bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of manual and morphometric analysis techniques for rat hepatocyte peroxisomes
Authors: Ellzey J. T. , Stevens T. L. , Borunda D. , Dominguez D. C.
Published: June 2020

It has been well documented that ethanol is toxic to hepatocytes and that peroxisomes are key organelles in the metabolism of ethanol. Lieber (1985) has confirmed that when rats are fed a 30% ethanol-derived calories diet for three weeks there are noticeable ultrastructural changes such as the accumulation of lipid (steatosis) and the hypertrophy of the smooth endoplasmic reticulum. We sought an efficient costeffective technique for obtaining reliable quantitative documentation of subtle changes within organelles of hepatocytes after rats were fed a 30% ethanol-derived calories diet for two weeks. One hundred micrographs of match paired ethanol-fed rats (n = 5) were compared with 100 micrographs of controls (n = 5) and analyzed by the point counting method; with a digital planimeter using SigmaScan/Image software (Jandel Inc.) and calculations were made using Excel v. 4.0 (Microsoft Corp.); as well as with Optimas image analysis software (Bioscan). Micrographs were taken with a Zeiss EM 10 transmission electron microscope.
Visualization of transcytosis in MDCK cells using laser scanning confocal microscopy
Authors: Martin Greg , Cariappa Rohit , Hubbard Ann L.
Published: June 2020

The plasma membrane of polarized epithelial cells is composed of two structurally and functionally distinct domains -- the apical and basolateral -- that also differ in molecular composition. The routes followed by integral membrane proteins from their site of synthesis to their site of function varies between different kinds of epithelia. Madin-Darby canine kidney (MDCK) cells deliver plasma membrane proteins directly to the correct domain, while polarized hepatocytes deliver all newly synthesized plasma membrane proteins initially to the basolateral membrane, then retrieve and redirect the apical membrane proteins. We are studying the targeting signals and delivery routes of DPPIV, a single transmembrane protein whose destination is the apical domain in polarized epithelial cells.

DPPIV transfected into MDCK cells is delivered to the basolateral plasma membrane after long (13hr) treatment with Brefeldin A (BFA). After BFA’s removal these molecules are retrieved from the basolateral membrane and transcytosed to the apical plasma membrane. This protocol provides a useful model for studies of the indirect route of protein sorting in polarized epithelial cells, since DPPIV at the basolateral surface can be labeled with specific antibody and then subsequently followed in living cells.
Relevancy of electron microscopy in the study of male factor in conjugal infertility
Authors: Gallegos M.G. , Ramírez E. , Eguia R.M. , González D. , Díaz O.
Published: June 2020

In recent years, the study of male factor in conjugal infertility, has received more attention since it was recognized as an important cause of infertility in 30-50% of the cases; and to the diminishing quality of semen, observed during the last decades, possibly related to environmental polution.

Alterations in sperm motility has been included as a direct cause of male infertility along with the traditionally known causes. Frequently these alterations have been related to morphological changes of spermatozoa. The morphology and size of sperm cells are higly variable in human semen and abnormal forms also can be found in fertile men. Experimental data demonstrate that abnormal spermatozoa are not functional cells. There are many clinical reports that associate spermatic dismorphy with infertility. Previously reported abnormalities in the sperm morphology related to infertility include: acrosomal agenesis, defects in the dynein arms and fibrous sheath displasia. Therefore, it is important to undertake the ultrastructural study of spermatozoa to determine subcellular pathology of the gamete which could explain the reproductive failure, specially if there is no evident cause of the motility defect or if there has been no response to treatment, or if the assisted reproductive programs have failed repeatedly.
Ultrastructural characterization of acute lymphoblastic leukaemia in children in Irbid, Jordan
Authors: Al-Rimawi H. , Al-Bagdadi F. , Hailat N.
Published: June 2020

A formal scheme for the characterization of acute leukaemia on light microscopic morphological adaptation (FAB) has been proposed by a group of French, American and British haematologists. Acute leukaemia has been reported with unclassifiable morphology and undifferentiated cytochemistry by FAB. The application of the light microscope for cellular diagnosis is not very reliable, due to the fact that the key predominant cell being sought for the diagnosis is poorly differentiated. However, we do agree that cellular differentiation by light microscopy, which is solely based on morphological criteria as a diagnosis evidence is often lacks accuracy. This statement is clear indication of the light microscopic limitation, to identify the morphological changes in comparison with the electron microscope. We suggest electron microscopic conformation might be necessary for light microscopic diagnosis. Five patients 5-12 years old were clinically suspected as leukaemia, were presented to Princess Basmah Teaching Hospital paediatric section for diagnosis. FAB classification which is based on morphological and biochemical criteria was used for diagnosis through bone marrow aspiration.
Subcellular localization of the latent membrane protein LMP-1 in Epstein-Barr virus infected cells by immunogold EM
Authors: Misra D. N. , Agostini R. M. , Yunis E. J.
Published: June 2020

Epstein-Barr virus (EBV) infection, prevalent in all human populations, is clinically silent in general, but causes infectious mononucleosis in some adolescents and B-lymphocyte proliferative disorders (LPDs) in immunocompromised individuals (e.g. AIDS infected; allograft recipients). EBV is also etiologically associated with African Burkitt’s lymphoma, nasopharyngeal carcinoma, and Hodgkin’s disease. The virus infects B lymphocytes and transforms them into lymphoblastoid cells which proliferate indefinitely in culture. The latently infected cells express an array of EBV gene products including 6 nuclear antigens (EBNAs), terminal proteins LMP-2A and LMP-2B, latent membrane protein LMP-1, and untranslated RNAs EBER 1 and EBER 2. These components are being extensively studied since they are involved in latency or proliferative transformation; LMP-1 has also shown oncogenic properties. In this work, we have used immunogold electron microscopy for precise subcellular localization of LMP-1 in EBV infected cell lines.

Two human cell lines, P3HR-1 (Burkitt’s lymphoma) and CCL-113 (Hodgkin’s disease), obtained from ATCC, were grown in RPMI 1640 containing 20% fetal calf serum, 100 U/ml penicillin and 100 μg/ml streptomycin.
Juvenile nephronophthisis: A case report
Authors: Price George , Cerezo Lizard , Pryor Norman
Published: June 2020

Nephronophthisis, or the deterioration of nephrons, is a classification of congenital kidney disorder that results in a medullary cystic disease. The three variations of genetic expression for this disease are: 1. Sporadic occurrences where family history is negative for renal disease. 2. Recessive inheritance with or without other associated abnormalities. 3. Transmitted inheritance that is dominant with probable autosomal, and possible X-linked trait.

Nephronophthisis is reported to occur between the ages of 2 to 68 years of age, with most appearing in the first three decades of life. The most common clinical presentation is chronic renal failure, with a history of polyuria, and polydipsia. Children and adolescents may also exhibit enuresis, and chronic anemia.

Light microscopic examination of kidney biopsy tissue reveals extensive tubular atrophy accompanied by glomerular sclerosis, and inflammation resembling pyelonephritis. Tubules that are cystically dilated may be observed primarily at the cortico-medullary junction, although this finding is dependent on the extent of the disease process.
Ultrastructural study of skeletal muscle invasion by a malignant fibrous histiocytoma
Authors: Finol H. J. , Márquez A. , Bello B. , Rivera H.
Published: June 2020

Cancer grows by progressive invasion, infiltration and destruction of tissues surrounding primary tumors or their metastases. Although this process has been amply investigated, it has not been adequately studied by means of electron microscopy and scarce information exists about its morphological aspects; Because of these reasons, we studied the ultrastructure of skeletal muscle invasion by a malignant fibrous histiocytoma as an example of the cancer growing process.

Biopsies were obtained from a mass located intramuscularly in the left thigh of a 70 years old male patient. Samples were taken from the tumor and the surrounding muscle tissue. The specimens were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.

The histopathological picture of the tumor fell within the spectrum for malignant fibrous histiocytoma. The borderline zone between tumor cells and muscle tissue was carefully examined. Tumor cells were located in the extracellular space. Muscle fibers were not found invaded but those beside tumor cells exhibited several alterations including atrophy (Fig. 1) and vacuolation (Fig. 3).
Utilization of scanning Electron Microscopy/Energy-Dispersive x-ray microanalysis to detect an immunogold labeled virus on a Transmission Electron Microscope thin sectioned sample
Authors: Helmick C. M. , Bailey J. F. , Ristow S. S.
Published: June 2020

Since not all research facilities have access to a transmission electron microscope (TEM) / x-ray microanalysis system, a study was conducted to determine if a scanning electron microscope (SEM) equipped with an energy dispersive x-ray microanalyer would detect and quantify an immunogold labeled virus on a TEM thin sectioned sample. The objectives of the study were to first, demonstrate that a particular region (serous cardiac gland) of a thin sectioned fish esophageal tissue sample could be detected on a SEM. Secondly, we sought to demonstrate that the quantities of colloidal gold x-rays emitted were in association with the viral infected esophageal tissue at 1 and 24 hours post infection.

Tissue and Immunogold labeling. Juvenile rainbow trout (Oncorhychus mykiss) were challenged in vivo at 105 pfu with Hagerman infectious hematopoietic necrosis virus (IHNV) or mocked infected with phosphate buffered saline (PBS). Fish were killed and fixed in 6% paraformaldehyde and 0.5% glutaraldehyde in 0.1 M PBS at 1 and 24 hours post infection and stored at 4°C.
Three-Dimensional Reconstruction reconstruction of A Z band from rigor skeletal muscle
Authors: Schroeter J.P. , Edwards R.J. , Goldstein M. A.
Published: June 2020

We have produced three dimensional reconstructions of several regions of the Z band and the nearby I band in rat soleus muscle in rigor. The reconstructions were calculated using weighted back-projection techniques on electron micrograph tilt series taken about two orthogonal axes. Examination of cross-sections of the reconstructed Z bands reveal that the lattice is in the basket-weave form. We have previously shown that this form of the Z band lattice predominates in the muscle in rigor. The reconstructions reveal a dense net of cross-connecting Z-filaments in the Z band, which interconnect the axial filaments in a projected four-fold array.

The Z band lattice spacing was measured as 27 +− 4 nm, consistent with values seen in electron micrographs of cross sections of this muscle. The Z spacing and the form of the lattice show little distortion from that observed in cross sections, despite a beam induced change in section thickness from ∼80 to 45 nm. This suggests that, as in previous Z band reconstructions in unstimulated muscle, section shrinkage in the Z band does not occur by means of a uniform collapse throughout the section.
Quick large-piece diagnostic electron microscopy processing
Authors: Valdivieso Teresa P. , Valaitis Jonas
Published: June 2020

In the past submissions of tissue (fine needle biopsies of kidney, liver, incisional biopsies, tumors and miscellaneous other biopsies) for transmission electron microscopy examination were small, i.e. no larger than 1mm cubed (1,2). With such submissions, from the time the specimen was received in the electron microscopy laboratory until photographic prints were available and a diagnosis reported by the pathologist was 72 hrs. A modification of the standard procedure allows the processing of larger and thinner pieces of tissue up to 5mm × 3mm × .5mm and shortens the turn-around time from 72 hrs to 24 hrs.

Large pieces of tissue are processed according to the procedure detailed below. All the usual steps are abbreviated: Primary fixation and post-fixation: 5 hrs; dehydration: 20 min; infiltration in epoxy resins: 1 hr and 25 min; embedding and orientation of specimens: 15 min; polymerization: 60 min; cutting thick and thin sections: 50% fewer blocks in comparison to previous procedure; staining in heavy metals: no change.
Ultrastructure of metaphase chromosomes and interphase nuclei
Authors: Woods Philip S. , Ledbetter Myron C. , Van't Hof Jack
Published: June 2020

Electron microscopy of whole-mount preparations of chromosomes and nuclei was greatly improved upon over earlier studies, when techniques were developed to expand the specimen and to preserve the expanded state during drying. When the earlier procedures were followed, the thick and dense chromosomes and nuclei always appeared nearly opaque to the electron beam and yielded little information regarding internal structure. With the newer techniques, it has been possible to study structure in detail deep within these specimens. The chromosomes of the plant Vicia faba are composed of a very long thin (5-20 nm) fiber which consists of about 38% DNA, with a presumed equal amount of histones; and a thicker 15-55 nm net-like component consisting of the remaining 24%, as nonhistones. Our interests concern determining the structural relationship of these components in chromosomes and nuclei of root-tip cells of this same plant.

Fig. 1 shows a Vicia faba metaphase chromosome expanded with EDTA and processed by freeze-substitution. Inset, at the same magnification, shows an untreated similarly processed control chromosome.
Basic literacy in electron-probe x-ray microanalysis with energy-dispersive x-ray spectrometry: Qualitative and quantitative analysis
Authors: Newbury Dale E.
Published: June 2020

Rigorous electron probe x-ray microanalysis (EPMA) with energy dispersive x-ray spectrometry (EDS) takes place in two sequential steps: qualitative analysis followed by quantitative analysis.

Qualitative analysis: Qualitative analysis involves the assignment of the peaks found in the x-ray spectrum to specific elements. One of the most important attributes of energy dispersive x-ray spectrometry (EDS) for qualitative analysis is that we can always view the complete x-ray spectrum. The EDS photon detection process effectively provides parallel detection in energy. Depending on the detector window and spectrometer characteristics, the entire energy range from Be K radiation (0.106 keV) to the incident beam energy can be available for analysis. With an incident beam energy of 15 keV, at least one family of x-ray lines (K, L, or M shell) will be excited for each element in the Periodic Table with atomic number ≥ 4. We ignore at our peril this capability to do a complete qualitative analysis at all specimen locations that we choose to measure. Quantitative analysis is meaningless if qualitative analysis has not been properly perfonned first. The bases for qualitative analysis include the exact energy of the peak(s), which places a premium on spectrometer calibration, the recognition of all members of each x-ray family and the possibility of two (or more) families being excited, the relative intensities ("weights of lines") within a family, and the artifacts associated with each high intensity peak, particularly the escape peak(s) and sum peak(s).
Immunoelectron microscopy of frozen hydrated blood platelets
Authors: O’Toole E. T.
Published: June 2020

We have previously shown that ultrarapid freezing followed by cryomicroscopy provides a uniquely effective preservation of platelet ultrastructure, particularly in its cytoskeleton and membrane systems. However, a limitation of cryomicroscopy of frozen hydrated specimens is the lack of information about the localization of specific proteins within the cell. Methods for immunolocalization of antigens on material that has been rapidly frozen, freeze-substituted and embedded in immunocompatible resins have excited considerable interest among biologists, because of the high quality of preservation afforded by fast-freezing techniques. However, the extent to which fixation and dehydration affect the distribution of antigens is not known. Here we describe a method for imaging immunolabeled cells in the frozen hydrated state, avoiding the destructive steps of dehydration.

Blood platelets were isolated from citrated whole blood by differential centrifugation and washed in Hank’s balanced salts. Washed platelet suspensions were placed on formvar coated, carbon stabilized gold finder grids and placed in a humid chamber at 37°C for 30 minutes to allow adhesion and spreading of the cells.
A basic introduction to image processing using NIH-Image as a model
Authors: Mansfield John
Published: June 2020

Advances in camera technology and digital instrument control have meant that in modern microscopy, the image that was, in the past, typically recorded on a piece of film is now recorded directly into a computer. The transfer of the analog image seen in the microscope to the digitized picture in the computer does not mean, however, that the problems associated with recording images, analyzing them, and preparing them for publication, have all miraculously been solved. The steps involved in the recording an image to film remain largely intact in the digital world. The image is recorded, prepared for measurement in some way, analyzed, and then prepared for presentation.

Digital image acquisition schemes are largely the realm of the microscope manufacturers, however, there are also a multitude of “homemade” acquisition systems in microscope laboratories around the world. It is not the mission of this tutorial to deal with the various acquisition systems, but rather to introduce the novice user to rudimentary image processing and measurement.
Optimizing detector resolution and efficiency in CCD arrays
Authors: Joy David C. , Allard Lawrence F.
Published: June 2020

The effective use of a CCD camera to record TEM images requires the use of a scintillator to convert the energy of the incident electrons into light. In order to record the image with the highest resolution possible from the given CCD array we require that the broadening of the electron beam that occurs as it travels through the scintillator be less than, or comparable to, the diameter of the pixel. Beam spreading that is greater than the pixel size not only reduces the line-pair resolution, but also causes correlation between adjacent pixels which may result in the measured detector quantum efficiency (DQE) apparently exceeding unity. At the same time we need the electron to transfer the maximum possible amount of energy to the scintillator since the intensity of the signal produced by the CCD array depends directly on the energy deposited. Clearly these two requirements are mutually opposed since the conditions which minimize the beam spreading will also likely be the conditions under which the least energy is transferred.
Quantitative Electron Microscope with imaging plate
Authors: Shindo D.
Published: June 2020

Imaging plate has good properties, i.e., a wide dynamic range and good linearity for the electron intensity. Thus the digital data (2048x1536 pixels, 4096 gray levels in log scale) obtained with the imaging plate can be used for quantification in electron microscopy. By using the image processing system (PIXsysTEM) combined with a main frame (ACOS3900), quantitative analysis of electron diffraction patterns and high-resolution electron microscope (HREM) images has been successfully carried out.

In the analysis of HREM images observed with the imaging plate, quantitative comparison between observed intensity and calculated intensity can be carried out by taking into account the experimental parameters such as crystal thickness and defocus value. An example of HREM images of quenched Tl2Ba2Cu1Oy (Tc = 70K) observed with the imaging plate is shown in Figs. 1(b) - (d) comparing with a structure model proposed by x-ray diffraction study of Fig. 1 (a). The image was observed with a JEM-4000EX electron microscope (Cs =1.0 mm).
Slow-scan CCD cameras and low-dose High-Resolution Electron Microscopy: Direct and quantitative
Authors: Pan M.
Published: June 2020

It has been known for many years that materials such as zeolites, polymers, and biological specimens have crystalline structures that are vulnerable to electron beam irradiation. This radiation damage severely restrains the use of high resolution electron microscopy (HREM). As a result, structural characterization of these materials using HREM techniques becomes difficult and challenging. The emergence of slow-scan CCD cameras in recent years has made it possible to record high resolution (∽2Å) structural images with low beam intensity before any apparent structural damage occurs. Among the many ideal properties of slow-scan CCD cameras, the low readout noise and digital recording allow for low-dose HREM to be carried out in an efficient and quantitative way. For example, the image quality (or resolution) can be readily evaluated on-line at the microscope and this information can then be used to optimize the operating conditions, thus ensuring that high quality images are recorded. Since slow-scan CCD cameras output (undistorted) digital data within the large dynamic range (103-104), they are ideal for quantitative electron diffraction and microscopy.
EMCAT: An automatic image-processing system for electron-microscopic tomography
Authors: Liu Weiping , Sedat John W. , Agard David A.
Published: June 2020

Any real world object is three-dimensional. The principle of tomography, which reconstructs the 3-D structure of an object from its 2-D projections of different view angles has found application in many disciplines. Electron Microscopic (EM) tomography on non-ordered structures (e.g., subcellular structures in biology and non-crystalline structures in material science) has been exercised sporadically in the last twenty years or so. As vital as is the 3-D structural information and with no existing alternative 3-D imaging technique to compete in its high resolution range, the technique to date remains the kingdom of a brave few. Its tedious tasks have been preventing it from being a routine tool. One keyword in promoting its popularity is automation: The data collection has been automated in our lab, which can routinely yield a data set of over 100 projections in the matter of a few hours. Now the image processing part is also automated. Such automations finish the job easier, faster and better.
Convergent-beam thickness determination: The advantages of digital imaging
Authors: McKernan Stuart , Carter C. Barry
Published: June 2020

Convergent-beam electron diffraction (CBED) patterns contain an immense amount of information relating to the structure of the material from which they are obtained. The analysis of these patterns has progressed to the point that under appropriate, well specified conditions, the intensity variation within the CBED discs may be understood in a quantitative sense. Rossouw et al for example, have produced numerical simulations of zone-axis CBED patterns which show remarkable agreement with experimental patterns. Spence and co-workers have obtained the structure factor parameters for lowindex reflections using the intensity variation in 2-beam CBED patterns. Both of these examples involve the use of digital data. Perhaps the most frequent use for quantitative CBED analysis is the thickness determination described by Kelly et al. This analysis has been implemented in a variety of different ways; from real-time, in-situ analysis using the microscope controls, to measurements of photographic prints with a ruler, to automated processing of digitally acquired images. The potential advantages of this latter process will be presented.
Off-axis electron holography of a two-phase polymer
Authors: Libera M. , Gajdardziska-Josifovska M. , Disko M. M.
Published: June 2020

Electron holography enables retrieval of phase from an image wave. This phase information is lost in conventional microscopy. As part of an ongoing program to study polymer microstructure via phase-contrast imaging, we report here our first experiences applying off-axis holography to polymers.

This study utilized a 48k mw styrene/butadiene diblock copolymer mixed with 30% 25k mw styrene homopolymer. The specimen was cast from toluene, annealed, cryomicrotomed, and osmium stained. Offaxis electron holography experiments were performed at Arizona State University using the Philips 400STFEG microscope operated at 100kV. Digital holograms with =0.25nm fringes, 520kx magnification and Is exposures were recorded using a Gatan slow-scan CCD camera. Numerical hologram reconstruction was performed employing Gatan's Digital Micrograph.

Figure 1 shows a diffraction contrast image of the specimen showing alternating styrene-rich (light) and butadiene-rich (dark) lamellae. Absolute phases were obtained from holograms in which vacuum was used as reference (region A in Fig. 1). Typical reconstructed amplitude and phase images from region A are shown in Fig. 2.
Surfactant mediated deformation of gold particles
Authors: Dabbs D. M. , Yao N. , Aksay I. A.
Published: June 2020

Ultrafine (∽ 20 nm diameter) gold particles produced by the reduction of an aqueous AuCl3 solution with citric acid have been used as model systems for the study of structural control in systems of nanometersized colloids and for the study of sintering between such particles.Liu has observed that the final, monosized particles evolve from sintered (welded) aggregates (Fig. 1). This process is visible as the color of the gold suspension changes over time. Liu also noted that the ultimate particle size was a function of the gold/citrate ion ratio in the original solution. Similarly, Ferguson et al. have observed the low temperature welding of gold surfaces when organic adsorbates move laterally to increase metalmetal contact. Although Liu has shown that aggregation and deaggregation processes are important in the evolution of colloidal particles, no explanation has been given for the dewelding mechanism of larger aggregates to form discrete particles. In this work, we combine the techniques of electron microscopy and infrared spectroscopy to propose a chemical influence for the dewelding process.
Molecular routes to the formation of ordered inorganic arrays
Authors: Hey wood Brigid R. , German Caroline
Published: June 2020

Anisotropic inorganic materials are desirable as they possess unique physical and chemical properties resulting from the manner in which the particulate components assemble. The facility to control the ordering of colloidal inorganic particles could presage dramatic improvements in the fabrication of ceramics, catalysts or paints. Biological systems have already harnessed the manifold advantages of such materials, consider shells, teeth, bones etc.(Figures 1 & 2). Synthetic strategies for the formation of nanodimensional inorganic solids abound but there are few reliable methods currently available for directing their subsequent aggregation. Some degree of ordering can be achieved by the application of external forces (magnetic, electrical) but the aggregates readily dissemble once the stimulus is removed. The requirement is, therefore, for an effective molecular route to the ordered assembly and construction of hierarchical inorganic microstructures.

The present work forms part of an extended programme of research investigating crystal tectonics, the ordering of nanodimensional inorganic solids. Here, the controlled morphological tailoring of inorganic crystals to yield a form which favours self-assembly has been investigated.
Thin-film substrates for the study of solid-state transformations
Authors: Erickson Dwight D. , Kotula Paul G. , Carter C. Barry
Published: June 2020

A popular route to obtain α-alumina (α-Al2O3) ceramics is by the use of sol-gel chemistry in which boehmite (γ-AlOOH) is dispersed in water to form a colloidal solution which is later dried and heat treated. Heat treatment of the boehmite produces a series of metastable transitional aluminas prior to the formation of α-alumina at approximately 1200°C. The transformation sequence has associated with it a large volume decrease with significant pore formationand entrapment which results in a poorly densified, vermicular α-alumina product. The use of nucleating agents or seeds such as α-alumina or hematite (α-Fe2O3) is known to lower the transformation barrier and eliminate the vermicular microstructure. The enhanced transformation has been attributed to a solid-state homo- or heteroepitactic nucleation mechanism. Direct evidence of such a mechanism, obtained using transmission electron microscopy (TEM), has been reported. In that study, however, only the edges of large (20 μm diameter) hematite particles distributed in a partially transformed transition alumina matrix were observed. The hematite crystals in that case could not be imaged in cross-section so the extent of the transformation could not be precisely determined.
Interfacial structures of dissimilar materials joined by capacitor-discharge welding
Authors: Doğan C. P. , Wilson R. D. , Hawk J. A.
Published: June 2020

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.

At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.
Dependence of growth stress on microstructure in periodic nanometer layered thin-film coatings
Authors: Nguyen Tai D. , Underwood James H.
Published: June 2020

Sputtered x-ray multilayer coatings usually exhibit the presence of intrinsic stress in the structures. Stress in the coatings are undesirable in many x-ray optical applications where flat mirrors, or precise control of curved mirrors, are designed. Controlling of the stress in these multilayers requires understanding of stress and microstructural evolution in multilayers and thin films.

Stress in thin films can be determined by the amount of bending or curvature of the substrate caused by the films. For a film deposited on a flat substrate, stress in the film is measured by using the laser scanning technique. The change in the curvature of the film and substrate is determined fromthe reflection profile fo the incident laser.For the usual case of a substrate that is elastically isotropic in the plane of the film, the expression of the biaxial stress in the film is given by the Stoney equation:

for the case in which the thickness of the films is usually much less than that of the substrate, where E and γ are the substrate biaxial modulus and Poison ratio, ts and tare the substrate and film thicknesses, and K is the substrate curvature.
Local atomic structure of relaxor ferroelectric solids studied by pulsed neutron scattering
Authors: Egami T. , Rosenfeld H. D. , Teslic S.
Published: June 2020

Relaxor ferroelectrics, such as Pb(Mg1/3Nb2/3)O3 (PMN) or (Pb·88La ·12)(Zr·65Ti·35)O3 (PLZT), show diffuse ferroelectric transition which depends upon frequency of the a.c. field. In spite of their wide use in various applications details of their atomic structure and the mechanism of relaxor ferroelectric transition are not sufficiently understood. While their crystallographic structure is cubic perovskite, ABO3, their thermal factors (apparent amplitude of thermal vibration) is quite large, suggesting local displacive disorder due to heterovalent ion mixing. Electron microscopy suggests nano-scale structural as well as chemical inhomogeneity.

We have studied the atomic structure of these solids by pulsed neutron scattering using the atomic pair-distribution analysis. The measurements were made at the Intense Pulsed Neutron Source (IPNS) of Argonne National Laboratory. Pulsed neutrons are produced by a pulsed proton beam accelerated to 750 MeV hitting a uranium target at a rate of 30 Hz. Even after moderation by a liquid methane moderator high flux of epithermal neutrons with energies ranging up to few eV’s remain.
Electron Microscopy of inorganic materials
Authors: Thomas G.
Published: June 2020

Over the past two decades tremendous progress has been made in the use of advanced transmission electron microscopy techniques to solve complex materials problems. This is especially true in the case of inorganic materials, such as multicomponent metal oxides. The inherent complexity of the crystal structure and microstructure of these ceramic materials as well as the interdependence of the final properties on microstructure and processing mean that detailed characterization of the effect of processing variables on the structure and microstructure is imperative. Electron microscopy has become firmly established as a powerful tool to explore the structure and microstructure of these materials. Due to the various types of interactions of electrons with materials, the electron microscope is unique in that it can provide morphological, structural, compositional and in the case of materials such as ferroelectrics information on the domain and domain wall configurations. This is illustrated and summarized in Fig. 1. In this review, some typical examples of the applications of advanced transmission electron microscopy techniques to solving problems in ferroelectric materials will be discussed.
Spectroscopic ellipsometry studies of ferroelectric surfaces and thin films
Authors: Trolier-McKinstry S.
Published: June 2020

Spectroscopic ellipsometry (SE) is an optical technique in which a beam of light of a known wavelength and a known polarization state is reflected from a sample surface. On reflection, the polarization state of the light beam is changed in a way which depends on the depth profile of the sample dielectric function. Data on the polarization state changes are collected at typically 50 - 100 wavelengths, and are then modeled to extract information on the sample. The depth resolution of the technique is generally in the Ångstrom range. However, because the measurement constitutes an averaging over the area interrogated by the light beam, the spatial resolution of the technique is quite low. At the Pennsylvania State University, we have developed a series of systematic calibrations for the instrument which allow measurements to be made on dielectric specimens. Thus, SE can now be used to non-destructively interrogate insulating samples, including ferroelectric materials.
Microstructural development in solution-derived PZT thin films
Authors: Headley T. J. , Tuttle B. A. , Voigt J. A. , Michael J. R.
Published: June 2020

Lead zirconate titanate (PZT) thin films are of technological interest for a variety of electronic and optical applications such as nonvolatile memories, decoupling capacitors, infrared detectors, and optical storage media. Fabrication of PZT films by solution deposition techniques is attractive because of uniform, stoichiometric control at the molecular level, ease of processing, and both low capital investment and total cost. Control of phase evolution, microstructure, crystallite size and orientation, and ferroelectric domain assemblage during processing is essential to optimize electrical and/or optical properties of the films. Factors which play a major role in controlling these parameters are details of the solution chemistry and mixing, thermal processing, Pb stoichiometry, Zr/Ti ratio, and substrate characteristics. Electron microscopy techniques have been used extensively to correlate microstructural features with film processing parameters as will be emphasized in this presentation.

As annealing temperature is increased, phase evolution in PZT thin films typically proceeds from amorphous to pyrochlore to the ferroelectric perovskite phase. Fine-grained pyrochlore crystallizes from the amorphous film at low annealing temperatures and also precedes crystallization of the perovskite phase at higher temperatures. There is evidence that the Zr/Ti stoichiometry influences the microstructure of the amorphous-to-pyrochlore transformation.
Investigation of ferroelectrics using conventional and in situ electron microscopy
Authors: Saikumar V. , Chan H. M. , Harmer M. P.
Published: June 2020

In recent years, there has been a growing interest in the application of ferroelectric thin films for nonvolatile memory applications and as a gate insulator in DRAM structures. In addition, bulk ferroelectric materials are also widely used as components in electronic circuits and find numerous applications in sensors and actuators. To a large extent, the performance of ferroelectric materials are governed by the ferroelectric domains (with dimensions in the micron to sub-micron range) and the switching of domains in the presence of an applied field. Conventional TEM studies of ferroelectric domains structures, in conjunction with in-situ studies of the domain interactions can aid in explaining the behavior of ferroelectric materials, while providing some answers to the mechanisms and processes that influence the performance of ferroelectric materials. A few examples from bulk and thin film ferroelectric materials studied using the TEM are discussed below.

Figure 1 shows micrographs of ferroelectric domains obtained from undoped and Fe-doped BaTiO3 single crystals. The domain boundaries have been identified as 90° domains with the boundaries parallel to <011>.
Effect of energy filtering on micro-diffraction in the SEM
Authors: Mancuso James F. , Fama Leo A. , Maxwell William B. , Lehman Jerry L. , Weiland Hasso , Biederman Ronald R.
Published: June 2020

Micro-diffraction based crystallography is essential to the design and development of many classes of ‘crafted materials’. Although the scanning electron microscope can provide crystallographic information with high spatial resolution, its current utility is severely limited by the low sensitivity of existing diffraction techniques (ref: Dingley). Previously, Joy showed that energy filtering increased contrast and pattern visibility in electron channelling. This present paper discribes the effect of energy filtering on EBSP sensitivity and backscattered SEM imaging.

The EBSP detector consisted of an electron energy filter, a microchannel plate detector, a phosphor screen, optical coupler, and a slow scan CCD camera. The electrostatic energy filter used in this experiment was constructed as a cone with 5 coaxial electrodes. The angular field-of-view of the filter was approximately 38°. The microchannel plate, which was the initial sensing component, had high gain and had 50% to 80% detection efficiency for the low energy electrons that passed through the retarding field filter.
EBSP: A powerful tool in studying recrystallization of metals
Authors: Furu T. , Lohne O. , Sødahl Ø. , Nes E.
Published: June 2020

The Electron Back Scattering Pattern Technique (EBSP), for measurements of crystal orientations is now a well established technique for microtexlure detennination. The application of the technique to material problems has increased quite substantially the last years, both in basic research and in more industry related problems. When studying the recrystallization process in detail a relatively large area of a specimen has to be investigated to obtain good statistical results. With a resolution of the order of 0.5-1 μm and a short processing time the EBSPtechnique has shown to be advantageous compared to TEM on one side and X-ray and neutron diffraction on the other. By the EBSP-technique we are able to follow the local texture evolution during transformation and are at the same time able to analyse changes in the untransfonncd matrix (i.e. subgrain growth etc.).

It is well accepted that the formation of recrystallization nuclei is a highly heterogeneous process.
The texture between grains
Authors: Randle V.
Published: June 2020

The ‘texture between grains’, sometimes called mesotexture, refers to the distribution of geometry/crystallography at grain boundaries and grain junctions (edges). These parameters can be accessed from measurements of individual grain orientations, and the most efficient means of collecting such data is by electron back-scatter diffraction (EBSD) in a scanning electron microscope. The reason for studying the texture at grain boundaries and junctions, on an individual basis, is that the properties of these defects (e.g. energy, mobility, diffusivity, resistivity etc) is geometry-dependent. It is desirable to investigate the nature of this relationship and how improved grain boundary properties might be achieved.

The following information can be obtained:

1.

Misorientation across grain boundaries, allowing them to be classified as low/high angle, and according to the coincident site lattice model.

2.

The orientation of the grain boundary surface (plane) itself with respect to the lattice of each neighbouring grain.

3.

Classification of grain junctions as I-lines (dislocation balance) or U-lines (dislocation imbalance).

4.

The connectivity between grain boundaries, or between the grain boundary/junction networks.
Identifying fracture mechanisms with the EBSP technique
Authors: Slavik D. C.
Published: June 2020

Stress corrosion cracking (SCC), liquid metal embrittlement, and corrosion fatigue cracking mechanisms can be evaluated by measuring grain boundary misorientations along the crack path or the crystallography of fracture surface facets. The crystallographic orientation of individual grains can be measured with back Laue, Kikuchi, selected area channelling pattern (SACP), or electron back scatter pattern (EBSP) techniques. EBSPs are unique since a large statistical sampling of individual grains or subgrains as small as a micrometer in diameter can be probed on single large samples.

For intergranular fracture, low angle and coincident site boundaries (twins as an example) are typically SCC resistant compared to general high angle grain boundaries. This observation, important for modeling fracture or improving microstructural performance, can be identified by sampling boundaries in the matrix and along the fracture path with EBSP or SACP techniques.

Transgranular fatigue mechanisms, dramatically influenced by the test environments for Al-Li-Cu alloys as shown in Figures 1a and b, can be identified my measuring fracture facet crystallographic orientations.
Microstructural characterization of interface-engineered Si3N4 for improved fracture toughness and wear resistance
Authors: Ghosh G. , Vaynman S. , Fine M. E.
Published: June 2020

Due to its low density, high strength and high modulus, Si3N4 is a potential candidate as a wear-resistant material. However, the fracture toughness of Si3N4 is rather poor. It is well known that the fracture toughness of ceramics can be increased by introducing compressive residual stress at the surface. This can be achieved by forming a chemical layer having lower coefficient of expansion at high temperature and then cooling the sample to room temperature. Improvement of wear resistance of Si3N4 by surface modification with Al2O3 has been demonstrated. Here we have studied the strengthening of polycrystalline Si3N4 by producing compressive stresses at all grain boundaries throughout the sample.

Polycrystalline Si3N4 (predominantly β-phase) powders were coated with Al2O3, dried, hot pressed and sintered at 1650°C to form Sialon at the grain boundaries. Both conventional TEM and AEM were performed to examine the as-coated powders and the samples after hot-pressing and sintering.
Nanometric plasticity in diamond-turned germanium
Authors: Callahan D. L. , Morris J. C. , Kulik J. , Patten J. A. , Scattergood R. O.
Published: June 2020

This study applies transmission electron microscopy to the analysis of anomalous ductility encountered in the diamond-point turning of semiconducting Ge. Both finished surfaces and turnings are examined. The machined surface exhibits fine parallel tool marks decorated with randomly oriented nanocrystalline Ge fragments as shown in FIG 1. The tool marks are periodic with a period corresponding to a feed pass. The fragments are the displaced debris which remain between each pass of the diamond tool. There are no indications of substantial dislocation activity or microcracks extending below this surface.

A fine Ge chip exhibiting a ductile removal morphology is shown in FIG. 2. This type of turning shows fine periodic tool marks as seen on the finished surfaces (FIG. 1) and thickness modulations perpendicular to the tool marks. These thickness modulations are identical to discontinuous shear patterns reported in soft metals turning and point to a shear slip-dominated deformation process; in fact, the general morphology of these chips is virtually indistinguishable from that observed in fine aluminum turnings.
Phase separation in sol gel-derived ceramic films of silica-zirconia, alumina-zirconia, and titania-zirconia system
Authors: Tong J. , Eyring L.
Published: June 2020

There is increasing interest in composites containing zirconia because of their high strength, fracture toughness, and its great influence on the chemical durability in glass. For the zirconia-silica system, monolithic glasses, fibers and coatings have been obtained. There is currently a great interest in designing zirconia-toughened alumina including exploration of the processing methods and the toughening mechanism.

The possibility of forming nanocrystal composites by a phase separation method has been investigated in three systems: zirconia-alumina, zirconia-silica and zirconia-titania using HREM. The morphological observations initially suggest that the formation of nanocrystal composites by a phase separation method is possible in the zirconia-alumina and zirconia-silica systems, but impossible in the zirconia-titania system. The separation-produced grain size in silica-zirconia system is around 5 nm and is more uniform than that in the alumina-zirconia system in which the sizes of the small polyhedron grains are around 10 nm. In the titania-zirconia system, there is no obvious separation as was observed in die alumina-zirconia and silica-zirconia system.