bluuebunny/crossref_metadata_2025 huggingface dataset:
A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy
Authors: Monchoux F. , Rocher A. , Martin J.L.
Published: June 2020

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.

Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary
Various technic for the measurement of step thickness on crystal surfaces
Authors: Boulesteix C. , Colliex C. , Mory C. , Pardo B. , Renard D.
Published: June 2020

Contrast mechanisms, which are responsible of the various types of image formation, are generally thickness dependant. In the following, two imaging modes in the 100 kV CTEM are described : they are highly sensitive to thickness variations and can be used for quantitative estimations of step heights.

Detailed calculations (1) of the bright-field intensity have been carried out in the 3 (or 2N+l)-beam symmetric case. They show that in given conditions, the two important symmetric Bloch waves interfere most strongly at a critical thickness for which they have equal emergent amplitudes (the more excited wave at the entrance surface is also the more absorbed). The transmitted intensity I for a Nd2O3 specimen has been calculated as a function of thickness t. The capacity of the method to detect a step and measure its height can be more clearly deduced from a plot of dl/Idt as shown in fig. 1.
In situ oxidation of Fe: Cr: Ni foils in the H.V.E.M
Authors: Rhoades Brian L.
Published: June 2020

Continuous observation of oxidation processes on the surface of austenitic stainless steels has been achieved byin situoxidation of electrochemically thinned foils in the AEI EM7 H.V.E.M. using the gas reaction cell designed by Swann (1)

Figure 1 shows the sequence of oxidation of a Fe: 18% Cr: 10% Ni foil at 700°C in air at 3.5 kPa recorded with an accelerating potential of 700 kV. Initially the surface reaction is characterised by the rapid formation of a transparent layer of minute randomly oriented crystals of the cubic oxide (Fe, Cr)3O4which is revealed by the appearance of diffuse rings on the single crystal γFe diffraction pattern. After approximately 30 seconds at 700γC the interface between the cubic oxide and the base alloy can be observed progressing inwards from the thinnest edges of the foil, and the formation of nuclei of α(Fe, Cr)2O3commences within the cubic oxide layer over both sides of the foil.
Ferromagnetic domains in CrBr3, investigated with a liquid helium magnetic specimen stage
Authors: Möllner H. , Schönauer M. , Hörl E.M.
Published: June 2020

In continuation of the electron microscopical work on CrBr3 done by Matricardi et. al. we have applied a special type of liquid helium specimen stage, which has permitted application of a horizontal magnetic field in the specimen region. During observation of the specimen we have been able to apply fields up to 60 Oe, without observation fields up to 600 Oe.

In general the observations of Matricardi et.al. have been confirmed, especially the contrast, size and shape of the domains, their non-appearance in in-focus micrographs and micrographs taken above the Curie point. On the other hand occasional regions of the foil, where the contrast disappears (Fig. 1a] are not thought to be chemical inhomogeneities. Such regions can exhibit strong domain contrast if the foil orientation changes slightly, as in our case by the thermal strains occuring in warming-up the specimen to approx. 60 K and cooling it down again.
SEM and Auger microanalysis studies of Cu-Be dynode surfaces at each activation condition
Authors: Koshikawa T. , Fujii Y. , Sugata E. , Kanematsu F.
Published: June 2020

The Cu-Be alloys are widely used as the electron multiplier dynodes after the adequate activation process. But the structures and compositions of the elements on the activated surfaces were not studied clearly. The Cu-Be alloys are heated in the oxygen atmosphere in the usual activation techniques. The activation conditions, e.g. temperature and O2 pressure, affect strongly the secondary electron yield and life time of dynodes.

In the present paper, the activated Cu-Be dynode surfaces at each condition are investigated with Scanning Auger Microanalyzer (SAM) (primary beam diameter: 3μmϕ) and SEM. The commercial Cu-Be(2%) alloys were polished with Cr2O3 powder, rinsed in the distilled water and set in the vacuum furnance.Two typical activation condition, i.e. activation temperature 730°C and 810°C in 5x10-3 Torr O2 pressure were chosen since the formation mechanism of the BeO film on the Cu-Be alloys was guessed to be very different at each temperature from the results of the secondary electron emission measurements.
Quantitative elemental analysis by transmission electron spectroscopy
Authors: Joy David , Maher Dennis , Mochel Peggy
Published: June 2020

In transmission electron spectroscopy the fundamental formula for elemental quantitation using inner-shell excitations gives the number n of atoms per cm2 contributing to the K-edge as

where Ik and Io are the integrated intensities in the K-edge and zero-loss peak, respectively. Both of these integrals are measured for a spectrometer acceptance angle 2α and an energy interval ΔE. The parameter αk(α,ΔE) is the ionization cross-section for the same angular and energy parameters. The variation of αk with α and ΔE is a function of the generalized oscillator strength and little detailed information on this quantity is available. Therefore it is necessary to proceed empirically and the simplest assumption is that

where σk is a saturation (x-ray) cross-section and ηα,ηΔEcan be identified with efficiency factors.

The accuracy of Equation (1) for K-edges from light elements (Li ≤ Z ≤ Al) is being tested by computer curve fitting and background stripping (see Fig. 1).
X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.
Authors: Cliff G. , Nasir M.J. , Lorimer G.W. , Ridley N.
Published: June 2020

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equation

where k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(1119),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.

The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.
Quantitative analysis of in situ straining experiments in the case of strong frictional forces
Authors: Louchet F. , Kubin L.P.
Published: June 2020

Investigation of frictional forces -Experimental techniques and working conditions in the high voltage electron microscope have already been described (1). Care has been taken in order to minimize both surface and radiation effects under deformation conditions.

Dislocation densities and velocities are measured on the records of the deformation. It can be noticed that mobile dislocation densities can be far below the total dislocation density in the operative system. The local strain-rate can be deduced from these measurements. The local flow stresses are deduced from the curvature radii of the dislocations when the local strain-rate reaches the values of ∿ 10-4 s-1.

For a straight screw segment of length L moving by double-kink nucleation between two pinning points, the velocity is :

where ΔG(τ) is the activation energy and lc the critical length for double-kink nucleation. The term L/lc takes into account the number of simultaneous attempts for double-kink nucleation on the dislocation line.
A comparison of dislocation arrangements in pollycristalline aluminium deformed in uniaxial and equibiaxial tension
Authors: Parker B.A.
Published: June 2020

There is increasing interest in understanding the deformation of sheet metals in stress systems similar to those used in metal-forming practice. Parameters in constitutive equations describing plastic deformation are found to be sensitive to the strain path and the present work describes experiments aimed at elucidating differences in the micromechanics of deformation.

Samples of annealed, 1-mm thick, commercial purity,aluminium sheet with a grain size of 30 μm were deformed at a strain rate of 2x10-3 sec-1 to natural strains in the range 0.03 to 0.16 in uniaxial and in balanced biaxial tension. Strains were measured at the site of the electron microscope samples using a 2-mm electroetched grid; the original rolling direction of the sheet was identified on the specimen discs.

There are difficulties in drawing conclusions from the structures observed because of the inhomogeneity of plastic deformation, particularly at low strains and because of the relaxation of the deformed structure during sample preparation.
Microanalysis of precipitates in a ferritic steel
Authors: Titchmarsh J.M.
Published: June 2020

The advances in recent years in the microanalytical capabilities of conventional TEM's fitted with probe forming lenses allow much more detailed investigations to be made of the microstructures of complex alloys, such as ferritic steels, than have been possible previously. In particular, the identification of individual precipitate particles with dimensions of a few tens of nanometers in alloys containing high densities of several chemically and crystallographically different precipitate types is feasible. The aim of the investigation described in this paper was to establish a method which allowed individual particle identification to be made in a few seconds so that large numbers of particles could be examined in a few hours.

A Philips EM400 microscope, fitted with the scanning transmission (STEM) objective lens pole-pieces and an EDAX energy dispersive X-ray analyser, was used at 120 kV with a thermal W hairpin filament. The precipitates examined were extracted using a standard C replica technique from specimens of a 2¼Cr-lMo ferritic steel in a quenched and tempered condition.
Application of convergent beam electron microscopy in materials science
Authors: Steeds J.W. , Fung K. K.
Published: June 2020

IntroductionWe have used a Philips EM400 electron microscope with a STEM pole- piece to carry out convergent beam electron microscopy on a wide variety of materials, including precipitates in stainless steels, metal/semiconductor contacts, metal oxide catalysts, environmental fibres, metastable phases in evaporated films, and transition metal chalcogenide layer compounds. Two features of this microscope make it particularly suitable for convergent beam work. These are its low hydrocarbon partial pressure which greatly reduces the carbon contamination of the specimen when working with a small probe (̴ 300 Ådiameter) and the very wide angular field of view in the diffraction plane (̴ 16°).

Two-dimensional diffraction may be used to yield information about the projected crystal potential. In certain cases a simple relationship has been established between the form of zone axis patterns and the nature of the projected potential, Oneway of using this information is by making measurements of zone axis critical voltages and we have recently extended our measurements to a number of zone axis patterns with 6 mm symmetry having different sorts of projected potential.
A new method of complex structure analysis by electron microscopy
Authors: Rybin V.V. , Voronina E.V.
Published: June 2020

Recently, it has become essential to develop a helpful method of the complete crystallographic identification of fine fragmented crystals. This was maainly due to the investigation into structural regularity of large plastic strains. The method should be practicable for determining crystallographic orientation (CO) of elastically stressed micro areas of the order of several micron fractions in size and filled with λ>1010 cm-2 density dislocations or stacking faults. The method must provide the misorientation vectors of the adjacent fragments when the angle ω changes from 0 to 180° with the accuracy of 0,3°. The problem is that the actual electron diffraction patterns obtained from fine fragmented crystals are the superpositions of reflections from various fragments, though more than one or two reflections from a fragment are hardly possible. Finally, the method should afford fully automatic computerized processing of the experimental results.

The proposed method meets all the above requirements. It implies the construction for a certain base position of the crystal the orientation matrix (0M) A, which gives a single intercorrelation between the coordinates of the unity vector in the reference coordinate system (RCS) and those of the same vector in the crystal reciprocal lattice base : .
New orientation relationship in martensitic transformation in austenitic stainless steel welded explosively
Authors: Yamashita T. , Onzawa T.
Published: June 2020

Martensitic transformation induced by plastic deformation in 18/8 stainless steel has been extensively investigated by many workers. Venablel has proposed that the orientation relationships in transformations are (111)γ// (00.1)ε// (011)α and [101]γ//[11.0]ε//[lll]α. Since metals welded explosively or shock loaded are subjected to rapid plastic deformation under a high pressure, the aspects of martensitic transformations are expected to be different from those reported hitherto. The purpose of the present experiment is to show the new orientation relationship in transformation and the new aspects of transformations in 18/8 stainless steel welded explosively as well as shock loaded. The atomic movements required in transformation are also considered.

Austenitic stainless steel plates, 3×50×200 mm, were heated in vacuum at about 700°C for 30 min to transform existing ε and α phases into γ phase. They were welded explosively by using two kinds of explosives with detonation velocities of 2,400 m/s and 5,000 m/s.
TEM - characterization of precipitates in Al-Zn5-Mgl
Authors: Degischer H.P. , Lacom W.
Published: June 2020

Various techniques of TEM are described to investigate precipitates in metals, which reach dimensions from a few nm to more than 100 nm. The examples presented here are characterized by strong interactions of the lattice structures of the inclusions and the matrix, therefore replica techniques are not applicable (an example of that is presented in [1]] because the metastable phases might change.

Selected area diffraction of regions of about 100 nm give well defined diffraction patterns of the phases present in that part of the specimen. Generally the diagram corresponding to a single precipitate cannot be obtained, but in contrast to microdiffraction techniques sharp diffraction spots can be measured. The orientation relationship between the inclusions and the matrix can be studied best, if the beam direction coincides with the main cristallographic zone axis, i.e. in cubic lattices: <001>, <112>, <111>, <011>. At these poles the patterns are highly symmetric, especially because of doublediffraction, but the diagram can be constructed to unfold the coinciding patterns.
Effets of surfaces on precipitate morphology in irradiated thin foils
Authors: Potter D.I. , Taylor A.
Published: June 2020

Thermal aging of Ni-12.8 at. % A1 and Ni-12.7 at. % Si produces spatially homogeneous dispersions of cuboidal γ'-Ni3Al or Ni3Si precipitate particles arrayed in the Ni solid solution. We have used 3.5-MeV 58Ni+ ion irradiation to examine the effect of irradiation during precipitation on precipitate morphology and distribution. The nearness of free surfaces produced unusual morphologies in foils thinned prior to irradiation. These thin-foil effects will be important during in-situ investigations of precipitation in the HVEM. The thin foil results can be interpreted in terms of observations from bulk irradiations which are described first.

Figure 1a is a dark field image of the γ' precipitate 5000 Å beneath the surface(∿1200 Å short of peak damage) of the Ni-Al alloy irradiated in bulk form. The inhomogeneous spatial distribution of γ' results from the presence of voids and dislocation loops which can be seen in the bright field image of the same area, Fig. 1b.
A TEM study of discontinuous precipitation in Cu-Be alloys
Authors: Michael Joseph R.
Published: June 2020

It is known that a lamellar discontinuous precipitate forms in aged Cu-1.8wt.% Be alloys. The purpose of this study was to investigate factors which influence the formation of the precipitate and to characterize its growth.

To determine the effect of solution treatment on the discontinuous precipitate, specimens were solution treated at 800°C, 850°C, and 900°C for 1 hour followed by an ice water quench. Some of the solution treated specimens were examined in the as-quenched condition. The remaining specimens were aged at 340°C for 24 hours. The specimens were thinned with a twin-jet electropolishing unit using 30% HNO3 in methanol at -60°C. The specimens were then examined using either an RCA-EMU3G or a Philips EM-300 electron microscope.

Each solution treated specimen was not single phase, but showed some residual grain boundary precipitate which implies that the solution anneal was not sufficient, or else precipitation had occurred during quenching. The higher solution treatment temperatures slightly reduced the amount of this grain boundary precipitate, but none completely removed it, even after five hours at temperature,indicating quench decomposition as the mechanism responsible.
A comparative electron microscopic histochemical study of myxoid liposarcoma and myxoid variant of malignant fibrous histiocytoma
Authors: Lam Ronald , Hawkins Earl , Maeda Koichi
Published: June 2020

Despite several ultrastructural studies of myxoid liposarcoma and myxoid variant of malignant fibrous histiocytoma, the histochemical nature of the extracellular matrix has not been fully explored. The purpose of this study is to cytochemically localize the glycosaminoglycans (GAG)and to compare these two apparently histogenetically different neoplasms which share a common feature of testicular hyaluronidase sensitive myxoid stroma.

Two sarcomas typical of myxoid liposarcoma and myxoid fibrous histiocytoma were examined by electron microscopy after fixation in 2.5% glutaraldehyde, 0.2% ruthenium redglutaraldehyde, and pre-embedment staining with colloidal iron (CI). Intracellular GAG could be localized in both tumors by CI. The stellate lipid-containing mesenchymal cells of the myxoid liposarcoma exhibited CI reactive sites characterized by multiple electron dense particles in secondary lysozomes as well as in small dense bodies (93-273 nm) which probably represent secretory granules (Fig. 1A).
The use of frozen tissue for diagnostic electron microscopy
Authors: Van de Velde R. , Chien K. , Heusser R.
Published: June 2020

Specimens received for evaluation by a diagnostic electron microscopy laboratory do not always meet the accepted criteria for optimal preservation. Several reasons can be cited including delayed fixation, improper fixative or sample size. When a biopsy containing the diagnostic lesion is frozen at the time of surgery for an immediate diagnosis based on a cryosection or when one has a small biopsy and is not able to set aside sufficient tissue for all study parameters electron microscopy is often deleted. In our laboratory when a needle biopsy of kidney is insufficient for a complete microscopic work-up a decision may be made to freeze the tissue to provide rapid immunohistochemical data. After sufficient frozen sections are cut, the frozen tissue can then be placed in fixative for light microscopy. Because ultrastructural data sometimes would be necessary for a complete diagnosis, we have used frozen sections of renal tissue for EM studies as well.
Square-array fiber cell membranes in the mammalian lens
Authors: Costello M.J. , McIntosh T.J. , Robertson J.D.
Published: June 2020

Two types of intercellular contacts have been observed between lens fiber cells. Gap junctions showing the normal EF-pit/PF-particle fracture pattern have been Identified in a number of species and predominate in the chick where they can cover as much as 50% of the cell surfaces. A second type of junction appears in mammalian lenses and is composed of membranes containing square crystalline arrays. In an effort to further characterize the square array membranes we have compared fragments of intact lenses to isolated junctions and used a variety of freeze-fractureetch procedures to visualize the unusual fracture morphology.

Fig. 1A shows a typical fracture pattern of fiber cell membranes in a fragment of intact rat lens cortex. Two fracture surfaces are observed separated by a large step (arrows). The upper surface is covered by large irregularly shaped particles. In the lower membrane surface 8-9 nm dia. particles are clustered in some regions into small square arrays; a few tightly packed clusters appear to be covered by a small plaque of amorphous material (circles).
Systematic evaluation of microangiopathy in diabetic Chinese hamsters: II. Morphometric analysis of basement membrane thickness in the quadriceps muscle of 19-23 month old Chinese hamsters
Authors: Sawada G.A. , Diani A.R. , Peterson T. , Wyse B.M. , Blanks M.C. , Vidmar T.J. , Gerritsen G.C.
Published: June 2020

Capillary basement membrane thickening appears to be one of the primary manifestations of microangiopathy which affects numerous capillary beds in diabetic man. Although many diabetic animal models exhibit microangiopathy in the eyes and kidneys, few studies have demonstrated the existence of muscle capillary basement membrane thickening similar to that which occurs in human diabetics.(1) Furthermore, a limited number of investigations have been systematically designed to correlate quantification of basement membrane thickness with metabolic perturbations, age, duration, and severity of diabetes. Systematic characterization of diabetic microangiopathy may help to elucidate some of the factors underlying basement membrane thickening and serve as guidelines for therapeutic studies which are designed to prevent or inhibit basement membrane thickening. Clinically, muscle biopsies are easily obtained, and this type of characterization may also prove useful in the diagnosis of diabetic microangiopathy. Therefore, the purpose of this study was to determine if basement membrane thickening is present in the quadriceps muscle capillaries of 19-23 month old diabetic Chinese hamsters in comparison with age-matched controls.
Comparative morphometry on rat liver sinusoids, endothelial fenestrae, and red blood cells fixed by constant low pressure perfusion fixation
Authors: Wisse E. , Charles K. , Vandersmissen P. , De Zanger R.B.
Published: June 2020

Fixation of the liver is critical with regard to the preservation of the fine structure of sinusoids, sinusoidal cells, the endothelial filter (1) and the space of Disse, including the sinusoidal membrane of the parenchymal cells. In this tissue region, important exchange processes between the blood and parenchymal cells occur. Lobular gradients in the endothelial filter and gradients in the geometry of the sinusoids and the space of Disse, together with regional differences in microcirculation, and interactions between blood cells and the endothelial lining, might contribute to the expression of physiological gradients in the tissue. In order to study lobular gradients of endothelial fenestrae and sinusoids, we have used light microscopy (LM), TEM and SEM of constant low pressure perfusion fixed rat livers. The diameter of red blood cells (RBC) was measured at different steps of preparation. A Kontron Ibas I image analyser with XY tablet was used for morphometric measurements. Data processing and statistical evaluation was done on the Ibas I and on a PDP 11/70 system.
Crystalline order to a resolution of 4.7 A in the sheath of Methanospirilium hungatii: A cross-beta structure
Authors: Stewart Murray , Beveridge T.J. , Sprott D.
Published: June 2020

The archaebacterium Methanospirillum hungatii has a sheath as part of its cell wall which is composed mainly of protein. Treatment with dithiothreitol or NaOH released the intact sheaths and electron micrographs of this material negatively stained with uranyl acetate showed flattened hollow tubes, about 0.5 μm diameter and several microns long, in which the patterns from the top and bottom were superimposed. Single layers, derived from broken tubes, were also seen and were more simply analysed. Figure 1 shows the general appearance of a single layer. There was a faint axial periodicity at 28.5 A, which was stronger at irregular multiples of 28.5 A (3 and 4 times were most common), and fine striations were also seen at about 3° to the tube axis. Low angle electron diffraction patterns (not shown) and optical diffraction patterns (Fig. 2) from these layers showed a complex meridian (as a result of the irregular nature of the repeat along the tube axis) which showed a clear maximum at 28.5 A, consistent with the basic subunit spacing.
An association between microtubules and nucleocapsids in nucleopolyhedrosis virus-infected hemocytes and fat body in the gypsy moth
Authors: Shields K. S.
Published: June 2020

Studies of nucleopolyhedrosis virus infection in midgut cells of corn earworm and cabbage looper larvae indicate that cytoplasmic microtubules might be involved in the vectorial movement of nucleocapsids from the microvilli, where invasion takes place, to the cell nucleus, where replication occurs. Such an association between cytoplasmic microtubules and adenovirus has been shown in Hela cells. During a recent study of the pathway of nucleopolyhedrosis virus infection in the gypsy moth, an unusual relationship was observed between microtubules and nucleocapsids in infected hemocytes and fat body cells.

Fourth instar gypsy moths were fed a lethal dose of nucleopolyhedrosis virus. Larvae died of virus in 11 to 12 days. At intervals beginning at 12 hours and continuing to 10 days post-ingestion of virus, hemolymph was collected and fat body was dissected from groups of larvae.
Immunofluorescence and electron microscopy on the same semithick section of epon-embedded material
Authors: Rupp Gerald , Bowser Samuel S. , Rieder Conly L.
Published: June 2020

When compared to the traditional thin section, semithick (0.25-0.50-µm) sections possess a number of inherent advantages for analyzing cellular ultrastructure. One such advantage is the ability to visualize biological material within semithick sections with good resolution by phase-contrast light microscopy (LM). This fact, in combination with the recent demonstration that immunofluorescence (IMF) LM can be performed on Epon-embedded material, has prompted us to investigate the feasibility of conducting IMF and electron microscopy (EM) on the same section. Such an approach would enable one to compare the distribution of labelled antigen(s), as observed by IMF, with the underlying cellular ultrastructure.
The stability of calcium oxalate during electron irradiation in an AEM
Authors: Newkirk J.W. , Khan S.R.
Published: June 2020

Calcium Oxalate is a major constituent of most kidney stone material. Electron microscope studies of materials containing calcium oxalate are complicated by decomposition during observation. This structural instability not only limits the observation time but also precludes the use of focussed probe techniques such as microdiffraction.

Two factors under the control of the experimenter which could help increase observation time are accelerating voltage and specimen temperature Available at the Center is a JEOL 200CX TEM capable of 200kV equipped with a Gatan 636 cold stage which can cool a specimen to -180C in-situ. Calcium Oxalate was deposited on carbon support films from an aqueous solution. The resulting specimens were then examined at 200kV at OC, -50C, -100C, -180C, and room temperature (RT) and at 100kV at 0 and -100C. Selected area diffraction patterns were taken at specific time intervals in order to follow the decomposition. This was done at least three times at each condition in order to insure reproducibility. Care was taken that the beam current (~ 20 microamps) and illumination were the same at 100 and 200kV.
Preparation of tissues by concurrent freezing and fracturing for x-ray microanalysis
Authors: Pelok S. D. , Heckman C. A.
Published: June 2020

It has recently become possible to localize ions of physiological interest by x-ray spectrometry coupled with electron microscopy. This methodology offers considerable potential for determining whether ion contents and fluxes are correlated with cell and tissue differentiation. The preparation of tissues for such studies can be problemmatical, however, due to the low solute content and slow rate of freezing of biological samples. Even after preparation of tissues by slam freezing, ice crystals have been found at positions representing distances of only 20 µm beneath the surface (Tormey, 1983). At even greater depths, the crystals may be large enough to disrupt the integrity of the cells and permit the translocation of diffusible ions. For many biological tissues, distances of this size order mean that internal structure is necessarily perturbed.
Vitelline and chorionic membranes of an ichneumonid parasitoid
Authors: Norton W.N. , Vinson S.B.
Published: June 2020

The chorionic membrane of parasitoid eggs is of particular interest to individuals investigating parasite-host interactions at the cellular level. Results of several studies indicate that the chorionic surface and/or material associated with the latter are of importance in providing protection against the host immune system. The primary objective of the present study was to determine, ultrastructurally the manner in which the vitelline and chorionic membranes of an ichneumonid parasitoid,Campoletis sonorensisare synthesized.

The reproductive system ofC. sonorensisconsists of 2 ovaries, each composed of 12 ovarioles. Within the ovarioles developing oocytes are enclosed by a single layer of follicular tissue. Adjacent follicle cells adhere by means of septate desmosomes and gap junctions (Fig.1). During the initial stages of vitellogenesis or yolk deposition each follicle cell is abundantly supplied with non-membrane bound ribosomes, but rough endoplasmic reticulum is sparse.
Rodlets associated with the cell wall and crystals of litter fungi
Authors: Arnott H. J.
Published: June 2020

Crystals of calcium oxalate have been found associated with a series of basidiomycete hyphae. while the morphology of these crystals is quite variable, two forms have been commonly found in association with gymnospermous litter. Graustein et al. using SEM found star-shaped (druse-like) crystal conglomerates associated with Hysterangium crassum which they believed to be the result of oxalate secretion followed by precipitation on the surface of the hyphae. Another example of fungi forming druselike crystal aggregates on their hyphae was found in a basidiomycete wood rotting fungus in which the development of the crystals appeared to arise from within the hyphae. Examination of the material by SEM showed a sheath covering the surface of crystals supporting the internal origin of the oxalate crystals. In the present case litter fungi were collected in a mixed pine and fir forest 15 miles south of Nederland, Gilpin County, Colorado (Arnott no. 264). The fungi were fixed in the field in gluteraldehyde, treated with 3% glycerol and freeze fractured. Other specimens were stored dry or critical-point dried for study by SEM. The nature of the crystals was determined by chemical solubility, birefringence and x-ray analysis. The fungi are basidiomycetes.
Cryo-SEM of the soybean rhizoplane
Authors: Perkins Sandy K. , Calvert Harry E. , Bauer Wolfgang D.
Published: June 2020

The surfaces of roots perform several important functions for plants. They provide for nutrient and water uptake from the soil, for defense against soil pests and pathogens, and for colonization by important microbial symbionts such as mycorrhizae and rhizobia. Despite their functional importance, root surfaces have not been well characterized biochemically, developmentally or ultrastructurally. A major difficulty to the ultrastructural analysis of root surfaces is preservation of the mucigel layer. Mucigel is a highly hydrated, loosely attached layer consisting primarily of polysaccharide components. In nature, mucigel serves as a lubricant to facilitate the movement of growing root tips through the soil. The mucigel layer is colonized by a variety of soil microorganisms. The microbes degrade the mucigel and at the same time add their own polysaccharide secretions to the layer. To improve the visualization of mucigel on the root epidermis we have explored the use of a cryo-chamber attached to an SEM which allows the direct observation of frozen-hydrated specimens.
Scanning electron microscopy of flowering apices
Authors: Lee Kit W.
Published: June 2020

Critical point drying (CPD) is widely used for the preparation of delicate shoot apices for scanning electron microscopy (SEM). In order to prevent charge accumulation on the dehydrated specimen, it is necessary to coat the surface with metal by vacuum evaporation or sputtering. However, cellular shrinkage is the most common irritating artifact for the shoot apices thus prepared (1). In addition, specimen charging is a common occurrence during SEM observation.

Direct examination of mature plant materials (e.g., leaf, stigma, pollen, etc.) in the SEM is one of the alternative preparation methods (2,3). Nevertheless, such a simple technique has not been commonly used for floral apices. The aim of the present investigation was to explore the feasibility of using unfixed, uncoated apices for SEM.
Electron energy loss analysis and imaging in biology
Authors: Ottensmeyer F.P.
Published: June 2020

The major advances in our understanding of subcellular morphology have come about largely due to the imaging capabilities of the electron microscope. Image detail with spatial resolutions of 2 to 3 nm is common, and in special cases resolutions better than 1 nm have been achieved on individual macromolecules. However, the desire to add a knowledge of chemistry to structural analysis invariably has led to a compromise in which spatial resolution has had to be sacrificed. At worst, e.g., in biochemical analysis, morphology is entirely destroyed. Light optical histochemical techniques, though often very specific, need only preserve structure to within about 500 nm, light optical resolution. Electron microscopic cytochemical techniques are somewhat better but are limited in specificity by chemical approaches that must incorporate heavy atoms or deposit massive precipitates at or near the primary site of analysis. This site is therefore localized relatively poorly or is covered up completely.
Microstructural characterization of zinc sulfide electroluminescent films
Authors: Emma T.A. , McDonough M.
Published: June 2020

Although the mechanisms operating during electroluminescence are generally known, a detailed understanding of the relationship of microstructure to performance characteristics has not been established. Several attempts have been made to relate microstructure to performance in sputtered zinc sulfide. Preliminary results have also been reported that relate microstructure to sputtering parameters.(3) These relationships remain poorly defined and additional characterization is clearly indicated. Much of the effort has been directed toward a description of ZnS films prepared by electron beam evaporation (EBE), and atomic layer epitaxy (ALE). Sputtered films have been somewhat neglected because of poor performance, although there are several advantages to be gained by using this method of deposition.
Roller technique for TEM preparation of viscous fluids and particle suspensions
Authors: Burnett P. , Chiuve M. , McCann M. , Walworth V.
Published: June 2020

We have developed a rapid technique that utilizes pressure rollers to spread suspensions of particles, viscous dispersions or polymer latices onto electron microscope grids.

We use motor-driven rubber rollers, as pictured in the schematic drawings of Figure 1. Other pressure roller systems, both motor-driven and hand-operated, have also worked satisfactorily. The grid and a drop of the fluid are placed between two .004” polyester sheets. Passing this sandwich through the rollers spreads a thin layer of the solution or dispersion onto the grid. The pressure is adjusted to control the thickness of the coated layer. The grid is removed and examined in the microscope.
Irradiation performance of pyrolytic silicon carbide coatings on fissile fuel particles
Authors: Lauf R. J.
Published: June 2020

Fuel particles for the High Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC coating with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) the combined effects of irradiation and fission product interactions. This paper reports the behavior of SiC deposited on fissile fuel particles and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.
STEM investigation of the low temperature ashing of coal
Authors: Allen Robert M. , VanderSande John B.
Published: June 2020

Low temperature ashing (LTA) with an oxygen plasma is done in coal research to burn off the organic material in a powdered coal sample in order to concentrate minerals in the coal for subsequent analysis. The assumption is made that the final ash represents the mineral matter because no significant mineral transformations occur at LTA temperatures (∼150C). The present work was performed to examine the changes which do take place during the LTA of coal.

The coals used in this work were PSOC 98, an HVC-bituminous coal from Wyoming, and PSOC 279, an HVB-bituminous coal from Indiana. The raw coal samples were ground to -200 mesh and a portion of each was characterized by a STEM and an electron microprobe. Sample preparation has been described elsewhere. The STEM used was a JEOL 200CX; the microprobe was a JEOL 733 equipped with digital beam control, and a commercially-available software package for the automated analysis of mineral particles in coal samples.
Study of Franckeite by HREM
Authors: Kang Zhen Chuan
Published: June 2020

Franckeite, PbSnSbFeS, is one of the series of cylindrites. Makovicky points out that cylindrite, approximately FePbSnSbS, possesses two interpenetrating incommensurable lattices, each with a pronounced sublattice; the pseudotetragonal (T) A-centered subcell has a = 11.73A, b = 5.79A, c = 5.81A, α = 90, β = 92.38, γ = 93.87; the orthohexagonal A-centered subcell of the pseudohexagonal (H) component has a = 11.71A, b = 3.67A, c = 6.32A, α = 90, β = 92.58, γ = 90.85. Numbers of large true cells were detected both by x-ray and electron diffraction. The Franckeite mineral is similar to it. In this work the mineral was found and analyzed by use of the high-resolution lattice imaging technique.
Subgrain rotation during in-situ annealing of Al-6 wt% Ni in the HVEM
Authors: Chan H. M. , Humphreys F. J.
Published: June 2020

Recently a series of commercial aluminum alloys has been developed (based on eutectic compositions), which contain a high volume fraction (∼10%) of second phase [1,2]. This paper describes the behavior of one such alloy, when thinfoil specimens (75% defd.) were annealed in-situ in the HVEM.

The eutectic alloy studied was Al-6 wt% Ni. The alloy heat treatment and particle (Al3Ni) dispersion parameters are given in Table 1. Three-mm discs were punched from as-deformed material. Thin foil specimens were prepared by standard jet polishing techniques. In-situ annealing was carried out in the AEI EM7 high voltage electron microscope at 500 kV, using a platinum ribbon heating stage [3].
Incorporation of slip dislocations in twins in titanium
Authors: Nutt S.R.
Published: June 2020

Twinning is an important mode of deformation in hexagonal metals, particularly in titanium, where there are only four independent slip systems. There have been several theoretical treatments of the interaction between slip dislocations and twins in hcp structures, although there has been only limited experimental verification of these interactions. This paper presents the results of a TEM investigation of the decomposition of 1/3<1120> slip dislocations upon penetrating a twin boundary in titanium. The work began as a study of subsurface deformation induced during dry sliding wear of titanium, and later led to in situ tensile straining experiments. Results from both types of experiment are discussed.
Precipitate phases in an Al-SiC composite
Authors: Nutt S.R. , Carpenter R.W.
Published: June 2020

The modulus of many aluminum alloys can be greatly increased by the addition of small amounts of silicon carbide. The resulting composite material is also stronger than the unreinforced alloy, but exhibits poor fracture toughness. The reason for the low ductility of Al-SiC composites is unknown, although results presented here indicate that embrittling phases present in the matrix alloy may be partially responsible. The purpose of this work has been to study the distribution of precipitate phases in Al-SiC composites, focusing particular attention on interface regions. The material studied was fabricated by adding SiC whiskers to a 2124 Al alloy powder, consolidating, then heat treating to a T6 temper.
Metastable and stable structures occurring during crystallization of some Cu-Ti amorphous alloys
Authors: Marshall A. F. , Lee Y. S.
Published: June 2020

Amorphous Cu-Ti alloys belong to the inter-transition metal class of metallic glasses which, in contrast to the metal-metalloid glasses, can often be made amorphous over a wide range of compositions. Crystallization studies of these alloys not only provide information on glass stability, but also allow characterization of equilibrium and metastable crystal phases and microstructures across a broad portion of the phase diagram.

Above 40 at% Ti, the Cu-Ti system shows a series of tetragonal intermetallics based on a body-centered tetragonal subcell and showing one-dimensional ordering of Cu and Ti along the c-axis (Fig. 1). Crystallization in the composition range about 40 at% Ti has been shown to involve intermediate transformation to a metastable microcrystalline (bcc) structure; lattice images of the fully crystallized material show a mixture of the Cu3Ti2 and Cu4Ti3 phases.
Yorktown display architecture
Authors: Gupta Satish
Published: June 2020

The advances in VLSI and CRT technology over the past ten years have resulted in feasible implementations of raster-scan displays capable of displaying complex images with reasonably high resolutions. Single chips capable of storing 64 Kilobits can be used to build memory systems capable of storing such high resolution images. The ability to manipulate these high resolution images interactively requires the ability to change a large amount of information rather rapidly.

At the IBM Thomas J. Watson Research Center, we have built a display system which addresses the problem of changing high resolution display images rapidly. The system was design to allow the rapid manipulating of images in wide range of applications. The applications planned include text formatting, computer aided design, and image processing applications which process digitized images.
Energy band effects in Si L ELS edges of Si and SiC
Authors: Skiff W.M. , Carpenter R.W. , Lin S.H.
Published: June 2020

Interpretation of near-edge core shell fine structure in electron energy loss spectra (ELS) can aid in the phase identification of small areas of sample in an analytical transmission electron microscope. Previously we performed extended Hückel molecular orbital (EHMO) calculations on a series of tetrahedral Si clusters. The resulting energies and wavefunctions were used to calculate 1st Born inelastic scattering cross sections for discrete transitions to molecular states. We have extended this work to include the effects of translational symmetry in crystalline materials - energy band effects.

Si and α-SiC samples were prepared by crushing, chemical dissolution, or grinding followed by ion beam thinning. A cryogenic stage (80K) was used to eliminate specimen contamination. ELS spectra were acquired with a 100keV converged electron probe (100Å diameter at specimen, 13mrad convergence angle) from single scattering regions (<500Å thick). Samples were tilted into kinematic diffracting conditions, with the Si near the [111] and SiC near the [0001] zone axes.
Cavity nucleation on special boundaries
Authors: Romeu L. D. , Reyes J.
Published: June 2020

All present theories of cavity formation assume cavities are nucleated during creep on geometrical irregularities at grain boundaries and triple junctions. The resulting (required) tensile stress concentration enhances diffusional creep in the vicinity of the boundary producing a high vacancy flux which ends up nucleating a cavity. No mention is done of the role played by the structure of the boundary. In this paper we present experimental evidence indicating that cavity nucleation is dependent on the structure of the boundary and that cavities in pure metals are nucleated at special boundaries.

According to Bollman, a lattice dislocation impinging on a boundary can dissociate into grain boundary dislocations with non crystalline Burgers vectors (GBDs). Also, Pond has shown that further dissociation into partials can occur in certain boundaries. When the degree of good fit decreases, the Burgers vector of any possible GBDs decrease and dislocations tend to be largely spread out becoming “dissolved” into the boundary. Boundaries capable of sustaining dislocations with relatively large Burgers vectors (long range strain fields) are called special boundaries.
A TEM study of transient oxide scales on β-NiAl
Authors: Doychak J.
Published: June 2020

The oxidation sequence of alumina forming alloys usually involves a period when transient, metastable phases of Al2O3 form rather than the thermoydnamically stable α-Al2O3 phase. The structures of these phases are spinel derivatives and are found to have a strong epitaxial relationship to the metal substrate. Using single-crystal β-NiAl doped with 0.1 wt.%Zr, the oxide phases that form in air at 800°C and the orientation relationships that exist between the oxides and metal substrate were determined using transmission electron microscopy. Once the transient oxidation stages are characterized, an understanding of the formation of stable α-Al2O3 scales can be more easily obtained.