bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Varying Salinity on Leaf Ultrastructure of Zannichellia Palustris
Authors: Barnabas AD , Jimmy R , Govender K , Przybylowicz WJ , Mesjasz-Przybylowicz J
Published: July 2020

Zanichellia palustris is a submerged halophyte which occurs in waters of low salinity (5%o to 10%o). It is not capable of surviving at high salinity. Reasons for its inability to tolerate hypersaline conditions is important to our understanding of its biology. in the present study, leaf ultrastructure of plants growing at normal salinity was compared with plants growing at high salinity so as to assess the effects of hypersalinity. Attention was focused on ultrstructural changes occurring in leaf blade epidermal cells.

Plants were grown in seawater at two salinities : 10%o (control) and 20%o (high salinity). Pieces of mature leaf blades from both treatments were harvested and prepared for Transmission Electron Microscopy (TEM) following standard procedures. in addition, the overall distribution and concentration of chlorine (Cl) in the leaves was ascertained since it is the most abundant anion in seawater and is important in considerations of salt tolerance in submerged halophytes. Cl was determined by means of a nuclear microprobe. Pieces of sectioned leaves were rapidly frozen, freeze dried and carbon coated. Elemental distribution maps of Cl were obtained using the true elemental imaging system (Dynamic Analysis). Two complementary techniques, Proton Induced X-Ray Emission (PLXE) and Proton Back Scattering (BS) were performed simultaneously using the GeoPIXE suite of programmes. Sample thickness and composition of major elements were obtained from the BS spectra.

The ultrastructural morphology of leaf blade epidermal cells, which possess transfer cell characteristics differed at each salinity. While the cytoplasm was well preserved in epidermal cells of plants at the control salinity : 10%o (Fig 1), considerable cytoplasmic damage occurred in epidermal cells of plants at high salinity, in the form of breakdown of membranes such as the plasmamembrane and tonoplast, and senescence of various organelles including chloroplasts and mitochondria (Fig. 2).
TEM Embedding Technique for Immunocytochemistry of Cultured Cells
Authors: Sands S , Meek W
Published: July 2020

Vero cells (African green monkey kidney epithelium) contain very dense cytoplasm with numerous ribosomes and mitochondria. They also contain an impressive network of cytoskeletal proteins, especially vimentin intermediate filament. Vimentin is present in all cells of mesenchymal origin, but their localization in the cell is usually restricted to a perinuclear position. Vero cells exhibit large bundles of vimentin filaments in a network, coursing throughout the cell. Additionally, many vimentin filaments connect to each other in an intermediate filament focus, or vertex. We investigated these vimentin vertices using immunofluorescence, scanning and transmission electron microscopy.

The processing of cultured cells for transmission electron microscopy is a difficult task, especially when one desires to preserve in situ relationships. When sectioning epithelial cell lines, a single cell layer (approximately three micrometers) of tissue is available, so a few thick sections will remove all the cells in the block. A traditional method for TEM of cultured cells is to disrupt these cells from their substrate and then centrifuge these cells into a pellet which can be sectioned. While it may be easier to obtain thin sections of cultured cells employing this method, many characteristics of the cells cannot be adequately investigated, including cell-to-cell junctions, cell shape on a substrate, cell morphology associated with a substrate, position of organelles in a cell growing on a substrate, and morphology and relationship of mitotic cells.

Growing cells on Thermanox cover slips and embedding in LR White polymerized in gelatin capsules at 55°C affords an effective method of viewing and labeling cells in culture. When the resin has been polymerized, the Thermanox coverslip is carefully removed from the block by using a razor blade to pry it off. The cells remain in the LR White, exposing them to the surface of the block. in fact, the very first sections of the block contain cells. Although this prevents one from facing the block, the exposed surface is usually flat enough to obtain good thin sections.
Glutathione Distribution in Transformed Leukocytes Determined by Immunoelectron Microscopy
Authors: Ault Jeffrey G , Lawrence David A
Published: July 2020

Glutathione (GSH) is a tripeptide thiol found in virtually all mammalian cells. GSH is a cofactor in several enzymatic reactions and is important in intracellular cysteine storage. Probably the most interesting of its many functions is its role in protecting the cell against the detrimental effects of ionizing radiation, reactive oxygen compounds, free radicals, and toxic xenobiotics. GSH is the reduced form which can be oxidized to a disulfide form (GSSG) or to form mixed disulfides with proteins. The GSH oxidation-reduction cycle maintains a high GSH to GSSG ratio which provides a reservoir of reducing equivalents that can nullify reactive oxygen species and detoxify xenobiotics. The study of glutathione in the fields of cancer research and immunology has attracted much attention, especially with regard to changes with age.

In this study, we have determined the cellular distribution of glutathione using immunoelectron microscopy. A mouse monoclonal antibody (8.1-GSH) against the glutathione adduct with Nefhylmaleimide (NEM) was used.
A Novel Method of Data Collection for Automated Electron Tomography Based upon Pre-cal1bration of Image Shifts and Defocus Changes
Authors: Ziese Ulrike , Janssen Ries , Geerts Willie , van der Krift Theo , van Balen Auke , Ruijter Hans de , Jong Krijn de , Verkleij Arie , Koster Bram
Published: July 2020

Electron tomography is a three-dimensional (3D) imaging method with transmission electron microscopy (TEM) that provides high-resolution 3D images of structural arrangements. with electron tomography a series of images is acquired of a sample that is tilted over a large angular range (±70°) with small angular tilt increments. For the 3D-reconstruction, the images of the tilt series are aligned relative to each other and the 3D-reconstruction is computed. Electron tomography is the only technique that can provide 3D information with nm-scale resolution of individual and unique samples. Routine application of electron tomography will comprise a major step forward in the characterization of complex materials and cellular arrangements. When collecting tilt series for electron tomography image shifts and defocus changes have to be corrected for by the human operator. The repetitive correction of these changes is highly time consuming, error prone and very hard to carry out under low-dose imaging conditions.

Many practical problems are overcome when electron tomography data collection is performed in an automated fashion. Automation includes the (a) image acquisition on a (digital) CCD camera, which implies that (b) changes in image position and defocus can be detected by on-line image processing and (c) immediately be corrected for by computer control of the microscope, (d) Finally, tilt series are directly available in digital format for subsequent processing. Typically, carrying out such an experiment would take a day, and the actual data collection 2-4 hours. in spite of the enormous progress made in terms of data collection speed during the last few years, the current status of automated tomography still does not meet the requirements that would make it a routinely applicable tool. For a great number of biological assays and research projects, results obtained under different experimental conditions have to be compared, and series of experiments have to be carried out. Therefore, we propose a novel approach for recording a tilt series that significantly increases data collection speed, and widens the applicability of the technique.
Electron Spectroscopic Tomography for Materials Science
Authors: Möbus G , Inkson B J
Published: July 2020

Tomographic 3D-reconstructions from tilt series of projections differ in two major aspects when moving from biochemistry (e.g.) to materials science applications: (I) Crystalline inorganic materials fail the weak phase image formation approximation and suffer from dynamic and nonlinear contrast contributions (which depend for both CTEM and HREM on atomic lattice plane orientation). (II) exposure tolerance increases by two orders of magnitude. We therefore propose energy filtered tomography with inelastic electrons (electron spectroscopic imaging, ESI) as a new method for 3D-reconstruction of free or buried subsurface nanostructures or nanoparticles. Energy filters are not used here to improve SNR by removing inelastic background, but to provide the necessary projection relationship between a 3D concentration distribution and the (processed) image intensity. Ideally, a 4-dimensional data space is recorded for a single tilt axis tomography experiment, D=D(δE, Θ,x,y), (with 5E as energy loss, Θ as tilt, and (x,y) as image coordinates). The material has to withstand exposures of T = t × Ntilt × Nloss (t = 5...20sec per image, Ntilt >12 directions, Nloss = 5....20 energy loss values).
Using Electron Tomography to Determine How Kinetochores Bind and Alter the Conformations of Microtubule Plus Ends
Authors: McEwen BF , Barnard RM , Hsieh C-E , J. Frank
Published: July 2020

Chromosome alignment during mitosis and meiosis is mediated through the interaction between kinetochores and spindle microtubules (Mts). Kinetochores are fibrous mat-like structures, located at the primary constriction of chromosomes, that bind spindle Mts, generate poleward chromosome motion, and delay progression through mitosis until chromosome alignment is complete. Mts are polar polymers that function as tracks for the movement of a variety of cellular organelles and vesicles. Chromosome alignment requires a unique form of Mt-based motion because kinetochores capture and bind the plus ends of a bundle of Mts, rather than moving along the lateral surface of a single Mt. As a result, the direction of chromosome motion must be coordinated with the growth and shrinkage of Mts. Furthermore, the kinetochore maintains continuous attachment to growing and shrinking Mts and simultaneously permits the addition and dissociation of tubulin subunits within its confines
Automation of Tilt Series Acquisition in Transmission Electron Microscopy for Applications in Biology and Materials Science
Authors: Daberkow Ingo , Feja Bernhard , Sparlinek Peter , Tietz Hans R
Published: July 2020

During the last decade, computation of a three-dimensional image from a tilt series (3D reconstruction) has become a well established method, of which a variety of implementations are available. The term “electron tomography” is now generally used for this type of data acquisition and 3D reconstruction. An overview over the techniques involved is given in.

With the introduction of micro-processor-controlled TEMs and cooled slow-scan CCD cameras and with the progress in performance of high-speed computers, automation of complex imaging procedures became mainly a task of developing appropriate software, using the control facilities of the microscope. in this way, automated electron tomography was realized in 1990 at the Max- Planck-Institute for Biochemistry in Martinsried, and at about the same time at the University of California in San Francisco (UCSF). New techniques for automatic focusing and alignment, developed somewhat earlier, have been integrated in these automated tomography procedures. in the following we discuss the requirements of automatic data acquisition and the present implementation for several TEMs.
Bringing Together High- and Low-Resolution Data: Electron Tomography of Budding Enveloped Alpha Virus
Authors: Cheng RH , Hultenby K , Haag L , Forsell K , Garoff H , Hsieh C-E , Marko M
Published: July 2020

The multi-layered architecture of alphaviruses is built up with the registration of nucleocapsid (NC) proteins and envelope spike proteins across a lipid bilayer. At the surface of the NC, capsid proteins are organized as 42 capsomers such that the three tails from each spike complex bind three capsomers. Alphaviruses have been extensively studied using cryo-EM and X-ray crystallography at near-atomic resolution (see review by Sedzik et al.). This work involves averaging images of many isolated virions, and makes use of the symmetry of the particle. The study of assembly and budding of virus particles at the cell surface, however, requires structural determination of individual virions in situ. Electron tomography offers a means for such studies.

Small features are obscured in typical thin-section (ca. 50nm) TEM micrographs due to the projection in 2D of all the structures throughout the section thickness. However, slices thinner than lnm can easily be obtained from tomographic reconstructions. Thus, small structures such as capsomers can be seen, even in thick (>100nm) specimens (Fig. 1b).
CTF Correction in Electron Tomography of Insect Flight Muscle
Authors: Winkler Hanspeter , Taylor Kenneth A
Published: July 2020

In order to extend the resolution available in electron tomograms, we have been experimenting with various deconvolution procedures that will ultimately enable correction of the focus gradient thereby allowing the resolution to be extended to beyond the first zero in the contrast transfer function (CTF). This effort requires first a determination of the amount of amplitude and phase contrast in the typical specimen used by us.

For the determination of the percentage of amplitude contrast a focus series of 19 images was taken at a magnification of 13500 on a CM300. The micrographs were digitized on a PDS scanner, the pixel size was 0.888 nm. After correction of translational shifts, rotations, and defocus dependent magnification differences the image restoration was carried out according to [1,2]. From the resulting complex wave function an averaged amplitude contrast amount of 18% was obtained for the stained specimen. The phase contrast part and amplitude contrast part are shown in Figs, 1b, and 1c, respectively, and can be compared with the micrograph taken at 960 nm underfocus (Fig. 1a).
Porous Vycor Glass as a Model System for Biodevices: An AFM Study of Properties of Water in Confined Geometries
Authors: Quist Arjan P , Lal Ratnesh
Published: July 2020

Structural and dynamic studies of the adsorption behavior of small molecules within and on the surface of porous systems are of great interest for designing biocompatible and sustainable biodevices. Porous vycor glass is an ideal system for such studies because of its well characterized hydrophilic network of cylindrical pores. Moreover, the pore sizes in vycor are directly comparable to pore sizes of systems like macromolecules and biological membranes. Molecular dynamics simulations of vycor-water interactions as well as some structural data from neutron scattering and diffraction experiments are available. Close to the pore surface the number of water-water hydrogen bonds is reduced, and compensated by vycor-water hydrogen bonds. Insight into the behavior of water molecules in those confined geometries could provide necessary and relevant information for designing biodevices for tissue generation, as well as about contamination- and inflammation affinities of implant materials.

Here we present an Atomic Force Microscopy (AFM) study of vycor at different levels of surface hydration.
A Tissue Engineering Model for Tractional Organization of Cells and Matrices
Authors: Bhatnagar Rajendra S , Nicoll Steven B , Qian Jing Jing , Smith Nancy
Published: July 2020

Tissues are characterized by highly distinctive microarchitecture and overall form that are critical to tissue specific function. with increasing interest in tissue engineering to create surrogates for human tissues and organs, innovative techniques have been developed to generate scaffolds that display form, and microarchitecture mimicking physiological structures. While this artifice may generate pre-programmed shapes, it fails to take advantage of the inherent ability of cells to organize themselves and their surroundings. The generation of mechanical forces by the cellular cytoskeleton plays a critical role in the organization of matrix and of cellular colonies. The anchorage of the cytoskeleton to a substrate is essential for cellular tractional processes. in tissues, cells are anchored in a stationary, 3-D network of collagen in a highly characteristic spatial arrangement. This spatial order arises from vectorial deposition of matrix and its subsequent tractional organization by cells. The junction of the cell binding domain of collagen with specific integrin receptors, and the cells’ cytoskeleton comprises the apparatus for the interconversion of mechanical and biochemical energy.
Morphological Characterization of an Elastin-Mimetic Triblock Copolymer Utilizing CRYO-HRSEM
Authors: Wright ER , Conticello VP , Apkarian RP
Published: July 2020

The elastin-mimetic tri-block copolymer, C5, with the polypeptide repeat [((VPAVG)(IPAVG)3(VPAVG))m((VPGVG)2(VPGEG)(VPGVG)3)n((VPAVG)(IPAVG)3(VPAVG))m] was produced via protein hyper-expression utilizing a pET plasmid and Escherichia coli (BL21- Gold(DE3)) as the bacterial host. The gene coding for the polypeptide was produced by a multimerization protocol that has undergone recent modifications. A sample of the elastinmimetic block copolymer, C5, was prepared as a 20 to 25 percent protein solutions in sterile ddH20. Approximately 10 μL of the solution was pipetted into 3 mm gold planchets (Balzers BU 012 130T), which had been pre-equilibrated to 4°C in an isothermal environmental cooler (Torrey Pines Scientific). The temperature of the cooler was raised to 20°C and allowed to stabilize for 10 minutes. The solidified samples, were plunge-frozen in liquid ethane at its melting point (−183°C); the samples were stored in liquid nitrogen (LN2). A sample was transferred to and mounted on the precooled (∽−170°C) Oxford CT-3500 cryo-stage held in the cryo-preparation chamber.
Artificial Myocardium: Design Principles and Substratum
Authors: Yost Michael , Price Robert , Simpson David , Terracio Louis
Published: July 2020

Death and disability due to cardiovascular disease and congenital anomalies remains a significant health problem in the United States. Despite improvements in detection, patient management, surgery and preventative medicine, the quality of life for people who suffer from cardiovascular dysfunction has a major impact on our society. The intact heart is an elaborate three-dimensional structure that insures the orderly propagation of electrical signals coordinating the contraction and relaxation of the ventricular wall. Localized loss of muscular tissue as a result of congenital defect or disease process alters this structural arrangement and impairs overall cardiac function. Conventional surgical techniques cannot begin to adequately restore the subtle structural and functional relationships in the heart. The ability to construct a tissue-engineered prosthesis composed of cardiac muscle cells in a collagen-based scaffold may potentially offer a superior alternative to currently available surgical techniques.

A tissue engineered myocardium must have the following components: First, it must develop and maintain the correct cellular phenotype as well as a functioning contractile apparatus of parallel myofibrils, Second it must be able to form gap junctions within itself and with the native tissue and these gap junctions must be competent at conducting electrical pacing as well as other biochemical signals, and Third, it must be capable of participating in and contributing to the rhythmic contraction of normal myocardium as well as accommodate the changes in contraction frequency ubiquitous in the cardiac environment
Electrospinning Applications in Bioengineering: Fabrication of Bio-Engineered Skeletal Muscle
Authors: Telemeco T , Bowlin GL , Matthews JA , Cohen NM , Vida M , Wnek GE , Terracio L , Simpson DG
Published: July 2020

The objective of this study is to develop a skeletal muscle prosthetic composed entirely of natural or otherwise bioresorbable materials that recapitulates the structure and function of intact muscle. in our fabrication strategy we begin by electrospinning (see Mathews et al., this volume) a hollow, cylindrical fascial sheath composed of poly-glycolic acid (PGA), poly-lactic acid (PLA), Type I collagen microfibers or a blend of these materials (figure 1). The resulting fascial sheath is a highly porous fabric composed of interwoven fibers that range from less than 1 micron to 2-5 microns in diameter (patents pending). Next, we isolate neonatal rat skeletal myoblasts by enzymatic dissociation. The dissociated tissue is subjected to an interval of differential adhesion to enrich the preparation in skeletal muscle myoblasts. The final cell pellet of myoblasts is then suspended at high density in Type I collagen. This suspension is polymerized at 37°C for 10-15 minutes and used to fill a fascial sheaths (patents pending).
Microspectroscopy Using a Solid Immersion Lens
Authors: Poweleit CD , Menéndez J
Published: July 2020

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.

As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.
Pharmaceutical Polymorphism Studies by Infrared Spectroscopic Imaging
Authors: Lewis Lori , Troost Peter , Lavery Donald , Nishikida Koichi
Published: July 2020

Many drugs are known to crystallize in different polymorphic forms or as solvates. Solubility, melting point, density, hardness, optical properties, vapor pressure, and a host of other physical properties may all vary with polymorphic form. Not only do the various crystal structures of a given pharmaceutical compound affect the efficacy of the drug, but they may also carry enormous legal implications. Much product revenue can depend upon the identification and patent protection of certain polymorphic forms. Thus, the control of crystallization is a very important process parameter, and techniques such as X-ray crystallography, infrared spectroscopy, Raman spectroscopy, and polarized light microscopy are routinely used in the characterization of crystalline drugs.

This presentation will involve the investigation of a variety of pharmaceutical polycrystalline films using infrared (IR) spectroscopic imaging. Preliminary data was collected using a conventional FT-IR microscope with visible polarized light capabilities. Correlating data was then collected using a commercially available IR imaging microscope.
Emerging Viral Hemorrhagic Fevers
Authors: Zaki Sherif R , Goldsmith Cynthia S
Published: July 2020

Clinically, the combination of fever and hemorrhage can be caused by many pathogens, including viruses, rickettsiae, bacteria, protozoans, and fungi. However, the term viral hemorrhagic fever (VHF) is usually reserved for systemic infections characterized by fever and hemorrhage caused by a special group of viruses that belong to four different families: Filoviridae, Arenaviridae, Bunyaviridae, and Flaviviridae. All members are lipid-enveloped RNA viruses; except for filoviruses, where the resorvoir remains unknown, these viruses are transmitted to humans by arthropods and rodents. The VHFs are characterized by abnormal vascular regulation and damage. The VHFs all have similar clinical pictures with mortality rates of 15-30% or in the case of Ebola virus, up to 80%. Between 1993 and 2001, more different VHFs and related diseases were reported than during any comparable period over the past several decades. These diseases include Ebola VHF in Uganda in 2000, in Zaire in 1995 and in Gabon between 1994 and 1996; ongoing cases of Marburg hemorrhagic fever in the Democratic Republic of Congo beginning in 1998; Rift Valley fever in Saudi Arabia and Yemen in 2000 and in Kenya in 1997; Lassa fever in Sierra Leone in 1997; hantavirus pulmonary syndrome in the Americas since 1993; and imported cases of dengue hemorrhagic fever from Central and South America, and yellow fever from Africa during the 1990s.
Polyomaviruses As Emerging Pathogens
Authors: Howell DN , Miller SE
Published: July 2020

Polyomaviruses are double-stranded DNA viruses of the family Papovaviridae. They replicate in cell nuclei, where they form 40-50-nm, non-enveloped, icosahedral nucleocapsids that exit the host cell by lysis (Fig. 1A-C). Polyomaviruses with pathogenic potential in both human and non-human hosts have been known for many decades. in recent years, however, new pathogenic polyomaviruses have been described in man, non-human primates, and other animals. New forms of acquired and iatrogenic immunocompromise have also led to changes in the prevalence and pattern of disease caused by well-characterized polyomaviruses. This presentation provides an overview of emerging polyomavirus diseases, illustrated with vignettes from our diagnostic practices. in many cases, the detection and monitoring of polyomavirus infections has been facilitated by ultrastructural examination.

Two well-characterized polyomaviruses cause disease in humans, almost invariably in the setting of immunosuppression. JC virus, described in 1971, is the causative agent for progressive multifocal leukoencephalopathy (PML), a generally fatal disorder characterized by patchy, progressive destruction of the cerebral white matter.
Intestinal Microsporidiosis
Authors: Marc Orenstein Jan
Published: July 2020

Sixteen years have passed since a microsporidian was first reported as an opportunistic pathogen in HIV/AIDS. to date, two new genera, Enterocytozoon and Trachipleistophora, and 5 new species, Enterocytozoon bieneusi, Encephalitozoon hellem and E. intestinalis, and T. hominis and T. anthropophthera have been described infecting patients with AIDS. E. bieneusi and E. intestinalis have been among the most common intestinal pathogens diagnosed as causes of diarrhea and wasting in HIV/AIDS.

Members of their phylum, Microspora, have in common a hollow polar tube that is tightly wound up in their spores. The coiling up of the polar tube, just beneath the cell wall, allows a structure that is several times its length to be packaged within a spore. E. bieneusi, which has the smallest of all microsporidian spores, 1 x 1.5 ¼m, overcomes its size limitations by packaging its polar tube in 2 layers of 3 coils each. When conditions are right, this unique structure is extruded from the spore and becomes the “needle of a syringe”.
Emerging and Reemerging Viral Pathogens: A Microscopic Overview
Authors: Goldsmith Cynthia S , Zaki Sherif R
Published: July 2020

During the 20th century, the advent of vaccines and antibiotics, and continued improvements in urban sanitation and water quality resulted in a dramatic decline in mortality due to infectious diseases. There was a brief period of optimism in the mid-1900's that infectious pathogens would no longer be a significant cause of death in the United States. For a number of reasons, this trend had reversed by the end of the century, and the rates of death caused by infectious diseases began rising. in recognition of this change, the Institute of Medicine issued a report in 1992 that called attention to the major factors contributing to the emergence and reemergence of infectious diseases. Among these were the following: increased human encroachment on wilderness habitats, resulting in changes in the ecosystem and increased contact with animal and insect vectors which may harbor unknown infectious agents; sizable growth in human population, resulting in increased urbanization and crowding; increased global travel; changes in human behaviors; and microbial evolution.
Detection of Early Cytomegalovirus Infection in Pathologial Specimens by H&E, IHC, ISH, Grocott’S and Modified Steiner Silver Stain for LM and EM: A Review
Authors: Chien K , Heathershaw ML , Heusser RC , Shiroishi H , Gonzalez R , Nast CC , Cohen AH
Published: July 2020

The diagnosis of cytomegalovirus (CMV) in tissue sections is usually quite easy because of the characteristic appearance of intranuclear inclusions. At times the morphological features are equivocal, the nuclear findings may be atypical or only a single cell may be affected, thereby creating uncertainty about the diagnosis. This report reviews our experience with the various microscopic techniques that can be used to make definitive identification of CMV.

EM - Visualizing the viral particles in a single or even lysed cell by routine electron microscopy can make the definite diagnosis, but section size limits the usefulness in the detection of early CMV infection (fig. 1). However, if a diagnosis can not be made with certainty by the following methods, EM can be performed on stained paraffin sections for confirmation.

H&E - A Hematoxylin & Eosin stain that discloses characteristic intranuclear inclusions surrounded by a clear halo indicates CMV infection (fig.2A).
Public Health Laboratory Preparedness; Bioterrorism the New Challenge
Authors: Meyer Richard F
Published: July 2020

In the event of a bioterrorist attack, rapid screening, agent identification, and confirmatory diagnosis will be critical, so that prevention and treatment measures can be implemented quickly. However, because few biologic agents thought likely to be used as biological weapons represent major public health problems in the United States, we have limited capacity to diagnose them, either at the state and local or the federal level. to begin to address this new public health challenge the Laboratory Response Network for Bioterrorism (LRN) was established.

The LRN is a multi-level system designed to link state and local public health laboratories, clinical, military, veterinary, agricultural, water and food-testing laboratories. Operational in August of 1999, the LRN was established as a consequence of Presidential Decision Directive 39, increased congressional awareness of the huge biological weapons program in the former Soviet Union, the high level of risk to national security and subsequent emergency funding to the Centers for Disease Control and Prevention under the DHHS Operating Plan for Anti- Bioterrorism Initiative.
Toward Quantitative Annular Dark Field Imaging
Authors: Vanfleet RR
Published: July 2020

Annular Dark Field imaging has the potential to be directly quantifiable. By this I mean that with careful measurement, the absolute image intensity has physical meaning. Unlike Bright Field TEM, the ADF image has no contrast reversals with focus and with the exception of thick specimens there are no contrast reversals with changes in thickness. Thus, image intensity is related to thickness, composition, orientation, and structure of local regions whose size is determined by the electron probe. The ability to extract quantitative information about the specimen from the intensity requires careful collection of the intensity data and a solid understanding of how that intensity will change with thickness, composition, orientation, and structure. The qualitative effect of thickness and composition has been well shown in the literature but more quantitative approaches have been lacking.

The simplest models of ADF imaging treat each atom interacting
Atomic-Scale Study of a Co/AlOx/Co Magnetic Tunnel Junction
Authors: Plisch MJ , Chang JL , Plisch MJ , Buhrman RA
Published: July 2020

Magnetic tunnel junctions (MTJ) which consist of two ferromagnetic electrodes separated by a thin (∼10Å) tunnel barrier can exhibit a magnetoresistance of greater than 40% at 295 K. They hold substantial potential for application as computer memory and magnetic field sensors. Much about the spin-dependent tunneling process is still not understood. in order to identify features that may affect the spin-polarization of the tunnel current, we have used the UHV STEM at Cornell University to perform atomic-scale imaging and EELS on an MTJ system. The MTJ was sputter deposited on (100) Si with layer sequence Co 60Å/Al 12AÅO2 exposure/Co 100Å.

The annular dark field (ADF) image (Fig. la) shows the A10x barrier layer has a fairly uniform thickness of about 15 Å. Its profile (Fig. 1c) appears diffuse partly due to layer roughness rather than atomic mixing. in bright field (BF) the appearance of strong Fresnel fringes (Figs. 1b,c), due to a large difference in average electrostatic potential between Co and AlOx, complicates interpretation.
Dopant Distribution Analysis in Carbon Nanotubes By Z-Contrast Imaging
Authors: Dickey EC
Published: July 2020

Similar to graphite and carbon fullerenes, the physical properties of carbon nanotubes (NTs) can be altered by ex-situ doping or by functionalizing the nanotube walls. Such mechanisms for tailoring the properties of carbon NTs expand their potential utility in electronic, optical and structural applications. Both acceptor (e.g. I2, Br) and donor-type (e.g. K, Rb) dopants have been successfully intercalated into single-wall NT (SWNT) bundles, and the transport properties of these doped species are greatly altered. For example, iodine-doped SWNTs exhibit a 40% decrease in DC conductivity. Doped SWNTs are a completely new class of nanostructured materials, and there is a large demand for understanding the structure of the various doped-compounds as well as the ramifications for the electronic properties of the material.

In this paper we demonstrate the utility of Z-contrast scanning transmission electron microscopy (STEM) for elucidating the structure of doped nanotubes.
Lorentz Stem: A Digital Approach to an old
Authors: Zaluzec Nestor J
Published: July 2020

The study of magnetic materials using electron column instruments has been a fruitful area of research for microscopists/microanalysts for nearly 4 decades. A number of techniques have been developed for both the SEM and TEM which enable visualization of magnetic fields ranging from Fresnel imaging (Fuller and Hale, Silcox), Differential Phase Contrast (Chapman), through to Electron Holography (Tonomura). The latter are generally qualitative, while the former quantitative, albeit at the price of significant complexity. The advent of microprocessor control of modern instruments, CCD detectors, and experimental diligence allows us to revisit and in fact revitalize this area of measurement.

The experimental work reported here is being carried out in the ANL AAEM HB603Z 300 kV FEG instrument. in this instrument, the electron optical column was operated in a zero field mode (figure 1), where the objective lens is turned off and the probe forming lens functions were reallocated to the C1, C2, and C3 lenses.
Complementary Structural Information from Diffraction Patterns in STEM: Accurate Thickness Measurement with Pattern Matching
Authors: Zuo J M , Shi YF
Published: July 2020

In this paper, we discuss the advantage of combining STEM imaging with diffraction. in addition, we present a set of accurately calculated convergent beam electron diffraction (CBED) patterns for Si, which highlights the sensitivity of electron diffraction to structure. The calculation takes the full account of crystal bonding by including known experimental structure factors in simulation. Such calculated patterns can be used for accurate determination of the sample thickness, crystal orientation and polarity (for acentric crystals). Calculations with and without crystal bonding show significant difference in calculated intensities, equivalent to a change in thickness about several nanometers for thick samples.

The annual dark field (ADF) imaging mode in scanning transmission electron microscopes offers the unique advantage of combining high-resolution electron imaging and spectroscopy with diffraction. The large cutoff angle used in ADF imaging allows simultaneous recording of diffraction patterns for quantitative structural information, while ADF imaging gives the precise position of the probe and the image of the sample.
A Sub-Ev Resolution Soft-X-Ray Spectrometer for a Transmision Electron Microscope to Obtain the Density of States of the Valence Band
Authors: Terauchi M , Yamamoto H , Tanaka M
Published: July 2020

We developed a high energy-resolution electron energy-loss spectroscopy (EELS) microscope to investigate electronic structures from specified small specimen areas [1]. EELS gives us information of the dielectric properties and the partial density of states (DOS) of the conduction band. Together with the DOS of the conduction band (unoccupied states), the DOS of the valence band (occupied states) is imperative to understand the whole electronic structure. Unfortunately, the DOS of the valence band cannot be reached directly by EELS.

A partial DOS of the valence band can be obtained by fluorescent X-ray emission spectroscopy (XES). A conventional EELS instrument attached to a TEM usually takes spectra with an energy resolution of about 1 eV, by which the DOS of conduction bands has been studied using ELNES until now. Thus, an energy resolution of about 1 eV is at least necessary for the study of the DOS of the valence band.
Exit Wave Reconstruction of Interfaces Between Zno Films and ScalmgO4 Substrates
Authors: Wessler B , Steinecker A , Mader W
Published: July 2020

Epitaxial ZnO thin films were produced on basal plane ScAlMgO4 (SAM) by chemical solution deposition (CSD) (fig. 1). ZnO crystallizes in the wurtzite structure and ScAlMgO4 is isostructural to YbFe2O4, a layered structure shown in fig. 2. The crystallographic orientation relationship was observed by XRD using θ-2θ scans and off-axis φ scans to be (0001)zno ∥ (0001)SAM and  zno ∥  SAM. The lattice mismatch between film and substrate is 0,09%.

For TEM observations in cross-sectional geometry two substrates were glued together with the epitaxial film surfaces. Electron transparent specimens were produced by standard methods of mechanical thinning and ion beam etching. The HRTEM investigations were performed on a Philips CM300 FEG electron microscope with Ultra-Twin lens operated at 300 kV. After correction of axial coma and two-fold astigmatism images were recorded on a slow-scan lk × lk CCD camera with a sampling of 0.0193 nm/pixel.
Radial Distribution Function of Tin Thin Film Adjusted by Experimental Phase Shifts
Authors: González-Valenzuela C , Espinosa-Magaña F , Martínez-Sánchez R , Duarte-Möller A
Published: July 2020

Titanium Nitride thin film was obtained by the DC-Sputtering technique and characterized using the transmission EXEELFS formalism. The experiments were performed in a CM 200 transmission electron microscope with a GAT AN 766 PEELS attachment. A primary energy of 200 keV and a spot size of 440 nm with an average acquisition time of 5 min were used. The atomic distribution obtained using EXEELFS was corrected with the respective experimental phase shifts. Atomic parameters were compared with those corrected by EXAFS phase shits and the known crystallographic values.

The energy loss spectra for the sample, around the ionization Ti L23-edge and N K-edge corrected for background and multiple scattering process is shows in Figure 1. N K-edge appears at an energy loss of 400.4 eV and the Ti L23-edge is located at an energy loss of 464.3 eV. These values on energy are shifted 0.6 eV respect to the isolated transitions.
Anaysis of Lacbed Patterns from A Microtwin in Cobalt
Authors: Su Kim Hwang , Ahn Byung Ryang
Published: July 2020

Recently LACBED (Large Angle Convergent Beam Electron Diffraction) studies for identifying the nature of stacking faults has been reported in [1,2]. Here we report the LACBED study for a microtwin whose images are usually similar to those of an intrinsic or an extrinsic stacking faults (for this discussion, see [3]).

Observations: Thin foils of cobalt with the thickness of about 180 nm (f.c.c phase, a=0.354 nm) were examined by a Philips CM200. Fig. 1 shows strong beam dark field images of microtwins or stacking faults. Fig. 2 shows the bright field LACBED pattern taken near the area marked as a circle in fig. 1. The specimen height, from the convergent point of beams, was about 0.0586 mm and the convergent angle was 0.615 degrees.

Calculations and analysis: Analysis of fig. 1 alone indicates the encircled fault an extrinsic stacking fault.
Uncertainties in Stereo Lattice Imaging
Authors: Qin W , Fraundorf P
Published: July 2020

Three-dimensional reconstruction in TEM is an established technique in both electron diffraction crystallography and electron tomography [1,2]. By stereo lattice imaging, we refer to a different task: determination of unit cell parameters in 3D using only direct-space lattice images at two or more (often widely varying) orientations [3,4], This note concerns the uncertainties associated with lattice parameter determinations by this technique. in particular, for decreasing crystal thickness the broadening of reciprocal lattice spots increases one’s chances to visualize lattice fringes. At the same time, however, it introduces uncertainties in reciprocal lattice vector length and direction.

In the following discussion, sources from which uncertainties arise are assumed to be uncorrected. Three sources of uncertainty for reciprocal lattice vectors which lie in the plane of the specimen stage (and hence can be imaged directly as fringes) are, in order of decreasing relative size as follows:
Fringe Visibility Maps
Authors: Fraundorf P , Qin W
Published: July 2020

The phrase “fringe visibility map” here refers to high-resolution images of uniform-thickness single crystal foils showing locally hemispheric deformation (i.e. bent into the shape of a watchglass), and to various mathematical analogs thereof. As the availability of “diffraction information” in direct-space form increases, for example with the availability of HREM and z-contrast lattice images, fringe visibility maps may serve as the direct space analog to Kikuchi maps, i.e. to diffraction pattern maps of Kikuchi line pairs as a function of specimen orientation, and their various cartoonifications.

Figures 1 to 3 are schematic Mathematica-generated fringe visibility maps for face-centered, body-centered, and diamond face-centered cubic lattices, respectively. Here we have turned the “locally hemispheric” concept around and drawn fringes visible when one is viewing a spherical particle of the appropriate thickness, along varying beam directions (rather than lattice orientations) parallel to the local radius vector on that sphere.
Exit Wave Reconstruction and Elemental Mapping of Twin Boundaries in the System Zno - Ga2O3
Authors: Barf J , Walther T , Steinecker A , Mader W
Published: July 2020

Polycrystalline ZnO was sintered with 5 mol.% Ga2O3 at 1350°C for lhour in air. Samples for transmission electron microscopy (TEM) were prepared by cold pressing, grinding, dimpling and Argon ion-milling.

ZnO crystallizes in the hexagonal wurtzite structure. Bright field and dark field images reveal lamellar defect structures which are not observed in undoped ZnO. Electron diffraction shows that the lamellar regions consist of heavily twinned ZnO. The twin boundaries (TB) of both twin variants are parallel to lattice planes of type { }. Lattice images along reveal narrow planar twin boundaries as well as a diffuse image contrast within the twin lamellae (Fig. la). to characterize the nature of the boundaries we recorded dark field images of the twinned regions using reflections of type ±{0002}. in combination with microdiffraction it can be shown that the diffuse boundaries are inversion domain boundaries (IDB) which alternate with the sharp TB. This microstructure is related to the polarity of ZnO.
Measuring Interface Potential of Bi2sr2cacu2O8 (001) Twist Boundaries by off-Axis Electron Holography
Authors: Schofield M A , Zhu Y
Published: July 2020

The potential variation, charge transfer and lattice distortion across grain boundaries in polycrystalline superconductors play a crucial role in the transport properties of the material. in particular, the grain interfaces often act as weak links to the superconducting current, which limits the critical current densities that may be obtained. in the case of the high Tc superconductor Bi2Sr2CaCu2O8 (Bi-2212), special interest is paid to (001) twist boundaries since, in part, they are dominant in c-axis aligned tapes and wires, but more interestingly because the superconducting critical current is found to be independent of twist angle for this system. Such grain boundary behavior is presently not understood, and is further puzzling since “impurity phases” of Bi-2223 or Bi-2201 (consisting of additional or missing Cu-Ca-0 planes, respectively) are commonly observed at the (001) twist boundaries. with the rich structure found at these types if interfaces, understanding the potential distribution may lead to new insight about the boundary properties.
Evaluation of Methods for Extracting Chemical Information from Eels Line-Spectra Across Interfaces
Authors: Imhoff D , Sikora T , Pailloux F , Tencé M , Colliex C
Published: July 2020

EELS fine structures on characteristic core edges are closely related to the bonding type and structural environment around the excited atoms. Consequently, they constitute useful hints for investigating the electronic properties at interfaces. One major difficulty then lies in the extraction of the information relevant to the involved atoms, from that due to neighbouring atoms on both sides of the selected interface seen end on by the impinging electrons. We have investigated possible ways to reach this goal, using the spectrum-line method, which consists in acquiring sequences of spectra at well defined increments (0.3 nm) while scanning a subnanometer electron probe (0.7 nm) across the interface. This approach constitutes one step forward with respect to the spatial-difference (SD) method which processes spectra acquired on two adjacent areas, one encompassing the interface, the other one on a reference area nearby. A normalized version (NSD) has been introduced to extend its field of application from grain boundaries to heterophase interfaces in order to enhance their specific ELNES contribution
TEM of nanodot arrays fabricated by direct laser interferometry
Authors: Liu Y , Zheng M , Yu M , Skomski R , Liou S H , Polushkin N I , Sellmyer D J
Published: July 2020

Patterned nanostructures and nanodots are attracting increasing interest in the information storage industry. The ultimate recording density of a magnetic medium will have single domain dots aligned in arrays and each dot in such an array acts as a recording bit. The ideal structure is that the dots are magnetic and the surrounding medium is non-magnetic so that each dot can switch magnetization direction freely without the interference from other dots. This paper presents the nanostructure of the nano-dot array investigated by transmission electron microscopy and magnetic force microscopy. The Co:C film was deposited by alternatively sputtering Co target and C target. The as-deposited specimen has an amorphous structure as revealed by electron diffraction in TEM. Such films transform to ferro-magnetic ones after heat treatment [1]. A laser beam of wavelength of 308 nm and a flux of 0.24 J/cm2 was split into two beams of an approximately equal intensity and then recombined, generating an interference pattern and a periodic modulation of the light intensity.