bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy loss spectra from silicon compounds: SiL edges
Authors: Carpenter R. W. , Skiff W. M. , Lin S. H. 
Published: June 2020

Electron energy loss microanalysis is of great interest for analysis of second phases containing light elements in semiconductor materials. Small precipitates (minimum dimension ∼10nm) in heat treated CZ-Si wafers were identified in-situ earlier as amorphous SiOx particles, and it was also noted that there was a marked change in the shape of the Si-L edge in spectra from the precipitate relative to those from the surrounding matrix.This work has been extended to include spectra from other Si compounds, to examine the shape change of the L edge when silicon is in different environments. All of the spectra shown here were taken at l00kV with fixed, convergent probe. The incident probe size on the specimens was ∼10nm. Many of the spectra was taken using a cryogenic stage with the specimen near -196°C, which made possible extended observations of a single area. All specimens were wedge shaped (crushed or ion-thinned), with spectra taken from thin edges.
Is full computer automation of H.R.E.M. feasible?
Authors: Krivanek O.L. , Stadelmann P. , Higgs A. , Chen C. , Disko M.M. 
Published: June 2020

Recently it has become clear that a high resolution electron microscope (H.R.E.M.) can be controlled by a computer which "sees" the image via a TV camera connected to a digital framestore, and which "adjusts" the microscope imaging parameters via a D/A (Digital/Analog) control interface so as to optimize the image. The question therefore arises whether it will some day be possible to replace human microscope operators with inexpensive minicomputers capable of performing all the traditionally human tasks, but with much greater precision, repeatability, and speed.Fig. 1 shows a schematic of the computer control system for a JEM 200CX HREM under development at ASU. The TV camera is coupled via a 2:1 reducing fibre- optics bundle to a P22 phosphor screen as described previously. The DeAnza framestore has enough memory for up to four 512x512x8 bit images, and can perform various simple operations such as adding or subtracting two images at TV rates (on-line).
Microtubules, sickle cell hemoglobin fibers, and various crystal structures
Authors: Edelstein Stuart J. , Crepeau Richard H. , Akey Christopher W. , Ceska Thomas A. 
Published: June 2020

Structural studies involving electron microscopy and image reconstruction techniques are now approaching levels of resolution that had previously been the domain of x-ray crystallography. Studies on purple membrane are a prime example. Although few other systems have reached comparable levels of resolution, progress is being made on several fronts. Citing work from this laboratory, I will illustrate three ways we are using electron microscopy to approach the border with x-ray crystallography, in studies on: three-dimensional crystals (cytochrome oxidase from P. aeruginosa, catalase, and beef heart F1-ATPase); arrays of proteins which do not form three-dimensional crystals (tubulin sheets and microtubules); and the supra-molecular structure of a protein of known atomic structure (sickle cell hemoglobin).A. Electron microscopy as an adjunct to X-ray crystallography for threedimensional crystalsOur applications in this area have primarily consisted of embedding and sectioning techniques with crystals that are too small or otherwise unsuitable for x-ray crystallography, such as occur for cytochrome oxidase from P. aeruginosa or beef heart F1-ATPase.
Electron microscopy of frozen hydrated suspensions
Authors: Lepault Jean 
Published: June 2020

High resolution electron microscopy of biological objects requires minimizing of both preparation artefacts and beam damage. Taylor and Glaeser have shown that these two requirements can be fulfilled by observing frozen hydrated specimens. Routine use of frozen hydrated specimens has been limited by two factors: the lack of preparation methods and the technical difficulty in building high resolution low temperature stages compatible with cold transfer. This last limitation has been removed by the development of new gas cooled specimens holders, by the improvement of existing holders, and by creation of a super conducting lens system where the specimen is kept at 4.2 k. Finally, recent methods of preparing thin films of water (500 - 3000 Å) have allowed routine observation of frozen suspensions. Parameters influencing structural preservation during both preparation and observation can thus be analyzed.HYDRATION AND VITRIFICATION: Maintenance of hydration of biological objects in the electron microscope high vacuum permits preservation of structural details to better than 3Å.
Differential staining of crystalline arrays of outer mitochondrial membrane channels
Authors: Mannella Carmen A. , Frank Joachim 
Published: June 2020

The mitochondrial outer membrane contains pore-forming polypeptides (Mr⋍= 30,000) which are its main protein components in plants and fungi. Outer membranes (OM) isolated from Neurospora mitochondria often contain extended regular arrays of subunits with stain-accumulating centers 2-3 nm in diameter. That these subunits are the mitochondrial channels has been established immunologically. Antibodies against the predominant 31-kDa OM polypeptide of Neurospora (a) prevent in vitro insertion of OM channels into bilayers and (b) preferentially bind to the crystalline membranes in OM fractions.Planar projections of individual OM channel layers have been reconstructed from electron micrographs of negatively stained crystalline vesicles by Fourier filtration. In the usual array (Fig. 1a) the unit cell is a parallelogram which can hold six stain centers (putative pore openings) arranged in a hexagon with p2 symmetry. There are large pore-free areas in these arrays (* in Fig. 1a) which are likely composed of phospholipid, since they disappear when the membranes are treated with phospholipase A2(Fig. 1b).
Toward an alignment of the actin molecule within the actin filament
Authors: Smith P.R. , Fowler W.E. , Aebi U. 
Published: June 2020

An understanding of the specific interactions of actin with regulatory proteins has been limited by the lack of information about the structure of the actin filament. Molecular actin has been studied in actin-DNase I complexes by single crystal X-ray analysis, to a resolution of about 0.6nm, and in the electron microscope where two dimensional actin sheets have been reconstructed to a maximum resolution of 1.5nm. While these studies have shown something of the structure of individual actin molecules, essential information about the orientation of actin in the filament is still unavailable.The work of Egelman & DeRosier has, however, suggested a method which could be used to provide an initial quantitative estimate of the orientation of actin within the filament. This method involves the quantitative comparison of computed diffraction data from single actin filaments with diffraction data derived from synthetic filaments constructed using the molecular model of actin as a building block. Their preliminary work was conducted using a model consisting of two juxtaposed spheres of equal size.
Membrane-bound vesicles associated with the microvilli in the midgut of the freshwater microcrustacean, Daphnia magna
Authors: Jansma Patricia L. 
Published: June 2020

The presence of the membrane bound vesicles or blebs on the intestinal epithelial cells has been demonstrated in a variety of vertebrates such as chicks, piglets, hamsters, and humans. The only invertebrates shown to have these microvillar blebs are two species of f1ies. While investigating the digestive processes of the freshwater microcrustacean, Daphnia magna, the presence of these microvillar blebs was noticed.Daphnia magna fed in a suspension of axenically grown green alga, Chlamydomonas reinhardii for one hour were narcotized with CO2 saturated water. The intestinal tracts were excised in 2% glutaraldehyde in 0.2 M cacodyl ate buffer and then placed in fresh 2% glutaraldehyde for one hour. After rinsing in 0.1 M cacodylate buffer, the sample was postfixed in 2% OsO4, dehydrated with a graded ethanol series, infiltrated and embedded with Epon-Araldite. Thin sections were stained with uranyl acetate and Reynolds lead citrate before viewing with the Philips EM 200.
Low-voltage scanning electron microscopy
Authors: Pawley J. B. , Winters M. P. 
Published: June 2020

There are two reasons for the renewed interest in using the SEM at beam voltages, Vb, around 1kV (LVSEM). The most common one arises from applications in the semiconductor industry and emphasizes the reduction in charging artifacts and in subsurface beam damage. The second reason postulates that the increased contrast in the topographic component of the secondary electron signal will permit an important improvement in topographic spatial resolution if only a sufficiently small probe diameter can be obtained. We shall treat these two areas separately and then mention some of the strategies that have been adopted to make LVSEM work.Surfaces are very important in the manufacture of modern semiconductor devices and the ability of the electron probe to induce current flow (EBIC), to detect variations in surface voltage, Vs, and to excite characteristic x rays in addition to its ability to image topography in an easily understandable way guaranteed the SEM a major role in programs of semiconductor development and failure analysis. There were two problems, however, charging and beam-induced damage to the specimen.
Qualitative and quantitative SEM of gastrointestinal tract
Authors: Carr K.E. , Hayes T.L. , Hume S.P. , Kamel H.M.H. 
Published: June 2020

Introduction:The natural mucosal surfaces of the digestive tract provide an interface with the environment which undergoes structural changes in response to experimental procedures and naturally occurring disease. This paper describes the application of modern scanning electron microscopy (SEM) techniques to gastrointestinal research. Initially based on qualitative studies of mucosal responses to insult such as irradiation or hyperthermia, the interpretation of recent results has come to rely increasingly on the semi-quantitative assessment of surface damage and on the use of frozen hydrated specimens to eliminate processing artefact and to permit quantitative elemental analysis.Materials and Methods:Tissue has been collected from several sources. Irradiated mouse intestine has been compared with similar tissue exposed to hyperthermia or drug treatment. Biopsies of gastrointestinal tissue have been collected prospectively or retrospectively, the latter by dewaxing blocks of interest from hospital files. Routine scanning electron microscopy has often been followed by post-embedding the specimen for resin light microscopy and transmission electron microscopy (TEM). Alternatively, resin sections 1 μm thick mounted on coverslip fragments were surface etched by oxygen plasma, shadowed with platinum/palladium and gold coated prior to examination in the SEM. Etched surfaces of mouse duodenum and stomach have also been examined in the frozen hydrated state to record cell and tissue structure as well as data on ion concentrations through x-ray microanalysis.Results and Discussion:Qualitative studies of mucosal responses using secondary electron imaging, in use since the 1960s, are enhanced by the ability of the SEM to record extensive surface areas, if necessary through montage techniques. in this way, the problems of individual variation in an experimental series can be minimised. Mucosal responses to irradiation in small bowel have been documented. The collapse of the villous pattern from erect finger-like processes to irregular conical projections follows a time scale of several days after a single dose of irradiation, whereas equivalent structural changes are completed within 24 hours of an episode of heat injury. Correlative light microscopy and TEM studies show that the changes in shape of the villi after irradiation may be linked to alterations at the interface between surface epithelium and underlying connective tissue: focal irregularities of the basal lamina and detachment of epithelial cells may represent the earliest manifestation of subsequent damage to surface contours.
The stapedius muscle of the squirrel monkey
Authors: Fermin C.D. , Igarashi M. , Thompson G. 
Published: June 2020

Contraction of the stapedius muscle (the acoustic reflex) is useful in the clinical diagnosis of various auditory disorders. In an effort to better understand the basic innervation of the acoustic reflex we are presently studying its neuroanatomy in the squirrel monkey (Saimiri sciureus). Since the morphology of the squirrel monkey stapedius muscle (SMSM) has not been previously described, we will present here our own findings from eleven muscles observed under light (LM) and transmission electron microscopy (TEM). Squirrel monkeys were perfused intracardially with either 10% neutral buffered formalin or 3% buffered glutaraldehyde. The stapedius muscles were dissected out under the operating microscope. For LM, the muscles were embedded in JB-4 plastic and cut serially at 5 micra and for TEM, the muscles were processed as previously described (2).The topography of the SMSM in the middle ear is similar to the human (3). The muscle attaches to the posterior side of the stapes' head by a thin collagenous tendon that extends almost midway into the muscle in a postero- ventral direction.
Filamentous arrays reminiscent of tropomyosin crystals in Hirano bodies of Alzheimer's disease
Authors: Metuzals J. , Montpetit V. , Clapin D.F. , Nelson R.F. 
Published: June 2020

Distinctive acidophilic rods, Hirano bodies, have been observed in brains of patients under a variety of pathological conditions, including Alzheimer's disease, and also in normal, aged individuals. Data on the three-dimensional conformation and on the chemical composition of these structures are presently controversial. The presence of actin in Hirano bodies has been indicated immunocy tochemically. Other authors have proposed that Hirano bodies are crystalline arrays of ribosomes attached to membranes. We report here the results of an investigation of Hirano bodies in the brains of Alzheimer's patients. Applying the techniques of three-dimensional electron microscopy, we have demonstrated as a major component of the Hirano bodies, characteristic arrays of filamentous proteins reminiscent of tropomyosin crystals produced in vitro.Frontal lobe biopsies from 3 patients with pre-senile dementia diagnosed as Alzheimer's disease were investigated by three-dimensional electron microscopy. Fig. 1 is a survey of a Hirano body occupying the main portion of a neurite. It is comprised of sheets of filaments forming characteristic network patterns.
Probing the ultrastructure of the mitotic and meiotic spindle in eggs: An expeditious approach based on semi-thin (0.25 μm) serial sections
Authors: Rieder Conly L. , Bowser S. , Nowogrodzki R. , Ross K. , Sluder G. 
Published: June 2020

Eggs have long been a favorite material for studying the mechanism of karyokinesis in-vivo and in-vitro. They can be obtained in great numbers and, when fertilized, divide synchronously over many cell cycles. However, they are not considered to be a practical system for ultrastructural studies on the mitotic apparatus (MA) for several reasons, the most obvious of which is that sectioning them is a formidable task: over 1000 ultra-thin sections need to be cut from a single 80-100 μm diameter egg and of these sections only a small percentage will contain the area or structure of interest. Thus it is difficult and time consuming to obtain reliable ultrastructural data concerning the MA of eggs; and when it is obtained it is necessarily based on a small sample size.We have recently developed a procedure which will facilitate many studies concerned with the ultrastructure of the MA in eggs. It is based on the availability of biological HVEM's and on the observation that 0.25 μm thick serial sections can be screened at high resolution for content (after mounting on slot grids and staining with uranyl and lead) by phase contrast light microscopy (LM; Figs 1-2).
Quantitative electron microscopic study of the hepatic endoplasmic reticulum in Reye’s syndrome
Authors: Sturgess J. M. , de la Iglesia F. A. 
Published: June 2020

Reye’s syndrome represents a serious clinical condition in children with symptoms of liver involvement, acute encephalopathy and biochemical alterations. This condition, for which the etiology is not yet known, has been linked to mycotoxin poisoning, viral infection, or simulated by drug toxicity, particularly salicylates. However, basic cellular mechanisms and early ultrastructural changes have not been well defined. The liver endoplasmic reticulum (ER) plays a fundamental role in detoxification. Our understanding of ER changes in this syndrome would clarify the processes leading to liver damage.Quantitative electron microscopic aspects of hepatocytes were evaluated to characterize numerically the tissue changes in liver biopsies from patients with Reye's syndrome and compared with data available from age-matched controls. Liver biopsies were evaluated from three patients, 1.5, 6.5 and 13.5 years of age, having clinical and pathological evidence of Reye's syndrome. All biopsies were obtained within 24 hours of clinical onset. Preservation of architecture of hepatocytes was adequate for critical evaluation of ultrastructure.
Cytochemical localization of nitrate reductase in Chlorella
Authors: Michaels A. , Wolosowick J. , Kriho V. , Solomonson L. 
Published: June 2020

We have investigated the subcellular location of nitrate reductase in Chlorella. Chlorella is a unicellular green algae. The algae can be readily cultured under defined conditions. When cultures of Chlorella are grown in media containing ammonia, as a nitrogen source, there is a very low activity of nitrate reductase. If cultures are are grown in the absence of ammonia, but with nitrate substituted as a nitrogen source, the activity of the enzyme increases about ten-fold. This increase is dependent on protein synthesis and is inhibited by cycloheximide.Nitrate reductase was purified to homogeneity and injected into rabbits. Antinitrate reductase IGg was prepared and used to localize the enzyme in the light microscope with FITC conjugated goat anti-rabbit IGg and electron microscope with goat anti-rabbit IGg coupled to colloidal gold.Samples of ammonia and nitrate grown cultures were fixed in gluteral- dehyde and embedded in polyethylene glycol. Thick and thin sections were cut for light and electron microscope localization according to Wolosowick and May.
Atomic orientation effects in proton stopping at low velocity
Authors: Lam Kin 
Published: June 2020

The energy of moving ions in solid is dependent on the electronic density as well as the atomic structural properties of the target material. These factors contribute to the observable effects in polycrystalline material using the scanning ion microscope. Here we outline a method to investigate the dependence of low velocity proton stopping on interatomic distances and orientations.The interaction of charged particles with atoms in the frame work of the Fermi gas model was proposed by Lindhard. For a system of atoms, the electronic Lindhard stopping power can be generalized to the formwhere the stopping power function is defined as
Ultrastructural morphometric analysis of lymphocyte nuclear structure
Authors: Dardick I. , Bladon T. , Sinnott N. , Dardick A. , Hall R. , Jeans D. , Setterfield G. 
Published: June 2020

Despite the important -role of nuclear morphology in tissue recognition and tumor diagnosis, the variation of this organelle in terms of size, shape and condensed chromatin organization, and the mechanisms involved, are poorly understood. Since antigenic and mitogenic activation of the normal lymphocyte leads to considerable alteration in the nucleus in terms of size and condensed chromatin distribution, this cell type affords an opportunity to study this phenomenon in detail. Previous studies have shown that a sizeable amount of nuclear protein is made during lymphocyte transformation.This ultrastructural morphometric image analysis was undertaken in an attempt to quantitate modifications in nuclear components during T-lymphocyte (human peripheral) and B-lymphocyte (mouse spleen) transformation induced with concanavalin A (Con A) and bacterial lipopolysaccharide (LPS) respectively. Cell suspensions and tissue samples were obtained at varying intervals after mitogen stimulation. Random nuclei, both unstimulated (Type 1), partially transformed (Type 2), and fully transformed (Type 3) were photographed (Figs 1 to 3).
Epitaxial crystallization of lipids containing alkane chains
Authors: Dorset Douglas L. 
Published: June 2020

As shown in an accompanying paper, the quantitative use of electron diffration data from slightly bent, thin microcrystals for structure analysis is impeded when a long unit cell axis is parallel to the incident beam. A total crystallographic analysis is allowed, on the other hand, if a shorter cell edge parallels this direction so that the largest Patterson components along this vector are not severely spread out by slight crystal bending.Because of favored van der Waals interactions, typical solution crystal growth of molecular organic compounds causes the longest unit cell axis to lie approximately perpendicular to the best developed crystal face. A crystal growth forcing the longest unit cell axis to lie in this direction, on the other hand, can be realized by epitaxy, the earliest demonstration for polymethylene chain materials given by Willems. Although the use of cleaved salt crystal faces has long been popular for nucleation of epitaxial growth, organic substrates, such as naphthalene, present certain advantages.
Correlation averaging of sickle cell hemoglobin fibers
Authors: Crepeau R.H. , Edelstein S.J. 
Published: June 2020

Deoxyhemoglobin S fibers, responsible for the erythrocyte deformation characteristic of sickle cell anemia, have been studied by applying correlation techniques to negatively stained images. The objectives of this study are to provide higher resolution three-dimensional reconstructions than previously obtained. Earlier studies in this laboratory required a combined real space - Fourier space analysis (REFORM) to determine the fourteen strand morphology of the cross-section and the approximate tetramer packing arrangement to about 30 Å resolution. That work provided the basis for preliminary molecular model building efforts, but higher resolution will be necessary to establish the orientation of individual tetramers. An absolute directionality in the fibers, implied by the presence of an odd number of pairs of filaments in the fourteen strand model, is demonstrated by the real space correlation method described here.Correlation methods have been used for locating equivalent copies of a reference particle in either randomly ordered two-dimensional particles (projection) or imperfectly ordered flat sheets.