bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dislocation structures and twinning in tungsten <110> single crystals
Authors: Subramanian Raja , Vecchio Kenneth S. 
Published: June 2020

Tungsten single crystals are brittle due to predominant twinning and crack formation at twin-twin intersections. Twinning and its influence on crack nucleation have been studied in detail. Despite the twinning, significant plastic deformation takes place by the generation and glide of dislocations. Hitherto uninvestigated dislocation structures and twin boundaries in tungsten <110> single crystals deformed quasistatically in compression have been studied using transmission electron microscopy.In compressed samples, cracks nucleate at twin-boundary intersections. Such a crack is indicated by an arrowhead in Figure 1 which shows an optical image of twin boundaries. Figure 2 shows a bright field (BF) image of a twin boundary (marked by an arrowhead). The inset in Figure 2 is the microdiffraction pattern taken at the twin boundary which shows a ∑3 coincidence site lattice (CSL) symmetry.
Direct observation of the flux line lattice in Al-doped YBa2Cu3O7-δ
Authors: Grigorieva I.V. , Midgley P.A. , Bagnall K.E. , Sasaki K. , Steeds J.W. 
Published: June 2020

There has been much interest in the effect of partial substitution of Cu atoms in YBa2Cu3O7-δ (YBCO) by dopant atoms such as Fe, Al and Co. It has been found that an increase in the doping level alters the structure of YBCO - the twin domain size drops to 30-100Å for x>0.025 and the domains form the so-called 'tweed' structure. HREM has confirmed that within the domains the structure remains orthorhombic but on a macroscopic scale is quasi-tetragonal. This, in turn, leads to a change in superconducting properties: a rapid decrease in the transition temperature Tc, critical current, etc.In the present contribution the first results are reported on the direct observation of the magnetic flux structure in YBa2(Cu1-xAlx)3O7-δ single crystals (x=0.04) which was also expected to be influenced by Al doping. The flux line (vortex) distribution was observed using the high resolution Bitter pattern technique which involves evaporation of fine ferromagnetic particles (both Fe and Co were used in our experiments) to ‘decorate’ vortices at the surface of a superconductor.
Characterization of Rh/Si multilayer structure by HREM and HAADF
Authors: Cheng Y. , Liu J. , Stearns M.B. , Steams D.G. 
Published: June 2020

The Rh/Si multilayer (ML) thin films are promising optical elements for soft x-rays since they have a calculated normal incidence reflectivity of ∼60% at a x-ray wavelength of ∼13 nm. However, a reflectivity of only 28% has been attained to date for ML fabricated by dc magnetron sputtering. In order to determine the cause of this degraded reflectivity the microstructure of this ML was examined on cross-sectional specimens with two high-resolution electron microscopy (HREM and HAADF) techniques.Cross-sectional specimens were made from an as-prepared ML sample and from the same ML annealed at 298 °C for 1 and 100 hours. The specimens were imaged using a JEM-4000EX TEM operating at 400 kV with a point-to-point resolution of better than 0.17 nm. The specimens were viewed along Si [110] projection of the substrate, with the (001) Si surface plane parallel to the beam direction.
EM of rapidly solidified permanent magnets
Authors: Mishra Raja K. 
Published: June 2020

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.
AEM study of reacted surface layer of borosilicate nuclear waste glasses
Authors: Wang L.M. , Kaser S.A. , Ewing R.C. , Bates J.K. 
Published: June 2020

Analysis of the reacted surface layer of borosilicate glass is important to the understanding of the long term nuclear waste glass reaction process. The objective is to assess the simulated nuclear waste glass/water reaction pathway by identifying new crystalline phases that appear on the glass surfaces during the reaction. The results can be used to validate models generated to predict long-term performance of the nuclear waste glass under a range of conditions.In this study, extensive scanning electron microscopy (SEM) with qualitative energy dispersive x-ray spectroscopy (EDS) analysis, quantitative analytical and high resolution transmission electron microscopy (AEM and HRTEM) have been performed on two 202U glasses which were reacted in saturated water vapor for 14 and 23 days, respectively. In order to study the microchemical and microstructural changes with increasing depth from the reaction surface, TEM specimens were prepared in cross-section using the ultramicrotomy slicing technique similar to that described by Bates et al. In this process, small chunks containing the reacted surface layer and a thin layer of glass were first broken off from the sample surface and each of these chunks was then embedded in resin to form a block. Finally, thin sections, approximately 90 nm thick, were microtomed from these blocks and were transfered to copper mesh grids covered by holey carbon films for observation. AEM and HRTEM analyses were accomplished using a JEOL JEM-2000FX microscope attached with a Noran/TN-5500 EDS system at the University of New Mexico.
The 3-D substructure of RNA in nascent RNP granules: A novel application of osmium ammine-B staining and electron spectroscopic imaging
Authors: Olins Ada L. , Olins Donald E. , Shah Manesh B. , Levy Henri A. , Bazett-Jonest David P. 
Published: June 2020

RNA has a particulate substructure when visualized in situ with the nucleic acid specific stain osmium ammine-B (OA-B). In this study energy spectroscopic imaging (ESI) was used to enhance the contrast and collect the data for tomographic reconstructions.The Balbiani ring (BR) in the salivary gland polytene chromosomes of Chironomus tentans larvae furnishes a well known model for the structure of nascent m-RNA. This gland produces copious amounts of silk-like secretory proteins which are very large (106 daltons). The site of transcription, the BR, is easily recognized in the EM by its characteristic “puff” structure and electron-dense granular transcripts. Mature BR granules are 45-50 nm in diameter and can be easily observed within the nucleus and passing through nuclear pores.
Ultrastructural autoradiography of L6 skeletal-muscle cells exposed to a tritiated macrolide antibiotic (LY237216) in vitro
Authors: White S.L. , Jensen C.B. , Giera D.D. , Laska D.A. , Novilla M.N. , Hoover D.M. 
Published: June 2020

In vitro exposure to LY237216 (9-Deoxo-11-deoxy-9,11-{imino[2-(2-methoxyethoxy)ethylidene]-oxy}-(9S)-erythromycin), a macrolide antibiotic, was found to induce cytoplasmic vacuolation in L6 skeletal muscle myoblast cultures (White, S.L., unpubl). The present study was done to determine, by autoradiographic quantitative analysis, the subcellular distribution of 3H-LY237216 in L6 cells.L6 cells (ATCC, CRL 1458) were cultured to confluency on polycarbonate membrane filters (Millipore Corp., Bedford, MA) in M-199 medium (GIBCO® Labs) with 10% fetal bovine serum. The cells were exposed from the apical surface for 1-hour to unlabelled-compound (0 μCi/ml) or 50 (μCi/ml of 3H-LY237216 at a compound concentration of 0.25 mg/ml. Following a rapid rinse in compound-free growth medium, the cells were slam-frozen against a liquid nitrogen cooled, polished copper block in a CF-100 cryofixation unit (LifeCell Corp., The Woodlands, TX). Specimens were dried in the MDD-C Molecular Distillation Drier (LifeCell Corp.), vapor osmicated and embedded in Spurrs low viscosity resin. Ultrathin sections collected on formvar coated stainless steel grids were counter-stained, then individually mounted on corks. A monolayer of Ilford L4 nuclear emulsion (Polysciences, Inc., Warrington, PA) was placed on the sections, utilizing a modified “loop method”. The emulsions were exposed for 7-weeks in a light-tight box at 4°C. Autoradiographs were developed in Microdol-X developer and examined on a Philips EM410LS transmission electron microscope. Quantitative analysis of compound localization employed the point and circle approach of Williams; incorporating the probability circle method of Salpeter and McHenry.
Piroximone (MDL 19,205)-induced ultrastructural and biochemical changes in early adrenal medullary proliferative disease in rats
Authors: Sprinkle-Cavallo J. , Thompson F.Y. , Loudy D.E. , Dudley M.W. , Ogden A.M. , Gibson J.P. 
Published: June 2020

Piroximone is a cardiotonic agent (phosphodiesterase inhibitor) proposed for the treatment of congestive heart failure. The drug causes adrenal medullary proliferative disease (AMPD) in rats after 1 year or more of treatment. In this study we investigated the effects on adrenal chromaffin cells prior to the development of obvious hyperplasia. Male rats were administered 0, 300, or 600 mg/kg/day of piroximone in the diet for three months.For morphometry studies, adrenals from 5 rats/group were fixed in 10% formalin and stained with hematoxylin and eosin (H&E). For differentiation of chromaffin cell types, left adrenals from 5 rats/group were fixed in 2% glutaraldehyde and 4% EM grade formaldehyde and stained with Gomori's methanamine silver and also (after pretreatment with 2.5% potassium dichromate in 1% sodium sulfate) with H&E as well as toluidine blue. For electron microscopy studies, adrenal medulla from 5 rats/group was fixed in 5% glutaraldehyde with post-fixation in 4% paraformaldehyde.
Microscopic evaluation of structural changes in brittle, hydrated, gelatin capsules
Authors: Robson J. , Snow G. , Park J.Y. , Moretz R.C. , Krenkel H.-O. , Angel A. 
Published: June 2020

Gelatin capsules are a commonly used dosage form for prescription medications. Storage conditions as well as drug formulation can directly affect capsule integrity over time. Often, capsule brittleness following storage can be related to water loss. In this report an encapsulated drug formulation containing 77% anhydrous citric acid became brittle following two years of storage at 25° C/60% RH. However, Thermogravimetric data showed that capsule brittleness did not result from changes in water content. Both normal(without drug formulation) and brittle capsules contained 12% water. Microscopy was then applied to examine capsule walls to determine if the change in physical integrity could be related to a structural change.LM of normal capsules showed both the interior and exterior walls to be smooth, without indentations. SEM examination of the interior wall of the normal capsules revealed fairly smooth walls (Fig. 1). Sections of normal capsules examined with the TEM revealed intact walls with little variation between sections or capsules (Fig. 2). Examination of capsules stored for one year revealed interior surfaces stippled with particulate identified as active ingredient(AI) and citric acid. The particulate was not fused to the interior wall and no morphological changes were observed for the Al or citric acid when compared to known active/excipient morphology. In contrast, the interior wall of capsules stored for two years showed striking morphological changes. LM presented an eroded interior wall indicating a loss or redistribution of gelatin. TEM further illustrated that the structure of the capsule had been altered; subsurface pockets were seen throughout the section of the capsule (Fig. 3). TiO2 particles, a whitener used in the capsules, were redistributed in the areas where degradation was apparent. SEM presented irregular interior surfaces with abundant particulate fused to the capsule wall (Fig. 4). The fused particulate presented structure which contrasted with the known morphology of the citric acid and Al starting materials indicating that dissolution and recrystallization had taken place. Comparable crystal structure was determined when Al and citric acid were dissolved in water and allowed to recrystallize at room temperature.
Plants in response to copper toxicity
Authors: Tsay Ching-Chiann , Huang Yu-Fen , Wang Li-Wen , Chen Yung-Reui 
Published: June 2020

Plant response to heavy metal in soil varies with plant species, their developmental stages and the ways of pollution. Plants seedlings studied by morphological and biochemical markers through hydroponic culture can provide a way for screening Cu-tolerant plants which are potential plants for removing copper from Cupolluted soil.Seeds of tested plants obtained from both commercial sources and open field of Cu-polluted regions were germinated in petri dishes. Ten-day-old seedlings were transferred to a Hoagland's solution containing different concentrations of copper. Tested plants with symptoms of copper toxicity were collected as the materials for microscopic observations with OM and TEM, and for isozyme analysis with PAGE electrophoresis.
Limits for high-resolution electron microscopy of inorganic materials?
Authors: Smith David J. 
Published: June 2020

The era of atomic-resolution electron microscopy has finally arrived. In virtually all inorganic materials, including oxides, metals, semiconductors and ceramics, it is possible to image individual atomic columns in low-index zone-axis projections. A whole host of important materials’ problems involving defects and departures from nonstoichiometry on the atomic scale are waiting to be tackled by the new generation of intermediate voltage (300-400keV) electron microscopes. In this review, some existing problems and limitations associated with imaging inorganic materials are briefly discussed. The more immediate problems encountered with organic and biological materials are considered elsewhere.Microscope resolution. It is less than a decade since the state-of-the-art, commercially available TEM was a 200kV instrument with a spherical aberration coefficient of 1.2mm, and an interpretable resolution limit (ie. first zero crossover of the contrast transfer function) of 2.5A.
Microtwinning Evidence For The Apparent Five-Fold Symmetry in T2(Al6Li3Cu)
Authors: Vecchio Kenneth S. , Williams David B. 
Published: June 2020

Since the discovery in 1984 by Shechtman et al. of crystals which display apparent five-fold symmetry, extensive effort has been given to establishing a theoretical basis for the existence of icosahedral phases (eg.2.). Several other investigations have been centered on explaining these observations based on twinning of cubic crystals (eg.3.). Recently, the existence of a stable, equilibrium phase T2Al6 Li3Cu) possessing an icosahedral structure has been reported in the Al-Li-Cu system(4-6).In the present study an Al-2.6wt.%Li-l.5wt.%Cu-0.lwt.%Zr alloy was heat treated at 300°C for 100hrs. to produce large T2 precipitates. Convergent Beam Electron Diffraction (CBED) patterns were obtained from two-fold, three-fold, and apparent five-fold axes of T2 particles. Figure 1 shows the five-fold symmetric zero layer CBED pattern obtained from T2 particles.
The energy dependence of axial coherent bremsstrahlung in the high-voltage electron microscope
Authors: Butler J.H. , Spence J.C.H. , Humphreys C.J. , Johnson E.A. 
Published: June 2020

Coherent bremsstrahlung (CB) emitted by 200 to 1000 keV electrons traversing oriented silicon crystal targets has been detected using a high voltage electron microscope equipped with an energy dispersive x-ray spectrometer. In this energy range there 1s a strong dependence on the relativistic properties of the Incident electrons: β = v/c varies from about 0.69 (E = 200 keV) to 0.94 (E = 1 MeV); whereas in higher energy accelerator CB experiments β remains close to unity and the variation of any particular peak energy with respect to E is small.This work concentrates on the detection of the “type B” CB which arises from “juddering” of the electron beam as it traverses successive planes of atoms and is prominent 1n directions transverse to the beam. These spectra exhibit harmonics, peak energies which are Integral multiples of a basic value, which can be ascribed to Umklapp processes in successively higher order Laue zones (H0LZ) of the reciprocal lattice.
Valence shell excitations in silicon compounds using ELS
Authors: Skiff W.M. , Carpenter R.W. , Lin S.H. 
Published: June 2020

Variations in the valence-shell excitation cross section, as a function of energy loss, across the series of silicon compounds, Si, SiC, Si3N4, and SiO2, were studied using electron energy loss spectroscopy. These variations can be explained in terms of elemental and chemical effects.Each spectrum was collected using a 100keV beam, a 10mrad collection half-angle, and a 5mrad beam divergence, at 0.7eV resolution, in a Philips 400 FEG, with the thin specimen in kinematic diffracting conditions. The background-stripped Si L edge was fitted to a calculated Si L atomic ionization cross section, hence normalizing the spectrum to cross section per Si atom. The spectrum was finally converted to that per valence electron by using the stoichiometry and the number of valence electrons per formula unit.
In situ fracture of SiC-whisker-reinforced Al203
Authors: Angelini P. , Becher P. F. 
Published: June 2020

Dynamic in situ fracture experiments were performed on SiC-whisker-reinforced Al203 to determine the mechanisms responsible for the observed increase in fracture resistance. Observations of both stationary as well as moving crack tips while the specimen was under load showed that fracture resistance is due to debonding near the whisker matrix interface, crack deflection, pinning, and bridging by SiC whiskers.Two types of hot pressed specimens were evaluated. One contained 20 vol % SiC whiskers as well as 0.5 wt % MgO and 2.0 wt % Y203 as sintering aids. Another was fabricated with only 5 vol % SiC whiskers with no sintering aids. Specimens were prepared for TEM by cutting the material perpendicular to the hot pressing axis, grinding, polishing, dimpling, and argon ion milling.
Energy loss and x-ray analysis of major constituents in silicon oxynitride ceramics
Authors: Braue W. , Skiff W.M. , Carpenter R.W. , Ma H. 
Published: June 2020

Silicon Oxynitride (Si2N2O) is an orthorhombic phase that often occurs as a minor phase In Si3N4-base structural ceramics. It is thought to form as a result of oxygen surface contamination of the constituent powder particles, usually exhibits a rod or plate morphology and may react with sintering aids or impurities in the system. The structure of Si2N2O is a network of distorted Si-centered SiN3O tetrahedra in which the tetrahedral environment of the Si is similar to its environment in Si3N4 and SiO2. The average Si-N bond length is smaller, compared to both Si3N4 allotropes, with an Si-0 bond length typical of most silicates. EELS spectra of Si3 N4, and SiO2 are well known.Here we present the first results of a high resolution EELS study to compare the energy loss core edges of Si, 0 and N in Si2N2O to the corresponding edges in Si3N4 and SiO2.
TEM investigation of extended defects in hexagonal BaTiO3
Authors: Eibl O. , Pongratz p. , Skalicky P. , Mazur J.H. 
Published: June 2020

Barium titanate is known mostly for the ferroelectric, piezoelectric and dielectric properties of its tetragonal phase. Above 1330°c in strongly reducing atmosphere (pO2 = 10-20 bar) BaTi03 transforms from the cubic to the high temperature hexagonal polymorph preserved at room temperature as a metastable phase containing defects which are a subject of the present investigation. The hexagonal phase consists of close packed (Ba-03) planes and Ti planes stacked along the [001] direction resulting in a ABCACB stacking sequence. In this structure TiO6 octahedra are linked either by common corners or common faces. A high resolution image of the projected structure along [100] is shown in Fig. 1.Stacking faults are observed on (001) planes. The density of faults is l-2xl06 m-1 and the faults are extending over the whole grain size which is a few hundred microns. Partial dislocations usually 100 nm apart are found in the fault plane.
Near-Field Scanning Optical Microscopy
Authors: Betzig E. , Isaacson M. , Lewis A. , Lin K. 
Published: June 2020

The spatial resolution of most of the imaging or microcharacterization methods presently in use are fundamentally limited by the wavelength of the exciting or the emitted radiation being used. In general, the smaller the wavelength of the exciting probe, the greater the structural damage to the sample under study. Thus, the requirements of minimal sample alteration and high spatial resolution seem to be at odds with one another.However, the reason for this wavelength resolution limit is due to the far field methods for producing or detecting the radiation of interest. If one does not use far field optics, but rather the method of near field imaging, the spatial resolution attainable can be much smaller than the wavelength of the radiation used. This method of near field imaging has a general applicability for all wave probes.
Doping of vanadium alloys with helium using tritium
Authors: Braski D. N. 
Published: June 2020

Vanadium alloys are currently being evaluated for possible future application as a structural first wall for a fusion reactor. Major concerns are the displacement damage and high rates of helium production in a first wall caused by the 14 MeV neutrons from the plasma. To study the effect of helium on the microstructure and to simulate its effect in irradiation experiments, various vanadium alloys have been doped with helium using the “tritium trick” procedure.Vanadium alloy specimens were heated at 400°C in a stainless steel retort with tritium at 53 kPa (400 torr). Helium concentration was controlled by holding the specimens under these conditions for a predetermined time to allow the tritium, which is quite soluble in vanadium, to diffuse into the material and transmute to 3He. The process was stopped by reducing the pressure and increasing the temperature in the retort to 700°C. This removed the remaining tritium from the specimens and left the insoluble 3He behind in the microstructure.
The interface between sipos and silicon
Authors: Posthill J.B. , Ozguz V.H. , Mortman J.J. 
Published: June 2020

Semi-insulating polycrystalline silicon (SIPOS) is formed by introducing oxygen during the deposition of silicon. SIPOS is currently used as a passivation layer for high voltage devices. More recently, it has also been introduced as an emitter material for bipolar transistors. Electrical properties are expected to be influenced by many factors, some of which are: dopant type and concentration, the grain size and contiguity of the silicon crystals, and the microstructure of the SIPOS/Si interface. This contribution reports cross-section TEM results obtained from samples that have undergone different silicon wafer preparation prior to SIPOS deposition and different post-deposition rapid thermal anneal (RTA) treatments.One set of silicon wafers was dipped in buffered HF immediately prior to SIPOS deposition in order to remove any oxide. A thin chemical oxide ∼1 nm thick was intentionally left on the other set of wafers.