bluuebunny/crossref_metadata_2025 huggingface dataset:
Hardening Effect and Electron Metallography of Precipitation in Uranium with Small Additions of Titanium
Authors: Johnson D. H. , Ammons A. M.
Published: June 2020

Uranium-0.5 wt.% titanium and U-1.0 wt.% Ti alloys are alpha-phase, martensitic uranium alloys which show large increases in strength due to precipitation of U2Ti on aging at moderate temperatures. Hardness, electron microscopy, and X-ray diffraction were used to study growth kinetics of the U2Ti precipitation and the precipitate-matrix interactions.

The alloys were induction melted from high-purity uranium and sponge titanium in a zirconia-coated graphite crucible and bottom poured into a zirconia-coated mold; subsequently, the alloys were solution treated at 800°C for one hour in a vacuum of 5 x 10-6 torr and water quenched. Small specimens were then heat treated at temperature in a vacuum of 5 x 10-6 torr and water quenched.

Thin foils were prepared by a modification of the two-step electrothinning procedure of DuBose and Stiegler from rods using 15 volume percent perchloric acid and 35 volume percent butyl cellosolve in methanol for initial thinning and a bath of 6 volume percent perchloric acid cooled with a dry ice-acetone mixture for the final electropolishing.
Martensite Transformation in β-NiAl
Authors: Mohanty G. P. , Rath B. B.
Published: June 2020

We present in this report some results of a study of the martensite transformation in the Ni-rich β-NiAl alloys. This transformation, first reported by Maxwell and Garla, has since been confirmed by several recent studies. Samples for the present study were prepared by vacuum-induction melting of the high purity elements with a nominal Al-68%Ni composition. Under equilibrium conditions, this alloy consists of single β-phase above 1350°C and a two-phase mixture of β and Ni3Al below this temperature. Martensitic transformation was introduced by quenching small rectangular-shaped samples in iced brine from above 1350°C, following equilibration in the β-range. The quenched samples were appreciably harder than the slow-cooled samples (770 vs. 390 VHN) and showed the typical acicular surface microstructure, shear markings within the grains, and often sharp steps at the grain boundaries, thus giving them a jagged appearance.
Comparison of Deterministic and Linear Cosine Spatial Filtering of Transmission Electron Micrographs
Authors: Ansley David A.
Published: June 2020

The coherence of the electron flux of a transmission electron microscope (TEM) limits the direct application of deconvolution techniques which have been used successfully on unmanned spacecraft programs. The theory assumes noncoherent illumination. Deconvolution of a TEM micrograph will, therefore, in general produce spurious detail rather than improved resolution.

A primary goal of our research is to study the performance of several types of linear spatial filters as a function of specimen contrast, phase, and coherence. We have, therefore, developed a one-dimensional analysis and plotting program to simulate a wide 'range of operating conditions of the TEM, including adjustment of the:

(1) Specimen amplitude, phase, and separation

(2) Illumination wavelength, half-angle, and tilt

(3) Objective lens focal length and aperture width

(4) Spherical aberration, defocus, and chromatic aberration focus shift

(5) Detector gamma, additive, and multiplicative noise constants

(6) Type of spatial filter: linear cosine, linear sine, or deterministic
Comparison of Simulated Images With Electron Images of Lactic Dehydrogenase
Authors: Fiskin A. Max , Mack Patricia
Published: June 2020

Comparison of negative stain images of glutamate dehydrogenase (GDH) with shadow projections of opaque models has revealed that this approach can be misleading. We have suggested an x-ray simulation procedure in which the influence on the image of disruption of oligomer, finite metal-ion complex size, and depth of the stain layer are simulated under controlled conditions, and have deduced a model of GDH quaternary structure using this procedure.

Here the accuracy of procedure suggested above is tested by comparing micrographs of rabbit muscle lactic dehydrogenase (LDH) with simulated images obtained with a model of dogfish LDH constructed in accord with x-ray diffraction data. The dogfish and rabbit muscle LDH's exhibit extensive sequence homology, are each composed of four subunits, and have nearly identical molecular weights. Dogfish LDH exhibits 222 symmetry and the shape of the oligomer approximates a parallelepiped.
Construction and Application of Environmental Cell
Authors: Fukami A. , Katoh M.
Published: June 2020

The key points of constructing an environmental cell are an environmental window frame which transmits electron beam from vacuum to the cell, and an environmental window film put on the frame.

From our experimental results, the window frame is made from a copper aperture having a 300 μmϕ hole covered with a copper screen having 40 μmϕ holes, and the window film is made from doubly vacuum-evaporated film which consists of carbon layer (350 Å in thickness, facing to vacuum side) and silica or silicon carbide layer (150 Å, facing to atmospheric side), using the micro grid technique developed by us). Carbon layer has high mechanical strength against to the difference in pressure between in and out of the cell (0.01 to 760 Torr.), and silica or silicon carbide layer has desirable durability for electron irradiation in gases. The thickness of atmospheric space is controled by a spacer (10 to 200 μm), and a specimen is generally put on the window film facing to the objective lens.
Formation of Dislocation Channels in Neutron Irradiated Molybdenum
Authors: Mahajan S.
Published: June 2020

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.

Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.
Preferential Sputtering of Ni3Al Single Crystals Studied Using Atom-Probe Field-Ion Microscopy and XPS
Authors: Thomas M.P. , Waugh A.R. , Southon M.J. , Ralph Brian
Published: June 2020

It is well known that ion-induced sputtering from numerous multicomponent targets results in marked changes in surface composition (1). Preferential removal of one component results in surface enrichment in the less easily removed species. In this investigation, a time-of-flight atom-probe field-ion microscope A.P. together with X-ray photoelectron spectroscopy XPS have been used to monitor alterations in surface composition of Ni3Al single crystals under argon ion bombardment. The A.P. has been chosen for this investigation because of its ability using field evaporation to depth profile through a sputtered surface without the need for further ion sputtering. Incident ion energy and ion dose have been selected to reflect conditions widely used in surface analytical techniques for cleaning and depth-profiling of samples, typically 3keV and 1018 - 1020 ion m-2.
Reduction of Radiation Damage in Organics by Cooling to 4K and Embedding
Authors: Knapek E. , Formanek H. , Lefranc G. , Dietrich I.
Published: June 2020

Structure determination of organic, in particular biological, material is performed with x-ray methods, if sufficiently large crystals are available. In the case of small periodic regions a good tool is electron diffraction. However, the information gained with this method will in general hardly do. The necessary additional data can be obtained e.g. by direct imaging with the electron microscope. Unfortunately structure changes due to the electron impact make imaging very difficult with a resolution below 20 Å. Recently it has been established that radiation damage can be drastically reduced by cooling the specimen to 4 K1 or by embedding it in an amorphous matrix. In the following the radiation protection achieved by combining both methods is shown on the example of the organic complex Cu-bis-salicyloylhydracin (Cu-BSH) which is interesting for cable technology.

The specimens are prepared by solving BSH in NH3 and subsequently adding copper tretamin solution. The needle-shaped crystals which precipitate are spread on holey carbon foil (Fig. 1). Diffraction patterns were taken at room temperature and at 4 K.
TEM Characterization of Aged Ti-5Al-2.5Sn Powder Metallurgy Alloys with Si and with Ge Additions
Authors: Jackson A. G. , Omlor R. E. , Froes R. H. , Moteff J.
Published: June 2020

Titanium alloys produced by the powder metallurgy (PM) techniques are of interest because of the potential cost savings and property enhancement above that possible by conventional ingot metallurgy approaches. In the present program the Ti-5Al-2.5Sn alloy, an all alpha system, is being studied as a model PM titanium alloy. Alloying additions of Si and Ge, which normally result in coarse precipitate regions in cast and wrought material because of their low solubility, have been made. The PM products circumvent the ingot problem because segregation is avoided and precipitates are retained in solution by either the rapid quench rate (pre-alloyed powder) or homogeneous mixing (elemental blend approach). The resulting product displays structures and behavior which differ from conventional Ti-5Al-2.5Sn product. To date Ti-5Al-2.5Sn PM alloys with 0.5 Si and with 1.0Ge w/o have been prepared by an elemental blend/cold compact/sinter process, followed by Hot Isotatic Pressing (HIP'ing). Subsequently specimens were aged at 1000°F (540°C) for 3, 66, and 500 hours in order to precipitate silicides and germanides. Thin foils were then prepared and characterized using TEM and STEM techniques.
Applications of In-Situ Electron Microscopy in Catalysis
Authors: Gai P.L. , Goringe M.J.
Published: June 2020

Controlled reduction and oxidation reaction experiments on metal oxide catalysts, sulphides, and iron-titanium oxide minerals have been conducted in an environmental (or gas reaction) cell fitted to an AEI-EM7 high voltage electron microscope operating at 1MV. With this technique it is possible to observe dynamic heterogeneous reactions using gas pressures in the range from a few torr to an atmosphere, and temperatures from room temp, to ∼1000°C. A full dynamic description of the behaviour of the solid with respect to temperature, pressure, gaseous environments can therefore be obtained. These observations are useful in understanding mechanisms of heterogeneous catalysis, redox processes, and migration of the reduced species, which affect catalyst selectivity and activity. Examples of some in-situ reactions have been reported in the literature.
Platinum-TiO2 (Rutile) Substrate Interaction During Cyclic Oxidation-Reduction Heat-Treatment
Authors: Shinozaki S. , Donlon W. T. , Meitzler A. H.
Published: June 2020

When polycrystalline TiO2 (rutile) pellets (∼1mm in thickness and ∼3 mm in diameter), dispersed with Pt particles to act as a catalyst, were heat-treated under certain conditions involving an applied electric field, new unusual microstructures were formed. The heat-treatment procedure was, as follows: 1) apply 1 volt dc field between two Pt electrodes inbedded into the pellet, 2) heat the sample to 750°C and begin cycling the sample between oxydizing (4% O2 in N2) and reducing (2% CO in N2) atmospheres at a rate of several cycles per hour, 3) lower the temperature to 600°C while continually cycling (200 cycle), and, 4) cool the sample to room temperature under the reducing atmosphere (1). The pellet was ion milled to a proper electron transparency and examined by means of a Siemens EM102 and a Philips EM400 TEM-STEM microscope.

Some TiO2 grains in this sample exhibited no resolvable defect structure, except that the matrix appeared to be strained due to small defects (Fig. la).
Interpretation of High Resolution Lattice Image of Thick Crystal
Authors: Ishizuka K. , Iijima S.
Published: June 2020

A wealth of information on structural details in the images of thick crystals has been demonstrated. This paper is concerned with interpretation of the HREM images of thick crystals.

To save the cost of the HREM image calculation, a computation method for the multislice formulation will be economical. Our previous studies of a crystal of niobium oxides showed that the HREM images appearing in thin regions recurred in thicker regions (Fig. 1). The simulation of this recurrence would be a measure to judge the validity of the calculation. The calculated amplitudes for some beams contributing to the image are shown in Fig. 2. The HREM images corresponding to the thicknesses indicated in Fig. 2 are simulated using our experimental parameters. The recurrence of the image is reproduced clearly in this calculation (Fig. 1). The result is encouraging for the analysis of thick crystals in terms of their structural details.
Observations of Pt-Ir on Al2O3 Catalysts Using a Fast Digital System Controlled STEM
Authors: Butler J. H.
Published: June 2020

The familiar Scanning Transmission Electron Microscope (STEM) technique of Z-contrast, used to image heavy atoms on amorphous supports, can be applied to the study of metal catalysts with only partial success. The contrast is reduced when crystalline systems are studied since a Bragg contribution is introduced in the standard annular dark-field collector. At large angles, the Bragg reflections diminish due to thermal vibrations; and the scattering cross section is approximately proportional to Z2. Thus scattering in this region is predominately Rutherford-like. The atomic number dependence of this high angle detectoro (HAD) signal makes it particularly suited for identifying small (20-50Å diameter) catalyst particles suspended in polycrystal line alumina.

The experimental configuration for this imaging mode suggests concurrent acquisition of the HAD signal and the corresponding bright field signal , as on-line arithmetic of the two is necessary to optimize image contrast. In the conventional STEM it is impossible to detect the HAD signal because it is cut off by the specimen cartridge. Treacy, et al. have developed a sophisticated method for obtaining these signals.
Flash Tube Radiation Annealing of BF2-Implanted Silicon
Authors: Chen L. J. , Lu L. Z. , Lue J. T.
Published: June 2020

Laser and electron beam annealing of ion-implanted semiconductor are currently of great interest as alternatives to thermal annealing. It is known that unconventional annealings are essentially extensions of thermally induced recovery and regrowth processes which are dependent on power density, annealing time and energy balance. The annealing mechanism does not seem to depend on the coherence of the source. Any source capable of applying short and intense heat pulses should suffice for rapid annealing. For large areas processing and economic considerations, a high power density, short pulse flash tube radiation annealing may be more advantageous than other unconventional annealing methods. With appropriate control, light pulses from flash tube heat up the surface layer of ion-implanted silicon very rapidly and may anneal out the damage or recrystallize the amorphous layer.

Two inches in diameter and about 10 mil in thickness wafers of 3-5 Ω-cm, phosphorus doped, (001) and (111) oriented silicon were implanted at room temperature with 100 keV BF+2 ions to doses of 1 x 1014 to 1 x lO16/cm2. A demountable flash tube was used to anneal the samples with 100 μsec FWHM pulses and energy density (ED) ranging from 19.6 to 41.1 J/cm2. The fill pressure of air was kept beloe 30 torr. Optical and scanning electron microscopy (OM and SEM) were used to study the changes of silicon surface after annealing. Transmission electron microscopy (TEM) was performed to investigate the microstructural changes. Four point probe method was applied to measure the sheet resistivity.
Application of TEM to the Characterisation of Commercial BaTiO3 Capacitors
Authors: Mecartney M. L.
Published: June 2020

Ferroelectric BaTiO3 with its high dielectric constant is a material widely used for miniature high capacitance capacitors. Pure BaTiO3 has the perovskite crystal structure (cubic) above 120°C and undergoes a phase transformation to a ferroelectric state at 120°C: the electric dipole is created as the Ti+4 ion shifts slightly along a <100> direction, resulting in a slightly tetragonal structure (c/a 1.01). Ferroelectric domains form to minimize strain energy. Commercial polycrystalline BaTiO3 contains various impurities and dopants and the purpose of this TEM study is to assess whether similar behaviour occurs compared to the pure material.

BaTiO3 capacitors from several industrial sources were examined, containing up to several atomic per cent of various oxides (Bi, Zr, Sn, Ca) which stabilize the high dielectric constant over a wide range of temperatures and “tie up” oxygen vacancies. Previous TEM work in the present study using EDS has shown that the presence of impurities prevents the ferroelectric phase transformation and the formation of ferroelectric domains at room temperature. No ferroelectric domains exist in region A of fig. 1(d) where Bi, Sn, and Ca impurities were detected, while conversely in the ferroelectric region B no impurities could be found. (Delta fringes from overlapping ferroelectric domains delineate the ferroelectric portion of the grain.) It is thought that impurity ions substituting on the BaTiO3 lattice distort the lattice sufficiently to prevent the phase transformation from occuring.
Localisation and Momentum Transfer in Inelastic Scattering
Authors: Howie A.
Published: June 2020

With the more positive and precise utilisation of a wide variety of inelastic signals now made possible by STEM, microscopists ask questions going beyond the established theory of charged particle scattering. Because of its relevance to resolution and contrast, particular interest attaches to the degree of localisation of these interactions, but this has received only limited attention in earlier work, e.g. ion channelling, particle track structure.

A fast electron with velocity v, scattering through an angle θ with energy loss ΔE =θEmv2, experiences a momentum transfer. The corresponding impact parameter b is, by the uncertainty principle, roughly given bybut a more precise approach evaluates the scattering from a suitably localised initial wave function (e.g. a Gaussian) to a final state plane wave accepted by the detector (fig.1). The scattering amplitude as a function of b can be calculated from the more familiar plane wave scattering amplitudes by Fourier integration.
The Combined Effect of Channelling and Blocking in Electron Energy Loss Spectroscopy
Authors: Taftø J. , Krivanek O. L.
Published: June 2020

Bragg reflection of electrons gives rise to a modulation of the wavefield over the crystal unit cell. Depending on the incident beam direction the electrons may be concentrated at one or another type of atoms or between them. Localized ionization processes will therefore show an orientation dependence, and this will affect the X-ray emission intensities as well as electron energy loss spectra. The energy loss case gives more possibilities for experimental arrangements than the X-ray emission case, in that the direction of not only the incident electron beam, but also that of the exit beam to be analyzed may be selected.

Natural MgAl2O4spinel was studied. The crystals were ground in a mortar and thin areas were analyzed with a Gatan 607 spectrometer attached to a Philips 400T electron microscope operating at lOOkV. The experiments were done for the (400)-planar case where the main atomic planes contain Al2O4. The Mg-atoms are midway between the A12O4and may be considered as interstitials in this planar case.
Application of EELS to the Study of Metal-Hydrogen Systems
Authors: Zaluzec N. J. , Schober T. , Westlake D. G.
Published: June 2020

The study of metal-hydrogen systems is becoming increasingly important in various energy technologies today, and as a consequence it becomes desirable to be able to characterize the resulting phases as accurately as possible. In this paper we report a preliminary study of metal-hydrogen systems using the technique of electron energy loss spectroscopy (EELS) in an analytical electron microscope (AEM).

The study of hydrogen in rare earth metals using EELS was first reported by Colliex et al. in 1976; in that work as well as in this study the characteristic energy loss of plasmon scattering was measured in various metal and hydride phases. Plasmon scattering in general is related to electronic structure of the material and thus the formation of a hydride phase if it affects the electronic structure of the alloy is expected to produce characteristic changes in the energy loss distribution.
SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections
Authors: Egerton R.F.
Published: June 2020

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).
The Observation of Atomic Surface Structure from Au Thin Films
Authors: Krakow William , Trafas G.
Published: June 2020

The direct imaging of the surface structure of thin crystalline films in the conventional transmission electron microscope (CTEM) requires resolution of a few angstroms both laterally and perpendicular to the atomic surface layers. Although the lateral resolution was not achieved, dark-field images of the forbidden reflections from (111) Au films could be employed to image lateral areas ∼500Å diameter. The first atomic level resolution pictures of the Au surface of (001) films were reported by Krakow and Ast. Here optical diffractograms revealed the presence of the forbidden surface reflections due to partially filled bulk lattice unit cells corresponding to a surface lattice periodicity of ∼2.86Å. Subsequently, improved electron micrographs were obtained at incident beam energies of lOOkV and at ImeV where in the latter case the microscope resolution was better than 2Å3. Several diffraction experiments were also performed to understand the nature of the surface structure of (001)Au. In this study models of a “single” (001)Au surface were constructed and computations performed to demonstrate the types of images attainable at different resolution levels and under different microscope imaging conditions.
UHV-Electron Microscope Study of Monolayer Adsorption Processes
Authors: Takayanagi K.
Published: June 2020

UHV electron microscopy (UHV-EM) has been shown to be a potent method for investigations of surface structures and surface processes both in TEM-TED (transmission electron microscopy and diffraction) and REM-RED (reflection EM and ED) modes. In addition to the same structural informations as RHEED and LEED they give important informations on microtopography of the surfaces and/or adsorbed phases and detailed aspects of heterogeneous surface phenomena. Analyses of Au(111) reconstructed surface structure in TEM mode and atomic steps of Si(111) surface, adsorbed structures and their domains and phase transition processes in REM mode were reported previously. The present paper reports further results of such studies. In REM mode, a new evaporator for in-situ observation of metal deposition on Si(111) and a double tilt specimen holder for diffraction analyses of surface reactions were constructed. In TEM mode, dark field microscopy by forbidden surface reflections and high resolution microscopy (HREM) have been applied.
Nucleation of Indium Atoms on an Amorphous Carbon Substrate
Authors: Snipes J. , Ohtsuki M. , Utlaut M. , Crewe A. V.
Published: June 2020

The motion of indium atoms on a thin (∼15 Å) amorphous carbon film was followed over a period of 14 days using a high resolution STEM. Indium was chosen because it nucleates rapidly in comparison with other atom species that have been observed (e.g., Ag, U, Pt, and Pd). A previous study showed that the effect of the electron beam on the motion of the deposited atoms was negligible, so that the observed nucleation is predominantly a diffusion process.

The indium atoms were evaporated onto the substrate. The specimen was then placed in the microscope and kept under vacuum at room temperature throughout the study. Micrographs were taken at daily intervals, digitized, and stored on magnetic tape for retrieval with a computer and image processor. All micrographs were taken at an electron energy of 31 keV (Fig. 1).
Anomalous Weak Beam Contrast from Extrinsic Stacking Faults
Authors: Shaw M.P. , Self P.G.
Published: June 2020

This paper concerns observations of anomalous fault contrast arising from weak beam images of extrinsic faulted dislocation loops. Weak beam images are of considerable use when examining lattice defects due to the reduced image width associated with dislocations and the fine detail revealed in the fringe contrast from stacking faults. The observations described here arose from a study of interstitial (extrinsic) dislocation loops produced by radiation damage in a commercial nickel base superalloy, Nimonic PE16(1).

Figure 1 shows a bright field image revealing faulted loops on all four {111} planes of the f.c.c. structure. Complementary images taken in a variety of different two beam diffracting conditions showed the faulted loops to be <111> interstitial faults surrounded by <111> pure edge (Frank) partial dislocations. When images were taken under weak beam conditions, contrast from the stacking faults was found to be critically dependent on the sign of g.R (where g is the diffracting vector and R the displacement vector of the fault).
EELS Measurements of Carbon and Nitrogen in V(CN) Precipates from HSLA Steel
Authors: Garratt-Reed Anthony J.
Published: June 2020

The technique of carbon extraction replication has enabled many workers to obtain useful data on the composition of a variety of precipitates in alloys. When the available analytical method (energy-dispersive X-ray spectroscopy) was limited to detect only those elements heavier than neon the presence in the specimen of the carbon of the replica was not objectionable. With the development of methods to analyze for light elements, such as electron energy-loss spectroscopy (EELS), or energy dispersive X-ray spectroscopy with an ultra-thin window detector occasions arise when analysis for carbon is indicated. In such cases carbon extraction replication is clearly inappropriate.

In the present project it was required to study the precipitation of vanadium, presumed to be in the form of carbonitrides, in vanadium HSLA steel. Of particular interest was the ratio of carbon to nitrogen as a function of the specimen history and initial composition. Replicas were therefore made using aluminum.
The Application of a Model Function Describing Beam Broadening to Elemental Analysis of Rapidly Varying Concentration Gradients
Authors: Imeson D. , Vander Sande J. B.
Published: June 2020

As microanalysis by X-ray spectrometry in STEM is increasingly applied in materials science, a particular set of problems is being identified in which beam spreading in the sample and the associated concept of the X-ray spatial resolution are crucial to the interpretation of experimental data. These problems include the investigation of solute segregation to, or depletion near, grain boundaries, the determination of composition profiles across dendrite cell walls, especially in rapidly solidified material, composition determination in phase separated systems where the separation takes place on a fine scale, as for example in spinodal decomposition, and many other problems involving small precipitates or interfaces between phases. We intend to discuss beam spreading separately at this meeting. We propose the use of a model, parameterized function to describe beam spreading for application to the problems mentioned above. With this description, an analytic expression for the X-ray emission from a region of known or modeled composition variation can be obtained, being proportional to the convolution of the two functions describing the electron intensity distribution and the concentration variatioa For many simple cases this expression can be simply solved, either analytically or with the aid of a small computer or programmable calculator.
Rapid Recording of Microdiffraction with a STEM Instrument
Authors: Cowley J. M.
Published: June 2020

The optical system attached to our HB5 STEM instrument acts as an efficient two-dimensional detector system which allows microdiffraction patterns from regions 10Å or less in diameter to be recorded at TV rates. Replaying the patterns from single video-tape frames allows us to study transient phenomena and to overcome to some extent the limitations due to the mechanical and electrical instabilities which often induce relative movements of the electron beam and the specimen of the order of 1Å over periods of a fraction of a second.

This rapid recording has made it possible for microdiffraction patterns to be obtained from regions of less than 20Å in diameter selected from images of a highly disordered kaolinite sample which is very sensitive to radiation damage. When the electron beam is stopped at a position chosen by a marker in the bright field image, the diffraction pattern fades out in about 0.1 secs, but several single frames of the videotape provide good records such as that of figure 1(a).
Microdiffraction in Dedicated STEM
Authors: Houghton D.C.
Published: June 2020

Microdiffraction in dedicated STEM instruments has shown considerable promise as a source of microanalytical information. A major problem has been the relatively inefficient sequential methods used to obtain the diffraction pattern. The apparatus shown schematically in Fig. 1 has facilitated parallel viewing and recording of diffraction patterns in the HB5 STEM. The equipment is robust, low cost and can be installed with no modifications to the microscope.

A series of diffraction patterns were recorded under identical conditions at a (110) zone axis in an Al-4% Cu foil shown in Fig. 2(a) to allow direct comparison of sequential and parallel recording methods. The thickness in this part of the foil was ∼220 nm as measured from the projected widths of θ' plates. The selected area “rocking beam” images in Figs. 2(b) and (d) are clearly noisy, suffer from scan distortions and their usefulness for phase identification and crystal orientation is severely limited.
Experiments with an Imaging Filter in a CTEM
Authors: Krahl D. , Herrmann K.-H. , Zeitler E.
Published: June 2020

The installation of an imaging energy filter extends the imaging and analytical capabilities of a conventional transmission electron microscope (CTEM) considerably. We report here on experiments which demonstrate the versatility of such a device. The arrangement of our system is shown in Fig. 1. The experiments performed pertain to:

The improvement of contrast in thick specimens by exclusion of inelastically scattered electrons. The spatial resolution of the electron microscope can be preserved by the correction of second-order aberrations with additional electromagnetic hexapoles.

The determination of the concentration of light elements with EELS at a spatial resolution better than 10 nm. The chemical structure of ceramic material (SI3N4and SiC with additions) could thus be elucidated. A study on the extended fine structure in the energy loss spectra of the oxygen and magnesium K edges in MgO (Fig. 2) did confirm the theoretical prediction for that material.
Analytical Electron Microscope Evacuated by Perfect Dry Pumping System
Authors: Harada Y. , Ishida Y. , Arai Y. , Ooi K. , Obara Y.
Published: June 2020

Analytical electron microscopes (AEM), which provide the functions of transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy, have been in practical use to analyze elements in microareas. Meanwhile, surface studies have recently been conducted with an ultrahigh vacuum (UHV) electron microscope by utilizing reflection electron microscopy including the reflection high energy electron diffraction method. We have developed an ultrahigh vacuum analytical electron microscope (UHVAEM) aimed at surface studies.

The present paper describes the outstanding features of the UHVAEM. Fig. 1 shows the schematic diagram of its vacuum system. The specimen and gun chambers are evacuated by a sputter ion pump (SIP) after being rough pumped by a turbo molecular pump (TMP). The viewing and camera chambers which have much out-gas from photographic films are evacuated by the TMP. The image forming lens system is designed to provide constant projector lens excitation over the entire magnification range.
Development of the Cryo Pump System for Electron Microscope
Authors: Iwatsuki M. , Venuti Guy
Published: June 2020

In proportion, as the electron microscope expands the field as an analytical instrument, the problems of specimen contaimination will become more critical. Also, emission instability and short life of the LaB6 tips depend on the ultimate vacuum pressure in the gun chamber (particularly, due to the partial pressure of oxygenized molecules). Meanwhile, as scanning electron microscopes are utilized as a means for quality control in the semi-conductor field, as well as for analysis, the problems with specimen contamination will become more prominent.

Today, DP-RP type pumps are widely used as high vacuum pumps in scanning electron microscopes. However, due to the oil used in these pumps, back-streaming occurs, causing specimen contamination. In contrast to this wet vacuum system, ion pumps, Ti-sublimation pumps, and Turbo-molecular pumps, etc. have been utilized as dry vacuum systems. Among these dry pumps, ion pumps and Ti-sublimation pumps are most popular as a means of obtaining ultra high vacuum. Also, Turbo-molecular pumps are widely used for scanning electron microscopes.
Generation and Storage of SEM or STEM Intensity Profiles on a Multi-Channel Analyzer
Authors: Owen R. T. , Madden M. M. , Bates S. R.
Published: June 2020

Using an SEM for quantitative analysis often requires intensity profiles along a single scan line. These profiles are usually obtained by either: 1) selecting a scan line from the CRT display, switching to Y-modulation and photographing the displayed intensity profile, or 2) scanning the negative of a photograph of the entire CRT display along a line using a microdensitometer. The first method requires additional measurements of the CRT beam deflection to get quantitative information, and thus has limited accuracy. The second method places another interface between the measurement and the detector signal.

For SEMs or STEMs equipped for energy dispersive x-ray analysis with a multichannel analyzer (MCA) and minicomputer, modifications can be made to the circuitry to allow digital recording of line scan intensity data directly with the MCA.
Bluetongue Virus Infection in Salivary Glands of Culicoides Variipennis
Authors: Foster Neil M. , Jones Robert H.
Published: June 2020

Bluetongue virus (BTV) multiplies in the invertebrate host culicodies variipennis and is transmitted by this biting fly to wild and domestic ruminants; e.g., see review. Virus replication in the salivary gland of nonbloodfed flies was similar to that for cultured cells. This report describe observations on BTV-infected salivary gland cells from bloodfed flies.

Two-day-old female flies, which had been given a blood meal on normal rabbits when the flies were one day old, were inoculated either with normal or BTV-infected cell culture fluids into the hemocoel. Flies were maintained alternately on water and 10% sugar solution for 14-21 days when salivary glands were removed and processed for viewing in thin section.

Viroplasms in association with macrotubules, fibrils, and progeny virions were observed in the cytoplasm of infected salivary gland cells (Fig. 1). Large numbers of macrotubules were observed and they often occupied large areas of the cell. Macrotubules most often appeared in bundles of linear array and had an ordered appearance.
Immunologic Localization of Murine Leukemia Virus Antigens in Thin Sections
Authors: Weigand Ray A. , Paquette Carol I. , Longley Clifford , Furmanski Philip
Published: June 2020

In order to examine the temporal sequence of intracellular events which culminates in the release of infectious virus particles from the cell surface, we have developed immunoferritin techniques to localize viral antigens in thin sections. We previously described the intracellular localization of murine mammary tumor virus p28 protein in thin sections using an unlabelled antibody procedure with ferritin-antiferritin. We now describe the labelling of murine leukemia virus (MuLV) in thin sections using anti-MuLV and Protein A-ferritin.

Cultures of F-MuLV in NIH/3T3 cells were grown to 90% confluence, fixed, dehydrated, and embedded in Epon as before. Thin sections were picked up on nickel grids, incubated in 20% H2O2 for 20 min, rinsed in PBS, and subjected to the labelling procedure. The labelling protocol included: preincubation in 5% BSA in PBS, rinse in 1% BSA in PBS, 3 hour incubation in rabbit anti-MuLV, rinse in 1% BSA in PBS, incubation in apoferritin, incubation in Protein A-ferritin (Zymed Labs., Burlingame, CA), rinses in 1% BSA in PBS and PBS, and incubation in 2% glutaraldehyde in PBS.
Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum
Authors: Hardie L. P. , Balkwill D. L. , Stevens S. E.
Published: June 2020

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systems

Actively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.
Ultrastructural Aspects of the Aecial, Uredial and Telial Stages of Puccinia Asparagi DC
Authors: Baker Karen K.
Published: June 2020

Puccinia asparagi DC is a macrocyclic, autoecious rust occurring on Asparagus officinalis. The most apparent manifestations of the disease are the aecial pustules on the stalks in the spring and the uredial and telial pustules on the fern stems during the summer. Pycnia are inconspicuous and were not observed in the first year of this study

Aecidioid aecia occur in groups on stems (Fig. 1). Hyphae is both inter- and intra-cellular. Aecia have a well-defined peridium, 1 cell layer thick. Aeciospores are binucleate (Fig. 2) and finely verrucose. Verrucae are electron transparent in ultrathin sections. Wedge-shaped disjunctor cells separate the aeciospores.

Uredia occur on the stems of the fern growth during the summer. The pustules are subepidermal and erumpent. Urediospores are pedicillate early during development and at maturity are echinulate (Fig. 3) with 4 equatorial pores. Echinulations are electron transparent in ultrathin sections.
Electron Microscopic and Optical Diffraction Analyses of Crystalline Intranuclear Inclusions in Human Osteosarcoma Cells
Authors: Yasuzumi Gonpachiro
Published: June 2020

The fine structure of the crystalline intranuclear inclusions in the human osteosarcoma cells was studied by using a goniometer which tilted the specimen at angles of ±30° and ±40°. The results appear in the series of micrographs showing Fig. 1. At the point by the arrow, a helical structure is visible in two filaments. Optical diffrection patterns of selected areas of each negative electron micrograph film were taken by using a helium-neon laser as a source.

A tentative model of the structure can be based on optical diffraction techniques applied to electron micrographs taken at different tilt angles. The diffraction pattern taken from image No. 0 in Fig. 1 is depicted in Fig. 2. Diffraction patterns from Nos. 3, 4 and 8 are shown in Figs. 3, 4 and 5. The contrast of some periodic structures can be eliminated in the image (extinction effect due to Bragg reflection of electron waves) by the interference of scattered waves from constituent elements. Hence it is rather important to interpret the electron micrographs and their optical diffraction patterns by considering the extinction effect of the image contrast.
Stereoscopic Visualization of Spermidine-DNA Torus Structure Prepared by the Freeze-Fracture, Deep-Etch Technique
Authors: Ruben George C. , Marx Kenneth A. , Reynolds Thomas C.
Published: June 2020

Freeze-fracture TEM has been used to visualize spermidine-DNA complexes╌a model system for bacteriophage DNA packaging. We have observed the toroidal shape and bacteriophage size (770Å) of spermidine-condensed DNA particles prepared by quick freezing of DNA-spermidine solutions followed by a freeze-fracture, deep-etching technique. Single direction shadowing with low Pt-C metal levels (9Å thick) has allowed us to demonstrate that the freeze-fracture technique is capable of revealing the organization of separate double helical DNA strands on the torus surface. The spermidine-DNA toruses exhibited surface Pt-C decoration consistent with the DNA double helix being circumferentially wrapped to form the torus. In addition, we have demonstrated that a hydrated sample shows the same toroidal shapes that have been previously demonstrated by Chattoraj et. al, in a dehydrated preparation.

We performed freeze-fracture TEM studies of spermidine condensed (0.2 mM) Calf Thymus DNA (5 μg/ml) complexes in 1 mM NaCl, 10 mM Tris pH 7.0. Samples were freeze-fractured and etched for 13 min at -97°C.
Position of Histone Pairs: H3, H4 and H2A, H2B Within the Nucleosome
Authors: Stoeckert C. , Beer M. , Wiggins J.W. , Hjelm R.P.
Published: June 2020

The genetic material of eukaryotes is organized into nucleosomes. These consist of 145 base pairs of DNA and 2 each of the histone proteins: H2A, H2B, H3 and H4. Studies by Finchet al(1977) and Dubochetet al(1978) indicate that the shape of the nucleosome is a flat cylinder with a diameter of 110Å and a height of 55Å. Models based on histone-DNA and histone-histone cross-linking have been proposed by Kluget al(1980) and Carteret al(1980). Here we report a direct determination using the Johns Hopkins scanning transmission electron microscope (STEM) (Wigginset al, 1979).

In order to identify a histone, it was labeled with several platinum atoms in a two-step procedure. The first is modification of the histone lysines with methyl (methyl-thio-acetimidate). This reaction was done on 0.3 mgs/ml in nucleosome protein in 0.6 M NaCl, 20mM Na borate pH 9.4. An imidate conc. of 40mM modifies about 50-60% of the lysines. The result is to provide thioether groups for subsequent platinum binding.
The Ultrastructure of Lymphocytic Hypophysitis
Authors: Asa S.L. , Kovacs K. , Bilbao J. M. , Josse R. G. , Kreines K.
Published: June 2020

Seven cases of lymphocytic hypophysitis in women have been reported previously in association with various degrees of hypopituitarism. We report two pregnant patients who presented with mass lesions of the sella turcica, clinically mimicking pituitary adenoma. However, pathologic examination revealed extensive infiltration of the anterior pituitary by lymphocytes and plasma cells with destruction of the gland. To our knowledge, the ultrastructural features of lymphocytic hypophysitis have not been studied so far.

For transmission electron microscopy, tissue from surgical specimens was fixed in glutaraldehyde, postfixed in OsO4, dehydrated and embedded in epoxy-resin. Ultrathin sections were stained with uranyl acetate and lead citrate and examined with a Philips 300 electron microscope.

Electron microscopy revealed adenohypophysial cells of all types exhibiting varying degrees of injury. In the areas of most dense inflammatory cell infiltration pituitary cells contained large lysosomal bodies fusing with secretory granules (Fig. 1), as well as increased numbers of swollen mitochondria, indicating oncocytic transformation (Fig. 2).
Is There a Mast Cell-Noradrenergic Nerve Interaction in the Bovine Splenic Vein?
Authors: Dzielak David J. , Thureson-Klein Åsa
Published: June 2020

Release of neurotransmitter from noradrenergic nerve terminals can be modulated by a variety of endogenous and exogenous compounds which act as agonists or antagonists at receptors located on the presynaptic membrane of the terminal.For example, noradrenaline acts as an α-adrenoreceptor agonist to decrease further release. This effect can be reversed by drugs such as phentolamine which blocks the α-adrenoreceptor to increase the outflow of transmitter. Actually, the α-receptor mediated overflow after exposure to an antagonist is one of the most studied mechanisms in transmitter regulation. However, we have been confronted with an exception to the rule of noradrenaline overflow after phentolamine (Fig. 1). In this study isolated bovine splenic vein strips were preincubated in tritiated noradrenaline and mounted in a superfusion apparatus. Oxygenated Tyrodes medium (pH 7.4) containing 10-6M cocaine and 10-4M normetanephrine was used during superfusion.
Retrograde and Transganglionic Anterograde Transport of an HRP-Wheat Germ Acclutinin Conjugate as Studied with Tetramethyl Benzidine Ultracyto-chemistry
Authors: Carson Keith A. , Mesulam Marsel
Published: June 2020

The protein tracer horseradish peroxidase (HRP) is a primary component in the current method of choice for the anatomical demonstration of neuronal connections. Recently the performance of HRP as a neuronal tracer was improved significantly by conjugating the HRP to wheat germ agglutinin (WGA). When compared to HRP alone, the conjugate was observed to label larger numbers of neurons following comparable injections. In addition, the conjugate has been shown to be transported through peripheral ganglia and into the central projections of the ganglion neurons. However, the ability of the conjugate to demonstrate neuronal connections, as with HRP alone, is greatly dependent on the cytochemical method used to localize the HRP activity. It was previously shown by light microscopy, that the tetramethyl benzidine (TMB) method provided the highest degree of sensitivity when tested against eight other commonly used HRP cytochemical methods. Only recently have the conditions necessary to render the TMB reaction product suitable for electron microscopy been described.