bluuebunny/crossref_metadata_2025 huggingface dataset:
Freeze fracture imaging and computer simulation of liposome structure: Membrane geometry and defects
Authors: Zasadzinski Joseph A.
Published: June 2020

At low weight fractions, many surfactant and biological amphiphiles form dispersions of lamellar liquid crystalline liposomes in water. Amphiphile molecules tend to align themselves in parallel bilayers which are free to bend. Bilayers must form closed surfaces to separate hydrophobic and hydrophilic domains completely. Continuum theory of liquid crystals requires that the constant spacing of bilayer surfaces be maintained except at singularities of no more than line extent. Maxwell demonstrated that only two types of closed surfaces can satisfy this constraint: concentric spheres and Dupin cyclides. Dupin cyclides (Figure 1) are parallel closed surfaces which have a conjugate ellipse (r1) and hyperbola (r2) as singularities in the bilayer spacing. Any straight line drawn from a point on the ellipse to a point on the hyperbola is normal to every surface it intersects (broken lines in Figure 1). A simple example, and limiting case, is a family of concentric tori (Figure 1b).

To distinguish between the allowable arrangements, freeze fracture TEM micrographs of representative biological (L-α phosphotidylcholine: L-α PC) and surfactant (sodium heptylnonyl benzenesulfonate: SHBS)liposomes are compared to mathematically derived sections of Dupin cyclides and concentric spheres.
The core cylinder in the junctional SR of single intact skeletal muscle fibers of the frog after quick-freezing: Its topography
Authors: Sommer J.R. , Nassar R. , Scherer B.
Published: June 2020

The "core cylinder" (CC) represents confluent electron lucencies seen in the junctional SR (JSR) when skeletal muscle is fixed in the presence of cations such as ruthenium red. CCs are a consistent feature in quick-frozen muscle fibers (Fig.l), both in the resting state and after various intervals between stimulation and freezing, incl. tetanus (5 sec, 50Hz). The CCs are excentrically located inside the JSR and are separated from the junctional membrane toward the transverse tubule by the coextensive line(CL) and from the rest of the membranous envelope of the JSR by granular material (junctional granules, JG). JGs are also found elsewhere in the free SR. Whereas the JGs fill the JSR completely in many cases, often they are separated from the JSR envelope by a peripheral clear halo except in the region of the CL; in favourable sections they form regular rosettes about the CC (Fig.3). Very frequently, the CC loose their more circular configuration (in one dimension)(Fig.4), with flares connecting the CCs with the peripheral halo at either end of the CL (Fig.3). The junction between the electron-lucent flares and the ends of the CL subtends, approximately, the location of the staggered rows of pits on the E face of the freeze-fractured JSR(Fig.2).
Deafferentated vestibular nerve
Authors: Fermin C.D. , Igarashi M.
Published: June 2020

Contrary to the cochlear branch of the VIIIth nerve, the vestibular branch does not degenerate quickly in the squirrel monkey after the end organs are surgically removed. This surgical procedure is favored by some investigators who advocate that removal of the vestibular receptors does eventually lead to the death of the nerve. Others think that the neurons of the vestibular ganglion can regenerate and contribute to partial reoccurrence of the symptoms the patient had before surgery. Thus, this problem remains unsettled. We are presently studying the vestibular nerve and ganglia of the squirrel monkey (Saimiri sciureus) in order to examine the fate of the surviving neurons, and the changes that these cells undergo after labyrinthectomy. Animals were anesthetized, perfused intracardially and the specimens were processed for transmission electron microscopy (TEM) as previously described. For light microscopy (LM), some specimens were embedded in JB-4 plastic, cut serially at 5 micra and stained with 0.2% toluidine blue and 0.1% basic fuchsin in 25% alcohol.
Neuromuscular junction alterations in extraocular muscles of myotonic rats
Authors: Pachter Bruce R. , Eberstein Arthur
Published: June 2020

Rats treated with 20,25-diazacholesterol manifest clinical as well as physiological signs characteristic of human myotonic dystrophy. The extraocular muscles (EOMs) of such myotonic rats were shewn in a prior study to exhibit by electromyography, prolonged insertion activity, high frequency bizzare discharges, and myotonic responses, which are comparable to that observed in skeletal muscle. Light and electron microscopy of the EOMs revealed numerous fiber alterations, i.e., dense bodies, atrophic and angulated fibers, cell vacuolization, dilation and proliferation of the sarcoplasmic reticulum, mu11ilamllar membranous bodies, atypical mitochondrial clusters and disruptions, mitochondrial inclusions, excessive lipid accumulations, and myofibrillar degeneration. Many of these changes have been reported in human myotonic peripheral musculature. The most susceptible fiber populations in the EOMs were found to be the pale, intermediate, and red singly-innervated fibers of the global region; the pale fibers were the most affected.
Interaction of the cell surface with the extracellular matrix during epithelial morphogenesis
Authors: Rapraeger Alan C. , Koda Joy E. , Bernfield Merton
Published: June 2020

The shape of adherent cells is the product of two scaffolds: the Intracellular cytoskeleton and the surrounding extracellular matrix. During epithelial morphogenesis, changes In cell shape require modifications in both of these structures. Studies of the components of the cytoskeleton, their Inter-relationships and their response to cell motility and shape changes have provided rich Information about how changes in cytoskeletal organization may take place. Less is known about how extracellular molecules interact with one another, and particularly how the cell regulates these matrix interactions. As an approach to this problem, we are investigating the structure and function of heparan sulfate proteoglycans in mammary eplthellal cells, molecules that are able to bind a variety of matrix molecules, and therefore may have an organizational role in extracellular matrix assembly. Additionally, some are Integrally associated with the plasma membrane, thereby potentially anchoring the cell to the matrix.
Effect of permeabilization of tight junctions on morphology of 3-cell intersection
Authors: Polak-Charcon Sylvie , Pitelka Dorothy R.
Published: June 2020

Tight junctions (TJ) at 3-cell intersections (3Cl) appear in freeze-fracture replicas as channels limited by 2 vertical strands in one cell's membrane, each representing the line of fusion with one of the other cells. Recent observations show in mammary cells exposed to a calcium chelator, retraction of microvilli from cell borders, starting at the 3Cl. Ca2+ depletion is also known to reduce transepithelial resistance. These observations led us to inquire whether 3Cl might be the sites most vulnerable to agents that increase junction permeability. We used the rat mammary adenocarcinoma cell line LA7 (from R. Dulbecco) to ask this question.

LA7 monolayers were treated with reagents known to affect transepithelial permeability: Ca2− and Mg2+-free phosphate-buffered saline (PBS-CMF), the Ca2+ chelator EGTA (0.025%), colchicine (0.1mM), cytochalasin B (10 μg/ml), procaine (1 - 10 μg/ml), kinetin (0.4 μM), phalloidin (10-50 μM). Confluent LA7 on impermeable substrates form many domes (Fig I) as fluid transported basally is trapped between the monolayer and the plastic. Their presence is proof of TJ integrity and was the criterion used in this study. Functional effects of the treatments were measured by maintenance or change in dome numbers and morphological effects were followed by freezefracturing.
Structure of bacteriophage lambda receptor protein
Authors: Jap Bing K. , Glaeser Robert M.
Published: June 2020

Receptor protein for phage lambda (LamB protein) is a major outer membrane protein in maltose-induced E. coli cells. This protein (M.W. ∼48,000) facilitates the passage of maltose, maltooligosaccharides and other sugars across the outer membrane. LamB and matrix proteins (OmpC and OmpF) form permeability channels and share a number of unique physical and biochemical properties. Yamada et al. have carried out experiments reconstituting LamB proteins with 1ipopolysaccharides, 1ipopolysaccharide derivatives, fatty acids, and phospholipid. The reconstituted specimens show first order hexagonal lattice with lattice constants that vary with the reconstitution component.

We have reconstituted LamB protein with phosphatidylcholine from soybean. The reconstituted LamB membrane patches have dimensions from 0.2 μm to 3 μm in diameter with typical size of about 0.4 μm. LamB specimens negatively stained with phosphotungstic acid is shown in Figure l together with its optical diffraction pattern. The optical diffraction pattern shows a hexagonal lattice with lattice constant ∼7.2 nm. The diffraction intensities extend to a resolution of ∼2.4 nm.
Ultrastructural features of human pituitary adenomas producing growth hormone, prolactin and thyrotrophin
Authors: Horvath E. , Kovacs K. , Scheithauer B. W.
Published: June 2020

The majority of pituitary adenomas are monohormonal and monomorphous, i.e. they produce only one hormone and are composed of one morphologic cell type. About 12-15% of pituitary adenomas are piurihormonal containing more than one hormone, either in one cell type (monomorphous) or 2 or more morphologic types (plurimorphous). Most piurihormonal adenomas produce growth hormone and prolactin. Other combinations are uncommon.

We report here the ul trastructural features of 11 pituitary tumors which produced growth hormone (GH), prolactin (PRL) and thyrotrophin (TSH), as shown by immunohistochemistry. They were removed by surgery from 3 men and 8 women between 24 and 63 years of age. Eight tumors were associated with elevated blood GH levels and acromegaly. In 3 patients, blood prolactin levels were elevated. Hyperthyroidism was evident in 1 woman with elevated blood TSH levels.

For fine structural studies, parts of tissue were fixed in 2.5% glutaraldehyde, postosmicated in 1% OsO4, dehydrated in graded ethanol, processed through propylene oxide and embedded in an Epon-Araldite mixture. Ultrathin sections were stained with uranyl acetate and lead citrate and investigated with a Philips 300 electron microscope.
Zoospores were produced by gill rot pathogen
Authors: Liu Kuo-chun , Chien Chau-heng
Published: June 2020

Branchiomycosis of fish is commonly known as gill rot which was first reported in Germany more than seventy years ago. In recent years world-wide occurrence was observed among cultured fish species. The causal agent of this disease was a low form of fungus in the genus of Branchiomyces. Two species, B. demigrans and B. sanguinis, were identified mainly according to their morphological differences such as the thickness of the hyphae and the diameters of the spores.

Available literature indicated that the shape of the spores was round and the size of the spores was 5 to 9 μ in B. sanguinis and 12 to 17 μ in B. demigrans. Recently, Egusa and Ohiwa reported similar observation from diseased samples of eel Anguilla japonica cultured in Japan. They also reported that no flagellum was observed in fixed samples. Chien et al., indicated that the spores produced by the pathogen were endospores.
Historical Introduction
Authors: Heidenreich R. D.
Published: June 2020

This program has been organized by the EMSA to commensurate the 50th anniversary of the experimental verification of the wave nature of the electron. Davisson and Germer in the U.S. and Thomson and Reid in Britian accomplished this at about the same time. Their findings were published in Nature in 1927 by mutual agreement since their independent efforts had led to the same conclusion at about the same time. In 1937 Davisson and Thomson shared the Nobel Prize in physics for demonstrating the wave nature of the electron deduced in 1924 by Louis de Broglie.

The Davisson experiments (1921-1927) were concerned with the angular distribution of secondary electron emission from nickel surfaces produced by 150 volt primary electrons. The motivation was the effect of secondary emission on the characteristics of vacuum tubes but significant deviations from the results expected for a corpuscular electron led to a diffraction interpretation suggested by Elasser in 1925.
TEM Evidence for the Ejection of Matter by Energetic Displacement Cascades
Authors: Merkle K.L.
Published: June 2020

At the first wall of a D-T fusion reactor very energetic displacement cascades will be produced. These cascades are initiated by 14 MeV neutron recoils of energies near 100 keV and above. Such cascades can also be produced by selfion bombardment. TEM has served in the past as a valuable tool in investigations of cascade defect structures; also quantitative correlations between cascades produced by energetic self ions and 14 MeV neutrons have been established.1 Qualitatively Figs. 1 and 2 show strong similarities between 200 keV self ion cascades and cascades produced by 14 MeV neutron bombardment of Au. Most clusters visible in Fig. 1 and 2 are thought to result from the collapse of depleted zones. The presence of multiple defect clusters is indicative of subcascade formation.

The intersection of an energetic cascade with a surface will lead to the ejection of atoms or clusters of atoms. This problem of surface erosion has recently found considerable attention.
In-Reactor Precipitation of Gamma Prime in Nimonic PE16
Authors: Gelles D. S.
Published: June 2020

Iron-based precipitation hardened superalloys are being considered for use as structural materials in Fast Breeder Reactors due to their high temperature strength. Appropriate application of these materials requires an understanding of the microstructural stability of precipitation hardening phases in the radiation damage environment. It is not yet clear whether irradiation will affect precipitate stability in-reactor; a whole host of possible behaviors have thus far been considered (1). Transmission electron microscopy appears to be the technique best suited for evaluating precipitate stability. Precipitate sizes in these alloys range from a few atom diameters to several microns, well within the range of state-of-the-art electron microscopy techniques.

An example of the complexity of reactor-induced gamma prime precipitation for these materials is provided in Fig. 1. Nimonic PE16 (Fe-44Ni-15Cr-lAl-lTi-3Mo) is a precipitation hardened commercial alloy containing aluminum and titanium additions in order to develop the coherent gamma prime phase for improved strength.
Direction of Black-White Contrast from Small Dislocation Loops
Authors: Cooper W. D. , Hartley C. S. , Hren J. J.
Published: June 2020

Dislocation loops observed in the transmission electron microscope exhibit a characteristic black-white strain contrast under two-beam dynamical diffracting conditions. A simple concept of the nature of this contrast indicates that the black-white direction should lie parallel to the projection of the Burgers vector onto the image plane. Using the results of several contrast calculations for small loops, Wilkens and Riihle (1972) recognized that the black-white direction did not always lie parallel to the Burgers vector projection. For loops with an appreciable shear component, they concluded that a determination of the black-white direction would not be sufficient for analysis of the loop crystallography. However, for pure edge loops they predicted that the black-white direction would correspond (within a few degrees) to the projection of the Burgers vector. Numerous investigators have used this erroneous assumption to analyze the crystallography of loops.
High Resolution Electron Microscope Using a New 200 kV Electron Gun
Authors: Kamimura S. , Katsuta T. , Minamikawa Y.
Published: June 2020

Higher accelerating voltage has been required of transmission electron microscopes in various research and application fields. In this report, a new electron gun developed by Hitachi, Ltd. will be described. The aim of this development was to design a compact 200 kV electron microscope offering simplicity and convenience of operation and maintenance and the highest possible performance.

Description will be made first on the packaged electron gun. Fig. 1 shows the sectional view of the gun. The accelerating tube is built in the gun housing so as to be free from exterior impact. Unlike the conventional gun housing, this one is made of epoxy resin instead of metal. The inside diameter of the housing is reduced to 170 mm due to the excellent insulation property of epoxy resin. A bushing for high voltage cable is mounted on the housing, making its withstand voltage high in spite of the short contour of the housing (140 mm).
A Simple Airlock Gold Coater and Technique for Coating Heat Sensitive Samples
Authors: Allard L.F. , Thomas P.D. , Bigelow W.C. , Kirchoff B.K.
Published: June 2020

In our laboratory, we frequently observe delicate biological samples in the SEM using cold stage and micromanipulation techniques. The accumulation of static charges often occurs on frozen tissue samples, and on critical point dried samples which are being microdissected “in situ”, thereby causing degradation of the image. In such instances it is useful to be able to coat a sample with gold to eliminate charging without warming it or exposing it to the atmosphere. We have developed a simple airlock coater for the JEOL JSM-U3 SEM, which permits a frozen specimen to be coated without introducing surface artifacts which result from moisture condensation or heating during coating. The entire system can be constructed for about $500.00. Detailed drawings and circuit diagrams are available from the authors upon request.

Figure 1 shows an overall view of the airlock coating chamber attached to the SEM airlock. This chamber has an insulated copper rod feedthrough which is attached to a sample stage.
Field Emission Scanning Auger Electron Microscopy
Authors: Bovey P. , Warden I.A. , Williams P.M.
Published: June 2020

The combination of a scanning electron microscope with Auger Electron Spectroscopy provides a powerful means of micro surface analysis. A high brightness Field Emission source permits Auger analysesat the 300A level, in addition to secondary electron scanning microscopy with a resolution of 100A. An airlock mechanism is provided to allow the rapid introduction of samples and a non-dispersive X-ray detector with which “bulk” chemical analysis can be carried out can be included. The instrument is operated at ultra-high vacuum for routine analyses but can be fitted with an “environmental” cell in which a sample can be examined in situ at 0.1 torr gas pressure an up to 600 C. Other radiation sources can be added to extend the applicability of the instrument. These include a twin-anode x-ray source for ESCA and ion guns for depth profiling.
The New ANL Materials Science HVEM Facility
Authors: Lyles R. L. , Merkle K. L. , Okamoto P.
Published: June 2020

A new transmission HVEM facility has been completed at Argonne National Laboratory. The ANL HVEM provides the beginning of a dedicated materials research laboratory which will subsequently include an interface with a 2 MV tandem accelerator and a low energy ion injector for iri situ ion irradiation and ion beam analysis experiments (Figure 1).

The microscope, an improved version of the AEI EM-7, has an accelerating voltage of 1.2 MeV. Moreover, a number of exceptional features have been designed into the instrument which will significantly enhance its usefulness in materials research: 1. High vacuum specimen chamber with direct ion pumping. 2. Instrumentation for two independent and alternatively selectable dark field conditions. 3. Negative ion trap. 4. Ion beam interface. In addition, a helium temperature, side entry, cooling stage is being developed at ANL . The negative ion trap and the ion beam interface are features that have not been previously included in HVEM designs.
Lattice Imaging of a High-Angle Grain Boundary in Germanium at 500kv
Authors: Krivanek O.L. , Isoda S. , Kobayashi K.
Published: June 2020

The promise of the new generation of high-voltage, high-resolution electron microscopes (HREMs) for atomic resolution studies in materials science has excited considerable interest (1). This paper describes an application to elemental Ge of the first member of this generation, the Kyoto 500kV HREM (2).

Fig. 1 shows a (Oil) Ge crystal almost certainly less than 100Å thick, supported by a thin amorphous Ge film and surrounded by several Au crystallites. The specimen was prepared by vapor co-deposition of Au and Ge from separate sources onto a rock salt substrate held at room temperature. The imaging parameters were: accelerating voltage 500kV, axial illumination, no objective aperture, el. opt. mag. 200 000x, exposureotime 10 secs and, as the optical diffractogram (Fig. lb) shows, defocus =-600Å (≃ Scherzer defocus). The dashed circles in the diffractogram show the theoretical extent of the first phase-contrast transfer interval. The interval easily includes all the 111 diffraction spots, indicating that all the end-on (ill) planes and the defects they contain have been imaged faithfully and without distortion.
Experiments With Thin Single Crystal Graphite Films
Authors: Mlinarsky L.
Published: June 2020

The ability to make extremely thin single crystal films could be potentially of great use for high resolution biological and single atom electron microscopy because the substrate noise could be greatly reduced over that obtained with amorphous films. (That is, the number of atoms in any resolution cylinder would not obey a Poisson distribution but would vary in a regular fashion.) This would increase the visibility of atoms and biological particles and would permit imaging with less dose. In addition, very thin films would be useful in minimizing multiple scattering effects in electron energy loss spectra which would be helpful in interpreting EXAFS-like structure near inner shell excitation edges. For these reasons, we have started a program aimed at trying to fabricate very thin (∽20-30 Å) single crystal films.

We have begun to grow thin graphite films after the method of Riddle and Siegel (1).
Electron Optical Studies Of Sepiolite-Bas Ed Drilling Fluids Subjected To Hydrothermal Treatments
Authors: Güven Necip , Carney Leroy L.
Published: June 2020

Mineralogical components of drilling fluids may undergo changes under increased temperatures during the deep-well drilling operations and give rise to unusual mud control problems. Sepiolite- based drilling fluids have been subjected to hydrothermal treatments in order to examine the possible mineralogical reactions. The sepiolite was obtained from Industrial Mineral Ventures, Inc., and it contained about 10% carbonate and 10% mica as impurities. A drilling fluid (350ml) containing sepiolite (25g), NaOH (0.5g), and organic polymers (2.5g) was heated at 370°C for 16 hours in a cement consistometer. Sepiolites occur as individual fibers or bundles of them; their lengths may reach up to 2 microns and their widths range from 200 to 300 angstroms. After the above hydrothermal treatment, no significant changes were noted in morphological features of sepiolite.
Optimized Programs For Testing Image Processing Algorithms
Authors: Welton T.A.
Published: June 2020

Previously reported programs1-3 for the enhancement of bright field electron micrographs have now been made much more flexible and trouble- free. In addition, the cost of image processing has been much reduced by careful attention to programming details. Finally, a program has been added to synthesize bright-field micrograph data, with considerable flexibility in choice of microscope parameters. This system of programs is being used to evaluate the modified Wiener processing algorithm previously described, with the aim of identifying those aspects of real micrographs which have thus far prevented practical enhancement. There is some evidence that realization of adequate beam coherence and energy spread may not suffice for high resolution enhancement, and coma and sample thickness problems accordingly need exploration. Both can be handled, if necessary, by relatively simple changes in the processing algorithms. These difficulties are, incidentally, important considerations in the evaluation of the relative merits of computer and coherent optical processing procedures. This is true since the coherent optical processing appears incapable of allowing for these complications.
Calculation Of Stem Dark-Field Images
Authors: Fertig J. , Rose H.
Published: June 2020

Dark-field imaging is a promising procedure to visualize single atoms in high resolution electron microscopy. The quality of a dark-field micrograph depends to a large extent on the illumination mode for the CTEM or on the detector geometry for the STEM. The most commonly used dark-field modes are: CTEM with axial, tilted, or hollow-cone illumination and STEM with an annular detector limited by the angles and θ1-θ2. The STEM is equivalent to a CTEM which uses hollow-cone illumination of finite angular width (limiting angles θ1, θ2). the following we always assume θ2 = п/2.

The three CTEM imaging modes have been investigated theoretically by several authors. Krakow (1) computed dark-field images of small organometallic molecules assuming tilted illumination. However, he could not achieve results for hollow-cone illumination because his computing method was too timeconsuming. Hoch (2) calculated images of model objects under axialy tilted, and hollow-cone illumination of infinitely small angular widthy applying the fast Fourier transform technique.
Quantitative Analysis of Human Gastric Parietal Cells
Authors: Turner J. N. , Chey W.Y.
Published: June 2020

Stereologic analysis has been performed on the images of parietal cells from the body of the stomach from eleven patients--five with Zollinger-Ellison Syndrome (Z-E), three with gastric ulcer (GU), and three with esophagitis who serve as controls (C). Two blocks were randomly selected from each patient for sectioning. All parietal cells in both block faces were photographed and five cells were randomly selected from the photographs from each block (i.e. 10 cells per patient).

Cell diameters were measured both parallel to and perpendicular to the basement menbrane. Figure 1 is a bar plot showing the means and standard deviations for these measurements. There was no statistical difference between the three groups for the measurement parallel to the basement membrane. However, the mean perpendicular diameter of the cells (19.0 μm) from the Z-E cases was greater than that (15.8 μm) of the control group (p<0.05).
On the Design of Magnetic Spectrometers for Electron Energy Loss Spectroscopy
Authors: Fields J. R.
Published: June 2020

In designing an energy loss spectrometer, one can avoid the need for a highly regulated high voltage supply by decelerating the electrons prior to the energy analysis.1,2 However, with present technology it is equally feasible to regulate the high voltage to a few parts per million and to use a magnetic spectrometer to analyze the fast electrons.3 With that approach one requires a magnetic analyzer which will perform optimally in a given application. Specific cases have been treated, notably that of constant angular magnification4, and theoretical calculations sufficient for most design problems have been performed5-9 Even so, it is not always clear how to formulate design criteria which can be used to determine values of the various parameters which describe a magnetic spectrometer. Moreover, the ideal focusing case has not been treated for any but constant angular magnification instruments.
Subcellular Localization of Fluorinated Serotonin in Human Platelets by Electron Energy-Loss Spectroscopy
Authors: Costa J.L. , Joy D.C. , Maher D.M. , Kirk K.L. , Hui S.W.
Published: June 2020

Fluorinated organic molecules have considerable potential as tracers in bio logical systems, since a number of fluorinated analogs demonstrate biological activity similar to that of the parent molecule1. To date, however, the subcellular localization of fluorine has been hampered by the relatively low sensitivity of conventional X-ray microanalysis systems to fluorine. Electron energy-loss spectroscopy, in contrast, is a very efficient method for detecting light elements. We have capitalized on the high sensitivity of this technique to fluorine to identify and localize fluorinated serotonin at a subcellular level in human platelets.

Intact human platelets were incubated with 10-5 M concentrations of either serotonin (5HT) or 4,6 difluoroserotonin (DF5HT)2 for 30 minutes at 37°C. Following the incubation period, air-dried whole mounts3 were prepared on 200 mesh copper grids coated with collodion and carbon. Individual platelets were examined at 80 kv in the STEM mode (10 nm spot size), utilizing a Jeol 100B microscope equipped with a field emission gun, a scanning attachment, an electron spectrometer, and a Kevex analysis recording system.
Considerations on the Use of Electron and Photon Beams for Determining Micro-Chemical Environment
Authors: Isaacson M. , Utlaut M.
Published: June 2020

Over the last half decade there has been growing interest in the use of synchrotron radiation as a tunable x-ray source for performing chemical and electronic spectroscopy of matter (e.g., 1). Concurrent with this (although a lot less visable in the popular literature) has been the increasing trend towards utilization of electron energy loss spectroscopy (ELS) within an electron microscope environment (e.g., 2). From the point of view of materials analysis, it is worthwhile to compare electron and photon beams insofar as their detective sensitivity is concerned. This is of interest since, for many applications, one must decide whether ELS within an electron microscope or setting up an experiment at a synchrotron radiation facility will give one the desired information. This paper represents a preliminary study aimed at making such a comparison. (The reader is alerted to keep in mind that extrapolation of such a comparison beyond the limited scope of what we intend can be dangerous!)
The Effect of Energy Loss on Lattice Fringe Images of Dysprosium Oxide—
Authors: Craven A. J. , Colliex C.
Published: June 2020

Energy filtered 7.5 Å lattice fringes from type C crystalline dysprosium oxide, (Dy203), have been recorded with a V.G. Microscopes HB5 STEM. A spectrum from the specimen is shown in fig. 1. The principal features are a collective 'plasmon' excitation (P) at 15.7 eV and a 5P core-loss (C) at 37.2 eV (1). Fig. 2a, b, c, d are lattice fringe images recorded in 100 seconds with an objective (i.e. probe) semi-angle of 8 mrad and a collector semi-angle of 1 mrad. Fig. 2a is unfiltered and fig. 2b, c, d are filtered with an 8 eV energy window centred on 0 eV, 16 eV and 37 eV respectively. The lattice fringes persist in the images formed with loss electrons, but their visibility is much reduced because of lower contrast and higher noise. The contrast was measured from line traces and for one set of results was 0.17 ± 0.02 for the unfiltered image, 0.27 ± 0.02 for the zero loss image, 0. 21.± 0.02 for the plasmon image and 0.27 ± 0.03 for the core loss (contrast = 2(Imax - Imin)/(Imax + Imin)).
Quantitative Metallurgical Applications of Plasmon Energy Loss Microanalysis
Authors: Williams David B.
Published: June 2020

When A1 and Mg alloys are studied in the transmission electron microscope, the principal energy loss sustained by the 100 kV imaging electrons that of plasmon excitation (quantized oscillations of the free electrons). ! By placing an electron spectrometer beneath the viewing screen of the micro scope, with a limiting entrance slit, the energy loss spectrum from a line ' the bright field image may be obtained, see Fig. 1. The spectrum consists a zero loss line and plasmon loss lines corresponding to one or more plasmo excitations. It has been shown that the spectral peak position may be reladirectly to composition with an accuracy of < 1wt%)(1) and a spatial resolution of < 10nm.(2) Thus changes in peak separation across the spectrum may interpreted in terms of composition changes along a line in the image.

By placing the spectrometer entrance slit underneath a grain boundary, the solute composition profiles accompanying grain boundary precipitation have been investigated.
Transmission Electron Microscopy Studies of Ti-6A1-4V Showing the Microstructural Influence on Fatigue Life and Microhardness Values
Authors: Imam M. Ashraf
Published: June 2020

The purpose of this paper is to discuss the improvement of some material properties through changing the microstructure. Transmission electron microscopy TEM, has been used to characterize microstructures of the Ti-6A1-4V alloy after different heat treatments. These microstructural studies have been correlated with fatigue property measurements and microhardness values as shown in Table 1. In general, microhardness increases with increasing solution treatment temperature while fatigue resistance reaches a maximum at 900°C and then again decreases.

Experimentally, the ELI Ti-6A1-4V specimens were heat treated under the conditions shown in Table 1. Surfaces were polished to a 16 μm surface prior to fatigue testing at ±0.020 shear strain with a constant axial stress of 2.12 x 107 N/M2. Thin foils for TEM observation at 100KV and 200KV were obtained by spark cutting followed by electropolishing in a solution of 62.5% methanol, 31% butanol and 6.5% of 70% perchloric acid at 13.9 volts at -40°C.
Dislocation Microstructures in Fatigued Copper
Authors: Winter A.T.
Published: June 2020

A characteristic feature of fatigue in many materials is the concentration of deformation into bands of intense slip. In single crystals of copper fatigued at low constant plastic strain amplitudes these "persistent slip bands" (PSB's) are first observed as the stress amplitude reaches saturation.(1,2).Their formation in the immediately succeeding cycles is rapid but after perhaps twice the number of cycles required to reach saturation the specimen enters a more stable state which is maintained until large cracks are formed near the end of the test. In this state, although PSB formation may continue slowly its rate is very much reduced - few new bands form and the existing ones do not show much increase in width. The fatigue deformation is carried in a quasi-reversible manner by the PSB's whilst the remainder of the specimen (known as the matrix) becomes inactive. At the specimen surface the PSB's are marked by intense rumpling which is known to play a part in crack formation and fatigue failure.
Cementation of Copper on Pure Aluminum: Analysis of the Two-Step Rate Mechanism by Scanning Electron Microscopy
Authors: Annamalai V.
Published: June 2020

Iron has been the major source of the precipitant metal in the copper cementation process. Aluminum, due to its abundant availability in the form of beverage cans, has been used successfully in the process in laboratory experiments1. In a recent study of the cementation of the Cu2+/pure A1 system2, it was found that the reaction rates followed a distinct two-step rate mechanism. This paper presents a physical explanation of the two-step rate mechanism on the basis of the structural characteristics of the copper deposits.

A specially designed cementation cell along with aluminum (99.99% pure) rotating discs was used in this study2. Ultrasonic experiments were conducted using an 80 watt Bransonic 12 ultrasonic cleaner. Copper deposits were examined in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25 KV in the secondary electron emission mode.

In most of the experiments, two distinct kinetic regions were observed, namely an initial slow rate followed by a final enhanced rate.
a<100> Dislocation Loops in MgO
Authors: Narayan J. , Ohr S. M.
Published: June 2020

Dislocation loops having a/2 <110> Burgers vectors on {110} planes introduced by plastic deformation and subsequent annealing of MgO have been studied extensively in the past using transmission electron microscopy.1 Recently it was reported that high temperature electrical conduction for a long period of time (> 100 hours) induced a thermal breakdown2 in MgO crystals. Transmission electron microscope investigation of these samples just before the thermal breakdown, revealed the presence of a type of loop not previously observed in this material with a<100> Burgers vector lying in {100} planes.

Figure la-d shows electron micrograph of two of these a<100> type loops for diffraction vectors (ḡ) [200], [020], [220] and [220], These micrographs were taken under kinematical diffraction conditions with the deviation parameter w ∽ 1.0. From stereo microscopy it was determined that the loops labeled α and β lie on (001) and (100) planes respectively.
SEM Study of Tension Wood Fiber Morphology and its Effect on Paper Properties
Authors: Robinson K. W.
Published: June 2020

Tension wood (TW) is an abnormal tissue of hardwood trees; although it has been isolated from most parts of the tree, it is frequently found on the upper side of branches and leaning stems. TW has been classically associated with geotropic alignment, but more recently it has been associated with fast growth. Paper made from TW is generally lower in strength properties. Consequently, the paper industries' growing dependence on fast growing, short- rotation trees will result in higher amounts of TW in the final product and a corresponding reduction in strength.

Relatively few studies have dealt with the role of TW in the structure of paper. It was suggested that the lower strength properties of TW were due to a combination of factors, namely, its unique morphology, compression failures in the cell wall, and lower hemicellulose content. Central to the unique morphology of the TW fiber is the thick gelatinous layer (G-layer) composed almost entirely of pure cellulose.
A Freeze Shadow Technique for the Preparation of Soft Paint Latexes for Electron Microscopy
Authors: Walter Earl R. , Bryant Glen H.
Published: June 2020

With the development of soft, film forming latexes for use in paints and other coatings applications, it became desirable to develop new methods of sample preparation for latex particle size distribution studies with the electron microscope. Conventional latex sample preparation techniques were inadequate due to the pronounced tendency of these new soft latex particles to distort, flatten and fuse on the substrate when they dried. In order to avoid these complications and obtain electron micrographs of undistorted latex particles of soft resins, a freeze-dry, cold shadowing technique was developed. The method has now been used in our laboratory on a routine basis for several years.

The cold shadowing is done in a specially constructed vacuum system, having a conventional mechanical fore pump and oil diffusion pump supplying vacuum. The system incorporates bellows type high vacuum valves to permit a prepump cycle and opening of the shadowing chamber without shutting down the oil diffusion pump. A baffeled sorption trap isolates the shadowing chamber from the pumps.
Studies of Oxide Formation on Copper Thin Films by Electron Microscopy
Authors: Hembree G. G. , Otooni M. A. , Cowley J. M.
Published: June 2020

The formation of oxide structures on single crystal films of metals has been investigated using the REMEDIE system (for Reflection Electron Microscopy and Electron Diffraction at Intermediate Energies) (1). Using this instrument scanning images can be obtained with a 5 to 15keV incident electron beam by collecting either secondary or diffracted electrons from the crystal surface (2). It is particularly suited to studies of the present sort where the surface reactions are strongly related to surface morphology and crystal defects and the growth of reaction products is inhomogeneous and not adequately described in terms of a single parameter. Observation of the samples has also been made by reflection electron diffraction, reflection electron microscopy and replication techniques in a JEM-100B electron microscope.

A thin single crystal film of copper, epitaxially grown on NaCl of (100) orientation, was repositioned on a large copper single crystal of (111) orientation.
Limitations and Prospects of Freeze-Fixation and Freeze-Etching
Authors: Moor Hans
Published: June 2020

Ever since the freeze-etching method became a routine laboratory technique, an increasing number of scientists has applied it in biological and especially in membrane research. The manifold details of membrane architecture gave rise to a multitude of questions as to the functional significance of these structures, the possible introduction of artificial alterations and the presumptive limits of the method.

The limitations of freezing originate from segregation phenomena in the cytosol caused by rapidly growing ice crystals. Using the standard freezing technique (dipping specimens in liquid Freon or propane) segregation artifacts are avoided by the application of antifreeze agents. Mani structures are stable or can be stabilized against the action of the antifreeze. If this is not possible, very high freezing rates have to be achieved. These require special techniques using a propane jet or a jet of liquid nitrogen under high hydrostatic pressure (1).
Comparison of Three Common Fixatives on Bacteria
Authors: Hanson J.M. , Pfister R.M. , Smucker R.A.
Published: June 2020

The ultrastructure of the cytoplasmic membranes, cell walls, and mesosomes of Escherichia coli and Bacillus megaterium were found to be significantly affected by different fixation procedures.

Logarithmic cells were divided into equal portions and different fixation procedures employed. A 6% glutaraldehyde solution followed by 1% 0s04 fixa-tion (1). The Ryter-Kellenberger (R-K) fixation (2) and Luft's ruthenium red (R-R) (3). The glutaraldehyde-OsO4 and R-K were post fixed with 2% and 0.5% uranyl acetate respectively. Thin sections were post stained with uranylacetate and lead citrate. One sub-portion of Bacillus megaterium was criti-cally-point dried. Glutaraldehyde-OsO4 critically-point dried whole mounts (Fig. 1) showed little background material and smooth walls. The R-K cells (Fig. 2) had irregular outer walls. The R-R cells (Fig. 3) were irregular and revealed external polysaccharide. There is a distinct difference in the internal morphology of the wall layers using the E. coli (Figs. 4,5,6). A heavier staining of the CM was observed in B. megaterium (Fig. 7).
Ultrastructural Characteristics of an Organism Intimately Associated with Necrotic Bone in Gangrenous Stomatitis (Noma)
Authors: Merrell B.R. , Joseph S.W.
Published: June 2020

Gangrenous stomatitis (noma) is a severe disfiguring, gangrenous condition involving the cervicofacial region of young children in the underdeveloped areas of the world. It begins as an indurated papule in the premolar or molar area of the mouth. Progression is rapid and insidious, eventually leading to extensive destruction of the facial structures, including the soft tissue, bone, and teeth. Rapid onset of secondary infection has made effective bacteriological studies difficult and confusing (1). Several types of bacteria, chiefly anaerobic, have been implicated as primary pathogens. The present paper describes an ultrastructural study of necrotic bone from paraffin embedded material collected in Indonesia from advanced cases of noma, showing a close association between a microorganism and the necrotic bone.

Figure 1 shows that the colonization of the bone by the organism presents as a brush border-like layer, consisting of long filamentous, rod-shaped organisms overlaying an irregular surface of bone.
Quantitative Organic Analysis by Electron Probe: Urea
Authors: Beeuwkes R.
Published: June 2020

It is now just 10 years since the first published description of a method for elemental analysis of biological fluids by electron probe (1). During this decade microdroplet analysis techniques have been highly perfected and are in routine use in many laboratories for the study of droplets in the 10 to 100 picoliter (pi) range. Despite this rapid development, droplet analysis remains almost entirely elemental since techniques for molecular characterization by electron probe have not been established. In renal physiology, where microdroplet analysis has been most accepted, single specimens are routinely studied for Na, K, Ca, Mg, Cl, P, and S; but urea, which plays a fundamental role in the mechanism of urine concentration, cannot be directly measured except by wet photometric techniques requiring several nanoliters of fluid and many quantitative handling steps (2, 3). In this report, a new method for droplet analysis is presented which permits electron probe measurement of both urea and elemental concentrations in single 50 pi droplets.
Direct Analysis of Frozen Hydrated Tissue Sections Using X-Ray Analysis and STEM
Authors: Saubermann Albert J.
Published: June 2020

X-ray analysis can be used for identification and quantitative analysis of biologically important ions and soluble compounds. Conventional methods for specimen preparation are usually not applicable, thus requiring new and unusual methodologies. Ion loss or movement during fixation can be minimized by using cryotechniques which permit the investigator to analyze his specimen frozen and hydrated. Frozen hydrated (F.H.) tissue sections have several advantages over bulk F.H. tissue: one can rely upon conventional morphology for structure and cell identification; the excited volume of tissue is easier to define thus reducing uncertainty of X-ray signal origin; and the X-ray signal can be quantified with relative ease. Although there are benefits to using F.H. tissue sections there are also problems. The preparation and analysis of F.H. sections can be divided into three broad areas which include: (1) initial preparation, (2) transfer; and (3) analysis. Initial preparation is concerned with sampling, freezing and sectioning.
Scanning Electron Microscopy of African Swine Fever Virus in Tissue Culture
Authors: Breese S. S. , Pan I. C.
Published: June 2020

Previous studies of African swine fever virus (ASFV) development and its hemadsorption property by transmission electron microscopy showed virus emergence from the cells (1) and the attachment of infected cells to red cells (2). The scanning electron microscope has been used in the present study to examine the surfaces of infected leucocytes and Vero cells. Leucocytes prepared from swine blood were grown in buffer in Leighton tubes containing glass microscope cover slips and infected with ASFV Lisbon '60 strain prepared from tissue culture. After 1 hr. incubation at 37°C, the inoculum fluid was removed and replaced with F15 balanced salt solution maintenance fluid and 10% foetal bovine serum. The Vero cell cultures were grown and infected in a similar manner. Observations were made starting 18 hrs. after infection.

The cover slips were washed gently with Sorenson's buffer pH 7.3, fixed in 2% Glutaraldehyde in Sorenson's buffer and post-fixed in 2% osmic acid in Sorenson's buffer. Dehydration with graded alcohols was followed by immersion in amyl acetate.
Some Observations on Intra-Mitochondrial Crystals
Authors: Clarke J. A. , Landon D. N. , Ward P. R.
Published: June 2020

Intra-mitochondrial crystals have been noted in muscle biopsies from patients in a wide variety of diseased states. As far as we are aware, none of these crystals have been subjected to detailed crystallographic analysis. Recently, similar crystals were observed in a biopsy from a patient with a mitochondrial myopathy, characterised by a deficiency in reducible cytochrome b (Morgan-Hughes, J. A., Darveniza, P., Kahn, S. N., Landon, D. N., Sherratt, R. M., Land, J. M. and Clark, J. B., 1977, Brain, In Press). Aldehyde-fixed, osmicated resin imbedded material was examined using Siemens, JEOL and Phillips electron microscopes with goniometer specimen stages. The crystals generally lay between the outer and inner mitochondrial membranes and measured 1 - 3 μm in length and 0.1 - 0.3 μm in width. Characteristically, these crystals revealed specific periodicities.