bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrated Specimen Stability in the Electroscan ESEM: Specimen Surface Temperature Variations and the Limitations of Specimen Cooling
Authors: Griffin Brendon J.
Published: June 2020

Chamber temperature and pressure are the two principal factors in preserving hydrated specimens in a high vapour pressure or environmental SEM; in this study the Electroscan ESEM. Hydrated specimen stability, is achieved by operating at or near water saturated conditions in the specimen chamber.

The ambient chamber temperature (in the ESEM) has been measured and found to be ∼29°C, ∼7°C higher than the laboratory environment. Water saturation at this temperature requires a chamber pressure of ∼30t and poor image resolution results from the high degree of primary beam scattering under these conditions. A low cost Peltier effect cooling stage has been constructed to provide cooling of specimens to ∼5°C. At this temperature water saturated conditions are achievable in the chamber at ∼5t with resultant good image resolution.

Usage has shown that stability of sensitive hydrated specimens still remains difficult. This is due to the cooling and measurement of specimen temperature through the stage at the base of the specimen, rather than at the surface.
Trauma causes heterogeneous compositional shifts in spinal cord
Authors: Walsh Lyle G. , Greene William B.
Published: June 2020

Each year spinal cord trauma causes thousands of otherwise healthy people to be permanently disabled. In most cases, the axonal tracts are not mechanically severed. Instead, unknown mechanisms cause a progressive segmental necrosis. In this study, we use electron probe x-ray microanalysis, EPMA, to examine the composition of the dorsal axons and myelin 6 hours after mild and moderate trauma in order to identify the subcellular changes induced by trauma. Laminectomies were performed on anesthetized rats and sham, 6 g-cm or 20 g-cm trauma was delivered and the wound closed. Six hours after trauma the rats were again anesthetized, the dura was removed and the spinal cord was frozen in situ with a 100 psi jet of super-cooled liquid propane. Cryosections, 200 nm thick, were cut at -120°C and placed on carbon coated formvar covered folding copper grids. Samples were freeze dried and analyzed within an Hitachi H-7000 STEM on a Be tipped, GATAN, analytical cold stage with a 2-4 nA, 125 KeV beam.
Prospects for compositional imaging with the atom probe microscope
Authors: Kelly T. F. , Camus P. P. , McCarthy J. J. , Larson D. J. , Holzman L. M. , Zreiba N. A.
Published: June 2020

For the purposes of analytical characterization on the atomic scale, the ultimate instrument would identify every atom in a sample and determine its position with atomic-scale resolution. The recently developed positionsensitive atom probe (POSAP) comes as close as yet possible to this goal. This is the only experimental technique which can analyze the three-dimensional (3D) composition of a sample on a sub-nanometer scale.

By adding a position-sensitive detector (PSD) to a conventional atom probe/field ion microscope, a 3D data structure with position-correlated compositional analysis is acquired. The 3D data are stored on a computer and may be examined for structural and compositional information at an atomic level. Note that, because it uses time-of-flight mass spectroscopy, all elements and their isotopes are detected in this way with equal proficiency. Usually, the evaporation rate is mediated by pulsing the field on the specimen. This approach, however, severely limits the data acquisition rate (about 1 atom per second) and mass resolution (about 1 part in 30).
The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe
Authors: Zuo H.J. , Price M.W. , Griffin R.D. , Andrews R.A. , Janowski G.M.
Published: June 2020

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.
The genetic relationship between hydrous and anhydrous interplanetary dust particles
Authors: Zolensky Michael , Barrett Ruth
Published: June 2020

It is a fundamental goal of interplanetary dust particle (IDP) research to determine the sources and histories of these primitive extraterrestrial materials. Chondritic IDPs have been divided into anhydrous and hydrous varieties, with sub-classification being made on the grounds of the dominant anhydrous (olivine or pyroxene) or hydrous (smectite or serpentine) present. The presumption is that hydrated IDPs experienced aqueous alteration on parent bodies (hydrous asteroids or possibly comets); we wish to discover whether the anhydrous IDPs were the initial raw materials for these reactions. We report here analyses of olivines and pyroxenes from 22 large (>15 um) chondritic IDPs: 18 anhydrous and 4 hydrous; olivines and pyroxenes are scarce in most hydrous IDPs, when present at all Finally, we compare anhydrous to hydrous IDPs, and both to chondritic meteorites.

Figure 1 shows our results for this study. We find there to exist no significant difference in the compositions of olivines from olivine vs. pyroxene dominated IDPs, which are therefore plotted together (in contrast to our preliminary results for a smaller data set).
A preliminary study of a high-Na glass and its Cl-rich inclusions by EPMA
Authors: Yang S. V. , Wagstaff J. H. , McKay G. A.
Published: June 2020

It is always a challenging task for the probe user to handle the Na-loss problem of high sodium glasses in EPMA (electron probe microanalysis). To find an appropriate Cl-bearing EPMA standard is another challenge, too. Here we adopted the analytical methods suggested by Yang, et. al., to meet both challenges for our study of a unique glass (Sample C9) from the Lonar Crater, India. The main object of this study is to explore an old field (Na loss) and a new field (standardless WDS analysis) in EMPA. Therefore, we will not discuss the geological implications of the analysis results in detail.

Glass C9 contains more than 95% glass matrix plus a few percent inclusions. The majority of the inclusions in the glass matrix are feldsparthoid-like clusters 100-200 microns in size (Figure 1). Pyrite-like dissimilates less than 1 micron are also common. The glass is a quenched impact melt formed when a meteorite struck an evaporite-rich target area.
Small-area-x-ray fluorescesce analysis of multilayer thin -metal- films
Authors: Zaitz M. A.
Published: June 2020

Thin film technology has become an integral part of semiconductor multichip ceramic packages. Characterizing the thickness of multimetal thin film structures that combine both thin and thick films is an important parameter for manufacturing process control and development.

Statistical process control (SPC) is a new requirement for manufacturing processes. Cost is also becoming a crucial factor. "State of the art" multichip ceramic packages built to many levels of thin films are expensive. The fewer parts sacrificed for testing using the standard destructive analytical techniques the more cost effective is the process. Small area, non-destructive thickness measurements on actual product are a must for today and will be even more significant in the future as patterns are reduced in size. Creative and innovative instrumentation and techniques are needed to keep pace with the changing technology. The new and novel micro XRF technique is meeting the challenge "head on".

Traditional micro analysis techniques such as SEM-EDX and microprobe involve altering the sample, i.e.
Microbeam x-ray diffraction and its applications in the semiconductor industry
Authors: DeHaven Patrick W.
Published: June 2020

X-ray diffraction(XRD) from polycrystalline materials is a powerful structural probe, capable of obtaining information on phase(s), crystallite orientation, average grain size, and residual stress. One problem in the application of XRD to the analysis of semiconductor chips and multi-chip carriers is that there is often the need to obtain information from individual features, which can range in size from several hundred microns on chip carriers to sub-micron on semiconductor devices. Conventional powder diffractometers are designed to irradiate an area of several square millimeters, and cannot be used to examine individual micron-sized features. This need to obtain diffraction information from very small areas has been one of the driving forces behind the development of x-ray microbeam diffraction.

The design of a microdiffractometer involves modification of the incident x-ray beam, the sample holder, and the x-ray detector. The incident beam must be focused down to a spot size consistent with the feature to be examined.
Interface Between a Gatan PEELS and an EDAX 9900 Computer for Simultaneous Energy Loss Analysis and Chemical Mapping
Authors: Thomas X. , Balossier G. , Wagner D. , Martin Ph. , Bonhomme P.
Published: June 2020

Introduction

Energy loss spectroscopy is a well known technique allowing elemental analysis in thin films. When an energy loss spectrometer is coupled with a STEM it is possible in addition to perform chemical mapping. The U314 INSERM laboratory is equipped with a C.M. 30 PHILIPS STEM coupled with an EDAX 9900 and a GATAN 666 parallel detection electron spectrometer.

We describe a complete system including an additional A.T. microcomputer enabling simultaneous energy loss analysis and chemical mapping .

Material and method

An interface fitted with the bus connecting the GATAN electronics and the EDAX multichannel analyzer (MCA) allows to read the data during a photodiode read-out, and to send them via a parallel port into the host A.T microcomputer. To do this, only 18 bus lines are used and the proprietary communication protocol between the photodiode interface and the MCA is not affected. All the functions provided by the EDAX PVEELP software are preserved.
The Detection of 0.5AT% Boron in Ni3Al Using Parallel Energy Loss Spectroscopy
Authors: Boothroyd C B , Sato K , Yamada K
Published: June 2020

Recent work has suggested that the improvement in ductility when boron is added to the inherently brittle Ni3Al is caused by the segregation of boron to the grain boundaries and that this seems to be associated with the presence of disordered grain boundary “phases”. In order to clarify the role of boron at Ni3Al boundaries at the resolution of transmission electron microscopy we have developed a method for detecting concentrations as low as 0.5at% of boron in Ni3Al using parallel energy loss spectroscopy.

Specimens of Ni-24at%Al with and without 0.5at% B were electropolished in a 20% perchloric acid/ethanol solution and examined at 120 kV in a Philips 420T electron microscope equipped with a Gatan parallel energy loss spectrometer. Figure la shows part of the loss spectrum from the Ni3Al-0.5%B matrix after background subtraction. Provided a high enough count rate can be obtained, the major problem for detecting small edges in energy loss spectra is channel to channel variations in the gain, which for figure la produce a noise level (2σ) of ~0.3%.
Stepped Diffractor for Point Focusing of Monochromatic X RAYS
Authors: Wittry David B. , Sun Songquan
Published: June 2020

Point focusing x-ray diffractors can be obtained by a geometry that corresponds to rotating the Johansson geometry about a line joining the source and image points. Methods by which such a diffractor can be made from bulk single crystal materials have been previously described. In the present paper, we consider the design of a diffractor with a stepped surface that could utilize layered diffracting materials such as multiple monomolecular films or layered synthetic microstructure (LSM). First we consider the effect of the diffractor material's rocking curve on the performance in focusing diffractors. Then we consider limitations on the focusing that arise from the width of the rocking curve and the finite size of the steps, and we give an example of the design parameters of a point focusing diffractor with stepped surface.

Effect of The Rocking Curve. Width For diffractors used in focusing applications, it is important to know the physical basis for the rocking curve in order to determine whether the width of the rocking curve will affect the angle of diffraction.
Electron spectroscopic imaging and analysis of calcium ions during the first 24h of the interaction of Trypanosoma cruzi heart muscle cell
Authors: Nazareth Meirelles Maria , Claudia Pereira Miriam
Published: June 2020

Several processes are controlled by the intracellular level of calcium ions. It is generally accepted that calcium ions play an important role contraction-relaxation cycle of muscle cells. Chagas 'disease is an endemic disease in South America caused by T. cruzi where a parasite - induced destruction of heart muscle occurs leading to heart failure, cardiac blockage and arrythmias.In order to study the role of calcium ions during the interaction of T. cruzi - host cells, primary cultures of heart muscle cells (HMC) obtained from dissociation of heart mice embryos were infected with trypomastigotes forms of T. cruzi for 24h (1). The cells were processed with protocols that include in the fixation step the presence of 2.5 to 10mM of CaC12 and in the post fixation the addition of 0.8 potassium ferrocyanide in 2 osmium tetroxide plus 2.5mM CaC12 (2.3).

The electron spectroscopic image (ESI) of ultrathin and unstained specimens were performed with a Zeiss EM 902 equipped with an integrated imaging electron energy spectrometer that eliminates aberrations and contrast losses and produces elementspecific images.
Quantitative EDS analysis in the SEM applying the XPP procedure
Authors: Pouchou Jean-Louis , Pichoir Françoise
Published: June 2020

Extensive work has been done during the last decade to develop new models able to improve the performance of data reduction procedures 1n quantitative x-ray microanalysis. Some of them are now successfully used as routine tools in microprobe work, and allow to analyze accurately light and ultra-light elements and to characterize layered specimens.

In the field of analytical scanning electron microscopy (SEM) using energy dispersive spectrometers (EDS), it seems that less attention has been paid to the effective improvement of the quantitation processes. Although EDS systems have unavoidable limitations due to their lower peak-to-background ratio and poorer resolution, the authors have the feeling that the quantitative results can be significantly improved by use of more reliable models taking properly into account the specific instrumental and experimental conditions.

With this aim in view, our first contribution has been to implement our recently developed XPP model and associated routines (mass absorption coefficients, efficiency of the Quantum window) into the KEVEX Delta system.
Computer programs for the calculation of x-ray intensities emitted by elements in multi-layer structures
Authors: Bastin G.F. , Heijligers H.J.M. , Dijkstra J.M.
Published: June 2020

For the calculation of X-ray intensities emitted by elements present in multi-layer systems it is vital to have an accurate knowledge of the x-ray ionization vs. mass-depth (ϕ(ρz)) curves as a function of accelerating voltage and atomic number of films and substrate. Once this knowledge is available the way is open to the analysis of thin films in which both the thicknesses as well as the compositions can usually be determined simultaneously.

Our bulk matrix correction “PROZA” with its proven excellent performance for a wide variety of applications (e.g., ultra-light element analysis, extremes in accelerating voltage) has been used as the basis for the development of the software package discussed here. The PROZA program is based on our own modifications of the surface-centred Gaussian ϕ(ρz) model, originally introduced by Packwood and Brown. For its extension towards thin film applications it is required to know how the 4 Gaussian parameters α, β, γ and ϕ(o) for each element in each of the films are affected by the film thickness and the presence of other layers and the substrate.
Microanalysis of Asbestos Fibers by Ft-IR Microscopy
Authors: Reffner John A. , Wihlborg William T.
Published: June 2020

The identification of asbestos fibers in bulk or airborne samples can be made by Fourier transform infrared (FT-IR) microscopy. Since asbestos fibers have been shown to be a health hazard, it is important to identify their presence in environmental samples. Asbestos fibers require both chemical and morphological data for their identification. This FT-IR microscopical method uses light microscopy for morphological and infrared spectroscopy for chemical identity of microscopic fibers. For the six minerals defined by the EPA as asbestos, the infrared spectral analysis can be made on the same sample preparations that are used for polarized light microscopy(PLM) or phase contrast microscopy (PCM) counting. In this study, the detection limit for asbestos fibers in airborne samples was 2 × 20μm (˜˜240pg).

The infrared spectra of microscopic fiber bundles of standard asbestos minerals were obtained using an IRμS™ infrared microspectrometer. Spectra were collected within the range of 4000 to 600 cm-1 (2.4 to 16.7 μm), at a spectral resolution of either 2 or 4 cm-1.
Low-temperature Scanning Electron Microscopy and Physical-Chemical investigations of leaf surface characteristics
Authors: Guggenheim R. , Zuberbühler E. , Düggelin M. , Harr J.
Published: June 2020

Plant protection agents (often incorrectly referred to as ‘pesticides’) mostly are targeted at plant surfaces either to protect them against pathogens and parasites or to destroy the treated plants in the case of herbicides. Many times, more than one species of plants are involved, that respond differently to such applications.

In any of the cases cited, a thorough knowledge of the leaf surface characteristics may help to explain desired or undesirable effects. Also the wetting properties of a spray applied to plants will likely influence the performance of the active ingredient involved. It is obvious that only the use of a whole array of different methods will allow an interpretation or a prediction of effects caused by the application of plant protection sprays.

To get well preserved epicuticular wax structures of leaf surfaces we used low-temperature scanning electron microscopy (LTSEM). Fresh cut samples were immediatly frozen in liquid nitrogen, transferred into a Balzers SCU 020 cryopreparation unit attached to an SEM Cambridge Mk II A.
Secondary and Auger Electron Spectroscopy and Energy-Selected Imaging in a UHV-STEM
Authors: Hembree Gary G. , Luo Frank C. H. , Venables John A.
Published: June 2020

A new UHV-STEM has been developed for the NSF-HREM facility at Arizona State University. In this instrument low energy (0-2 keV) electrons can be collected through the objective lens from both sides of thin (STEM) samples, or from the input side of bulk (SEM) samples. As explained in more detail elsewhere, we use magnetic parallelizers to control the angular compression of the emitted secondary and Auger electrons, which spiral around the B-field lines. The parallelizers have axial fields of about 100 G, and compress all these emitted electrons into a cone of less than 6 deg. The sample may be biassed negatively by a few hundred volts, which enables us to compress the cone angle further and to observe the sample using biassed secondary electron imaging (b-SEI). At the exit aperture of the parallelizer the low energy electrons are deflected slightly off-axis by a Wien (E × B) filter to separate them from the the 100 keV beam.
Intensity Sensitivity of RHEED
Authors: Ma Yiqun , Bonevich John , Marks Lourie D.
Published: June 2020

It is well recognized that RHEED patterns are very rich in information. However, due to the lack of a suitable dynamical theory for the interpretation of these patterns obtained from arbitrary surfaces, one important part of the information-the intensities of these patterns (instead of individual spot), has not been used for surface analysis. With newly developed EPMO method (Edge Patching method in Multislice-Only mode), dynamical simulations of RHEED patterns for arbitrary surfaces have become possible. The results of the simulations show that the intensities of RHEED patterns are highly sensitive to various surface structures, such as surface reconstruction, adsorption, surface relaxation, surface absorption and surface steps ect..

Fig.1 shows the simulated RHEED patterns using the EPMO method for the 2×1 missing row reconstruction (a) and the 2×1 oxygen chemisorption (b) on the Au(001) surface and [010] zone. The incident energy is 100keV and the incident angle is 30mRad. The intensities of fractional spots corresponding the 2×1 oxygen chemisorption in (b) are perceivably weaker than those corresponding to the 2×1 reconstruction in (a), since the oxygen is a weak scatter, compared to the gold.
Applications of High-Resolution X-ray Mapping
Authors: Garratt-Reed Anthony J.
Published: June 2020

It has been well established that x-ray imaging (mapping) of samples at high magnification in a field-emission analytical electron microscope is a viable technique when some form of correction is employed to compensate for the unavoidable image drift which occurs during the somewhat extended acquisition time of the images. The technique is only of practical use, however, if the time spent in acquiring the image results in data which would not otherwise have been obtained. It is the purpose of this paper to present examples where high-resolution mapping did provide data which was unique and essential to solve the problems under investigation.

All experiments were performed in a VG Microscopes HB5 STEM, with a field-emission gun operating at 100kV. For most experiments, the probe size was of the order of 2 nm, and the probe current was 0.2-0.4 nA. The x-ray detector was a Link Analytical LZ5 windowless energydispersive x-ray spectrometer with a resolution of 137eV at 5.9kV, subtending a solid angle of 0.078Sr at the sample.
On-line measurement of specimen thickness by Convergent Beam Electron Diffraction
Authors: Otten Max T.
Published: June 2020

Convergent Beam Electron Diffraction (CBED) thickness measurement is the easiest and most accurate way of determining the thickness of crystalline materials. The method was described by Kelly et al. The specimen thickness can be calculated from a few measurements on a recorded diffraction pattern in a matter of minutes (by hand) or seconds (by a computer program).

For thickness measurement a CBED pattern is needed that contains a two-beam diffracting condition, with a dark Kikuchi line going through the centre of the Bright-Field disc and the corresponding bright Kikuchi line through the centre of a Dark-Field disc. Parallel to the bright Kikuchi line, the Dark-Field disc contains a number of fringes (Fig. 1) whose distance from the Kikuchi line varies with specimen thickness. The data needed for a measurement are the electron wavelength, the d-spacing dhkl of the diffraction used, the distance 2θB between the Bright-Field disc and Dark-Field disc in the CBED pattern, and the distances Δθi between the dark thickness fringes and the bright Kikuchi line in the Dark-Field disc (Fig. 2).
Analysis by Electron Diffraction of a Rhombohedral Al-Ge Phase
Authors: Vincent R. , Exelby D. R.
Published: June 2020

Although we have shown in previous work that large angle CBED (LACBED) patterns excited around zone axes include kinematic intensities suitable for determination of unknown structures, the data collection and processing required is quite considerable, especially for crystals with moderately large unit cells. As a preliminary guide to a structure, we have investigated the utility of approximate structure factors and phases obtained from zero layer reflections excited around a major zone axis, followed by a Fourier or Patterson transform to estimate projected atom positions. Naturally, dynamical effects cannot be avoided but the use of focussed LACBED patterns implies that local perturbations from non-systematic reflections are not an important factor that limit the accuracy of intensity measurements. Furthermore, it is convenient here to separate reflections into two sets, where the majority are essentially two-beam in character, whereas the remainder lie within strong systematic rows. Even within these rows, only the extinction distances of weaker reflections are likely to be seriously perturbed, and therefore affect the accuracy of structure factors.
TEM contribution to solve the crystal structure of Sr5Ir3O11
Authors: Li Z. G. , Harlow R.L. , Marshall WJ. , Crawford M.K. , Subramanian M.A.
Published: June 2020

X-ray diffraction plays a dominant role in the crystal structure determinations. Typically, diffraction data of a selected "single" crystal is first collected by a diffractometer, and then the crystal structure can be solved and refined. The quality of the structure determination is measured by the crystallographic residual value R. If the R value is reasonably small, the structural model is assumed to be correct. Usually, models found by x-ray diffraction do describe real structures and these can be confirmed by other techniques. We report here an unusual case, a plausible structural model which yielded a low R value from data collected on a crystal that was NOT "single": the structure derived from the "single" crystal x-ray diffraction data is completely bogus. TEM played an important role in solving this problem.

In the context of high-temperature superconductivity, we have recently studied Ir+4 containing layered oxides in the SrO-IrO2 system. Sr2lrO4 has a K2NiF4-type structure with a rotational distortion (see fig. la).
High precision measurement of Debye-Waller factors for NiAl
Authors: Niichter W. , Weickenmeier A.L. , Mayer J.
Published: June 2020

Motivation
Quantitative convergent beam electron diffraction (CBED) is increasingly appreciated as a tool to determine bonding charge densities of crystalline materials. Simulated CBED patterns are fitted to experimental ones to derive the structure factors. These are converted by means of the Mott formula to yield the total charge density. Finally a neutral atom total charge density is subtracted and the difference is interpreted as the bonding charge density. Accounting for the temperature by a Debye-Waller factor (DWF) the g-th Fourier coefficient of the bonding charge density is then given by

where u denotes the thermal root mean square atomic displacement. Here we have assumed thesimplest case of identical isotropic atomic vibrations for all atoms in the crystal. In order to estimate the error in due to the uncertainty in u we insert the results obtained by Fox and Tabbernor for NiAl at room temperature. They found differences between atomic and measured values of in the order of 2 percent.
Structure of high hardness cathodic-arc deposited carbon
Authors: Callahan D. L. , McAdams S. D. , Anders S. , Anders A. , Brown I.G. , Bhatia C. S.
Published: June 2020

Carbon films exhibiting a peak hardness of 59 GPa have been produced using pulsebiased cathodic-arc deposition. This value is much greater than that expected of an amorphous "diamond-like" carbon (die) film and is well within the hardness range of chemically vapor-deposited diamond. Furthermore, this peak hardness is observed at an indentation depth of approximately 50 nm and not on the upper surface of the film. A structural analysis by transmission electron microscopy (TEM) has been conducted in order to explain these mechanical phenomena.

Details of the sputtering apparatus are described elsewhere. Films for this study were deposited on silicon using a two-step process in which a thin layer, approximately 10 nm, was first deposited at a relatively high substrate bias (~2 kV) followed by growth of the majority of the film at a lower bias (~200 V). Plan-view examination of carbon films revealed both uniformly amorphous regions and extensive nanocrystalline phase regions.
Atomic resolution in energy-loss images: fact or artefact?
Authors: Otten Max T.
Published: June 2020

Since the introduction of energy-filtered imaging, the ultimate resolution has been a point of debate. Berger and Kohl[1] concluded that resolution is limited to ~1 nm. In contrast, one group of investigators[2,3] has argued that atomic resolution can be achieved. The conclusions from the latter group have been questioned previously [4]. In order to provide more insight into the origin of the fine detail in some energy-loss images, a number of experiments have been performed to try and resolve this issue.

The main issue of the high-resolution detail in energy-loss images (i.e., images from electrons that have lost an amount of energy) is whether it comes from elastic or to inelastic scattering. In the former case, a combination of elastic scattering and inelastic scattering, the high-resolution energy-loss image is an artefact. In the latter case, inelastic scattering only, it would be real.

On the basis of theory energy-loss images are unlikely to achieve atomic resolution.
Quantitative compositional mapping of InxGa1-XAs/GaAs quantum wells by annular dark field imaging
Authors: Hillyard S. , Chen Y.-P. , Schaff W.J. , Eastman L.F. , Silcox J.
Published: June 2020

Annular dark field imaging in the scanning transmission electron microscope (STEM) exhibits both high resolution and Z-contrast. It is intrinsically quantitative since image data can be recorded directly from linear detectors into digital memory. Annular dark field imaging has been used, along with energy filtered imaging to correct for sample thickness variation, to map out the In concentration in InxGa1-xAs quantum wells with near atomic resolution and sensitivity. This approach is similar to “chemical lattice imaging”, which maps out composition variation using a conventional transmission electron microscope image and a vector pattern recognition algorithm.

The quantum wells were grown by molecular-beam epitaxy (MBE). Figure 1 shows a typical high resolution annular dark field image of a 50 Å wide nominal In0.3Ga0.7As/GaAs quantum well. The linescan in figure 2 gives the actual numbers making up the image. Barring contaminants and lattice imperfections, the change in intensity with position is caused by two things: variation of In concentration and thickness.
Compositional separation in CoCrTa thin film as observed using a TEM with an imaging filter
Authors: Kimoto K. , Yahisa Y. , Hirano T. , Usami K. , Narishige S.
Published: June 2020

Cobalt chromium alloys are current longitudinal high-density recording media. Compositional features in the cobalt chromium thin films directly affect the magnetic and recording properties. Elemental analyses of the films have been performed by several methods, however, topological nature and crystallographic information are still ill-defined because of limitations in these methods.

In the present study, elemental mapping of cobalt and chromium in a CoCrTa thin film has been quantitatively performed using a transmission electron microscope (TEM) with an imaging filter.

A chromium underlayer (75nm thick) and a CoCrTa magnetic layer (27nm thick) were deposited on a Ni-P plated Al-Mg alloy substrate using direct current magnetron sputtering at a substrate temperature of 270°C. Target contents for sputtering of the CoCrTa film are shown in Table I. Energy-filtered images and electron energy loss spectra (EELS) were acquired using a TEM (Hitachi, HF-2000) equipped with an imaging filter (Gatan, imaging filter model 678). Because of the high brightness of a field emission gun, this system allows a small collection semiangle (4.4 mrad) and a narrow energy window (20-30 eV) for imaging.
Scanning EM in very high electric fields near field ion/emission specimens
Authors: Larson David J. , Camus Patrick P. , Kelly Thomas F.
Published: June 2020

An atom probe field ion microscope (APFIM) has been constructed inside a NORAN Instruments Automated Digital Electron Microscope (ADEM). The ADEM is a scanning electron microscope (SEM) with a field emission source and a very large vacuum chamber. The APFIM has positive and negative high voltage capability and uses a microchannel-plate/phosphor screen assembly as an imaging and single-ion detector. The APFIM specimen can be cooled by a cryogenic refrigerator. The motivation for this study was the need to deliver an electron beam to the apex of an APFIM specimen while a high field is applied. The beam will be used to thermally pulse the field evaporation rate. The expected field-induced image shift and distortion has been studied previously in a transmission EM with a liquid metal field emission source as a specimen.

Fig. 1 shows the interior of the instrument. Computer simulations were done for electron trajectories with negative and positive voltages applied to the emitter based on a simple paraboloidal electric field model described previously.
Problems in interpreting sub-Å-resolution images studied by simulated evolution based digital image matching
Authors: Möbus G. , Dehm G. , Gutekunst G. , Rühle M.
Published: June 2020

1. Introduction:Experimentally determined CTF-data caused predictions that atomic resolution microscopy (JEM ARM1250) of sapphire should become possible with single atomic columns resolved (Fig. 1). The smallest projected bond-length (ca. 0.85 Å) lies beyond the point-resolution of 1.05 Å but within the information limit of this instrument (around 0.85 Å). After extensive trials such images could not be verified experimentally. Instead, images like Fig. 3 b typically appear, containing still high frequencies but different from predictions.

2. Ideal and realistic image simulations:Reasons for this deviations have been examined following with special respect to sub-Å-resolution, including specimen tilt, beam tilt, achromatic anisotropic damping (MTF, vibration, drift), non-ideal columns and amorphous contamination. The stepwise EMS-contrast generation from the crystal single slice over the specimen exit plane into the image plane is compared in Fig. 1 (ideal alignment) and Fig. 2 (realistic simulation). Predominant factors lie in specimen misalignment or other disturbancies (e.g. strain fields) during multislice followed by trade-off effects during fitting of imaging parameters and achromatic damping. The single slice potential is of less influence in the present case.
Quantitative biomedical microscopy: a technology for both basic and clinical sciences
Authors: Herman B. , Pillai M.R. , Halabi S. , McKalip A. , Periasamy A. , Wodnicki P. , Gordon J. , Wang X.F.
Published: June 2020

The development of quantitative optical microscopy has led to the ability to obtain accurate, highly sensitive spatial and temporal measurements of cell structure and function as well as the detection of low levels of pathogenic agents. One application of this capability has been in studies examining the role of high risk Human Papillomaviruses (HPV) in cervical cancer. Cervical cancer is the second most prevalent cancer in women worldwide, and epidemiological studies have strongly implicated the sexually transmitted HPV as a causative agent. So far, approximately 70 different genotypes have been identified, and those types associated with genital lesions have been classified as either “low-risk” or “high-risk” based on their association with benign or malignant lesions. The “high-risk” HPVs, such as HPV-16 and 18, have been found in approximately 84% of cervical carcinomas and are associated with cervical dysplasia and cervical intraepithelial neoplasia (CIN). HPV-16 is the most prevalent high-risk genotype and is present in about 50% of all genital lesions.
Association of gamma-glutamyl transpeptidase (γ-GTP) positive cells with tube-forming structures in rat brain endothelial cell cultures: a bright field and laser confocal microscopy study
Authors: De Bault L.E. , Wang B.L. , Grammas P. , Ringer D.P. , Kong J.
Published: June 2020

Gamma-glutamyl transpeptidase (γ-GTP), an enzyme purported to regulate amino acid transport, is expressed at high levels in blood-brain-barrier (BBB) capillary endothelium, but is a property that is variably expressed in cell culture. The ability of endothelial cells to form capillary-like tubes under different culture conditions has been reported by several investigators. In this study, a rat cerebral resistance vessel endothelial cell strain (RV-150 ECT) , that spontaneously forms cellular aggregates and connecting tubes, has been shown to contain a subpopulation of γ-GTP positive cells, was evaluated for the spatial relationship between γ-GTP and its mRNA, and the tube-forming structures in culture.

Cells were grown on coverslips and fixed in acetone for enzymecytochemistry or in 3% paraformaldehyde and 0.5% glutaraldehyde in PBS pH 7.4 for immunocytochemistry and in situ transcription (IST), respectively. The enzyme substrate/acceptor were γ-glutamyl-4-methoxy-2-naphthyl-amine and glycylglycine. The primary antibody was affinity purified goat anti-γ-GTP IgG. The primers for the IST were 25-nt oligonucleotides complementary to γ-GTP mRNA. After the primers were hybridized to the mRNA the mRNA was transcribed in situ in a mixture of dNTPs containing DIG-labeled dUTP and reverse transcriptase.
Direct phase extension in protein electron crystallography: tests with data from Escherichia coli omp F porin
Authors: Dorset Douglas L.
Published: June 2020

Phase determination in the high-resolution electron crystallographic analysis of membrane protein structures has been based most often on the Fourier transforms of low-dose electron micrographs. With increasing resolution, this task becomes increasingly difficult because of inherent paracrystalline lattice distortions, requiring some ‘unbending’ operation to access information beyond e. g. 6 Å. In addition, the specimen itself will be more prone to radiation damage as the demands for greater resolution are imposed. For this reason, Gilmore, et al. have suggested that direct methods, e. g. maximum entropy and likelihood, be employed to extend easily available lower resolution phase information to the resolution of the electron diffraction pattern. More recently, we have carried out phase extensions for bacteriorhodopsin and halorhodopsin, via the Sayre equation, which is simply a convolution of phased structure factors. Despite pessimistic estimates from x-ray crystallography, the extension, e. g. from 15 to 10 Å to a resolution limit of 6 Å, is relatively easy, so that new phases for bacteriorhodopsin have a mean error of 50°, whereas those corresponding to the most significant magnitudes from halorhodopsin have only a 36° error (but 72° for all new reflections).
Freeze-dried and platinum-carbon replicated 35Å cellulose microfibrils are triple-stranded and left-hand twisted
Authors: Ruben George C. , Bokelman Gordon H.
Published: June 2020

To contrast enhance unidirectional (45° angle) 15-18Å thick Pt/C coated cellulose specimens backed with 100-173Å thick carbon films, micrographs were contrast reversed on Kodak 7302 fine grain positive film. In addition to increasing the contrast of 10-20Å features, the Pt/C coated surfaces are now white and the molecular details are modulated on this background in blacks and shades of grey for easy structural interpretation. By shooting a tilt series at 10° intervals at 105X on a JEM 100CX at 80KV with a 5mm focal length and a 40μ objective aperture, a 6.6Å resolution and a 2710Å depth of field are achieved in the picture series. The tilt series is generally visualized stereoscopically and then a single image representing the correct 3-D structure is shown.
Ultrastructural analysis of hepatic carcinogenesis in two small fish species
Authors: Hawkins William E. , Overstreet Robin M. , Walker William W.
Published: June 2020

Small fish species are potentially good environmental carcinogenesis models because they are sensitive to several types of carcinogens, develop tumors rapidly, and are economical to breed and maintain. To gain a better understanding of the origin and progression of neoplastic lesions, we exposed 6-10-day-old specimens of seven small fish species to the direct-acting carcinogen methylazoxymethanol acetate (MAM-Ac) and all seven developed hepatic neoplasms. We examined livers of two species, Japanese medaka (Oryzias latipes) and king cobra guppy (Poecilia reticulata), by electron microscopy at various intervals after MAM-Ac exposure. Livers were processed by routine procedures. Tissues were minced, fixed by immersion in 3% phosphate-buffered glutaraldehyde, rinsed in buffer, postfixed in 1% phosphate-buffered osmium tetroxide, and processed into Embed 812.
Epidermal cells cultured on a collagen-based material
Authors: Doillon C. J. , Wasserman A. J. , Berg R. A. , Silver F.H.
Published: June 2020

Transmission electron microscopy is an effective means of characterizing the phenotypic expression of epidermal cells. Epidermal cells cultured on plastic dishes proliferate into several layers and differentiate in the same manner as in vivo. Epidermal cells may be cultured on a collagen-based material which can be used as a synthetic epidermis for wound coverage instead of a skin autograft. The purpose of this study is to characterize and compare the morphology of epidermal cells grown on plastic, collagen sheets, and collagen sponges under similar cell culture conditions.
Physical characteristics of "old" epon 812 and various epon-like replacements
Authors: Mascorro J.A. , Kirby G.S.
Published: June 2020

Epon 812 has been used successfully as an embedding medium because of its well known sectioning and staining characteristics as well as its ability to tolerate the unfriendly confines of an electron microscope column which include intense heat and strong vacuum. Although production of this popular medium was discontinued by the Shell Chemical Co. in the mid-1970's, the product still is available from several suppliers. However, existing inventories now are nearly 10 years old and microscopists eventually must rely on similar substitutes if Epon was their original choice. This work has examined the replacements EmBed 812, LX-112, Pelco Medcast and PolyBed 812 for physical characteristics such as flow rate, density, viscosity and hardness. In addition, an original supply of Shell Epon 812 was tested and compared to the Epon facsimilies. This work also seeks to establish ideal infiltration and polymerization schedules in order to minimize processing time and insure that tissues are well impregnated subsequent to microtomy and microscopy.
The distribution of antigen on the surface of RBL-2H3 rat basophilic leukemia cells observed by back-scattered electron imaging
Authors: Stump R.F. , Pfeiffer J.R. , Seagrave JC. , Huskisson D. , Oliver J.M.
Published: June 2020

In RBL-2H3 rat basophilic leukemia cells, antigen binding to cell surface IgE-receptor complexes stimulates the release of inflammatory mediators and initiates a series of membrane and cytoskeletal events including a transformation of the cell surface from a microvillous to a lamellar topography. It is likely that dynamic properties of the IgE receptor contribute to the activation of these responses. Fewtrell and Metzger have established that limited crosslinking of IgE-receptor complexes is essential to trigger secretion. In addition, Baird and colleagues have reported that antigen binding causes a rapid immobilization of IgE-receptor complexes, and we have demonstrated an apparent increase with time in the affinity of IgE-receptor complexes for antigen.
Ultrastructure of fat body trophocytes in the life stages of Dermacentor variabilis (Say)
Authors: Coons Lewis B. , Lamoreaux William , Rosell-Davis Rosemarie , Starr-Spires Linda
Published: June 2020

The American dog tick, Dermacentor variabilis (Say), has three life stages: larva, nymph, and adult. Each stage requires a blood meal to molt to the next stage or to reproduce and each stage has a fat body. A light microscopic study found two cell types in the fat body of this tick. The,fat body of a related tick produces vitellogenin during oviposition. The purpose of this study was to examine the ultrastructure of the fat body in the life stages of D. variabilis.

Ticks were from a colony maintained at Memphis State University. Ticks were fed on rabbits. Tissue was fixed in situ in 2.5% glutaraldehyde in 0.1M sodium cacodylate, pH 7.2 for 1 hour, post-fixed in 1% OsO4 in the same buffer, dehydrated in an ascending series of acetone and embedded in Epon Araldite. Sections were examined in a Zeiss 10A TEM operated at 60KV.
Evaluation of the arsenic inclusion using CTEM, STEM, and HVEM
Authors: Sorensen E. M. B. , Ramirez-Mitchell R.
Published: June 2020

The electron dense arsenic inclusion was first reported to occur in the nucleus of hepatocytes of Lepomis cvanellus. a freshwater species of sunfish, following laboratory exposures of this species to solutions of arsenate. Markedly elevated levels of arsenic were reported in the livers of the green sunfish, apparently due to the enterohepatic redistribution of the metalloid following biliary excretion. A maximum of approximately 50 and 160 ppm arsenic was found in the liver and bile, respectively, following a 6-d exposure of these fish to 60 ppm arsenic at 20°C. Translocation of arsenic from a cytoplasmic to nuclear location occurred during a 6-d period, ultimately leading to an increase in the size and number of intranuclear inclusions in the parenchymal hepatocytes. Microprobe analysis data indicated that the inclusion was composed of arsenic in a one to six ratio with sulfur.
High-resolution electron microscopy of surfaces: Profile views and front views
Authors: Nihoul G.
Published: June 2020

High resolution electron microscopy images of crystals are obtained by making some beams, diffracted by the crystal, interfere with the transmitted beam. For some experimental conditions, to be carefully defined for each specimen, the image can be shown to represent atomic columns; thus information in the atomic range is obtained, though it must be stressed that interpretation of these structure images must be done carefully as artefacts can give effects not linked with the crystal structure. In the last 3 years, this technique has been applied to the study of surfaces where it has given some striking results.
Knockcn surface diffusion
Authors: Ma Y. , Marks L. D.
Published: June 2020

There is growing interest in the use of electron microscopy to study surfaces. Unfortunately, the electron beam used to obtain images can also lead to surface modifications. Two processes can occur: electronic transitions which become converted into atomic motion leading either to preferential desorption of one species or athermal surface diffusion, and ballistic surface sputtering or diffusion. We report here preliminary theoretical results for this latter process, athermal surface diffusion due to ballistic Rutherford scattering.