bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring rapid changes in near-membrane [Ca2+] using new membrane-associated Ca2+ indicators
Authors: Etter E. F. , Poenie M. , Minta A. , Fay F. S.
Published: June 2020

There are many cellular processes that take place across the cell membrane and that are regulated by Ca2+ just beneath the membrane. These include exocytosis in secretory cells and presynaptic neurons, control of K+ and Ca2+ permeability through membrane channels and activation of membrane-associated enzymes in many cell types. Indirect evidence suggests that during a physiological response, the concentration of Ca2+, ([Ca2+]) near the membrane may rise higher and change more rapidly than the [Ca2+] in the bulk cytosol. Gradients in intracellular [Ca2+] between the cell periphery and center during cell stimulation have been detected using Fura-2 and digital image microscopy or, with higher time and spatial resolution, using Fluo 3 and confocal microscopy, but these gradients are still much smaller than expected based on models of Ca2+ homeostasis and buffering in the cells studied. This suggests that in images obtained using soluble Ca2+ indicators, the fluorescence signal indicating rapid, large changes in [Ca2+] just beneath the cell membrane is obscured by the fluorescence signal from the rest of the cell where [Ca2+] changes are smaller or slower. Recently, Ca2+ indicators with a lipophilic tail which inserts into cell membranes have been developed to selectively monitor near-membrane [Ca2+].
Comparative ultrastructural study of camel, cow, and horse basophil
Authors: Hailat Nabil , Bataineh Ziad , Lafi Shawkat , Al-Bagdadi Fhakri
Published: June 2020

The ultrastructure of Arabian camel, cow, and horse basophils in peripheral blood was studied in order to provide detailed description of its constituents and to determine the similarities and the differences between these three species. Peripheral blood was taken from the three animals, centrifuged and the pellets were fixed in glutaraldehyde, dehydrated and embedded in Spurr's resin. Silver sections were mounted on copper grids and viewed by Zeiss electron microscope and microphotographs were taken. Camel's basophils were found to have smooth cell surface with small number of short pseudopodia (Figure 1). The horse' basophil had more longer pseudopodia while the cow's basophil had a large number of small ridges instead. The nucleus of the camel's basophil, similar to that of the horse' basophil, occupied almost 30% of the cytoplasm, while that of the cow's basophil, occupied larger area of the cytoplasm (Figure 1). The nucleus of the camel's basophil appeared irregular with marginated patchy chromatin and with abundant heterochromatin.
Mitochondrial distribution during oocyte maturation
Authors: Calarco P.
Published: June 2020

Maturation of an immature oocyte into one capable of being fertilized involves tightly choreographed movements of chromosomes and organelles. Although maturation has been described at the EM level, little information is available on the 3-dimensional distribution of organelles during maturation in living oocytes. Mouse oocyte maturation provides the best model system, and the present study describes the spatial distribution of mitochondria in live oocytes.

Immature oocytes were collected from ovaries in embryo culture medium containing IBMX 1/1000 (Sigma) to block maturation. Maturation, initiated by placing oocytes in IBMX-free medium, takes 12 hours at 37°C and 90% matured. Acridine orange (100 μM in medium, 10 min) was used to mark chromatin (data not shown). Mitochondria were labeled with rhodamine 123 (100 μM in medium; Molecular Probes, Oregon) which is cell permeant and accumulates in mitochondria. Live oocytes labeled for 1-2 hours, were rinsed, mounted in medium under oil and examined at various time points by the BioRad MRC-600 confocal laser scanning microscope (CLSM).
MAST cells in the dermis of rats repeatedly moistened with chloroform: An EM study
Authors: Abu-Ghalyun Y. , Shakhabneh J. , Al-Bagdadi F.
Published: June 2020

Mast cells are a free cell type, usually found in connective. The cells are common in the dermis and are abundant around blood vessels. Heterogeneity in the ultrastructure of mast cell has been documented. Variation of the morphology of the ultrastructure between the regional mast cells has been reported. Cellular relationships has been reported between mast cells and nerves, plasma cell, P neuropeptide and epithelial cells of uterine glands. The purpose of this study is to report the behaviour of mast cells in the dermis of rats repeatedly moistened with chloroform. Specimens were collected from the leg site of rats repeatedly moistened with chloroform, three times per day for three weeks. The collected specimens were immediately immersed in 2% glutaraldehyde in cacodylate sodium buffer at pH 7.4. Then the tissue was post fixed in 1% osmium tetroxide, dehydrated in ethyl alcohol, processed and embedded in Epon. One micron thick sections were stained with toluidine blue for orientation and silver sections were stained with lead citrate and urynal acetate.
Ultrastructural alterations of neuronal cells in gangliogliomas
Authors: Ho K.L. , Garcia J.H.
Published: June 2020

Gangliogliomas are uncommon glioma of the central nervous system, generally found in the temporal lobe of young individuals with a clinical history of seizures. The tumor is a mixed tumor composed of neoplastic mature ganglion cells and neoplastic glial cells, mostly astrocytes. Although the clinicopathological correlation of this tumor is well documented, few detailed ultrastructural studies have been reported.

We studied three cases of ganglioglioma of the temporal lobe and found several unusual ultrastructural features of the neuronal cells: (1) Hirano bodies (eosinophilic rod-like structure), highly organized eosinophilic crystalloid arrays of interlocking filaments that display lattice like configuration. Homogenous electron-dense material may appear as patches permeating the fibrillar structure (Fig. 1). (2) Lafora bodies (polyglucosan bodies), round to oval non-membrane-bound inclusion composed of short branching filaments about 7-10nm in diameter and granular structures (Fig. 2). (3) Pick's bodies, perikaryonal aggregates of straight neurofilaments with or without ribosome association mixed with vesicles, myelin figures and dense bodies.
Detection of spermatophagia in the ejaculate of infertile patients
Authors: de Gallegos L. G. , RamÍrez B. E. , Arce M. A. Y. , González S. D. , Rositas M. R. E.
Published: June 2020

Among the presently recognized factors related to reproductive anomalies in the human male, are the alterations of semen, mainly represented by defects in spermatic motility or asthenospermia . Autoinmune and infections could be responsible for a number of these cases . In both of these, a distinguishing factor is spermatophagocytosis, which may be unreckognizable in optic microscopy bat which is very apparent in electron microscopy.

To study the incidence of this event in cases of asthenoteratozoospermia, and its relation to infections and immune disorders, we studied a series of 60 infertile patients that presented motility defects and a control group of 5 volunteers of proven recent paternity. After 3 to 7 days of sexual abstinence, 1 or 2 semen samples were obtanied from each patient by masturbation. The samples were washed in phosphate buffered saline, double fixed in 2.5% glutaraldehide and 1% osmium tetraoxide and included in epoxi resin by the conventional method. Thick and thin sections were obtained whith a diamon knife and were examined microscopically. Electron micrographs of representative areas were analyzed.
An ultrastructural study of Nosema polyvora blunck infecting the malpighian tubules of Pieris canidia larva
Authors: Cheung W. W. K. , Wang J. B.
Published: June 2020

Microsporidian protozoans of Nosema spp. are common pathogens of insects in the orders Lepidoptera, Hymenoptera and Orthoptera. They are chronic pathogens that can be transmitted horizontally as well as vertically in susceptible insects. Thus they have the potential of being a microbial insecticide for suppressing insect pests populations. During the course of ultrastructural studies of the malpighian tubules of Pieris canidia we have found that Nosema polyvora Blunck commonly infects the tubules. It is worthwhile to investigate into the ultrastructure of this protozoan in order to better understand the host-parasite relationship.

Fourth instar larvae of P. candidia were dissected in phosphate buffered saline and malpighian tubules were isolated for fixation in 2.5% glutaraldehyde in 0.2M phosphate, pH 7.2, for 1 hr. Subsequently, tissues were post-fixed in 1% osmium tetroxide in phosphate buffer and were dehydrated in alcohol/acetone series. Tissues were finally embedded in spurr resin and were cut with a Reichart ultrotome. Sections were stained with uranyl acetate and lead citrate for observation under a Zeiss EM 9S-2 or JEOL JEM CX-II electron microscope.
Application of EM to differentiate herpes virus from pox virus in genital specimens
Authors: Rekrut K. , Schleuter K.
Published: June 2020

Confirmation of herpes simplex virus (HSV) from genital lesions of obstetrical (OB) patients may affect both the management of the delivery and of the neonate.(l,2) During 1992 and 1993, 4,450 genital specimens from OB patients were submitted in viral transport media for herpes culture. The specimens were inoculated into MRC-5, Vero, and A-549 tissue culture tubes, incubated, and examined daily for 7 days for cytopathic effect (CPE). The original specimens were frozen at −70° C until final reports were issued. Culture tubes with CPE were tested by the Dupont Herpchek enzyme immuno assay (EIA) to confirm the presence of herpes simplex virus (HSV). (3,4) 170 OB patient specimens were positive by culture and confirmed by EIA.

There were also 63 cultures exhibiting CPE ressembling HSV which were negative by EIA testing, which failed to pass in fresh tissue culture cells or progress to more enhanced CPE in culture. These original specimens were screened by electron microscopy after direct ultracentrifugation employing the Beckman airfuge with the EM 90 rotor on to formvar carbon-coated 300 mesh copper grids and negatively stained with 2% PTA.
Structural integrity after cold storage of human epidermal model in hypothermosol: A correlative ultrastructural and fluorescent assay
Authors: Eichelberger Henry H. , Baust John G. , Van Buskirk Robert G.
Published: June 2020

For research in cell differentiation and in vitro toxicology it is essential to provide a natural state of cell structure as a benchmark for interpreting results. Hypothermosol (Cryomedical Sciences, Rockville, MD) has proven useful in insuring the viability of synthetic human epidermis during cold-storage and in maintaining the epidermis’ ability to continue to differentiate following warming.

Human epidermal equivalent, EpiDerm (MatTek Corporation, Ashland, MA) consisting of fully differentiated stratified human epidermal cells were grown on a microporous membrane. EpiDerm samples were fixed before and after cold-storage (4°C) for 5 days in Hypothermosol or skin culture media (MatTek Corporation) and allowed to recover for 7 days at 37°C. EpiDerm samples were fixed 1 hour in 2.5% glutaraldehyde in sodium cacodylate buffer (pH 7.2). A secondary fixation with 0.2% ruthenium tetroxide (Polysciences, Inc., Warrington, PA) in sodium cacodylate was carried out for 3 hours at 4°C. Other samples were similarly fixed, but with 1% Osmium tetroxide in place of ruthenium tetroxide. Samples were dehydrated through a graded acetone series, infiltrated with Spurrs resin (Polysciences Inc.) and polymerized at 70°C.
In vitro assembly of 2-D crystals from partially purified EA1 protein secreted by Bacillus anthracis strain Delta Sterne-1
Authors: Downs Mary Beth , Ribot Wilson , Farchaus Joseph W.
Published: June 2020

Many bacteria possess surface layers (S-layers) that consist of a two-dimensional protein lattice external to the cell envelope. These S-layer arrays are usually composed of a single species of protein or glycoprotein and are not covalently linked to the underlying cell wall. When removed from the cell, S-layer proteins often reassemble into a lattice identical to that found on the cell, even without supporting cell wall fragments. S-layers exist at the interface between the cell and its environment and probably serve as molecular sieves that exclude destructive macromolecules while allowing passage of small nutrients and secreted proteins. Some S-layers are refractory to ingestion by macrophages and, generally, bacteria are more virulent when S-layers are present.

When grown in rich medium under aerobic conditions, B. anthracis strain Delta Sterne-1 secretes large amounts of a proteinaceous extractable antigen 1 (EA1) into the growth medium. Immunocytochemistry with rabbit polyclonal anti-EAl antibody made against the secreted protein and gold-conjugated goat anti-rabbit IgG showed that EAI was localized at the cell surface (fig 1), which suggests its role as an S-layer protein.
Detection of atrial natriuretic peptides (ANP) in rat atria by immunogold-silver staining (IGSS)
Authors: Rufner Robyn , Hacker Gerhard W. , Forte Michele , Carson Nancyleigh E. , Xenachis Cristina , Gu Jiang
Published: June 2020

The use of immunogold-silver staining (IGSS) to enhance label penetration and Localization for immunocytochemistry or in situ hybridization utilizing a variety of metallic salts has been documented. In this morphological study, the effects of silver acetate, silver lactate and silver nitrate were evaluated for immunogold-labeling of a trial natriuretic peptides (ANP) in rat right atria.

Eight Wistar Kyoto retired breeders were sedated with pentobarbital, perfused with either 4% paraformaldehyde (LM) or Karnovsky's fixative (EM), and right atria were dissected, processed, embedded in paraffin or epon, respectively and sectioned according to conventional methods. For light microscopy, an indirect IGSS method according to Hacker (3) was performed. Paraffin sections on glass slides were washed in ddH2O, immersed in Lugol's iodine, washed in ddH2O and treated with 2.5% aqueous sodium thiosulfate for 20 sec. After additional washes in ddH2O and TBS-0.1% fish gelatin, 10% normal goat serum (PBS with 1% BSA) was applied for 20 min before an overnight incubation at 4°C with a polyclonal α-ANP primary antibody (Peninsula Labs, 1:1000 in TBS/BSA).
Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography
Authors: Braunfeld M.B. , Moritz M. , Alberts B.M. , Sedat J.W. , Agard D.A.
Published: June 2020

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.

We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.

Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.
A rapid method for negative staining of fecal samples for diagnosis of viral-induced gastroenteritis by Transmission Electron Microscopy
Authors: Barrish J. P. , Hicks MJ , Leer LC , Hayes ES , Estes MK , Cubitt WD
Published: June 2020

The most common etiologic agents for viral gastroenteritis are rotavirus, adenovirus, and members of the “small round structure virus” category (enterovirus, norwalk virus, calicivirus, astrovirus). A rapid diagnosis of viral infection can avoid unnecessary antibiotic therapy, extensive and costly medical workups and reduce the patient’s hospital stay. Pseudoreplication has been the preparation method of choice at many institutions, because of its concentrating effect on viral particles. Unfortunately, in addition to concentrating viral particles, this method also concentrates fecal debris, making the screening process quite difficult at times and time consuming.

A rapid method of negative staining for viral particle identification in fecal samples is presented. The method first described by Cubitt et al has been modified, resulting in a reduction in the amount of debris and improved staining quality of the viral particles, while still concentrating the number of viral particles. This method requires less than 1 ml of stool specimen and may be prepared in less than three minutes.
Three-Dimensional reconstruction of protein bodies in developing maize endosperm using immunocytochemical techniques
Authors: Lending C. , Spinelli S.
Published: June 2020

The storage proteins of maize (Zea mays L.), like many other cereals, are a group of alcohol-soluble proteins classified as prolamines. In maize these proteins comprise four structurally distinct types and are termed zeins. Zein synthesis is initiated in developing maize endosperm and continues until the seed reaches maturity (between approximately 12 to 50 days after pollination). Zeins are synthesized by polysomes bound to the rough endoplasmic reticulum (RER) and they accumulate as insoluble aggregates called protein bodies. Our previous studies have shown that the zeins are deposited within protein bodies in a defined order in normal genotypes. However, the actual three-dimensional organization of the zeins within protein bodies and the interactions that occur between the various zeins is not known. Our goal is to understand protein body organization and the interactions that occur between the various proteins.

The four types of zeins are identified by their molecular weight after separation by SDS-PAGE, and are designated α-, β-, γ- and 6-zeins. The β-, γ-, and δ-zeins are all sulfur-rich proteins, while the α-zeins contain only low amounts of cysteine and methionine. These proteins can be individually detected by immunocytochemical staining of ultrathin sections. Additionally, ultrathin sections poststained with lead citrate and uranyl acetate demonstrate that there are two distinct regions that correlate with the immunocytochemical staining patterns.
An SEM and EDS study of secretions from the leaves of two halophytes
Authors: Naidoo Yougasphree , Gregory Michael A. , Naidoo Gonasagren
Published: June 2020

Salt glands are secretory organs that occur in several angiosperm families including the Plumbaginaceae and Poaceae. They are particularly prevalent on the leaves of plants growing in saline habitats where by the secretion of ions, they prevent toxic levels of salts from accumulating in their tissues. Whether different species of halophytes containing morphologically disparate glands preferentially secrete different cocktails of ions is not known. This question was addressed by employing SEM and EDS to determine the morphology and elemental constituents of crystalline deposits over the salt glands of two species of salt marsh halophytes: Limonium scabrum (Thunb.) Kuntze (Plumbaginaceae) and Sporobolus virginicus (L.) Kunth (Poaceae).

The two halophytes, collected from intertidal marshes and cultivated in a mixture of coarse sand and compost (3:1 by volume) were irrigated daily with tap water and fertilised every two weeks with full strength Hoagland’s nutrient solution. Plants were watered weekly for 3 months with 50 mol m−3 NaCl supplied as diluted sea water.
Scanning electron microscope study of brochosomes of cercopidae
Authors: Frost A. S. , Gardner J. S. , Nielson M.
Published: June 2020

Brochosomes are minute granules secreted by specialized cells lining the lumen of Malphigian tubules in homopteran insects. They have been reported on two different homopteran families, the Cicadellidae (leaf-hoppers) and Membracidae (tree-hoppers), but they have never been reported on members of the family Cercopidae (froghoppers), although they have been suspected to be produced by other homopteran families. These three families all belong to the subgroup Auchenorryncha, and often coexist in the same habitat. Many theories have been proposed regarding brochosome function, but no conclusive results have ever been reported.

Scanning electron microscopy was used to study legs of five species of Cercopidae. Brochosomes were observed on legs of Lepyronid batrachoidea (Fig. 1), Clastoptera brunnea (Fig. 2), Philaronia bilineata (Fig. 3), and Aphozphoza media (Fig. 4). None was found on Clastoptera juniperina. The shape of the brochosomes remained fairly consistent on all species except Clastoptera brunnea. Normally the structure was a polyhedron consisting of 12 pentagons and 20 hexagons, appearing hollow and nearly spherical. However, on Clastoptera brunnea, the brochosomes were larger and appeared to be more faceted.
Early ossicle growth in the regenerating disc of a brittle star
Authors: Shlepr M. , Turner R. L.
Published: June 2020

Calcification in the echinoderms occurs within a limited-volume cavity enclosed by cytoplasmic extensions of the mineral depositing cells, the sclerocytes. The current model of this process maintains that the sheath formed from these cytoplasmic extensions is syncytial. Prior studies indicate that syncytium formation might be dependent on sclerocyte density and not required for calcification. This model further envisions that ossicles formed de novo nucleate and grow intracellularly until the ossicle effectively outgrows the vacuole. Continued ossicle growth occurs within the sheath but external to the cell membrane. The initial intracellular location has been confirmed only for elements of the echinoid tooth.

The regenerating aboral disc integument of ophiophragmus filograneus was used to test the current echinoderm calcification model. This tissue is free of calcite fragments, thus avoiding questions of cellular engulfment, and ossicles are formed de novo. The tissue calcification pattern was followed by light microscopy in both living and fixed preparations.
Cytolysis caused by selenite uptake in the Bacillus subtilis
Authors: Yang W. H. , Yang J. R.
Published: June 2020

The toxic effects of selenium compounds on animals are well documented. However, the cytotoxic effects of these compounds are not well known. Using electron microscopy and atomic absorption spectrophotometry, we studied the effect of sodium selenite on the fine structure of Bacillus subtilis.

Bacteria were cultured with sodium selenite in LB broth at 38°C in a shaker culture system. At concentrations of selenite greater than 1mM, an inhibitory effect on bacterial growth was seen during the first few hours of culture. Using the atomic absorption assay, no uptake of selenite into bacteria during the lag phase was demonstrable. However, during the exponential growth phase, a marked increase in the selenium content of the cell pellet was measured along with a decrease in selenite in the supernatant (Figure 1). A reddish discoloration of the culture media was observed which corresponded with increasing selenite uptake by bacteria. After 24 hours in culture, an increase in particle density and viscosity of the culture media was measured which suggested fragmentation of the bacteria resulting in the release of DNA into the media.
Electron probe x-ray microanalysis with energy-dispersive x-ray spectrometry: The basics of x-ray spectrum interpretation
Authors: Newbury Dale E.
Published: June 2020

Electron probe x-ray microanalysis (EPMA) with energy dispersive x-ray spectrometry (EDS) provides the capability for detecting elements with atomic number ≥ 4 (beryllium) from an excited specimen volume with linear dimensions of micrometers and a mass in the picogram range. To maximize the utility of EPMA/EDS, the analyst needs to understand the rich source of information that is potentially available in the x-ray spectrum. At its most basic level, interpretation of the spectrum consists of recognizing and identifying the various components of the spectrum as recorded by the EDS system: characteristic peaks, artifacts, and continuum background. While a modern EDS system is capable of making this interpretation in an automatic fashion, the careful analyst will always check the computer’s interpretation, which of course demands that the analyst be at least as "smart" as the computer! A systematic examination of spectra from pure elements or simple compounds is a good way to develop the necessary working knowledge.
Automated linescan analysis in the electron microprobe
Authors: Spinnler G. E. , Christenson D. , Nielsen C. H.
Published: June 2020

Elemental linescan analysis in the electron microprobe (EMPA) or the SEM is useful for determining athe spatial distribution of elements. In many supported catalyst systems, the elemental distribution in pellets is important for their manufacture and performance. More important than determining the distribution of an individual pellet, is determining the distribution of many pellets in a sample to represent the lot. For this reason, multiple pellets must be analyzed. Various manufactures have systems that provide various degrees of automation for this type of analysis, however, there are no systems that allow complete unattended operation necessary to collect data on many samples.

The hardware consists of a JEOL JXM 8600 with four wavelength spectrometers, an EDX detector and a NORAN Voyager. Special software was written to completely automate the linescan procedure from finding the catalyst pellet to printing the report. This software combines the imaging and other analytical functions of the Voyager with a search and identify routine that locates the catalyst pellets and determines the positions of the linescan in accordance with predetermined criteria.
Crystal tectonics: Novel routes to the ordered aggregation and self assembly of inorganic solids
Authors: Heywood Brigid R.
Published: June 2020

Oriented materials attract considerable attention since thay have the potential to exhibit collective properties which exceed those of the isotropic species by several orders of magnitude. Much success has already been achieved with organic materials, e.g. liquid crystals, conducting polymers, but reliable protocols for the construction of organised crystal micro-architectures from inorganic solids have yet to be established. Given the potential advantages of translating molecular properties (optical, piezoelectric, catalytic) to the macroscopic scale strategies for the construction of hierarchical crystal assemblies, crystal tectonics, merit particular consideration.

This crystal tectonics route to the synthesis of anisotropic inorganic materials remains entirely untested, but draws much of its inspiration from the study of deterministic self-organisation in biological systems. Such self-organisation relies on a series of highly specific “host-guest”, ligandreceptor type interactions (more typically cited examples of such include, enzyme-substrate-cofactor binding, antibody-antigen complexation, and triplet/base matching during polypeptide synthesis). The biogenic formation of hierarchical inorganic arrays, biomineralization, is remarkable not only for its control of crystallisation to yield solids of uniform size and unusual habit, but equally for the construction of elaborate functional micro-architectures from these biosolids.
Digital image acquisition, processing, and analysis in a polymer microscopy laboratory
Authors: Berry Vinod K. , Zhang Xiao
Published: June 2020

In recent years it became apparent that we needed to improve productivity and efficiency in the Microscopy Laboratories in GE Plastics. It was realized that digital image acquisition, archiving, processing, analysis, and transmission over a network would be the best way to achieve this goal. Also, the capabilities of quantitative image analysis, image transmission etc. available with this approach would help us to increase our efficiency. Although the advantages of digital image acquisition, processing, archiving, etc. have been described and are being practiced in many SEM, laboratories, they have not been generally applied in microscopy laboratories (TEM, Optical, SEM and others) and impact on increased productivity has not been yet exploited as well.

In order to attain our objective we have acquired a SEMICAPS imaging workstation for each of the GE Plastic sites in the United States. We have integrated the workstation with the microscopes and their peripherals as shown in Figure 1.
Using the atomic-force microscope to measure roughness characteristics of acetabular prosthetic shells used as hip-socket replacements
Authors: Williams Gary. , Jani Shilesh , Marchese-Ragona Silvio P.
Published: June 2020

Total replacement of a diseased or traumatized hip joint is fast becoming one of the most common surgical procedures. The acetabular prosthetic shell is gaining widespread acceptance as a socket replacement for this procedure. Bio-materials research is providing a wealth of information regarding the life span, wear characteristics, and performance of these replacements, with a major clinical finding being the destruction of bone (osteolysis) at interfaces with the implants. Osteolysis is widely thought to be associated with the particulate wear debris released from articulation of the ball and socket. Formation and release of these particulates will depend not only on the relative motion occurring but also the surface roughness of the metal.

In this study we used the Atomic Force Microscope (AFM) to compare the internal surface topography of two acetabular shells, one polished to a mirror finish and the other unpolished. The ultimate goal of the study was to determine whether a polished shell reduces the amount of wear and tear on the ultra-high molecular weight polyethylene (UHMWPE) insert that is fitted between the shell and the Femoral ball (Figure 1).
Energy-dispersive x-ray spectroscopy: Escape peaks of some biomaterials in the light-element region
Authors: Okerstrom Susan J.
Published: June 2020

The phenomena of escape peaks is well known, but caution must be exercised to avoid confusion in peak identification. A summary of our experiences with certain escape peaks may be useful to others.

In biomedical devices, metal components are often used in pure elemental form or as alloys with high concentrations of a particular element. Noble metals such as gold, platinum and iridium are commonly used in pacemaker components. These metals are body compatible, have high corrosion resistance and are good electrical conductors. Pacemaker electrodes are commonly made of platinum, used alone or alloyed with about 10% iridium. These materials are routinely analyzed using the scanning electron microscope (SEM) with energy-dispersive x-ray spectroscopy (EDS).

While analyzing platinum electrodes at 20 keV with the Beryllium window open, it was noted that an unexpected peak was seen in the spectrum near where carbon would be expected at 0.310 keV. The same peak was noted when the Be window was closed (figure 1). It was first thought to be a detector problem.
Gas reaction chamber for gas-solid interaction studies by high-resolution TEM
Authors: Sharma Renu , Weiss Karl , McKelvy Michael , Glaunsinger William
Published: June 2020

An environmental cell (E-cell) is a gas reaction chamber mounted inside an electron microscope column where thin solid samples can be observed under various gases (O2, H2, N2, NH3etc.) at selected temperatures. Even though the idea of having an E-cell incorporated in the microscope column is as old as transmission electron microscopy itself, recent developments in the instrumentation and designs of both the microscopes and E-cells have made it possible to obtain high resolution images (0.3-0.6 nm). We have used the differentially pumped model proposed by Swan to modify a PHILLIPS 400T transmission electron microscope for gas-solid studies.

Figure la shows a side view cross section schematic of the E-cell fitted in the 9 mm gap between twin lens objective pole pieces. It consists of a small chamber with 200 and 400 μm apertures on sides a and a’ respectively. The walls are machined at the same angle as the pole pieces for an optimum fit to the conical exterior of the pole pieces and the cell is held firmly in place with o-rings (b).
Development of UHVTEM with UHV compatible goniometer and specimen-treatment chamber for surface studies
Authors: Kondo Y. , Kobayashi H. , Ishibashi Y. , Kasai T. , Nunome H. , Honda H. , Kersker M. , Ishida Y.
Published: June 2020

JEOL has previously been involved in the development of various ultrahigh vacuum transmission electron microscopes (UHVTEM). Interest in UHVTEM is increasing, and for higher vacuum, higher resolution and specimen treatment capability, we have developed a new type of UHVTEM, the JEM- 2000FXVII. This paper reports the construction and performance of this new UHVTEM including a newly developed UHV compatible goniometer, specimen treatment chamber and various types of specimen heating holders.

Figure 1 shows the overview of the JEM-2000FXVII with a specimen pre-treatment chamber (PTC) and UHV compatible goniometer. The PTC consists of two chambers: one for specimen treatment and the other for pre-evacuation. Specimen treatment is accomplished by using any of 7 attachment ports (six 70ϕ ICFs and a 152ϕ ICFs) in the PTC (Fig. 2). The PTC is attached directly to the TEM column and quick exchange of the specimen from PTC to column is thus possible. In-situ observation is also possible using the three attachment ports (70ϕ ICFs) in the column.
Stabilising a Peels spectrometer
Authors: McMullan D.
Published: June 2020

The resolution of a parallel recording electron energy loss spectrometer (PEELS) depends critically on the stabilities of the power supplies to the microscope column and the spectrometer over the period of the exposure. They may be the limiting factor in a dedicated scanning transmission electron microscope (STEM) with a field-emission electron gun (FEG), and improving them so that they are sufficiently stable can be a difficult task.

An alternative approach is to compensate for any drift by deflecting the electron image of the spectrum leaving the spectrometer. The amount of deflection is that required to keep the zero-loss peak at a fixed position relative to the recording system. Such a stabiliser is being developed in the Microstructural Physics (MP) Group at the Cavendish Laboratory and a progress report is given here.

The MP STEM is a VG Microscopes HB501 fitted with an Isaacson electron spectrometer. The normal accelerating potential is 100 kV and the FEG has an electron energy spread of about 0.25 eV. The spectrometer gives a dispersion of 1.8 pm per eV at the slit and from the evidence of very short exposures its resolution is adequate to match the FEG energy-spread in the absence of drift. A PEELS system with 3 quadrupoles and a YAG + CCD detector has been added, but the slit has been retained.
HREM image simulation of Ti5Si3TiC/6H-SiC interfaces
Authors: Bow J. S. , Carpenter R. W. , Kim M.J.
Published: June 2020

Researches on interfacial structures by experimental HREM and computer simulation to the present have concentrated on solving one interface between two phases. Interfaces with a thin third phase interlayer between two major phases are of more recent interest. As the thickness of the interlayer phasedecreases, the strain fields of the bounding interfaces are no longer completely accommodated by the interlayer phase. The structures of both interfaces have to be considered simultaneously. This abstract describes some early work on establishment of a supercell including three phases and two interfaces for HREM simulation.

The interface triad, Ti5Si3/TiC/6H-SiC, which was formed during annealing Ti/6H-SiC contacts, is an important example. The TiC thickness observed in the experimental HREM image, Fig. 1, is about 2.5 nm. The interlayer dimension normal to the interfaces is not large, and the size of the required supercell is small enough for computation on a moderately fast workstation.

The simplest way to build a supercell including these three phases is to build each individual crystal constituent of the triad in the desired orientation and dimension and then assemble them with suitable translation vectors.
Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings
Authors: Kung H. , Jervis T. R. , Hirvonen J.-P. , Nastasi M. , Mitchell T. E. , Embury J. D.
Published: June 2020

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.

Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.
Structural-property relations in ferroelectric-based materials
Authors: Randall C. A.
Published: June 2020

Ferroelectric and related materials are gaining importance owing to the wide variety of phenomena associated with ferroelectricity. This includes high dielectric permittivity, electrostriction, pyroelectricity, and piezoelectricity. Applications using these properties are continually requiring higher performance of the materials. Therefore, there exists a need to understand the structuralproperty relations of ferroelectrics as a means to optimize their design.

Transmission electron microscopy (TEM) techniques are beginning to provide quantitative and qualitative information on the mesoscopic structures, local crystallography, and chemistry of ferroelectric materials. This paper will consider three examples in which TEM methods have been successfully used to prepare higher performance materials and/or a deeper understanding of the role of mesoscopic structures on the physical dielectric characteristics.

The first example demonstrates the importance of intermediate scale B-site chemical ordering within the complex lead perovskite lattice and the associated observation of relaxor behavior. Figure 1 shows a typical dark field electron micrograph of B-site order domains in Pb(Mg1/3Nb2/3)O3.
Determination of crystal polarity in the Electron Microscope
Authors: Mader W. , Recnik A.
Published: June 2020

A few methods were proposed for the determination of crystal polarity using electron diffraction. The method by Taftø and Spence is based on the coupling between ZOLZ and FOLZ reflections, requiring exact tilting to excite weak high- and odd-indexed reflections. The method by Spellward and James relies on the comparison of experimentally observed and calculated CBED patterns of fairly thick crystals, where the features in the CBED discs are compared. In this paper we present a method for polarity determination readily evident from ZOLZ reflections in zone-axis microdiffraction patterns. The method is based on zero-layer interactions from thin crystals with thickness t smaller than the extinction length of the primary beam. Then the diffraction discs appear homogeneous, and the breakdown of Friedel's law is noticable in a difference of the intensities of the reflections g and -g which are not related to a mirror plane (Bijvoet-related reflections).

The method can be applied using any transmission electron microscope which is designed for obtaining convergent-beam microdiffraction patterns and in principle, specimen-cooling is not necessary. The crystals have to be oriented to a low-indexed zone axis, where the diffraction plane contains a polar crystal axis.
Orientation imaging of microstructures
Authors: Adams B. L.
Published: June 2020

The complexity of microstructures characteristic of polycrystalline materials presents the serious investigator with many challenges. The materials engineer hopes to associate the important technological properties of these materials with specific (quantifiable) attributes of the microstructure; however, microscopy presents an overwhelming myriad of details over a wide range of scales of inquiry. Thus, the persistent question becomes: What is important in the microstructure relative to a specific property or aspect of material performance? One particular viewpoint, which stems from the modern atomistic interpretation of the structure of solids, is that for polycrystalline materials it is the spatial placement of lattice orientation that is of essential interest.

The past decade has seen some remarkable progress in microdiffraction technique in conjunction with the scanning electron microscope. This progress now makes it possible to vigorously pursue the aforementioned lattice-orientational viewpoint. Since 1987 modern SIT (silicon intensified target) vidicon and CCD (charge-coupled device) cameras have been used to capture the backscattered Kikuchi diffraction (BKD) formed in stationary spot mode in the scanning electron microscope.
BKD in the SEM: Toward a smaller information volume
Authors: Troost K. , Kamminga J.-D.
Published: June 2020

Upto now, the recording of backscatter Kikuchi diffraction (BKD) patterns (also called electron backscattering patterns, EBSP) for microscale texture analysis is mostly performed at high primary beam voltages U > 20 kV using an SEM with a tungsten or LaB6 electron gun. Under these circumstances, a lateral resolution of 0.2-0.5 μm has been reported. However, the texture analysis of fine-grained bulk materials or vacuum-deposited thin metallic layers as used in the IC-industry requires a higher spatial resolution. A fieldemission electron gun (FEG) with a much higher electron-optical brightness can deliver the 1-nA beam current needed for EBSP recording in a spot of about 10 nm, enabling a lateral resolution of 20×80 nm3 and an information depth of 10 nm at 20 kV. In Ref. 2, the possibility of using lower beam voltages to obtain an even higher resolution is mentioned. Monte Carlo simulations indeed show that the interaction volume decreases at least linearly with decreasing U.
Applications of microtexture analysis for materials characterization using SEM and TEM techniques
Authors: Weiland H. , Liu J.
Published: June 2020

Research and development in material science require the understanding of structure and property relationship. In many instances, such a relationship at a local microstructural scale is crucial for a mechanistic insight. Spatially-resolved microtexture analyses based on both scanning and transmission electron microscopy have now become powerful tools for these studies. By these techniques, not only can a linkage be established between morphological and crystallographic components of the microstructure, grain boundary details can be obtained as well. The choice of the SEM- or TEM-based microtexture technique for a study, however, depends on the specific needs. Several industrial examples of applied and basic work will be used for illustration.

Industrial deformation processes such as extrusion, rolling and forging are generally inhomogeneous. As a result, strain gradients, and consequently, microstructure gradients, are intrinsic to most industrial products. For example, a laboratory-produced plane strain extrusion of an Al-Zn-Mg-Cu alloy exhibits a range of complex grain structures (Fig. 1a).
Characterization of SiC fiber-reinforced SiC composites by TEM
Authors: Park K. , Sung C.
Published: June 2020

SiC fiber-reinforced SiC composites have been accepted to have considerable potential as an engineering structural ceramic for numerous high-temperature applications, such as various heat engine components. In this study, the microstructure of matrix, fiber, and matrix/fiber interface of SiC fiber (SCS-6, Textron)-reinforced nitrogen-treated SiC composites was characterized using transmission electron microscopy (TEM). Cross-sectional TEM samples were prepared by mechanical grinding, dimpling, and ion-milling. The samples were analyzed using a Philips EM400T TEM and a Noran ultrathin window Micro-Z detector.

The α-Si3N4 was formed in the porous SiC matrix by nitriding (Fig. 1(a)). The porous SiC matrix can permit easy and continuous penetration of the nitriding gas and rapid escape of the reaction and volatilization products, thus favoring vapor-phase reactions. In the case of huge SiC grains, the α-Si3N4 was formed at the surface of the huge SiC grains. Rod-shaped Si2N2O phase was often observed in the porous matrix. Figs. 1(b), (c), and (d) show electron diffraction patterns obtained from the α-SiC, α-Si3N4, Si2N2O phases, respectively.
Microstructure of intermetallic-matrix composites produced in situ by self-propagating high-temperature synthesis
Authors: Doğan C. P. , Alman D. E.
Published: June 2020

Self-propagating, high-temperature synthesis (SHS) is one method of material production in which elemental constituents are ignited, initiating a self-sustaining, exothermic reaction that results in their transformation into intermetallic and ceramic compounds. In addition, several reactions can be initiated within a single body to form intermetallic-intermetallic, intermetallic-ceramic, or ceramic-ceramic composites in situ. The driving force for the reactions is the negative heats of mixing of the forming compounds, which results in the liberation of heat. The obvious advantages of SHS processing are that it presents an opportunity to produce near net-shape advanced materials and composites with a high level of purity in a relatively low-cost and energy efficient manner.

At the U.S. Bureau of Mines, we are actively involved in the SHS processing of a wide range of singlephase intermetallic and intermetallic-matrix composites: TiAl, TiAl+TiB2, TiAl+TiC, TiAl+Ti5Si3, MoSi2+SiC. One key element of our study is a thorough understanding of the effect of processing variables, such as composition, temperature, pressure, time, powder morphology, etc., on the microstructure, and hence the properties, of these materials.
Toward quantitative defect analysis using HREM
Authors: Smith David J.
Published: June 2020

The electron microscope has evolved to the level where it is now straightforward to record highresolution images from thin samples (t∼10 to 20nm) that are directly interpretable in terms of atomic arrangements. Whilst recorded images necessarily represent two-dimensional projections of the structure, many defects such as dislocations and interfaces may be linear or planar in nature and thus might be expected to be amenable to detailed characterization. In this review, we briefly consider the recent significant progress that has been made in quantitative defect analysis using the high-resolution electron microscope and then discuss some drawbacks to the technique as well as potential scope for further improvements. Surveys of defect modelling for some small-unit-cell materials and interfaces have recently been published, and reference should be made to other papers in this symposium for further examples.

The technique of structure imaging originated in the early '70s with observations of large-unit-cell block oxides.