bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical electron microscopy of aluminum ion-implanted with molybdenum
Authors: Stephenson L. D. , Bentley J. , Benson R. B. , Parrish P. A.
Published: June 2020

The microstructures of aluminum ion-implanted with molybdenum and subjected to various heat treatments are being investigated for correlation with nearsurface properties such as corrosion. Previous work indicated enhanced corrosion resistance, but dealt chiefly with the as-implanted condition and involved little microstructural characterization. In addition, the Al-Mo binary system is of interest because metastable phase formation was considered to be possible and the equilibrium phase diagram is poorly defined. Electropolished coupons 38 × 28 × 0.5 mm of 99.999% A1 with ∽0.5 mm grain size were implanted with Mo+ ions at the Naval Research Laboratory. The dual energy implant schedule of 4.88 × 1019 ions/m2 at 50 keV plus 6.14 × 1019 ions/m2 at 110 keV resulted in a peak concentration of 4.4 at. % Mo (measured by ion backscattering) within the projected range of ∽50 nm.

Disks (3 imi diam) were electrodischarge machined from as-implanted specimens and then were backthinned by electropolishing.
Study of charge transfer in FeTi
Authors: Taft∅ J.
Published: June 2020

It is well known that for reflections corresponding to large interplanar spacings (i.e., sin θ/λ small), the electron scattering amplitude, f, is sensitive to the ionicity and to the charge distribution around the atoms. We have used this in order to obtain information about the charge distribution in FeTi, which is a candidate for storage of hydrogen. Our goal is to study the changes in electron distribution in the presence of hydrogen, and also the ionicity of hydrogen in metals, but so far our study has been limited to pure FeTi. FeTi has the CsCl structure and thus Fe and Ti scatter with a phase difference of π into the 100-ref lections. Because Fe (Z = 26) is higher in the periodic system than Ti (Z = 22), an immediate “guess” would be that Fe has a larger scattering amplitude than Ti. However, relativistic Hartree-Fock calculations show that the opposite is the case for the 100-reflection. An explanation for this may be sought in the stronger localization of the d-electrons of the first row transition elements when moving to the right in the periodic table. The tabulated difference between fTi (100) and ffe (100) is small, however, and based on the values of the scattering amplitude for isolated atoms, the kinematical intensity of the 100-reflection is only 5.10-4 of the intensity of the 200-reflection.
STEM studies of small metal particles
Authors: Cowley J.M. , Monosmith W.B.
Published: June 2020

Small metal particles having diameters in the range of 5 to 100Å are currently being studied intensively because of their importance in catalytic systems. High resolution electron microscopy is a particularly valuable tool for such studies. Scanning transmission electron microscopy offers the additional advantage that high resolution images may be correlated with microdiffraction and microanalysis from selected regions of diameter close to the image resolution. In practise it is usual to obtain either microdiffraction patterns or microanalysis from regions larger than the resolution limit because of the requirements for ready interpretability of the diffraction patterns and for convenient count rates in the case of microanalysis using either ELS or EDS. In the case of small platinum particles, evidence from various techniques suggests that some oxygen may be present in a surface layer and X-ray diffraction and EXAFS studies suggest that particles in the 15-20Å size range after exposure to air, may consist almost entirely of Pt3O4 and PtO.
Analytical electron microscopy of supported bismuth molybdate catalysts
Authors: Kolar H.R. , Carpenter R.W.
Published: June 2020

Three major phases of bismuth molybdate are commonly used as selective oxidation catalysts: Bi2Mo3O12(α), Bi2Mo2O9(β) and Bi2MoO6(γ). The distribution of phases and microstructural configuration is of great interest as the phases are often mixed to produce particular catalytic properties.

Two samples of Bi2Mo3O12(α) supported on SiO2 were examined in a Philips EM400ST (Cs=1.5mm) at 100kV with a field emission source and EDAX energy dispersive x-ray spectrometer. The samples were prepared from Bi(NO3)3 and amonium molybdate with the pH adjusted to 5. Ludox was added to obtain a yield of 1:1 Bi2Mo3O12 to SiO2 and the samples were spray dried. The samples were then calcined in air at 550°c and 650°C (A and B respectively). After suspension in acetone and crushing in a mortar and pestle the samples were dispersed onto a holey carbon film on Cu grids. EDS spectra were obtained with a focussed probe of approximately 15Å diameter (measure) in the STEM mode. A Gatan low background, low temperature stage (T-185°C) was used to reduce contamination. Acquisition times of 150s were used to obtain reasonable counting statistics.
Beam Sensitivity in the Electron Microscope: Strategies for Examination
Authors: Hobbs Linn W.
Published: June 2020

A large proportion of the specimens, both organic and inorganic, examined in the electron microscope undergo some form of alteration during examination in the electron beam. That deleterious consequences often result should not be surprising when one considers that, to be resolved, an atom requires interaction with > 104 electrons which deposit energy in the specimen at a rate > 104 W/mm3. It is indeed more surprising that reliable information can be extracted at all from so many materials under these conditions. The first evidence of beam sensitivity was reported in 1947 by Burton, Sennett and Ellis in NaCl crystallites. They concluded in commendably cautious language: We have recently observed changes in a number of substances, chiefly ionic crystals, when subjected to intense electron bombardment in the electron microscope. While the results are not readily interpretable, they do suggest that the effects may not be entirely due to the heating effect of the electron beam.
On-line Fourier analysis of electron-microscope images using electronic apertures
Authors: Krakow William
Published: June 2020

In recent years digital television frame store devices have made it possible to digitze high resolution TEM images directly and obtain their Fourier transforms (i.e. optical transforms) in real time.1-3 Generally, restricted areas of 64x64 pixels are processed to reduce computer overhead hence the resultant optical transforms suffer from speckle due to the finite sampling. A larger array size of 256x256 has been attempted4 but the computation time to obtain the FFT was probably greater than ten minutes or done off-line. More efficient and extensive computer methods have been developed in our laboratory for flexible, real time, Fourier analysis via a digital TV frame store which will now be described.

The facilities of the digital frame store are described elsewhere in this proceedings. A JEOL 200CX top entry pole piece microscope was coupled through a transmission to a low light level SIT camera having a true 512x512 pixel resolution and provided input to the frame store. The problem of Fourier analysis then reduces to methods of digitizing data, transmitting it to the host computer, manipulating and processing data in the host and displaying final results by shipping da ta back to the frame store from the host computer for display.
Overlapping SAD patterns
Authors: Ploc R.A.
Published: June 2020

Most computer techniques used to index Selected Area electron Diffraction (SAD) patterns deal with simple patterns in the sense of there being present a single linear array of two reciprocal lattice vectors. If more than one crystal orientation contributes to the pattern, the investigator must judiciously pick and choose pairs of reflections (or groups of reflections if measuring errors are to be minimized) in an effort to sort out which reflections belong to what orientation. Even further complicating the issue is the usual desire to establish the orientational relationship between the different diffracting materials. These problems have been addressed at our laboratories by creating a computer code to isolate and identify overlapping SAD patterns.

The basis of our analysis rests upon the fact that each crystal orientation giving rise to an SAD pattern is but a twodimensional sectioning of a much larger three-dimensional reciprocal lattice. At 100 keV operation, the reciprocal lattice vectors associated with each reflection are, to a good approximation, parallel to the vector from the diffraction pattern origin to the reflection in question.
Electron crystallographic studies of DNA structure
Authors: Downing Kenneth H.
Published: June 2020

For many years after the elucidation of the double-helical nature of DNA structure, DNA was thought to exist only in either the A or B conformation. More recently, a great deal of variability in DNA structure has been recognized. Such factors as salt type and concentration, level of hydration, and base sequence have been found to alter the conformation from the original models in both subtle and dramatic ways. The A and B conformations are now seen as families which comprise nearly continuous variations of helical parameters. While structural studies have been carried out on DNA under a fairly wide range of conditions, by both fiber and single crystal x ray diffraction, it is likely that only a small number of the possible conformations of DNA have yet been probed. I have been studying the structure that DNA adopts under conditions which have not been well characterized previously by diffraction experiments, and have found evidence for a DNA conformation which has not previously been described.
Three-D structure of luminal plasma membrane protein from urinary bladder
Authors: Wade R.H. , Brisson A.
Published: June 2020

We present a low resolution (35 Å) three dimensional reconstruction of the molecular form of the membrane protein which forms the naturally occuring crystalline arrays of the luminal plasma membrane of the mammalian urinary bladder.

This membrane consists of concave plaques 120 Å thick with 80 Å thick interplaque regions, giving the scalloped appearance observed on thin sections. Isolated luminal membranes, observed by negative staining and freeze etching present reqular hexagonal arrays of particles with a lattice parameter of 160 Å. Image averaging techniques show that the particles possess 6 or 12 resolvable subunits having a stellate appearance. These arrays called hexagonal membranes correspond to the 120 Å thick concave plaques. Thin sections show the hexagonal membrane to be asymmetric,with a 80 Å thick luminal leaflet and a 40 Å thick cytoplasmic leaflet.

The isolation procedure described by Caruthers and Bonneville was followed with slight modifications. 1 % PTA (pH 7.0-7.4) was used as negative stain.
Chromosome behavior in living cells and the electron microscopy of chromosome attachment to the spindle
Authors: Kubai D. F. , Nicklas R. B.
Published: June 2020

During mitosis and meiosis, chromosomes are distributed to daughter cells in controlled fashion, with patterns of chromosome distribution determined by specific interactions between chromosomes and the microtubules composing the spindle. In meiosis, for example, homologous chromosome pairs (bivalents) attach to the spindle so that the kinetochore of one chromosome of the pair is associated with kinetochore microtubules extending toward one spindle pole while the kinetochore-associated microtubules of the partner chromosome extend toward the opposite pole. This arrangement assures that partner chromosomes proceed in opposite directions during anaphase chromosome movement and results in the delivery of only one member of the homologous chromosome pair to each daughter cell. This sort of descriptive/mechanical account of mitotic and meiotic chromosome behavior is now well-established. However, total understanding of the role of the spindle in precise chromosome distribution demands a much more detailed analysis of spindle organization than is yet available. For instance, determination of where and how the innumerable microtubules of the spindle are mechanically linked should help to clarify exactly where forces for chromosome movement are applied.
Vaginal microflora in a rat model of polycystic ovarian disease
Authors: Singh K.B. , Tewari Ram P. , Khosho F. K.
Published: June 2020

Exposure of female rats to continuous light for prolonged periods induces persistent estrus (PE), an anovulatory disorder. Instead of cyclic fluctuations, the vaginal smears from PE rats show only cornified cells as the hormonal control of the estrous cycle becomes inappropriate, and ovaries become cystic when ovulation ceases. The reproductive tract, a key target organ in PE, shows numerous manifestations of chronic estrogenic influence.

In this paper, we report our findings on bacterial colonizations and ultrastructural examinations of the vaginal surface epithelium of PE rats with polycystic ovaries (PCO). Quantitation of bacteria in the vaginal lavage was done with a standard volume of sterile normal saline and studied in five different hormonal states: diestrus day 1 (D-1), diestrus day 2 (D2), proestrus (Pro E), estrus (E), and persistent estrus (PE). Scanning electron microscopy (SEM) was used to examine the vaginal surface epithelium from PE rats with PCO and compared to the controls. In all rats, cardiovascular perfusion was performed for in vivo fixation of the organs using 2.5% glutaraldehyde in 0.1 M Na Cacodylate buffer (pH 7.3) for 30 minutes.
Influence of biomatrix on granulosa cell morphology in culture
Authors: Bagavandoss P.
Published: June 2020

Recent developments in tissue culture technology have shown that cells, grown on biomatrix (BM) extracted from their organ, exhibit tissue specific functions and prolonged survival in culture. I report here, Scanning Electron microscopic (SEM) observations of morphological differences that occur on rat granulosa cells when cultured on tissue culture plastic and pig ovarian BM. The BM was prepared as described elsewhere. Diethylstilbesterol (DES) capsule implanted female rats were sacrificed four days later, on day 25 of age, ovaries removed and granulosa cells isolated for culture. 500,000 cells/ml were plated on plain coverslips or on coverslips coated with BM and cultured with or without ovine follicle stimulating hormone (oFSH). At 72 hrs, 2 coverslips from each group were removed and fixed in standard aldehyde fixative. Remaining cells were challenged with 1 IU human chorionic gonadotropin and 24 hrs later fixed as above. Fixed cells were washed, dehydrated in ethanol, critical point dried, gold coated and examined with JSM-U3 JE0L SEM.
Polygonal profiles of ferritin molecules
Authors: Massover William H.
Published: June 2020

The molecular structure of the iron-storage protein, ferritin, is becoming known in ever finer detail. The 24 apoferritin subunits (MW ca. 20,000) have a 2:1 axial ratio and are polymerized with 4:3:2 symmetry to form an outer shell surrounding a variable amount of microcrystalline iron, Recent x-ray diffraction results indicate that the projected outline of the native molecule has a quasi-hexagonal shape when viewed down the 3-fold axes of symmetry, and a quasi-square shape when looking down the 4-fold axes. To date, no electron microscope study has reported observing anything other than circular profiles, which would indicate that ferritin is strictly spherical. The apparent conflict between the "hollow sphere" of electron microscopy (E.M.) and the "truncated rhombic dodecahedron" of x-ray diffraction could reflect the poorer effective resolution of E.M. coming from radiation damage, staining, drying, etc. The present study investigates the detailed shape of individual ferritin molecules in order to search for the predicted aspherical profiles and to interpret the nature of this apparent contradiction.
Visualization of protein subunits of equine ferritin
Authors: Glanvill S.R. , McLean J.D.
Published: June 2020

The first electron microscope study was carried out by Farrant in 1954. He established the characteristic appearance of the ferritin molecule, that of an iron micelle surrounded by a protein shell. The microcrystallinity of the iron core was demonstrated by Massover and Cowley in 1972 utilizing darkfield illumination to show lattice spacing of between 2.2 Å and 9.5 Å. The protein shell can be shown by negative staining techniques but because of the granularity of the stain details of the protein substructure remained unresolved. Massover was able to demonstrate the subunits by rotary shadowing with uranium oxide, but again the profile of the subunits was not resolved. An electron density map study of apoferritin indicated the subunits were cylindrical in shape with the approximate dimensions of length 55 Å and diameter 27 Å. A bismuth stain developed by Ainsworth and Karnovsky to enhance the electron opacity of ferritin in ultrathin sections has been used to produce the high resolution micrographs of the ferritin protein subunits shown in figures 1-4. The cores of the molecules show lattice spacings in both bright-and dark-field between 2.2 Å and 9.5 Å.
Macromolecular structures of biological specimens are not obscured by controlled osmium impregnation
Authors: Peters Klaus-Ruediger , Green Samuel A.
Published: June 2020

High magnification imaging of macromolecules on metal coated biological specimens is limited only by wet preparation procedures since recently obtained instrumental resolution allows visualization of topographic structures as smal l as 1-2 nm. Details of such dimensions may be visualized if continuous metal films with a thickness of 2 nm or less are applied. Such thin films give sufficient contrast in TEM as well as in SEM (SE-I image mode). The requisite increase in electrical conductivity for SEM of biological specimens is achieved through the use of ligand mediated wet osmiuum impregnation of the specimen before critical point (CP) drying. A commonly used ligand is thiocarbohvdrazide (TCH), first introduced to TEM for en block staining of lipids and glvcomacromolecules with osmium black. Now TCH is also used for SEM. However, after ligand mediated osinification nonspecific osmium black precipitates were often found obscuring surface details with large diffuse aggregates or with dense particular deposits, 2-20 nm in size. Thus, only low magnification work was considered possible after TCH appl ication.
The use of Lab-Tek tissue culture Chamber/ Slides and Flaskette for processing cultured monolayers for electron microscopy
Authors: Chien K. , Van De Velde R.L. , Heusser R.C. , Said J.W.
Published: June 2020

In situ embedding is a preferable means for the ultrastructural study of cultured cell monolayers. However, the major difficulty is the separation of the polymerized plastic resin from the supporting substrates. This abstract demonstrates a simple, fast procedure for using existing products for cell culture and in situ embedding of monolayers. Epoxy block surfaces up to 10 cm2 can be easily separated from an untreated glass slide and sectioned vertically or horizontally for EM studies.

The Lab-Tek tissue culture Chamber/Slides or Flaskette are constructed so that 1 to 8 chamber compartments or a single flask is attached to a regular glass slide by gaskets. Different cell lines or procedures can be performed on the same chamber/slide. When the plastic chambers and gasket are removed, the glass slide can be coverslipped and filed for reference. We use these products routinely for cell cultures. When an EM study is needed, we fix the cell monolayers in situ within the chambers or flask, dehydrate with ethanol, infiltrate and embed in an epoxy resin.
Microwave fixation of cells in culture for scanning electron microscopy
Authors: Chew E.C. , Riches D.J. , Tam P.P.L. , Tsao G.S.W. , Lam T.K. , Hou-Chan H.J.
Published: June 2020

The use of microwave irradiation for fixation of human and animal tissue has been proven satisfactory at light microscopic and electron microscopic levels. The present communication reports the study of the same method of fixation of cell cultures for scanning electron microscopy.

Trophoblasts were isolated from the placentae of mouse conceptuses at 10.5 days of gestation. The placenta was dissected out from the decidua and placed in Ca and Mg-free PBS, minced and then forced through a gauge-21 syringe needle. The tissue fragments were digested with 0.25% trypsin in Ca and Mg-free PBS for 20 - 30 minutes at 4°C. The digested tissue was then washed with complete PB1 medium. A single-cell suspension was obtained by spinning down the larger fragments by centrifugation. A known volume of the single-cell suspension was added to the culture medium (DCMEM and 20% FCS). The culture medium was changed after 24 hours to remove any unattached cells.
Automated image analysis applied to freeze-fracture replicas of Tetrahymena
Authors: Hufnagel Linda
Published: June 2020

Quantitative studies on intramembranous particle (IMP) frequencies and size distributions have been found to be valuable for the analysis of dynamic changes in membrane structure and function (c.f. 1,2,3). However, few such quantitative studies have been exhaustive because of the tedious and timeconsuming measurements required. The process can also be expensive, if one has to make special enlargements of photographs for accurate measurement.

I wished to examine the effects of various environmental factors, developmental sequences and preparative conditions on the frequency, size distribution, spatial distribution and orientation of IMPs in various regions of the plasma membrane of Tetrahymena, a ciliated protozoan ideally suited to studies on aging, cell-cell interactions, development of pattern and effects of toxic chemicals, whose membrane structure I have already characterized in some detail using freeze-fracture and freeze-etch methods. Both manual measurement and semiautomatic image analysis seemed out of the question for the numerous samples which would have to be analyzed and the large number of particles required for statistically meaningful results.
The influence of cell shape on mammary cell function in vitro
Authors: Shannon J.M.
Published: June 2020

It has become increasingly apparent that the normal proliferation and differentiation of cells, in both the embryo and the adult, may be dependent on the cells' interaction with the extracellular matrix. A number of investigators utilizing a variety of systems have demonstrated that the in vitro association of cells with biological substrata results in markedly improved proliferation and differentiation over that seen in cells cultured on plastic. An important, unresolved question arising from these studies concerns how the interaction(s) of the cell surface with the extracellular matrix elicits differential gene expression. One intriguing possibility is that the influence of the extracellular matrix is communicated to the nucleus via a chemomechanical bridge provided by the cytoskeleton. If this is true, then it would be expected that perturbation of cytoskeletal elements caused by changes in cell shape due to cell-substrate interactions might result in impaired cell function.
Ultrastructural studies on aortic paraganglioma
Authors: Sun C. N. , Schaefer R.
Published: June 2020

Aortic paraganglioma is a rare tumor of the superior mediastinum. The first report of aortic paraganglioma in humans was made by Lattes in 1950. Since then, there have been 40 cases published, however, ultrastructural studies are few, only one report came to our attention. For this reason, the present investigation was undertaken.

The aortic paraglanglioma mass was removed from a 47 year old white male and specimen was fixed in glutaraldehyde, then post-fixed in osmium tetroxide. After dehydration, tissues were embedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate. The spherical encapulated tumor mass measing 4x5 cm had a tannish gray, homogeneous appearance. The cells are arranged into alveolar-like clusters or nests, which were separated by narrow bands of connective tissue and blood vessels. Collagen fibrils and long space fibrous collagen were occasionally found in the connective tissue, while endothelial cells and pericytes were found in the blood vessels. There were two types of tumor cells in the alveolar-like clusters: sustentacular cells and chief cells (Fig. 1). The sustentacular cells were in juxta position to large polyhedral shaped chief cells.
Ultrastructural investigation of spontaneous pituitary gonadotroph cell adenomas in aging Sprague-Dawley rats
Authors: McComb D. J. , Beri J. , Zak F. , Kovacs K.
Published: June 2020

Gonadotroph cell adenomas of the pituitary are infrequent in human patients and are not invariably associated with altered gonadal function. To date, no animal model of this tumor type exists. Herein, we describe spontaneous gonadotroph cell adenomas in old male and female Sprague-Dawley rats by histology, immunocytology and electron microscopy.

The material consisted of the pituitaries of 27 male and 38 female Sprague Dawley rats, all 26 months of age or older, removed at routine autopsy. Sections of formal in-fixed, paraffin-embedded tissue were stained with hematoxylin-phloxine-saffron (HPS), the PAS method and the Gordon-Sweet technique for the demonstration of reticulin fibers. For immunostaining, sections were exposed to anti-rat β-LH, anti-ratβ-TSH, anti-rat PRL, anti-rat GH and anti-rat ACTH 1-39. For electron microscopy, tissue was fixed in 2.5% glutaraldehyde, postfixed in 1% OsO4 and embedded in epoxy-resin. Tissue fixed in 10% formalin, embedded in epoxy resin without osmification, was used for immunoelectron microscopy.
Multivariate classification of diffraction patterns: Effects of different stains on images of mitochondrial pore arrays
Authors: Frank Joachim , Mannella Carmen
Published: June 2020

Correspondence analysis has previously been used for classifying images of single macromolecules.In these applications, each individual image is represented by a N-dimensional vector where N is the number of pixels selected by an area-of-interest mask. Clustering of images may be detected by projecting these vectors into a suitably chosen, low-dimensional subspace. In the current work, this analysis is extended to diffraction information.

Subject of this study are the characteristic stain-dependent changes in appearance of the pore arrays in outer membranes of N. crassa mitochondria.3 Since the stain moeities active in solution carry different charges at different pH, the different staining patterns may be indicative of surface charges of the pore protein and lipid.

Although different patterns of stain distribution can be distinguished in the Fourier filtered images, there is a considerable amount of scattering within each experimental set. This has led us to search for a method that would allow the grouping of experimental data to be assessed, and the significance of structural differences to be established. In principle, correspondence analysis of the filtered images would achieve this goal.
Three-dimensional reconstruction of the 30S ribosomal subunit from randomly oriented particles
Authors: Verschoor A. , Frank J. , Radermacher M. , Wagenknecht T. , Boublik M.
Published: June 2020

The small (30S) subunit of prokaryotic ribosomes can assume any of a wide range of tilt positions on the specimen support. Correspondence analysis should make it possible to order views appearing in the electron micrograph according to the angle of tilt.

231 individual windowed images from two micrographs showing negatively stained 30S subunits from E. coli ribosomes were subjected to multireference alignment. Correspondence analysis yielded six morphologically significant factors of variance. The second of these related to variations in stain concentrations, which are irrelevant at the level of gross morphology. The coordinates for each image in five-dimensional space (relating to factors 1,3,4,5, and 6) were subjected to a nonlinear mapping algorithm, which calculated an optimal two-dimensional map.

The resulting distribution (Fig 1) consisted of two clusters, one of rightfacing, the other of left-facing views. Subaverages along the outer margin of the cluster on the left showed the particle in a range of typical views.
Diffuse Scattering from Disordered Crystals
Authors: Iijima S.
Published: June 2020

A simple case of disorder in crystals is that of interstitials with little lattice relaxation. If this disorder takes place two-dimensionally, repeating regularly in the third direction, interpretation of diffuse scattering intensities becomes straightforward and optical diffraction experiments on model structures can be justified. This ideal case has been demonstrated in crystals of oxides in the Nb2O5-WO3 system (1). Interstitials of metal- oxygen strings which were distributed over some of the pentagonal tunnels in the host structure (tetragonal tungsten bronze-type) result in diffuse ring patterns appearing around the sharp Bragg spots (Fig. la). Positions of the individual interstitials were directly determined from high resolution structure images (Fig. 2a) and thereby diffuse scattering intensities can be approximately expressed by an equation
Computer Simulation of Defect Images from Transmission Electron Microscopy
Authors: Cooper W. D.
Published: June 2020

During recent years, defect structures resulting from radiation damage have been successfully studied by a large number of investigators. Early studies were based primarily on the analysis of the characteristic black-white lobe contrast from small dislocation loops. Contrast calculations indicated that the sense of the black-white contrast, relative to the diffracting vector at a given depth in the foil, could be used to determine the nature (vacancy or interstitial) of the loop. These calculations have also been used to formulate rules for the determination of the loop Burgers vector and habit plane normal [1]. For pure edge loops this simple procedure is quite satisfactory, but for loops with a shear component of the Burgers vector it becomes very involved and, in certain geometries, may lead to erroneous conclusions. Carpenter has demonstrated that “unsafe” orientations exist which do not permit the unambiguous determination of the Burgers vector relative to the loop plane [2].
A Stable Field Emission Electron Source
Authors: Bottoms W.R. , Haydon G.B.
Published: June 2020

There is great interest in improving the brightness of electron sources and therefore the ability of electron optical instrumentation to probe the properties of materials. Extensive work by Dr. Crew and others has provided extremely high brightness sources for certain kinds of analytical problems but which pose serious difficulties in other problems. These sources cannot survive in conventional system vacuums. If one wishes to gather information from the other signal channels activated by electron beam bombardment it is necessary to provide sufficient current to allow an acceptable signal-to-noise ratio. It is possible through careful design to provide a high brightness field emission source which has the capability of providing high currents as well as high current densities to a specimen. In this paper we describe an electrode to provide long-lived stable current in field emission sources.

The source geometry was based upon the results of extensive computer modeling. The design attempted to maximize the total current available at a specimen.
Electronic Cone Illumination with the Conventional Transmission Electron Microscope
Authors: Krakow William
Published: June 2020

An electronic device has been constructed which manipulates the primary beam in the conventional transmission microscope to illuminate a specimen under a variety of virtual condenser aperture conditions. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. The device has been utilized mainly for the hollow cone imaging mode where the device provides a microscope transfer function without zeros in all spatial directions and has produced high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens.
Computer Experiments for High Resolution Electron Microscopy at 100 and 500 kV
Authors: Krakow William
Published: June 2020

A system of computer programs has been written to simulate both bright-field and dark-field micrographs of a variety of materials of interest in both metallurgical and biomolecular applications of high resolution electron microscopy. Selected area diffraction has also been incorporated into this system of programs as well as the ability to orient the object of interest relative to the microscope coordinate system by specifying the Eulers angles between the microscope and object coordinate systems. For bright-field imaging both elastic and inelastic scattering can be included for the tilted beam or axial imaging modes. Optical diffraction programs yield the power spectra of these micrographs and filtering programs have also been designed for high pass filtering and correction of the microscope transfer function. Some of the variables which are input into this system of computer programs are: objective lens defocus, spherical aberration, chromatic aberration, beam tilt, objective aperture size and electron wave length.
Ion Accelerator - HVEM Link
Authors: Bennetch J. I. , Horton J. A. , Jesser W. A.
Published: June 2020

The simulation of radiation damage has primarily been accomplished by either ion accelerators or high voltage electron microscopes. Recently a 200 kV gas source ion accelerator (Kaman Nuclear Model A-1001) modified to accept a Granville Phillips precision leak valve (Model 203) has been attached to a 500 kV TEM for simulation of the fusion reactor environment by Simultaneous Accelerator Microscope Irradiation (SAMI) conditions.1,2 While accelerators have been linked to TEM columns before, those cases are for 100 kV and 200kV microscopes and hence displacement damage from the electrons is limited.3,4 The arrangement of the accelerator and microscope is schematically shown in Figure 1. A drift tube 4' long links the microscope column to the ion accelerator. The 8 mm gap between pole pieces of the objective lens permits easy access of the ion beam to the specimen through a side entry port at 90° to the entry port of the specimen.
Backscattered Electron Spectroscopy with a Si(Li) Detector
Authors: Russ J.C.
Published: June 2020

Solid state lithium-diffused silicon detectors are commonly used as energy-dispersive X- ray detectors. These devices will, however, produce electrical pulses with a height proportional to the energy of electrons (and other particles) as well. We have used a Si(Li) detector with conventional electronics (amplifier, multi-channel pulse-height analyzer) to measure the energy spectrum of electrons backscattering from pure elements with atomic numbers from 12 (Mg) to 92(U).

Since the electron beam striking the target also generates X-rays (characteristic and continuum) that are measured by the detector along with the backscattered electrons, and since it is not possible to stop the X-rays from reaching the detector while allowing the electrons to pass, we measured the electron spectrum by difference. Figure 1 shows superimposed, the spectra (for a copper target) of X-rays plus electrons (upper curve) and X-rays only (lower curve), the latter obtained with the use of a magnetic electron trap in front of the detector.
Microstructure Of Wulfenite, Chalcopyrite, And Barite: Some Mineral Engineering Applications Of The Tem
Authors: Murr L.E.
Published: June 2020

The role of crystal defects and related microstructures in controlling the mechanical properties and other behavior of metals and alloys is well known, and materials characterization, particularly microstructural, has become an integral part of metallurgical and materials engineering. Similar characterization would also seem to be valuable in other more general areas of mineral processing and mineral engineering, particularly since it might be expected that crushing, grinding, leaching, and other forms of extraction of mineral and metal values would also be dependent upon the existing microstructure, or the development of microstructure with processing. While there has been a considerable effort made in recent years to characterize mineral microstructures in general1, there have been few attempts to characterize the microstructures of ore minerals.
The Role Of Dislocations And Related Crystal Defects In Providing Preferential Sites For Bacterial Attachment To Mineral Surfaces
Authors: Murr L.E. , Berry V.K.
Published: June 2020

It has recently been shown that bacteria involved in the catalysis of leaching reactions which convert insoluble sulfides in copper-bearing ores to water soluble sulfates not only attach to the mineral surface under certain conditions, but that in porphyry copper ores where CU2S, CuFeS2, and FeS2 phase regions are disseminated throughout quartz monzonite, feldspar, or related host-rock matrices, the attachment is observed to occur only on the exposed sulfide phase surfaces, and not on the matrix or host-rock surface1,2. This selective attachment of microorganisms to specific chemical regions as a result of the necessity to sustain rather specific and rather delicate microbial metabolisms raises interesting questions about the initial surface site preference for the attachment of individual microorganisms.

Murr and Berry3,4 have postulated that dislocations might serve as initial attachment sites, or that as a result of defect-induced variations in surface energy or volume energy, groups of dislocations might provide preferential sites for initial bacterial attachment.
An Electron Microscopic Study Of Some Solid-State Polymerization Reactions
Authors: Jones William , Thomas John M. , Livesley David A.
Published: June 2020

There is interest at present amongst organic solid-state chemists in producing, through topochemical reaction, stereoregular and crystalline polymers of high molecular weight. In certain reactions the geometry of the polymer product and the high degree of crystallinity are completely determined by the molecular packing in the monomer crystal (1). In others, however, low molecular weight product or products not predicted from a knowledge of the monomer packing have lead to suggestions that dislocations or other regions of imperfection may be important as sites of initiation of reaction or possibly of nucleation of the formed polymer (2). Defects will also control the length of the formed polymer (2).

We have utilized transmission electron microscopy for investigating defects in anthracene and some of its derivatives, which also undergo chemical and photo-induced reactions, occasionally in a manner not determined by the perfect crystal lattice (3). Consequently we felt it appropriate to observe by TEM foils of monomer before, during and after polymerization.
Characterization of Deposits on Silicone Contact Lenses from Clinical Wear Studies
Authors: Freeman H. , Berta R.
Published: June 2020

Contact lenses made from silicone elastomer have been made and tested because of the inherent permeability of silicones to gases. Adequate transfer of such gases as oxygen and carbon dioxide through the Silcon® lens tends to minimize metabolic imbalance at the cornea. This property offers the potential for comfortable extended wear of Silcon® lenses. However, as in other man-made materials interacting with body processes, silicone contact lenses are subject to the accumulation of biological materials which gradually impair visual acuity. Morphological and chemical information about the accumulation has been gained by the use of replication electron microscopy, scanning electron microprobe; and identification of biological species by mass spectrometry.

Silicone contact lenses were dispensed to patients in the course of an experimental clinical program during which frequent examinations were made of the patient's eyes and lenses. Lens care regimens were carefully specified.
Fringe Spacing Measurements of Lattice Imaging Micrographs
Authors: Wu C.K.
Published: June 2020

Lattice imaging has been utilized in order to detect localized, plane-byplane variations in composition through correspondence with fringe spacing variations in the image. In this way direct observations concerning defects and phase transformation processes in materials are obtained. Since lattice imaging pictures are usually taken at high magnification (a magnification at the final screen of approximately x500,000 is generally necessary for a line resolution ∽2Å), the analysis of the fringe spacings must be performed very carefully. Three different methods were employed, viz., A) Microdensitometer trace analysis: The individual fringe spacings can be found by directly measuring the distance from peak to peak on a microdensitometer plot of the image and dividing by the appropriate magnification. The exact position of each peak sometimes becomes unidentifiable due to lack of contrast in the negative near the fringe.
Defocused Images Of Electrostatic And Magnetic Edges
Authors: Mory C. , Colliex C.
Published: June 2020

Fresnel fringes are a common feature in CTEM defocused images of specimen edges. The detailed contrast is actually governed by the exact geometry of the termination of the edge. Calculations by Fert and Laffite (1) and by Fukushima et al (2) have shown that the intensity profile is very sensitive to the existence of a region of thickness gradient. Joy et al (3) have clearly interpreted these contrast variations as a consequence of the refraction of the electrons in this zone.

In order to determine how far these effects can be used to evaluate physical parameters of an edge, we have computed images of thin electrostatic or magnetic edges to fit them with experimental observations. An optical model with a pure phase or a mixed phase^and amplitude object is used. The structure of the wave function a on the exit surface of the specimen forms the input signal for the subsequent electron optical imaging system which involves spherical and defocusing aberrations.
Improvement of TEM Bright-Field Images by Hollow-Cone Illumination
Authors: Rose H. , Fertig J.
Published: June 2020

Axial coherent (parallel) illumination, commonly used for bright-field imaging, creates artifacts and strong structural noise. These parasitic structures are caused by an overlap of Fresnel fringes, which can be largely suppressed if hollow-cone (partially coherent) illumination is employed (1,2). However, it is commonly assumed that this imaging mode leads to a severe reduction in contrast. To obtain reliable information on the maximum contrast achievable, we have made extensive calculations of images of single atoms taking into account both phase contrast and scattering absorption contrast. The image contrast C = C(r, C3, Δf, U, θo, θ, Z) of an atom is a function of the image coordinate r, sperical aberration C3, defocus Δf, voltage U, aperture ΔO, cone angle Δ of the illumination, and the atomic number Z. At resolutions currently obtainable, the bright-field contrast of the objects can be described very accurately if the first- and second-order terms of the Born approximation of the scattering amplitude are considered.
Instrumentation For Quantitative Microscopy
Authors: Ralph B. , Jones A.R.
Published: June 2020

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.

In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.
A New System For Optomanual Semiautomatic Quantitative Image Analysis
Authors: Rohr H.P.
Published: June 2020

Today, in image analysis the broadest possible rationalization and economization have become desirable. Basically, there are two approaches for image analysis: The image analysis through the so-called scanning methods which are usually performed without the human eye and the systems of optical semiautomatic analysis completely relying on the human eye.

The new MOP AM 01 opto-manual system (fig.) represents one of the very promising approaches in this field. The instrument consists of an electronic counting and storing unit, which incorporates a microprocessor and a keyboard for choice of measuring parameters, well designed for easy use.

Using the MOP AM 01 there are three possibilities of image analysis:

the manual point counting,

the opto-manual point counting and

the measurement of absolute areas and/or length (size distribution analysis included).

To determine a point density for the calculation of the corresponding volume density the intercepts lying within the structure are scanned with the light pen.
Stereological Analysis Of Sem Images
Authors: Schmiβer H. S , Swensson R. A.
Published: June 2020

Development of new signal detection systems for STEREOSCAN scanning electron microscopes has greatly increased the applicability of quantitative image analysis to pictures obtained with an s.e.m. While quantitative image analysis has proven to be a powerful technique to draw quantitative information from pictures obtained from light microscopes as well as various other sources of images, the field of scanninq electron microscopy has largely been uncovered in the past.

This was mainly due to the particular appearance of “normal” s.e.m. pictures. Exactly those features which make s.e.m. pictures easy to interpret intuitively an aesthetically attractive i.e. the pseudo three dimensional appearance made it virtually impossible to treat these images with the well known methods of electronic image analysis.
Electron Microscopy of Precipitates of NaCl: FeCl2 Crystals
Authors: Yacaman M. Jose , Vook R. W.
Published: June 2020

Suzuki phase precipitates1 produced by divalent impurities in alkali halide crystals can act as preferential gucleation sites for vapor deposited metals using the gold decoration method2. The present work applies this technique to the study of NaCl: FeCl2. Crystals with several FeCl2 concentrations were grown by the Kyropoulos method in a controlled atmosphere and thermally homogenized. The final impurity concentration Cs was determined by atomic absorption spectroscopy. Precipitates were inducel bg linear cooling from 550°C to room temperature at rates of 7.64, 3.82, and 23°C/hr. Gold decoration was performed at 10 Torr on vacuum-cleaved surfaces at 100°C. Precipitates were visible because of an enhanced nucleation density: Figs. la - c. The volume fraction Vσ of precipitates was determined from the total fractional area of the precipitates in micrographs taken from several areas of the replicas. Vσ is linearly related to Cs (Fig. 2) with a slope of 8.1 ± 1.0.