bluuebunny/crossref_metadata_2025 huggingface dataset:
The Impact of Imaging Technologies in Materials Engineering
Authors: Gronsky R.
Published: June 2020

Materials Engineering is widely acknowledged as a “hyper-discipline” spanning the fundamental sciences (Physics, Chemistry and Biology) with all of the traditional engineering pursuits (Civil, Electrical, Mechanical, Metallurgical, Nuclear…). A healthy materials engineering program in fapt demands interaction among basic science and technology, all classes of materials, and the intrinsic elements of the field, parochially known as properties, performance, structure (including composition) and synthesis (including processing). Advanced characterization techniques are obviously critical to this integration, and new imaging technologies have accelerated the process of characterizing materials at all relevant length scales, communicating large data sets to practicing engineers, and refining manufacturing methods with image-based technologies. The importance of imaging technologies was forecast by the National Research Council in a highly regarded 1989 report “Material Science & Engineering for the 1990’s: Maintaining Competitiveness in the Age of Materials,” which included prominent mention of all microscopy methods. Since then, the success and challenges associated with imaging technologies have increased dramatically.

In the biomaterials field, which is projected to be a $5 billion dollar industry before the year 2000, imaging technologies are most evident. Cross-modal medical imaging (MRI, CAT..) localizes the results of disease or trauma that might be remedied by implantable structures, developed under condition of strict microstructural control, and monitored for degradation products by non-invasive in-situ means. Products include biochemical sensors requiring high spatial resolution characterization of structure and composition, orthopedic prostheses and repairs, sometimes processed to possess pore structures that mimic natural bone, and wound-management devices, including artificial skin composed of bi-layer silicone elastomers and glycosaminoglycan interspersed with collagen. The last of these is especially dependent upon microstructural characterization. Implantable materials systems, such as the cochlear implant for hearing restoration (direct stimulation of the auditory nerve), or heart-assist devices (long fatigue life), require some of the highest standards in materials selection, design, and integration, with the added dimension of biocompatibility. In addition, the irradiation sensitivity of many candidate biomaterials requires strict attention to low-dose imaging methods, rapid scan image acquisition, and sometimes extensive image processing to avoid or circumvent artefacts. Forward-looking projects on fully implantable therapeutic “agents” for medicinal delivery or chelation of toxins and viruses will place even more demands upon our ability to image in-situ functionality.
In Situ Localization of PPAR Gamma and Uncoupling Protein in Mouse Embryo Sections Using Digoxigenin-Labeled Riboprobes
Authors: Jennermann C. , Kliewer S. A. , Morris D. C.
Published: June 2020

Peroxisome proliferator-activated receptor gamma (PPARg) is a member of the nuclear hormone receptor superfamily and has been shown in vitro to regulate genes involved in lipid metabolism and adipocyte differentiation. By Northern analysis, we and other researchers have shown that expression of this receptor predominates in adipose tissue in adult mice, and appears first in whole-embryo mRNA at 13.5 days postconception. In situ hybridization was used to find out in which developing tissues PPARg is specifically expressed.

Digoxigenin-labeled riboprobes were generated using the Genius™ 4 RNA Labeling Kit from Boehringer Mannheim. Full length PPAR gamma, obtained by PCR from mouse liver cDNA, was inserted into pBluescript SK and used as template for the transcription reaction. Probes of average size 200 base pairs were made by partial alkaline hydrolysis of the full length transcripts. The in situ hybridization assays were performed as described previously with some modifications. Frozen sections (10 μm thick) of day 18 mouse embryos were cut, fixed with 4% paraformaldehyde and acetylated with 0.25% acetic anhydride in 1.0M triethanolamine buffer. The sections were incubated for 2 hours at room temperature in pre-hybridization buffer, and were then hybridized with a probe concentration of 200μg per ml at 70° C, overnight in a humidified chamber. Following stringent washes in SSC buffers, the immunological detection steps were performed at room temperature. The alkaline phosphatase labeled, anti-digoxigenin antibody and detection buffers were purchased from Boehringer Mannheim. The sections were treated with a blocking buffer for one hour and incubated with antibody solution at a 1:5000 dilution for 2 hours, both at room temperature. Colored precipitate was formed by exposure to the alkaline phosphatase substrate nitrobluetetrazoliumchloride/ bromo-chloroindlylphosphate.
Can Microwave Ovens Reduce Immunocytochemical Labeling Times?
Authors: Iadarola Linda , Webster Paul
Published: June 2020

In recent years the use of microwave ovens in biomedical microscopy laboratories has contributed to reducing the times of fixation and resin embedding. Reports of the use of microwaves for histochemsitry and immunocytochemistry led us to investigate the possible use of a microwave oven to reduce immunocytochemical labeling protocols.

The application of specific antibodies to thawed cryosections of aldehyde-fixed material is becoming more accessible to research and service laboratories. These detection methods, routinely performed in our laboratory, were used to study the effect of microwaves on labeling protocols using affinity purified, polyclonal antibodies and protein A-gold.

Cells containing 3-(2,4-dinitroanilino)-3-arnino-N-methyldipropylamine (DAMP), a compound which accumulates in low pH compartments, were aldehyde-fixed, cryosectioned and then labeled with rabbit antibodies to dinitrophenol (which bind to DAMP) and 10nm protein-A gold. Regular sequential labeling protocols were compared with protocols using a microwave oven operating at 100% power, where the antibody incubation and washing times were reduced. The effect of microwaves on the labeling efficiency was investigated using simple quantitative methods. The protocol which produced reduced incubation times with no loss of labeling efficiency was then applied to sections in the absence of microwaves. The effect of reducing the final methyl cellulose-uranyl acetate contrasting step was also investigated.
Subcellular Localozation of TFPI in Human Umbilical Vein Endothelial Cells (HUVEC)
Authors: Olsen Randi , Webster Paul , Hansen John Bjarne
Published: June 2020

Tissue factor pathway inhibitor (TFPI) is a serine protease inhibitor which regulates tissue factor (TF) induced blood coagulation by inhibiting the action of factor VIIa-TF complexes and factor Xa. In plasma, more than 80 % of the TFPI is bound to lipoproteins, 10 -20 % is carrier free, whereas platelets contains a small amount of TFPI. A major pool is probably assosiated with the vascular endothelium (1). This pool may have a crucial regulatory function because the endothelial surface serves as a binding site for factor VII/VIIa, mediating the activation of the extrinsic coagulation system.

The normal distribution of TFPI within human umbilical vein endothelial cells (HUVEC) was examined on ultrathin cryosections labeled with specific antibodies and colloidal gold probes (2,3). Label was seen associated with the cell surface and with many intracellular structures. The surface label was patchy, the signal intensity varied between cells and between different parts of the same cell. Intracellular TFPI was found in many compartments including the Golgi complex (fig.l) a finding that was expected as these cells are the main site of TFPI synthesis, and endocytic organelles. Anti TFPI-antibodies were seen over organelles that also contained 3-(2,4-Dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP), a compound that accumulates in organelles with low lumenal pH. DAMP was visualized using anti-DNP antibodies (fig.2). Structures that contained exclusively TFPI or DAMP were also seen, suggesting that TFPI did not enter all endocytic organelles and was not exclusively localized to low pH compartments. The TFPI-antibodies also colocalized with specific markers of endosomes (MPR) (fig.3) and lysosomes (LAMP-1) (fig.4)(4). TFPI colocalized with both, demonstrating the appearence of TFPI also in these endocytic compartments.
Three-dimensional imaging of nucleosomes from transcriptionally active genes using electron spectroscopic imaging
Authors: Czarnota G. J. , Bazett-Jones D. P. , Ottensmeyer F. P.
Published: June 2020

The three-dimensional structure of the nucleosome was determined using particles purified from transcriptionally active genes in conjunction with electron spectroscopic imaging, and quaternion-assisted angular reconstitution procedures. The results reveal a configuration which is very different from the canonical compact crystallographic structure for this fundamental chromosome subunit, implying a structural disruption of the nucleosome with the activation of gene expression in accord with numerous physico-chemical observations.

Previous analyses of nucleosomes purified from transcriptionally quiescent genes have indicated numerous structural states dependent on factors in vitro which modify charge based interactions in nucleoprotein complexes. Nucleosomes from transcriptionally active genes undergo chemical alterations in vivo which similarly modify charge based interactions. In order to investigate the effects of the gene expression associated chemical alterations on nucleosome structure, particles were purified from transcriptionally active genes using mercury affinity chromatography. These nucleosome particles are hyperacetylated with respect to particles from transcriptionally quiescent genes. Here additionally, sulphydryls normally buried within the protein core of the transcriptionally inactive particle are exposed to chemical modifying agents thus facilitating purification as described.
High resolution rotary shadowing of herpes simplex virus helicase proteins
Authors: Moretz R. C. , Crute James J.
Published: June 2020

Herpes viruses cause numerous human diseases. Herpes Simplex viruses (HSV1 and HSV2), varicella zoster virus (VSV),cytomegalovirus (CMV), and Epstein-Barr Virus (EBV) cause conditions ranging from peripheral sores (HSV, VSV), generalized viremia (CMV) and recurrent malaise (EBV). The common targets for HSV are neurons in the CNS, peripheral nerve cells or plexuses of sensory ganglia in highly innervated epithelium (e.g. lips, genitals).

Interfering with the mechanisms of infection and virus production depends on the ability to target specific stages of viral reproduction. Helicases are enzymes that are essential for the duplication of viral DNA. The origin binding protein (OBP) helicase (encoded by the DNA replication gene UL9) binds to sequences in DNA at the three replication origins. These origins are points within the HSV chromosome where DNA replication initiates. The protein is a 83kDa polypeptide which exists as a dimer. Although the role of the UL9 helicase in HSV DNA replication has not been exactly determined, by analogy to other eukaryotic origin binding replication proteins, the binding and enzymatic action of the UL9 helicase to the origin sequences may initiate the assembly of a multiprotein replication complex. Helicase-primase (the product of the DNA replication genes UL5. UL8 and UL52) acts to unwind double-stranded DNA at growing replication forks. The helicaseprimase activity is expressed by a 213kDa heterodimer consisting of the 99kDa UL5 and 114kDA UL52 subunits. ICP8 (SSB—UL29 gene product) is a single-stranded binding protein of 122kDa that complexes with OBP (two SSB/OBP dimer). Each of these gene products has been expressed in insect cells with a recombinant baculovirus and purified to near homogeneity. Assays have been established for the screening of compounds that could inhibit the helicase activity of HSV 1 helicases. Analysis of helicase/DNA substrate complexes under different conditions will be facilitated by a better understanding of the structure of the individual proteins.
Visualization of co-axially coiled dsDNA in bacteriophage T7 capsids by cryo-electron microscopy
Authors: Cheng Naiqian , Cerritelli Mario E. , Rosenberg Alan H. , Booy Frank P. , Steven Alasdair C.
Published: June 2020

The packaging of viral DNA into a pre-formed procapsid structure and its subsequent release from the mature virion during infection, constitutes one of the basic phenomena of the viral life-cycle which still remains to be understood. The DNA must package at a high density into the head to allow efficient utilization of the space available, overcome the mutual electrostatic repulsive forces between the strands, and be readily available for release upon infection. Cryo-electron microscopy has proven to be an invaluable tool for visualizing the internal organization of the packaged DNA inside viral capsids. We report on the effectiveness of this technique in examining the packaging of the ∼40,000 bp double-stranded DNA genome inside the capsids of bacteriophage T7.
Location of subunits in the acetylcholine receptor by analysis of electron images of tubular crystals fromTorpedo marmorata
Authors: Burkwall David A. , Josephs Robert , Holly Jennifer , Richman David , Fairclough Robert
Published: June 2020

The nicotinic acetylcholine receptor(AChR) is a membrane protein containing four different homologous polypeptide chains (two copies of an α-subunit and single copies of β, γ, and δ). These subunits assemble about a central cavity, which is thought to delineate the ion-selective channel. In tubular crystals fromT. marmoratareceptors normally exist as dimers, paired through disulphide bonds between the δ-subunits. Conflicting reports still arise concerning the relative locations of these subunits around the central axis. It has been proposed that the β-subunit lies between the two α-subunits or that the γ subunit lies between the two α-subunits. Here we examine the locus of two subunit-specific labels, mAb 383C and 247G, bound to receptors and averaged in each case from over 5,000 molecules.
A comparison between one non-invasive and three invasive procedures used in the preparation of plant material for X-Ray microanalysis
Authors: Echlin Patrick
Published: June 2020

It is generally accepted that accurate quantitative elemental x-ray microanalysis of bio-organic material depends critically on the way the sample is treated before it is analysed. It is axiomatic that preparative procedures which change the local permeability of samples are going to be less useful than procedures which do not affect this critical property of cells and tissues, particularly if highly diffusible electolytes are the focus of any investigation. Thus we generally eschew ambient temperature methods in favour of low temperature techniques which either slow down or halt diffusion processes. As part of a larger study on the distribution and local concentration of aluminium in the developing leaves of tea plants, which under some circumstances can be as high 30,000ppm, a comparative study has been carried out to assess the effectiveness of four preparative techniques in retaining this element in the cell walls and vacuoles of older tea leaves which are know to contain more aluminium than younger leaves.
Quantification of order in the liquid at a solid-liquid interface by high-resolution transmission electron microscopy (HRTEM)
Authors: Howe J. M.
Published: June 2020

A number of different theoretical approaches have been used to model the atomic structure and properties of solid-liquid interfaces. Most calculations indicate that ordering occurs in the first several layers of the liquid, adjacent to the crystal surface. In contrast to the numerous theoretical investigations, there have been no direct experimental observations of the atomic structure of a solid-liquid interface for comparison. Saka et al. examined solid-liquid interfaces in In and In-Sb at lattice-fringe resolution in the TEM, but their data do not reveal information about the atomic structure of the liquid phase. The purpose of this study is to determine the atomic structure of a solid-liquid interface using a highly viscous supercooled liquid, i.e., a crystal-amorphous interface.
HRTEM investigation of the interface between AIN and SiC
Authors: O’Keefe M.A. , Ponce F.A. , Nelson E.C.
Published: June 2020

Epitaxial thin films of the group III nitrides play an increasingly important role in the fabrication of high-efficiency light emitting diodes in the range between yellow and blue. Growth of such films on sapphire requires the use of low temperature buffer layers of AIN or GaN. Silicon carbide has a much closer lattice parameter match than sapphire to AIN, and promises to produce better AIN layers. Since the atomic arrangement at the interface between AIN and SiC determines the degree of perfection of the epitaxial layer, we have attempted to determine the structure of this interface by hign-resolution transmission electron microscopy. Devices were grown by MOCVD; AIN was deposited on the Si-face of α-6H SiC, followed by GaN. The specimen was cut for HRTEM observation in the SiC projection, mechanically thinned to 20μm and ion-milled to electron transparency. Observations were made using the NCEM JEOL ARM-1000 operated at 800keV. Images were obtained at a specimen thickness of 85A (determined by extrapolation to the first extinction distance of the wedge). The most-useful defocus was −1050Å at which the important spacings from both SiC and AIN are passed with the same phase (fig.1).
Computer simulation of transmission electron micrographs by microscope for windows
Authors: Kuokkala V.-T.
Published: June 2020

microScope for Windows™ is a transmission electron micrograph simulation program for brightfield and darkfield images of dislocations and stacking faults, based on the dynamical two-beam theory and the column approximation. The program is a modification of the original programs of Head et al, which have been rewritten in Visual Basic™ 4.0 for Microsoft® Windows™ 3.1. microScope for Windows™ also includes routines needed to prepare data for the actual calculation of the image, and to calculate and display a rocking curve for any pixel of the previously computed brightfield or darkfield image. On a 120 MHz Pentium, microScope for Windows™ calculates a true gray scale (256 gray level) image consisting of 19840 pixels in about 10 seconds (version 2.3). A 300 dpi laserprinter screendump at the end of the calculation of an image is shown in Fig. 1.
Calculation of many-beam dynamic electron diffraction without high-energy approximation
Authors: Ahn B. R. , Kim N. J.
Published: June 2020

High energy approximation in dynamic theory of electron diffraction involves some intrinsic problems. First, the loss of theoretical strictness makes it difficult to comprehend the phenomena of electron diffraction. Secondly, it is difficult to believe that the approximation is reasonable especially in the following cases: 1) when accelerating voltage is not sufficiently high, 2) when the specimen is thick, 3) when the angle between the surface normal of the specimen and zone axis is large, and 4) when diffracted beam with large diffraction angle is included in the calculation. However, until now the method to calculate the many beam dynamic electron diffraction without the high energy approximation has not been proposed. For this reason, the authors propose a method to eliminate the high energy approximation in the calculation of many beam dynamic electron diffraction. In this method, a perfect crystal with flat surface was assumed. The method was applied to the calculation of [111] zone axis CBED patterns of Si.
Application of Low-Voltage Field-Emission SEM to the Study of Internal Pore Structures of Activated Carbon
Authors: Liu J. , Ornberg R. L.
Published: June 2020

Activated carbon has interesting and useful properties for industrial applications. It has been used extensively in purification, separation, chemical recovery and catalysis. To achieve a predictable performance of activated carbon materials, it is necessary to develop a comprehensive understanding of the pore structure including pore size, pore shape, and pore surface chemistry. Macropores (> 50 nm), mesopores (2-50 nm) and micropores (< 2 nm) generally coexist in activated carbon. It is thus desirable to synthesize activated carbon with controlled pore structures to optimize its performance. We previously reported the characterization of thesurface pore structureof activated carbon by field emission SEM (FESEM) and the examination of theinternal pore structureby HAADF/HRTEM techniques.1However, both HAADF and HRTEM techniques give only limited information about the carbon pore structure. We report here some preliminary observation of the internal pore structure of activated carbon by high resolution low voltage FESEM technique.
SEM image sharpness analysis
Authors: Postek M. T. , Vladar A. E.
Published: June 2020

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.

In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.
How to get the most of a SEM using the CASINO monte carlo program
Authors: Drouin D. , Hovington P. , Gauvin R. , Beauvais J.
Published: June 2020

High resolution scanning electron microscopy (SEM) has become more and more popular for several reason. First, the new field emission (FE) source of electron is now able to produce a high current density electron probe even at very low energies. It is possible to perform analysis with spatial resolution comparable to one obtain in conventional transmission electron microscope (TEM). The major inconvenient of TEM analysis are related to sample preparation. Fabrication of electron transparency film is generally a complex and time consuming process.

To fully exploit a SEM, microscope users must have an accurate knowledge of the electron matter interaction. In order to help microscope users determine the appropriate microscope conditions, Monte Carlo simulation programs have been developed. Those programs, use random number sequences and complex models to accurately determine the signals recorded in a SEM (X-Ray and Backscattered electron). With the new generation of powerful personal computers, it is now possible to rapidly predict SEM outputs corresponding to the user’s microscope conditions. The CASINO program is a shareware that can be used to fully exploit a SEM.
Investigation of low-loss spectra and near-edge fine structure of polymers by peels
Authors: Heckmann W.
Published: June 2020

Transmission electron microscopy has changed from a purely imaging method to an analytical method. This has been facilitated particularly by equipping electron microscopes with energy filters and with parallel electron energy loss spectrometers (PEELS). Because of their relatively high energy resolution (1 to 2 eV) they provide information not only on the elements present but also on the type of bonds between the molecular groups. Polymers are radiation sensitive and the molecular bonds change as the spectrum is being recorded. This can be observed with PEEL spectrometers that are able to record spectra with high sensitivity and in rapid succession.

A PEEL spectrum can be divided into a low loss range and an inner shell loss range of higher energy. The low loss spectra of polymers always show a broad peak at about 22 eV and a further peak at 7 eV, if aromatic groups are present, as is the case with PS (Fig. 1). In the course of exposure, the intensity of this peak decreases, a sign that the benzene ring is destroyed by the radiation (Fig. 2).
Extraction and identification of fillers and pigments from pyrolyzed rubber and tire samples
Authors: Sadhukhan P. , Zimmerman J. B.
Published: June 2020

Rubber stocks, specially tires, are composed of natural rubber and synthetic polymers and also of several compounding ingredients, such as carbon black, silica, zinc oxide etc. These are generally mixed and vulcanized with additional curing agents, mainly organic in nature, to achieve certain “designing properties” including wear, traction, rolling resistance and handling of tires. Considerable importance is, therefore, attached both by the manufacturers and their competitors to be able to extract, identify and characterize various types of fillers and pigments. Several analytical procedures have been in use to extract, preferentially, these fillers and pigments and subsequently identify and characterize them under a transmission electron microscope.

Rubber stocks and tire sections are subjected to heat under nitrogen atmosphere to 550°C for one hour and then cooled under nitrogen to remove polymers, leaving behind carbon black, silica and zinc oxide and 650°C to eliminate carbon blacks, leaving only silica and zinc oxide.
Postmortem and in situ TEM methods to study the mechanism of failure in controlled-morphology high-impact polystrene resin
Authors: Cieslinski R. C. , Dineen M. T. , Hahnfeld J. L.
Published: June 2020

Advanced Styrenic resins are being developed throughout the industry to bridge the properties gap between traditional HIPS (High Impact Polystyrene) and ABS (Acrylonitrile-Butadiene-Styrene copolymers) resins. These new resins have an unprecedented balance of high gloss and high impact energies. Dow Chemical's contribution to this area is based on a unique combination of rubber morphologies including labyrinth, onion skin, and core-shell rubber particles. This new resin, referred as a controlled morphology resin (CMR), was investigated to determine the toughening mechanism of this unique rubber morphology. This poster will summarize the initial studies of these resins using the double-notch four-point bend test of Su and Yee, tensile stage electron microscopy, and Poisson Ratio analysis of the fracture mechanism.
A shear stabilized biaxial texture in a lamellar block copolymer
Authors: Polis D. L. , Pinheiro B. S. , Lakis R. E. , Winey K.I.
Published: June 2020

Block copolymers spontaneously self-assemble into a variety of morphologies. Recent studies have produced a biaxial texture in poly(styrene-b-ethylene propylene), SEP, diblock copolymers by applying oscillatory shear. This biaxial texture consists of “parallel” lamellae (normal to lamellae aligned perpendicular to shearing surfaces) and “transverse” lamellae (normal to lamellae aligned parallel to shearing direction) according to small-angle X-ray scattering, SAXS. The present study has determined how these two populations of lamellae are arranged and how they relax upon quiescent annealing by examining the superstructure via FE-SEM.

Sample preparation for the JEOL 6300 FE-SEM was designed to preserve a sample's orientation with respect to the shearing direction and provide a large viewing area (.1 - .3 mm2) relative to what is typical with cryo-ultramicrotomed sections for TEM. Bulk samples were cut and mounted on a specimen stub with one of the 3 orthogonal directions of the shearing geometry oriented perpendicular to the stub surface.
TEM study of a biofilm on copper corrosion
Authors: Chiou W. A. , Kohyama N. , Little B. , Wagner P. , Meshii M.
Published: June 2020

The corrosion of copper and copper alloys in a marine environment is of great concern because of their widespread use in heat exchangers and steam condensers in which natural seawater is the coolant. It has become increasingly evident that microorganisms play an important role in the corrosion of a number of metals and alloys under a variety of environments. For the past 15 years the use of SEM has proven to be useful in studying biofilms and spatial relationships between bacteria and localized corrosion of metals. Little information, however, has been obtained using TEM capitalizing on its higher spacial resolution and the transmission observation of interfaces. The research presented herein is the first step of this new approach in studying the corrosion with biological influence in pure copper.

Commercially produced copper (Cu, 99%) foils of approximately 120 μm thick exposed to a copper-tolerant marine bacterium, Oceanospirillum, and an abiotic culture medium were subsampled (1 cm × 1 cm) for this study along with unexposed control samples.
Fracture investigation of Fe-Zn alloy coating on steel sheets after deformation
Authors: Lin Yuli , Hou Wen-Shen
Published: June 2020

Steel coating technology has made great progress in recent years to meet the demand for corrosion-resistant steel. Fe-Zn coated steel sheet is one of those which has been developed with increasing production in response to the brisk demand in the automobile, construction and household electrical appliance industries

The adhesion of coating to substrate is a critical property of any coating system for mechanical integrity and environmental protection of the substrate. The investigation of fracture on the coating layer and/or on any interfaces after deformation, specially the initiation of failure provides fundamental acknowledge to understand major factors contributing to the adhesion of coatings. This paper presents the results of fracture on Fe-Zn alloy coatings on steel sheets after deformation.
Stabilizing the nanostructure in ball-milled iron alloys through the addition of oxide precipitates
Authors: Doğan C.P. , Rawers J.C.
Published: June 2020

High-energy ball milling has proved to be an effective means of producing nanostructured metal alloys from elemental powders. Interest has focussed on this processing method because of its potential to form metastable compositions with a combination of properties not attainable by more conventional processing techniques. Consolidation of the resulting powders into commercially-viable solids has proven difficult, however. Because of the metastable nature of the compositions formed and the extremely high boundary area that makes up the nanostructure, these materials are very susceptible to exposure to elevated temperatures. Since most conventional consolidation techniques involve high temperatures, the nanostructure within the powders is typically lost during this processing step. Thus, a reliable means of enhancing the thermal stability of these materials, allowing economical consolidation, is clearly needed.

One possible method to enhance thermal stability is to introduce a homogeneous distribution of stable second phase particles that will pin the grain boundaries, allowing retention of the nanostructure at temperatures high enough for effective consolidation.
Microanalysis of Ferroelectric Memories Using Micro X-Ray Diffraction
Authors: Eatough M. O. , Rodriguez M. A. , Dimos D. , Tuttle B.
Published: June 2020

Since the advent of the microdiffractometer a new world of analysis possibilities have opened. In this paper we will discuss a novel use of microdifraction. We have developed a method for monitoring domain switching in ferroelectric thin films in situ using micro x-ray diffraction (μXRD). μXRD is a nontraditional x-ray diffraction technique which has recently attracted much attention [3]. The microdiffractometer is capable of obtaining a diffraction pattern from 0 – 150° 20 simultaneously from regions as small as 30μm in diameter. The purpose of this study was to determine if ferroelectric switching of ferroelectric Pb(Zr, Ti)O3 (PZT) thin films can be observed using μXRD. This method will be extremely valuable as we target the necessary processing parameters to achieve the desired switching behaviors and to monitor switching in micron-sized devices.
Imaging focused x-rays from glass capillaries
Authors: Steel Eric B. , Jach Terrence
Published: June 2020

Recent developments of glass capillaries allow x-ray probes to be focused down to micrometer sizes. These probes show promise for microanalysis applications, if they can reliably deliver high intensity, well formed x-ray beams to a specimen. We have developed an optical bench for viewing and evaluating the focused x-rays emitted from these capillaries. The optical bench allows pulse counting, direct viewing of the x-ray probe spatial distributions, and energy pass band by using exchangeable detectors. Our results are used to determine the probe forming capabilities of the lenses and to indicate problems and directions for improving the manufacturing of the x-ray optics.

The x-ray optical bench is shown in a schematic diagram in figure A. It consists of a conventional CuKα x-ray diffraction tube joined to an optical table. An optical rail extends across them. A shielded box with a hinged side covers the source and the optical rail. The x-ray optic and exchangeable detector system are located on computer controlled stages to allow fine adjustments in all necessary translation and tilt directions. This optical bench permits measurements to be devised, performed, and changed with a minimum of difficulty. The optical bench allows for maximum flexibility in sample positioning, detector positioning, source size, and source collimation. The quantities that we evaluate in each optical element include focal spot size, spot uniformity, total spot flux, spot aberrations, diffuse scattered radiation, and depth of field or convergence.
Synchrotron infrared microspectroscopy challenges difficult analytical problems
Authors: Wetzel David L. , Reffner John A. , Williams Gwyn P.
Published: June 2020

Micro spectroscopy of molecular species in situ takes advantage of biological concentration by nature of certain molecules within the bulk specimen. Localized hetergeniety is readily documented. Order or randomness may be established for substances that are present in a quantities below the detection limit in the bulk but that may be present in a measurable amount when acute probing is done in the correct region of the specimen. Spectral resolution with a microbeam directed at a relatively small spot from which spectroscopic data is obtained makes this task readily possible. Spectral resolution is achieved with optical efficiency of modern infrared micro spectrometers in which signal is conserved and noise minimized. Improvement of S/N is routinely done by coadding multiple scans however reducing the aperture by half reduces the signal by at least four and doubling S/N requires taking data for four times as long. Thus even if a diffraction limiting situation does not arise one of these desirable goals of 1) good spectral separation (small aperture size), 2) high S/N (good low-noise spectra) and 3) short time of data accumulation must be compromised. This is true with even the most optically efficient instrument however substituting infrared radiation from the vacuum UV storage ring of the National Synchrotron Light Source (Brookhaven National Laboratory) for the conventional thermal (glowbar) instrument source makes it possible to achieve all three goals without the necessity of a severe compromise on at least one of them. The synchrotron beam is 2-3 orders of magnitude brighter, has no thermal noise, and has very low divergence. Aperturing the small concentrated beam results in a relatively small percentage loss in beam intensity.
Imaging Deep Optical Sections with Two-Photon Excitation Fluorescence Microscopy
Authors: White J.G. , Centonze V.F. , Wokosin D.L.
Published: June 2020

The technique of optical sectioning allows the visualization of a succession of images of parallel planes within a thick specimen with little or no out-of-focus interference. Ultimately, a limit is reached on the depth to which optical sections can be obtained from a given sample. This limit, up to the working distance of the objective, is largely determined by the degree of light scattering encountered by the incident excitation beam as well as the returning emission signal.

Confocal imaging was one of the first optical sectioning techniques applied to fluorescence imaging. Two-photon excitation imaging is a recently developed alternative optical sectioning technique for fluorescence imaging where an excitation wavelength of around twice the excitation peak of the fluorophore is used in a laser-scanning microscope. This excitation wavelength produces very little fluorophore excitation in the bulk of the sample, but when the incident photons are confined in space and time sufficient two-photon absorption events can take place to obtain rapid imaging of fluorophores. With high peak powers—obtained with a sub-picosecond pulsed laser source focused by a lens—sufficient photon density can be obtained for easily detectable two-photon events. Thus fluorophore excitation occurs as two photons are absorbed essentially simultaneously, which act effectively as a single photon of twice the energy (half the wavelength). Two-photon events have a quadratic dependence on intensity, and, therefore, decrease rapidly away from the focal volume of the lens. In a raster scanning system, fluorophore excitation is confined to the optical section being viewed as fluorophore away from the lens focal volume is not excited by the long-wavelength illumination.
Analysis of Cellular Organelles and Macromolecular Assemblies by Electron Energy Loss Spectroscopy
Authors: Leapman R.D. , Andrews S.B.
Published: June 2020

Recent advances in electron energy loss spectroscopy (EELS) have significantly extended the range of applications for biological microanalysis. For example, EELS can now detect physiological concentrations of the important element calcium in rapidly frozen cells with a sensitivity greater than that achievable by energy-dispersive x-ray spectroscopy (EDXS). It can also detect small numbers of phosphorus atoms bound to macromolecular assemblies, and measure water distributions in frozen hydrated tissue. Here we discuss some of these developments in the context of detection limits and mapping techniques in the scanning transmission electron microscope (STEM) and energy-filtering transmission electron microscope (EFTEM).

The useful information about elemental composition in EELS of biological specimens generally resides in weak core-edge signals corresponding to atomic concentrations in the 10−5−10−3(1–100 mmol/kg dry weight) range. For example, the Ca L2,3signal/background ratio is typically only 10−3and it is necessary to measure differences in signal that are only 104 of the background. Changes in low-loss fine structure corresponding to varying chemical composition are also very subtle; for example, detection of a 3% change in water content requires reliable measurement of a 0.1 eV shift in the low-loss intensity maximum. To extract such information requires efficient parallel detection of the energy loss spectrum and a high-brightness source to provide a sufficient number of incident electrons. The dedicated STEM is particularly well-suited for analyzing low concentrations of biological elements. If desired, the probe current can be reduced into the picoampere range for low-dose, high-resolution imaging prior to elemental analysis. The STEM’S field-emission source can then be used to deliver a current approaching 10 nA into a ~10 nm diameter probe. High electron flux conditions are ideal for spectrum-imaging applications where adequate counting statistics must be achieved within a limited pixel dwell time. The cold field-emission source of the STEM has the additional advantage of providing electrons with a narrow energy spread of <0.5 eV which is important in fine structure studies.
Calcium Quantitation with A Parallel EELS/Cooled CCD System
Authors: Ho Ruoya , Shao Zhifeng , Somlyo Andrew P.
Published: June 2020

The value of electron energy loss spectroscopy (EELS) for analyzing low concentrations of phosphorus and calcium, in biological cryo-sections, has been well documented. With currently available techniques, the sensitivities of EELS for phosphorus and calcium can be three to ten fold higher than those of electron probe microanalysis (EPMA).

Our experiments were performed with an EELS system including a Philips CM200 electron microscope equipped with a field emission gun and a STEM unit, and a GATAN 666 PEELS. We replaced the original fiber optically coupled photodiode array on the PEELS with a cooled CCD camera with lens coupling for better performance. The microscope is operated at 200 keV, allowing us to use relatively thick cryo-sections (λi = 1700 Å for carbon at 200 keV). We also used the shortest camera length in the STEM unit for achieving higher collection angle. According to our experience, the 2 mm aperture on the PEELS provides the best compromise of energy resolution and collection angle. Under these conditions, the collection semi-angle of this system is about 7 mrad and the energy resolution (full width at half maximum without specimen) is about 2.2~2.4 eV. The main limitations on using a larger collection angle are the 90 mm column between the viewing screen of the microscope and the entrance aperture of the PEELS and the poor energy resolution obtained with larger PEELS aperture.
Electron Spectroscopic Imaging and Analysis in the TEM: Have the Limits Been Reached
Authors: Ottensmeyer F. P.
Published: June 2020

Electron energy filtering in the transmission electron microscope has had two major applications: 1) contrast enhancement in the image by elimination of chromatic aberrations, and 2) microanalysis by utilization of the information carried in the electron energy loss spectrum.

The first application is unique to the fixed beam electron microscope, in which the image suffers from the interaction of the imaging lens with a broad spectrum of electron energies. Since the modal energy loss in the spectrum of 100 kV electrons traversing a carbonaceous light-atom material is about 25 eV per mean-free-path length in the specimen, a lens even with a chromatic aberration constant as good as 1 mm will blur the corresponding image to about 25 Å. In the STEM in which no imaging lenses are used after the electron beam has interacted with the specimen, chromatic aberrations do not occur; at most an effect due to the non-localization of the electron-specimen interaction may be detected as a blurring due to low-loss electrons. Even in the TEM, the effect of energy filtering to use only elastic electrons is small for bright field images of thin specimens stained with heavy atoms, since contrast and visibility is achieved primarily from the predominant elastic scatter from the heavy atoms. However, for dark field microscopy of unstained specimens the effect of filtering is dramatic, since for carbon atoms inelastic scattering dominates elastic scattering by a ratio of 3 to I.
Applications of Confocal Microscopy and Scanning Electron Microscopy to the Localization of Immunoreagents Used in Medical Diagnostic Systems
Authors: Neilly J.P. , Gagne G.D. , Bryant J. , Daanen B. , Schuette K.
Published: June 2020

Medical diagnostic assays often are based on the immobilization of immunolabeling reagents on solid substrates such as polystyrene beads, microparticles, or membranes. The distribution of immunoreagents on or within these substrates has a significant effect on product performance. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) can be used to localize immunological reagents on beads and other surfaces. In this paper we describe examples in which CLSM and SEM were used to assist in the design and troubleshooting of three diagnostic systems.

A protective overcoat is used on HIV antibody-coated 0.25“ polystyrene beads in an HIV screening assay. To visualize topographical detail of the antibody distribution on beads with and without the overcoat, beads were labeled with a fluorescent secondary antibody and examined by CLSM. On overcoated beads, the distribution of HIV antibody was relatively uniform; but on non-overcoated beads, HIV antibody distribution was patchy and located mostly in low areas of the bead surface (Fig. 1), evidence that the overcoat provided protection for the HIV antibody. In the same assay system, performance was enhanced by using beads coated with a mixture of HIV antibodies from two IgG subclasses. The relative distribution of the two primary antibodies on the bead surface was demonstrated using isotype-specific secondary antibodies and CLSM.
The Surface Structure of Biomolecules Using Correlative Microscopy: TEM, SEM, STM and AFM
Authors: Gross H. , Tittmann P. , Wepf R. , Fuchs K.H.
Published: June 2020

Freeze-drying followed by heavy metal shadowing is a long established and straight-forward TEM-approach to routinely study the structure of dehydrated macromolecular structures. Very thin specimens, such as isolated membranes or single macromolecules, can directly be adsorbed on Carbon-coated support grids.To attain the highest possible resolution, efforts were made to improve dehydration, metal shadowing and to minimize post-deposition changes in the metal film. Using our MIDILAB high vacuum cryotransfer system the freeze-dried and shadowed specimens are transferred into the microscope under high vacuum and cryo conditions. At no stage are the specimens exposed to air or warmed to ambient temperature. As a consequence, the stabilizing carbon film used in the conventional shadowing approach can be omitted and thereby images containing higher resolution structural features are recorded.
Correlative Microscopy on the Mechanism of Attachment of the Intestinal Protozoan, Giardia: Observations Using Immunofluorescence, Interference Reflection, Phase, and Video Microscopy Together with Tem and High-Resolution SEM.
Authors: Erlandsen S.L. , Macechko P.T. , Feely D.E.
Published: June 2020

The intestinal protozoan Giardia has evolved a mechanism for adherence of trophozoites to the intestinal epithelium by means of a holdfast or attachment organelle called the ventral adhesion disc. The ventral adhesion disc is formed by a monolayer of microtubules bound to one another and to the ventral plasmalemma by cross links, and each microtubule has a dorsal ribbon-like extension, composed of giardin. These dorsal ribbons are cross-linked with one another, and project from each microtubule into the overlying cytoplasm (1, 2). The peripheral margin of the ventral disc is named the lateral crest. SEM and TEM studies have shown that the monolayer of microtubules forms an overlapping spiral, which externally is visible as a spiral ridge resembling the figure six. Using immunofluorescence, the ventral adhesion disc has been shown to contain contractile proteins distributed in the lateral crest which composes the peripheral margin of the disc (3). The presence of microtubules/contractile proteins and evidence for the adhesion disc attaching to the microvillous border of epithelial cells suggests a contractile mechanism for trophozoite attachment (4, 5).