bluuebunny/crossref_metadata_2025 huggingface dataset:
3D Visualization of Maize Stem by MRI Technology
Authors: Cheng P C , Chen J H , Hwang S C , Sun C K , Walden D B , Cheng W Y
Published: July 2020

Recent development in confocal and multi-photon microscopy allows 3D imaging of plant tissue in high resolution. However, other than physical sectioning, macroscopical study of plant organs in 3D remains a difficult task. Among various available technologies for macroscopical imaging (e.g., Xray macro-tomography, optical coherent tomography and MRI), MRI is an ideal choice for its contrasting modality in volumetric imaging of soft tissues. A 3T Biospect MRI system (Brucker, Germany)(FIG 1) equipped with a 6cm inner diameter micro-quadrature coil (FIG 2) for RF transmission and reception of MRI signals was used in this study. Spin echo based RARE sequence was used to obtain T2 weighted images with TR/TE = 3160.5/58.5ms and field-of-view of 1.67cm × 1.67cm (256 × 256 pixels) at a slice thickness of 0.8mm. This corresponds to a voxel size of 65 × 65 × 800μm. Data was obtained within 1/2 hour with number-of-excitations (nex) set at 16. Figure 4 (a-x) shows a series of MRI sections through a stem node (the node below the main ear insertion) from field-grown maize (Zea mays, van Odyssey sweet corn). The stem was fixed in 1:3 EtOH/acetic acid, washed thoroughly in water prior to imaging. Air bubbles trapped in the tissue were removed by vacuuming, to avoid imaging artifact due to low magnetic susceptibility of air. Figure 5 (a-g) shows reconstructed longitudinal sections. Three-dimensional reconstruction (FIG. 3) was performed by using Vaytek VoxBlast™ and AutoQuant’s AutoVisulize 3D™ software. in combination with image segmentation and tracing tools, the MRI technology will greatly enhance our capability in the understanding of vascular architecture and its development in plants.
Electron Tomography of Corneal Collagen Fibrils
Authors: Gilpin C J , Holmes DF , Ziese U , Koster AJ , Kadler KE
Published: July 2020

The ability of cornea to transmit light whilst being mechanically resilient is directly attributable to the formation of an extracellular matrix containing orthogonally arranged sheets of densely packed uniformly-narrow collagen fibrils, in which each sheet contains parallel arrays of fibrils. An understanding of the molecular basis of tissue organisation requires knowledge of the detailed 3-dimensional structure of individual collagen fibrils and how they interact to generate higher order structures. in this study adult bovine corneal collagen fibrils were examined using transmission electron microscopy and automated electron tomography to generate three-dimensional volumes of individual fibrils which had been negatively stained. Tilt series images were collected with an angular increment of 2° over a range of ± 70° using a Philips CM200FEG coupled to a TVIPS automated electron tomography system. A microfibrillar substructure was observed throughout the thickness of the fibril (Figure 1). The microfibrils were ∼4 nm in diameter and were oriented in a right-handed helical twist along the length of fibrils. The microfibrils were observed at an angle of 15° to the long axis of the fibril. As the technique of electron tomography generates a threedimensional volume from the data it was possible, for the first time, to visualise the lateral arrangement of molecules within individual fibrils. There were regions where there was a distinct lateral order and other regions which showed a more fluid-like arrangement. The axial positions of most crystallinity corresponded with the location of the C-telopeptides and N-telopeptides as well as a region close to the d-band in the gap structure of the fibrils. The study also demonstrated that the microfibrils are organised in a quasi-hexagonal packing arrangement
Multiscale Microscopies in the Design and Fabrication of Novel Nanocomposites
Authors: Eppell SJ , Tong W
Published: July 2020

The smallest apatite mineralites found in nature reside in vertebrate bone tissue. These nanoapatites participate in the formation of a protein/mineral composite with unique physical and biological properties. The composite has distinct structural features at the 10 nm, 100 nm, 1 um, 100 um, and 1 cm length scales. We analyzed the natural material on the 1-1000 nm length scale with the purpose of setting the design criteria for synthetically duplicating the material. Using a biomimetic motif, we synthesized nanomineralites with size and shape approximately equal to the natural material.

We show that our synthetic mineralites compare with the natural apatites. Recently the average size of naturally occurring mineralites in mature bovine bone was shown to be 12 nm X 10 nm X 0.61 nm. Similar experiments on 1-3 week old bovine bone mineralites showed an average size of9nm X 6nm X 2.0 nm. Within a standard deviation, the length and width of the two populations are equal.
Identifying Molecular Counterparts of Functional Gradients in Biomaterials
Authors: Herbert Waite J
Published: July 2020

many naturally occurring structures are, in fact, composite materials with functionally graded mechanical properties. in manufacturing, achieving such graded properties is critical when joining two materials of significantly different elastic moduli, thermal or electronic characteristics. One assumes that similar imperatives are at play in the profusion of biological examples of gradients. Two gradient biosystems, in particular, have been the focus of our attention: These are mussel byssal threads and polychaete jaws. Mussel byssal threads are composites consisting of anisotropically packed discontinuous fibers in an amorphous matrix all coated by a protective cuticle. The threads are produced by process resembling reaction injection molding and imparted with a longitudinal gradient of mechanical properties ranging from stiff and tough distally to extensible and rubbery proximally. Collagen is the principal tensile polymer as determined by fiber x-ray diffraction, however, the mechanical properties of typical tendon are poorly matched with those of byssal threads.
Relation Between Shear Viscosity and Morphology in Lung Surfactant Monolayer
Authors: Ding Junqi , Warriner Heidi E , Zasadzinski Joseph A
Published: July 2020

The primary function of lung surfactant monolayers (LS) is to control and reduce surface tension in the lung permitting easy breathing. to do this, the monolayer must maintain coverage of the entire lung surface during the rapid surface area changes which accompany breathing. We use a magnetic needle viscometer and optical microscopy to determine the relationship between monolayer shear viscosity, which controls its two-dimensional flow properties, and synthetic lung surfactant composition. We show that, within a specific range, palmitic acid interacts with DPPC/POPG to make lung surfactant rigid at low surface tension (or high surface pressure) and fluid at high surface tension. This enables the monolayer to attain near zero surface tensions during compression yet respread easily at high surface tension More palmitic acid makes the monolayer more rigid and eventually increases the collapse surface tension while reducing the readsorption rate at high surface tension.
Effects of Spaceflight on Cultured Bone Cells
Authors: Landis WJ
Published: July 2020

Bone is known to alter its architecture, mass, composition, metabolic state, development and function in response to the effects of external forces applied to it, whether those forces be loading or unloading in nature (1). These adaptive changes by bone and the vertebrate skeletal system in general may be imparted by mechanical forces, gravity, buoyancy, or other such influences and manifest themselves in a number of ways. The skeleton of an animal, for example, may increase in mass through exercise and heightened activity, it may lose mass as a result of extended immobilization or weightlessness, or it may remodel during fracture repair processes. A mechanism explaining the adaptation by bone and the skeleton to the presence or absence of applied forces is not completely understood, but the changes are thought to occur ultimately at the cellular level of structure. Studies presented here have examined the relationship between forces and bone cell response in this context: Spaceflight and weightlessness have been utilized to investigate the influence of gravitational unloading on a model of cultured osteoblasts derived from normal embryonic chicken calvaria.
Vascular Tissue Engineering Utilizing Electrospun Matrices: Microscopic Evaluations
Authors: A. Matthews Jamil , E. Wnek Gary , G. Simpson David , L. Bowlin Gary
Published: July 2020

The development of a seamless, collagen-based vascular prosthetic scaffolding (< 4 mm I.D.) has been accomplished using an electrospinning fiber production technique (Patents Pending). Electrospinning is the deliberate application of the phenomenon of electrostatic spraying which occurs when electrical forces at the surface of the polymer solution overcome the surface tension, creating a splay. The splay produces fibers with diameters in the nano-scale range (<500 nm). The collagen-based scaffold production method (flexible, quick, and simple) utilizes the splaying of the collagen-based solution from a nozzle to a grounded rotating mandrel (4 mm O.D. cylindrical mandrel for the preliminary vascular tissue engineering). in splaying, the solvent evaporates creating nano-scale fibers of polymerized collagen (and elastin in some variations). The collagen fibers are collected on the mandrel forming a cylindrical tube (media equivalent scaffolding). to date, mixtures of collagen containing Type I and 80:20 Type l/Elastin have been utilized to produce vascular scaffolds of various thickness (50 - 2,000 microns).
Role of Raman Microprobe Spectroscopy in the Characterization of Microelectronic Materials
Authors: Klymko NR , Casey JA , Tai L , Fitzsimmons JA , Adar F
Published: July 2020

The production of semiconductor chips and packaging materials involves the use of a wide array of materials, from solvents and polymers, to photoresists, to metal and dielectric layers, to conductive and thermal pastes. Characterization of these materials, both in raw form and as formulated for in-process use, is integral to successful use of them in microelectronic manufacturing. Physical and chemical analytical techniques are employed to determine parameters such as composition, cure state, and interface chemistry. More often than not, it is the successful combination of complementary analyses which provide the complete understanding of material parameters needed.

This paper reports the use of Raman microprobe spectroscopy as a characterization technique for microelectronic materials. Several examples will be given, illustrating the type of information which can be obtained and the complementary use of Raman spectroscopy in conjunction with other analytical techniques such as Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) to characterize microelectronic packaging materials and organic materials used in semiconductor manufacture.
Application of Confocal Laser Imaging Microscopy and Raman Spectroscopy to Particle Characterization in Semiconductor Industry
Authors: Conti Giuseppina , Uritsky Yuri
Published: July 2020

The analytical needs in semiconductor technology have developed according to the increasing demands imposed by size and complexity. Early optical visualization, localization and counting of ever-smaller particles extended almost immediately to their morphological and chemical characterization. This evolution was due to the shifting balance from quality control to root-cause analysis. Root-cause analysis requires a deeper analytical approach to the characterization of the observed defects. Atomic composition may suffice at times as an answer. However, this information may be ambiguous and inadequate. Therefore, deeper chemical information regarding molecular structure and crystallinity of the particle is now required.

The analytical capabilities and versatilities associated with optical spectroscopy inevitably have led to their increasing applications in the semiconductor industry. in particular, the complementary Infrared and Raman spectroscopies on one hand provide huge insight into the molecular structure and crystallinity of the particles, on the other hand Raman and Photoluminescence (PL) spectroscopies are easily coupled to systems providing particle visualization and localization.
The Partition Layer of Common Bunt Teliospores
Authors: Hess WM , Weber DJ
Published: July 2020

The basidiomycete fungus, Tilletia constitutes the most important group of smuts economically as they infect cereal grains which provide a major portion of the world’s food supply. The teliospores of the smuts which have been studied have a spore wall layer called the partition layer or the striated zone which is very resistant to fixatives and resins used for electron microscopy. We assume that the chemical nature of this wall layer is the primary factor to prevent spore desiccation and to maintain spore viability for many years. Teliospores of Tilletia tritici (Bjerk.) Wint. (formerly T. caries), T. controversa Kühn, T. indica Mitra, and Neovossia horrida (Tak.) Padwick and Khan all have a reticulated exterior spore layer (sheath). Common bunt, Tilletia laevis Kühn (formerly T. foetida) teliospores lack this exterior reticulated layer, but are also resistant to spore desiccation and maintain viability for many years. Therefore, the purpose of this study was to compare the ultrastructural characteristics of the partition layer of T. laevis teliospores with the partition layer of other teliospores of smut fungi which have been studied.
Nipah Virus and Other Emerging Pathogens: The Role and Importance of Electron Microsccopy
Authors: Hyatt AD
Published: July 2020

When it is all said, done, celebrated and published, the question remains, “How do we identify new viruses?” How do we build preparedness for rapid identification and teams whereby important data can be disseminated to our peers in virology, histopathology and molecular biology? The answers lie in the ability to build effective teams and to recognize the unique contributions of disciplines such as electron microscopy and the associated skill bases. The success in Australia for the rapid and accurate identification of new viruses has, in the main, been attributed to the effective use of electron microscopy. Data generated from such investigations have provided the foundation for subsequent studies involving the above areas of diagnostic inquiry. Data presented in this paper overviews some of the successes of electron microscopy and highlights its continued role in the identification of ‘emerging pathogens’ that have potentional impact on trade, human health, medical health and conservational biology.
Estimation of Electron Beam Broadening in Specimen for Analytical Electron Microscopy
Authors: Lee C-W , Kidu S , Oikawa T , Shindo D
Published: July 2020

The electron beam broadening in specimens is a important issue to obtain a high spatial resolution expected by using a fine electron probe of nanometer order in analytical electron microscopy. Beam broadening mainly depends on electron diffusion in specimens. The theoretical equation on the beam broadening, which is based on single scattering approximation model for incident electrons, has been proposed by Goldstein et al.. in this work, the beam broadening was estimated experimentally by a TEM equipped with a field emission gun and the results were compared with the values theoretically obtained.

The sizes of the beam diameter with and without specimens were measured by using JEM-2010F and JEM 3000F TEMs, which are equipped with a field emission gun, being operated at 200 and 300 kV, respectively. The beam diameter was defined as the diameter containing 90% of the total electrons. The specimens used were amorphous SiO2, crystalline MgO and Si.
Progress with the IBM Very High Resolution STEM
Authors: Batson RE , Mook HW , Kruit P , Krivanek OL , Dellby N
Published: July 2020

The IBM high resolution STEM project has now reached the point where integration of new subsystems into the instrument is the main activity. During the past three years, we have demonstrated a 50meV EELS resolution using a high brightness electron monochromator incorporated into the electron gun [1, 2, 3], and better than 0.14mn spatial resolution using spherical aberration correction at 120KeV. [4] Recent effort has been to identify and remove many sources of instabilities in the original instrument; to rebuild several existing subsidiary pieces of equipment such as the ADF detector, the EELS spectrometer electron optical coupling, and the EELS CCD detection system; and to set up software and hardware control of each system to allow routine operation.

The new STEM column is summarized in Fig. 1. Briefly, the original VG gun flange has been lowered about 4cm, using a spacer, to allow insertion of the Fringe Field monochromator.
Substitutional Impurity Segregation to the Σ 5 (310)/[001] Stgb in Cu Doped Aluminum and Ag Doped Copper
Authors: Plitzko J M , Campbell G H , King W E , Foiles S M , Kisielowski C
Published: July 2020

The phenomenon of segregation is of long standing scientific interest and has been studied extensively, both theoretically as well as experimentally. For our investigations we have chosen the Σ5 symmetric tilt grain boundaries (STGB) in two face-centered cubic (FCC) metals, aluminum and copper. Both metals were doped with only 1 at% of the impurity species (Cu and Ag). One of our major goals in this study was to investigate the size effect on segregation of an impurity to distinct sites at the grain boundary. Therefore we have selected the Ag as an impurity in Cu and Cu as an impurity in Al. The latter one is of special interest for applications like interconnects in microcircuits, where one of the major controlling factors of electromigration is expected to be the diffusion or segregation of Cu atoms at Al grain boundaries.

The model grain boundaries have been fabricated with ultra-high vacuum diffusion bonding of single crystals which bonds the bicrystals under highly controlled environmental conditions.
Quantitative Field-Emission Transmission Electron Microscopic Study of Domain Boundaries in Cerium Doped A-Sialon Materials
Authors: Xu F , Bando Y , Wang C , Mitomo M
Published: July 2020

α-sialon is the isostructural derivative based on the a-silicon nitride (α-Si3N4) structure by partial replacement of Si by Al and N by O. The structure is considered to be stabilized by the incorporation into the large interstices (r=0.146nm) of a metal like Li, Mg, Ca and most small rareearths. Large rare-earth metal ions have been considered not to be able to enter the interstices in α-sialon structure until several recent successes in accommodating large cerium ions (r=0.103nm). This gives rise to questions of the location and distribution of these large cerium ions within the asialon structure. It has been found that α-sialon grains formed in Ce-Si-Al-O-N system are usually rich in a new structural defect which has been considered to be initiated specifically by the presence of cerium in the lattice. This new intergrown defect is identified as domain boundary in our present study by transmission electron microscopy (TEM).
Structural Characterization of Vanadium Carbide Using Core Ionization Electron Energy Loss Spectroscopy (Cieels) in Transmission Mode
Authors: González-Valenzuela C , Espinosa-Magaña F , Paraguay D. F , Duarte-Moller A
Published: July 2020

Vanadium carbide was purchased as powder at Aldrich with a 99.9% pure. Sample was prepared in the standard method for powder observation in a TEM.EELS experiments were carried out in a Phillips CM 200 STEM equipped with a Gatan 766 PEELS spectrometer. Experimental conditions for acquiring were the follows: a spot size of 500 nm, a chamber length of 400 mm and a detector aperture of 3 mm using a energy dispersion of 0.3 eV/channel with a beam energy of 200 KeV. Acquisition time was around 10 mn. taking an average of 100 spectra.

All the EELS spectra were corrected for background subtraction and multiple scattering deconvolution, before the fine structure analysis. The fine structure range was about 200 eV beyond the C-K edge located at energy loss of 283.8 eV and respect to the VL23-edge located at a energy loss of 513 eV.
On Lensless Imaging of Organics with Neutrons, X-Rays, Helium Atoms and Low Energy Electrons: Damage and Iterative Phase Retrieval
Authors: Spence JCH , Weierstall U , Fries J
Published: July 2020

Recent experiments with X-rays and high energy electrons have shown that image recovery from diffracted intensities is possible for non-periodic objects using iterative algorithms. Application of these methods to biological molecules raises the crucial problem of radiation damage, which may be quantified by Q = ΔE σi/σe, the amount of energy deposited by inelastic events per elastic event. Neutrons, helium atoms and low energy electrons below most ionization thresholds produce the smallest values of Q (see for TMV imaged at 60 eV). For neutrons (λ = 10-2Å, and deuterated, 15N-abelled molecules) Q is ∼3000 times smaller (∼50 times for λ = 1.8Å) than for electrons (80- 500keV) and about 4x 106 times smaller than for soft X-rays (1.5Å). Since σe for neutrons is about 105 times smaller than for electrons (and about 10 times smaller than for soft X-rays), a 105 times higher neutron dose is required to obtain the same S/N in a phase contrast image compared with electrons, if other noise sources are absent.
Light Atom Sensitivity of Quantitative HREM
Authors: Möbus G
Published: July 2020

Introduction: Modern TEM/STEM instruments with field emission gun and various analytical equipment allow the measurement of interfacial properties by a range of modes and techniques without exchanging the specimen. It is therefore useful to think of a criterion to assess the sensitivity of each technique, e.g. for the location of light atoms, by a commonly applicable formula.

Sensitivity measures: A “quantitative” TEM experiment is defined here as consisting of a digital comparison (e.g. via data difference or cross correlation) between experimental (E) and simulated (S) microscopy signal. The matching quality R = f(E,S) is to be optimised (minimum for data difference, maximum for cross correlation). The target quantity of the Q-TEM experiment is assumed to be the location or occupancy of a light atomic column in projection surrounded by heavier atoms in the core of an interface making use of dynamical enhancement effects.
An Interferometric Electron Ruler with Picometer Accuracy in Gauaging Lattice Displacement
Authors: Wu Lijun , Zhu Yimei , Tafto J
Published: July 2020

We report a novel technique to accurately measure interfacial lattice displacement by forming an electron probe close to a specimen in a manner similar to that originally proposed by Gabor to record a hologram. This method is based on the quantitative analysis of the interference pattern of shadow images in coherent electron diffraction. The approach is unique in that there are no adjustable microscope parameters, the contrast is strong even when the fault is viewed edge-on, and a large number of shadow images of the fault corresponding to different Bragg reflections can be studied simultaneously. Since it is an interferometric technique, the spatial resolution of the measurement is not limited by the wavelength of the fast electrons. An accuracy down to 1pm has been demonstrated in measuring the displacement associated stacking faults and grain boundaries in superconductors. It is, to our knowledge, the highest that has been achieved in measurements of displacement vectors.
Predictive Structure-Property Correlations for SrtiO3 Grain Boundaries
Authors: Prabhumirashi Pradyumna L , Johnson Kevin D , Dravid Vinayak P
Published: July 2020

In polycrystalline materials the trapping of charge at interfaces has a decisive influence on the electrical transport properties through the formation of electrostatic potential barriers. This can either be an intrinsic phenomenon or can be related to impurity segregation leading to complex defect centers. This plays a key role in technologically important systems, especially those having electrically active interfaces, e.g.,p-n junctions in semiconductors and grain boundaries in electroceramics.

Electroceramic oxides such as ZnO and SrTiO3 are common systems that exhibit the tendency of current control by internal potential barriers. While bulk measurements, either electrical (e.g. P-E, C-V, I-V), or optical (e.g. Raman) have contributed significantly to the understanding of charged interfaces, there are a very few direct observations of electrical activity at a nanometer level. For instance, it has been recognized that space charge and dopant segregation at the grain boundary are inter-related.
Quantitative EFTEM of Cr Grain Boundary Segregation in Cocrta
Authors: Wittig JE , Al-Sharab JF , Bentley J , Evans ND , Nolan TP , Sinclair R
Published: July 2020

Grain boundary Cr segregation provides magnetic isolation between the crystals in sputtered Co thin films used for longitudinal magnetic recording. Magnetic isolation decouples individual grains in order to increase coercivity, lower media noise, and allow for higher recording densities. These sputtered Co alloys grow with a strong [1120] texture owing to a body centered cubic (BCC) Cr underlayer. The sputtered Cr seed-layer has a [001]BCC growth texture and the BCC {110}cr planes lattice match with the hexagonal (0002)cr planes. This produces the desired condition of the easy axis of magnetization, [0001]co, in the plane of the magnetic layer. However, since two orthogonal orientations of the {110}cr planes exist parallel to the [001]cr growth direction, it is possible to nucleate two hexagonal Co grains with orthogonal variants of the c-axis that will impinge to form a 90° grain boundary. The well defined crystallographic texture of the Co-alloy thin film with random angle and 90° grain boundaries presents an opportunity to study the effects of boundary character on Cr segregation in hexagonal crystals.
Energy Loss Fine Structure Studies of Temper-Embrittled Lowalloy Steel
Authors: Papworth AJ , Williams DB
Published: July 2020

Temper-embrittlement in low-alloy steel has been attributed to the segregation of elements to the prior austenite grain boundary (PAGB). Auger electron spectroscopy (AES) has shown that the embrittlement of the PAGB is due to phosphorus segregation. The problem with this type of analyses is that only the PAGBs that fracture can be analyzed. More recent X-ray studies in a field emission gun scanning transmission microscope have shown that molybdenum, nickel, chromium manganese and phosphorus all segregate to PAGBs, and that these elements can be classified into two segregation groups; those PAGBs that contain nickel, manganese and phosphorus and those PAGBs that contain molybdenum, chromium and phosphorus. AES cannot determine conclusively, which segregation group is responsible for the embrittled PAGBs. The measurement of how embrittled the low-alloy steel has become, requires the knowledge, which PAGBs are embrittled and the percentage of these boundaries within a given volume.
Non-Stoichiometry at Dislocation Cores in Perovskites and Related Materials
Authors: Duscher Gerd , Kim M , Browning ND , Christen D K , Cantoni C , Pantelides S T , Pennycook S J
Published: July 2020

Z-contrast images and electron energy loss spectra (EELS) were obtained from low angle grain boundaries in SrTiO3 and YBa2Cu3O7-x (YBCO). Z-contrast images are easy to interpret and especially useful for positioning the beam to acquire EELS data from small sample areas [1], because both these techniques can be performed simultaneously.

In high-temperature superconductors even a single grain boundary can reduce the critical current by up to four orders of magnitude. The band-bending model can quantitatively explain this phenomenon. YBCO is a hole-doped superconductor with about one hole per unit cell for optimum doping at x close to zero. It has a structure closely related to the perovskite structure, and Z-contrast images have shown that the dislocation cores are made up of similar structural units as in SrTiO3.[2,3] Our EELS measurements show clear evidence for band bending effects around isolated dislocation cores in an undoped 8° low angle grain boundary.
Atomic Scale Analysis of Oxygen Vacancy Segregation At Grain Boundaries in Ceramic Oxides
Authors: Browning N D , Buban J P , Ito Y , Klie R F , Lei Y
Published: July 2020

The properties of ceramic oxides being developed for such varied applications as fuel cells, ionic transporting membranes, high-Tc superconductors, ferroelectrics and varistors are dominated by the presence of grain boundaries. Key to controlling the electronic properties of the grain boundaries in these materials is a fundamental understanding of the complex relationship between structure, composition and local electronic structure. The ability to characterize and directly correlate these parameters on the atomic scale is afforded by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Furthermore, the recent development of in-situ heating capabilities in the JEOL 201 OF STEM/TEM permits atomic resolution analysis to be performed at elevated temperatures and the interactions of grain boundaries with the oxygen vacancies determined.

Figure 1 shows an example of the type of experiment that can be performed using these methods.
Quantitative HREM: Reliable Structure Determination of Grain Boundaries in SrTiO3
Authors: Gemming Thomas
Published: July 2020

High resolution transmission electron microscopy (HREM) is an excellent experimental method to image grain boundary structures with atomic resolution. The advantage of the method is the short exposure time of only about one second that is needed to record an image. Other methods like Z-contrast imaging require much longer exposure times and are therefore much more prone to specimen drift during recording. However there is the remaining difficulty to HREM that the evaluation of experimental images is not straightforward and a thorough analysis of the images is necessary in order to deduce quantitative information with small error bars of only a few pm (10-15m). A second inherent difficulty common to all atomic resolution imaging techniques is that the information is retrieved from a very small area of a specimen. The question arising from that is: can we nevertheless be sure to obtain a representative answer to a “real world” material science problem? A positive answer to this question is given by the investigations presented here.
Microscopic Analysis of Twin Grain Boundaries in Alumina
Authors: Nufer S , Marinopoulos AG , Fabris S , Elsässer C , Kurtz W , Rühle M
Published: July 2020

Extended structural defects in α-Al2O3 (alumina), a technologically important, complex ceramic material were quantitatively analyzed with respect to grain boundary segregation, atomic and electronic structures using spatially resolved electron energy-loss spectroscopy (EELS), energy dispersive X-ray spectroscopy (EDS) and first-principles local-density-functional (LDFT) calculations. in this study the results of analytical investigations will be compared with the outcome of LDFT calculations.

The analytical measurements were performed with a dedicated scanning transmission electron microscope (TEM) VG HB501UX, operating at 100 kV and with a typical beam diameter of lnm. For the spatially resolved EELS a parallel electron energy-loss spectrometer (Gatan model 666) with an energy resolution of better than 0.8 eV was used. For the chemical analysis an EDS system (Noran-Gresham with a Si(Li) detector and a Norvar window) was applied. The detection limit of the EDX system for measuring interface excess is in the range of 0.3 atoms/nm2.
UHV-TEM/REM Study of Palladium Silicide Islands Grown on Silicon (111) 7×7 Surface
Authors: Takeguchi M , Mitsuishi K , Liu J , Zhang Q , Tanaka M , Furuya K
Published: July 2020

The growth of self-organized nanoislands and nanowires on a substrate has been extensively studied with a view to fabricating the new functional materials and advanced electric devices. in the present work, Pd silicide islands and wires grown on Si (111) 7x77×7surface were observed in situ by ultrahigh vacuum transmission and reflection electron microscopy (UHV-TEM/REM). Pd was deposited on Si (111) 7×7 surface at about 700 K using an electron beam evaporator attached to the column of a UHV microscope. Two kinds of specimens were prepared: a <111> oriented rectangular specimen with a thin area, whose (111) top surface was observed by plan viewed TEM, and a <110> oriented bulk rectangular specimen, whose (111) side surface was observed by REM

Figure la shows a REM image of Si (111) 7×7 surface. An incident electron beam is directed from the top to the bottom of the figure, which is foreshortened in the beam direction.
Impurity Effects on Shear Adhesive Strength of Tungsten Carbide Thermal Spray Coatings on Steel
Authors: Naidu Seetala V , Garber James D , Glassc Gary A
Published: July 2020

We have used High Velocity Oxy-Fuel (HVOF) thermal spray coating process to obtain tungsten carbide coatings on steel. It is important to control the powder quality and surface roughness of the substrate in the thermal spray coating process to obtain good adherence. The adhesive strength is greatly effected by the interfacial impurities. Most commonly used in the thermal spray industry is Al2O3 grit abrasive for good surface roughness of steel substrate to produce anchor patterns for the coating. The previous studies indicated that some fine Al2O3 particles are trapped in the rough surface grooves during this process. The ring shear test method, described previously, appears to give the most accurate results on shear adhesive strength. The ring shear strength test was comprised of a 0.02” thick and 0.25” wide ring coating on a 1” diameter cylindrical substrate rod. This rod is placed in a disk with a cylindrical hole of the rod size and an incremental pressure is applied on the rod.
Characterization of Gan/Sapphire Interface and the Buffer Layer by TEM/AFM
Authors: Shea B , Sun-Paduano Q , Bliss D F , Callahan M C , Sung C
Published: July 2020

Interest in wide band gap III-V nitride semiconductor devices is increasing for optoelectronic and microelectronic device applications. to ensure the highest quality, TEM analysis can characterize the substrate and buffer layer interface. Measurements taken by TEM reveal the density of dislocations/cm2 and the orientation of Burger's vectors. This information allows for changes to be made in deposition rates, temperatures, gas flow rates, and other parameters during the processing.

The GaN/sapphire samples grown at AFRL were produced in two consecutive steps, first to provide a thin buffer layer, and the other to grow a lum thick epitaxial film. Both growth steps were prepared using metallic organic chemical vapor deposition (MOCVD) in a vertical reactor. Buffer layers were prepared using a range of temperatures from 525 to 535°C and with a range of flow rates and pressures in order to optimize the nucleation conditions for the epitaxial films.
Microtexture Studies of Extruded Aluminum Using Electron Backscatter Diffraction
Authors: Claves S R , Misiolek W Z , Williams D B
Published: July 2020

Electron backscatter diffraction (EBSD) is a powerful tool used for the characterization of deformed microstructures and has been successfully applied to determine the microtexture of specific regions of bulk samples. The work presented here is a continuation of previous analyses investigating the microstructural response of 6xxx aluminum extrudates to complex die designs. Specifically, the grain orientations across longitudinal welds produced from porthole dies is being studied.

Previous work examined the cross section of a sample that was extruded using a specially designed die that would position the weld in the center of the part. This specimen, shown in Figure 1, is a simple, solid, rectangular shape produced under controlled conditions. The other sample being studied, seen in Figure 2, was part of an actual extrusion run, conducted with typical industrial parameters. This sample is part of a complex shape that uses a porthole die to produce hollow sections.
Specimen Thickness Effects on EBSD Patterns in the Sem
Authors: Michael J R
Published: July 2020

Electron backscatter diffraction (EBSD) in the SEM has become a widely used technique for both automated orientation mapping and the identification of unknown crystalline phases. Despite the rapidly growing use of this technique for the above applications, there has been relatively little fundamental research concerned with determining the thickness of the surface layer that generates the EBSD pattern. EBSD patterns are related through reciprocity to electron channeling patterns. Based on this assumption the thickness of the surface layer that an EBSD pattern is generated in is 2 or 3 extinction distances. Extinction distances at low SEM voltages (10-20 kV) are quite short. Thus, EBSD patterns are generated in very thin surface layers. This paper will discuss the results of a study of the information depth of EBSD in the SEM.

Previous research has attempted to determine the information depth of EBSD by obtaining patterns from samples that have had layers of other crystalline or microcrystalline material deposited on the surface.
Which is Better for Protein Imaging: Phase Contrast TEM or Annular Dark Field STEM?
Authors: Rez P
Published: July 2020

In a landmark paper Henderson compared X-ray, neutrons and electrons for protein structure determination. He showed that electron microscopy should be superior to X-ray or neutron diffraction in terms of dose for a given resolution. in addition he presented a theoretical analysis to determine the smallest size molecule whose structure could be determined by phase contrast microscopy. Although he qualitatively considered amplitude contrast mechanisms and concluded they were inferior to phase contrast, no explicit numerical analysis was performed. It has been implicitly assumed that bright field phase contrast imaging is the optimal technique for imaging small biological molecules. Protein specimens are usually embedded in some medium such as ice or glucose. Since they must give a very low contrast it seems reasonable to expect that bright field techniques for these weakly scattering objects would be inferior, given that a weak signal is sitting on large background.
HRTEM and EELS Study for Superconducting and Non-Superconducting (Cu,Cr)-1212 Cuprates
Authors: Anan Y , Asaka T , Kurami H , Hatano J , Tsutsumi S , Kimoto K , Matsui Y
Published: July 2020

The crystal structures of high temperature superconducting cuprates consist of alternative stacking of charge-reservoir (CR) block and conduction block. in case of YBa2Cu3Oy, (YBCO), CR block contains one-dimensional Cu(I)-O chain and BaO layers, and conduction block contains two-dimensional Cu(II)O2 planes and Y layers. YSr2Cu3Oy (YSCO), where Ba-sites of the YBCO are replaced by Sr completely can be obtained only by high-pressure synthesis. However, by replacing Cu(I) partly by Cr, YSr2Cu3-xCrxOy can be obtained even under ambientpressure conditions. The compound YSr2Cu2.8Cr0.2Oy (x=0.2) is non-superconductive, but, superconductivity is induced by partial replacement of Sr-sites with Ba; the compounds with YSr2-xBaxCu2.8Cr0.2Oy (x≤0.5) is non-superconductive, but the compound with x≥1.0 is superconductive. in order to obtain the structural information about the transition to superconducting phases, the effect of the Ba substitution is investigated by transmission electron microscopy (TEM).In the present study, the compounds with YSr2-xBaxCu2.8Cr0.2Oy (x=0-1.5) are examined by high resolution TEM (HRTEM) and electron energy-loss spectroscopy (EELS) to elucidate structural and electrical modification induced by Ba-substitution.
Tem Study of Nano-Crystals in Strontium Ion-Implanted Cubic Zirconia
Authors: Zhu S , Wang LM , Wang S X , Lian J , Ewing RC
Published: July 2020

Yttria stabilized zirconia (YSZ) is an important oxygen ion conducting solid electrolyte. YSZ is used in oxygen sensors, oxygen pumps, and fuel cells. Perovskite-type oxides of general formula ABO3 are also of fundamental significance due to their electrical and electro-optical properties. SrZrO3 is a promising material- for application as protonic conductor. in this paper, we present electron microscopy analysis of the formation of SrZrO3 nano-particles in the top surface of YSZ single crystal after ion implantation. These results demonstrate a unique process for obtaining mixed-conducting oxides in the surface layer of YSZ. in addition, it is important to study the behavior of strontium in YSZ because of the potential application of YSZ as an inert fuel matrix for “burning“ excess plutonium in nuclear reactors.

400 keV strontium ions have been implanted into YSZ at room temperature to a fluence of lxl021 ions/m2.
The Charge Ordering Behavior of Colossal Magnetoresistive (CMR) Layered Compounds La2-2xSr1+2xMn2O7 (x = 0.5 ∼ 0.6)
Authors: Luo Z P , Miller D J , Mitchell J F
Published: July 2020

In colossal magnetoresistive (CMR) materials, large changes in physical properties stem from the interplay between charge ordering (CO) coupled with orbital and magnetic orderings. Thus detailed microstructural studies are important in understanding these changes in physical properties. In-situTEM observation is a very useful approach to study CO transitions in these CMR compounds. We have recently studied the CO behavior of the three-dimensional perovskite Nd1/2Sr1+2xMnO3. in this work, we report the CO of two-dimensional naturally layered compounds La2-2xSr1+2xMn2O7 (327 phase), where x is the hole doping level and varies from 0.5 to 0.6 in this work.

Thin foil TEM specimens were prepared from polycrystalline bulk samples by conventional thinning and ion milling method at liquid N2 temperature. The in-situ TEM work was carried out in the Electron Microscopy Center at Argonne National Laboratory using a Philips CM30 with a liquid N2 cold stage, and a Hitachi H-9000 with liquid He cold stage.
Effect of High Heating Rates on Microstructure of Alumina and Aluminum Titanate Ceramics
Authors: Stanciu Lia A , Groza Joanna R
Published: July 2020

In conventional sintering, high heating rates are often used to enhance densification and reduce grain growth. The essence of this concept is to use fast heating rates to favor densification instead of grain growth, if the activation energy for densification is greater than that for grain growth. At low temperatures, surface diffusion is the most effective sintering mechanism but is associated with grain coarsening. Therefore, a high heating rate may take the system for densification at high temperatures before surface diffusion causes grain growth and decreases the sintering driving force. Field activated sintering technique (FAST) is a newly developed sintering method, which applies an external electrical field to enhance densification. The method applies pulsed and continuous current to powders subject to a modest pressure (< 100 MPa). Electrical current application enables fast heating rates. The sintering cycles are very short, typically less than 10 minutes for full densification.
Toughening of Brittle Materials by Dislocation Cells
Authors: Saka H , Moon W-J , Horiuchi S , Uchimura S
Published: July 2020

Many attempts have been made to improve the fracture toughness of brittle materials such as ceramics. Most of the methods developed so far make use of metallurgical processes, for example, phase transformation, refining of grains, formation of composite materials. However, these methods can not be applied universally to brittle materials which do not have such a useful metallurgical processes.

Moon and Saka (1) recently showed that the fracture toughness Klc of a YAG single crystal the sub-surface of which is damaged by micro-Vickers indentation at room temperature, followed by annealing at high temperatures is improved by a factor 2 from 1.13 to 2.26MPam1/2. The fracture toughness Klc was evaluated by measuring the length of cracks which initiate at the corner of Vickers indentation(2). Transmission electron microscopy of the subsurface reveals the healing of cracks introduced by room-temperature indentation and formation of dislocation cells. The thin foil specimens were prepared using a focused ion beam(FIB) technique(3).
Variation of Size and Alignment in Carbon Nanotubes by Changes of Growth Condition
Authors: Provencio Paula P , Siegal Michael P , Overmyer Donald L
Published: July 2020

Carbon nanotubes have previously been grown on Ni coated glass, aligned vertical to the substrate over a multi-centimeter square area1. Under vacuum, the aligned nanotubes were grown below 666° C (strain point of the best display glass) by plasma-enhanced hot filament, chemical vapor deposition. It was found, the size and alignment of the nanotubes could be varied by changing the dwell time and the thickness of the catalytic Ni layer by plasma etching. in more recent, ongoing studies, the size of carbon nanotubes is varied by changing the growth temperature and dwell time under acetylene/nitrogen atmosphere using chemical vapor deposition onto W and Ni coated Si.

Multiwall carbon nanotube films are grown using a thermally-activated chemical vapor deposition process. Thin Ni catalyst layers are sputtered onto W-coated Si(100) and reduced in a 600°C CO anneal. Nanotubes then grow at temperatures ranging from 630 - 790°C in an acetylene/nitrogen mixture.
The Expression Patterns of Semaphorin Genes 3b, 4a, 4f, and 6c in the Lymphoid Tissue of Mice Found Through in Situ Hybridization
Authors: Beheshti Sayeh , Matthes David
Published: July 2020

The semaphorin family consists of a set of secreted and transmembrane proteins which contain a domain of approximately 500 amino acids called the semaphorin domain. The investigation of the role of semaphorin proteins in the nervous system has established them as chemorepellents of axons. Recent studies have identified the semaphorin proteins on the surface of cells in the immune system and in the genomes of two lytic viruses. These strongly suggest the possible involvement of the semaphorin proteins in the immune system. This study aims to understand the expression patterns of four semaphorin genes, Sema3B, Sema4A, Sema4F, and Sema6C in the lymphoid tissues of wild type mice. These proteins were chosen to represent the three subfamilies III, IV, and VI. The first family contains secreted proteins which have immunoglobulin domains (III), the second contains transmembrane proteins which have immunoglobulin domains (IV), and the third contains transmembrane proteins which do not have immunoglobulin domains (VI).
The Effects of Light Intensity on Plastid Organization of the Toxic Dinoflagellate Prorocentrum Hoffmanianum: A Correlated Tem and Fluorescence Microscopy Study
Authors: Schuette S , Schmitt S , Tindall D
Published: July 2020

Toxic dinoflagellates gained notoriety for their devastation to coastal and island economies, causing damages totaling in the millions of dollars that included losses of harvestable resources, clean-up costs, as well as cancellation of holiday reservations in popular tourist/recreational areas.3 These red tide blooms sparked an urgency for obtaining information pertaining to the dynamics of toxin production, but understanding the mechanisms of toxin production have proven to be difficult to pin point. This study tested the hypothesis that cells grown under various light intensities undergo structural and compositional changes and served as a basis for future biochemical studies of Prorocentrum  hoffmanianum.

We examined ultrastructural changes to the chloroplast in cells from monocultures of Prorocentrum hoffmanianum grown in three different light intensities, via a transmission electron microscope and a fluorescent light microscope. The full or normal growth chamber intensity of ca. 5000 lux represented the control group referred to as the full light treatment.