bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure Variations in Small Metal Particles
Authors: Barry J.C. , Gai P.L. 
Published: June 2020

High resolution electron microscopy (HREM) is found to be a useful technique for the study of supported metal particles. However, with HREM, image detail in supported particles is often obscured by support contrast. Computer calculations have therefore been carried out for a model silver particle/amorphous alumina catalyst, to examine the effect of support thickness on particle image detail.Model catalysts were prepared by evaporating Ag on amorphous alumina. The diffraction contrast and HREM images, recorded on a JEOL 200CX HREM, are shown in Figs. 1(a) and (b) respectively. It can be seen in the latter image that the edge definition is blurred in the presence of the amorphous support.Image calculations were carried out using an Intellect 200 image analysis system for 55 atom particles of cuboctahedral and icosahedral shapes (energy calculations show that small clusters of 55 atoms are relatively stable 3) as well as for 309 atom cuboctahedral particles.
Simultaneous Ultramicrotomy of Multiple Areas and Examination of Ribbons on One New Grid
Authors: Chien K. , Van de Velde R. , Heusser R. 
Published: June 2020

The localization of an area of interest for ultramicrotomy within a tissue block is usually determined by first surveying large thick sections under the light microscope. Yang has shown that multiple areas from a large block face can be vertically divided for sequential sectioning. By applying a simple and direct technique, two or more areas of interest from the same block can be sectioned simultaneously and examined on one grid for ultrastructural studies.Depending on the size and distance between the areas that are going to be sectioned, there are several possible approaches:1.Two Small Areas Widely Separated. Since the entire surface of the block is in one plane after thick sectioning, it is possible to rotate the block and trim selected areas into two trapezoids so that their leading and trailing edges are parallel to the knife edge. If their combined total areas do no exceed the average area routinely sectioned, the two trapezoids can be cut simultaneously and two ribbons formed (fig.1).
E.M. Autoradiography of Crayfish Androgenic Gland
Authors: Tichenor Paula J. 
Published: June 2020

The androgenic gland is near the terminal region of the vas deferens in most crustaceans. It secretes a hormone responsible for male sexual characteristics. Eyestalk ablation, or destalking, is known to cause androgenic gland stimulation. Previous experimental and E.M. evidence is equivocal as to whether the hormone is a steroid or a protein; hence, this investigation.Three groups of 6 experimental (bilateral eyestalk extirpation) and 6 non-destalked controls were selected from 36 reproductive Form I male Orconectes sp. crayfish. The three groups were given the following regimes 6 days after destalking the experimental animals: (1) 2UCi/g animal weight L-amino acid-3H; (2) 0.76UCi/g Uridine-5-3H; and (3) same regime as group (2) followed by specimen incubatitfn with 0.2 mg/ml ribonuclease Type I-A.
Imaging Properties of the Soft X-Ray Photon
Authors: Sayre D. 
Published: June 2020

Introduction. The soft x-ray photon (0.1-lkeV, wavelength l-10nm) is now available for the first time in large numbers, thanks to several new radiation sources (see below). This particle offers important new opportunities in the imaging of unprocessed biological structures, including intact biological cells in the natural and even living state.Basic properties. We begin by examining the basic properties of the particle which give it its special imaging characteristics.1.The reaction cross-section level of its principal imaging reaction, photoelectric absorption (Fig. 1). This cross-section, at 105- 106 barns/atom, is excellently matched to the thickness of the biological cell. The other principal imaging reactions in use today (scattering of 100keV electrons in electron microscopy, and coherent scattering of 0.15nm photons in x-ray crystallography; see Fig. 1) are best suited to cellular sections or substructures, and to macroscopic ordered specimens (crystals), respectively.2.The strong dependence of its reaction cross-section on Z (Fig. 1). For example, the 2.4nm photon images biological structures in the presence of water, due to its low reactivity with hydrogen and oxygen. In general, good image contrast is obtained without specimen processing, even for biological materials.
X-Ray Contact Imaging: the Technique
Authors: Feder R. , Mayne-Banton V. 
Published: June 2020

Until recently, instruments used to image small biological objects directly have involved the use of light microscopy or electron microscopy. Presently, the use of x-rays has emerged as another probe to investigate details in biological specimens. X-rays can be used either by using an x-ray “lens”, which will be discussed by others at this symposium or by a direct contact “print” of the object on a special emulsion. This latter method is what will be discussed in this paper.The object to be ‘photographed’ is prepared on a substrate and then placed in contact with a resist such as poly- methyl-methacrylate (PMMA). This polymer has the property that when it is exposed to x-rays and then placed in a solution of methyl isobutyl ketone (MIBK) it will 'develop’ depending on the number of x-ray photons absorbed in the PMMA. This three dimensional relief structure is actually a photon density map of the specimen.
Freeze-Drying-Embedding Method of Specimens For Analysis of Diffusible Elements by Electron Spectroscopic Imaging
Authors: Simon G.T. , Spitzer E. 
Published: June 2020

Electron spectroscopic imaging (ESI), developed in the last decade by F. P. Ottensmeyer and his group is one of the most sensitive electron microscopic analytical techniques available today. Spatial resolutions of 0.5.m and mass resolution of 50 atoms or less can be achieved. The limitations of ESI resides in the fact that only very thin specimens (20nm in thickness) can be used. It is therefore impossible to analyze frozen-dried or frozen hydrated sections.The primary concern in analyzing diffusible elements is their extraction and translocation during processing. Already existing freeze-drying embedding techniques have been modified. Quick freezing is by far the fixation method of choice. The type of coolant and the entrance velocity are of critical importance. Vitrification layers of 25-30 microns can be obtained by plunging small fragments of tissue into liquid propane at an entrance velocity of more than 6.4 m/s.
Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy
Authors: Chien K. , Van de Velde R. , Shintaku I.P. , Sassoon A.F. 
Published: June 2020

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.
Films That Wet Without Glow Discharge
Authors: Wall J.S. , Hainfeld J.F. , Chung K.D. 
Published: June 2020

Mass measurements with the Scanning Transmission Electron Microscope (STEM) provide a direct link between biochemistry and the information in the dark field STEM image of an unstained biological specimen. Total mass of a complex mass of individual components, mass per unit length, mass per unit area, or change in mass distribution following biochemical treatment, are easily determined.Accuracy and preparation requirements have been described elsewhere. In the past year, we have made significant progress in specimen preparation, developing a “wet film” technique which eliminates the need for glow discharge treatment of grids. The method is similar to the Valentine technique but uses minute quantities of specimen. A thin carbon film is evaporated under UHV conditions onto freshly cleaved rock salt. The thin carbon is floated off the rock salt onto distilled water and a titanium grid with a thick, holey carbon film laid on top of it. After a few minutes, the grid is picked up from above by grasping its edge with a tweezer and turned over so that the adhering drop of water is facing upward.
Structural and Chemical Studies of Pathological Fibers in Human Neurofibrillary Degeneration
Authors: Kosik K.S. , Duffy L.K. , Bakalis S. , Abraham C. , Selkoe D.J. 
Published: June 2020

The major structural lesions of the human brain during aging and in Alzheimer disease (AD) are the neurofibrillary tangles (NFT) and the senile (neuritic) plaque. Although these fibrous alterations have been recognized by light microscopists for almost a century, detailed biochemical and morphological analysis of the lesions has been undertaken only recently. Because the intraneuronal deposits in the NFT and the plaque neurites and the extraneuronal amyloid cores of the plaques have a filamentous ultrastructure, the neuronal cytoskeleton has played a prominent role in most pathogenetic hypotheses.The approach of our laboratory toward elucidating the origin of plaques and tangles in AD has been two-fold: the use of analytical protein chemistry to purify and then characterize the pathological fibers comprising the tangles and plaques, and the use of certain monoclonal antibodies to neuronal cytoskeletal proteins that, despite high specificity, cross-react with NFT and thus implicate epitopes of these proteins as constituents of the tangles.
Early Electron Microscopy remembered through the candle light of history
Authors: Newberry Sterling 
Published: June 2020

As nearly as we have been able to ascertain, three very early programs to make a true Electron microscope arose in this hemisphere independently and concurrently. That is to produce instruments with demountable vacuum systems and means for interchanging specimens. Washington University in St. Louis was one of the three. The author is grateful for this opportunity to describe the Washington University work.Washington University was a likely place for a beginning in electron microscopy. In the first quarter of the century it had risen to prominence in many fields especially physics, biology and medicine and close communication existed between them. The physics department had direct lineage from J. J. Thompson and W. H. Bragg and close ties with Chicago and Berkeley. The biology department had strong connections with Woods Hole, while the medical school staff included “people from the four comers of the earth” and it had a close association with the Rockefeller Medical Institute.
The effect of thermal exposure on precipitation of Ti3Al(C,N) in Ti-48Al-IV-0.2C
Authors: Donlon W.T. , Dowling W.E. , Cambell C.E. , Allison J.E. 
Published: June 2020

Titanium aluminides are attractive candidates for high temperature structural applications because of their high strength to weight ratio at elevated temperatures. The microstructure of these alloys consists of γ-TiAl (distorted L10 structure) , plus α2-Ti3Al (ordered DO19 structure). Varying the heat treatment temperature and cooling rate of these alloys alters the volume fraction and distribution of the γ and α2 phases. This has significant effects on the room temperature ductility. In addition, precipitation of carbides has been observed during high temperature exposure. The effect of these precipitates on the mechanical properties has yet to be determined.Figure 1 shows the general microstructure that was used for this investigation. TEM foils were prepared by electropolishing using 5% perchloric, 35% 1-butanol, 60% methanol at -40°C. No precipitates were found following heat treatment in the γ+α phase field. Samples approximately 20 mm square were thermally exposed to temperatures between 625° and 1000°C for times between 1 and 2000 hours.
New phases in the Al-Co-Cu alloy system : Marked variations from the “true” decagonal phase
Authors: Ramani Atul S. , Giannuzzi Lucille A. , Carim Altaf H. , Bitler William R. , Howell Paul R. 
Published: June 2020

The decagonal phase in the Al-Co-Cu alloy system was first discovered by He et al. We shall call this phase the “true” decagonal phase (TD) phase because it is the one most commonly observed in the Al-Co-Cu alloy system. It is well known that quasicrystalline phases such as the TD phase contain the phason defect peculiar to incommensurate phases that causes subtle variations from perfect decagonal symmetry. In this paper we report on the existence of new phases in the Al-Co-Cu alloy system, that are related to the TD phase but yet show marked variations from the TD phase. These variations are too drastic to be caused by phason defects alone.Figure 1(a) is a selected area diffraction pattern (SADP) recorded from a TD phase single “crystal” showing near perfect decagonal (tenfold) symmetry. This SADP agrees very well with the first published SADP of the TD phase in Al-Co-Cu that also shows almost perfect decagonal symmetry. In a previous paper we have reported several kinds of deviations from perfect decagonal symmetry, but none of these deviations involved the observation of perfect pentagonal (fivefold) symmetry. Figure 1(b) is an SADP recorded from a phase in Al-Co-Cu that exhibits perfect pentagonal symmetry instead of the expected decagonal symmetry. This breakdown of true tenfold symmetry into true fivefold symmetry is caused by unequal intensities of equal and opposite reflections. This example is a clear violation of Friedel's law, which states that the intensities of equal and opposite diffraction vectors must be equal.
HREM observations of internetallic alloy formation in Pt-Sn thin films
Authors: Dufner D.C. 
Published: June 2020

The general goal of this research is to clarify mechanisms of solid state reactions at the atomic level as a step in the rationalization of macroscopic reaction behavior in solids. A study of intermetallic alloy formation resulting from interdiffusion of metals in thin films can be made by HREM. In this work, reactions between Pt and Sn in thin films are studied to elucidate mechanisms for structural and compositional changes during the interdiffusion process.Thin films of Pt and Sn used in this study were prepared by the two-film method introduced by Shiojiri. Few hundred angstroms of Pt were vacuum-deposited onto holey carbon films mounted on TEM grids. Sn films with an average thickness of 200Å were created by evaporation at rates of 15-30 Å/sec onto air-cleaved KBr substrates. The Sn films were wet-stripped and collected on the holey Pt grids. Figure 1 shows a cross-section schematic of a Pt-Sn couple. While this two-film arrangement did not allow observations of the actual reaction interface, microtomy was used to produce cross-sections.
EM study of phase transformation in zinc coatings
Authors: Drewien C. A. 
Published: June 2020

Electrodeposited iron-zinc alloy (EZA) coatings, used for barrier and galvanic corrosion protection of steel by the automotive industry, are deposited under conditions, which give rise to small grain sizes and non-equilibrium phases. Subsequent processing of automotive body panels requires a paint bake cycle of 175 °C for 30 minutes. The as-deposited microstructure has not been investigated by TEM due to difficulty of sample preparation, and information on the effect of heat treatment upon EZA coatings is lacking. In this study, the as-deposited microstructure of a 6 w/o Fe EZA coating is investigated with electron microscopy, and in-situ heating in the TEM is used to observe the thermal stability of the microstructure.A 6 w/o bulk iron content EZA coating was electrodeposited from a chloride bath onto a steel surface. The 7 μm thick coating was removed from the substrate, and three mm disks, punched from the material, were electropolished at 30-40 V in a room temperature, aqueous chromic-acetic acid mix. Samples were imaged with a JEOL 6300 FEG-SEM operated with an accelerating voltage of 1 keV and with a Philips 430 EM under an operating voltage of 250 keV.
Microstructure of BSCCO-Ag composites made by floating-zone method
Authors: Ikuhara Y. , Suzuki T. , Ikuhara Y.H. , Michishita K. , Takahashi K. , Kubo Y. 
Published: June 2020

To develop applications of oxide superconductors,in addition to the enhancement of the critical current density (Jc), improving their mechanical properties is also important. The Bi-oxide superconductors are intrinsically brittle because of clevage in the basal plane. We have found that doping by Ag is very effective in improving the mechanical properties of Bi-oxide superconductor without decreasing its Jc. In this study,the microstructure of BSCCO-Ag was observed by transmission electron microscopy (TEM) in order to clarify the relationship of microstructure to mechanical properties.BSCCO-Ag composites were fabricated by floating zone (FZ) method. The critical temperature(Tc) and Jc were 89K and 3000A/cm2, respectively. The mechanical properties were measured by three-point bend test and indentation fracture measurements. A JEOL 4000FX (400kV) was used to analyze the microstructure.
Simulation and interpretation of image contrast and diffuse scattering of tweed structure
Authors: Zhu Yimei , Cai Z.X. , Suenaga M. , Welch D.O. 
Published: June 2020

The so-called tweed structure exhibits a roughly periodic lenticular-domain image (Fig.l) associated with the streaking of diffuse scattering around the fundamental reflections in an electron diffraction pattern (Fig.2(c)). Tweed was observed in high Tc oxides YBa2(Cu1-xMx)3O7-δ (M = Fe, Co, Al, x≥0.03; M = Cu, δ∼0.6-0.8), as well as in some binary alloys, which usually show statistical fluctuation in their composition or in an order parameter.Although tweed has long been studied, crystallographic aspects of tweed modulation is not well understood. To shed light on the details of the structure, we performed simulations both on the tweed image and diffuse scattering, based on our TEM observations of YBa2(Cu1-xMx)3O7-δ
Controlled hot-stage experiments in the HREM with active drift compensation and 2Å lattice resolution
Authors: Boyes E D , Hanna L , Gai P L 
Published: June 2020

An electronic system has been developed to compensate electronically, with <2Å lattice resolution, for the image shift due to specimen and/or stage drift in the HREM. A simple system has been highly effective in compensating for the drift which has long limited many scientifically important but technically demanding applications of TEM in both the physical and biological sciences. It has facilitated controlled hot stage experiments with full HREM resolution.Over an extended period of time (>15s) which is fully adequate to record a high resolution image photographically or electronically, most drift of either the stage or the specimen can be approximated to a constant and relatively slow rate along a straight line path segment. With the new system the drift characteristic is video analyzed and an inverse correction ramp derived from a 12-bit DAC or external analog function generator is applied to existing post-specimen electrical image shift coils to stabilize the image position at the TEM camera. Image stabilization is also necessary for high quality data recording by digital processing of multiple (e.g. 256 or more) TV frames for an equivalent exposure time of several (8.5) seconds. This is the main data recording method for the dynamic experiments and with it low dose techniques can be used to minimize the beam damage effects which otherwise can be a serious problem in many HREM applications.
High-resolution imaging of ceramics
Authors: Carter C. Barry , McKernan Stuart 
Published: June 2020

Ceramic materials have now been studied for many years using high-resolution transmission electron microscopy (HRTEM). The technique has had a major impact on our understanding of both the solid-sate chemistry of the materials themselves and the interfaces and defects present in the materials. The development of both aspects of the field have progressed in parallel as summarized in Figure 1. It is the purpose of this paper to review the current status and assess the needs for future studies.HRTEM is uniquely suited for examining the chemistry and structure of ceramic materials on the local scale. Although it does not directly give information on the chemical composition of these materials, it does provide information on the local crystal structure which can, in turn, be used to infer the local crystal chemistry. A particularly clear illustration of such an application is shown in Figure 2 where a small particle with the spinel structure has grown inside a matrix of olivine as a result of internal oxidation of the matrix. The selected-area diffraction pattern confirmed the FCC nature of the particle although due to its small size, the diffraction spots were all considerably elongated.
A HREM study of V/Al2O3 interface
Authors: Ikuhara Y. , Pirouz P. , Heuer A. H. , Yadavalli S. , Flynn C. P. 
Published: June 2020

The interface structure between vanadium and the R-plane of sapphire (α-Al2O3) was studied by conventional and cross-sectional high resolution electron microscopy (HREM) to clarify the atomic structure of the interface.A 57 nm thick vanadium film was deposited on the (1102) (R) plane of sapphire by molecular beam epitaxy (MBE) at a substrate temperature of 920 K in a vacuum of 10-10torr. The HREM observations of the interface were done from three directions: two cross-sectional views (parallel to [0221]Al2O3 and [1120]Al2O3) and a plan view (parallel to [2201]Al2O3) by a top-entry JEOL 4000EX electron microscope (400 kV).
Phase identification in SiC whisker reinforced Al2O3-R2O3-based composites
Authors: Sung C.M. , Ostreicher K.J. , Huckabee M.L. , Buljan S.T. 
Published: June 2020

A series of binary oxides and SiC whisker reinforced composites both having a matrix composed of an α-(Al, R)2O3 solid solution (R: rare earth) have been studied by analytical electron microscopy (AEM). The mechanical properties of the composites as well as crystal structure, composition, and defects of both second phases and the matrix were investigated. The formation of various second phases, e.g. garnet, β-Alumina, or perovskite structures in the binary Al2O3-R2O3 and the ternary Al2O3-R2O3-SiC(w) systems are discussed.Sections of the materials having thicknesses of 100 μm - 300 μm were first diamond core drilled. The discs were then polished and dimpled. The final step was ion milling with Ar+ until breakthrough occurred. Samples prepared in this manner were then analyzed using the Philips EM400T AEM. The low-Z energy dispersive X-ray spectroscopy (EDXS) data were obtained and correlated with convergent beam electron diffraction (CBED) patterns to identify phase compositions and structures. The following EDXS parameters were maintained in the analyzed areas: accelerating voltage of 120 keV, sample tilt of 12° and 20% dead time.