bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructure of the Ascospores and Conidia of Venturia Inaequalis
Authors: Granett A. L. 
Published: June 2020

Venturia inaequalis (Cke.) Wint. is the causal agent of scab,a worldwide disease of apples. There have been few electron microscopic investigations on any phase of this fungus. The studies reported herein were initiated to clarify some ultrastructural characteristics of ascospores and conidia.In the spring ascospores develop within perithecia on decaying apple leaves from the previous year. Either whole perithecia were teased from leaves, or ascospores were isolated from leaves in an air tunnel device. Conidia develop on living leaves, blossoms, and fruits. Infected leaves were sprayed with distilled water and these spores were collected and concentrated into a pellet by low speed centrifugation. Perithecia, ascospores, and conidia were fixed in glutaraldehyde and osmium tetroxide; ultrathin sections were stained with uranyl acetate and lead citrate.
Fine Structure Changes Produced by Gastric Mucosal Irritants: Ethanol and Urea
Authors: Eastwood Gregory L. , Kirchner John P. 
Published: June 2020

Many substances cause physiologic alterations in the gastric mucosa such that the subsequent back-diffusion of H+ ion leads to morphologic damage. To account for the abnormal permeability induced by gastric irritants, it has been suggested that the tight junctions between surface epithelial cells are loosened. However, since little is known regarding the fine structural effects of these substances, we performed the following studies using two recognized irritants, ethyl alcohol (EtOH) and urea.Fasted adult male Swiss mice in groups of 3 mice each received via esophageal intubation one of the following solutions for 15 minutes: distilled water, 145 mN NaCl, 10% EtOH, 10% EtOH + 100 mN HCl, 25% EtOH, 25% EtOH + 100 mN HCl, 45 mN NaCl + 100 mN HCl, 900 mN urea, or 1500 mN urea.
Central Monoamine Neurons
Authors: Hökfelt T. 
Published: June 2020

Considerable interest has been focused on a group of biologically highly active substances often called biogenic monoamines including dopamine (DA), noradrenaline (NA), adrenaline (A) and 5-hydroxytryptamine (5-HT). Initially their existence in various non-neuronal cell systems and their role as hormones called for extensive research efforts. Subsequently their possible involvement in neurotransmission both in the peripheral and central nervous system has been studied in laboratories all over the world.Today a wide variety of methods are available for studies on monoamine neurons among others histochemical techniques at the light and electron microscopic level. These techniques have been of importance not only for identification and mapping of such neurons but also for the understanding of their physiological role(s) e.g. in brain function.
Measurements of Single-Stranded RNA From Foot-and-Mouth Disease Virus
Authors: Breese Sydney S. , Bachrach Howard L. 
Published: June 2020

In the continuing study of the physical and chemical properties of purified foot-and-mouth disease virus (FMDV), particles were treated to release RNA strands by dialysis against demineralized distilled water. The RNA strands were mounted by loop drop on formvar carbon coated specimen grids pretreated with 0.1% bovine plasma albumin to give a protein spreading surface. Dilutions were made in demineralized distilled water to achieve the best concentration for subsequent measurements. Specimen grids were rotary shadowed at low angle with uranium. 2.5 to 3.0 X prints of electron micrographs taken of random fields at 8,000 to 11,000 X were used for measurements with a map-measuring device.Samples were selected from supplies in long term storage which had been made according to methods outlined previously.
Manchette Microtubules of Mouse Spermatids and their Resistance to Pepsin Digestion
Authors: Wolosewick John J. , Bryan John H. D. 
Published: June 2020

The manchette is a transitory microtubular complex associated with a spermatid nucleus during the morphopoietic events of spermiogenesis. Behnke and Forer provided evidence for four classes of microtubules (mts) in crane fly spermatids, rat sperm tails and tracheal cilia. Their observations also included the Sertoli cell and spermatid tail mts in rat testis, but they failed to mention the manchette mts. This present paper points out the distinct difference in stability or resistance to pepsin digestion between the manchette mts and other microtubular elements in the seminiferous epithelium of the mouse.Testes of adult mice were removed from the’ animals after cervical dislocation and placed into 2.5% glutaraldehyde/Millonig's phosphate buffer (pH 7.2). Testicular capsules were gently split and separated, thus exposing the tubules. After 15 min.
The Ultrastructural Demonstration of a Fixative-Stable Dehydrogenase Acting on Leuco Nitroxyl Analogs
Authors: Shannon W. Allen , Wasserkrug Hannah L. , Plapinger Robert E. , Lynm Dwo , Seligman Arnold M. 
Published: June 2020

A dehydrogenase which is relatively stable in formalin fixative and which reduces various leuco nitroxyl analogs is demonstrated cytochemically in rat myocardial, hepatic, and prostatic tubuloalveolar glandular cells.The various tissues were extricated and fixed in phosphate-buffered formaldehyde for up to 1 hr. The substrates used were products produced by catalytic hydrogenation of four different compounds with stable nitroxyl free radicals (Fig. 1). These compounds were 4-hydroxy-2,2,6,6, tetramethyl piperidine-l-oxyl (I), the urethane derivative (II) formed by reacting compound I with phenylisocyanate, 4-amino-2,2,6,6, tetramethyl piperidine-l-oxyl (III), and 2,2,6,6, tetramethyl piperidine-l-oxyl (IV). The nonosmiophilic tetrazolium salt, 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl) tetrazolium chloride (BSPT), which produces an insoluble, osmiophilic formazan upon reduction, was used as the electron acceptor at pH 7.4. Following incubation in the reaction medium, the tissues were osmicated in 2% osmium tetroxide at 50°C for 2 hr.
Localization of RNA on Mitotic Chromosomes
Authors: Papsidero Lawrence D. , Braselton James P. 
Published: June 2020

Thin sections of aldehyde fixed Cyperus alternifolius root tips were stained with uranyl acetate, washed with EDTA, and poststained with lead citrate to selectively stain ribonucleic acid (RNA) containing structures. As previously shown by other investigators RNA containing structures appeared electron dense, while nuclear regions known to contain DNA appeared less electron dense or “bleached”. RNase treatment removed all nuclear structures staining for RNA; light microscopic cytochemistry (Azure B) was performed on 1-3 micron sections of plastic embedded material to confirm the enzymatic removal of RNA.Granular appearing fibrils with indistinct boundaries were observed at the periphery of bleached metaphase chromosomes (Fig. 1). These fibrils are similar to the ribonucleoprotein perichromatin fibrils observed by Monneron and Bernhard in interphase nuclei. Nucleolar remnants were also observed associated with metaphase chromosomes.
Epitaxially grown paraffin: An electron crystal structure analysis
Authors: Moss Barbara , Dorset Douglas L. 
Published: June 2020

Epitaxial crystal growth proceeds in a manner entirely different from solution- growth. By a careful two-dimensional lattice matching in the substrate and the material of interest, crystallization in a desired orientation may be obtain. The area of each single microcrystal will, of course, depend upon the crystallinity of the substrate and the possibility of different growth directions thereon.Epitaxy offers considerable advantages over solution growth, since resultant crystals give electron diffraction intensity data suitable for total structure determination. Crystallographic phasing techniques such as Patterson maps and direct methods rely upon the kinematic or single-scattering approximation. Their usefulness thus requires minimizing perturbations to the intensity data due to dynamical scattering and crystal bending. Diffracted beam amplitudes are most insensitive to crystal bends when the electron beam is parallel to a short unit cell dimension. Dynamical scattering effects are reduced if there are few repeat units in the beam direction, which requires very thin crystals. The value of this approach is illustrated with paraffin.
Phosphotungstic acid staining of latexes for transmission electron microscopy
Authors: Shaffer O. L. , El-Aasser M. S. , Vanderhoff J. W. 
Published: June 2020

Measurement of particle size and particle morphology by transmission electron microscopy (TEM) is important in the characterization of polymer latex systems. Special sample treatment methods have been developed to permit the study of latexes that present problems, such as low-glass-transition-temperature (Tg) and electron-transparent particles. Some of these methods include hardening and staining by osmium tetroxide or bromine of latexes that contain unsaturation, negative staining by uranyl acetate, and freezing of latexes with low glass-transition temperatures.We have recently found phosphotungstic acid (PTA) to be useful in both negative and positive staining of latex particles. As a negative stain, PTA can enhance the contrast between the electron-transparent particles and the dense PTA-stained background. This has been particularly useful with latexes such as poly(butyl acrylate), poly(ethyl acrylate), poly(ethylene), and other polymers of similar electron densities. As a positive stain, PTA can also react with the surface functional groups of particles, such as hydroxyl, carboxyl, and amine groups.
Faceted grain boundaries in Al2O3
Authors: Morrissey K. J. , Carter C. B. 
Published: June 2020

The occurrence of faceted grain boundaries in commercially produced Al2O3 is quite common. This type of boundary has been noted previously, but little structural information has been reported. The different types of faceted boundary include twin boundaries, special high-angle boundaries, and lowangle grain boundaries. Faceted interfaces between Al2O3 grains and secondphase particles have been briefly discussed elsewhere. The present work is concerned mainly with the crystallography of special high-angle boundaries and twins.The planes of the facets can be understood using the concepts of the O-lattice and the CSL, which have been successfully used to study metals and semiconductors. Wagner, Tan, and Balluffi have proposed the generalized CSL, in which the coincident lattice sites in the two grains need neither be identical nor be occupied by atoms. It is in this sense that the CSL model will be used in this work.
Microtomy of spherical Al2O3 powders
Authors: Jenkins E.J. , Tucker D.S. , Hren J.J. 
Published: June 2020

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.
The spatial resolution limit of electron lithography
Authors: Joy David C 
Published: June 2020

As the size of microcircuit elements continues to decrease it is important to attempt to determine what factors ultimately limit the width of the finest line that could be fabricated by electron lithography and conventional polymer resists. Since the line profiles in an exposed and developed resist are determined by the contours of equal absorbed energy density this can be done by modelling the scattering which occurs in the polymer. We consider here the idealised case of a thin resist layer supported on a substrate of negligible scattering power, and irradiated with a beam of electrons in the energy range 30 to 100 keV, and calculate the minimum line width attainable under these optimum conditions.In the absence of any backscattering from the substrate it might be expected that the energy deposition profiles would be determined by elastic scattering in the resist.
Electron diffraction study of hydrogenated amorphous SiC
Authors: Sabatini R. L. , Kampas F. J. , Vanier P. E. , Taftø J. 
Published: June 2020

Hydrogenated amorphous SiC (a-SiC:H) is a promising new solar cell material. In constrast to structural studies of amorphous Si and amorphous C, studies of amorphous SiC are rare. The main features of the diffraction patterns of amorphous Silicon and amorphous Carbon are two diffuse halos which for Si correspond to interatomic distances of about 2.35 Å and 3.85 Å and for C to 1.50 Å and 2.50 Å. These distances are close to the nearest interatomic distances present in the crystalline form of the same elements.Using 120 KeV electrons, we observe two pronounced halos also for a-SiC:H, similar to what is observed for pure Si and pure C. Figure 1 shows diffraction patterns from a-SiC:H and for comparison from Si and C.
Mismatch and misorientation at the precipitate/matrix interface in an Al-Zralloy
Authors: Porter Angus , Makin Louise , Ralph Brian 
Published: June 2020

Much of the hardening of high strength aluminium alloys containing zirconium results from the precipitation of the metastable γ'	(Al3Zr) phase (Ll2 structure, cube/cube related to the matrix). There exists some controversy in the literature as to the magnitude of the matrix (γ)-γ' misfit in Al-Zr alloys; the values reported range from 1% down to rather less than half this figure. In the present paper, the use of moire fringe imaging to study mismatch and misorientation between the γ and γ' lattice in a binary Al-Zr alloy will be considered. The advantages of this technique for the study of small second-phase particles are three-fold. The information obtained is specific to a single particle; the exact nature of the particle/matrix interface is unimportant, as long as the two lattices exhibit nearly coincident diffraction maxima; and mismatch and misorientation of particular sets of lattice planes can be determined from a single image.
AEM analysis of crystallization in Ti-based amorphous alloys
Authors: Pelton A.R. , Marshall A.F. , Lee Y.S. 
Published: June 2020

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2from the amorphous matrix.
Localization of immunolabels by electron microscopy and image averaging
Authors: Frank J. , Sizaret P.-Y. , Verschoor A. , Lamy J. 
Published: June 2020

The accuracy with which the attachment site of immunolabels bound to macromolecules may be localized in electron microscopic images can be considerably improved by using single particle averaging. The example studied in this work showed that the accuracy may be better than the resolution limit imposed by negative staining (∽2nm).The structure used for this demonstration was a halfmolecule of Limulus polyphemus (LP) hemocyanin, consisting of 24 subunits grouped into four hexamers. The top view of this structure was previously studied by image averaging and correspondence analysis. It was found to vary according to the flip or flop position of the molecule, and to the stain imbalance between diagonally opposed hexamers (“rocking effect”). These findings have recently been incorporated into a model of the full 8 × 6 molecule.LP hemocyanin contains eight different polypeptides, and antibodies specific for one, LP II, were used. Uranyl acetate was used as stain. A total of 58 molecule images (29 unlabelled, 29 labelled with antl-LPII Fab) showing the top view were digitized in the microdensitometer with a sampling distance of 50μ corresponding to 6.25nm.
Specimen heating stage with in-situ evaporator in UHV-STEM for the observation and characterization of monolayered superstructures
Authors: Ohtsuki M. , Schuler J.J. , Crewe A.V. , Ichinokawa T. 
Published: June 2020

In-situ evaporating experiments on solid surfaces become meaningful only when the evaporation takes place after the surface of the object is fully cleaned in ultra high vacuum (UHV). A specimen heating stage is usually used for the cleaning process.For the observation of single heavy atom superstructures at atomic resolution in UHV, we have constructed a new specimen heating stage equipped with an insitu evaporator. The device is built into the specimen ante-chamber of the high-resolution UHV-STEM as shown in Figures 1 and 2. The vacuum of the chamber has been tested at 4 × 10-10 torr. with two 20 ℓ/ sec ion pumps attached close to the chamber. The vacuum of the STEM column is better than 1 × 10-10 torr. The heating stage is built into the specimen holder so that direct heating of the specimen is possible. In the detail shown in Figure 2, a thin specimen is mounted between two supporting grids which are then fastened together by two semi-circular tantalum clips. These clips are also used as contacts which carry the current to heat the specimen directly.
Design of objective lens for 200-kV high-resolution electron microscopes
Authors: Tsuno K. , Honda T. , Harada Y. , Naruse M. 
Published: June 2020

Developement of computer technology provides much improvements on electron microscopy, such as simulation of images, reconstruction of images and automatic controll of microscopes (auto-focussing and auto-correction of astigmatism) and design of electron microscope lenses by using a finite element method (FEM). In this investigation, procedures for simulating the optical properties of objective lenses of HREM and the characteristics of the new lens for HREM at 200 kV are described.The process for designing the objective lens is divided into three stages. Stage 1 is the process for estimating the optical properties of the lens. Firstly, calculation by FEM is made for simulating the axial magnetic field distributions Bzc of the lens. Secondly, electron ray trajectory is numerically calculated by using Bzc. And lastly, using Bzc and ray trajectory, spherical and chromatic aberration coefficients Cs and Cc are numerically calculated. Above calculations are repeated by changing the shape of lens until! to find an optimum aberration coefficients.
Surface structures of platinum crystal films grown epitaxially on silver
Authors: Hines R. L. 
Published: June 2020

Ultrathin platinum crystals a few atom layers thick are expected to have a number of properties that might make them useful as test objects to characterize the structure of platinum surfaces of interest in catalysis. Previous experiments on surface structures of platinum crystal films have indicated a rough surface when platinum crystal films were prepared at growth rates of 0.1 nm/minute in an oil pumped vacuum system at a nominal pressure of 2 micro- Torr. For the experiments reported here the platinum crystal.s are grown at growth rates of 0.1 nm/minute in a vacuum of 0.05 microTorr in an ion pumped system. The ultrathin platinum crystals are grown by first depositing approximately 200 nm of silver on the surface of a freshly cleaved piece of mica held at 270 °C in a vacuum of 0.05 microTorr. Then the platinum is evaporated onto the clean silver surface with the silver substrate at a set temperature between 50	°C and 270 °C. Then a carbon layer approximately 10 nm thick is deposited on the platinum by carbon arc evaporation.
Radiation effects on minerals in the electron microscope
Authors: Veblen David R. , Buseck Peter R. 
Published: June 2020

Radiation damage is commonly the most important limiting factor in transmission electron microscopic studies of minerals. This is especially true for high-resolution TEM (HRTEM) investigations, which typically utilize a relatively large electron dose. Conversely, because of this requirement, HRTEM studies provide a good opportunity for observing the effects of radiation in the electron microscope on different minerals. In this contribution, we attempt to impose some chemical and structural order on observations of beam damage in minerals, mostly silicates, based on HRTEM investigations of a wide range of specimens over the past decade.Because reports of radiation damage rates in the TEM are typically anecdotal, with no fixed point of reference, we here limit our comparisons of rates to first-hand observations. These observations were made primarily at lOOkV in a JEOL JEM100B microscope, although some of the same systematics also have been noted in other instruments at voltages up to 200kV. In addition, experiments of others where part of a crystal structure damages selectively are discussed.
Electron-beam spreading in thin foils at 40keV
Authors: Stephenson T.A. , Loretto M.H. , Jones I.P. , Augustus P. 
Published: June 2020

Experiments have been performed to determine the effects of thickness, and crystallinity on beam spreading in thin foils. The experimental technique consists of measuring an incident and exit electron probe size as shown in Fig. 1. Beam spreading is defined as the difference between these two quantities. Results were compared with Monte Carlo calculations.Beam spreading experiments in single crystal silicon oriented positive of a 440 reflection have shown that the experimental measurements are adequately described by Monte Carlo calculations using Doyle and Turner elastic scattering cross-sections (Fig.2). The addition of an inelastic component via the Bethe continuous loss approximation produces an insignificant change. Adjustment for the generation and scattering of fast secondary electrons is reserved for future work.Two experiments were performed to elucidate the effects of crystallinity. The first involved single crystal silicon in which exit grobe size measurgments were performed with diffracting conditions s=+0.0027Å-1 and s=-0.0034Å-1 from 220 (Table 1). Since beam spreading is dependent on high angle scattering, these results are qualitatively consistent with the orientation dependence of high angle diffuse scattering.