bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation damage and spatial resolution in the EXELFS of inorganic materials
Authors: Haskel D. , Sarikaya M. , Qian M. , Stern E. A. 
Published: June 2020

EXELFS, the extended energy loss fine structure superimposed on the high energy loss side past an inner-shell electron excitation in an EELS spectrum, contains quantitative information about the local structure around the scattering atom from which the core electron is excited, similar to that contained in the x ray absorption fine structure (XAFS). Main advantages of the EXELFS technique over XAFS include the relative ease in the former to study the local environments of low Z elements coupled to the higher spatial resolution, imaging and diffraction capabilities of the TEM.Radiation damage to the sample caused by the energetic electron beam, however, has been an important concern to whether EXELFS can be safely applied to study materials at the nanometer scale. To investigate this question we chose to study Al, SiC and MgO as representatives of three different classes of binding: metallic, covalent and ionic, with the belief that these should exhibit different sensitivities to different mechanisms of radiation damage and hence will be fair representatives of a wide variety of materials.
Corroded spent nuclear fuel examined with EELS
Authors: Buck Edgar C. , Dietz Nancy L. , Bates John K. 
Published: June 2020

Direct disposal of spent nuclear fuel (SNF) into the proposed unsaturated geologic repository at Yucca Mountain, NV is being studied at several laboratories, including Argonne National Laboratory. Corrosion tests with SNF are being conducted to understand the long-term behavior of SNF under conditions designed to simulate the unsaturated conditions at the site. The SNF used in this study was the Approved Testing Material (ATM)-106 with a bum-up of 43 MW·d/kg U. A sample of ATM-106 fuel was exposed to dripping simulated groundwater for 271 days; after this time the experiment was terminated and the material removed for further study. Details of the testing methodology have been given by Finn et al.,.Previous attempts to study SNF with TEM have used ion milled samples, in this study we prepared the samples by ultramicrotomy which reduced the radiological hazard substantially.
Investigation of copt and copt + ZrOx thin films for magnetic storage media using high-resolution analytical electron microscopy
Authors: Ristau R. A. , Barmak K. 
Published: June 2020

Materials for very high density magnetic storage media, with capacities of 10 Gbits/in2 and beyond, require high coercivity and high signal to noise ratio. To achieve storage densities of this level engineering of the material to produce very fine, magnetically decoupled domains is necessary. We have characterized the microstructure and microchemistry of 10 nm thick CoPt and CoPt + ZrOx thin films, as deposited and annealed, using transmission electron microscopy (TEM) and nanometer-scale energy dispersive x-ray spectroscopy (EDS).CoPt has a very high coercivity (Hc) when annealed to produce the ordered Ll0 phase. Annealing also increases grain size which reduces the signal to noise ratio. Co-sputtering CoPt with ZrOx was intended to reduce grain size. TEM micrographs in Figure 1 show that grain growth was dramatically reduced in the CoPt + ZrOx films. Essential to the development of optimum material properties are quantified grain size measurements, yet owing to the small grain size and the complexity of TEM images due to diffraction contrast there are few systematic studies of grain size in thin films.
An approximation to the dynamical calculation of rheed patterns from rough surfaces
Authors: Lordi S. , Eades J.A 
Published: June 2020

RHEED (reflection high energy electron diffraction) is a technique widely used in molecular beam epitaxy (MBE) and for the characterization of surfaces in other contexts. Despite its widespread use, however, the interpretation of RHEED has largely been limited to the use of positions of the reflections with no attempt made to use the intensities in the patterns.The reasons for this are related to the complexity of RHEED computations. There are several methods which can be used to calculate RHEED intensities from flat surfaces. However, in MBE (and other crystal growth methods) where RHEED is most often used, the surfaces are rough. Of the dynamical methods for calculating RHEED intensities from flat surfaces, only the modified Cowley-Moodie multislice method with the edge patching algorithm can be applied to rough surfaces without making severe approximations. This method is computationally intensive because the ensemble average over the statistical parameters of the surface cannot be done before the dynamical calculations.
Migrating to digital imaging from film
Authors: Minter J. R. , Schlafer K. , Sotak G. , Thom L. 
Published: June 2020

Since the invention of the microscope, most images were recorded on photographic film. For transmission electron images, Hamilton and Marchant recognized that most photographic films are “nearly perfect detectors, in that they record the input signal without appreciable loss and do not seriously add to the input noise”. Despite film's efficiency as an image recorder, microscopists complained about the long cycle time between image recording and completion of the final print. Quantitative image analysis of images recorded on film is also time-consuming and expensive because microdensitometers capable of producing high quality and high resolution scans of negatives are slow and expensive.Over the past few years several new technologies to record light and electron images have been commercialized. The oldest of these are video-rate cameras and TV-rate cameras built with charge coupled devices (CCDs). These are limited by small image size (512 × 478). Larger format digital cameras built using slow-scan CCD cameras have recently been applied to light and transmission electron microscopy. Digital scan generators and frame buffers have been added to scanning electron microscopes.
Practical methods for TEM
Authors: Chien K. , Gonzalez R. , Heusser R. C. , Shiroishi H. , Heathershaw M. L. 
Published: June 2020

Multiple sectioning: Two or more core specimens from a kidney needle biopsy can be embedded in single block using an 8-facet silicone rubber embedding mold. Tissue blocks are softened by placing them face down on an 85°C hot plate for one minute and then trimming with a Teflon coated razor blade. This prevents the block face from being deeply fractured which can affect section quality. If glomeruli are found within different cores in a single block, the block face can be retrimmed into multiple mesas and simultaneously thin-sectioned. This method greatly increases the efficiency of both thick and thin sectioning which is extremely helpful when handling more than 1600 cases of renal biopsies in our EM laboratory each year.Knife Spacer: Due to the difference in thickness between a glass and diamond knife, and also depending on which portion of the diamond knife is being used, the knife stage has to be moved laterally over a long distance when changing from one knife type to the other. Placing a L-shaped spacer, 3 to 5 mm in thickness, on the left side of the stage when sectioning a glass knife will greatly reduce this lateral adjustment.
Time-resolved high-resolution electron microscopy of structural stability in mgo clusters
Authors: Kizuka T. , Tanaka N. 
Published: June 2020

Structure and stability of atomic clusters have been studied by time-resolved high-resolution electron microscopy (TRHREM). Typical examples are observations of structural fluctuation in gold (Au) clusters supported on silicon oxide films, graphtized carbon films and magnesium oxide (MgO) films. All the observations have been performed on the clusters consisted of single metal element. Structural stability of ceramics clusters, such as metal-oxide, metal-nitride and metal-carbide clusters, has not been observed by TRHREM although the clusters show anomalous structural and functional properties concerning to solid state physics and materials science.In the present study, the behavior of ceramic, magnesium oxide (MgO) clusters is for the first time observed by TRHREM at 1/60 s time resolution and at atomic resolution down to 0.2 nm.MgO and gold were subsequently deposited on sodium chloride (001) substrates. The specimens, single crystalline MgO films on which Au particles were dispersed were separated in distilled water and observed by using a 200-kV high-resolution electron microscope (JEOL, JEM2010) equipped with a high sensitive TV camera and a video tape recorder system.
Probing vacancies and structural distortions at individual defects in ceramics using EELS
Authors: Wallis D. J. , Browning N. D. 
Published: June 2020

In electron energy loss spectroscopy (EELS), the near-edge region of a core-loss edge contains information on high-order atomic correlations. These correlations give details of the 3-D atomic structure which can be elucidated using multiple-scattering (MS) theory. MS calculations use real space clusters making them ideal for use in low-symmetry systems such as defects and interfaces. When coupled with the atomic spatial resolution capabilities of the scanning transmission electron microscope (STEM), there therefore exists the ability to obtain 3-D structural information from individual atomic scale structures. For ceramic materials where the structure-property relationships are dominated by defects and interfaces, this methodology can provide unique information on key issues such as like-ion repulsion and the presence of vacancies, impurities and structural distortion.An example of the use of MS-theory is shown in fig 1, where an experimental oxygen K-edge from SrTiO3 is compared to full MS-calculations for successive shells (a shell consists of neighboring atoms, so that 1 shell includes only nearest neighbors, 2 shells includes first and second-nearest neighbors, and so on).
The structure and properties of misfit layer compounds
Authors: Curzon A. E. 
Published: June 2020

The purpose of this article is to provide an introduction to the class of compounds known as misfit layer compounds.An example of a misfit layer compound is (NdS)1.2NbS2 In the present study this material was made by heating appropriate amounts of sulphur powder, niobium powder and neodymium chips in an evacuated quartz tube at 850°C for 12 hours. A subsequent five day process involving transport and back transport at 1000°C in the presence of iodine as transport agent led to the formation of lustrous crystal platelets suitable for electron microscopy and electron diffraction studies. The orthorhombic material consists of alternate layers of NdS (two atoms thick) and layers of NbS2 (three atoms thick) each perpendicular to the c-axis. Fig. 1 shows a [100] view of the structure observed in recent studies. Though it differs from the structure reported in other work, both reported forms have features in common which are characteristic of all misfit layer compounds.
Can The Icosahedral Phase Be Modeled as a Crystal?
Authors: Bian Weimin , Zhu Yimei 
Published: June 2020

We propose a crystal model that is in excellent agreement with the experimental electron diffraction patterns and high-resolution electron microscopy images of the icosahedral phase in Mn-Al and related systems. Structurally, the model has long-range translational order with a large unit-cell (Im3 space group) containing 10038 atoms, as well as orientational order characterized by symmetry close to the m35 point group which is commonly assigned for quasicrystals.Fig.l(a)-(c) show, respectively, the SAD patterns of the so-called twofold, threefold, and fivefold axes observed in rapid quenched Al-14at%Mn. Simulation of the corresponding SAD patterns (Fig.l(d)-(h)) suggested that they did not result from a single zone-axis diffraction, but from several closely orientated zone axes. For example, Fig.1(f) was generated by the superposition of the [305], [508], and [8 0 13],…. axes (denoted as N-<305>); the rotation angles from the [001] axis to each axis are 30.96°, 32.01°, and 31.61 °, respectively. All are very close to 31.71 °, which is the angle between a twofold and a fivefold axis in the m35 point group. In a conventional electron diffraction experiment, if the [001] axis of the crystal is rotated 31.71° around the [010] axis, these three zone axes would simultaneously satisfy the Bragg conditions and cannot be separated. Such superposition in the projected diffraction pattern, especially when the unit-cell is large, can yield a pseudo-fivefold symmetry which is indistinguishable with a true fivefold symmetry in SAD.
Skeletal-muscle ultrastructural pathology in patients with sepsis and multiple organ failure syndrome (MOFS)
Authors: Márquez A. , Diaz N.L. , Finol H.J. , Correa M.E. 
Published: June 2020

To date the most accepted definition of sepsis includes the suspicion of infection plus the systemic response to it (tachypnea, tachycardia and hypothermia or hyperthermia). This condition could lead to the so called multiple organ failure syndrome (MOFS) when there are evidences of flinctional compromise in two or more systems. Muscle weakness and wasting are common findings in those patients. The skeletal muscle histopathology in patients with those two conditions has been poorly studied. The only electron microscopic investigation we could find describes alterations in muscle fibers and endplates.In this work we describe the whole spectrum of changes found in skeletal muscle of patients suffering from sepsis and MOFS.Five patients recluded in an Intensive Care Unit were selected, two had a diagnosis of sepsis, and three presented MOFS. Needle muscle biopsies from quadriceps femoris muscle were obtained. Tissue samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.
Electron microscopy study of skeletal muscle microvasculature in the paraneoplastic phenomenon
Authors: Tonino P. , Finol H.J. , Márquez A. , Müller B. , Correa M. , Sosa L. 
Published: June 2020

In addition to signs and symptoms at sites of primary and metastatic disease, cancer can cause manifestations in remote sites that are not directly affected by any focus of disease. Such manifestations of malignancy are collectivelly known as paraneoplastic phenomenon. Muscular manifestations consist of slight to severe and usually proximal wasting and weakness. In our laboratory we described the ultrastructural pathology of skeletal muscle in the paraneoplastic phenomenon in patients with bronchogenic and cervix carcinoma. In these studies a brief report on capillary alterations was made. The present investigation was undertaken in order to extent the study on the microvasculature in the skeletal muscle paraneoplastic phenomenon.Muscle biopsies were obtained in patients suffering from bronchogenic carcinoma (n= 10), gastric carcinoma (n= 7), cervix carcinoma (n= 1) and lymphoma (n= 4). Tissue samples were processed by routine transmission electron microscope techniques and observed in a Hitachi H-500 EM.
Application of a corrected LVSEM in Biology: Artefacts in imaging of uncoated biological material
Authors: Wepf R. , Haider M. , Kroug M. , Mills D. , Zach J. 
Published: June 2020

In Biology high resolution SEM has become of special interest to study the surface representations of isolated macromolecular complexes as well as the organisation of such complexes and organelles in their natural context.Apart from the probe size, surface imaging in the nm-scale is limited by the interaction volume of the primary electrons, which directly increases with increasing primary energy. On one hand at low voltages (200-1000eV) the interaction volume can be kept minimal, but a probe size of 1-2 nm can only be obtained by a correction of the spherical and chromatic aberrations (Zach, 1990; Haider et al., 1994). On the other hand, the probe size at high voltages is mainly limited by diffraction and spherical aberation but nevertheless a probe sizes <1 nm at 30keV can be routinely achieved (Nagatani et al., 1987). To overcome the resolution limitation by the large interaction volume in bulk samples, biological specimens are coated with a very thin (1-2 nm) metal film to localize the SE-signal at the surface of the specimen (Joy, 1990).
Environmental Scanning Electron Microscope (ESEM) Observation of Subsurface Charge Effects in Insulators: Implications for Electron Imaging and X-Ray Microanalysis
Authors: Griffin B.J. , Nockolds C.E. 
Published: June 2020

The nature of subsurface charging in non-conductive samples has been investigated and modelled by a number of authors. Potential effects of subsurface charging include modification in electron range and interaction volume, variation in secondary electron yield, and reduction in incident electron beam energy and consequent modification to the emitted x-ray signal.During an unconnected experimental series on large surface area, polished mineral samples unusual images were observed following spot x-ray analysis. On these specimens, a bright circle centred on the analysis point was observed at low magnification in the secondary electron image. Around diis bright circle was a concentric dark zone with diffuse edges. This effect was noted to be time variant, with the scanned area progressively increasing in brightness until the contrast with the circle was lost. Curiously however the perimeter of the circle was defined at this stage by a narrow 'dark' ring. This serendipitous observation has led to the observation and definition of subsurface charging in insulators, albeit at a preliminary stage.
Tip-sample force interaction and surface local hardness in STM and AFM imaging
Authors: Whangbo M.-H. , Bengel H. , Magonov S. N. 
Published: June 2020

STM and AFM images of various layered inorganic compounds, organic conducting salts and polymers were examined to assess the role of the tip-sample force interaction in scanning probe microscopy. To a first approximation, the AFM image of a sample surface is described by the total electron density plot ρ(r0), and the STM image by the partial electron density plot, ρ(r0, ef). In these calculations, the structures of the surface layers are taken from the bulk crystal structures, so that a surface deformation induced by the tip force is neglected.During the scanning in STM and AFM measurements, a sample surface often undergoes a geometry relaxation due to the tip-sample force interactions. As depicted in Fig. 1a, the macroscopic deformation of a sample surface caused by the tip force is explained in terms of classical theories in which the interacting solids are treated as materials with uniform density distributions. For a surface with several different chemical environments, the extent of the surface atom depression is determined by the local hardness.
Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy
Authors: Kinney H. , Occelli M.L. , Gould S.A.C. 
Published: June 2020

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.
Novel labeling methods for em analysis of ultrathin cryosections
Authors: Robinson John M. , Takizawa Toshihiro 
Published: June 2020

Ultrathin cryosections are the most favorable material for localization of intracellular antigens with particulate probes (e.g., colloidal gold) in post-embedding immunocytochemistry. Cryosections are prepared under the most benign conditions as compared to embedding samples in various kinds of plastic media. Typically, higher labeling efficiencies can be achieved with ultrathin frozen sections than with plastic sections.We have utilized human neutrophils, the most abundant type of leukocyte, as a model system to explore labeling procedures for ultrathin cryosections. These labeling procedures can serve as alternative or complementary approaches to the traditional colloidal gold label. Neutrophils are characterized by the presence of numerous granules in their cytoplasm. For many years, the model for neutrophil structure has held that there are two granule types in these cells, the socalled azurophilic and specific granules. We have described an additional cytoplasmic compartment with unusual properties in neutrophils. This compartment is characterized by the presence of the enzyme alkaline phosphatase (Fig. 1).
An improved method for preparation and stereo imaging of negative-stained phospholipid vesicles by field-emission STEM
Authors: Apkarian Robert P. , Lee Stephen , Menger Fredric M. 
Published: June 2020

The method of application of negative stains and the subsequent chemical interaction with various types of phospholipids affect vesicle morphology. Temperature, pH, stain concentration, and the method by which the vesicle solution is applied to the grid necessitates a systematic study. We have developed a method for spray mounting and uranyl acetate (UA) staining of extruded vesicles composed of dilauroylphosphatidylcholine (DLPC, 95%) and dimyristoylphosphatidylcholine (DMPC, 5%) from which we could acquire quality stereo images with high resolution field emission STEM.The vesicles were prepared by 19 passes through a low pressure extruder containing a 0.1 μm polycarbonate membrane filter. After extrusion, 0.5 ml of vesicle solution was diluted with 3.5 ml of 0.1 μm filtered water and vortexed. The concentration of diluted phospholipid was 1.35 mM. The vesicle solution and 2 % UA stain in Milli-Q purified deionized water were mixed at room temperature 1:1 v/v. The UA solution was first prepared at 2X the desired concentration (4%) and sonicated into aqueous solution for at least 15 min. Before mixing with the vesicle solution, the UA was diluted to the desired 2% concentration and run through a 0.1 ¼m filter.
Low-temperature low-voltage scanning electron microscopy (LTL VSEM) of uncoated frozen biological materials: A simple alternative
Authors: Ahlstrand G. G. 
Published: June 2020

Introduction.Scanning Electron Microscopy (SEM) of biological materials, e.g. plants, fungi, insects, bacteria, host-pathogen interactions, and food systems, requires sample stabilization. Conventional strategies of chemical fixation (e.g. buffered glutaraldehyde, paraformaldehyde, osmium tetroxide), dehydration (ethanol or acetone series), critical point drying (CPD) and metal coating (Au/Pd) in a sputter coater or vacuum evaporator are often by applied. However, delicate biological materials may not withstand the stress of conventional preparation and acquire artifact such as collapse or shrinkage of cells or loss of soluble components (Fig la). Sophisticated devices and techniques are available which quick-freeze (<1.0 s), metal coat and transfer specimens under vacuum into the SEM. Herein I describe a simple, inexpensive alternative in which fresh biologicals are frozen slowly (< 1.5 min.) on an SEM cold stage, imaged directly without metal coating (Fig lb) at low SEM acceleration voltage (kV), and defrosted if needed with nitrogen gas (N2).