bluuebunny/crossref_metadata_2025 huggingface dataset:
Z-Contrast Imaging of Grain Boundaries in Semiconductors
Authors: Chisholm M. F. , Pennycook S. J.
Published: June 2020

Interest in grain boundaries in semiconductors is linked to the application of polycrystalline semiconductors as photovoltaic and interconnect materials. In real devices such as solar cells and MOS structures as well as future devices such as flat-panel displays, the intergranular regions of the polycrystalline solid have a significant effect on the flow of electronic current. These grain boundary barriers exist because the chemical potential of the boundary atoms are shifted from the bulk value by the change in local symmetry. The chemical potential is also changed by impurities, other structural defects, and other phases in the boundary. The lack of knowledge on the atomic structure of grain boundaries is, at present, the greatest barrier to advancements in the understanding of the electrical properties of these defects.

The advances of the last few years have provided the tools with which to probe these interfaces at the true atomic scale. One such tool is the high-resolution scanning transmission electron microscope installed at Oak Ridge National Laboratory (VG Microscopes HB603) that can form a 1.27Å electron probe. Images are formed by scanning the probe across a thin sample and using an annular detector to collect electrons scattered to high angles. Because the annular detector collects electrons scattered over a wide range of angles, phase correlations and dynamical diffraction effects are averaged by this annular integration. Thus, an image with incoherent characteristics is produced and retained to relatively large specimen thickness.
Electron Microscopy Over the Internet as an Outreach Tool
Authors: Cousens D. R. , Waddell D. , Cribb B. , Jones M. , Drennan J.
Published: June 2020

Microscopy is an ideal medium to explore the wider applications of science and technology within the community in science and technology awareness programs. It bridges many individual disciplinary areas in science allowing many different facets of science and technology to be presented within a familiar framework.

The development of low cost video-audio conference software at Cornell University and the concurrent installation of Internet connections in Queensland schools at both primary and secondary level have provided an opportunity to enhance the science awareness and community service aspects of the Centres’ operation beyond physical visits by school groups. This increases dramatically the potential audience that can be reached for a given investment of time. It also allows school communities in the more remote areas of the state to have some access to advanced scientific instruments and the applications for which they are used. The project is being initially piloted with schools in regional areas around Brisbane as this provides immediate feedback in the exploratory stages of the program.
A 200kV Comprehensive Analytical Electron Microscope
Authors: Tomita T. , Kawasaki M. , Takeguchi M. , Honda T. , Kersker M.
Published: June 2020

With the use of a high-brightness electron source, the performance of the analytical electron microscope (AEM) has significantly improved. It features a variety of sophisticated analytical functions, such as X- ray spot analysis, area analysis, electron beam energy analysis, electron diffraction, and phase analysis using a biprism for holography. Here, we report the results of our analysis using a 200kV comprehensive AEM which has an integrated ZrO/W emitter as its optic source. The AEM (JEM- 2010F) is equipped with an X-ray energy dispersive spectrometer (EDS), scanning image observation device (ASID), parallel detection electron energy loss spectrometer (PEELS), and TV camera.

(1) X-ray mapping using EDS and ASID With FEG, the probe current in a 1 nm probe is increased by two-order orders of magnitude, and the background noise generated near the sample and in the illumination system is minimized. As a result, EDS analysis features high sensitivity at a minimum detection of 1% weight fraction from an ultra-micro area of lnm diameter.
STEM investigation of the chemistry and bonding changes associated with the grain boundary embrittlement of Cu by Bi
Authors: Keast V. J. , Bruley J. , Williams D. B.
Published: June 2020

It has long been known that trace amounts of Bi can embrittle Cu after appropriate heat treatments. The Bi segregates to the grain boundaries and weakens them such that failure occurs through intergranular fracture without plastic deformation. This behavior is demonstrated in the scanning electron micrograph of a typical Cu-Bi fracture surface in Figure 1. It is known that the Bi extends for only a few atomic layers into the grains on either side of the grain boundary. This narrow segregation width was been confirmed using Energy Dispersive X-ray Spectroscopy (EDS) on a VG HB603 STEM. Figure 2 shows the ratio of Bi to Cu as the probe is stepped across the grain boundary.

The segregation behavior is well understood, however it is not yet properly understood how the Bi causes embrittlement once it is at the grain boundaries. The Bi must change the bonding at the boundaries so that the boundaries become weak and hence the most likely fracture path. The Electron Energy Loss Near Edge Structure (ELNES) coupled with the small probes and high current density available in a field emission STEM can provide information about the localized electronic structure and hence bonding at grain boundaries. Previous investigations indicated that the near edge structure of Cu was altered at the grain boundaries due to the presence of Bi.
EXELFS study of the structure of silica and sodium silicate glasses
Authors: Winkler Dennis C. , Williams David B. , Jain Himanshu
Published: June 2020

The conventional extended X-ray absorption fine structure (EXAFS) method is not ideal for determining local structure around light elements in a solid. Although the “electron yield” EXAFS technique can be used to increase sensitivity to lighter elements, it is mainly a surface technique. We have employed the extended energy-loss fine structure (EXELFS) technique for determining the local structure (partial radial distribution function, inter atomic distance, and disorder parameter) in oxide glasses, specifically around Si and O in silica and sodium silicate glasses. Because a scanning transmission electron microscope is used, EXELFS also allows high spatial resolution which is particularly useful for a glass prone to phase separation.

EXELFS results from the same phenomenon responsible for EXAFS, namely the interference of the
outgoing spherical wave of the ejected electron with portions of itself which have been backscattered
from the neighboring atoms in the solid. This produces oscillations in intensity beyond the absorption edge. These variations in intensity are transformed to radial distribution functions in the same fashion as EXAFS data. EXELFS, like EXAFS, provides local atomic environment information that is element specific.
Tomography of paracrystalline specimens
Authors: Taylor Kenneth A. , Winkler Hanspeter
Published: June 2020

3-D image reconstruction of objects with no symmetry are produced by combining images of specimens tilted at finely spaced intervals about a single tilt axis. Image fiducials, usually gold particles applied to the surface of the specimen, are used to orient and align the separate views and 3-D images calculated by back projection methods. Electron microscope tomography has developed into a powerful method for producing a 3-D image of objects lacking crystalline symmetry. Crystalline objects are usually reconstructed using Fourier based methods that produce averaged 3-D images. Electron crystallography has become a powerful tool for solving the 3-D structure of proteins at atomic resolution.

Paracrystalline objects lie between crystalline and nonperiodic specimens because part of their structure is often well ordered but they have as well a significant disordered part. Muscle is one of the more notable members of this type of specimen because often the actin and myosin filaments form a well ordered array but the crossbridges, i.e. the motor domain of myosin, are much more disordered.
Digital imaging: When should one take the plunge?
Authors: Mansfield John F.
Published: June 2020

The current imaging trend in optical microscopy, scanning electron microscopy (SEM) or transmission electron microscopy (TEM) is to record all data digitally. Most manufacturers currently market digital acquisition systems with their microscope packages. The advantages of digital acquisition include: almost instant viewing of the data as a high-quaity positive image (a major benefit when compared to TEM images recorded onto film, where one must wait until after the microscope session to develop the images); the ability to readily quantify features in the images and measure intensities; and extremely compact storage (removable 5.25” storage devices which now can hold up to several gigabytes of data).

The problem for many researchers, however, is that they have perfectly serviceable microscopes that they routinely use that have no digital imaging capabilities with little hope of purchasing a new instrument.
Heterogeneous solid-state reactions between MgO(00l) and iron oxide
Authors: Johnson Matthew T. , Schmalzried Hermann B. , Carter C. Barry
Published: June 2020

The transport properties of the diffusing species in heterogeneous solid-state reactions are affected by concentration gradients, temperature gradients, stress fields and electric fields. In the present study, interfacial reactions between thin films of iron oxide and bulk monocrystalline MgO{001}, resulting in the formation of the spinel product MgFe2O4, were carried out separately as a function of time and temperature, applied external electric field and partial pressure of oxygen. Electron microscopy techniques have been utilized to investigate the reaction kinetics and interface morphology.

The reaction couples were produced by means of pulsed-laser deposition (PLD). The setup for PLD has been described elsewhere. By depositing high-quality oxide films on bulk substrates, a well controlled geometry can be fabricated which is conducive to the study of fundamental processes in solid-state reactions. In producing the reaction couples, 600nm of iron oxide was deposited on monocrystalline MgO{001}. The reaction couples were then reacted under varying conditions and analyzed, using both scanning (SEM) and transmission electron microscopy (TEM).
Nucleation and growth of SrTiO3on Nanometer-Sized BaTiO3particles
Authors: Chun C. M. , Navrotsky A. , Aksay I. A.
Published: June 2020

The hydrothermal processing of either BaTiO3or SrTiO3can result in the formation of nanometer-sized particles. Despite agreement on the mechanism of dissolution and precipitation, there remains some controversy concerning the nucleation and growth mechanism of the particles, particularly on the appearance of “raspberrylike” BaTiO3particles in the early stage of growth. The controlled aggregation of primary particles by multiple clustering or morphological instability of continuous growth by molecular addition have been proposed as possible mechanisms. Similarly, the role of supersaturation during precipitation leading to the formation of colloidal BaTiO3particles is not yet understood. Our TEM studies using the growth of SrTiO3on BaTiO3seed particles reveal that two different morphologies for the growing SrTiO3exist and that the form taken by the SrTiO3depends on the degree of supersaturation.

Nanometer-sized BaTiO3seed particles were hydrothermally treated in both dilute (0.4M) and concentrated (2.0M) supernatant solutions prepared by reacting TiO2(Degussa, P-25) in an aqueous solution of Sr(OH)2at 80°C for 4 hours followed by centrifugation.
Stacking sequences of the crystallites in Co-Sm films
Authors: Robertson B. W. , Liu Y.
Published: June 2020

Magnetic thin films sputtered from the Co-Sm system have been shown to be promising as recording media. High coercivities of up to 4.0 kOe have been obtained from Co-Sm films. Recent microstructure characterization of Co-Sm films deposited by the DC magnetron sputtering has shown that the microstructure is composed of the amorphous matrix and crystallites with a grain size of about 5nm . As different sputtering processes have different dynamics for the formation of the nanostructure, phases formed could be different from those predicted by the equilibrium phase diagram. Crystal structure determination is important for understanding the high anisotropy and epitaxy growth of the Co-Sm films. The crystal structure of the crystallites was identified to be a close-packed structure. However, the stacking sequence changes from crystallite to crystallite. This paper describes the detailed high resolution electron microscopy (HREM) study of the stacking sequence of the crystallites in Co-Sm films. It is found that the stacking near the Cr underlayer tends to be hexagonal (ABAB) stacking. As the film grows, the stacking sequence is disturbed and three layer stacking, four layer stacking and random stacking are formed.
Electron behavior in the gaseous environment of the ESEM chamber
Authors: Wight S.A.
Published: June 2020

Measurements of electrons striking the sample in the Environmental Scanning Electron Microscope (ESEM) are needed to begin to understand the effect of the presence of the gas on analytical measurements. Accurate beam current is important to x-ray microanalysis and it is typically measured with a faraday cup. A faraday cup (Figure 1) was constructed from a carbon block embedded in non-conductive epoxy with a 45 micrometer bore platinum aperture over the hole. Currents were measured with an electrometer and recorded as instrument parameters were varied.

Instrument parameters investigated included working distance, chamber pressure, condenser percentage, and accelerating voltage. The conditions studied were low vacuum with gaseous secondary electron detector (GSED) voltage on; low vacuum with GSED voltage off; and high vacuum (GSED off). The base conditions were 30 kV, 667 Pa (5 Torr) water vapor, 100,000x magnification with the beam centered inside aperture, GSED voltage at 370 VDC, condenser at 50%, and working distance at 19.5 mm. All modifications of instrument parameters were made from these conditions.
High performance Nanogold™-in situ hybridzation and its use in the detection of hybridized and PCR-amplified microscopical preparations
Authors: Hacker G. W. , Zehbe I. , Hainfeld J. , Graf A.-H. , Hauser-Kronberger C. , Schiechl A. , Su H. , Dietze O.
Published: June 2020

In situ hybridization (ISH) with biotin-labeled probes is increasingly used in histology, histopathology and molecular biology, to detect genetic nucleic acid sequences of interest, such as viruses, genetic alterations and peptide-/protein-encoding messenger RNA (mRNA). In situ polymerase chain reaction (PCR) (PCR in situ hybridization = PISH) and the new in situ self-sustained sequence replication-based amplification (3SR) method even allow the detection of single copies of DNA or RNA in cytological and histological material. However, there is a number of considerable problems with the in situ PCR methods available today: False positives due to mis-priming of DNA breakdown products contained in several types of cells causing non-specific incorporation of label in direct methods, and re-diffusion artefacts of amplicons into previously negative cells have been observed. To avoid these problems, super-sensitive ISH procedures can be used, and it is well known that the sensitivity and outcome of these methods partially depend on the detection system used.
Large-angle convergent-beam electron-diffraction study of coherent precipitates and decorated dislocations
Authors: Wiezorek J.M.K. , Fraser H.L.
Published: June 2020

Conventional methods of convergent beam electron diffraction (CBED) use a fully converged probe focused on the specimen in the object plane resulting in the formation of a CBED pattern in the diffraction plane. Large angle CBED (LACBED) uses a converged but defocused probe resulting in the formation of ‘shadow images’ of the illuminated sample area in the diffraction plane. Hence, low-spatial resolution image information and high-angular resolution diffraction information are superimposed in LACBED patterns which enables the simultaneous observation of crystal defects and their effect on the diffraction pattern. In recent years LACBED has been used successfully for the investigation of a variety of crystal defects, such as stacking faults, interfaces and dislocations. In this paper the contrast from coherent precipitates and decorated dislocations in LACBED patterns has been investigated. Computer simulated LACBED contrast from decorated dislocations and coherent precipitates is compared with experimental observations.
Investigation of AerMet100 segregation behavior during casting and homogenization by quantitative electron microscopy and thermodynamic/kinetic modeling
Authors: Lippard H.E. , Campbell C.E. , Dravid V.P. , Olson G.B.
Published: June 2020

Dendritic segregation of alloying elements during solidification results in non-uniform chemical and mechanical properties of steels. Homogenization can reduce the composition imbalances and restore uniformnity of mechanical properties. AerMet100 is a high alloy steel produced in wrought forms by Carpenter Technology, Inc. for applications requiring a combination of high strength, high fracture toughness, and resistance to stress corrosion cracking. The nominal composition is (wt%) 13.4% Co, 11.1% Ni, 3.1% Cr, 1.2% Mo, 0.23% C, and the balance Fe. Recent studies of cast and homogenized AerMet100 have demonstrated the mechanical properties approaching the high levels of wrought AerMet100. Optimization of a homogenization treatment for elimination of the microsegregation developed during solidification was completed using thermodynamic/kinetic modeling and quantitative energy dispersive spectrometry (EDS) in scanning electron microscopy.

The as-cast alloy has the classic fern-like dendritic structure shown in Figure 1. The primary dendrite arm spacing was 150-400 μm and the secondary arm spacing was 70-110μm.
Molecular Surface Imaging of Particles Using Microprobe Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)
Authors: Linton R.W. , Fister T.F. , Summers S.S. , Strossman G.S. , Holland M.J. , Odom R.W.
Published: June 2020

The objective of this research is to develop imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) to characterize ultra-thin organic films on microscopic particles. An initial application is to evaluate the surface chemistry of polycyclic organic matter (POM) on combustion-generated particles as an area of fundamental interest in the assessment of the environmental fate and impact of carcinogenic pollutants.

Controlled deposition of POM monolayers was achieved using either gas or solution phase coating on model particles such as silica, as well as on authentic environmental particles such as coal flyash or soot. Another aspect of the work was to monitor surface transformations of adsorbed POM involving photochemical degradation or reactions with gaseous pollutants such as nitrogen oxides. For the first time, variations in POM adsorption and reactivity have been probed as a function of particle type by the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to perform surface analysis on single particles. Results using a pulsed gallium microbeam source on a TOF-SIMS indicated that 0.1 monolayer coverages of individual POM species can be detected as quasimolecular ions from single particles with diameters typically in the 5 μm range. Primary ion doses were <1013 ions/cm2 to minimize surface damage during a typical 10 min spectrum acquisition from an 40x40 ftm image field. Correlation of in situ measurements using TOF-SIMS with traditional solvent extraction and chromatographic results, including LC or GC-MS, allowed for more detailed assessments of the sensitivity and quantitative capabilities of TOF-SIMS. The combination of monolayer analysis with microanalysis creates severe challenges to sensitivity since the total number of molecules within the analytical volume is so small (< 107 POM molecules on a lμm2 particle area)
Modeling of dissolution and resolution in contact x-ray microscopy
Authors: Wang Y. , Jacobsen C.
Published: June 2020

Contact x-ray microscopy or microradiography offers a simple-to-use approach to high resolution imaging of wet, thick biological specimens. One great advantage of the technique is that it can be usedwith short pulse, incoherent x-ray sources such as laser produced plasmas, and polymer replicas or direct AFM viewing are promising new approaches to image readout. However, it has long been pointed outthat issues such as diffraction blurring over finite sample-to-resist spacing, shot noise in the exposure, and sidecutting during development must be considered in evaluating contact x-ray microradiographs.

We present here the results of numerical modelling of contact x-ray microscopy using photoresists. We assume a phantom consisting of protein rods and balls of different diameters, all embedded in a water layer. We assume that the x-ray exposure is provided by a black body source with temperature kBT = 100 eV (such as in a laser-produced plasma), and that the black bodyspectrum is then modified by x-ray transmission in 0.1/μm of Al2O3, 0.1μm of Si3N4, and 5μm of water.
X-ray Gabor holography: Recent progress
Authors: Lindaas Steve , Jacobsen Chris , Kalinovsky Alex , Howells Malcolm
Published: June 2020

Gabor holography is well positioned to exploit flash x-ray sources, such as x-ray lasers and free electron lasers, as well as ultra-bright third generation synchrotron sources as a sub-50 nm resolution imaging technique for biological samples. Gabor holography requires no optics (except for a monochromator with λ/Δλ ~ 500) and no sample prefocusing since the image is focused in the reconstruction process. Furthermore, sample alignment is eased since the area of illumination can be quite large. In fact, Gabor holography can be used to image large fields with multimode sources with the resulting numerical aperture, and hence resolution, being limited by the size of a single mode. However, Gabor holography is not a real time technique so there is no rapid feedback to improve the immediate experiment. In addition, the resolution has been limited by shortcomings in the reconstruction methods.

Our primary emphasis has been on biological imaging so we use x-rays in the water window (between the O-K and C-K absorption edges).
Integration of olfactory, gustatory and other sensory stimuli in the orbitofrontal cortex: Feeding and reward
Authors: Price J. L.
Published: June 2020

Olfactory sensory information is transferred through the olfactory bulb to the primary olfactory cortex, an extensive paleocortical region that occupies the entire ventral surface of the forebrain in rats, although it is restricted to a relatively smaller area in primates. While much of the analysis and discrimination of olfactory stimuli occurs in the primary olfactory cortex, further axonal projections carry olfaction related activity to other brain structures, including the medial thalamus, the orbitofrontal cortex and the ventral part of the basal ganglia. The organization of extensive interactions among these structures, and between them and other parts of the brain, indicates that they provide the basis not only for further analysis of olfactory stimuli, but also for integration of olfaction with taste and other sensory modalities related to feeding, and possibly for stimulus-reward association.

To analyze this system, multiple axonal tracers, some of them transmitter specific, have been used in association with histochemical and immunohistochemical staining and electrophysiological recording.The tracer labeling was mapped with a computer aided microscope that allow the distribution of labeled cells and other markers to be determined over large brain sections. The distribution was then further analyzed by computer reconstructions of serial sections.
3-Dimensional immunolabeling and in situ hybridization detection using fluorescence photooxidation and intermediate-voltage Electron Microscopy
Authors: Deerinck Thomas J. , Martone Maryann E. , Lev-Ram Varda , Green David P. L. , Tsien Roger Y. , Spector David L. , Huang Sui , Ellisman Mark H.
Published: June 2020

The confocal laser scanning microscope has become a powerful tool in the study of the 3-dimensional distribution of proteins and specific nucleic acid sequences in cells and tissues. This is also proving to be true for a new generation of high contrast intermediate voltage electron microscopes (IVEM). Until recently, the number of labeling techniques that could be employed to allow examination of the same sample with both confocal and IVEM was rather limited. One method that can be used to take full advantage of these two technologies is fluorescence photooxidation. Specimens are labeled by a fluorescent dye and viewed with confocal microscopy followed by fluorescence photooxidation of diaminobenzidine (DAB). In this technique, a fluorescent dye is used to photooxidize DAB into an osmiophilic reaction product that can be subsequently visualized with the electron microscope. The precise reaction mechanism by which the photooxidation occurs is not known but evidence suggests that the radiationless transfer of energy from the excited-state dye molecule undergoing the phenomenon of intersystem crossing leads to the formation of reactive oxygen species such as singlet oxygen. It is this reactive oxygen that is likely crucial in the photooxidation of DAB.
Characterization of protein-lipid interaction and redistribution of minerals in infant formula by CTEM and EDS
Authors: Hendricks G. M. , Guo M. R. , Kindstedt P. S.
Published: June 2020

The protein-protein and protein-lipid interactions in 3 commercial powdered infant formulae were compared to raw and pasteurized milk samples. Centrifugation of the infant formulae and milk samples for 2 hr at 4°C gave 3 distinct fractions: fat, serum, and pellet. The objective of this study was to determine the mineral distribution (i.e., Ca, P, Mg, K, Na, Zn, and Fe) among the fat, serum and pellet fractions obtained by centrifugation. Recoveries of individual minerals from the 3 fractions exceeded 90% in all cases. Ca in the fat fraction of infant formulae ranged from 17.5% to 32%, where as only 1.4% and 1.7% of the total Ca was recovered in the fat fraction of the raw milk and the pasteurized milk samples. P, Zn, Mg, and Fe followed similar patterns with respect to the fat fraction. In contrast, 80 to 90% of the K and Na were found in the serum fraction of the infant formulae and milk samples.
Corbular (CSR) and extended junctional SR (EJSR) in skeletal muscle
Authors: Sommer J. R. , High T. D. , Taylor I.
Published: June 2020

Excitation-calcium release (ECR) is one of the first steps in excitation-contraction coupling in striated muscle. In skeletal muscle, there is some evidence that ECR depends on physical interaction between electrical activity at the plasmalemma (PL) and intracellular calcium stores (junctional sarcoplasmic reticulum; JSR). In cardiac muscle, there is very strong evidence for signal transmission from PL through the release of a diffusible transmitter substance, initially at couplings (= JSR tightly apposed to PL). Avian cardiac muscle has no transverse tubules (TT) but JSR, both as part of peripheral couplings (25%) and as extended JSR (EJSR) unattached to PL (75%). A subset of EJSR, corbular SR (CSR), occurs in small numbers in mammalian hearts and, topographically, fills in wherever TT and, thus, interior couplings (i.e. JSR) are missing. The total volume fraction of avian EJSR (75%) + JSR (25%) is identical to murine JSR (>90%) + CSR (< 10%). JSR-total (JSR, EJSR, CSR) establishes calcium release sites at about equidistant locations throughout the volume of a myocyte. Whereas, in avian hearts a signal for calcium release initiated at a peripheral coupling must be propagated transversely for up to 4 μm (cell radius) by quasi “saltatory” propagation of calcium-induced calcium release (CICR) along the EJSR’s junctional processes (JPs = ryanodine sites) eliciting calcium release for contraction at each contact, in mammalian cardiac and in skeletal muscle calcium release is effected in a one-step process through a propagated action potential kickstarting calcium release at each of a string of peripheral and interior couplings located along TT.
Free-radical-derived oxidants and ocular pathology in a model of chronic hypoxia
Authors: Ellis E. Ann , Holmes Gerard , Grant Maria B.
Published: June 2020

Hypoxia, whether systemic or localized, plays a role in a number of ocular pathologies. Systemic hypoxia results from cardiovascular or pulmonary abnormalities; localized hypoxia can result from regional vascular blockage or chemical hypoxia as observed in diabetes. Free radical derived oxidants have been implicated in the pathogenesis of vascular and other complications of hypoxia. We studied eyes to determine if there were similarities between the morphological components of diabetic retinopathy and chronic hypoxic retinopathy. Using the cerium NADH-oxidase cytochemical technique to localize the free radical derived oxidant, hydrogen peroxide (H2O2), we investigated the sites and role of oxidative injury in eyes from a rabbit model of chronic systemic hypoxia.

New Zealand albino rabbits, reared in a normobaric, hypoxic chamber (65±3 mm Hg) [normoxia = 149 mm Hg], were removed at ages five weeks (immature) or twelve weeks (mature). Animals were euthanized with pentobarbital; eyes were enucleated, fixed and processed for NADH-oxidase localization.
Characterization of morphological and cytotoxic changes of peripheral blood lymphocytes induced by Interleukine-2
Authors: Wang Fen , Head Jonathan F. , Elliott Robert L.
Published: June 2020

Interleukine-2 (IL-2) is a cytokine of central importance in the regulation of human immune responses. It stimulates peripheral blood lymphocyte (PBL) expansion and induces augmentation of their cytotoxicity. Recent studies have demonstrated marked heterogeneity in the response capacity of PBL to IL-2. In this study the expansion, cytotoxicity and ultrastructure of PBL obtained from breast cancer patients following stimulation with IL-2 were examined. The PBL were separated by Histopaque density gradient centrifugation and cultured in RPMI 1640 with 10% human AB serum for 7 days. 1000 units IL-2 were added in the culture for activating PBL invitro.

When compared to resting PBL (Fig. 1a) the cytotoxicity of IL-2 stimulated cells against MTF-7(T20) rat tumor cells was enhanced. These activated PBL were larger and consistently displayed the shape and cytoskeletal rearrangement characteristic of activation (Fig. 1b and 1c). The cytoplasm was expanded, and the number of electron-dense granules and vesicles were increased (Fig.2 and Fig. 3). These ultrastructural alterations indicate that IL-2 enhances the lytic ability of PBL through changes in the cell machinery.
Three-Dimensional reconstruction of atherosclerotic foam cells using tomosynthesis
Authors: Grant K. W. , Webber R. , Horton R. , Jerome W.G.
Published: June 2020

Thick specimens viewed by IVEM often have confusing superposition of features at different depths. To overcome this, a variety of techniques for separating depth have been used, i.e. stereo pair micrographs, serial reconstruction, and computed tomography. Tomosynthesis, a form of tomography, is an attractive alternative which has been applied to radiology samples. Like tomography, a 3-D reconstruction is produced from a series of images at separate viewing angles. However, the reconstruction is formed by registering and summing images rather than backprojection. Objects in the plane of focus are distinct due to superposition of identical pixels. A new focal plane is obtained by laterally shifting projections. Although not as complete a reconstruction as full tomography, tomosynthesis is fast, efficient, and requires a limited number of tilt angles. We have adapted tomosynthesis for IVEM to study atherosclerotic cellular lipid accumulation. Previously we showed that lipid is trapped within large lysosomes as part of the disease process. This lysosomal-engorgement is accompanied by formation of interconnected tubules also rich in acid hydrolases.
Environmental scanning electron microscopy of microcomedones
Authors: Hoyberg K. , Knaggs H.
Published: June 2020

Environmental Scanning Electron Microscopy (ESEM) combines the best features of conventional SEM (high resolution, depth of field) with the flexibility and ease of light microscopy. This is accomplished by the incorporation of a four stage differential pumping system and the utilization of a gaseous detector. These modifications allow the direct observation of wet, dry, and nonconductive specimens without sample preparation.

In vivo methods for assessing the effectiveness of acne therapies are time consuming and require recruiting, treating and monitoring patients for several weeks. ESEM is an ideal technique to study, in vitro, changes that occur in microcomedone structures during treatment with anti-acne agents. The samples are viewed in their natural state, and can therefore be viewed before and after treatment.

Microcomedones extracted by cyanoacrylate biopsy technique were examined via ESEM Approximately 4-5 areas per sample were selected. These areas were chosen to include small and large microcomedones, with or without vellus hairs and or microorganisms. Images of each area were recorded by electronic imaging and the coordinates of the areas stored via the instrument's computer.
The promises and perfidy of cryomicroscopy and analysis
Authors: Echlin Patrick
Published: June 2020

The unusual title of this short paper and its accompanying tutorial is deliberate, because the intent is to investigate the effectiveness of low temperature microscopy and analysis as one of the more significant elements of the less interventionist procedures we can use to prepare, examine and analyse hydrated and organic materials in high energy beam instruments. The promises offered by all these procedures are well rehearsed and the litany of petitions and responses may be enunciated in the following mantra.

Vitrified water can form the perfect embedding medium for bio-organic samples.

Frozen samples provide an important, but not exclusive, milieu for the in situ sub-cellular analysis of the dissolved ions and electrolytes whose activities are central to living processes.

The rapid conversion of liquids to solids provides a means of arresting dynamic processes and permits resolution of the time resolved interactions between water and suspended and dissolved materials.

The low temperature environment necessary for cryomicroscopy and analysis, diminish, but alas do not prevent, the deleterious side effects of ionizing radiation.

Sample contamination is virtually eliminated.
High-performance transmission scintillating screen for TEM
Authors: Fan G. Y. , Dunkelberger Dana G. , Ellisman Mark H.
Published: June 2020

A scintillating screen is an indispensable component of a slow-scan CCD (charge-coupled-device) camera system for transmission electron microscopy. Its performance is therefore of great concern because of its influence on the overall performance of the system. Screens produced by deposition of phosphor on a thin metal foil appear to be attractive particularly for intermediateand high voltage applications. The metal foil serves three purposes: (1) support for the phosphor; (2) charge conductor; and (3) light reflector. Vacuum deposited, thin aluminum foils serve these purposes well. We report here briefly the brightness and resolution of a scintillating screen composed of a 10 μm layer of P20 phosphor deposited on 2 μm Al foil. More detailed characterization of the screen can be found elsewhere. Results are compared to that of a screen made by depositing a similar layer of phosphor onto a glass plate, and that of a 0.5 mm YAG screen.

Fig. 1 illustrates schematically the structure of the aluminum screen.
Voltage-center COMA-free alignment for high-resolution Electron Microscopy
Authors: Ishizuka K. , Shirota K.
Published: June 2020

In a conventional alignment for high-resolution electron microscopy, the specimen point imaged at the viewing-screen center is made dispersion-free against a voltage fluctuation by adjusting the incident beam direction using the beam deflector. For high-resolution works the voltage-center alignment is important, since this alignment reduces the chromatic aberration. On the other hand, the coma-free alignment is also indispensable for high-resolution electron microscopy. This is because even a small misalignment of the incident beam direction induces wave aberrations and affects the appearance of high resolution electron micrographs. Some alignment procedures which cancel out the coma by changing the incident beam direction have been proposed. Most recently, the effect of a three-fold astigmatism on the coma-free alignment has been revealed, and new algorithms of coma-free alignment have been proposed.

However, the voltage-center and the coma-free alignments as well as the current-center alignment in general do not coincide to each other because of beam deflection due to a leakage field within the objective lens, even if the main magnetic-field of the objective lens is rotationally symmetric. Since all the proposed procedures for the coma-free alignment also use the same beam deflector above the objective lens that is used for the voltage-center alignment, the coma-free alignment is only attained at the sacrifice of the voltage-center alignment.
A case of the shakes: Resonance in a microscope mounting system
Authors: Garratt-Reed Anthony J.
Published: June 2020

That electron microscopes, especially modern, high performance ones, are susceptible to environmental interference, is well known. The author, aware of this susceptibility, has nevertheless experienced what were, to him, initially surprising difficulties in commissioning a new instrument. He offers this paper in the hope that it may help others avoid the pitfalls which so easily engulfed him.

The microscopy area at MIT was constructed fourteen years ago after two different manufacturers' installation engineers surveyed the space and declared it satisfactory. The microscopes installed at that time performed well and met their specifications with no difficulty - in the case of those that are still on-site, they continue to do so to this day.

Five years ago an ultra-high resolution TEM was installed. It was mounted on a series of synthetic rubber vibration absorbing pads. It proved difficult to meet the performance specifications on this instrument, despite the company service engineers checking the site and passing it as satisfactory. The specification was 0.18nm point-topoint, while the achievable resolution was 0.25nm.
Differential contrast enhancement of digital image information by PC-based massively parallel processing
Authors: Jenkins David R.
Published: June 2020

Digital images represent two-dimensional intensity maps which characterize the spacial x/y distribution of contrast information. Often, small detail contrasts are visaully unrecognizable due to the prevalence of large contrast components which, inversely proportional to their extent, compress the intensity range of the detail contrasts. A new “pixel-accurate intensity processing” (PAIP) technology provides unrestricted access to and display of all detail information contained in digital images independent of content, size and depth (8-16 bit). It offers an exciting new way for objective and exhaustive digital image evaluation in near-real-time.

We developed a PC-based massively parallel processing workstation (PiXision) for fast, artifact free differential contrast extraction utilizing the PAIP technology. Information extraction and enhancement requires only a few digital processing steps (Fig. 1): 1. The original image is smoothed with pixelaccurate precision within a significant intensity range (IRS) using the PAIP technology; 2. The smoothed image may additionally be subtracted from the original generating a detail image; 3. Finally, the smoothed or detail images are linearly scaled to 8-bit providing full visual intensity range. The basic software routine “smoolhens” an image to any significant intensity range without spacial artifacts, using a variable automatically adjusting local mask for pixel averaging.
Transmission electron spectroscopy and interferometry of electroceramic oxides
Authors: Dravid Vinayak P. , Lin X. , Ravikumar V. , Rodrigues R. , Wilcox N.
Published: June 2020

Research on ferroelectricity and related phenomena has come a long way since the discovery of hysteretic nonlinearity of polarization in "Rochelle Salt" by J. Valasek in 1920's. Ever since the discovery, microstructural issues have dominated the field. With the current trends in using ferroelectric and related oxides in nanocrystalline and thin film forms, techniques for microstructural analysis for such specimens are becoming more sophisticated.

We are currently investigating nanocrystalline TiO2 as a model system to examine size dependency of electronic structure in nanocrystals, as reflected in their energy loss spectra. Electron beam evaporated nanocrystals of TiO2 (size ranging from 2 - 10 nm) have been examined with transmission EELS with a ~ 0.8 nm electron probe of our HF-2000 FE TEM. The particles were dispersed on a holey carbon grid and those protruding into the holes were analyzed for changes in valence and core loss spectra as a function of nominal particle size. The plasmon loss energies were observed to increase with decrease in particle size.
Identification of the polarized microregions in PLZT
Authors: Zhang J. P. , Speck J. S.
Published: June 2020

Relaxor ferroe lee tries are classified by broad or diffuse transitions from their high temperature paraelectric (non-polar phase) to their low temperature ferroelectric phase. This is in contrast to conventional ferroelectrics such as PbTiO3 that show discrete ferroelectric transitions characterized by Curie-Weiss behavior in the dielectric susceptibility near the Curie transition temperature Tc. For relaxor ferroelectrics, the transition has a breadth on the order of 100°C The polarized domains normally show complex nanoscale mottled contrast in either bright field or dark field, two-beam or systematic row scattering contrast images; as an example, this contrast is shown in Fig. 1. The nanoscale contrast appears to be intimately associated with the relaxor phase; however, the physical origins of the contrast remain unclear. It is known that in classical treatments of ferroelectrics, the polarization and strain are the primary order parameters for the paralelectric-ferroelectric phase transition. For classical first order ferroelectric transitions, such as in PbTiO3 or BaTiO3, there is a concurrently spontaneous polarization and strain. However, these order parameters need not be directly coupled, and it may be possible that through the relaxor transition, strain and polarization are uncoupled. In this experimental effort we will demonstrate techniques that separate strain contrast from structure factor contrast, the latter being associated with polarization or compositional fluctuations.
A study of microstructures in ferroelectric Pb(Zr,Ti)O3 and KNbO3 thin films
Authors: Kingon A. I. , Rou S. H. , Chen Y. L.
Published: June 2020

Oxide ferroelectric thin films are receiving considerable attention due to their potential application in a wide range of devices including ferroelectric nonvolatile memory, dynamic random access memory (DRAMs) electrooptic phase modulators, and laser light source frequency doublers. However, the complexity of the oxide materials has resulted in a relatively slow development of structureprocessing property relationships. In this paper, we review in turn how the microstructures of epitaxial KNbO3 and Pb(Zr Ti)O3 have been significantly improved over a period of time.

In the case of epitaxial KNbO3 on oxide single crystal substrates, defect types which need to be controlled include 221-type misorientations, low angle boundaries, multiposition domains, and inversion domains. Several of these defect types are controlled via the substrate surface preparation. The role of lattice mismatch between film and substrate on the formation of the low angle boundaries remains an unresolved issue. We are currently comparing via TEM the KNbO3(100) films on (100)MgO, (100)MGAl2O4, (100)NdGaO3 and (100)KTaO3 substrates; these substrates covering a range of values of lattice mismatch between 0.1% and 5.0%.
Electron diffraction in UHV SEM, REM, and TEM
Authors: Venables J. A. , Harland C. J. , Bennett P. A. , Zerrouk T. E. A.
Published: June 2020

Electron diffraction techniques are widely used in Surface Science, with the main aim of determining atomic positions in surface reconstructions and the location of adsorbed atoms. These techniques require an Ultra-high vacuum (UHV) environment. The use of a focussed beam in UHV electron microscopes in principle allows such techniques to be applied on a microscopic scale. Most obviously this has been achieved in the Low Energy Electron Microscope (LEEM), where the corresponding diffraction technique, LEED, can now be used to investigate local areas with different surface structures, and to follow both temperature and time evolution of these local structures. Some other geometries can be used to achieve similar goals. If the incident energy is raised, the incidence angle has to be moved from normal towards glancing, so that the 'perpendicular' energy is kept within the LEED range of 10-100 eV. Several reflection (REM) and scanning (SEM) instruments have been built with energies between 5 and lOOkeV. In general, the addition of RHEED to an UHV-SEM with Auger Electron Spectroscopy (AES) forms a very useful tool in Surface Science.
AEM of shock-synthesized niobium silicide composites
Authors: Strutt A. J. , Meyers M. A. , Vecchio K. S.
Published: June 2020

In-situ composites of thermodynamically compatible phases have been the subject of recent investigations and in particular, those comprising 2-phase Nb/Nb5Si3 structures. Chemical reactions initiated by high velocity shock waves can be extremely rapid and (unlike more conventional techniques) are capable of forming composite compounds with carefully controlled, fine-scale microstructures. The current investigation involves the use of SEM, TEM and EDX to fully characterize the microstructure of niobium silicide specimens (of initial bulk compositions Si 40 at.% Nb and Nb 33 at.% Si) formed by shock-synthesis of nominally 5 μm size particles in a powder gas gun at an impact velocity of 1.3 km/s.

Recovered specimens were in the form of 34 mm diameter × 7 mm thick disks. Metallographic sectioning and examination by SEM in the backscattered imaging mode showed that both disks had undergone a chemical reaction with the exception of the peripheral regions which were merely compacted. Examination was also performed using a Philips CM30 analytical TEM at 300 keV in addition to EDX with a Link Systems ultrathin window detector.