bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Ni/Ni3Al diffusion-couple interface by AEM and HREM
Authors: Watanabe M. , Horita Z. , Smith David J. , McCartney M.R. , Sano T. , Nemoto M. 
Published: June 2020

The interface between the Ni-rich solid solution phase (γ phase) and the intermetallic phase (γ'phase) with the Ll2-ordered Ni3Al structure plays an important role in the strengthening of Ni-based two-phase alloys such as superalloys. In this study, we have examined microstructure and diffusional phenomena across the ϒ/ϒ' interface by analytical electron microscopy (AEM) and high resolution electron microscopy (HREM).Fully annealed high-purity Ni (99.9%) was coupled with Ni-25mol%Al and subjected to diffusion anneal at temperatures of 1073 and 1173K. Thin specimens were prepared from these diffusion couples by careful cutting, grinding, electro-polishing and ion-milling, details of which are described elsewhere. We used three different types of electron microscopes: (a) JEM-2000FX (at 200kV) for measurements of the overall concentration gradient with a probe size of ∼20nm, microstructure observations and selected area diffraction analyses, (b) EM400T-FEG (at 100kV) for high spatial resolution micro-chemical analysis with a probe size of ∼3nm, and (c) JEM-4000EX (at 400kV) for observations of lattice images at the interface. Characteristic x-ray lines of Ni Kα, Al Kα, and Ni La were measured by energy dispersive x-ray spectrometers with a Be-type window which were attached on both JEM-2000FX and EM400T-FEG. Ni Kα and Al Kα lines were used for the determination of compositions, and Ni Kα and Ni Lα lines were for the determination of local thicknesses. X-ray absorption corrections were made by the differential x-ray absorption (DXA) method when determining concentration gradients and by the extrapolation method when determining k-factors.
Phase transformations in rapidly solidified Nd33Fe77 alloy
Authors: Zaluska A. , Liao L.X. , Chen X. , Altounian Z. , Ström-Olsen J.O. 
Published: June 2020

Nd-Fe alloys are important for high performance permanent magnets (usually in combination with B, C or N) and a knowledge of the metastable and stable phases of the system is necessary for the development of these new materials. An effective way to investigate such phases is by crystallizing an amorphous precursor.Amorphous ribbons of the binary alloy Nd33Fe77 were produced by melt-spinning. The phase transformations induced by heat treatment of the as-quenched ribbons is complex involving first the production of metastable phases followed by subsequent transformation into stable phases and finally eutectic melting.
Analysis of ceramic-metal braze alloy systems by EPMA
Authors: Hefter J. , Werber G. , Kang S. 
Published: June 2020

The development of advanced material systems for brazing silicon nitride-based ceramics to various metallic substrates (e.g. Incoloy 909 Fe-based superalloy) depends strongly upon the structural and chemical nature of a number of interfaces (ceramic-braze and braze-metal) as well as on the braze microstructure. Such systems are being considered for joining ceramic rotors to metal shafts in automotive applications. Coatings may be deposited on the ceramic surface prior to brazing to promote braze adhesion and wetting. These materials further complicate the resulting microstructure of the system.Electron probe microanalysis can play a substantial role in the elucidation of the resulting braze microstructures since both phase morphology, distribution, and chemistry may be obtained. Here, a PY-6 silicon nitride ceramic was brazed to Incoloy 909 by using a Mo interlayer brazed between the two materials, Figure 1. The braze is a Au-5Ni-2Pd solid solution system and was used as a 50 μm thick foil. Brazing was accomplished by holding the specimen at 1080 °C for 10 min in a vacuum furnace. A cross-section for EPMA analysis was obtained by normal metallographic methods. All EPMA data were collected using a JEOL JXA-840 coupled with a Noran 5402 EDS system. Digital, background-subtracted maps (256x256, 0.1 s/point) were collected using “IPP” software.
Complete HREM autotuning using automated diffractogram analysis
Authors: Krivanek O.L. , Fan G.Y. 
Published: June 2020

Complete autotuning of a high resolution electron microscope (HREM) aligns the electron illumination along the true axis of the objective lens (autoalignment), corrects the astigmatism (autostigmation) and sets the focus to a user-selected value (autofocusing). We have developed a new method which performs complete autotuning with just 3 images, and is faster and more accurate than the best human operators.Our method uses diffractograms of images of amorphous materials recorded with a slow-scan CCD camera (SSC) at magnifications of 200-800 kx. Diffractograms computed from SSC images have better quality than diffractograms formed in an optical bench from a micrograph recorded on film, and are the perfect starting point for the autotuning procedure. The diffractograms are analyzed by an automatic routine described previously. The analysis yields the defocus, astigmatism, and astigmatism direction, and the computer then applies the needed corrections to the microscope. A single image recorded in typically 0.5 - 1.0 sees plus about 8 sees of processing time on a Macintosh Quadra are therefore sufficient for complete autostigmation and autofocusing. This time is likely to decrease in the future simply because of the increasing power of new generations of computers.
Defocus ramp correction in spot-scan imaging
Authors: Downing Kenneth H. 
Published: June 2020

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.
Low-voltage high-resolution SEM investigations of novel macromolecular liquid crystals
Authors: Adams W.W. , Vezie D.L. , Thomas E.L. 
Published: June 2020

The ability to visualize detailed 3-dimensional surface topology with SEM at low voltage and high resolution holds profound promise for analyzing liquid crystal textures, both in polymers and other macromolecular forms. Director textures, domain boundaries, and defects such as inversion walls, disclinations and dislocations can now be easily visualized with this technique. Studies concerning the effects of shear flow and magnetic fields on these defects are currently under way.Resolution of 4.0 nm at 1.0 keV is now possible with commercial SEM's, which incorporate the latest advances in lens design optimized for low voltage operation, and use high brightness, low energy spread field emission electron guns. The low energy spread of the field emission gun reduces chromatic aberration effects and facilitates successful operation at low keV. Low voltage operation provides dramatically improved image contrast due to the smaller beam/sample interaction volume and also greatly reduces sample charging artifacts. By operating at near crossover conditions, the need for coating nonconducting specimens with a conducting layer of metal or carbon is greatly reduced or eliminated.
Rotations and transformations in quasimelting
Authors: Narayanaswamy D. , Marks L.D. 
Published: June 2020

Morphological fluctuations of a quasimolten particle have been analyzed using high resolution electron microscopy (HREM) to determine the order and relative importance of rotations, translations and morphological transformations.Small gold particles evaporated onto a holey silicon monoxide support were examined in a conventional 300kV HREM at an electron beam flux of 25A/cm2. Single particles were observed over a period of time. The particle behavior was recorded in real time onto a Sony 8mm videotape recorder, at the rate of 30 frames per second, via a Gatan TV camera. The acquired images were further processed using SEMPER software on an Apollo workstation. The image frames were analyzed by employing a data reduction scheme. A basis set of good images were selected from the entire recording, and completely characterized on the lines of earlier workers. The set was found to consist of four distinct morphologies in various orientations. Samples of the morphologies isolated are shown in Fig. 1.
Z-band cross sections in rigor skeletal muscle have similar detailed structures as in tetanized muscle
Authors: Goldstein M. A. , Schroeter J. P. , Edwards R. J. 
Published: June 2020

We have previously shown that two structural states of the Z-band in muscle cross-sections are related to the contractile state of the muscle. In skeletal muscle at rest, the z-band is in the small square (ss) form, but tetanized muscle exhibits the basket weave (bw) form. Recently, we have shown that skeletal muscle in rigor also exhibits the bw form and dimensions.We have used two dimensional computer enhancement techniques on digitized electron micrographs to compare the detailed structure of the tetanized and rigor Z-band lattices. Both lattice averaging and Fourier filtering techniques were used, with enhanced images displayed as grey-scale projections, as contour maps, and in false color. There is only a slight difference between the lattices produced by the two different enhancement techniques. Thus, information in the enhanced images is not likely to be an artifact of the enhancement algorithm.
3-D reconstruction and analysis of mammalian mitotic spindle structure
Authors: McDonald Kent , Mastronarde David , Ding Rubai , O'Toole Eileen , McIntosh J. Richard 
Published: June 2020

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.
Ultrastructural study of experimental duodenal ulcer in a new animal model
Authors: Bui H.X. , delRosario A. , Abdulla M. , Ballouk F. , Bajakian V. , Lee C.Y. , Ross J.S. 
Published: June 2020

Various animal models have often been utilized as the basis of studies of the pathophysiology of peptic ulcer disease, however the ultrastructural changes in the evolution of duodenal ulcers produced in experimental animals have not been well elucidated. Utilizing a surgical method developed for the study of gastric ulcers we have established an experimental duodenal ulcer production technique in the rat which is highly reproducible and readily standardized. In the following time sequence study of experimental duodenal ulcers we present the ultrastructural features of ulcer induction and evolution.Duodenal ulcers were produced in 150-200 gram male Sprague Dawley rats by application of 50% acetic acid for 30 seconds through a 3 mm polyethylene tube to the serosa 1.0-1.5 cm distal to the pyloric sphincter. Routine transmission and scanning electron microscopy were performed on duodenal specimens at specific time points subsequent to surgical ulcer generation. Thin sections were stained with uranyl acetate and lead citrate and examined with a Phillip's EM 300 transmission electron microscope. For SEM, specimens were post-fixed in 2% osmium for two days, coated with gold/palladium and examined with JEOL JSM-6100 scanning electron microscope (JEOL, Inc., Peabody, MA).
Immunotactoid glomerulopathy: Recurrence of disease in renal transplant
Authors: Price George , Moses Gregory , Holcomb Allen , Cerezo Lizardo 
Published: June 2020

Immunotactoid glomerulopathy (ITG) is a disease of the kidney, first described 1980. It is characterized by the specific deposition of immunoglobulin in the renal glomeruli, producing diffuse mesangial expansion similar to that commonly noted in the sclerosing process of amyloidosis. However, these patients do not exhibit the clinical symptoms of patients with extra renal, or systemic disease, and therefore have a better prognosis. The demonstration by electron miscroscopy of fibrillar deposits that are thicker than that of amyloid is crucial to the diagnosis.The association of this disease to an autoimmune response is demonstrated by the immunofluorescent staining of antihuman IgG and C3 to the affected glomeruli. Other immunoglob ins may be implicated, but are not as common.
Fish kidney cell line in response to heat shock
Authors: Tung Li-Chu , Chen Yung-Reui , Chen Shiu-Nan , Kuo Guang-Hsiung 
Published: June 2020

In the present study, the ultrastructural changes of BPK cells, a fibroblast-like cell line, derived from the kidney of juvenile black porgy Acanthopagrus schlegeli, under heat shock treatment are described.The BPK cells were maintained in L-15 medium supplemented with 10% fetal calf serum and 0.15 M NaCl at 28|C2. The heating was carried out in precalibrated water baths. Monolayers of cells, grown on coverslips in parafilm-sealed petri dishes were submerged under water for 30 min at 40|C treatments. Cells were fixed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer supplemented with 6.6% sucrose, postfixed in 1% OsO4 and flat embedded in Spurr’s resin. Silver section were cut parallel to the substratum, stained with uranyl acetate and Reynold’s lead citrate, and examined in a Hitachi H-600 electron microscope at 75 KV.
Enhanced information from biological materials through technological improvements in cryo-electron microscopy
Authors: de Jong Marc J.C. , Busing Wim M. , Otten Max T. 
Published: June 2020

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.
Cytochemical localization of glycogen synthase activity in rat liver
Authors: Michaels John E. , Cardell Robert R. 
Published: June 2020

Glycogen synthase (GS) is the rate limiting enzyme for liver glycogen synthesis and its activity varies with the phosphorylation state of the enzyme. The current study focused on changes in the intralobular patterns of distribution of cytochemically localized GS activity during glycogen synthesis.Normal and adrenalectomized (ADX) rats were fasted overnight to reduce liver glycogen to minimal levels. Fasted ADX rats received 2 mg dexamethasone (DEX) 0-8 h prior to sacrifice to stimulate glycogen synthesis. Liver was removed, rapidly frozen in isopentane cooled in liquid nitrogen, then cryostat sectioned. GS activity was localized histochemically by 3 h incubation in medium containing both UDP-glucose and glucose 6-phosphate. Glycogen was formed as reaction product. Control incubations omitted the substrate. Two stains were used to identify glycogen: 1) iodine staining of the incubated sections was rather specific for the newly formed glycogen (Figs. 1-6), whereas 2) periodic acid-Schiff (PAS) stained both native and nascent glycogen.
The application of environmental SEM to marine biology
Authors: Ray Richard 
Published: June 2020

Preparation of marine biological material for standard scanning electron microscopy (SEM) requires extensive manipulation, including fixation, removal of salts, dehydration, and either air drying or critical-point drying because the SEM operates at high vacuum. Non-conducting samples including biological material must be coated with a conductive film of metal before the specimen can be imaged.The Electroscan Corporation (Wilmington, MA) recently introduced a new development in SEM technology—the environmental scanning electron microscope (ESEM). This instrument uses a unique secondary electron detector capable of forming high resolution images at pressures in the range of 0.1 to 20 torr. If water vapor is used as the specimen environment, wet samples including wet biofilms can be observed directly. This paper illustrates the use of the ESEM to view bacteria, dinoflagellates, and diatoms on surfaces.
Overcoming beam-induced specimen motion: A major advance in improving image contrast for organic specimens
Authors: Downing Kenneth H. 
Published: June 2020

Electron microscopists have for some time been progressing toward the goal of atomic resolution of the structure of several proteins; these are proteins that are available in thin crystals that can produce electron diffraction patterns extending beyond 3 Å. The diffraction patterns demonstrate that the specimens themselves should be amenable to high resolution studies. Progress in the solution of these structures has been limited, however, because it has not yet been possible to obtain images of the crystals which have the same quality as the diffraction patterns. Fourier transforms of the images show diffraction spots which decrease in intensity with increasing resolution much faster than do the corresponding electron diffraction patterns, recorded under essentially the same conditions.The source of this limitation in image quality is clearly not the electron microscope. Materials scientists routinely achieve the resolution which structural biologists still strive for.
Parameterization of the mean free path for inelastic scattering of fast electrons
Authors: Egerton R. F. , Cheng S. C. , Malis T. 
Published: June 2020

The areas, Iz and It, under the zero-loss peak and under the entire energy-loss spectrum (of a sample of thickness t) are related by the formula:t/ƛ(β) = ln (It/Iz) (1)where ƛ(β) is the inelastic mean free path for all energy losses and for scattering into the collection aperture, of semiangle β. We have used Eq.(l) to experimentally determine ƛ(β) by electron energy-loss spectroscopy of specimens of known composition and thickness. In the case of crystalline samples, the local thickness t was measured by convergent-beam diffraction. In the case of evaporated thin-film specimens, the average thickness was obtained by accurately weighing the substrate before and after deposition. The energy-loss spectroscopy was carried out in CTEM mode with incident energies Eo between 20keV and 120keV, and with collection semiangles in the range 0.2 mrad to 100 mrad.
A TEM study of electron tunneling in biological macromolecules
Authors: Panitz J. A. 
Published: June 2020

Tunneling is a ubiquitous phenomenon. Alpha particle disintegration, the Stark effect, superconductivity in thin films, field-emission, and field-ionization are examples of electron tunneling phenomena. In the scanning tunneling microscope (STM) electron tunneling is used as an imaging modality. STM images of flat surfaces show structure at the atomic level. However, STM images of large biological species deposited onto flat surfaces are disappointing. For example, unstained virus particles imaged in the STM do not resemble their TEM counterparts.It is not clear how an STM image of a biological species is formed. Most biological species are large compared to the nominal electrode separation of ∼ 1nm that is required for electron tunneling. To form an image of a biological species, the tunneling electrodes must be separated by a distance that would normally be too large for a tunneling current to be observed.
A TEM investigation of silicon nitride whiskers
Authors: Roy Tapan 
Published: June 2020

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.
Scanning X-Ray Microscopy
Authors: Rarback H. 
Published: June 2020

From a theoretical viewpoint, a scanning transmission soft x-ray microscope is an excellent instrument for imaging unmodified thick (1 - 10μm) biological specimens at moderate (10 - 100 nm) resolution . Such specimens include wet intact cells, cell cultures, and isolated organelles. It may even be possible to study the dynamics of a living cell at such resolution, a feat beyond the ability of most competing techniques.Two basic features of the scanning x-ray microscope account for these theoretical advantages: the soft x-ray photon is well matched to such specimens, and the scanning technique minimizes the specimen damage which will probably set the achievable resolution limit for such specimens. X rays with wavelengths between 1 and 10 nm have a penetration depth of the order of 1 μm in wet biological material; the predominant interaction is photoelectric absorption which simply removes a photon from the incident beam without degrading the resolution.