bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytosolic And Membrane Proteins In Plant Cytokinesis
Authors: Bednarek S Y , Dickey C
Published: July 2020

The mechanism of cytokinesis in higher plants is distinct from that of animal and yeast cells. Dividing plant cells are separated by the de novo construction of the cell-plate across the inside of the cell. Assembly of this new organelle is directed by a specialized cytoskeletal structure called the phragmoplast, a unique macromolecular scaffold that appears late in mitosis and is composed of intermediate filaments, microfilaments, and microtubules. Secretory vesicles are guided along the phragmoplast cytoskeleton toward the equatorial region of the structure where they coalesce and fuse to form a membranous tubular-vesicular network within which cell wall biosynthesis is initiated. A smoother more plate-like structure develops and extends radially outward as additional vesicles are added to the growing margin of the cell-plate until it ultimately fuses with the parental plasma membrane yielding two daughter cells separated by a common cell wall and extracellular space.
Three-Dimensional Visualization Of Miotic Chromosomes In Maize Trisomy 6
Authors: Cheng Wayne Y , Lee Thomas C , Walden David B , Cheng Ping-chin
Published: July 2020

The ability to visualize the chromosomes, especially in three-dimensional (3D) space, has great benefits for the understanding of genes’ function. The availability of various trisomic genotype in maize provides an excellent system for the study of 3D chromosome arrangement at various developmental stages. Laser scanning confocal microscopy and digital deconvolution technique is best suited for this type of work. A preliminary database on the three-dimensional arrangement of Ohio43 inbred line has been established; this information is essential for the evaluation of the effect of additional chromosome in trisomy genotypes.

Tassel inflorescence of maize (Zea mays L.) trisomy 6 in Ohio43 background were collected from the field station at the University of Western Ontario in London, Ontario, Canada, during the summer of 1998. Tassels at the proper developmental stages were fixed in 3:1 (95% EtOH / acetic acid) solution and stored at room temperature. After dissection from the spikelet, anthers were treated with the Feulgen-method, dehydrated in ethanol series and cleared in methyl salicylate.
Ultrastructural Analysis Of The Aseptate Gregarine Pterospora, A Parasite of The Bamboo Worm Axiothella Mucosa.
Authors: Landers Stephen C
Published: July 2020

The gregarine Pterospora is a parasite found in the body cavities of bamboo worms (Polychaeta: Maldanidae). The gamont stage of Pterospora has a bizarre structure with a main cell body and multiple posterior cytoplasmic extensions (Fig. 1). The cells are found in pairs within the coelom of the host and move by cytoplasmic streaming as they fill and empty their posterior extensions. Reports of this parasite in the literature are few (see references 1 & 2 for a review) and no ultrastructural details have been published regarding the genus. This study examines the fine structure of the gamont stage with particular emphasis on the structure of the pellicle.

The maldanid worm Axiothella mucosa was collected by shovel in St. Andrew Bay, Florida and returned to the Troy State University campus. Pterospora spp. gamonts were pipetted from minced setigers of the worms and fixed in 3% glutaraldehyde buffered with 0.05M sodium cacodylate, pH 7.5, for 1-6 hours.
Tissue Response To Three Mixtures Of A Bone Substitute Material In Tooth Extraction Sites
Authors: Krizan K E , Lew D , Burton R , Laffoon J , Keller J C
Published: July 2020

The objective of this study was to evaluate the biological responses of three different mixtures of a bone substitute material placed in tooth extraction sites to determine which mixture best enhances bone formation. Under general anesthesia three adult mongrel canine had bilateral extractions of the second and fourth premolar bicuspids. Each site was modeled into 3-wall defect with box-like dimensions and having the window on the buccal (outer) side of the mandible. A synthetic hydroxyapatite bone cement (HAC) was prepared three different ways: 1) 2.5 gms HAC + 0.75 cc sterile water (W); 2) 2.5 gms HAC + 0.75 cc 2% Hydroxypropylmethylcellulose in sterile water (HPMC); 3) 2.5 gms HAC + 0.75 cc Sodium Phosphate [45mM/15mL Phosphate + 60 MEq/15mL Sodium] (SP). Each mixture was syringe injected into a different extraction site and the fourth site received no cement to serve as a control site, and after sites were filled, a periodontal flap closure was accomplished with a 4-0 VICRYL suture.
Identification Of Scavenger Receptor Sr-Bi In The Endothelial Cells And The Smooth Muscle Cells Of Rat Aorta In Vitro
Authors: Yeh Y C , Hwang G Y , Yang V C
Published: July 2020

The class B,type I scavenger receptor (SR-BI) was the first molecularly well defined cell surface receptor which binds HDL and mediates the selective uptake of HDL cholesteryl ester. It is expressed primarily in liver and steroidogenic tissues. However, the recent studies also suggested a potentially important role of SR-BI in the initial steps of cholesterol efflux in the peripheral tissues. In this study, we have used immunoblotting and immunofluorescence microscopy to study the expression and subcellular localization of SR-BI in the cultured endothelial cells and the smooth muscle cells of rat aorta.

A peptide containing residues 495 to 509 from mSR-BI plus an NH2-terminal cysteine was coupled to hemocyanin. Then the peptide was used to generate mSR-BI495 antiserum in New Zealand white rabbits. The cells from the aortic ring of 1-month-old Spraque-Dawly rats were grown in the dishes containing complete medium (Dulbecco's modified Eagle's medium with 10% fetal bovine serum) and incubated at 37°C in 95% air/ 10 % CO2 atmosphere for 3-4 days.
Electron Tomography of Swollen Rigor Fibers of Insect Flight Muscle Reveals the S2 Fragment of Myosin
Authors: Wang Yunxun , Winkler Hanspeter , Reedy Michael K , Reedy Mary C , Taylor Kenneth A
Published: July 2020

We have used electron tomography of rigorized fibers of insect flight muscle swollen by immersion in dilute buffer (†1mM MOPS, pH 6.8), to reveal the 3-D arrangement of the myosin S2 fragment for the first time. S2 is an α-helical coiled-coil structure that connects the myosin head to the thick filament backbone. It is usually invisible in electron micrographs because of its close proximity to the backbone. The increase in inter-thick filament spacing from 45 nm to 55 nm pulls the S2 away from the filament backbone making it easier to identify. A total of 4 tomograms have been calculated by our standard method which involves collecting images using non-uniformly spaced tilt angles, cross correlation alignment, area matching and Whittaker-Shannon interpolation of the 3-D transform. A projection of one of these tomograms is shown in Figure 1. in raw tomograms S2 appears as a rod-like structure that originates at the thick filament surface to connect to both lead and rear crossbridges of rigor. S2 segments are particularly well resolved at the ends of the thick filament (Fig. 2), where in some cases it appears that the myosin subfilaments are separated from the backbone. Both the azimuthal direction and axial angle of S2 are variable.
Recognition, Specificity, Scanning Probe Microscopy and Biomaterials
Authors: Ratner Buddy D , Luginbühll Reto , Overney Rene , Garrison Michael , Boland Thomas
Published: July 2020

Although scanning probe microscopy (SPM) can generate images of surface topography, this class of techniques is exceptionally valuable in its ability to provide quantitative and chemically specific information about biomaterial surfaces with high spatial definition. Since engineered biomaterials are designed to deliver chemically defined information, often arrayed in specific geometries, tools that can characterize such materials are needed.

A few years ago, we demonstrated how the atomic force microscope (AFM) could precisely distinguish between each of the four nucleotide bases that comprise DNA, measure the nucleotide-nucleotide force of interaction and spatially localize that information on a surface (1). in particular, we found that the nucleotide bases could self-assemble on gold. The assembly process was imaged using scanning tunneling microscopy (STM) and this led to an understanding of the structure of the assembled film. The assembled film structure was further characterized using electron spectroscopy for chemical analysis (ESCA) and secondary ion mass spectrometry (SIMS).
Characterization of the Source/Drain Region in Mos Devices by Scanning Transmission Electron Microscopy
Authors: Topuria T , D. Browning N , Ma Z
Published: July 2020

The advancement of metal-oxide-semiconductor (MOS) technology towards sub- 100nm device dimensions presents several technical difficulties. Nanoscaling in MOS devices is specifically governed by difficulties in the formation of ultrashallow junctions for the source/drain regions with the requirement of low resistance and low leakage currents. The use of a silicide (forming Schottky contacts at the source and drain) instead of the conventional ion implanted Si for the contacts allows a reduction in the contact area to be made, due to lower serial resistance per unit area of the silicide. According to the specific contact resistance dependence on the Schottky barrier height (ΦSB) and active dopant concentration (ND),
Three-Dimensional STEM for Observing Nano-Structures
Authors: Tanaka Nobuo , Koguchi Masanari , Kakibayashi Hiroshi , Tsuneta Ruriko , Kase Kiwamu , Iwaki Masaya
Published: July 2020

Three-dimensional (3D) observation is one of the important trials of future TEM and STEM methods. in the field of biological science, 3D-observation has already become general because the biological materials are usually amorphous and computed tomography (CT) routines can be effectively used. The CT assumes that the image intensity is linearly proportional to the projection of material density. in a crystalline specimen, however, this linearity does not hold due to the dynamical diffraction effect depending on spepimen thickness and incident directions of electron beam. High-angle annular-darkfield STEM (HAADF-STEM) and EDX mapping images could meet this requirement of the linearity because their image intensity are little affected by the dynamical diffraction effect.

Our 3D-STEM is based on a 300 kV FE-TEM/STEM(Hitachi HF-3000) equipped with a specially designed eucentric specimen stage with double spherical fulcra, a newly developed dark/bright field STEM detectors, a 3D-sampling system and a 3D-imaging processor for 3D topography and tomography.
Characterization of Microlens Structures Fabricated in Cd1-xZnxTe and Cdte/Si IRFPA Substrate Materials
Authors: Boyd PR , Lee U , Little J , Morton D , Stoltz AJ , Benson JD , Martinka M , Dinan JH , Banish MR
Published: July 2020

The ternary II-VT alloy Hg1-xCdxTe has become the material of choice for many infrared detector applications. Current state of the art Hg1-xCdxTe infrared focal plane arrays (IRFPAs) are constructed as hybrid structures consisting of an epitaxial sensing layer of Hg1-xCdxTe on either a CdTe or Cd1-xZnxTe substrate, hybridized to a silicon readout circuit chip. For backside illuminated structures, like the typical infrared Hg1-xCdxTe detector array, multilayer antireflective coatings (AR) are required on the backside of the detector chip. The next generation of higher performance IRFPAs will be based on high densities of smaller detector pixels fabricated on large area monolithic heteroepitaxial substrate materials. Since the ultimate performance of photovoltaic diodes of this type is determined by the signal to noise ratio of the device, reducing the size of the pixels while lowering the undesirable noise currents in the devices also reduces the amount of signal generated by the diode.
Lipoblastoma and Lipoblastomatosis in Infancy and Childhood: Histopathologic, Ultrastructural and Cytogenetic Features
Authors: Barrish J , Dilley A , Brandt M , Patel D , Zhu S-H , Nichols R , Hicks J
Published: July 2020

Adipose tumors during the first decade of life are infrequent, composing about 6% of all soft tissue neoplasms in children. Lipoblastomas are rare benign tumors occurring in infancy and early childhood and arising from embryonic white fat. The tumors may infiltrate tissue locally and may be of considerable size, but lack the ability to metastasize. The tumor may be an isolated well-encapsulated mass (lipoblastoma, Figure) or lack encapsulation and be locally infiltrative (lipoblastomatosis). Although a benign tumor, lipoblastomas tend to recur, and may resemble myxoid liposarcoma, a malignant tumor.

We report 26 cases of lipoblastoma/lipoblastomatosis over a 15 year period at Texas Children's Hospital. There was a slight female predilection (1.2 F:1.0 M). The most common symptom was a painless mass of increasing size. The trunk (48%), extremities (33%), head and neck (15%), and lung (4%) were the tumor sites.
Oxidative Stress in Galactose Induced Diabetic Retinopathy in Inducible Nitric Oxide Synthase Knockout Mice
Authors: Ann Ellis E , Grant Maria B
Published: July 2020

Oxidative stress and inducible nitric oxide synthase (iNOS) have been implicated in endothelial cell dysfunction in diabetic retinopathy by formation of peroxynitrite, a cytotoxic product of superoxide and high levels of nitric oxide. Spontaneous diabetic models do not allow for separating the oxidative stress as a result of hyperglycemia from that of the nitric oxide system. in addition chemicals such as streptozotocin which can induce diabetes in animal models cause oxidative stress and induce iNOS before the onset of hyperglycemia. Galactose has been used to induce non-insulin dependent diabetes in mice and rats while gene knockout mice provide a means to study the role of specific NOS components. This study used cytochemical localization of hydrogen peroxide produced by NADH oxidase, a marker for superoxide production, and immunocytochemical localization of nitrotyrosine, a marker for nitric oxide formed radical peroxynitrite, to investigate the role of oxidative stress and the nitric oxide system in galactose induced diabetic retinopathy in iNOS knockout (iNOS%) mice.
Morphologic Assessment of Plasma Membrane Blebbing Provides a Sensitive, Early Indicator of Low Dose Lidocaine Neurotoxicity
Authors: Johnson ME , Dadarkar P
Published: July 2020

Background: Lidocaine is a local anesthetic that is frequently used for spinal anesthesia. in clinical and animal studies, lidocaine is associated with an increased risk of spinal neurotoxicity following spinal anesthesia. The mechanism of lidocaine neurotoxicity has not been fully elucidated, but it does not involve blockade of sodium channels, the mechanism by which lidocaine causes local anesthesia. Previous in vitro studies assessing cytoplasmic calcium, nerve conduction and action potential generation, and cell death, have demonstrated overt neurotoxicity at higher concentrations of lidocaine (≥ 2% [74 mM] of the hydrochloride formulation), but equivocal results at lower concentrations. Clinically available preparations of lidocaine for spinal anesthesia contain 5% or 2.5% lidocaine hydrochloride. in most cases, lidocaine mixes rapidly with cerebrospinal fluid after injection for spinal anesthesia, so that lower concentrations are more clinically relevant. We have therefore evaluated morphologic assessment of plasma membrane blebbing as a more sensitive assay of neuronal injury by lidocaine.
“Casino V2.0 : An Advance Simulation Tool for Scanning Electron Microscope Users”
Authors: Drouin D , Couture AR , Gauvin R
Published: July 2020

The topic of this paper is to present a new Windows™ environment version of the CASINO Monte Carlo program. The goal of this program is to assist scanning electron microscope users in their routine analysis and also in more advanced topic such as electron beam lithography for example. Based on a single scattering algorithm, this software is specially designed for low beam interaction in a bulk and thin foil. This program uses tabulated Mott elastic cross-sections, which benefit of both fast calculation and accurate interaction at low beam energy. At the moment CASINO can either be used to generate X-rays or backscattered electron signals. The program used simple two-dimension geometry to represent real sample. in this version, vertical and horizontal planes can be generated to allow cross-section representation or multi-layers analysis. Then beam can be scanned across different regions to produce X-ray linescan or bascattered electron profiles.

Many new convenient features have been added to the version 2.0 of CASINO. The new interface lets the users to consult the results as the simulation is still in progress.
The Single Platform Concept for the Operation of Analytical Equipment
Authors: Rowlands N , Bagnall. K
Published: July 2020

The movement towards a single platform concept for the operation of multi-functional analytical instruments has progressed over the past 10 years largely due to the availability of powerful computer technology combined with the need of ease of use to increase productivity. Other factors include the need to share data obtained from these increasingly complex instruments, and to transport these data in an easily managed format and the possibility of storing large amounts of data generated from projects.

Initial efforts in this field were generated by the need for computer control of complex instrumentation such as TEMs, EPMAs and dual beam instruments. Microprocessors enabled easy alignment, storage of stage parameters and digital image acquisition. with the boom in the semiconductor industry it was necessary to design tools that could be operated by individuals who did not possess the same amount of knowledge as the scientists and technologists of the previous generation. Early attempts at integration of techniques on a single platform were restricted, largely due to limitations in the capacity of the computers employed in controlling these tasks. Indeed, in some cases this actually increased the complexity of some instruments due to a profusion of microprocessors controlling the various analytical components of the larger analytical machines.
Chromatic Aberration Correction of a Low-Voltage SEM using a Wien Filter: Adjusting the Correction Strength
Authors: Steffen T , Tiemeijer PC , Krijn MPCM , Mentink SAM
Published: July 2020

The resolution of state-of-the-art low-voltage scanning electron microscopes (LV SEM), which is currently limited by the chromatic and spherical aberrations of the objective lens, can be improved by incorporating an aberration correcting device. At present four different concepts are discussed in literature: Zach and Haider demonstrated that a quadrupole/octupole corrector can correct both chromatic and spherical aberration. Rose proposed a Wien filter for chromatic aberration correction, which has relaxed stability requirements. Recently, we reported a simplified version of this corrector and showed that a spherical aberration corrector can be integrated in a Wien filter. Henstra and co-workers suggested a purely electrostatic corrector that can correct both chromatic and spherical aberration.

For all these concepts problems may arise when the lens-to-sample (working) distance for an aligned corrector is to be changed. in general, the corrector settings depend on the ratio Cc/f2, where Cc and f denote the coefficient of the chromatic aberration and the focal length of the objective lens, respectively. When the working distance is changed, this ratio is no longer perfectly matched to the corrector settings. The tedious realignments and readjustments, which then seem necessary, can be avoided by using a doublet objective lens as illustrated schematically in Figure 1.
In-Situ Ion Milling in the Transmission Electron Microscope (TEM) Outlook to a New Preparation Technique
Authors: Gnauck Peter , Burkhardt Claus , Plies Erich , Nisch Wilfried
Published: July 2020

Recent developments in transmission electron microscopy put high demands on specimen preparation. in general the imaging quality is not limited by the performance of the microscope but by the quality of the specimen. in order to achieve a spatial resolution of 0.1 nm in HRTEM undamaged samples with a thickness below 10 nm are required. in energy filtering analytical electron microscopy (EFTEM), a constant specimen thickness over large areas and very low contamination is needed.

Conventional ion-milling techniques for TEM specimen preparation are essentially blind. Thus, it is left to chance whether the specimen detail of interest is suitable for TEM-imaging (many specimen areas are too thick). Another problem is the reaction of the specimen with the atmosphere during the transfer from the preparation stage to the microscope, which makes it very difficult to obtain the clean specimen surfaces that are needed in analytical EFTEM. Especially in high-resolution electron microscopy and electron holography the formation of amorphous oxidation and contamination layers on otherwise crystalline materials may seriously reduce the quality of high resolution images of the crystal structure.
The Future of Automation: A Microscopist’s Wish List
Authors: Crozier P A
Published: July 2020

The considerable improvements in computational power and the increased sophistication of programming techniques now make it possible to automate many aspects of electron microscopy [1]. Automation offers several important advantages over manual operation. Automation of microscope operation permits novice microscopists to obtain data relatively easily thus increasing instrument utilization. The experienced microscopist should be able to acquire data more rapidly and with greater ease compared to manual operation, resulting in increased efficiency. Alignment of energyfilters and proposed Cs correctors are difficult and time consuming even for experienced microscopist and stable alignment algorithms are critical for practical use. Automation is essential for extensive statistical sampling of microstructures and can permit experiments to be performed that were previously impractical. For example, spectrum imaging involves acquisition of thousands of spectra from a predefined area. The acquisition and processing of such large volumes of data cannot be accomplished without the aid of automation. The future prospects for automation are exciting, although it is important to carefully consider the relationship between the computer controlled microscope and the operator. Here I give a personal perspective on approaches to automation which increase the power and efficiency of modern transmission electron microscopes.

The degree of automation is an important consideration that is related to the complexity of the analysis strategy. Some analysis situations call for repetitive sampling of a well-defined quantity such as layer thickness or particle size. These simple repetitive operations are ideal candidates for total automation. For many applications of automation it is necessary not only to acquire the data but also to process the data and extract the quantity of interest.
High Resolution Backscatter Electron (BSE) Imaging using the Autrata Modified YAG BSE Detector: Comparison of an In-lens Hitachi S-900 FESEM with the Below-the-Lens Hitachi S-4700 FESEM
Authors: Erlandsen Stanley L , Chen Ya , Frethem Chris
Published: July 2020

To obtain high resolution backscatter electron (BSE) images in field emission SEM (FESEM), one must consider selection of accelerating voltage, beam current, working distance between the specimen and the backscatter detector (in-lens or below-the-lens position for the specimen), the type of BSE detector, and the type of metal used to coat the specimen to improve conductivity and signal collection [1]. A new generation of below-the-lens FESEM have been tested for BSE imaging on biological samples, but no information exists on whether or not high resolution imaging is possible. Here we report the comparison of detection of a colloidal gold standard (6, 12, 18 nm) by high resolution BSE imaging using Autrata-modified YAG detectors in an in-lens FESEM and in a below-the-lens FESEM.

Standards were prepared by mixing colloidal gold particles of 6 nm, 12 nm, and 18 nm. The gold particles were attached via poly-l-lysine to glass chips and coated with <1 nm Pt by ion beam sputtering.
The Application of Ab Initio Direct Methods with Electron Diffraction for Solving Zeolite Structures
Authors: Sinkler Wharton
Published: July 2020

Recently a number of reports have been made in which direct methods (DM) were used to solve bulk inorganic crystal structures with electron diffraction (ED) data, either ab initio or in a combined approach using phase information from images. This paper reports ab initio application of DM to experimental ED data from the zeolite mordenite. Data from mordenite [001] were taken using a JEOL 3010 TEM at 300 kV. For collecting data, a small condenser and spot size were used to obtain a defocused probe 50 nm in size positioned over the edge of a thin area. Patterns were recorded with a CCD camera. Fig. 1 compares experiment with modeled kinematical data based on a published structure. Phase determination by DM was performed with the minimum relative entropy approach. As a test, ab initio DM was performed on modeled kinematical data.The result, shown in Fig. 2, is not distinguishable from a picture of the projected potential.
Real-time EELS spectra classification using Principal Components Analysis (PCA) and Artificial Neural Networks (ANN)
Authors: Åstrand P-G , Csillag S
Published: July 2020

Recent developments in detector technology [1] for EELS and Energy Filtered TEM has made possible to obtain large number of spectra and energy filtered images during very short exposure times. This in turn opens the exciting possibility of studying time dependent processes in the electron microscope, during exposure to the electron beam as well as the study of different radiation sensitive samples which are being degraded during lengthily data recording. This kind of data recording generates a large amount of data and manual data analysis should be avoided in order to be able to fully benefit from the improved sensitivity and increased speed of these new detectors. Thus a fast, real-time data analysis system is highly desirable.

A system for real-time data analysis (spectra classification) of data generated from such a detector has been simulated in a program based on the object oriented C++ framework ROOT [2][3].
Analysis of The Electronic Structure of Threading Dislocations in GaN Using Multiple Scattering Simulations
Authors: Arslan I , Browning N D
Published: July 2020

The promise of advanced technological applications in optical and electronic devices has led to a significant recent research effort in the structure-property relationships of defects in GaN. in particular, the major scientific issues arise from the high density of threading dislocations induced during thin film growth by film-substrate lattice mismatch. There is still debate as to the exact effect of these dislocations on the overall properties; they may or may not be electrically active and are thought to decrease the lifetime of devices. As such, a fundamental understanding of the electronic properties of these defects will facilitate the development of new and improved devices.

The analysis of the electronic structure of dislocations in GaN is performed here by a combination of atomic resolution electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) and multiple scattering (MS) simulations. Experimentally, a Z-contrast image of the dislocation core is obtained first1 and used to position the probe for EELS.
Effect of Shape on Solid-Liquid Phase Changes of Xe Precipitates in An Al Matrix
Authors: Mitsuishi K , Allen CW , Birtcher R C , Dahmen U
Published: July 2020

It is well known that rare-gas Xe atoms embedded in a crystalline Al matrix form precipitates having cuboctahedral shapes bounded by ﹛100﹜ and ﹛111﹜ surfaces1. Below a certain critical size, Xe precipitates are observed to be solid, even at room temperature. This is a result of the Laplace pressure, which is inversely proportional to the radius of the precipitate. Donnelly et al. reported that the critical size of Xe solidification was expected at 4nm in radius at room temperature.

Using high-resolution transmission electron microscopy, it is possible to observe these particles directly. It has been demonstrated that under off-Bragg conditions, the Al lattice fringes are minimized whereas the Xe lattice fringes are maximized. From such observations, it was confirmed experimentally that the average critical size of Xe precipitates is around 4 to 5nm in radius. However, much larger Xe precipitates are sometime observed to remain solid.
Pulse-Arc System for Investigation of Initial Fullerene Deposition
Authors: Murooka Y , Maede Y , Ozaki M , Hibino M
Published: July 2020

Since the discovery of fullerenes and carbon nanotubes, the deposits on arc electrodes produced at high gas pressure have been investigated intensely. Despite of the enthusiasm, little work was reported about the initial deposition processes. In principle, such processes could be followed by reducing the amount of products, i.e. a short discharge with a small current. In practice, however, this was prevented by two practical obstacles, arc instability and possible byproducts originated from reactions with remaining impurities in the vacuum chamber. In the present study, we reported a new kind of compact preparation system which allowed stable arc with a small current and a clean environment.

Figure 1 shows a schematic diagram of the system. For higher arc stability, the system had a small cylindrical shape which would reduce the effect of convection. Both electrodes were aligned on the axis inside the cylinder and their gap was adjustable by a micrometer.
Towards Property Nanomeasurments By In-Situ TEM
Authors: Wang ZL , Gao RP , Bai ZG , Dai ZR , Poncharal P , de Heer WA
Published: July 2020

Characterizing the physical properties of individual nanostructures is rather challenging because of the difficulty in manipulating the objects of sizes from nanometer to micrometer. Most of the nanomeasurements have been carried using STM and AFM. In this presentation, we demonstrate that transmission electron microscopy can be a powerful tool for quantitative measurements the mechanical, electrical and thermodynamic properties of a single nanostructure, such as a carbon nanotube or a nanoparticle.

Using a customer-built specimen holder, in-situ measurements on the mechanical properties of carbon nanotubes has been carried out using the resonance phenomenon induced by an externally applied alternating voltage [1]. If an oscillating voltage is applied on the nanotube with tunable frequency, resonance can be induced (Fig. 1). The bending modulus is calculated from the resonance frequency. The bending modulus is as high as 1.2 TPa (as strong as diamond) for nanotubes with diameters smaller than 8 nm, and it drops to as low as 0.2 TPa for those with diameters larger than 30 nm.
Spark Ignition Motor Vehicle Exhaust Particulate Matter Characterization
Authors: Blom Douglas A , Nolan Ted A
Published: July 2020

The Northern Front Range Air Quality Study concluded that for the Denver metropolitan area during 1996 and 1997, 55% of particles with an aerodynamic diameter 50% cutpoint of 2.5 μm (PM2.5) were attributable to motor vehicle exhaust particulates. The health effects of PM2.5 are currently unknown, but are under investigation. It is of vital interest to understand the chemistry, morphology, size distribution and microstructure of motor vehicle exhaust. The techniques of transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) appear to be well suited for the analysis of the microstructure, morphology and microchemical composition of particulate matter. Previous electron microscopy observations of particulate matter from a variety of sources have found that the chemical composition and crystal structure are characteristics of the source of the particles.

As part of an ongoing research project into the health effects of motor vehicle particulate matter, Southwest Research Institute (SWRI) is performing chassis dynamometer tests of a variety of vehicles and collecting samples from the exhaust stream for analysis.
Signaling by Calcium and the RHOA GTPASE: Relating Structure to Function
Authors: Somlyo AP , Somlyo AV
Published: July 2020

We will review the results of structural approaches used in our laboratory for evaluating the roles of calcium (Ca2+) and the small GTPase, RhoA, in normal and pathological cell signaling.

An early method, using strontium (Sr) as an electron opaque marker of mitochondrial Ca, was first used to localize this “Ca2+ surrogate” in the sarcoplasmic reticulum (SR) of smooth muscle. Subsequent development of electron probe X-ray microanalysis (EPMA) and electron energy-loss spectroscopy (EELS) allowed the direct and quantitative detection of intracellular Ca in smooth, skeletal and cardiac muscles. The major conclusion of these studies was that, in all muscles, the SR is the major intracellular sink/source of activator Ca2+. The high ratio of total/free cytoplasmic Ca2+ indicated the presence of significant cytoplasmic Ca buffers not only in striated, but also in smooth muscles, and EPMA of frog skeletal muscle showed that the time course of changes in cytoplasmic Ca during relaxation was consistent with the off-rate of Ca2+ from the Ca2+-buffer, parvalbumin.
Analysis of the Atomic Scale Oxygen Vacancy Ordering by EELS and Z-Contrast Imaging
Authors: Ito Y , Stemmer S , Klie RF , Browning ND , Mazanec TJ
Published: July 2020

Perovskite-type oxides with high electronic and ionic conductivity are very promising materials for use as dense ceramic membranes for oxygen separation. For the successful implementation of practical ceramic membranes, a full understanding of the parameters controlling the degree of non-stoichiometry, i.e. the defect chemistry is essential. A combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) can be used to directly image crystal and defect structures and the effect of the structures on the local electronic properties (i.e. oxygen coordination and cation valence). Here the defect chemistry in SrCoO3-δ before and after a reduction treatment at high temperatures is investigated in the JEOL 201 OF STEM. This material is known to exist in a wide a variety of phases with different crystal structures, compositions and valence states of cobalt, and can be highly oxygen deficient.
Development and Application of a New 300kv Omega-Filter Electron Microscope
Authors: Bando Y , Mitome M , Kitami Y , Kurashima K , Kaneyama T , Okura Y , Naruse M
Published: July 2020

It has been already pointed out that the medium voltage microscopes of 300kV to 400kV have some advantages in the analytical capabilities of EDS and EELS as compared to those of 200kV). The P/B ratios and the spatial resolution for the analysis will be improved with the increase of the accelerating voltages as well as lattice resolution. In order to improve the spatial resolution of inelastic filtered images, we have recently developed a new 300 kV omega-filter electron microscope with a field emission gun. In the paper, some characteristic features of the new microscope and its application results are described.

The new microscope have a 300kV field emission gun, an omega-filter, EDS, digital STEM, a slow-scan CCD, an imaging plate and TV camera. Some characteristic features of the new microscope are summarized in Table 1. Based on a calculation of probe diameter as a function of probe current at 300kV in a Shottkey type gun with a brightness of 7xl08A/cm2sr and Cs of 0.6mm, a minimum probe size (FWHM) is estimated to be about 0.2nm (Fig. 1).
Structural Analysis of gp6 and gp6/gpl5/gpl6 Complex by Cryo-Electron Microscopy At 10 Å Resolution
Authors: Orlova EV , Lurz R , Droege A , Gowen B , Tavares P , van Heel M
Published: July 2020

The mechanism of encapsidation of DNA into a bacteriophage head is a most intriguing problem. The portal protein is essential for the assembly of tailed double-stranded DNA (dsDNA) bacteriophages. These turbine-like homo-oligomers consist of 12 or 13 subunits surrounding a central channel. Portal oligomers are located at the vertex of the icosahedral head that binds to the phage tail. It was shown that gp6 portal protein from bacteriophage SPP1 has 13 subunits, prior to their incorporation into the viral procapsid structure. After packaging of the viral DNA inside the phage capsid, additional proteins have been found attached to the portal oligomer: gpl5 and gp 16. A complex of gp6/gpl5/gpl7 forms the connector structure that provides the interface for attachment of the phage tail. We here present the three-dimensional (3D) reconstructions of the gp6 wild-type protein alone and of the gp6/gpl5/gpl6 complex - both at 10Å resolution - based on electron cryo-microscopy using the angular reconstitution single particle methodology.
Single Particle Reconstruction of the Vault from TEP1 Knockout Mice and Refinement of the Computationally Selected Vault Barrel
Authors: Stewart PL , Kong LB , Siva AC , Kickhoefer VA , Harrington L , Rome LH
Published: July 2020

The vault complex is a ubiquitous and predominantly cytoplasmic 13 MDa ribonucleoprotein assembly, composed of three proteins (TEP1, 240 kDa; VPARP, 193 kDa; and MVP, 100 kDa) and an untranslated RNA (vRNA) Although the basic cellular function of the vault is still unclear, recently it has been shown that induction of the major vault protein (MVP) has a direct negative influence on the nuclear uptake of the anti-cancer drug, doxorubicin. We have been applying cryo-EM single particle reconstruction methods to study the structure and molecular architecture of this cellular component. A published reconstruction of the intact rat vault at 31 Å resolution revealed that the complex is hollow and is structurally well suited to serve in macromolecular transport or sequestration. Higher resolution, 23 Å, was achieved for a reconstruction of the RNase-treated rat vault and difference imaging with the intact rat vault localized the vRNA to the ends of the vault caps.
Single Particle Reconstruction of Human Fatty Acid Synthase
Authors: Brink J , Ludtke SJ , Yang C-Y , Gu Z-W , Wakil S , Chiu W
Published: July 2020

Fatty acid synthase (FAS) is the enzyme responsible for de novo synthesis of fatty acids from acetyl-CoA, malonyl-CoA and NADPH. FAS (550 kDa) is a homodimer of two multifunctional polypeptides, each with seven distinct catalytic activities and a site for the prosthetic group, 4’- phosphopantetheine, acyl carrier protein (ACP). These domains are organized from the N- to the C-terminus as follows: keto acylsynthase, acetyl/malonyl transacetylase, dehydratase, the interdomain, enoyl reductase, ketoreductase, ACP and thioesterase. The two polypeptides are held together through the interdomain and oriented in an anti-parallel manner, each contributing complementary half sites and giving rise to two independently active centers for palmitate synthesis. Interest in FAS arises from its involvement in human disorders, such as obesity, hyperlipidemia and carcinogenesis.

Human FAS purified from a breast cancer cell line, ZR75-1, was vitrified at 50-70 μg/ml on holey grids in the presence of NADPH and acetyl-CoA and kept at -166°C in a Gatan 626 cryo-holder.
Comparison of Particle Size Analyses from FEG-SEM and TEM Images
Authors: Lanteri S , Gendt D , Barges P , Petitgand G
Published: July 2020

Much effort has recently been employed in modeling steel behavior as a function of chemical composition and thermo-mechanical processing. In order for the models to be predictive, experimental data are needed to first calibrate and then validate the calculated results. Since many steel properties are conditioned in part by the state of precipitation, this study was undertaken to provide experimental measurements of precipitates in terms of their size distributions. Due to the size range (2-100 nm) of particles which exert the greatest influence on the mechanical properties, electron microscopy is practically the only technique available for obtaining images of the precipitates.

Two types of micrographs were used for image analysis in order to determine the size distribution of NbC particles present in a ternary alloy (Fe-Nb-C) heat treated at 800°C for 1000 mn. Polished surfaces lightly etched with a solution of 2% HNO3 and 98% ethanol were prepared for observations in a LEO 1550 scanning electron microscope equipped with a field emission gun.
Evaluation of Cardiomyocyte Viability after Cardiac Tissue Incubated in Special Culture System
Authors: Wei C , Papadimitriou J
Published: July 2020

Cardiac myocytes maintained in cell culture develop hypertrophy both in response to mechanical loading as well as to receptor-mediated signaling mechanisms. However, it has been shown that the hypertrophic response to these stimuli may be modulated through effects of intercellular contact achieved by maintaining cells at different plating densities. We recently developed the new special tissue culture system to culture minced cardiac tissue and to evaluate the apoptotic effect of different agent in cardiomyocytes. After 24 hours culture period, different culture conditions and factors may damage the cardiomyocyte. Therefore, we performed different methods to evaluate the viability of cardiomyocyte in cardiac tissue with 24 hours culture period in our special culture system.

Human cardiac atrial tissue was obtained from open-heart surgery (n=6). After cardiac tissue excision, the samples were immediately placed in oxygenated, nominally Ca2+-free Tyrode solution for transport to the laboratory. The time between excision and the beginning of laboratory processing was five to fifteen minutes.
The Action of C-Type Natriuretic Peptide on Apoptosis and P53 Expression in Human Cardiomyocytes
Authors: Seta K , Matsuda Y , Wei C
Published: July 2020

C-type natriuretic peptide (CNP) is endothelial cell origin and has potent vasodilatory and antimitogenic actions. We reported that CNP was markedly increased in human cardiac tissue with severe congestive heart failure. To date, the effects of CNP on cardiomyocyte growth and death remain unclear. Therefore, the present study was designed to investigate the actions of CNP on apoptosis and apoptosis-related gene p53 expression in human cardiomyocytes.

Human cardiac atrial tissue was obtained from open-heart surgery (n=6). The cardiac tissue was minced and incubated in the special tissue culture system in the absence or presence of CNP (10-7 M) for 24 hours. These studies were repeated with HS-142-1 (HS, 10-6 M), a natriuretic peptide biological receptor antagonist. To detect the DNA fragmentation, in situ terminal deoxymucleotidyl transferase dUTP nick end labeling (TUNEL) was performed. The p53 expression was determined by immunohistochemical staining (IHCS). An average of 1000 nuclei was analyzed for TUNEL and p53 staining studies.
Use of the Vital Stain FM4-64 for Visualizing Membrane Dynamics in Living Fungal Cells
Authors: Roberson RW , Fisher KE , Lowry DS
Published: July 2020

Allomyces macrogynus is a zoosporic fungus (Chytridiomycota) that exhibits a true alternation of generations between the diploid and haploid thalli. During the diploid stage in the life cycle, sporothalli are produced which are capable of forming asexual zoosporangia containing a multinucleate protoplast bound by a single plasma membrane and cell wall. Though able to remain in a quiescent, coenocytic state for an extended period of time, under certain environmental conditions the cytoplasm of mature zoosporangia is cleaved and gives rise to numerous uninucleate, uniflagellate zoospores within 40 to 50 min. Previous studies of cleavage membrane development m Allomyces zoosporangia have been conducted using light microscopy and transmission electron microscopy (TEM). Despite these investigations, our understanding of cytokinesis in zoosporangia of Allomyces and other zoosporic organisms remains incomplete. This is due, in part, to the difficulty of detecting cleavage elements using standard light microscope optics (i.e., phase contrast, differential interference contrast) and because ultrastructural analysis often provides limited temporal and spatial detail and may suffer from artifacts of sample preparation.
Automated Analysis of Data Mark Microstructure of Optical Discs
Authors: Chernoff D A , Cook C S , Burkhead D L
Published: July 2020

Introduction. By volume of material produced, optical disc manufacturing is the world's large nanotechnology industry, far surpassing semiconductors and magnetic disks. The development of various optical disc media has introduced a variety of challenges, which necessitate viewing the geometrical structure of the bumps, pits, or grooves on the surface of the discs. The Atomic Force Microscope (AFM) has the resolution and sensitivity needed for device analysis, but in the past has been limited by magnification errors, image distortion, data handling, and calibration. Furthermore, the common measurement procedure for AFM images consists of manual dimensional measurements. This introduces error and limits the number of measurements taken at one time. We have developed an automated process, which overcomes these limitations and provides a comprehensive approach to feature measurement, data analysis, calibration, and reporting.
LVSEM Surface Sampling, Preparation, Peak Overlap, Convergent Analysis and Covering up the FESTEM Aperture Charging Problem
Authors: Boyes E D
Published: July 2020

Surfaces The majority of the SEM secondary electron signal (SE) comes from the first few (<2nm) nanometers of the surface. The quality of the outermost few atomic layers of an exposed and reactive sample can therefore have a profound effect on image contrast. With light elements and low voltages the SE signal is dominated by scattering at the point of incidence of the primary probe, but more generally there is a significant contribution to surface SE generation by primary electrons backscattered from deeper in the sample. With the advent of very low voltage EDS, and the application of more conventional surface science methods, we learn that even without a coating the surface of a sample may be atypical of the bulk (Fig. 1). Contamination of an otherwise clean surface occurs by transport of the sample through the air, leading to oxidation, hydrocarbon accumulation, and occasionally to rather more dramatic pyrophoric effects.
Contact Angle Measurement in the Environmental Scanning Electron Microscope (ESEM)
Authors: Craven JP , Stelmashenko NA , Terentjev EM , Thiel B L
Published: July 2020

The ESEM uses a novel differential pumping system combined with a pressure-limiting aperture to achieve relatively high pressures of up to 10 torr in the specimen chamber. Using this system allows samples to be imaged in the presence of water vapour or other gases. Conveniently the saturated water pressure at 275K lies within this range, allowing the stabilisation of hydrated samples, condensation from water vapour and evaporation to be performed in situ within the microscope chamber.

Wetting of surfaces is of fundamental importance in many different areas of science, from textiles to petroleum engineering. The ESEM now provides an opening for high-resolution studies of these phenomena without the problematic depth-of-field limitations that optical methods present. The contact angle, θ, is defined as the angle between the tangent to the liquid-fluid interface and the tangent to the solid interface. It provides a ready indication to the wetting properties of a system.