bluuebunny/crossref_metadata_2025 huggingface dataset:
Black-white contrast of dislocation loops
Authors: Hren J. J. , Cooper W. D. , Sykes L. J.
Published: June 2020

Small dislocation loops observed by transmission electron microscopy exhibit a characteristic black-white strain contrast when observed under dynamical imaging conditions. In many cases, the topography and orientation of the image may be used to determine the nature of the loop crystallography. Two distinct but somewhat overlapping procedures have been developed for the contrast analysis and identification of small dislocation loops. One group of investigators has emphasized the use of the topography of the image as the principle tool for analysis. The major premise of this method is that the characteristic details of the image topography are dependent only on the magnitude of the dot product between the loop Burgers vector and the diffracting vector. This technique is commonly referred to as the (g•b) analysis. A second group of investigators has emphasized the use of the orientation of the direction of black-white contrast as the primary means of analysis.
Quantitative transmission electron microscopy of small agglomerates in HF-O
Authors: Rühle M. , Elssner G. , Ruano O.
Published: June 2020

High amounts of gases or carbon are soluble on interstitial sites of the hexagonal lattice of hafnium. The gas atoms influence nearly all physical properties; e.g., the critical resolved shear stress τ (CRSS) is drastically increased with an increasing content of gas atoms. Different authors measured the temperature dependence of τ for different 0 concentrations (cO ≲ 1.5 at%). The CRSS increases strongly with decreasing measuring temperature T. Ruano and Elssner concluded intuitively from the non continious shape of the τ-T curve, that besides the interstitially solved single gas atoms also agglomerates of gas atoms should be present in the specimens. These agglomerates act as strong barriers against plastic deformation. - A superposition of the 2 types of barriers (single interstitial gas atoms and agglomerates) could explain the shape of the τ-T curve. TEM studies were performed to prove this assumption of the existence of agglomerates. Hafnium specimens with different 0 content (0.13, 0.65 and 1.17 at%0) were electrolytically thinned and investigated with a Siemens ELMISKOP 102 operated at 125 kV.
Electron microscope investigations on ion damage in platinum
Authors: Schindler R.
Published: June 2020

Modern electron microscopes with lift- and tilt-stages allow small defect clusters in different samples to be investigated under nearly identical imaging conditions, especially with respect to magnification and excitation error. Taking advantage of these identical imaging conditions and applying statistical averages of may defects, it is possible to obtain very accurate mean sizes of defect clusters. Recent contrast calculations which consider both the depth positions and the actual sizes of the defects (l) make it possible to obtain the actual sizes of the observed defects from their images rather precisely. It is thus possible to detect very small changes in the mean cluster sizes as functions of different parameters, e.g., irradiation temperature Tirr at which the defects have been created, or their annealing treatment. Electron microscopy thus can provide data on the kinetics of point defects in addition to more conventional methods, e.g., resistivity-recovery and damage-rate measurements.

This paper reports on electron microscopy investigations on the temperature dependence of ion-damage in platinum.
Solute redistribution during in-situ irradiation of alloys in the high voltage electron microscope
Authors: Okamoto P. R. , Lam N.Q. , Lyles R. L.
Published: June 2020

During irradiation of thin foils in a high voltage electron microscope (HVEM) defect gradients will be set up between the foil surfaces and interior. In alloys defect gradients provide additional driving forces for solute diffusion since any preferential binding and/or exchange between solute atoms and mobile defects will couple a net flux of solute atoms to the defect fluxes. Thus, during irradiation large nonequilibrium compositional gradients can be produced near the foil surfaces in initially homogeneous alloys. A system of coupled reaction-rate and diffusion equations describing the build up of mobile defects and solute redistribution in thin foils and in a semi-infinite medium under charged-particle irradiation has been formulated. Spatially uniform and nonuniform damage production rates have been used to model solute segregation under electron and ion irradiation conditions.

An example calculation showing the time evolution of the solute concentration in a 2000 Å thick foil during electron irradiation is shown in Fig. 1.
Defects in ion implanted silicon
Authors: Lambert J.A. , Dobson P.S.
Published: June 2020

The defect structure of ion-implanted silicon, which has been annealed in the temperature range 800°C-1100°C, consists of extrinsic Frank faulted loops and perfect dislocation loops, together with‘rod like’ defects elongated along <110> directions. Various structures have been suggested for the elongated defects and it was argued that an extrinsically faulted Frank loop could undergo partial shear to yield an intrinsically faulted defect having a Burgers vector of 1/6 <411>.

This defect has been observed in boron implanted silicon (1015 B+ cm-2 40KeV) and a detailed contrast analysis has confirmed the proposed structure.
Amorphous Nb40ni60 produced by Ni+ ion implantation
Authors: Rechtin M. D. , Vander Sande J. , Baldo P. M.
Published: June 2020

Metallic glasses have recently evolved as an important new class of materials which can exhibit unexpected and highly desirable physical properties compared to their crystalline counterparts. Recent work on amorphous Nb40Ni60 has shown this alloy to have excellent resistance to displacement radiation damage effects to 900 K. This phenomenon, in conjunction with thermal stability to nearly 1000 K, and excellent mechanical hardness and strength, makes this refractory-transition metal alloy an attractive potential material for radiation environment applications. Some types of metallic glasses are available commercially as thin ribbons or filaments; however, the shape, size, and type of alloy available often limit their applications. In addition, ion implantation has been used to produce amorphous surface layers in some metal- metalloid systems such as Ni-P. This method of surface layer modification may be applied to unusual shapes and sizes.Furthermore, the thermal spike produced by ion implantation results in a cooling rate of ∽1014 K/sec in the vicinity of the collision cascade.
Electron microscopy study of plane matching (PM) secondary relaxations
in high angle grain boundaries
Authors: Schindler R. , Clemans J.E. , Balluffi R.W.
Published: June 2020

In many cases secondary grain boundary relaxations have been observed which appear as single sets of parallel lines under the electron microscope. In those cases stacks of identical and relatively low {hkl} planes in each of the two crystals adjoining the boundary intersect the boundary in sets of traces which almost match in spacing and direction. The subsequent relaxations then cause as much matching of the planes across the boundary as possible. The mismatch is forced into narrow bands (grain boundary dislocations) which bear a close relationship to the Moire pattern produced by the unrelaxed planar traces as pointed out by Pumphrey (l). Such boundaries have been frequently interpreted in terms of PM models which have been described and discussed by a number of investigators (2-5). In most PM models detailed atomic arrangements within the matching plane is ignored, and it is considered sufficient to match structureless planar sheets across the boundary without regard to atom matching along the planar edges.
Determination of crystal orientation by a zone axis method application to grain boundaries
Authors: Rocher A. , Fontaine C.
Published: June 2020

Several methods (1 → 3) have been proposed in order to determine by transmission electron microscopy (TEM) the orientation relationship between the crystal and the electron beam. The same type of method (4) has been used to find the orientation of a bicrystal. The most accurate ones (better than 0.1°) are based on the measurement of the relative position of Kikuchi lines with respect to diffraction spots. Such analysis are performed on diffraction pattern micrographs. The aim of the present work is to develop for TEM an in situ method for determination of the crystal orientation with respect to the goniometer coordinate frame, avoiding any analysis of the diffraction micrographs. The diffraction patterns used for this characterization are associated to the zone axis of the crystal. The method consists in plotting on the same stereographic projection the coordinate frame of the goniometer stage and the <100> axis of the crystal. These axis are determined from experimental indexation of three zone axis.
Preferred inclinations of <100> grain boundaries in epitaxially grown bicrystalline thin films of gold
Authors: Cosandey F. , Komem Y. , Bauer C. L.
Published: June 2020

Energy and concomitant structure of grain boundaries are related to inclination of the boundary plane as well as misorientation of grains defining the boundary. Although increasing information is becoming available on variation of grain boundary energy with misorientation, still relatively little is known about variation of grain boundary energy with inclination. The purpose of this research is to examine preferred inclinations of preselected grain boundaries in gold by transmission electron microscopy (TEM) in order to identify principal structural elements and to relate these elements to the energy of special grain boundary configurations.

Grain boundaries examined in this research are produced by a new technique involving vapor deposition of gold on common (001) surfaces of bicrystalline substrates of NaCl, characterized by preselected rotation about a common [001] axis, and subsequent epitaxial growth to form a bicrystalline thin film. These films are then removed from their substrates and examined by TEM. The principal advantage of this technique is that the grain boundary is formed during the deposition and growth process, thus resulting in a more perfect boundary structure while eliminating necessity of a separate bonding operation.
Decoration technique and surface physics
Authors: Bethge H.
Published: June 2020

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.

To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.
TEM study of the influence Of O2-pressure on the oxidation rate of pure aluminium foils
Authors: Kritzinger S. , Ronander E.
Published: June 2020

Initial stage oxidation of pure aluminium foils was studied by prismatic dislocation loop annealing. If the oxide film on a metal or alloy grows by the outward diffusion of the metal ions by either an interstitial or a vacancy mechanism through the oxide to the oxide/oxygen interface, vacancies are injected into the underlying matrix at the metal/oxide interface, creating a vacancy supersaturation in the matrix. The annealing rate of a prismatic loop, radius r and Burgers vector b, under the influence of a vacancy supersaturation, ΔC/Cₒ, is given by 1:

where E is a constant at a given temperature which involves the diffusion coefficient and geometrical factors, and the term αb/r is related to the line tension of the dislocation. If αb/r > (ΔC/Cₒ), the loop shrinks and vice versa. The rate of vacancy production due to oxidation can thus be studied by observing the growth or shrinkage rate of perfect loops in the transmission electron microscope, based on Eq. (1).
Oxidation of dilute Al-Mg foils in an O2-atmosphere as revealed by TEM
Authors: Kritzinger S. , Ronander E.
Published: June 2020

The thin film stage oxidation of Al-Mg in O2 was studied by TEM, utilising the prismatic dislocation loop annealing technique. Thin foils were prepared conventionally from oil-quenched sheets of Al-1.5 wt % Mg and oxidised ex situ in a special vacuum system1.

Generally it was found that oxidising at ∽ 170˚C and above, created a vacancy supersaturation large enough to cause prismatic loops to grow (Fig. 1). The growth rate increased with increasing O2-pressure. Even at 10-6 torr the larger loops still grew, while smaller ones shrank. Although a linear relationship between loop radius and annealing time was occasionally observed, the growth rate generally increased with time during an isothermal anneal at constant O2 partial pressure, and also varied from loop to loop. Small black spots appeared on almost all the micrographs after an annealing time of approximately half an hour and more (Fig. 2(a)).
SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system
Authors: Annamalai V. , Murr L.E.
Published: June 2020

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.

Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.

A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.
Quantitative X-ray analysis of thin samples in Tem
Authors: Pozsgai I. , Ilyinxx N.P.
Published: June 2020

The intensity of characteristic x-rays /IiX/ from thin self-supporting samples depends not only on the concentration /c/ of the excited element but also on the mass thickness /ƍD/ of the film:

The ki factors can be determined on thin etalon films of known thickness. So as to carry out quantitative analysis of thin samples, it is necessary to measure the local ƍ D independently of the measurement of x-ray intensities.

In this paper a method is described to determine the mass thickness of thin samples by electron transmission and their chemical composition by combining the x-ray intensity and electron transmission measurements.

It is known that some polycrystalline films e.g. Au, Ag, Sb, Bi and Cu films, exhibit anomalous behaviour in the exponential dependence of electron transmission on ƍD. Therefore we have developed a method for the measurement of electron transmission which overcomes the influence of Bragg reflection electrons.
Quantitative elemental analysis using an energy-dispersive X-ray spectrometer
Authors: Boom G. , Wolters G.H.J.
Published: June 2020

The input data for correction procedures (e.g. ZAF) are the individual intensities of elemental characteristic emission lines above Bremsstrahlung-background. In spectra obtained from biological specimens, peak-to-background ratios being O.2 - 1, different criteria for the determination of background-height under the peaks may result in vastly differing intensity data. Fig.l shows the results of six different processings of a single spectrum:(1) stripping of single G(aussian) peaks with user-specified (= fixed) energy-positions on the as-measured spectrum:(2) same but after spectrum-smoothing to reduce statistical scatter; (3) again single Gaussian-peak stripping but with least-squares fitting also along the energy-scale; (4) solving simultaneous equations for multiple Gaussians each with a user-specified (= fixed) energy-position using a straight line drawn between user-specified background-points as ‘ background-height’ (5)single gaussian-peak stripping with fixed positions, but after a frequency-filter background-calculation as used in the EDAX 7.EP-program; (6) as (5) but after a different frequency- filter calculation as used in the EDAX EMK-program.
Aspects of microanalysis in a transmission electron microscope
Authors: Sinclair R. , Jacobson B.E.
Published: June 2020

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.

X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3. Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).
Lateral resolution of the electron microbeam analysis
Authors: Dudek H.J.
Published: June 2020

The chemical inhomogenities in modern materials such as fibers, phases and inclusions, often have diameters in the region of one micrometer. Using electron microbeam analysis for the determination of the element concentrations one has to know the smallest possible diameter of such regions for a given accuracy of the quantitative analysis.

In th is paper the correction procedure for the quantitative electron microbeam analysis is extended to a spacial problem to determine the smallest possible measurements of a cylindrical particle P of high D (depth resolution) and diameter L (lateral resolution) embeded in a matrix M and which has to be analysed quantitative with the accuracy q. The mathematical accounts lead to the following form of the characteristic x-ray intens ity of the element i of a particle P embeded in the matrix M in relation to the intensity of a standard S
A quantitative investigation of thin specimen X-ray spectra in the TEM
Authors: Robertson B.W. , Chapman J.N. , Nicholson W.A.P. , Ferrier R.P.
Published: June 2020

In electron probe x-ray microanalysis, the observed x-ray spectra are degraded by the presence of both characteristic and bremsstrahlung x-rays from the regions of the specimen which are not under analysis and from the solid materials near the specimen. These x-rays are generated by electrons scattered from the probe by the specimen and by stray electrons originally outside the probe. The extraneous bremsstrahlung x-rays form a component of the observed continuum which is only indirectly dependent on the nature of the specimen. This effect is particularly undesirable in the analysis of thin biological specimens in the transmission electron microscope since the continuum level is commonly used in quantitative analysis as a measure of specimen mass thickness. Experiments have therefore been performed to investigate the magnitude of the extraneous radiation and to evaluate the success of attempts to reduce it. These have been detailed elsewhere (Nicholson et al. 1977).
Phase determination from superposed diffraction patterns
Authors: Kunath W.
Published: June 2020

The strong prefield of the single-field condenser-objective permits the demagnified imaging of a small field-1imiting aperture stop and thus diffraction from small crystalline areas [1], An additional biprism within the field-1imiting aperture splits the beam, resulting in two coherent plane waves in the crystal plane. Both waves produce a diffraction pattern which, in principle, can--by properly adjusting the biprism-- be superposed coherently in such a way that every two spots of different diffraction order interfere (Fig. 1). This allows the phase determination of structure factors [2]. Quantitative considerations and difficulties are reported.

In order to get sufficient information for the phases at least two exposures are needed with a relative translation of the source opposite to the crystal between them. Recently, encouraging light optical experiments have been performed with an extended source resulting in extended diffraction spots with intensity modulations (Fig. 2). The simplest model for explaining these modulations is shown in Fig. 3.
Intercalation of layer structures in the T. E. M. - modified charge density waves or artefacts?
Authors: Tat Lock G.J.
Published: June 2020

Periodic lattice distortions (PLD) linked to charge density waves have been shown to give rise to the formation of a variety of superlattices in the diffraction patterns of layer structures. Foreign atoms or molecules may also be inserted in the Van der Waals gaps in these materials by intercalation and this changes the form of the observed superlattices. In this paper we present new experimental results for the in situ intercalation of a variety of layer structures with hydrazine (N2H4) in the electron microscope. Although these results are interpreted in terms of scattering from modified PLD, it is suggested that some previously published results should be reinterpreted in terms of double diffraction between rotated crystallites or other artefacts.

Layer structures such as TaS2 or NbSe2 may exist in a variety of polytypes depending on the stacking of the layers along the c axis.
Kikuchi patterns of a non-centrosymmetrical crystal: tellurium
Authors: Le Goff J.-J. , Faivre G.
Published: June 2020

Kikuchi patterns of crystals of low-symmetry exhibit features which cannot be observed in common crystals. Two kinds of effects have been studied on Te crystals ; these crystals have a 3 atoms basis and belong to the enantiomotphous space-groups D3(fig- 1).

1. “UNUSUAL” BANDS

Systematic diffractions may be classified according to the profile of their Kikuchi band at 100 kV.

In the “usual” case, to which the quasi-totality of the diffractions belong, the band at 100 kV has its principal maxima near the first Bragg position (at ± ) and has no central maximum (at the O-position). We call this type of diffractions A-type.

For the “unusual” cases, we define two extreme situations which have been observed in Te (fig. 3 and 4) :

(i) A'-type [Te-]. The band presents at 100 kV a profile similar to those which are observed at higher voltage for diffractions of the “usual” type : a strong central maximum and principal maxima at n (n >1).
Dynamic studies of the deformation & fracture of pearlite using 200 Kv SEM
Authors: Porter D.A. , Easterling K.E. , Smith G.D.W.
Published: June 2020

A Jeol 200 kV STEM equipped with a tensile deformation stage, a secondaray electron detector and a video recording chain has been used as a high voltage SEM to study in situ the deformation and fracture of miniature tensile specimens of pearlite. The advantage with high voltage SEM is that the increased gun brightness, compared with conventional SEMs, provides an improvement in resolution for a given signal/noise ratio and therefore allows higher magnifications to be used during the recording of dynamic deformation sequences at TV scanning rates. This facility proved to be essential for the TV monitoring of pearlites at the finest interlamellar spacings. The influence of interlamellar spacing on the mechanisms of deformation was of particular interest in this study and the materials examined ranged from coarse pearlite, with a mean interlamellar spacing λ ⁓ 0.4 μm, to fine pearlite with λ ⁓ 0.1 μm,. The problems of ex post facto reasoning regarding the modes of deformation were avoided by continuously following deformation with the TV monitor and recording high resolution slow scan micrographs from the same area both before and after straining.
In Situstudies of fracture in solids
Authors: Narayan J. , Ohr S. M.
Published: June 2020

Problems of crack nucleation and propagation associated with fracture in solids have been the subject of numerous experimental and theoretical investigations in the past, but the basic mechanism of the phenomena is not well understood at present. One of the difficulties stems from the fact that detailed microscopic information on the physical processes occurring at the crack tip is lacking. This is particularly true with respect to the formation of plastic zones involving the generation and motion of dislocations. In the present study, we have examined by transmission electron microscopy the propagation of cracks duringin situtensile deformation of stainless steel, molybdenum and magnesium oxide representing ductile, semi-brittle and brittle solids.

Single crystal specimens suitable for electron transmission were prepared by dimpling and polishing from one side. With this geometry, the specimens could be deformed in pure tension in a bending holder. As the stress was applied, the cracks were initiated at the edge of the holes in the thinned foils.
Adhesion in metal cutting: a study in the SEM
Authors: Silva V.M. , Doyle E.D.
Published: June 2020

In a recent review of friction in metal cutting Bailey (1) claimed that it was now almost universally accepted that there was seizure or sticking contact between the chip and the tool in the immediate vicinity of the cutting edge, as indicated schematically in Fig. 1. This conclusion is rationalised on the basis that the sliding contact involves the continual generation of an uncontaminated chip surface at the cutting edge and that there is intimate contact between the chip and tool because of the high normal pressures on the rake face. However, recent work by Home et al. (2) using a transparent sapphire tool, revealed that the chip moves up the rake face of the cutting tool with no apparent seizure contact in the region of the cutting edge. In order to provide additional insight into this problem we have video-recorded the dynamic events in machining by carrying out the chip forming process within the evacuated chamber of the scanning electron microscope.
Use of 2½ D imaging in analysis of NiTi martensite
Authors: Michal G. M.
Published: June 2020

Several TEM investigations have attempted to correlate the structural characteristics to the unusual shape memory effect in NiTi, the consensus being the essence of the memory effect is ostensible manifest in the structure of NiTi transforming martensitic- ally from a B2 ordered lattice to a low temperature monoclinic phase. Commensurate with the low symmetry of the martensite phase, many variants may form from the B2 lattice explaining the very complex transformed microstructure. The microstructure may also be complicated by the enhanced formation of oxide or hydride phases and precipitation of intermetallic compounds by electron beam exposure. Variants are typically found in selfaccommodation groups with members of a group internally twinned and the twins themselves are often observed to be internally twinned. Often the most salient feature of a group of variants is their close clustering around a given orientation. Analysis of such orientation relationships may be a key to determining the nature of the reaction path that gives the transformation its apparently perfect reversibility.
High temperature studies of steels in the photo-emission electron microscope
Authors: Burnett B. , Parker K.E. , Baker A.J.
Published: June 2020

The Photo-Emission Electron Microscope (PEEM) provides a unique facility for the direct examination of high temperature metallurgical reactions. However, considerable experience and care is required in the interpretation of the images obtained since they differ greatly from those produced in other types of electron microscopy. Furthermore, the morphology of products and the rates of reactions may be influenced by the fact that they occur at the free surface of a material. These effects are particularly important in the study of precipitation reactions in steels, where the interpretation of features of the image involves a consideration of the interplay between solute supersaturation, surface orientation and surface reactivity. A Balzers KE3 PEEM has been used to examine the behaviour of a variety of experimental and commercial alloy steels under high temperature conditions.

Figure 1 illustrates the precipitation of an alloy carbide from austenite at low supersaturation. The precipitate is V5C6 and has formed at 850°C during cooling at 5°C/min from the 1050° C solution treatment temperature.
The use of STEM microdiffraction for the study of misorientation between subgrains
Authors: Ball M. D. , Morris P. L.
Published: June 2020

While there have been studies of the relationship between misorientation in worked structures and the development of recrystallisation nuclei, most have lacked accuracy owing to the positional uncertainty of selected area diffraction. However the fine electron probe forming capability required for STEM operation enables diffraction information to be obtained from regions of the order of 20 nm or less in diameter. We have applied this technique to an examination of recrystallisation in situ, where the early stages of grain development are arrested by the presence of particles.

The microdiffraction studies were carried out on specimens prepared from an Al-6% Ni alloy which had been given various rolling and annealing treatments. A JEOL JEM 100C/ASID-4D electron microscope was used in the STEM mode with the operating conditions such that the spot size was about 20 nm with a beam divergence of 10-3 rad.For each of the specimens studied, a suitably thin region with a typical subgrain structure was selected and photographed.
Studies of precipitate rich-zones on grain boundaries of Al-Mg-Si alloys after aging
Authors: Pirš Jože , Pavlin Marija
Published: June 2020

In most age-hardening aluminum alloys, metallographic studies have shown that the extent of precipitation adjacent to grain boundaries is much less than that which occurs in the interior of the grains. The width of these almost precipitate-free regions, which are sometimes called denuded zones, and the extent of solute depletion with them are dependent upon the particular alloy and its aging treatment. It has been observed that these zones are relatively soft with the result that plastic deformation takes place preferentially within them. It has been shown 2-4 that there exists a tendency for intercrystalline cracking in fatigue when such zones are present. It is of interest to note that Broom et al. were able to reduce the incidence of this type of failure in an Al- 4 wt pct Cu alloy by stretching the material 10 pct prior to aging. This was later confirmed also on Al - 10 wt pct Mg alloy.
Structure and crystallization of amorphous metal oxide films
Authors: Shiojiri M. , Miyano T. , Kaito C.
Published: June 2020

High resolution electron microscopic observations have been made on amorphous and crystalline metal oxide films. The specimen films were prepared by vacuum-evaporation of metal oxide powder from alumina coated tungsten basket onto clean glass substrates at room temperature. The films were deposited to a thickness of 100 Å, monitored with quartz crystal oscillating microbalance. The films were wet-stripped from the substrates and then mounted on gold holey films which were supported by standard gold electron microscope grids. Transmission electron micrographs were taken with JEM 100-C electron microscope under axial illumination. The microscope was equipped with an objective lens with Cs=1.8 mm and operated at 100 kV.

Figure 1 shows an electron micrograph and an electron diffraction pattern of as-deposited WO3 film. The thickness of the film is assumed to be less than 50 Å, since the 100 Å thick film was floated on the distilled water for 20 minutes for thinning by dissolution.
Structure of chromium-chromium oxide films
Authors: Smith P. J. , Wildman H. S. , Wilson H.
Published: June 2020

The percentage of chromium oxide in chromium films has been measured by Auger spectroscopy and related to structure and to electrical properties. Previous work had shown that depositing chromium films in increasing partial pressures of oxygen caused increases in resistivity and decreases in the temperature coefficient of resistivity (TCR).

Blanket chromium films, 1200Å thick, were deposited on SiO2. The system was evacuated into the 10-7 Torr range and backfilled with water vapor to produce films containing from 1% to 30% of chromium oxide. The volume percentage was determined by profiling the oxygen and chromium in each film by Auger spectroscopy (assuming that all the oxygen was present as Cr2O3) and averaging over the thickness of the film. The TCR, measured in the temperature range 60°-160°C, was found to vary linearly with oxide content in the range from 5% to 30%.

The TCR was +370 ppm/°C for a film with 2% oxide, whereas it was reported as +1200 ppm/°C for ultrahigh vacuum chromium.
Propane-jet freezing of muscle fibers for freeze fracture
Authors: Cantino M. E. , Pollack G. H.
Published: June 2020

Recent advances in freezing techniques have intensified interest in freeze fracture for the study of nonmembranous cellular structures. We describe here a method for freezing single skinned (demembranated) muscle fibers in a dual propane jet freezing device.

The freezing apparatus we used, developed by J. Gilkey and A. Staehelin (Univ. of Colo.), is based on the design by Müller. To adapt this device to studies of skinned relaxed and activated muscle fibers, we built the sample holder shown in Figure 1. The holder is separable into two parts (at the arrow) to allow mounting of fibers under relaxing solution. A modified Balzers freeze fracture support, with the back hollowed out and a groove milled in the top (figure 2) is placed between the hooks. A skinned frog semitendinosus fiber (F) is mounted over the support, between the fixed hook (right) and the moving hook (left). Fiber length is adjusted by moving the lever (L). To activate samples, the holder is removed from the bath and several drops of activating solution (relaxing solution plus calcium) are flooded over the fiber.
Glomangioma of the sella turcica
Authors: Asa S. L. , Horvath E. , Kovacs K. , Ezrin C. , Weiss M. H.
Published: June 2020

Glomangiomas arise from specialized smooth muscle cells surrounding arteriovenous anastomoses (1), and occur most commonly in the sites where glomera are numerous, especially in the skin of nail beds, hands and feet. We report here a glomangioma in an unusual site, the sella turcica.

A 42-year-old man complained of headaches and decreased visual acuity. Investigations revealed an intrasellar tumor with upward extension. There was no evidence of hormonal abnormality. After partial operative resection of the tumor, radiation therapy was administered. Two further surgical procedures were required for relief of symptoms caused by recurrent tumor.

By light microscopy, the tumor was composed of sheets of epithelial cells and vascular channels lined by flat endothelium. Tumor cells had round, vesicular nuclei and homogeneous acidophilic cytoplasm. Mitotic figures were rare.
Ultrastructural effects of combined hematoporphyrin derivative (HpD) and phototherapy on bladder transitional cell carcinoma
Authors: Shulok J. R. , Klaunig J. E. , Selman S. H. , Schafer P. , Goldblatt P. J.
Published: June 2020

Hematoporphyrin derivative (HpD) is a mixture of porphyrins possessing tumor localizing and photosensitizing properties. This compound has been examined in both animal models and in human clinical trials for the treatment of a variety of neoplasms. Although the treatment appears effective, many questions remain concerning the mechanism of action of hematoporphyrin derivative. This study examined the ultrastructural effects of combined HpD and phototherapy on a transplanted rat transitional cell tumor.

Four week old Fischer F-344 rats were subcutaneously injected with 1x106 viable AY27 cells (a rat bladder transitional cell carcinoma line). The resulting tumors were grown to 1 cm3 in size at which time each rat was given a single tail vein injection of 10 ug HpD/gram body weight. After 24 hrs. tumors were irradiated with light (630 nm; 200 mW/cm3) for 30 min. Treated tumors were sampled at 0, 0.5, 1, 4, and 24 hrs. post-phototherapy and processed for transmission electron microscopy. Additional rats with tumors were treated with either HpD only, light only, or nothing.
Preparation of diagnostic specimens for transmission electron microscopy
Authors: Harb Joseph M.
Published: June 2020

Several factors influence the selection of preparatory procedures for diagnostic TEM. These include variability of specimens, lack of accessibility to additional specimens, and the need for expeditious turn-around time and technical reliability. Specimens encountered in a diagnostic laboratory may include peripheral blood huffy coats and bone marrows, biopsies of liver, muscle, nerve, skin, kidney, lung and other organs, and a variety of tumors. It would be desirable for optimal preservation to employ a dehydration and embeddment schedule designed specifically for each specimen type, but such a practice in a diagnostic setting would seriously multiply the specimen handling steps and preclude simultaneous processing of different specimen types. Such a practice could also induce errors and increase the technical workload, which could have a negative effect on cost containment. Therefore, generalization of the preparatory schedule and selection of an embedding medium which will adequately preserve ultrastructural details for a wide range of specimens is appropriate.
Morphometry in pathology
Authors: Dardick Irving
Published: June 2020

As medical sciences strive to make observations more precise, pathologists are becoming interested in objective histological and cytological evaluation. Morphometry is one procedure for deriving objective data, and measurements and statistical analysis of cell, nuclear or tissue parameters can be made with relatively inexpensive equipment. We are currently using an Apple II Plus microcomputer, a digitizing tablet (GTCO Corporation, Rockville, Md.) and a morphometric analysis system software diskette (Atlantis Scientific Systems Group Inc., Ottawa, Canada).

Increasing numbers of reports of morphometric studies in pathology are appearing in the literature. Comparative analysis of nuclear shape of lymphocytes in mycosis fungoides and chronic dermatoses and measurements of microvillous length in mesotheliomas and adenocarcinomas show the value of this technique.
Aspiration cytology and transmission electron microscopy (TEM): A novel tissue-collection technique with useful diagnostic applications
Authors: Maksem J.A. , VanDyke C. , Carter H.W. , Galang C.F.
Published: June 2020

In the last decade fine needle aspiraration biopsy has gained recognition as a valuable diagnostic technique, and its benefits have been demonstrated in large series of patients with almost every type of tumor (1,2). The usual way to collect cellular material from needle-aspiration biopsies is to discharge the needle and syringe contents onto a microscopic slide and smear the material with another slide. The entire specimen is contained on the slides prepared at the time of biopsy. Serious technical difficulties are inherent to this method. 1) Inconsistent fixation, 2) drying artifact, 3) loss of tissue fragments, 4) inability to confirm impressions by a “second method”, and 5) retention of significant diagnostic material in the needle hub. Our technique avoids these difficulties.
Functional reconstitution of lens junction proteins into proteoliposomes
Authors: Nikaido Hiroshi , Rosenberg Emiko Y.
Published: June 2020

Many cells in animal tissues are connected together through “communicative junctions”, such as gap junctions, and protein oligomers (sometimes called connexons) with an apparent central channel have been isolated from the regions of liver plasma membrane enriched in such junctions. Although ingenious approaches such as dye injections have been used to characterize the properties of the channel, to our knowledge there has been no report of direct reconstitution studies of the type widely used with bacterial channelforming protein, porin, or with its analog from the mitochondrial outer membrane, mitochondrial porin.

More recently, membranes from lens fiber have been studied intensively, because they contain a large abundance of one protein, which appears to be the subunit of intercellular junctions. However, the subunits of the lens junction is different from those of liver gap junctions in its molecular weight, peptide map pattern, and immunological specificity.
Structural biochemistry: Correlation of structure and function at the molecular level by use of electron microscopy
Authors: Fowler Walter E.
Published: June 2020

Visualization of single, purified molecules often provides a valuable context in which to correlate physical chemical, biochemical and functional properties. For example, the apparent shape of a protein molecule in the electron microscope may allow estimation of the relative contributions of molecular asymmetry and hydration, which are difficult to distinguish by hydrodynamic methods, as well as assessment of molecular flexibility. Such ‘molecular microscopy’ can also be used to identify different subunits and structural or functional domains within a given molecule, e.g. by comparing the appearence of proteolytic fragments with that of the intact molecule or by ‘labelling’ the intact molecule with ligands specific for different functional sites. Intermolecular complexes consisting of molecules that interact in vivo can also be studied in the electron microscope, provided the complexes are or can be made sufficiently stable.
Complex serine proteases and associated regulatory elements in the human complement system: A transmission EM study
Authors: Smith Craig A.
Published: June 2020

An unusual negative staining method for TEM of biological macromolecules, termed the pleated sheet technique, has been exploited to study the molecular architecture of two sets of functionally similar bimolecular serine proteases and their regulatory elements of human complement. In this technique, macromolecules are adsorbed to a carbon film by the Valentine procedure and the film subsequently pleated while in contact with a 1% uranyl formate solution to trap stain with sample in the folds of pleats. A 400 mesh copper grid is placed on the compressed film, and film plus grid retrieved with a Saran Wrap drum. Subsequent dehydration produces a filmed grid containing negatively stained macromolecules within pleated regions and positively stained macromolecules in single sheet regions (Fig. 1A, 1B). The effect of sandwhiching sample and stain between carbon layers is to produce exceedingly uniform negative staining so that stain contours more accurately and more reproducibly reflect true molecular contours.
RNA polymerase: Preparation and structural analysis of helical polymers
Authors: Loren Buhle E. , Rew Pamela , Aebi Ueli
Published: June 2020

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.
Labeling of macromolecular assemblies with undecagold clusters
Authors: Kuhn Evelyn , Fuchs Mindy , Varkey Jacob , Beer Michael , Yang Heechung , Frey Perry
Published: June 2020

In many areas of Molecular Biology the arrangement of macromolecules in a complex assembly must be determined. This might be done if a component of interest can be labeled with a detectable marker. Recently we used the STEM and single platinum atoms to find the positions of histones in nucleosomes. This approach is limited by the difficulty of imaging single atoms and the need to use destructively high electron doses. We report preliminary results on the use of the large Undecagold clusters which promise to alleviate these problems. The compound was first prepared by Bartlett et al. and has been used by Wall and his co-workers on the Brookhaven STEM. Recently Frey and his collaborators have developed techniques for chemically manipulating them.
Nucleosome reconstruction by electron spectroscopic imaging of phosphorus
Authors: Ottensmeyer F.P. , Harauz G.
Published: June 2020

The three dimensional structure of a biological macromolecule or complex can be reconstructed from electron micrographs of different macromolecules or complexes lying in random orientation, provided that the relative orientations of individual particles can be determined (figure 1). In the case of the nucleosome core particle, a complex comprising 146 base pairs of DNA and 8 histone proteins, such orientational information can be obtained using a new technique called electron spectroscopic imaging which permits not only electron microscopy of the structure, but also the visualisation at high spatial resolution of the phosphorus distribution within the particle. Since phosphorus is a predominant constituent of DNA and not of protein, this elemental map represents an image of the nucleosomal DNA component. A comparison of a projection of a DNA supercoil model with images of the phosphorus distribution allowed us to orient individual distributions (figure 2). Using a direct convolution back-projection algorithm, the entire nucleosome containing both protein and DNA information was then reconstructed to a resolution of about 1.5 nm.
Visualizing protein molecules and assemblies with the quick-freeze/mica approach
Authors: Ip Wallace
Published: June 2020

The transition from an image of the isolated protein molecule to that of the in vivo structure is not always straightforward, and very often it is further complicated by the fact that images of the two states have to be obtained by different preparative EM techniques. Negative staining, which perhaps has contributed more to the understanding of macromolecular structure than any other EM technique, provides wonderfully detailed images of many isolated proteins in the size range of 6-100 nm, but cannot be used to visualize whole cells or even cell fragments with comparable results. The glycerol spray/mica technique (1,2,3) also provides striking views of isolated molecules but is again restricted to such specimens. The quickfreeze, deep-etch technique (4) as routinely practiced suffers from the converse problem in that it images cellular organelles with unusual clarity but does not work with suspensions of macromolecules because they clump or collapse during the deep-etching step.