bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microanalysis of silicate glass films grown on α-Al2O3 by pulsed-laser deposition
Authors: Mallamaci Michael P. , Bentley James , Barry Carter C. 
Published: June 2020

Glass-oxide interfaces play important roles in developing the properties of liquid-phase sintered ceramics and glass-ceramic materials. Deposition of glasses in thin-film form on oxide substrates is a potential way to determine the properties of such interfaces directly. Pulsed-laser deposition (PLD) has been successful in growing stoichiometric thin films of multicomponent oxides. Since traditional glasses are multicomponent oxides, there is the potential for PLD to provide a unique method for growing amorphous coatings on ceramics with precise control of the glass composition. Deposition of an anorthite-based (CaAl2Si2O8) glass on single-crystal α-Al2O3 was chosen as a model system to explore the feasibility of PLD for growing glass layers, since anorthite-based glass films are commonly found in the grain boundaries and triple junctions of liquid-phase sintered α-Al2O3 ceramics.Single-crystal (0001) α-Al2O3 substrates in pre-thinned form were used for film depositions. Prethinned substrates were prepared by polishing the side intended for deposition, then dimpling and polishing the opposite side, and finally ion-milling to perforation.
Ultrastructural localization of fibronectin in process of serial intimal regeneration
Authors: Ishiwata Toshiyuki , Yokoyama Munehiro , Asano Goro 
Published: June 2020

Intimal injury is considered as one of the initiation factors of atherosclerosis and intimal thickening. However the morphological elucidation after intimal injury is not so clear. On the other hand, fibronectin is a glycoprotein that play an important role in cell adhesion, migration, spreading, and differentiation. This study was designed to examine the mechanism of serial intimal regeneration after intimal injury and the localization of fibronectin using scanning and transmission electron microscope.Male Wistar rats, weighing 400g were used and endothelial denudation was produced by the modified methods of Baumgartner. A deflated vascular balloon catheter( 1.5F, DOW CORNING , Corp.) was introduced into the thoracic aorta, then inflated up to 2.5mm in diameter, and passed through the aorta three times to a length of 2.5cm. The animals were sacrificed at 15min, 3,7,14 and 28 days after denudation. For electron microscopic examination, the tissues were fixed in 2.5% glutaraldehyde in 0.1M phosphate buffer, treated with 1% osmium tetroxide in phosphate buffer, and dehydrated in a graded ethanol series.
Tailoring microstructures of materials through biomimetics
Authors: Sarikaya Mehmet , Aksay Ilhan A. 
Published: June 2020

Biomimetics involves investigation of structure, function, and methods of synthesis of biological composite materials. The goal is to apply this information to the design and synthesis of materials for engineering applications.Properties of engineering materials are structure sensitive through the whole spectrum of dimensions from nanometer to macro scale. The goal in designing and processing of technological materials, therefore, is to control microstructural evolution at each of these dimensions so as to achieve predictable physical and chemical properties. Control at each successive level of dimension, however, is a major challenge as is the retention of integrity between successive levels. Engineering materials are rarely fabricated to achieve more than a few of the desired properties and the synthesis techniques usually involve high temperature or low pressure conditions that are energy inefficient and environmentally damaging.In contrast to human-made materials, organisms synthesize composites whose intricate structures are more controlled at each scale and hierarchical order.
Microstructural characterization using x-ray diffraction imaging
Authors: Black David R. 
Published: June 2020

X-ray diffraction imaging, also known as x-ray topography, is a powerful tool to study the defect microstructure of single crystals. As the name implies, this technique is based on recording an image of the diffracted x-ray beam from a crystal. Contrast in the image results from point-to-point variation in the diffracted intensity through the crystal. An example of a diffraction image is shown in figure 1. That this image is in some way a topographic representation of the sample can be seen in the impression of differing elevations and textures in different parts of the image. However, since this image is a result of diffraction from the sample the interpretation of the image is much more complex.Diffraction contrast is usually separated into two types: mosaic contrast and extinction contrast. Mosaic contrast occurs for crystals considered to be formed from a collection of small perfect crystal blocks. These blocks have a well defined rocking curve width, the angular range over which they will diffract, and may be slightly misoriented with respect to each other and/or may have different lattice spacing.
Scanned probe microscopy in biology
Authors: Fisher Knute A. 
Published: June 2020

Numerous scanned probe microscopes (SPM) have been developed over the past decade. Most are based on the precise positioning of sample and probe using piezoelectric transducers, and some have the capability of imaging flat surfaces with atomic resolution. The first atomic resolution SPM applied to biological samples was the scanning tunneling microscope (STM). The atomic force microscope (AFM) was subsequently developed and over the past few years has become the instrument of choice for biological applications.Early investigators applied the STM to examinations of organic and biological systems ranging from small molecules to nucleic acids, globular and fibrillar proteins, and larger structures such as viruses, membranes, and even whole cells. Much of this work was done during the mid-80s using electricallyconductive highly-oriented pyrolytic graphite (HOPG) as a substrate. Images were often difficult to obtain and control experiments were lacking. Unfortunately, when careful experiments were undertaken, they revealed that HOPG itself was capable of generating images previously thought to be biological.
Distortion in lattice-resolution scanned-probe microscope images
Authors: Fei L. 
Published: June 2020

Scanned probe microscopes (SPM) have been widely used for studying the structure of a variety material surfaces and thin films. Interpretation of SPM images, however, remains a debatable subject at best. Unlike electron microscopes (EMs) where diffraction patterns and images regularly provide data on lattice spacings and angles within 1-2% and ∽1° accuracy, our experience indicates that lattice distances and angles in raw SPM images can be off by as much as 10% and ∽6°, respectively. Because SPM images can be affected by processes like the coupling between fast and slow scan direction, hysteresis of piezoelectric scanner, thermal drift, anisotropic tip and sample interaction, etc., the causes for such a large discrepancy maybe complex even though manufacturers suggest that the correction can be done through only instrument calibration.We show here that scanning repulsive force microscope (SFM or AFM) images of freshly cleaved mica, a substrate material used for thin film studies as well as for SFM instrument calibration, are distorted compared with the lattice structure expected for mica.
High-resolution SEM and STEM of adrenocortical endothelium: Molecular resolution of membrane complexes
Authors: Apkarian Robert P. 
Published: June 2020

A multitude of complex ultrastructural features are involved in endothelial cell (EC) gating and sorting of lipid through capillaries and into steroidogenic cells of the adrenal cortex. Correlative microscopy is necessary to distinguish the structural identity of features involved in specific cellular pathways. In addition to diaphragmed fenestrae that frequently appear in clusters, other 60-80 nm openings; plasmalemma vesicles (PV), channels and pockets fitted with diaphragms of the same dimension, coexist on the thin EC surface. Non-diaphragmed coated pits (CP) (100-120 nm) involved in receptor mediated endocytosis were also present on the EC membrane. The present study employed HRSEM of cryofractured and chromium coated specimens and low voltage HRSTEM of 80 nm thick LX-112 embedded sections stained with 2.0% uranyl acetate. Both preparations were imaged at 25 kV with a Topcon DS-130 FESEM equipped with in-lens stage and STEM detector.HRSEM images of the capillary lumen coated with a lnm continuous fine grain Cr film, provided the ability to scan many openings and resolve (SE-I contrast) the fine structure of diaphragm spokes and central densities (Fig. 1).
A linear-field scanning-force microscope: Application to x-ray gabor holography
Authors: Lindaas Steve , Jacobsen Chris , Howells Malcolm 
Published: June 2020

We have built a linear field Scanning Force Microscope to readout x-ray Gabor holograms recorded in photoresist. A field linearity yielding one half or less pixel registration error (for 10-50nm pixel sizes) across the scanned hologram is needed so that the resulting reconstruction is not significantly degraded. The desire for a large (75μm)2and linear scanning field necessitated designing our own stage since these conditions could not be met commercially.Gabor holography is well positioned to exploit flash x-ray sources, such as x-ray lasers and free electron lasers, as well as ultra-bright third generation synchrotron sources as a sub-50nm resolution imaging technique for biological samples. Gabor holography requires no optics (except for a monochromator with λ/Δλ ∽ 500) and no sample prefocusing since the image is focused in the reconstruction process. Furthermore, sample alignment is eased since the area of illumination can be quite large. In fact, Gabor holography can be used to image large fields with multimode sources with the resulting numerical aperture, and hence resolution, being limited by the size of a single mode.
Coherent soft x-ray single unit-cell diffraction
Authors: Chapman Henry N. , Balhorn Rod 
Published: June 2020

Following the basic ideas of x-ray structure analysis of single unit-cell specimens by Sayre it should be possible to determine the structure of weakly-scattering non-crystalline material from the radiation scattered from it, at a maximum resolution equal to half the wavelength of the radiation. Therefore, in principle, it should be possible to determine structures to 1 nm resolution by soft x-ray diffraction at 2 nm wavelength. An imaging method based solely on diffraction should be an extremely powerful x-ray microscopy tool.In order to determine the structure of the diffracting object however, the incident beam must be completely temporally and spatially coherent and the complex wave-field must be sampled across some surface at spatial frequency intervals of 1/(2 * Δ), where Δ is the resolution. Thus, a three-dimensional data set (a two-dimensional complex field) must be recorded to obtain the three-dimensional structure of the scatterer. In most cases, an area detector is used to determine the intensity of the wave-field, losing the phase information.
Chemical contrast in scanning transmission x-ray microscope
Authors: Zhang X. , Ade H. , Jacobsen C. , Kirz J. , Lindaas S. , Oehler V. , Williams S. , Wirick S. 
Published: June 2020

The Scanning Transmission X-ray Microscope (STXM) on the X1A undulator beamline, at the National Synchrotron Light Source, BNL, has been used for imaging various wet, unstained biological samples at 55 nm Rayleigh resolution. The microscope's Modulation Transfer Function was measured and agrees well with theoretical calculations, confirming the performance of the microscope as designed. The microscope is operated mainly in direct imaging mode where x-rays of fixed energy are diffractively focused to a microprobe and the sample is scanned in two dimensions. By varying the x-ray energy while keeping the beam focused to one spot on the sample enables us to get localized chemical composition of the sample from the absorption spectra in an area smaller than 0.2 by 0.2 micron at present. The spatial distribution of the chemical compositions can be obtained with a spacial resolution of 55 nm by imaging at absorption maxima of specific chemical bonds.The chemical sensitivity of the X-ray Absorption Near Edge Structure (XANES) provides a new contrast mechanism for organic system imaging.
Structure and properties of organic liquid crystals
Authors: Voigt-Martin I.G. 
Published: June 2020

Organic liquid crystals (LCs), both in the monomeric and polymeric state, are capable of self organisation because of the anisotropic shape of their molecules. By suitable molecular engineering it is thus possible to induce interesting physical properties like ferroelectricity, second harmonic generation (SHG) and photoconductivity. For a deeper understanding it is necessary to gain insight into the relationship between molecular characteristics (electronic charge distribution, dipole moments, hyperpolarisabilities, molecular conformation), structural relations (symmetry relations, space groups, defects) and the above physical propertiesFor structure analysis electron diffraction patterns from different crystallographic zones with many higher orders of diffraction are required. Unfortunately a characteristic feature of LCs is their loss of all higher order reflections and a change in symmetry. Furthermore, LCs give rise to specific defects, which give important information about the elastic energy density of the system. These can only be characterised by a phase contrast imaging method in which the small angle spatial frequencies are transferred by the electron microscope phase transfer function.
Application of energy-filtered imaging to the characterization of heterogeneous catalysts
Authors: Crozier P.A. , McCartney M. R. 
Published: June 2020

Heterogeneous metal catalysts often consist of one or more metal species distributed over a highly porous oxide support. In many cases, there is not a clear understanding of the relationship between the microstructure of such systems and their catalytic properties. Indeed, the systems often possess complex morphologies with domains containing many different phases. To build up a clear picture of the microstructure of these materials it is essential to have an accurate representation of the distribution of elements over reasonably large areas of the sample. Here we employed a Zeiss EM 912 fitted with an omega filter to determine elemental distributions over large areas in amination catalysts.The microscope, which operates at 120 kV, is interfaced to a Gatan slow-scan CCD camera (10242pixels) which can be used to acquire images, diffraction patterns and energy-loss spectra from regions of the sample. At present our machine is fitted with a W filament as an electron source which gives high beam current but limits the usable energy resolution to about 2 eV.
Growth behavior and structures of carbon nanotubes
Authors: Liu Mingqi , Cowley John M. 
Published: June 2020

Recent discovery of the novel hollow graphitic tubules of nanometer dimensions, so called carbon nanotubes, has greatly stimulated the studies in the field of carbon fiber growth. Their potential applications in electronic and materials industries have been suggested. In the present study, carbon nanotubes were fabricated by an arc-discharge method. The microstructures of nanotubes thus obtained were examined with a JEM-2000FX high-resolution transmission electron microscopy (HRTEM) and with an electron nanodiffraction technique in a VG HB-5 scanning transmission electron microscopy (STEM).HRTEM images show that nanotubes, consisting of 3 to 30 carbon sheets, have a length up to 1 μm and a diameter of 6 to 26 nm. Some nanotubes have a symmetric uniform sheet spacing of 0.34 nm. Others show non-symmetric uneven fringes (Fig. 1), indicating that they may have a polyhedral cross section. Most nanotubes are closed by cone-like or polyhedral shaped caps (Figs. 2 and 3). The closure angle varies from 17 to 40° and the internal sheets have a tendency to be closed in pairs. Fig. 4 shows the image of a growing tubes.
The bright future of digital imaging in scanning electron microscopy
Authors: Postek M. T. , Vladar A. E. 
Published: June 2020

One of the major advancements applied to scanning electron microscopy (SEM) during the past 10 years has been the development and application of digital imaging technology. Advancements in technology, notably the availability of less expensive, high-density memory chips and the development of high speed analog-to-digital converters, mass storage and high performance central processing units have fostered this revolution. Today, most modern SEM instruments have digital electronics as a standard feature. These instruments, generally have 8 bit or 256 gray levels with, at least, 512 × 512 pixel density operating at TV rate. In addition, current slow-scan commercial frame-grabber cards, directly applicable to the SEM, can have upwards of 12-14 bit lateral resolution permitting image acquisition at 4096 × 4096 resolution or greater. The two major categories of SEM systems to which digital technology have been applied are:In the analog SEM system the scan generator is normally operated in an analog manner and the image is displayed in an analog or "slow scan" mode.
Imaging peristome movement in the environmental SEM
Authors: Long J.C. , Mueller D.M.J. 
Published: June 2020

The ElectroScan Environmental Scanning Electron Microscope is a powerful new tool in the study of spore dispersal mechanisms in bryophytes. The ESEM is similar in many ways to a conventional SEM, but with a few important differences. While the ESEM column remains at high vacuum (10−7torr), the specimen chamber typically operates in a water vapor environment at low vacuum (1 to 20 torr). The secondary electron signal is generated by gaseous signal amplification and is collected by the Environmental Secondary Detector.This new technology has significant implications regarding sample preparation and specimen requirements. First, there is no need to dry the sample, thus observations in the natural state are possible. Second, the water vapor dissipates charge build up, therefore a conductive coating is not necessary.The ESEM lends itself directly to the understanding of spore dispersal in mosses, which involves the sensitivity of the peristome to changes in ambient moisture (hygroscopicity).
Z-contrast imaging of an ordered interface structure in the Si/CoSi2/Si system
Authors: Chisholm M. F. , Jesson D. E. , Pennycook S. J. , Mantl S. 
Published: June 2020

We show the atomic structure of buried CoSi2/Si(001) boundaries involves a 2×1 ordering of the interfacial Co atoms. The ability to directly image and interpret this unforeseen structure is possible through the Z-contrast technique, and presents a new level of insight into the important and controversial relationship between the atomic structure and electronic properties, such as the energy barrier for electron transport across metal-semiconductor interfaces.The buried CoSi2 layer was produced by implanting Co+ ions (200 keV, 2 × 1017 ions/cm2) in a Si(001) substrate heated to 350°C. The substrate was capped with 200 nm of SiO2 and then given a two-step anneal in high purity argon (750°C for 30 s + 1150°C for 10 s). This treatment results in a continuous buried CoSi2 layer ~70 nm thick, ~90 nm below the substrate surface. The layer and the substrate are oriented such that the cubic CaF2 unit cell of CoSi2 is aligned parallel to the cubic unit cell of Si.
Ultramicrotomy for study of interfaces and coatings
Authors: Williams G. , Malis T. 
Published: June 2020

While grain and phase boundaries in conventional alloys are examined quite readily by classic TEM specimen preparation methods such as electropolishing and ion thinning, the plethora of metal, ceramic and/or polymer combinations in many advanced materials have proven to be a much stiffer challenge. Whether in the form of composites, coatings, multilayers or thin films, such material systems have given rise to newer methods such as low angle ion thinning, mechanical (tripod) polishing to electron transparency and diamond knife sectioning. The damage incurred during the latter method may be offset by the advantages of a controlled thickness which is fairly insensitive to the type of material.Fig. 1 demonstrates that the high degree of deformation generated in ductile materials by no means prohibits conventional grain boundary imaging due to the substantial degree of dislocation self-recovery which generally occurs in thin sections. Alloy phase boundaries also are amenable to examination after sectioning, although the particle/matrix interface may debond somewhat as the hardness difference increases.
Recent developments in low-voltage SEM of polymers
Authors: Krause S.J. , Adams W.W. 
Published: June 2020

Over the past decade low voltage scanning electron microscopy (LVSEM) of polymers has evolved from an interesting curiosity to a powerful analytical technique. This development has been driven by improved instrumentation and in particular, reliable field emission gun (FEG) SEMs. The usefulness of LVSEM has also grown because of an improved theoretical and experimental understanding of sample-beam interactions and by advances in sample preparation and operating techniques. This paper will review progress in polymer LVSEM and present recent results and developments in the field.In the early 1980s a new generation of SEMs produced beam currents that were sufficient to allow imaging at low voltages from 5keV to 0.5 keV. Thus, for the first time, it became possible to routinely image uncoated polymers at voltages below their negative charging threshold, the "second crossover", E2 (Fig. 1). LVSEM also improved contrast and reduced beam damage in sputter metal coated polymers. Unfortunately, resolution was limited to a few tenths of a micron due to the low brightness and chromatic aberration of thermal electron emission sources.
Dynamic low-dose electron diffraction and imaging of phase transitions in polymers
Authors: Martin David C. , Liao Jun 
Published: June 2020

By careful control of the electron beam it is possible to simultaneously induce and observe the phase transformation from monomer to polymer in certain solid-state polymcrizable diacetylenes. The continuous change in the crystal structure from DCHD diacetylene monomer (a=1.76 nm, b=1.36 nm, c=0.455 nm, γ=94 degrees, P2l/c) to polymer (a=1.74 nm, b=1.29 nm, c=0.49 nm, γ=108 degrees, P2l/c) occurs at a characteristic dose (10−4C/cm2) which is five orders of magnitude smaller than the critical end point dose (20 C/cm2). Previously we discussed the progress of this phase transition primarily as observed down the [001] zone (the chain axis direction). Here we report on the associated changes of the dark field (DF) images and selected area electron diffraction (SAED) patterns of the crystals as observed from the side (i.e., in the [hk0] zones).High resolution electron micrographs (HREM), DF images, and SAED patterns were obtained on a JEOL 4000 EX HREM operating at 400 kV.