strands. Double strands in fibers are oriented such that the axis of the constituent double strands is nearly parallel to the particle axis, as indicated by the optical diffraction pattern of these particles.

The pitch of fibers varies from particle to particle, as well as within a single fiber, and this presents special problems in the structural analysis. We have measured the distances corresponding to 180° of rotation in 245 fibers.
Correlation analysis of structure images
Authors: Buckett M. I. , Marks L. D. , Luzzi D. E.
Published: June 2020

A typical high resolution structure image contains a large amount of intensity information which is masked by both statistical and amorphous noise. One useful method of quantifying such images is to employ correlation techniques. When one seeks to quantify the atom column positions, correlation techniques can be used to decompose the image into separate motifs (of specific peak amplitudes and positions - each motif corresponding to a single column of atoms), thereby reducing the data to a more manageable form.

This problem can be considered as the least squares minimization of the function:

where I(r) is the image, and m(r) is the motif, and the unknowns are the positions, rj, of the motifs and their peak heights, αj. The standard approach is to look for peaks in the cross-correlation (equation 2) between the motif and image, to determine rj and αj
Stereological analysis of partially amorphous HREM images
Authors: Kaspi R. H. , Luzzi D. E.
Published: June 2020

The HREM is highly sensitive to the presence of crystals in a specimen. As a results, researchers often report the presence of some fringe contrast in an otherwise amorphous image. The potential for obtaining more information than just a sense of the presence of crystal has not been addressed in detail. In the interest of allowing some amount of quantitative analysis of HREM images of partially and fully amorphous materials, we have developed an analytical method with which to quantify the directionality of an image using stereology.

Figure 1 is a series of HREM images taken through the crystal - amorphous interface of an electron irradiated Cu-Ti intermetallic alloy. The first image is from an unirradiated crystalline region. The second image is from a low dose irradiated region, while the third is from a region that has been irradiated to a dose just under the necessary dosage for a total amorphous transition.
Chemoselective cluster labelling of biomolecules
Authors: Foley C. J. , Maelia L. E. , Hainfeld J. F. , Wall J. S.
Published: June 2020

The Brookhaven STEM is capable of visualizing single heavy atoms at a beam dose of >103 el/Å2. Heteropolytungstate clusters, including W12PO403, have been found to incorporate several desirable properties as labels for biological specimens. They may be resolved at much lower beam doses due to their high concentrations of multiple heavy atoms and are directly visible labels. A lower beam dose also helps to preserve the biological structure of the specimens. Furthermore, they are extremely stable in the electron beam. Lastly, they are capable of being derivatized as chemoselective reagents for specific binding sites on biomolecules, as in the previously reported undecagold compound.

Two new classes of heavy atom labels, one specific for sulfhydryl and the other specific for both amino and sulfhydryl binding sites on proteins, have been synthesized by reactions analogous to those illustrated in Scheme 1.
Correlative light and high-voltage electron microscopy of primary (9 + 0) cilia in cultured kidney epithelial cells
Authors: Roth K. E. , Davison E. A. , Myers N. , Rieder C. L. , Bowser S. S.
Published: June 2020

With few exceptions, a single primary cllium is associated with virtually all vertebrate cell types. These cilia are often located adjacent to the nucleus and possess a 9+0 axonemal microtubule pattern which is generated by the “eldest” or “parent” centriole. Despite their ubiquity, the in vivo properties of primary cilia are largely unknown, primarily because their orientation perpendicular to the dorsal cell surface (and parallel to the optical axis) makes them difficult to observe by LM. To circumvent this problem, we have developed novel methods for imaging primary cilia in vivo and for examining selected cilia at the EM level.

Kidney epithelial cells (PtK, MDCK, BSC) are grown to confluency on 22 x 40mm solvent-cast Formvar films (0.5 μm thick). A side view of the mono-layer is obtained by folding the film, cell-side out, and sandwiching it in a simple coverslip chamber.
Anatomy and ultrastructure of Colocasia esculenta (L.) Schott (Araceae)
Authors: Stein B. D. , Strauss M. S.
Published: June 2020

Taro, Colocasia esculenta (L.) Schott (Araceae), is a staple crop grown in much of the tropics and subtropics. The plant consists of an underground stem, the corm, which is the harvestable portion, and aerial leaves. Most production is by subsistance farmers and the plant is an important part of the culture of these people.

Only a few studies have been done on the plant and its anatomy. In addition, much of the previous work on monocot anatomy has been done on the Poaceae. To establish a baseline for non-symptomatic plants for the study of diseases and physiology of taro and to expand the knowledge of the anatomy of monocotyledons, taro was examined ultrastructurally.

Leaf tissues for TEM were fixed in glutaraldehyde, postfixed in osmium tetroxide, dehydrated in acetone, infiltrated and embedded in Spurr's epoxy. Blocks were sectioned on a LKB Ultramicrotome III.
Ultrastructure and peroxidase activity of alveolar macrophages in cystic fibrosis
Authors: Garlich D. J. , Clawson C. C. , Elliott G. R.
Published: June 2020

Alveolar macrophages (AMs) and polymorphonuclear leukocytes (PMNs) are the two host defense cells responsible for bacterial clearance in infected lungs. In cystic fibrosis (CF), with its accompanying pulmonary infection, these cells are unable to rid the lung of invading bacteria. This has raised doubts about CF-AMs’ phagocytic ability and metabolism. Their in vivo morphology has had little attention, but a commonly held belief is that the CF-AM ultrastructure is essentiaIly normal and that these cells have not been phagocytically active. The present morphologic study was undertaken for evidence of ingestion by the CF-AM. Cytochemical staining for myeloperoxidase (MPO) was performed to aid in determining the cause for increased luminol-dependent chemiluminescence by the CF-AM, when stimulated by phorbol myristate acetate.

Fiberoptic broncho-alveolar lavage was performed on 12 CF patients and 17 normal healthy volunteers.
Statistical geometric analysis of packing of paired helical filaments in neurofibrillary tangles of Alzheimer's disease
Authors: Clapin D. F. , Montpetit V.J.A.
Published: June 2020

The tangles of abnormal fibers known as paired helical filaments (PHF), which occur in neurons of persons suffering from Alzheimer's disease, possess limited regions of quasi-crystalline ordering interspersed with regions of randomly oriented fibers. Analysis of the quasi-crystalline zones of tangles, as visualized in longitudinal orientation in thin sections, indicated that a paracrystalline order may characterize the packing of PHF in tangles. Para-crystals may be defined as structures in which each pair of molecules is associated with uniquely spaced positions with a low probability that the molecules occupy these positions. In a paracrystal of the first kind, the probability of the molecules occupying these positions is independent of the distance from an arbitrary origin. In a paracrystal of the second type, positional indeterminancy increases with increasing distance. Myelin is a paracrystal of the second kind. The purpose of this paper is to present evidence concerning the paracrystalline nature of PHF in Alzheimer tangles based on analyses of variance of PHF interfilament spacing.
Kidney proximal tubules: Ultrastructural response to changes in calcium and adenosine triphosphate
Authors: Craig B. L. , Lefurgey A. , Jacobs W. R. , Mandel L. J.
Published: June 2020

Use of conventional transmission electron microscopy (TEM) and x-ray microanalysis (EPXMA) to identify the intracellular sites of Ca binding and release has provided valuable Information concerning the mechanism for the cellular action of Ca in a variety of cells. In the kidney much indirect evidence links Ca with cellular Injury, but direct measurements of Ca compartmentation are lacking. We report here our initial ultrastructural observations of kidney proximal tubules exposed to agents which alter the compartmentation of Ca in predictable ways. This TEM evaluation of intracellular structural compartments such as mitochondria or endoplasmic reticulum provides the basis for correlative EPXMA studies of elemental compartmentation under the same conditions.

A suspension of kidney proximal tubules was isolated from the rabbit kidney as previously described and incubated at 37°C for up to 20’ with the Ca lonophores A23187 (5μM) or ionomycin (10 μM) or with the mitochondrial uncoupler FCCP (4 μM).
Effects of aging on axon terminals in the dentate molecular layer
Authors: Cullen-Dockstader K. , Fifkova E.
Published: June 2020

Normal aging results in a pronounced spatial memory deficit associated with a rapid decay of long-term potentiation at the synapses between the perforant path and spines in the medial and distal thirds of the dentate molecular layer (DML), suggesting the alteration of synaptic transmission in the dentate fascia. While the number of dentate granule cells remains unchanged, and there are no obvious pathological changes in these cells associated with increasing age, the density of their axospinous contacts has been shown to decrease. There are indications that the presynaptic element is affected by senescence before the postsynaptic element, yet little attention has been given to the fine structure of the remaining axon terminals. Therefore, we studied the axon terminals of the perforant path in the DML across three age groups.

5 Male rats (Fischer 344) of each age group (3, 24 and 30 months), were perfused through the aorta.
Scanning Electron Microscopy of mouse BALB/C/Cd polycystic renal disease
Authors: Keyhani E. , Penasse W.
Published: June 2020

Mouse BALB/C/Cd exhibited spontaneous transplantable kidney adenocarcinoma which affected both sexes and involved both kidneys. This disease is characterized by plain cysts and cysts with single or multiple polyps to solid tumors at various stages of evolution. The fine structure of solid tumor was previously described.

Single or multiple (up to 10) cysts were present throughout the cortex parenchyma. Their sizes ranged from 1 to 8 mm in diameter. The cysts occurred from both proximal and distal tubules and were composed of a single layer of cubic-cylindrical epithelial cells. Most cysts exhibited single or multiple focal areas of epithelial polypoid hyperplasia. Single polyps consisted of accumulations of hyperplasic cells piling up on top of each other (Fig. l). The other form consisted of single or multiple branched polyps with a central vascularized core (Fig. 2). The number of cells forming polyps hyperplasia varied between a dozen to up to several hundreds of cells.
The effects of different fixatives on the porcine integument
Authors: Monteiro-Riviere N. A. , Manning T. O.
Published: June 2020

The porcine integument is structurally similar to the human integument and is frequently used in dermatological studies. To assess the viability of porcine skin or to study cutaneous toxicity, normal cells and organelles must be optimally preserved with minimum alteration from the living state. Several investigators have proposed different fixation methods to study the integument. However, some of these methods are not appropriate for the porcine species. The objective of this study is to assess different fixatives and osmolalities for the porcine integument.

Skin samples were obtained from Yorkshire pigs, minced and placed in one of the following fixatives overnight at 4°C; 1. 2% glutaraldehyde(G) in O.1M phosphate buffer (PB) (397 mOsm), 2. 2% G in 0.2M PB (535mOsm), 3. 4% G in 0.1M PB (566 mOsm), 4. 4% G in 0.2M PB (786 mOsm), 5. 4% formaldehyde and 1% G in PB (1774mOsm), 6. 5% G and 4% paraformaldehyde in 0.2M cacodylate buffer (CB) (1522mOsm), 7. 2.5% G and 2% paraformaldehyde in 0.2M CB (976mOsm).
Ultrastructure of a caffeine-resistant mutant of Aspergillus parasiticus during aflatoxin production
Authors: Jones S. B. , Dobson T. O. , Stahl H. G. , Buchanan R. L.
Published: June 2020

Caffeine (1,3,7-trimethylxanthine) inhibits growth and aflatoxin synthesis in A. parasiticus. A caffeine-resistant mutant (BCR1) of A. parasiticus NRRL 2999 was isolated in which sporulation and aflatoxin production occurred only in the presence of caffeine. Further, when cultured in glucose-mineral salts (GMS), BCR1 required amino acids in addition to caffeine in order to produce aflatoxin. A system for ultrastructure study was thus available in which aflatoxin synthesis was controlled by supplementation with amino acids. Experiments were conducted to identify morphology that could be correlated with aflatoxin production in the mutant.

Cultures were conidia-initiated in GMS at 28C with agitation, with 6% peptone as amino acid source. Caffeine at 4 mg/ml permitted full growth and stimulated maximal aflatoxin accumulation. Fungal pellets were retrieved at 4 days and portions of the periphery were fixed in 3% glutaraldehyde in 80 mM Na-cacodylate, pH 7.0, for 3 hr.
A comparative study of fixation and dehydration techniques for the preservation of conidial structures in fungi for SEM
Authors: Edelmann Richard E. , Hogan Margaret E.
Published: June 2020

Conventional preparative techniques for biological specimens For scanning electron microscopy (SEM), when used for Fungal specimens, involve immersion in fixation and dehydration solutions. This often results in physical damage to delicate reproductive structures. Attempts at eliminating this damage using OsO4 vapors as a fixative, followed by air drying, may also produce less than optimal results.

In order to devise an improved method for preparing fungal specimens, several genera were selected for their very delicate aerial conidial structures, and were prepared using six different procedures. The various protocols were as Follows:

1)

Immersion Fixation in 1% paraformaldehyde, 2.5% glutaraldehyde in H2O, post-fixation with 2% OsO4, and critical point drying

2)

2% OsO4 (in H2O) vapor fixation and air drying

3)

2% OsO4 (in H2O) vapor fixation and freeze drying

4)

Powdered paraformaldehyde in a 6% relative humidity atmosphere vapor fixation and air drying

5)

Aqueous 5% paraformaldehyde/8% glutaraldehyde vapor fixation, and air drying

6)

Aqueous 5% paraFormaldehyde/8% glutaraldehyde vapor fixation, and freeze drying
Adapting cytochemical protocols to localize antigens, labeled-ligands, and labeled probes for mRNA
Authors: Childs Gwen V. , Unabia Geda , Lloyd Jonathan
Published: June 2020

Current methods available in immunocytochemistry can be adapted to obtain multiple stains for antigens, labeled-ligands, and/or mRNA and thus achieve a wider view of the structural and functional organization of a cell. In this presentation, applications of immunocytochemical stains for pituitary hormones in combination with affinity cytochemical stains for labelled probes for ligand-receptor complexes or messenger RNA will be described along with a practical view of how each stain is quantified.

The ABC peroxidase stains are useful for studies of antigens in semi-thin (1 μm) plastic-embedded sections or for antigens, biotinylated ligands or biotinylated probes for mRNA in whole cells. For the first group, cells or tissues are fixed optimally for the antigen and then embedded in plastic with a-protocol adapted to the antigen or antigenic site. Commonly used plastics that avoid harsh dehydrating or curing conditions include Lowicryl or LR White. Epoxy plastics may be used for hardy antigens.
A new high-resolution Electron Energy-Loss Spectroscopy microscope
Authors: Tanaka Michiyoshi , Terauchi Masami , Kuzuo Ryuichi , Tsuno Katsushige , Ohyama Junichi , Harada Yoshiyasu
Published: June 2020

Boersch, Geiger and coworkers constructed high resolution electron energy-loss spectroscopy (EELS) instruments. These had a very high energy resolution of approximately 3meV, but were operated at a relatively low accelerating voltage of about 30kV and could only obtain spectra from specimen areas greater than about 10µm in diameter.

We have been developing a new EELS instrument to investigate detailed electronic structures and thermal vibrations by taking spectra from specified small specimen areas and specified small reciprocal space areas. Our EELS microscope is composed of a thermal-type field emission gun, a Wien-filter monochrometer, the basic part of a JEM-1200EX microscope, a Wien-filter analyzer and a CCD detection system (Fig.1). Figure 2 schematically shows an xy-section of the Wien filter. The filter was designed to produce the Wien condition E=vxB (E:electric field, B:magnetic field, v:velocity of electrons) not only in the filter but also in the fringing field regions and to produce the stigmatic focus. The length of the filter was chosen to be 4cm.
Electron-optical design of a high-resolution objective lens for low-voltage Scanning Electron Microscope of biological applications
Authors: Ximen J. , Lin P. S. D. , Pawley J. B. , Schippert M.
Published: June 2020

By providing higher image contrast and reduced charging artifacts, the low voltage scanning electron microscope (LVSEM) is a valuable tool for surface characterization, of particular importance on nonconductive material such as biological specimens. Several SEM designs optimized for use at low voltage have been proposed.

Recently, we have designed a new high resolution LVSEM using a field emission gun. The key problem is to decrease both the spherical and chromatic aberration coefficients by using a magnetic lens of small bore diameters(5mm and 10mm) and a narrow gap (7.5mm) (FIG. 1). In our first design, the magnetic lens is built around the side-entry stage of a Philips 300kV TEM and performs as well as that in the present Hitachi SEM H-900 or H-900S. Its simple design has been chosen for reliability and flexibility in farbrication.
A new tool for rapid development of electron microscopy negatives and micrographs: Initial impressions of the MOHR/PRO-8 processor
Authors: Long James C.
Published: June 2020

Over the years, many techniques and products have been developed to reduce the amount of time spent in a darkroom processing electron microscopy negatives and micrographs. One of the latest tools, effective in this effort, is the Mohr/Pro-8 film and rc paper processor.

At the time of writing, a unit has been recently installed in the photographic facilities of the Electron Microscopy Center at Texas A&M University. It is being evaluated for use with TEM sheet film, SEM sheet film, 35mm roll film (B&W), and rc paper.

Originally designed for use in the phototypesetting industry, this processor has only recently been introduced to the field of electron microscopy.

The unit is a tabletop model, approximately 1.5 × 1.5 × 2.0 ft, and uses a roller transport method of processing. It has an adjustable processing time of 2 to 6.5 minutes, dry-to-dry. The installed unit has an extended processing switch, enabling processing times of 8 to 14 minutes to be selected.
A practical algorithm for maximum-likelihood HREM image reconstruction
Authors: Coene W.
Published: June 2020

Reconstruction in HREM of the complex wave function at the exit face of a crystal foil out of a focal series of HREM images, and with correction for the microscope's aberrations, can be performed with a variety of algorithms depending on the approximations involved for the HREM image formation. The maximum-a-posteriori (MAP) recursive reconstruction algorithm of Kirkland is the most general one with the full benefit of the effects of non-linear imaging and partial coherence, which are correctly treated in terms of a transmission-cross-coefficient (TCC). However, the routine application of the Kirkland algorithm has thusfar been hampered by its enormous computational demands, especially when large image frame sizes (5122) and a large number of HREM images (≥20) are aimed at. In this paper, we present a modified version of the Kirkland method within a maximum-likelihood (MAL) framework, and with a new numerical implementation yielding a workable algorithm with a much higher computational efficiency.
Exit-surface wave reconstruction using a focal series
Authors: de Ruijter W.J. , McCartney M.R. , Smith David J. , Weiss J.K.
Published: June 2020

Further advances in resolution enhancement of transmission electron microscopes can be expected from digital processing of image data recorded with slow-scan CCD cameras. Image recording with these new cameras is essential because of their high sensitivity, extreme linearity and negligible geometric distortion. Furthermore, digital image acquisition allows for on-line processing which yields virtually immediate reconstruction results. At present, the most promising techniques for exit-surface wave reconstruction are electron holography and the recently proposed focal variation method. The latter method is based on image processing applied to a series of images recorded at equally spaced defocus.

Exit-surface wave reconstruction using the focal variation method as proposed by Van Dyck and Op de Beeck proceeds in two stages. First, the complex image wave is retrieved by data extraction from a parabola situated in three-dimensional Fourier space. Then the objective lens spherical aberration, astigmatism and defocus are corrected by simply dividing the image wave by the wave aberration function calculated with the appropriate objective lens aberration coefficients which yields the exit-surface wave.
The use of radial density plots to calibrate images of frozen-hydrated specimens
Authors: Belnap David M. , Olson Norman H. , Grochulski Witold D. , Baker Timothy S.
Published: June 2020

Accurate magnification calibration for transmission electron microscopy is best achieved with appropriate external or internal standards. The use of the icosahedral polyoma virus as a standard in frozen-hydrated preparations was previously described. This method used the known diameter of polyoma (from x-ray measurements) as a reference to calibrate the diameters of other viruses. Measurements were made from circular averages computed from individual particle images or from an average image of many individual particle images. The measured diameters of several different spherical viruses are in good agreement with measurements of the same viruses made with x-ray crystallographic and solution scattering techniques.

We found, however, that it is very difficult to accurately measure particle diameters in images taken from frozen-hydrated specimens. This difficulty is attributable to several factors including i) uncertainty about the solvent density level, ii) superposition of density features that occur in two-dimensional projections of three-dimensional objects, iii) uneven outer surfaces of virus particles, iv) characteristically high noise and low contrast levels in micrographs, and v) contrast transfer function (CTF) effects.
Structure hierarchy in liquid crystalline polymers
Authors: Sawyer Linda C.
Published: June 2020

Structure models have been developed for the liquid crystalline polymers (LCPs), showing the existence of fibrillar hierarchies for both the lyotropic aramids and the thermotropic aromatic copolyesters. Hierarchies of structure have also been observed for biological materials. The nature of the smallest nanostructure that aggregates, typically microfibrils, and their interaction, are important in understanding the behavior of the material. This paper discusses the first application of scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM) to image the microfibrils in LCPs, in the 1-10 nm size range, resulting in a new LCP structural model.

The structure model proposed earlier, was based on the study of Vectra®thermotropic LCP moldings and extrudates, and Vectran®and Kevlar®fibers. The model resulted from characterization by light microscopy, and transmission and scanning electron microscopy. Recent studies of similar fibers by STM and low voltage FESEM has provided additional insights. Details of single microfibrils and their aggregation into fibrils and macrofibrils was shown.
Some early history of replica techniques for electron microscopy
Authors: Fisher Robert M.
Published: June 2020

By 1940, a half dozen or so commercial or home-built transmission electron microscopes were in use for studies of the ultrastructure of matter. These operated at 30-60 kV and most pioneering microscopists were preoccupied with their search for electron transparent substrates to support dispersions of particulates or bacteria for TEM examination and did not contemplate studies of bulk materials. Metallurgist H. Mahl and other physical scientists, accustomed to examining etched, deformed or machined specimens by reflected light in the optical microscope, were also highly motivated to capitalize on the superior resolution of the electron microscope. Mahl originated several methods of preparing thin oxide or lacquer impressions of surfaces that were transparent in his 50 kV TEM. The utility of replication was recognized immediately and many variations on the theme, including two-step negative-positive replicas, soon appeared. Intense development of replica techniques slowed after 1955 but important advances still occur. The availability of 100 kV instruments, advent of thin film methods for metals and ceramics and microtoming of thin sections for biological specimens largely eliminated any need to resort to replicas.
The 50 years before the Electron Microscope: From electron to electron lens — hans busch and the “Göttingen Group”
Authors: Rudenberg H. Gunther
Published: June 2020

Much of the research to characterize the electron at the turn of the century was made by physics professors at Göttingen University in Germany. Their efforts led their student Hans Busch to experiment and later to analyze the focusing action of a magnetic coil. With this he gave birth to the field of electron optics. Little known are either the delays associated with his discovery or the contributions of others in the “Göttingen Electron Group.”

In 1881, fifty years before the invention of the electron microscope, Rieke in Göttingen analyzed the constriction of the canal rays in a Crookes tube by a surrounding magnetic coil. Next, in 1897, which was a particularly exciting year in the history of the electron, Braun conceived the cathode ray oscillograph tube - now named for him in Europe - and J. J. Thomson in England made fundamental measurements on the electron. Also that year Wiechert, who must be recognized as co-discoverer of the electron, made similar measurements in Königsberg. After his appointment to Göttingen later in 1897 there followed a decade of intensive experimental research on the e/m ratio and characteristics of the electron by a half-dozen Göttingen physics professors (e.g. desCoudres, Kaufmann, Rieke, Simon, Stark, Wiechert).
Early contributions to the electron microscope: The relevant work and patents of reinhold rüdenberg
Authors: Rudenberg F. Hermann , Rudenberg H. Gunther
Published: June 2020

Few know that Reinhold Rüdenberg studied with the “Göttingen Electron Group” in 1906-8, that he was the first to detail the electron microscope in 1930-31 in Germany, that in the 1940's he contributed to the Farrand electron microscope, or that he conceived a number of other electron beam devices. Histories of the electron microscope seldom cite his work, and then only denigrate his role. Our objective here is to correct this misconception.

Reinhold Rüdenberg first demonstrated his interest in electronic devices as a high school junior in 1899 when he built a Rühmkorff induction coil which he used to power an x-ray tube and to generate Hertzian waves. While still a student of electrical engineering at Hannover, he applied for his first patent, on a radio oscillator, and published the first of over 100 technical articles. With a Doctor of Engineering from Hannover he was appointed instructor under L. Prandtl at the University of Göttingen.