bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging cellular dynamics using scanning laser confocal microscopy
Authors: Cooper M.S.
Published: June 2020

In recent years, the ability to image morphological dynamics and physiological changes in living cells and tissues has been greatly advanced by the advent of scanning laser confocal microscopy. Confocal microscopes employ optical systems in which both the condenser and objective lenses are focused onto a single volume element of the specimen. In practice, galvanometer-driven mirrors or acousto-optical deflectors are used to scan a laser beam over the specimen in a raster-like fashion through an epifluorescence microscope. The incident laser beam, as well as the collected fluorescent light, are passed through pinhole or slit apertures in image planes that are conjugate to the plane of the specimen. This method of illumination and detection prevents fluorescent light which is generated above and below the plane-of-focus from impinging on the imaging system's photodetector, thus rejecting much of the fluorescent light which normally blurs the image of a three-dimensional fluorescent specimen.
Electron probe x-ray microanalysis of subcellular ion transportin situ
Authors: Somlyo Avril V. , Somlyo Andrew P.
Published: June 2020

Electron probe x ray microanalysis [EPMA] provides quantitative information within a single spectrum about elements of biological interest with atomic number of 11 or greater. Therefore, the transport of ions and their accompanying co and counter ions across organelle membranes can be studiedin situby sampling within and adjacent to the intracellular organelle of interest under resting and stimulated conditions.

EPMA is based on the fact that the ionization of atoms by fast electrons generates x rays having energies characteristic of the excited atoms. The interaction of incident fast electrons with atomic nuclei generates a background of continuum x rays. Elemental quantitation of ultra thin sections with EPMA is generally based on the linear relationship between elemental concentrations and the ratio of the number of characteristic/continuum. The use of this principle, together with the appropriate standards for calibration, has been the most successful approach for quantitative biological EPMA. The spatial resolution of EPMA at present is better than 10 nm and the practical limit of sensitivity for detecting calcium, (albeit with high electron dose), is approximately 0.3 mmol/kg dry wt. Two modes of data collection are utilized: fixed probe analysis of a region of interest or a scanning probe mode, where an x ray spectrum is collected at each picture point, to obtain quantitative elemental x ray maps. To preserve the morphology and thein vivodistribution of diffusible elements, we prepare specimens by rapid freezing in sub cooled Freon or, more recently with a Lifecell CF100 metal are mirror device; thin sections cut at -130 °C to -160 °C on a Reichert cryoultramicrotome. Msec time resolution of physiological are events can be achieved by freeze trapping.
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.
Microstructure in shaped charge cones and its relationship to plastic instability and jet performance
Authors: Gurevitch A. C. , Murr L. E. , Niou C-S. , Advani A. H. , Grieves J. R. , Zernow L.
Published: June 2020

When a plane wedge of relatively thin plates of metal or a cone of sheet metal is backed up on the outside with explosive and detonated, the walls of these wedge-type geometries are caused to collapse so that the metal is forced to concentrate on the corresponding axis. In the case of a plane wedge a planar jet of metal is formed which conceptually approximates the blade of a sword moving at speeds up to 30,000 ft./sec. (∼ 9 km/s). When strategically placed on structural girders of a building, demolition can be achieved in a remarkable collapse process which can be carried out in the midst of a city. As a metal cone, the ensuing axial jet can punch a hole the size of a U.S. quarter in more than a meter of steel armor. These shaped charge jets, especially those originating from explosively collapsed metal cones, also exhibit remarkable mechanical behavior: metals such as copper are stretched nearly 900 percent (in the solid state) before necking into small particulates like a non-viscous fluid breaking up into small droplets. As it turns out this jet breakup, and its corresponding armor penetrating ability, seems to be dependent upon the initial metallurgical processing of the cone, especially the initial grain size in the case of copper. However since the jet break up for copper seems to occur over a very narrow range of grain sizes (between about 35 and 45 μm), more subtle features of the cone microstructure could be controlling the jet performance.
Electron holography observation of flux-line dynamics
Authors: Yoshida Takaho , Matsuda Tsuyoshi , Tonomura Akira
Published: June 2020

With the sufficient spatial resolution and magnetic sensitivity, Electron holography has opened a new way to directly observe the flux lines in superconductors. It has successfully shown the detailed magnetic field distribution of individual flux lines penetrating Pb thin films. This technique also excels at observing flux line dynamics. By taking the holograms with a TV camera and recording them on a video tape, it became possible to observe the flux motion microscopically and continuously. Using this technique, the present study will demonstrate the thermally excited and the electrical current induced flux line dynamics.
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.
Interface microstructures in melt-textured YBa2Cu3O7-δ on Ag-Pd and flux pinning centers introduced by Y2BaCuO5 particles
Authors: Wang Z. L. , Goyal A. , Kroeger D. M.
Published: June 2020

Transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) were used to study the microstructure of the melt-textured YBa2Cu3O7-δ (123) thick films on Ag-Pd substrate. The samples used for this study were melt-textured thick films of 123 on a Ag10%Pd alloy substrate. The film was prepared using a paint-on technique and was processed according to a schedule described elsewhere, Domains of 123, as large as 5-6 mm, are formed in the film. Analytical electron microscopy (AEM) studies of this material were made using a Philips EM400 TEM/STEM (100 kV) with a field emission gun (FEG). A small electron probe of diameter approximately 2 nm was generated, and used in determining the compositional change across grain boundaries.
Atomic resolution AEM (ARAEM) of oxide superconductors
Authors: Dravid Vinayak P. , Zhang H. , Marks L.D. , Zhang J.P.
Published: June 2020

A 200 kV cold field emission gun atomic resolution analytical electron microscope (ARAEM, Hitachi HF-2000) has been recently installed at Northwestern. The ARAEM offers an unprecedented combination of atomic structure imaging of better than 0.20 nm nominal point-to-point resolution and about 0.10 nm line resolution, alongwith nanoscale analytical capabilities and electron holography in one single instrument. The ARAEM has been fully functional/operational and this paper presents some illustrative examples of application of ARAEM techniques to oxide superconductors. Additional results will be presented at the meeting.
Low-temperature annealing of YBa2Cu3O7-x
Authors: Sabatini R.L. , Zhu Yimei , Suenaga Masaki , Moodenbaugh A.R.
Published: June 2020

Low temperature annealing (<400°C) of YBa2Cu3O7x in a ozone containing oxygen atmosphere is sometimes carried out to oxygenate oxygen deficient thin films. Also, this technique can be used to fully oxygenate thinned TEM specimens when oxygen depletion in thin regions is suspected. However, the effects on the microstructure nor the extent of oxygenation of specimens has not been documented for specimens exposed to an ozone atmosphere. A particular concern is the fact that the ozone gas is so reactive and the oxygen diffusion rate at these temperatures is so slow that it may damage the specimen by an over-reaction. Thus we report here the results of an investigation on the microstructural effects of exposing a thinned YBa2Cu3O7-x specimen in an ozone atmosphere using transmission electron microscopy and energy loss spectroscopy techniques.
High-resolution TEM of C60 thin films
Authors: Krakow W. , Rivera N.M. , Roy R.A. , Cuomo J.J.
Published: June 2020

The ability to fabricate buckminsterfullerenes, C60 molecules, in reasonably large quantities has made possible studies of the structural properties of this form of carbon when it is in a crystalline state. At room temperature, x-ray diffraction from three-dimensional bulk C60 crystals shows that the molecules are centered on sites of a face-centered-cubic Bravais lattice, A∘ = 14.2Å. Somewhat earlier in time, a study of C60/C70 bulk material using electron diffraction and high resolution electron microscopy has revealed a hexagonal phase. It is now believed that this phase is a simple cubic structure rather than a hexagonal structure. Since it is reasonable to expect that highly ordered C60 thin films will have superior properties to bulk material, several studies have been undertaken to understand the early stages of C60 thin film growth. Monolayer growth on GaAs has been studied by scanning tunneling microscopy., and on mica at room temperature using helium scattering. Along similar lines we have grown thin films of C60 molecules on mica and NaCl and characterized the crystallinity and local structural arrangements. Here we present some of our results of the electron microscope examination of these materials.
High-resolution TEM of Al-Cu-Fe quasicrystals
Authors: Krakow William , Divincenzo David P. , Bancel Peter A. , Cockayne Eric , Elser Veit
Published: June 2020

High resolution electron microscopy and electron diffraction have always been key tools for the study of quasicrystals. The unique features of quasicrystals arc their long range oricntational order despite the absence of periodic translational order, and their non-crystallographic symmetry. The early work in electron microscopy and diffraction assessed the degree of perfection of these materials; microdo-mains with slightly different orientations, phason strains and dislocations were found which masked the fundamental atomic structure. A defect free material was sought to deduce the atomic arrangement of these materials and this was found in Al-Cu-Fe. Preliminary examinations of these materials using 20 at.% Cu and 15 at.% Fe indicated they are almost entirely free of phason strains when viewed in a 200kV microscope.At the time of these investigations the microscopes employed were limited in resolution and thus provide limited information about the atomic arrangements of these quasicrystals. Recently, studies were made using a more powerful microscope operating at 400kV where the point resolution is improved to 1.7Å. In that case, a Al-Mn-Si specimen was viewed along the five-fold axis under apparent optimum imaging conditions. These prior studies have interpreted various image features as being due to dynamical scattering processes and therefore little about the atomic arrangement of the quasicrystal is obtained. Our interpretation of the image feature is different and is due to modification of the phase contrast transfer function. Here clarification is given of the information contained in high resolution micrographs of quasicrystals.
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.
HREM applications to industrial products: Observation of thick-film resistors with very large electron transparent area
Authors: Li Z.G. , Carcia P.F. , Donohue P.
Published: June 2020

HRTEM is a very powerful tool for structural characterization of materials. However, its role in industry is still very limited and electron microscopy is generally considered as a secondary support technique, although it can uniquely provide microstructural information leading to understanding and improvement of product quality, especially for those materials in the form of films. An example in the semiconductor industry is recendy described by Anderson. He points out that the main concerns of imaging using a conventional cross-section sample preparation method are too small imaged areas, not representative of the product, and artifacts that may be introduced during the ion-milling process. Here we apply HREM to thick film resistors and attempt to overcome these obstacles.
Interaction of dislocations with grain boundaries in Ni3Ge
Authors: Fang J. , Schulson E. M.
Published: June 2020

An important aspect of deformation in LI2 intermetallic compounds at low temperature is the interaction of gliding dislocations with grain boundaries. In-situ straining in Ni3Al revealed one mode of interaction: dislocations piling up at grain boundaries and emitting into the adjoining grain . The present paper shows another mode of dislocation-grain boundary interaction in Ni3Ge: dislocations piling up against grain boundaries and being ejected back into the original grain. In the present case, this phenomenon is broadly termed “dislocation reflection”. However, in both of these modes, the outcoming dislocations are not necessarily the same as the incoming ones.
Characterizations of LaNi5-yAly alloys
Authors: Mosley W.C.
Published: June 2020

LaNi5-YAlY alloys which reversibly form hydrides are used to store, pump, and separate hydrogen isotopes during processing of tritium at the Department of Energy's Savannah River Site (SRS). Over forty alloys with nominal bulk aluminum contents (Y) from 0 to 1.16. including several made with intentional excesses and deficiencies of lanthanum, were characterized by scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis and x-ray diffractometry (XRD) to determine distributions and compositions of constituent phases. Objectives were to produce primary LaNi5-yAly phases with desired absorption and desorption pressures for hydrogen isotopes and minimize secondary phases with undesirable absorption/desorption behaviors. Electron probe microanalysis (EPMA) was used to determine aluminum contents (y) of primary LaNi5-yAly phases. A relationship between y and hexagonal unit cell parameters was established. Pressure-composition- temperature (PCT) measurements allowed development of equations for predicting hydrogen desorption plateau pressures from XRD or EPMA data.
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.
Interfaces and precipitation
Authors: Weatherly G.C.
Published: June 2020

An important class of alloy transformation involves the precipitation of a body-centred cubic phase in a close packed cubic or hexagonal matrix (or vice-versa). In the past ten years, numerous investigations have demonstrated that the precipitate grows as a lath or needle-shaped particle, with the growth direction of the axis of the particle parallel to an invariant line of the phase transformation. Although there are an infinite number of potential invariant lines in such a transformation, commonly one observes that the growth direction is close to the common close-packed directions e.g. <110>f and <111>b, with a rational or near-rational orientation relationship between the two phases. These observations can be rationalized by invoking the geometric principles embodied in Bollmann's O-lattice theory or by appealing to the minimization of strain energy principle associated with the set(s) of misfit dislocations lying parallel to the invariant line. Figure 1 shows an example of this characteristic morphology of a lath of γ (face—centred) precipitated in a matrix of α (body-centred) in a two-phase stainless steel. The lath is bounded by well-developed facet planes_(see Fig. 1) with a growth direction about 5° from the common close packed [111]α, [101]γ directions. Sets of misfit dislocations and steps are visible at the (416)α and (275)α facet planes.
Compositional imaging of Co/Cr multilayer by high-angle annular dark-field microscopy
Authors: Liu J. , Cheng Y. , Stearns M. B.
Published: June 2020

Magnetic multilayers (ML) have been recently the subject of active research because of their fundamental magnetic behavior (i.e., large magnetoresistance at room temperature and two-dimensional superconductivity etc.) and also because of their potential application as media for perpendicular magnetic recording and information storage. It has been found that the magnetic properties of these ML films strongly depends on their layered structure. Thus it is essential to correlate the growth conditions with the structural, compositional and magnetic properties of the ML films. High resolution electron microscopy (HREM) has proved very useful for providing information about the detailed microstructures of the ML on an atomic scale. But the interpretation of HREM images in terms of chemical modulation across ML films is difficult due to the presence of strong diffraction and phase contrast in HREM images. In this study we have used high-angle annular dark-field (HAADF) microscopy technique to extract compositional information of the e-beam evaporated Co/Cr ML films and to correlate these results with that obtained by HREM.
Deformation effects on transgranular carbide precipitation in 304 stainless steels
Authors: Advani A.H. , Murr L.E. , Matlock D.J. , Fisher W.W. , Tarin P.M. , Miller R.L. , Ramos C. , Romero R. J. , Maldonado J.G. , Cedillo C.M.
Published: June 2020

Plastic deformation is a key variable producing accelerated intergranular (IG) carbide precipitation and chromium-depletion (sensitization) development in stainless steels. Deformation above 20% also produces transgranular (TG) carbides and depletion in the material. Research on TG carbides in SS is, however, limited and has indicated that the precipitation is site-specific preferring twin-fault intersections in 316 SS versus deformation-induced martensite and martensite lath-boundaries in 304 SS. Evidences indicating the relation between martensite and carbides were, however, sketchy.The objective of this work was to fundamentally understand the relationship between TG carbides and strain-induced martensite in 304 SS. Since strain-induced martensite forms at twin-fault intersections in 304 SS and the crystallography of the transformation is well understood, we believed that it could be key in understanding mechanisms of carbides and sensitization in SS. A 0.051% C, 304 SS deformed to ∽33% engineering strain (40% true strain) and heat treated at 670°C/ 0.1-10h was used for the research. The study was carried out on a Hitachi H-8000 STEM at 200 kV.
Use of light microscopy in the qualitative and quantitative study of liquid crystalline order
Authors: Viney Christopher
Published: June 2020

Light microscopy is a convenient technique for characterizing molecular order in fluid liquid crystalline materials. Microstructures can usually be observed under the actual conditions that promote the formation of liquid crystalline phases, whether or not a solvent is required, and at temperatures that can range from the boiling point of nitrogen to 600°C. It is relatively easy to produce specimens that are sufficiently thin and flat, simply by confining a droplet between glass cover slides. Specimens do not need to be conducting, and they do not have to be maintained in a vacuum. Drybox or other controlled environmental conditions can be maintained in a sealed chamber equipped with transparent windows; some heating/ freezing stages can be used for this purpose. It is relatively easy to construct a modified stage so that the generation and relaxation of global molecular order can be observed while specimens are being sheared, simulating flow conditions that exist during processing. Also, light only rarely affects the chemical composition or molecular weight distribution of the sample. Because little or no processing is required after collecting the sample, one can be confident that biologically derived materials will reveal many of their in vivo structural characteristics, even though microscopy is performed in vitro.
Dimensionality of hexatic melting in liquid crystals by in situ electron diffraction
Authors: Hui S.W. , Cheng M. , Ho J.T. , Pindak R.
Published: June 2020

The theory of melting in two dimensions indicates that it is very different from the melting in three dimensions. An intermediate hexatic phase, with long range orientational but short range translational order, is proposed to exist between two dimensional solid and fluid phases. Because the long range order is limited experimentally by the domain or “grain” size, which is expected to be of sub-millimeter size, selected area electron diffraction is the method of choice for observing orientational order. Free-standing smectic liquid crystal films prove to be a most attractive system in which to verify this theory. However, multilayered liquid crystal samples are not strictly two dimensional systems because of interlayer interaction, their melting characteristics are expected to deviate from that of two dimensional systems. Furthermore, the outer layers may behave differently from the inner ones due to interfacial tension. We have applied low dose electron diffraction to study the effect of dimensionality, or number of layers, on the melting of multilayer organic liquid crystals.
Investigation of defect structures of thermotropic liquid crystal polymers by optical and scanning EM
Authors: Ding Ding-kuo , Thomas Edwin L.
Published: June 2020

The integer defect structures of semi-flexible thermotropic polyester (MHDT) based on 1,10-decane bisterephthaloyl chloride with methyl hydroquinone were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). Liquid crystals, in general, are characterized by a unit vector called the director, n, which indicates the locally preferred orientation of molecules. Different types of defects, which were described by their strength, s, defined by the total change of the orientation of the director around the singularity divided by 2л, are imaged in the director fields. The integer defects of s=±1, in liquid crystal polymers were revealed by OM and SEM using the lamellar decoration technique developed in this laboratory.
A study on the formation of hydrothermally prepared BaTiO3 particles
Authors: Dogan Fatih , Liu Jun , Sarikaya Mehmet , Aksay Ilhan A.
Published: June 2020

BaTiO3 is an important ferroelectric material because of its high dielectric constant. To increase the optical transparency and mechanical strength, it is desirable to produce fine grained BaTiO3. Fine particles can be produced by colloidal processing techniques. In this case, however, it is usually necessary to synthesize monodispersed BaTiO3 particles with a predetermined diameter in a suspension. One widely used method to produce colloidal BaTiO3 particles is by reacting TiO2 particles with Ba(OH)2 in an aqueous solution at a moderately low temperature, i.e.,T < 100 °C.
Sulphur-induced reconstruction on Cu3Au (110) surface
Authors: Huang Yi , Cowley John M.
Published: June 2020

Sulphur is a common impurity in metals and alloys. The segregation of sulphur to the surface and interface has major effects on the chemical and mechanical properties of the materials. The structure of the sulphur adsorbed surface and its behavior at raised temperature have great practical and theoretical significance. Cu3Au is a typical ordering alloy whose bulk structure and properties have been extensively studied. Recently its clean surfaces have also been studied by many authors. These make Cu3Au a good material for studying the behavior of sulphur on surface, but, as we know, the impurity-adsorbed surfaces of this alloy have not been investigated very much. No work on the sulphur-adsorbed surfaces has been done.
Imaging dislocation shear band in sapphire
Authors: Chen S. J.
Published: June 2020

The deformation of sapphire at low temperatures and high strain rates produces basal twins and dislocation activity in various slip planes which appear as distinctive shear bands, where the dislocations line up in a row (figure 1). The most common shear band is in the basal plane (the lower band in figures 1a through 1c) and is made up of partial dislocations of the type 1/3<1010>(0001). These dislocations are all associated with the same stacking fault and the sum of three of these faults returns the structure to perfect stacking. The faults can be distinguished in bright field in the (1014) reflections (figure 1b) and clearly, in the lower band, the stacking fault disappears when three dislocations have traversed.
Dislocation loops in α-silicon nitride single crystals
Authors: Suematsu H. , Petrovic J. J. , Mitchell T. E.
Published: June 2020

Silicon nitride(Si3N4) is well known to be a most promising ceramic material for high temperature structural applications. It has high strength even at 1200°C and its fracture toughness is about 5 to 7 MPa•m½. Si3N4 has been manufactured on mass production lines as the compressor rotor for turbo chargers. For high temperature use, it is important to know the deformation characteristics of the material and the role played by dislocations and other defects. However, research on the nature of defects in Si3N4 has been limited considering the importance of Si3N4. In this study, we have examined defects in single crystals of Si3N4.
In-situ observations of the behaviors of ferroelectric domains in BaTiO3 under applied electric fields with TEM
Authors: Tsai Feng , Khiznichenko Victoria , Cowley J. M.
Published: June 2020

The previous studies on the behaviors of ferroelectric domains under applied electric fields were made by a number of researchers, e.g. Merz and Little on bulk BaTiO3 crystals with optical microscopy. It was suggested that under the applied electric field the new antiparallel domains nucleated and grew and 90° and 180° domains nucleated and grew sidewise. However, those results and conclusions were obtained from the experiments on large bulk crystals with optical microscopy of relatively lower magnification and resolution. TEM is a very powerful tool in the study of crystal structure and defects and may provide a new interpretation to the study of microdomains of hundred angstroms in thin ferroelectric films with a higher magnification and resolution and may be combined with electron diffraction. However, no reference has been found that an in-situ TEM study of the behaviors of ferroelectric materials under applied electric fields has ever been made.
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.
Quantitative estimation of electron beam irradiation damage of polyethylene single crystal using imaging plate
Authors: Oikawa T. , Shindo D. , Kudoh J. , Aita S. , Kersker M.
Published: June 2020

The degree of electron beam irradiation damage is estimated from the intensity fading of diffraction spots and the lattice spacing increase of the specimen. Previously, qualitative estimatin of the damage was made for beam-sensitive specimens, e.g., polymers and biomolecules. In the present study, the degree of irradiation damage was estimated by quantitative measurement of the intensity of electron diffraction patterns, using the Imaging Plate (IP). Polyethylene single crystal, which is a typical material for polymers, was used as a specimen.
Low-energy electron beam lithography: Monte Carlo simulation and experiment
Authors: Stark TJ. , Radzimski Z. J. , Peterson P.A. , Griffis D.P. , Russell P. E.
Published: June 2020

Recent advances in electron optical systems which allow reduction of electron beam voltage while maintaining sufficiently small spot size and high current density have opened new possibilities for electron beam lithography. The main advantage of low beam energy lithography is a reduction of backscattered electrons and, consequently, the reduction of problems associated with proximity effects. The other advantages of this technique are reduction in the dose required to modify a resist and minimization of substrate damage caused by energetic electrons. Proper electron energy must be chosen at which the beam deposits its energy mainly within the resist film with minimal penetration into the substrate. Monte Carlo simulation programs have been used widely to predict the scattering interactions and thus the area of proximity effects. Rutherford cross section for angle scattering and Bethe energy loss have been commonly used in Monte Carlo modeling. However, low energy lithography (<5keV) requires a more accurate approach based on Mott cross sections for scattering and a more precise formula for energy loss replacing the Bethe law which is invalid below 1 keV energy.
Ion thinning of TEM cross sections under beam switching control
Authors: Alani R. , Harper R.G. , Swann P.R.
Published: June 2020

Ion milled, cross sectional TEM specimens are used extensively to study the microstructure of multilayered materials. Unfortunately, it is difficult to get all the layers in a cross section equally electron transparent because usually they mill at different rates and have different atomic numbers. Differential thinning can be minimized by milling at low angles so that the slow milling layers protect the fast milling layers from the ion beam. However, even at low angles uneven milling can still occur when the ion beam travels along the multilayer interface (glue line). This problem can be partially overcome by using a shield to cut off the ion beam in these directions. However, this solution is not completely satisfactory because material sputtered from the edge of the shield can contaminate the specimen. A better solution, is to rock the specimen over a range of angles while the ion beam is centered approximately about the perpendicular to the glue line. With this method there is a possibility of uneven milling at both ends of the rocking angle where the beam is stationary for a short period during the change in direction of specimen rotation. Another solution, which is reported here, is to rotate the specimen continuously in the normal way and to switch off the ion beam as it passes by along the specimen glue line.
Observations on the precipitates in steels by extraction replica technique using the potentiostatic etching method with a non-aqueous electrolyte
Authors: Park Shin-hwa , Kim Ki-hwan , An Byung-ryang
Published: June 2020

Quantitative analysis of the precipitates of the steel is necessary in order to improve mechanical properties of the steel, because the precipitates in steels play an important role on the grain growth, recrystallization, and precipitation hardening. Recently, in-situ scanning electron microscope(SEM) observations on the precipitates with potentiostatic etching method in non-aqueous electrolyte have been reported. We applied the potentiostatic etching method for the preparation of the extraction replica.
4-dimensional, high-resolution imaging of living cells
Authors: Inoué Shinya
Published: June 2020

This paper reports progress of our effort to rapidly capture, and display in time-lapsed mode, the 3-dimensional dynamic architecture of active living cells and developing embryos at the highest resolution of the light microscope. Our approach entails: (A) real-time video tape recording of through-focal, ultrathin optical sections of live cells at the highest resolution of the light microscope; (B) repeat of A at time-lapsed intervals; (C) once each time-lapsed interval, an image at home focus is recorded onto Optical Disk Memory Recorder (OMDR); (D) periods of interest are selected using the OMDR and video tape records; (E) selected stacks of optical sections are converted into plane projections representing different view angles (±4 degrees for stereo view, additional angles when revolving stereos are desired); (F) analysis using A - D.
Structure in three dimensions of H,K-ATPase by Electron Microscopy and image processing
Authors: Mohraz Manijeh , Sathe Sonal , Smith P.R.
Published: June 2020

H,K-ATPase is an integral protein of the plasma membrane of parietal cells in the gastric mucosa. It is believed to constitute the pump responsible for secretion of acid into the stomach. It utilizes energy from ATP hydrolysis to transport H+ out of the cell and K+ into the cell against an H+ concentration gradient of one million-fold. The catalytic subunit (Mr 110,000) of H,K-ATPase shows striking sequence homology to those of other ion-transporting ATPases. The enzyme has a second subunit, a glycoprotein of ca 300 amino acids, which is homologous to the β subunit of the Na, K-ATPase.
Structure of rRNA in the ribosome
Authors: Boublik M. , Wall J. S.
Published: June 2020

Ribosomes are complex subcellular organelles playing a central role in protein biosynthesis. They are composed of more than fifty different proteins and three or four ribonucleic acids (rRNA) unevenly distributed (with no symmetry) between the large and small ribosomal subunit. It has been well established that ribosomal proteins and rRNAs are both involved in formation of the internal architecture of the ribosome as well as its function in protein synthesis. Understanding the fundamental relationship between structure and function requires establishment of the 3-D structure of the ribosome and its components at a molecular level.
The photoreceptor cytoskeleton visualized
Authors: Burnside Beth
Published: June 2020

The vertebrate photoreceptor provides a drammatic example of cell polarization. Specialized to carry out phototransduction at its distal end and to synapse with retinal interneurons at its proximal end, this long slender cell has a uniquely polarized morphology which is reflected in a similarly polarized cytoskeleton. Membranes bearing photopigment are localized in the outer segment, a modified sensory cilium. Sodium pumps which maintain the dark current critical to photosensory transduction are anchored along the inner segment plasma membrane between the outer segment and the nucleus.Proximal to the nucleus is a slender axon terminating in specialized invaginating synapses with other neurons of the retina. Though photoreceptor diameter is only 3-8u, its length from the tip of the outer segment to the synapse may be as great as 200μ. This peculiar linear cell morphology poses special logistical problems and has evoked interesting solutions for numerous cell functions. For example, the outer segment membranes turn over by means of a unique mechanism in which new disks are continuously added at the proximal base of the outer segment, while effete disks are discarded at the tip and phagocytosed by the retinal pigment epithelium. Outer segment proteins are synthesized in the Golgi near the nucleus and must be transported north through the inner segment to their sites of assembly into the outer segment, while synaptic proteins must be transported south through the axon to the synapse.The role of the cytoskeleton in photoreceptor motile processes is being intensely investigated in several laboratories.
The photoreceptor cytoskeleton and disk turnover
Authors: Roof Dorothy J. , Hayes Annmarie , Adamian Michael
Published: June 2020

The light sensitive part of the rod photoreceptor, the outer segment, is continually renewed within the retinas of adult vertebrates. This process of membrane renewal consists of two distinct components, disk addition and disk shedding, which are maintained in a constant dynamic balance throughout adult life. Thus, although each rod outer segment loses approximately 10% of its length each day due to shedding and phagocytosis of rod tips by the adjacent pigment epithelial layer, the total length of the outer segment remains constant due to assembly of new disks at the base of the outer segment. The mechanisms of disk shedding and disk addition are, as yet, undefined although it appears that each phase of the overall disk renewal cycle may involve some cytoskeletal components.
Pre-mRNA splicing and nuclear organization
Authors: Spector David L. , Lark Gayle , Huang Sui
Published: June 2020

Several major classes of small nuclear ribonucleoprotein particles (snRNPs) (Ul, U2, U4/U6, U5) as well as other splicing factors have been shown to be involved in the processing of pre-mRNA molecules. For most RNA polymerase II transcripts, such processing includes the addition of a 7-methylguanosine cap structure at the 5’ end of the nascent RNA transcripts, hnRNP assembly, splicing, polyadenylation, and the exchange of hnRNP proteins for mRNP proteins. Splicing of nuclear pre-mRNA molecules occurs in spliceosomes, macromolecular complexes composed of a pre-mRNA, snRNPs and other splicing factors. Since RNA processing is essential to cellular function, we and others have been interested in identifying the organization of splicing factors in cell nuclei. We have examined the localization of snRNPs in a variety of mammalian cells and have observed differences in the organization of these factors in transformed cells, immortal cells, and cells of defined passage number. Cells of defined passage number exhibit a speckled staining pattern after immunolabeling with anti-Sm, anti-B’ or anti-m3G antibodies. Furthermore, 2 to 3% of the cells, in a given population, exhibit 1 to 2 round “foci” in addition to the speckled labeling pattern. However, transformed cells exhibited 1 to 4 intensely stained round foci, in 81 to 99% of the cells, in addition to the speckled labeling pattern. Immortal cells exhibited 1 to 4 intensely stained smaller foci in 4 to 40% of the cells, in addition to the speckled labeling pattern. When immortal cells (REF-52) which had been transformed by adenovirus (REF-52 Ad5.4) were examined, these cells exhibited an increase in the percentage of cells containing 1 to 2 intensely stained foci, in addition to the speckled labeling, from 24% to 99%. We have identified these intensely stained foci as coiled bodies which can be visualized in the nucleoplasm of cells with or without antibody labeling. This study is the first to directly correlate an increase in the number of cells containing coiled bodies in a given cell population with the transformed phenotype. Based on this study, we conclude that the organization of snRNPs within the mammalian cell nucleus is a reflection of the physiology of the cell which may change upon transformation or immortalization.
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.
Three-dimensional reconstruction of the bacterial basal body/switch complex by electron cryomicroscopy
Authors: Francis Noreen R. , Sosinsky Gina E. , Thomas Dennis , DeRosier David J.
Published: June 2020

The bacterial flagellum is unique among Nature's motors in that it posesses a reversible, rotary motor and a propeller that converts torque into thrust The basal body, that part of the flagellum isolated from cells in attempts to purify the motor, contains eight different structural proteins. In Salmonella typhimurimi, the basal body consists of four rings (denoted M, S, L, and P) threaded on a coaxial rod. The M-S, L and Prings are each composed of a different protein, FliF, FlgH, and Flgl, each of which is present in ∽26 copies. The rod contains four different proteins, FlgB, FlgC, FlgF, and FlgG. Also present is FliE. These all are present in ∽6 copies except for FlgG present in ∽26 copies. The proteins important for motor rotation, however, are missing in standard basal body preparations. These missing proteins include the three “switch” proteins, FliG, FliM, and FliN, which control motor reversal (clockwise and counter-clockwise rotation) and may correspond to the rotor and gearbox of the motor. FliG has recently been shown to be localized at the M ring.
Electron diffraction of helical structures
Authors: Ruiz T. , Diaz R. , Ranck J-L. , Caspar D.L.D. , DeRosier D.J.
Published: June 2020

Electron microscopy has advantages over X-ray diffraction for the study of helical structures. For X-ray studies, one needs large well oriented samples which are difficult to obtain. Only one helical structure, TMV, has been solved by conventional X-ray analysis using multiple isomorphous replacement. In contrast, one requires single particles or small rafts for studies by electron microscopy. We are attempting to use a combination of imaging and electron diffraction data to analyze helical structures at 9-10 Å resolution in order to visualize α-helices. To obtain electron diffraction patterns we produced well-ordered domains (∽ 1-3 μm in diameter) for diffraction work. Several methods succeeded in aligning helical particles : the lipid monolayer technique, mica sandwiching and unidirectional blotting. The lipid monolayer technique proved to be the best for high resolution work. The three samples under study (flagellar filaments from Salmonella typhimurium, TMV and TMV stacked disk protein aggregate) gave electron diffraction patterns out to ∽10 Å resolution.