bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.