bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scanning electron microscopy studies on the morphology and release of vesicular stomatitis virus
Authors: Moninger Thomas , Rodriguez Jose 
Published: June 2020

In spite of convincing evidence to the contrary, the overwhelming majority of virologists still refer to vesicular stomatitis virus (VSV) as “bullet-shaped”. The term bacilliform, which refers to a cylinder with 2 rounded ends, is used infrequently and conditionally to describe VSV.We have used scanning electron microscopy (SEM) to study the morphology of the Indiana strain of VSV attached to, being, or having been released from 3 types of cultured cells, namely, a human melanoma line known as MEWO, human foreskin cells, and primary cultures of chick embryo cells. We have used crude virus suspensions and virus concentrated ten-fold by highspeed centrifugation and resuspension, as well as fresh virus preparations and virus suspensions that have been kept frozen at -70°C and thawed before use.Virus suspended in medium containing 10% fetal bovine serum was used for transmission electron microscopy (TEM). The suspension were negative stained with 1% phosphotungstic acid containing 0.1% bacitracin and viewed in an Hitachi H-7000 TEM. For scanning electron microscopy, virus was adsorbed for 1.5 hours at 37°C unto confluent layers of cells grown in 35 mm plastic petri dishes.
Fractal geometry and its uses for characterizing microstructure
Authors: Russ John C. 
Published: June 2020

Observers of nature at scales from microscopic to global have long recognized that few structures are actually described by Euclidean geometry. Mountains are not cones, clouds are not ellipsoids, and surfaces are not planes. Classical geometry allows dimensions of 0 (point), 1 (line), 2 (surface), and 3 (volume). The advent of a new geometry that allows for fractional dimensions between these integer topological values has stirred much interest because it seems to provide a tool for describing many natural objects. As is the case for many new tools, this fractal geometry is subject to some overuse and abuse.A classic illustration of fractal dimension concerns the length of a boundary line, such as the coast of Britain. Measuring maps with different scales, or striding along the coastline with various measuring rods, produces a result that depends on the resolution. More than this is required for the coastline to be fractal, however: It must also be self-similar.
Quantitative measure of mixture homogeneity of an alumina silicon carbide composite
Authors: Kelly James F. , Fuller Edwin R. 
Published: June 2020

Homogeneity, defined in terms of spatial distribution uniformity of one phase or component within another, can be determined from the variation of the standard deviation of the measured volume fraction of one component with sampling area. We have applied this concept to the evaluation of dispersions of Sic whiskers in an alumina matrix by using energy dispersive x-ray spectroscopy (EDS) . The quantitative analysis measures the area to area variation in SiC fraction. The homogeneity distribution was obtained by calculating the variance in this fraction as a function of magnification (sampling area) in a scanning electron microscope. These data are compared to calculations of expected values based on a Poisson distribution model for the dispersion of SiC.Compositions were prepared from two different SiC size distributions. The blending procedures and volume fractions (0.30) were the same for each composition. Six polished specimens were analyzed from each of two 100mm diameter hot-pressed alumina - SiC billets.
Cryopreservation of biological specimens
Authors: Joseph Costello M. 
Published: June 2020

Rapid cooling is the first, critical step in the preservation of biological specimens for examination using a wide variety of electron microscopic techniques. The choice of which cooling method to use depends on many factors, such as the restrictions of specimen geometry, the type of structural information desired and the microscopic techniques to be employed. This summary will highlight some recent technical innovations and novel applications of cryopreservation of biological specimens to study ultrastructure, chemical composition, and dynamic processes.For cryofixation to give realistic preservation of structural details, the specimen must be rapidly brought into intimate contact with the coolant and the contact must be maintained throughout the critical stages of the cooling process. During the last decade, four cooling methods have become prominent because they produce excellent preservation without cryoprotectants, are commercially available and are relatively simple to use:plunge cooling, jet cooling, slam cooling, and high-pressure cooling.Plunge cooling, the most commonly used method for cryofixation, is simply the immersion of a specimen into a liquid coolant usually held near its melting point.
Atomic-force microscopy: Exotic invention or practical tool?
Authors: Chernoff Donald A. 
Published: June 2020

The Scanning Tunneling and Atomic Force Microscopes are well-known due to their extraordinary capability of imaging atoms using a simple mechanism. However, atomic resolution is usually not needed to solve most problems in development and manufacturing. So, many scientists and engineers (mistakenly) regard these new microscopes as more “exotic” than practical.Both the AFM and the STM make 3-dimensional images of solid surfaces, but the AFM has much broader applications. The reason for this is that the AFM uses a universal sensing mechanism (repulsive and attractive mechanical forces), whereas the STM uses an electrical signal, which requires that the surface be at least somewhat conductive.
Using the extraordinary height sensitivity and wide scan capability of the AFM, we easily answer simple (but important) questions about surfaces and surface features, including:
-Is a contaminant present?-Is a feature a pit or a peak?-How tall is it?-What is the grain size of a coating?-How rough is the surface?
Software for the reconstruction of off-axis electron holograms
Authors: Joy David C , Bunn Rodney D 
Published: June 2020

Holography is a two step imaging process. After a hologram has been recorded it must then be reconstructed in order to obtain the stored image information. Gabor originally envisaged the use of optical reconstruction methods, but these are difficult to set up and limited in their flexibility. The alternative is to use digital techniques to reconstruct and manipulate the hologram and its reconstructions. This paper describes a program designed for the reconstruction of off-axis electron holograms.An off-axis electron hologram is an interferogram between a reference electron wave and the signal wave which has passed through the specimen. The hologram consists of a pattern of fringes modulated in position and amplitude as a result of phase shifts in, and scattering of, the signal wave. To recover phase and amplitude images from the hologram it is necessary to perform three operational steps. Firstly, the digitized hologram is Fourier transformed producing an array of complex numbers, one for each pixel in the original hologram.
Atomic resolution characterisation of interface structures by Electron Energy Loss Spectroscopy
Authors: Browning N. D. , McGibbon M. M. , Chisholm M. F. , Pennycook S. J. 
Published: June 2020

The recent development of the Z-contrast imaging technique for the VG HB501 UX dedicated STEM, has added a high-resolution imaging facility to a microscope used mainly for microanalysis. This imaging technique not only provides a high-resolution reference image, but as it can be performed simultaneously with electron energy loss spectroscopy (EELS), can be used to position the electron probe at the atomic scale. The spatial resolution of both the image and the energy loss spectrum can be identical, and in principle limited only by the 2.2 Å probe size of the microscope. There now exists, therefore, the possibility to perform chemical analysis of materials on the scale of single atomic columns or planes.In order to achieve atomic resolution energy loss spectroscopy, the range over which a fast electron can cause a particular excitation event, must be less than the interatomic spacing. This range is described classically by the impact parameter, b, which ranges from ~10 Å for the low loss region of the spectrum to <1Å for the core losses.
Hole count and secondary excitation in several analytical electron microscopes
Authors: Kenik E.A. , Allard L.F. , Bentley J. 
Published: June 2020

Hole count and secondary excitation are two concerns the analyst must address for energy dispersive X-ray spectrometry (EDXS) in the analytical electron microscope (AEM). Identification and minimization of the uncollimated radiation responsible for the hole count should be as important to the AEM manufacturer as it is to the microscopist, especially as "good" hole count performance can be a sales advantage. Secondary excitation (which we previously referred to as secondary fluorescence) arises from excitation of the specimen by electrons or high energy x-rays generated by the interaction of the primary electron beam with the specimen. A test specimen (modified chromium thin film/molybdenum washer) described previously, has been used to evaluate levels of both hole count and secondary excitation in a number of AEMs.Hole count spectra from the test specimen have been measured for several Philips AEMs and have been compared to those produced by direct excitation of a thick region of the molybdenum support by the high energy electrons at reduced beam current.
Characterization of ultrafine copper oxide aerosols for animal exposure studies
Authors: Godleski John J. , Krishna Murthy G.G. , Skornick William , Hatch Victoria , Stearns Rebecca , Katler Marshall 
Published: June 2020

People are exposed to complex mixtures of air pollutants in the urban environment. The inhalation of acid-coated metal oxide fine particles is a well-recognized health effects problem, but the mechanisms of toxicity remain undefined. Ultrafine particles (<100 nm in diameter) are difficult to detect by conventional air sampling methodology. In order to characterize such particles, electron microscopy techniques are needed. In this abstract, we outline techniques to produce, characterize, and expose animals to ultrafine (1-30 nm) copper oxide aerosols.The ultrafine copper oxide aerosols were generated using a high temperature tube furnace with molybdenum windings (0.93 m long), capable of operating at 1923° K. The temperature at the center of the furnace was maintained at 1709° K during the experiments. Copper metal shot of 99.99+ purity (Aldrich Chemical Co. Inc.) and 2-8 mm in size was used as the copper source. An alumina boat (30 x 8 x 3 mm) containing 2 g copper was placed at 0.187 m from the center of the furnace where the measured temperature was 1683° K. The copper vapors from the boat were carried by a pure argon stream and were oxidized by added oxygen.
Characterization of epitaxial diamond on natural diamond substrates by cathodoluminescence
Authors: Malta D.P. , Fitzgerald E.A. , Posthill J.B. , Rudder R.A. , Hudson G.C. , Markunas R.J. 
Published: June 2020

A large effort continues in the development of diamond growth technologies for the production of electronic-grade diamond epitaxy. Diamond has several properties such as a wide band gap (5.48 eV) and high thermal conductivity (2000 W m-1K-1) that make it desirable for electronic applications. Characterization of diamond with cathodoluminescence (CL) spectroscopy yields information on impurity and defect distributions with both spatial and energy resolution, providing insight into the growth process.Diamond films were grown by plasma-enhanced chemical vapor deposition (PECVD) on natural type Ia 1mm × 1mm × 0.25mm diamond substrates. The results of microstructural studies on this type substrate are discussed elsewhere in these proceedings. Two films were selected for CL analysis based on their strikingly different surface morphologies but similar growth conditions. Both were grown for 6 hours at a substrate temperature of ∽	750°C and a pressure of 5 Torr. The gas mixtures were varied: CO/CH4/H2 was used in one case and CH4/H2 in the other.
An electron microscopy study of high-thermal-conductivity ribbon-shape carbon fibers
Authors: Robinson Kerry E. 
Published: June 2020

In an effort to develop a low-cost high thermal conductivity carbon fiber, ribbon-shaped fibers were meltspun from a liquid crystalline, mesophase pitch precursor. Initial tests indicated that the ribbon-shaped fibers could be processed more easily and exhibited improved thermal conductivities when compared to commercial round fibers. Evidently, it is the more linear, polycrystalline structure within these fibers that accounts for their improved thermal conductivities. Thus, studies using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were conducted to fully analyze the transverse and longitudinal structure of these high thermal conductivity fibers.Ribbon-shaped fibers, melt-spun from a synthetic mesophase pitch and then heat treated, were tested to determine their tensile strengths, tensile moduli and thermal conductivities. A Jeol JSM-I C848 SEM at an accelerating voltage of 20 kV was used to obtain general structural information, such as extent and texture of lamellar organization of the graphitic layers within the fibers, and the microstructure of the fibers was studied by TEM.
An inexpensive, easy to use video imaging system for intracellular Ca2+ and quantitative fluorescence microscopy
Authors: Gruenstein Eric , Luna Jesus 
Published: June 2020

Fura-2 is the most commonly used member of a family of calcium sensitive flourescent dyes that allows the measurement of intracellular free calcium (Cai by dual excitation fluorimetry. The use of this dye in conjunction with video imaging microscopy permits visualization of changes in Cai with a high degree of spatial resolution. This resolution in turn allows the detection of Cai gradients, waves, and other localized cellular responses not easily detected by photometric techniques. Despite these advantages, most published reports have utilized photometry rather than imaging, due largely to the higher cost and greater complexity of use of the latter technique. With these problems in mind, we have developed a turnkey calcium imaging system that is both inexpensive and simple enough to use that it can be mastered in 2-3 hours.Data showing the distribution of free Ca2+ in the cytoplasm of a quiescent human fibroblast and the kinetics of stimulation of these cells with mitogens are illustrated on the next page.
Electron beam damage of Ni3Al
Authors: Muller David A. , Silcox John 
Published: June 2020

In recent years, the effect of radiation induced sputtering in electron microscopy at voltages as low as 100 kV has been identified and has emerged as a significant factor in microanalysis. The inhibiting effect of some surface layers has also been noted. More generally, the use of focused electron probes (as in STEM) as a tool for materials modification on the nanoscale has also been developed. We report here observations of electron radiation effects in Ni3Al, a proto-typical high temperature, high strength intermetallic of some considerable interest. This work is comparable to the study of electron radiation damage in aluminium reported by Bullough et.al.Fig. 1 illustrates the formation of holes in a Ni3Al specimen and the associated nickel rich patches formed after irradiation at 100kV in the Cornell UHV HB501A STEM in spot mode with an estimated 10Å FWHM beam size at a beam current of 0.12 nA for a period of 20 minutes. The somewhat dramatic radiation damage is readily seen.
A field-emission SEM optimized for operation at low beam voltage
Authors: Pawley JB , Ximen J , Lin PS-D , Schippert M. 
Published: June 2020

The advantages of operating the SEM at low beam voltage (V0 ) have been recognized for some time. They include: less specimen charging, greater contrast in the fine topographic component of the secondary electron (SE) signal and reduced radiation damage. Although initially it was difficult to obtain high resolution images when using low V0, this limitation can be essentially overcome by employing both a FE source and an immersion objective lens. In an instrument employing both of these features it is possible to produce a beam diameter of about 3 nm @ 1.5 kV. When insulating specimens are viewed under these conditions, the resolution in the image is limited more by the structure of the coating material than by the beam diameter, while on conductors, small structural features produce useful contrast only at low V0.The remaining obstacle to more widespread use of LVSEM for high resolution topographic imaging is the high cost of the equipment.
Applications of virtual objective aperture in TEM
Authors: Fan G.Y. , Deerinck T. , Ahn C.C. , Price J. , Young S.J. , Ellisman M.H. 
Published: June 2020

In a special imaging mode (B mode) available on a customized JEM-4000EX microscope, the objective mini lens (OM) is strongly excited so that the back focal plane of the objective lens (OL) is imaged onto the plane of the selected-area aperture (SA), Fig. 1, with a magnification of 3.2x. Thus the S A functions as a virtual objective aperture, the applications of which are summarized below.1. Improving contrast in imaging thick sections of biological specimens.The increased inelastic scattering in thick specimens results in image blur due to chromatic aberration present in the magnetic lenses. Such blur degrades image resolution and contrast. The energy loss spectrum in Fig. 2 (curve 1), from a 1 μm section of frog spinal ganglion, suggests that the inelastic contribution to images of this type of specimen is substantial. The use of an objective aperture (OA) can reduce some of the unwanted contributions (curve 2), but the SA in B mode is much more effective, as suggested by Fig. 1 and demonstrated by curved 3.
Second-generation scanning photoemission microscope at the National Synchrotron Light Source
Authors: Ko Cheng-Hao , Kirz Janos , Ade Harald , Johnson Erik , Hulbert Steven , Anderson Erik , Kern Dieter 
Published: June 2020

We are commissioning a new generation scanning photoemission microscope (X1-SPEM II) at beamline X1A of the National Synchrotron Light Source (NSLS). Our first generation scanning photoemission microscope (X1-SPEM I) was the first to achieve submicron resolution. One of the major improvements is the replacement of the home-made single pass cylindrical mirror analyzer with a high energy resolution, multi-channel Hemispherical Sector Analyzer (HSA). The alignment scheme for the optical elements has also been redesigned. The advantages of these two major improvements will be discussed.A photoemission microscope requires a high brightness source and a good focusing scheme. In most cases, a monochromator is placed between the photon source and the focusing optical elements. Our X1-SPEM uses the soft x-ray undulator at the NSLS as a high brightness source. A Fresnel zone plate is coherently illuminated by the monochromatic beam selected by the spherical grating monochromator (250-800 eV range) to form a microprobe, less then 0.2 μm in size.
3D microanalysis of tissue volumes using dual-energy conebeam x-ray microtomography
Authors: Johnson Roger H. 
Published: June 2020

Using a modified SEM as a microfocus x-ray source and stimulable phosphor plates as detectors, we have built a conebeam microtomograph for 3D imaging of 1-10mm biological samples (Figure l). For individual projections, the resolution and exposure time are about three microns and two minutes, respectively, with the same parameters in the reconstruction depending on the number of views.In conventional computed tomography (CT) each detector element integrates the energy incident upon it from all transmitted photons regardless of their wavelength. All spectral information is lost. It can be beneficial to acquire two sets of projections: one using a higher peak x-ray source energy than the other. Figure 2 illustrates that tissue and bone will attenuate the two spectra differentially producing different contrast relationships in the high- and low-energy images. We have previously clinically applied post-processing dual-energy CT to analyze the mineral and fat content of lumbar vertebrae in perimenopausal, osteoporotic women.
Improvements in electron diffraction of frozen hydrated crystals by energy filtering and large-area single-electron detection
Authors: Schröder Rasmus R. , Burmester Christoph 
Published: June 2020

Diffraction patterns of 3D protein crystals embedded in vitrious ice are critical to record. Inelastically scattered electrons almost completely superimpose the diffraction pattern of crystals if the thickness of the crystal is higher than the mean free path of electrons in the specimen. Figure 1 shows such an example of an unfiltered electron diffraction pattern from a frozen hydrated 3D catalase crystal. However, for thin 2D crystals electron diffraction has been the state of the art method to determine the Fourier amplitudes for reconstructions to atomic level, and in one case the possibility of obtaining Fourier phases from diffraction patterns has been studied. One of the main problems could be the background in the diffraction pattern due to inelastic scattering and the recording characteristics for electrons of conventional negative material.It was pointed out before, that the use of an energy filtered TEM (EFTEM) and of the Image Plate as a large area electron detector gives considerable improvement for detection of diffraction patterns.
Chemically assisted ion-beam etching in a low-angle ion mill
Authors: Alani R. , Swann P.R. 
Published: June 2020

In conventional ion mills, chemically assisted ion beam etching (CAIBE) has become an establish method for TEM specimen preparation of certain materials. CAIBE employs a reactive gas which brought in contact with the specimen through a jet assembly, while an inert gas ion beam is directed on the same area. Therefore, thinning occurs by the combination of chemical reaction and physic sputtering, which leads to enhanced thinning rates. The reactive gas used in the CAIBE technique can generated from a solid source which sublimes e.g. iodine or it can be injected directly from a pressuriz gas bottle e.g. nitrous oxide. Nitrous oxide in combination with a xenon ion beam has been used from cross sectioning TEM specimens of diamond films on silicon.It is well known that indium-containing compound semiconductors develop indium islands on the surface when thinned with an argon ion beam. It is believed that preferential sputtering enriches the surface with indium and that heating by the ion beam melts the indium which then agglomerates to for small globules on the surface.
Transmission electron microscopy studies of boron nitride thin films produced by pulsed laser deposition
Authors: Medlin D.L. , Friedmann T.A. , Mirkarimi P. B. , McCarty K.F. , Mills M.J. 
Published: June 2020

We are synthesizing boron nitride films by pulsed laser ablation in order to study the deposition conditions necessary to produce the cubic phase (cBN) which has a number of useful applications as a hard coating, semiconductor, and optical material. The yield of cubic material is controlled in part by the simultaneous irradiation of the growing film with a low energy beam of N2 and Arions. In order to understand how this transformation process occurs, we are using TEM to investigate how the microstructure and phase distribution varies with film deposition conditions.In many ways analogous to carbon, boron nitride forms both sp3- and sp2-bonded phases. The cubic phase (cBN), which is sp3 bonded, has the zinc blende structure, and in addition, BN can also form an sp3 bonded hexagonal phase with the wurtzite structure (wBN). An sp2-bonded hexagonal structure (hBN) is the stable room temperature phase, but like its analog, graphite, the sp2-bonded material can also exist in a highly disordered state, often referred to as turbostratic (tBN).