bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Resolution sem and Clostridial Attachment
Authors: Panessa-Warren B. , Tortora G.T. , Warren J. 
Published: June 2020

Since the mid 1960’s when the TEM was a new and primary tool for elucidating the classification of the various strains of microorganisms, investigators around the world have been reporting morphological surface aberrations (such as hairs, ribbons, tubular appendages and feather-like structures) of the clostridial endospore that facilitate and verify the classification of these organisms. Yolton Pope, Samsonoff and others were unable to discern the function, of these appendages and stated that the “functional role of spore appendages remains obscure”.Today, there is still no information on the functional role, if any, of these “appendages” and “hairs”. For the past few years we have been examining the endospores from two clostridial species that are pathogenic in man and higher mammals,C.sporogenesATCC3584, andC.difficileATCC 9689and43594. These organisms cause wound infections, pseudomembranous colitis, and nosocomial diarrhea. Our previous work strongly suggested that the outer envelope of these spores, the exosporium, had a “morphological plasticity” that allowed the spores to attach to a surface that supported bacterial growth5,6. With current advances in high resolution SEM using LaB6 and field emission sources, it is now possible to study these extremely small and complex spore appendages at all stages of germination with spacial orientation capabilities not possible when the original studies were done. Over the past 2 yrs, the advances in software technology and improved SEM resolution and image enhancement capabilities, make it possible to work with fields of intact spores still attached to a nutritive surface and examine the exosporium and membrane contacts with the nutrient surface at resolution and magnifications formerly reserved for TEM. This investigation combines attachment studies using agar substrates (Trypticase Soy agar + 5% glucose, and Blood CDC agar) and human cells (lung fibroblasts and colon cells), with high resolution imaging of intact spores on their nutritive substrate (agar and human cell)to determine the ultrastructural changes that accomplish clostridial colonization. Studies were also done to determine if attachment was altered as a result of exposure to cation substitution, cation chelation, or colchicine treatment.
A survey of detector options for the “leaky-vacuum” SEM
Authors: McKernan Stuart , Mansfield John F. 
Published: June 2020

Since the inception of the “Leaky-Vacuum” SEM (known by various manufacturers as environmental-, wet-, variable-pressure-, high-pressure- SEM) samples may be imaged with environmental conditions which are radically different from those in traditional SEMs. The presence of a (relatively) high pressure in the sample chamber affects the ability of the microscope to form a small, well defined electron probe on the surface of the sample, thereby affecting the ultimate resolution of the microscope. The environment also affect the operation of most SEM detectors. In this contribution the operation of different SEM detectors will be surveyed, and their performance in the "Leaky-Vacuum" SEM environment will be examined.The most common detector in the SEM, the Everhart-Thornley (E-T) secondary electron (SE) detector, suffers most strongly from the effect of the residual chamber gas at high pressures. SEs emitted from the sample are low in energy and frequently collide with the residual chamber gas. This causes an electron cascade which ultimately overloads the E-T detector.
Environmental microscopy of capillary stress-induced strain behavior in ambient-pressure aerogels
Authors: Rao Sudeep M. , Samuel Joshua , Prakash Sai S. , Brinker C. Jeffrey 
Published: June 2020

Ambient pressure silica aerogel thin films have recently been prepared by exploiting reversible drying shrinkage caused by derivatization of the internal gel surface. Aerogels have porosities of upto 99.9% and due to the small size of the pores (few nanometers), large capillary stresses are produced in gels that are partially saturated with a wetting liquid. As a result of these capillary stresses, the flexible silica network undergoes strain which has been observed using environmental microscopy. This technique allows variation of the equilibrium vapor pressure and temperature, and a simultaneous monitoring of the deformation of the unconstrained film thickness. We have observed >600% deformation during the pore-filling and pore-emptying cycles. In this presentation, we discuss the unique stress-strain behavior of these films.Ref.: Sai S. Prakash, C. Jeffrey Brinker, Alan J. Hurd & Sudeep M. Rao, "Silica aerogel films prepared at ambient pressure by using surface derivatization to induce reversible drying shrinkage", Nature. Vol. 374, 30 March, 1995, 439-443.
Atomic force microscopy studies of microstructure and properties of self-assembled monolayers
Authors: Richards J. F. , Troughton E. B. , Dennis R. A. , Russell P. E. 
Published: June 2020

Self-assembled monolayers are unique structures and have received considerable attention from microscopists seeking to image the predicted molecular level structure. More recently, practical engineering applications of SAMs have been proposed in areas ranging from corrosion barriers to adhesion promoters to lithographic resists. While some of the applications of interest, most notably the lithographic resists, can be developed on substrates close to the ideal; such as single crystal Si wafers or thin epitaxial films; many others will require the coating of very non-ideal surfaces. These may range from materials such as Al or ferrous based metals to engineering polymeric materials. In this study we have taken a two-pronged approach to develop reliable systematic atomic force microscopy (AFM) techniques for the determination of both microstructure and properties of SAMs on various substrates of interest.We have chosen to investigate n-alkanethiols (SH-(CH2)n-1-CH3) on single crystal gold as our reference system for technique development.
Quantitative Scanned Probe Microscopy
Authors: Russ J.C. , Scott P. J. 
Published: June 2020

The great advantage of the atomic force microscope and related technologies (tunneling current, near field optical, tips that oscillate vertically or laterally, etc.) has been simplicity of design. Vertical deflection of a reference tip on a cantilevered probe is detected by light scattering and used to shift the sample in the z direction to restore tip position. The output is generally in the form of surface images rather than measurements with high dimensional accuracy. Atomic scale resolution is achievable but lower magnification imaging is more difficult.Piezo devices used for x-y and z axis control have a limited range of motion and are noisy, nonlinear and subject to creep. Piezo displacement is not simply a function of voltage, or of the time integral of current, but depends upon many factors including rate and distance of motion, and internal resistance and capacitance in the device. It is possible in principle to calibrate such a system using a reference grid standard, but even this is highly dependent on scanning speed (different in the x, y, z directions) and will not provide quantitative z information.
Scanning probe microscopy of polymers in the field emission SEM
Authors: Brostin J. 
Published: June 2020

The field emission SEM (FESEM) is well suited for imaging polymer and other non-conductive surfaces. High resolution SEM images can be obtained without the application of a conductive coating when operated at low accelerating voltages. Compositional imaging in the backscattered electron mode is facilitated at low voltages by the incorporation of a microchannel plate (MCP) detector. The MCP equipped FESEM has been shown to be phenomenally sensitive to very small differences in average atomic number. Compositional contrasts are achieved in polymer and other low-Z composites that differ only in oxygen content. Those systems that completely lack intrinsic contrast can be differentially stained with ruthenium tetroxide vapors.These capabilities make the FESEM an ideal platform for locating phases and/or subtle features for scanning probe microscopy (SPM). Transparent, thin coatings or very fine, heterogeneously dispersed structures that cannot be readily located or observed with conventional light optics can generally be seen in the FESEM.
Rapid microwave processing of skeletal muscle for TEM
Authors: Smith S.A. , Martella A. 
Published: June 2020

Rapid tissue processing for transmission electron microscopy is a desired goal in a clinical EM laboratory. Reducing the time from tissue submission to examination in the electron microscope shortens turnaround time for diagnosis. Microwave enhanced tissue processing will accomplish these goals.Microwave technology reduces the time for tissue fixation and processing and may improve overall results. Fixation times can be reduced from minutes to seconds and resin polymerization from hours to minutes. Dehydration and infiltration steps can also be reduced, so that microwave rapid tissue processing can yield ultrathin sections from unfixed tissue in three hours.Three microwave protocols to process skeletal muscle biopsies are compared to standard processing. The protocols test the efficacy of microwave fixation, dehydration, and resin infiltration and polymerization. Protocol #1 uses microwave enhanced 4:1 formaldehyde/glutaraldehyde primary fixation followed by routine processing for remaining steps. Protocol #2 uses microwave primary fixation and 2% OsO4 post-fixation followed by routine processing. Protocol #3 uses microwave enhanced processing for entire procedure. Protocol #4 uses the standard processing technique.
Cosmetology treatments on human hair: An SEM study
Authors: Bowling D.F. 
Published: June 2020

High school cosmetology students study the methods and effects of various human hair treatments, including permanents, straightening, conditioning, coloring and cutting. Although they are provided with textbook examples of overtreatment and numerous hair disorders and diseases, a view of an individual hair at the high resolution offered by an SEM provides convincing evidence of the hair‘s altered structure. Magnifications up to 2000X provide dramatic differences in perspective. A good quality classroom optical microscope can be very informative at lower resolutions.Students in a cosmetology class are initially split into two groups. One group is taught basic controls on the SEM (focus, magnification, brightness, contrast, specimen X, Y, and Z axis movements). A healthy, untreated piece of hair is initially examined on the SEM The second group cements a piece of their own hair on a stub. The samples are dryed quickly using heat or vacuum while the groups trade places and activities.
Electron microscopy investigation of Si and Mo field emitters coated with diamond powder by dielectrophoresis
Authors: Myers A. F. , Choi W. B. , Cuomo J. J. , Hren J. J. 
Published: June 2020

Silicon and molybdenum are commonly used to fabricate field emission devices, which have promisingapplications in the flat panel display and vacuum microelectronics industries. However, uncoated Si and Mo field emitters usually exhibit oscillating currents during extended operation due to surface contaminant adsorption and desorption. Coating these cathodes with diamond by microwave plasma chemicalvapor deposition (MPCVD) has been shown to considerably improve the total electron emission current as well as to enhance the emission current stability. A very simple, inexpensive technique for depositing high pressure, high temperature (HPHT) synthetic diamond powder on Si and Mo emitters was recently developed and also shows greatly enhanced current-voltage characteristics. Since field electron emission from a cathode strongly depends on the emitter morphology, the diamond coating morphology and the diamond/Si and diamond/Mo interface microstructures were analyzed by electron microscopy.Single-crystal <111>-oriented Si emitters 100-300μm in height were grown by aSi-Aueutectic vaporliquid- solid technique, then chemically sharpened to form tips with a radius of curvature ≤ 30nm.
Partitioning behavior of alloying elements in PWA 1484
Authors: Miller M. K. , Lin L. S. , Cetel A. D. , Harada H. , Murakami H. 
Published: June 2020

In order to achieve a desired set of properties, such as high creep strength and oxidation resistance, a variety of alloying elements are typically added to commercial nickel-based superalloys. Since single crystal superalloys do not require the inclusion of alloying elements to improve the grain boundary properties, there is significant scope in optimizing the composition and heat treatment of these alloys. The effectiveness of these alloying elements depends on their level and location in the different phases present in the microstructure. Therefore, it is desirable to be able to accurately measure and theoretically predict their distribution within the microstructure.The partitioning behavior of the alloying elements in nickel-based superalloy PWA 1484 has been determined with the atom probe field ion microscope. These results have been compared with predictions generated from the “Alloy Design Program”. This computer program is based on regression analysis.
TEM studies of solid-state reactions in sputter-deposited Nb/Al multilayer thin films
Authors: Ma F. , Vivekanand S. , Barmak K. , Michaelsen C. 
Published: June 2020

Solid state reactions in sputter-deposited Nb/Al multilayer thin films have been studied by transmission and analytical electron microscopy (TEM/AEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The Nb/Al multilayer thin films for TEM studies were sputter-deposited on (1102)sapphire substrates. The periodicity of the films is in the range 10-500 nm. The overall composition of the films are 1/3, 2/1, and 3/1 Nb/Al, corresponding to the stoichiometric composition of the three intermetallic phases in this system.Figure 1 is a TEM micrograph of an as-deposited film with periodicity A = dA1 + dNb = 72 nm, where d's are layer thicknesses. The polycrystalline nature of the Al and Nb layers with their columnar grain structure is evident in the figure. Both Nb and Al layers exhibit crystallographic texture, with the electron diffraction pattern for this film showing stronger diffraction spots in the direction normal to the multilayer. The X-ray diffraction patterns of all films are dominated by the Al(l 11) and Nb(l 10) peaks and show a merging of these two peaks with decreasing periodicity.
Enhanced control of electropolishing for the preparation of thin foils for TEM: Artificial and multiple - phase micro-electropolishing
Authors: Lee Peter J. 
Published: June 2020

By rapidly changing voltage and current settings during electropolishing conditions can be set up for polishing otherwise difficult to polish multi-phase material. In addition a wider a more flexible range of polishing conditions can be obtained by manipulating the film build-up condition in micro-electropolishing that is normally outside the useful range of electropolishing.Electropolishing may be broken down into two distinct processes: Macro-electropolishing or “smoothing” whereby large scale asperities are removed and Mcro-electropolishing or “brightening” in which smaller (<lμm) irregularities are removed. In “bath” (immersion) electropolishing both processes take place whereas in “jet” electropolishing the polishing mechanism is primarily micro-electropolishing. For micro-polishing to occur a thin solid film must be produced at the specimen surface. In order for micro-electropolishing (sometimes called brightening or brilliance) there must be random removal of metal from the surface irrespective of features such as grain-boundaries, grain orientation and defects.
Sputter etching for microstructure evaluation of small-diameter corrosion-resistant MP35N alloy wire
Authors: Hanke L. D. , Schenk K. 
Published: June 2020

Metal alloy microstructures are characteristic of the material’s mechanical and physical properties, including the key properties of strength and corrosion resistance. Microstructural evaluations typically use chemical etching to reveal the material’s structure. For corrosion-resistant alloys, chemical etching can be difficult due to the inherent chemical resistance of the material. This is especially true for active-passive alloys, where the etching reaction is highly dependent on the final polishing and even the time delay between polishing and etching.Chemical etching is further complicated for extremely fine microstructures and when two or more metals are joined in the sample. These factors are concerns for fine wires, such as those used in implantable medical devices. A common alloy for wires in many medical applications is a Co-Ni-Cr-Mo alloy, designated as MP35N. Wires with extremely small diameters are produced by severe drawing processes that result in very fine microstructures. The alloy is often used in composite wire products, such as an MP35N outer sheath containing a silver core.
Molecule-specific imaging of biomaterials
Authors: Winograd N. 
Published: June 2020

The development of focused ion beams and time-of-flight SMS have opened new possibilities for characterization of biomaterials. For some cases, laser postionization is important for further increasing the sensitivity of the analysis. Our group has been involved in finding methodologies and applications which could add to the repetoire of imaging methods available to biologists. Presently, these methods include fluorescence microscopy, confocal microscopy, scanning probe microscopies and autoradiography, to name just a few.Sample preparation is a major issue for these materials. To achieve meaningful data it is essential to prepare an uncontaminated surface in vacuum that retains the original spatial composition of the target molecules. Although many elegant sample preparation methods have been developed in the electron microscopy community, the rules of the game for TOFSIMS imaging are quite different since we are after chemical information rather than morphological information. To solve this problem we have developed several cryogenic sample handling techniques whereby a biomaterial (e.g. a single cell) is rapidly frozen in the laboratory.
Granular cells: A new indicator of neuronal cell death in the spinal ganglia of the rat
Authors: Imel Kevin M. , Bailey J. Franklin , DeSantis Mark 
Published: June 2020

Damage to axons in the neonatal mammal results in the death of the affected neurons rather than survival and axonal regeneration as generally seen in the adult. This phenomenon has been well documented using indirect methods such as counting cells in histological sections of the experimentally damaged versus control tissue. Recent experiments have shown that cells with osmiophilic dense bodies, which have been termed “granules”, become apparent at the light microscopic level in ipsilateral lumbar dorsal root ganglia after destruction of the sciatic nerve on that side in neonatal rats. Within 84 - 96 hours after the lesion, the rat pups were anesthetized, perfused with 4% paraformaldehyde and the ganglia post-fixed in 1% unbuffered osmium tetroxide for at least 72 hours. Such a lengthy exposure to osmium was found to be necessary to visualize the granules.This offers the possibility of using these granules as a direct indicator of neuronal death in the lumbar dorsal root ganglia. The cells containing these granules were usually chromatolytic neuronal somata which had an eccentrically positioned nucleus (when a nucleus or nuclear remnant was still present) and peripheral aggregation of the rough endoplasmic reticulum (i.e. Nissl bodies).
Immunoelectron microscopic verification of a resident central-nervous-system macrophage in the rat that is not a pericyte, microglia, or type of mast cell
Authors: Dimlich Ruth V. W. 
Published: June 2020

One type of perivascular cell in the brains of all species so far examined has been given many different names. This has introduced a great deal of confusion into the literature. Using light microscopy this cell is autofluorescent, stains with periodic acid-Schiff (PAS), and cannot be identified by H&E that is used routinely in neuropathological analysis. Ultrastructurally this cell is on the luminal side of the basal lamina and has a non-lobulated nucleus, few mitochondria, a well defined Golgi area, and numerous lysosomes, phagosomes, and multivesicular bodies. Because of these features, the most common names for these cells have been “yellow fluorescing or Mato cells”, “perivascular or pericytal microglia”, “globular or phagocytosing pericytes” and “type II brain mast cell or neurolipomastocytes”.Application of a variety of histochemical techniques verified that these cells did not contain heparin or histamine, and identified for the first time that they also did not contain serotonin. Although granular and autofluorescent, the data confirmed that these cells were not mast cells. Immunohistochemically these cells also did not stain with OX42, an antibody specific for resting or activated microglia, or for actin as expected for pericytes.
X-ray microprobe for materials science
Authors: Ice G.E. 
Published: June 2020

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E≥5 keV) microprobes. With new x-ray optics these microprobes can achieve micron and submicron spatial resolutions. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature will have important applications to materials science. For example, x-ray fluorescent microanalysis of materials can reveal elemental distributions with greater sensitivity than alternative nondestructive probes. In materials, segregation and nonuniform distributions are the rule rather than the exception. Common interfaces to whichsegregation occurs are surfaces, grain and precipitate boundaries, dislocations, and surfaces formed by defects such as vacancy and interstitial configurations. In addition to chemical information, an x-ray diffraction microprobe can reveal the local structure of a material by detecting its phase, crystallographic orientation and strain.Demonstration experiments have already exploited the penetrating nature of an x-ray microprobe and its inherent elemental sensitivity to provide new information about elemental distributions in novel materials.
Spot-scan imaging of ice-embedded catalase crystal on a slow-scan CCD camera in a 400-kV electron cryomicroscope
Authors: Chiu Wah , Sherman Michael , Brink Jaap 
Published: June 2020

In protein electron crystallography, both low dose electron diffraction patterns and images are needed to provide accurate amplitudes and phases respectively for a 3-dimensional reconstruction. We have demonstrated that the Gatan 1024x1024 model 679 slow-scan CCD camera is useful to record electron diffraction intensities of glucose-embedded crotoxin complex crystal to 3 Å resolution. The quality of the electron diffraction intensities is high on the basis of the measured intensity equivalence ofthe Friedel-related reflections. Moreover, the number of patterns recorded from a single crystal can be as high as 120 under the constraints of radiation damage and electron statistics for the reflections in each pattern.A limitation of the slow-scan CCD camera for recording electron images of protein crystal arises from the relatively large pixel size, i.e. 24 μm (provided by Gatan). The modulation transfer function of our camera with a P43 scintillator has been determined for 400 keV electrons and shows an amplitude fall-off to 0.25 at 1/60 μm−1.