bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural anomalies of the flagellum in relation with abnormal motility in hybrid mice (C57BL x CDI)F1, treated with a mutagen: Ethyl methane sulphonate (EMS)
Authors: Ríos B. C. , Cantú M.G. , Gallegos L. , Ramírez B. E. 
Published: June 2020

In 1975, the effect of EMS on the dismorphic sperm fraction, was reported (1). Since then, the action of this drug at different levels on the seminiferous epithelium and over the spermatogenic process has been studied (2,3).Modifications in relation to the finding of morphologically abnormal sperms have been described too (6). Likewise the lowering of the count and of the sperm motility have been used as evidence of genetic damage caused by drugs (5). Recently it has been described that EMS not only affects the morphology of sperm but also their concentration and their motility (6). The present study has been done to determine if the effect of EMS on sperm motility has a morphological cause. Hybrid mice were administred a dose of 200 mg/Kg. of EMS intraperitoneally, for five consecutive days. The epididimary and deferens ducts content was studied four weeks later. They were fixed in 2.5% glutaraldehyde and 1 % osmium tetroxide; the material was included in epoxy-resin by the conventional method, sectioned and studied with a Zeiss EM 109 electron microscope.
SEM study of cytoskeleton of osteoblasts immobilized on HA-ceramic during biocompatibility testing
Authors: Fratssinet P. , Delga C. , Conte P. , Rouquet N. , Nadal M. 
Published: June 2020

Some standards for biocompatibility testing of biomaterials requires the determination of the cytoskeleton aspect of differentiated cells in contact with the material. It is usually determined by indirect immunofluorescence staining of cytoskeleton proteins and examination with a light microscope.This examination is difficult on non transparent material and the resolution is very poor. In order to study the interaction of osteoblast cytoskeleton with HA-macroporous ceramics, we grew chicken embryo osteoblasts on the material then we extracted cell membranes to expose the cytoskeleton proteins. They were then examined in SEM.
The leaf mesophyll of coyotillo (Karwinskia humboldtiana Zucc.) morphological characterization
Authors: Ordóñez J. Ruiz , Torres Cepeda T.E. , López A. Piñeyro 
Published: June 2020

Karwinskia humboldtiana, a semi arid shrub of México known by the ccmnon names cqyotillo or tullidora produces several toxins with high toxicity against humans and ruminants. These toxins are present in different organs the plant. In relation to morphology, with the exception of the histological stucty of Lux and Earl, we have little information applicable in defining kind of tissue, internal secretory structures or cells are involved in the production, storing or distribution of these toxins. The aim of this work is to offer sane structural description of coyotillo mesophyll especially the features of the internal secretory structures,Fresh leaves in physiological mature stage were obtained fran the field, and processed by routine techniques of light microscopy and transmission and scanning electron microscopy.
convergent-beam diffraction from surfaces
Authors: Eades J. A. , Smith A. E. , Lynch D. F. 
Published: June 2020

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.
Effects of surface stress relaxation on reflection electron microscopy images of normal emerging edge dislocations
Authors: Peng L.-M. , Cowley J.M. , Hsu Tung 
Published: June 2020

It has been well established that, due to the termination of the bulk periodic potential at the surface, the forces acting on the surface atoms are no longer symmetrical but the surface atoms are displaced from their ideal lattice positions. Similarly, additional surface relaxation due to the loss of periodicity is expected to occur at the points where some kinds of bulk defects, like dislocations, intersect the surface. There are experimental indications that the rather more pronounced contrast observed in TEM at these intersection points may be contributed to by the additional stress relaxation.The REM technique is sensitive to crystal orientation and provides an ideal method of detecting the surface strain relaxation. The diffraction contrast effects arise from the changes of the angle between the incident beam and the local surface reciprocal lattice resulting from the strain field on the surface.
Electron energy loss spectroscopy and energy filtered electron microscopy
Authors: Shuman H. 
Published: June 2020

The distribution of elements in thin biological specimens can be determined at high resolution with electron energy loss spectroscopy (EELS). The advantage of EELS is that the signal is large, since roughly 50% of the characteristic ionization events can be observed, but this is accompanied by difficulties related to the generally large background and the more stringent requirements for ultrathin specimens in EELS than in electron probe X-ray microanalysis. Therefore it is generally necessary to use signal processing methods to extract absorption edge information in EELS.EELS can be used in two ways: to produce line spectra with a stationary or rastered probe, or to directly form energy-filtered electron microscope (EFEM) images representative of the elemental distribution.
Making optimum use of the signal in image digitization
Authors: Christenson K. K. 
Published: June 2020

The detectors on modern electron microscopes often have a very high bandwidth which makes their outputs appear noisy on a short time scale. This noise is not a problem when photographing an image because the film integrates the signal. But it causes an annoying blurring of the trace in slow y-modulated line scans and can result in large errors if the signal is measured with a fast analog to digital converter (ADC)(Figs, 1,2).The noise in digital measurements can be reduced by reading the detector may times and taking the numerical average of the readings. This requires no extra hardware but it increases the time required to acquire a linescan or image and ignores the fundamental problem that the ADC wastes most of the information available in the signal by only sampling for a very small portion of its total cycle time.
Heteroepitaxy of stable metallic phases on GaAs: identification of candidate phases by TEM
Authors: Sands T. 
Published: June 2020

The structural perfection and thermal stability of epitaxical silicide contacts provides silicon technology with the potential for three-dimensional device integration as well as novel discrete device structures. Furthermore, the detrimental effects of grain boundaries on film resistivity and interdiffusion are eliminated in these epitaxical contact structures. Similar benefits for GaAs technology may be expected if stable metallic phases that grow epitaxically on GaAs can be identified. Such structures would also represent the ideal configuration for understanding the relationship between interface structure and electronic transport properties of metal/compound semiconductor systems.The search for candidate metallic phases can be simplified by considering only those phases that are cubic with lattice parameters compatible with aо (GaAs) = 0.565 nm. Of the many cubic structure types, the CsCl structure is the most common among the transition metal MGa phases.
Microstructural Characterization of Au-Ge-Ni based ohmic contacts to GaAs/AlGaAs modfet device
Authors: Rai A.K. , Petford-Long A.K. , Ezis A. , Langer D.W. 
Published: June 2020

Considerable amount of work has been done in studying the relationship between the contact resistance and the microstructure of the Au-Ge-Ni based ohmic contacts to n-GaAs. It has been found that the lower contact resistivity is due to the presence of Ge rich and Au free regions (good contact area) in contact with GaAs. Thus in order to obtain an ohmic contact with lower contact resistance one should obtain a uniformly alloyed region of good contact areas almost everywhere. This can possibly be accomplished by utilizing various alloying schemes. In this work microstructural characterization, employing TEM techniques, of the sequentially deposited Au-Ge-Ni based ohmic contact to the MODFET device is presented.The substrate used in the present work consists of 1 μm thick buffer layer of GaAs grown on a semi-insulating GaAs substrate followed by a 25 Å spacer layer of undoped AlGaAs.
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.
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.
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.
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.
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.
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.
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.