bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and microanalysis of laser-melted Tl high-speed tool steel
Authors: Kusinski J. , Bielicki T.A. , Thomas G. 
Published: June 2020

Laser melting (LM) is currently of interest as a means of improving the wear properties of high-speed tool steels (HSS). The rapid solidification rates obtainable after LM are expected to produce microstructural refinement and high homogeneity which are beneficial to mechanical properties. However a detailed understanding of the laser-hardening of HSS through LM of the surface remains to be obtained.This paper describes an electron-microscopic investigation of a conventionally-hardened Tl (0.85C/18.5W/4.2Cr/1.2V) HSS which was surface-melted to a depth of 300 um using 1ms pulses from a 7J neodymium laser with an incident diameter of 0.4 mm. The samples were subsequently tempered at 500°C, 600°C, and 700°C for 2 hours. The melted layer showed the highest hardness gain over the unmelted substrate after tempering at 700°C (1050 and 500 uHV respectively).
Two “improvements” for Philips 400 series microscopes
Authors: Greene A. E. , Eades J. A. 
Published: June 2020

The optimum size for the disks in a convergent-beam pattern is when the disks just touch. This provides the maximum area of useful pattern indside the disks and avoids the loss of information where they overlap. In a standard transmission microscope, the size of the disk is selected by the size of the condenser aperture. This provides only a few possible settings with rather coarse steps.We have modified Philips EM420 and EM400T microscopes to provide a continuous variation of the convergence of the incident illumination. This is accomplished by adding a control to vary the ‘Mini’ lens current. The mini lens is located inside the objective lens upper pole piece and by reversal of its magnetic flux, gives the objective lens system two distinct operating characteristics.
A simple method for performing scanned TEM on a JEOL 200CX
Authors: Colijn H. , Clark W.A.T. 
Published: June 2020

Computer analysis of TEM images and diffraction patterns has generally required the use of a video camera and frame storage. However, one can achieve the same result with a simple and inexpensive modification to the JEOL ASD system. With this modification, the ASD unit can collect TEM images and diffraction patterns rastered over the existing STEM detector. This modified ASD system can also use our existing x-ray analysis system (TN-2000) with digital beam control (DBC) to acquire images or diffraction patterns for computer analysis at a resolution of up to 512x512 pixels.Without having a video camera and frame store, one is limited to using STEM for collecting digital images. Scanned TEM allows many more options. Because the specimen is viewed in TEM mode, it is easy to adjust the camera length and magnification and to set up the desired imaging conditions. It is also significantly easier to obtain diffraction patterns using scanned TEM than using STEM methods.
A metrology electron microscope system
Authors: Hembree G. G. 
Published: June 2020

An electron microscope system has been constructed which is capable of calibration-quality dimensional measurements from 0.5 to 150 μm. This system was designed to certify one dimensional calibration artifacts for micrometrology instruments. Examples of these artifacts include stage micrometers for microscope magnification calibration and polystyrene latex for flow-through particle sizing instrumentation.The principle of operation of the instrument is similar to that of an ordinary optical measuring microscope. The electron beam is fixed in position and acts as the reference point. The measured object is translated beneath the electron beam on an electromechanically scanned stage. The displacement of the stage is determined by a commercial optical intei— ferometric measurement system. Therefore the metric of the system is directly traceable to the wavelength standard. One of the electron output signals from the specimen is stored synchronously with the data output from the interferometer by a dedicated minicomputer system. Subsequent analysis of the electron intensity profile is used to determine the measured size of the object.
Image modelling for SEM-based metrology
Authors: Joy David C. 
Published: June 2020

Much of the success of the scanning electron microscope (SEM) can be attributed to the fact that the images that it produces appear similar to those seen by our eyes. Consequently the interpretation of SEM micrographs is perceived as a straightforward process. Although this casual approach works well enough for many qualitative purposes, when the SEM is to be used to make precise dimensional measurements of micron-sized features, such as resist strips or conductor pads, then more care must be paid to the details of image formation.Two types of electron signal, backscattered (BS) and secondary (SE), are usually available in an SEM. In many respects quantitative image interpretation is more straightforward for backscattered than for secondary electrons because Monte Carlo trajectory tracing techniques can be employed to compute the expected variation of signal with beam position.
K, L, M, and N core shell ionization cross sections for ELS
Authors: Skiff W.M. , Lin S.H. , Carpenter R.W. 
Published: June 2020

Calculated core shell ionization cross sections are useful for elemental and chemical microanalysis using electron energy loss spectroscopy (ELS). We have recently derived analytical expressions for K, L, M, and N shell ionization cross sections in solids, that can be easily evaluated with a mini-computer. Here we briefly describe the theoretical model and give a preliminary comparison of the results with experiment.The ionization cross section was evaluated using the 1st Born approximation and the single-electron transition model. The initial core shell state was taken as a hydrogen-like atomic orbital with an effective nuclear charge (Z*). The final ionization state was taken as a normalized plane wave, which ignores the target potential.
Microdiffraction's Contribution to Microcharacterization
Authors: Eades J. A. 
Published: June 2020

The PresentThe most fully developed area of application of microdiffraction is the characterization of the specimen's crystal structure. Convergent-beam diffraction from a region of crystal, that has no defects (and, in the case of b, is free from strain), provides the following information:a) Unit cell. From a single short camera length pattern, it is generally possible to determine the unit cell of an unknown phase.b) Symmetry. The crystal point group and space group can be determined from a small number of patterns at major zone axes.c) Fingerprints. Standard patterns can be used to identify the same phase whenever it is subsequently observed.d) Strain. HOLZ lines can be used to measure local strain or lattice parameter variation.e) Thickness. Fringes in dark-field patterns can be used to measure crystal thickness.
Studies of silica sphere growth
Authors: Bogush G. H. , Zukoski C. F. 
Published: June 2020

Recipes are available for the preparation of monodisperse oxide powders and these materials are seeing increased use in the preparation of low flaw density ceramics. Despite the growing demand for these single sized powders, little is known about the physico-chemical processes which determine particle morphology. Here we report on studies of the mechanisms of particle growth.As a model system we choose silica spheres prepared through the hydrolysis of silica alkoxides in basic alcoholic solutions. The rates of particle growth were studied by dipping carbon sputtered formvar coated electron microscope grids into the reaction mixture at different times. The grids were immediately placed on filler paper which rapidly wicked the fluid off the grid leaving the silica particles behind.
Noise reduction in digitized images
Authors: Christenson K. K. 
Published: June 2020

In order to produce useable images at high scan rates, the detectors on modern electron microscopes often have a very high bandwidth (short response time to signal changes). This bandwidth makes the signal noisey; the signal has large fluctuations about the mean. Because the film integrates the signal this noise is not a problem when photographing an image. But it causes an annoying blurring of the trace In slow y-modulated line scans and can result in large errors if the signal if measured with a fast analog to digital converter (ADC).We interfaced an EDAX 9100/70 x-ray analyzer with a PV9242 line scan/mapping option to a Philips EM420 STEM. The EDAX unit controls the x-y raster and digitizes the detector signal at each pixel. When reading the raw signal from the standard Philips SED detector and amplifier the images were very noisy. This is because the ADC actually samples the signal for a very small portion of the total conversion time and then holds the sampled value for the actual conversion, effectively reading the signal for 0.3 usee out of 170 usec.
Preparation of integrated circuits for TEM electromigration in situ studies
Authors: Maskowitz J. V. , Rhoden W. E. , Kitchen D. R. , Omlor R. E. , Lloyd P. F. 
Published: June 2020

The fabrication of the aluminum bridge test vehicle for use in the crystallographic studies of electromigration involves several photolithographic processes, some common, while others quite unique. It is most important to start with a clean wafer of known orientation. The wafers used are 7 mil thick boron doped silicon. The diameter of the wafer is 1.5 inches with a resistivity of 10-20 ohm-cm. The crystallographic orientation is (111).Initial attempts were made to both drill and laser holes in the silicon wafers then back fill with photoresist or mounting wax. A diamond tipped dentist burr was used to successfully drill holes in the wafer. This proved unacceptable in that the perimeter of the hole was cracked and chipped. Additionally, the minimum size hole realizable was > 300 μm. The drilled holes could not be arrayed on the wafer to any extent because the wafer would not stand up to the stress of multiple drilling.
Ultrastructure and immunocytochemistry of interstitial cells of the deep muscular plexus in the canine small intestine
Authors: Torihashi Shigeko , Gerthoffer William T. , Sanders Kenton M. 
Published: June 2020

In the canine small intestine one of the pacemaker regions that generates electrical activity is located in the deep muscular plexus. Within this region special cells, known as interstitial cells (IC-DMP), are distributed. The ultrastructure and immuno-cytochemistry of IC-DMP were studied to clarify their identification and relationship to smooth muscle cells.Segments of the ileum were perfused through mesenteric arteries with a physiological buffer solution (pH5.0) for 3 min followed by a fixative (2.5% glutaraldehyde, 1.25mM Ca Cl2 and 3% sucrose in 0.05M cacodylate buffer; pH 7.4), postfixed in 1% OsO4 and embedded in Epon 812 for transmission electron microscopy (TEM). For immunoelectron microscopy, segments were perfused with a fixative solution (0.25% glutaraldehyde, 4% paraformaldehyde, 0.2% picric acid, 0.1% Triton X-100 and 0.1M phosphate buffer pH7.4), dehydrated and embedded in glycol methacrylate (GMA). Sections were stained with monoclonal antibody B4 to smooth muscle actin (ICN 1:200), anti-myosin light chain antibody (1:25), anti desmin- antibody(1:200), and anti-vimentin antibody (1:500) respectively. Immunoreactivities were detected by IgG gold (10nm, 6nm).
Ultrastructural studies of the digestive system of the leafhopper Euscelidius variegatus infected with BEV bacteria
Authors: Cheung W.W.K. 
Published: June 2020

The leafhopper Euscelidius variegatus Kirshbaum transmits plant diseases such as aster yellows and X-disease. It also harbours a BEV bacterium as a result of congenital infection . Since the bacterium can reduce the fecundity of the insect it has the potential of being used as a controlling agent for E. variegatus. Presently, little is known about the cytopathology of the host infected with BEV. This study aims to understand the damage done by the bacterium to the digestive system of E. variegatus and the defense reaction of the host to the bacterium.Digestive systems of BEV infected and non-infected adult females of E. variegatus were dissected in buffered insect saline and fixed in 2.5% glutaraldehyde in 0.1M sodium cacodylate (pH 7.2) for 1 hr. Tissues were post-fixed in 1% osmium tetroxide (pH 7.2) and dehydrated in alcohol/acetone series. These were blocked in Spurr resin and cut with a Reichart ultrotome. Thin sections were stained with uranyl acetate and lead citrate and were observed in a Zeiss EM 9S-2 electron microscope.
A microbial model for visualization of surface proteins using cryoimmobilization and high-resolution cryo-SEM
Authors: Erlandsen Stanley L. , Olmsted Stephen , Walther Paul , Chen Ya , Pawley Jim , Dunny Gary , Wells Carol L. 
Published: June 2020

Numerous studies on high resolution visualization of surface membrane proteins have utilized colloidal gold markers in conjunction with SEM, TEM, and by freeze-fracture cytochemistry using conventional or fracture flip methods, but in each case only information on the distribution of the marker complex, and not the actual structure of individual surface protein(s) was obtained.To investigate the detection of individual surface proteins, we have used a microbial model to examine surface proteins involved in conjugation or the transfer of DNA inEnterococcus faecalis. Two surface proteins encoded by the pCF10 plasmid, aggregation substance (Asc10; globular shape) and surface exclusion protein (Sec10; helical shape), mediate the aggregation of donor and recipient cells and prevent aggregation of like donor cells, respectively. Isogenic strains of E. faecalis that constitutively express neither Asc10 or Sec10 (pWM401) or both (pINY1801) were processed by 1) conventional chemical fixation, dehydration, critical point drying with CO2, ion beam sputtering with a discontinuous platinum film (<1 nm), and examination in a Hitachi S-900 FESEM operated at low voltage (<3 keV), or 2) cryoimmobilization of cells by high pressure freezing (Balzers HPM 010), mounting in a Gatan cryoholder followed by etching for 60 minutes at −100°C, cryocoating by planar magnetron sputtering (Balzers MED 010), and examination at −100°C in the S-900 FESEM.
Where’s the fat? Freeze-fracture analysis of ingredient interactions in food systems
Authors: Fincher Jean 
Published: June 2020

An important trend in the food industry today is reduction in the amount of fat in manufactured foods. Often fat reduction is accomplished by replacing part of the natural fat with carbohydrates which serve to bind water and increase viscosity. It is in understanding the roles of these two major components of food, fats and carbohydrates, that freeze-fracture is so important. It is well known that conventional fixation procedures are inadequate for many food products, in particular, foods with carbohydrates as a predominant structural feature. For some food science applications the advantages of freeze-fracture preparation procedures include not only the avoidance of chemical fixatives, but also the opportunity to control the temperature of the sample just prior to rapid freezing.In conventional foods freeze-fracture has been used most successfully in analysis of milk and milk products. Milk gels depend on interactions between lipid droplets and proteins. Whipped emulsions, either whipped cream or ice cream, involve complex interactions between lipid, protein, air cell surfaces, and added emulsifiers.
Scanning Tunneling Microscopy and low-temperature force microscopy of freeze-fractured samples
Authors: Fisher K. A. , Shattuck M. B. , Gustafsson M. G. L. , Clarke J. 
Published: June 2020

Monolayer freeze-fracture combined with scanned probe microscopy (SPM) offers unique advantages for studies of biological structure. The freeze-fracture methodology incorporates rapid freezing approaches for sample preservation and stabilization, and the scanned probe microscopies, especially scanning tunneling microscopy (STM) and atomic force microscopy (AFM), allow high resolution examination of surface features including digital mapping, quantification, and display. In routine biological STM a sharp conductive probe is positioned with piezoelectric transducers close to a conductive surface. When electron tunneling begins, the probe is scanned while electronic feedback maintains constant current. Because the tunneling current is logarithmically sensitive to separation between the tip and the sample, the feedback signal can be calibrated to indicate height with sub-Angstrom sensitivity and precision. In routine biological AFM, the sample is scanned while the force between the tip and the sample is kept constant.There are two fundamental problems in STM examinations of biological systems. First, biological samples are soft and are often perturbed by the scanning probe; and second, they are not electrically conductive. Coating samples with metal replicas simultaneously circumvents both these difficulties, conferring sample stability and electrical conductivity. The STM can be used to measure sample heights quite accurately, and has been used to measure the thickness and changes in thickness of metal-coated purple membrane and the depth of surface features of freeze-fracture replicas of synthetic phospholipids.
New polarized-light microscope for fast and orientation independent measurement of birefringent fine structure
Authors: Oldenbourg Rudolf 
Published: June 2020

The polarized light microscope has the unique potential to measure submicroscopic molecular arrangements dynamically and non-destructively in living cells and other specimens. With the traditional pol-scope, however, single images display only those anisotropic structures that have a limited range of orientations with respect to the polarization axes of the microscope. Furthermore, rapid measurements are restricted to a single image point or single area that exhibits uniform birefringence or other form of optical anisotropy, while measurements comparing several image points take an inordinately long time.We are developing a new kind of polarized light microscope which combines speed and high resolution in its measurement of the specimen anisotropy, irrespective of its orientation. The design of the new pol-scope is based on the traditional polarized light microscope with two essential modifications: circular polarizers replace linear polarizers and two electro-optical modulators replace the traditional compensator. A video camera and computer assisted image analysis provide measurements of specimen anisotropy in rapid succession for all points of the image comprising the field of view.
Laser-feedback microscopy: Fundamental principles and application to high-resolution biological imaging
Authors: Bearden Alan , Wong Terrence L. , Mitchell Morgan W. , Osborne Leslie C. , O’Neill Michael P. 
Published: June 2020

As discovered by Abbé, a fundamental limit to the lateral resolution of a conventional optical microscope is produced by “far-field” aperture diffraction at the objective lens. This limitation can be expressed in terms of the Airy disc which relates the obtainable resolution to the wavelength of light used and the objective’s numerical aperture (NA). In scanning confocal microscopy with a laser-produced Gaussian profile illumination beam, the lateral resolution in given by 1.22λ/NA. The axial resolution in this design is improved by the use of a pinhole aperture to pass light only from the objective’s focal plane. Typical best values for lateral (x,y) and axial (z) resolution for visible wavelength scanning confocal microscopy are ~200nm and ~300nm with a NA=1.4 oil immersion objective.Although optical microscopy displays limited resolution when compared to some forms of electron and scanning-probe microscopies (STM, AFM), the convenience of sample preparation and its ease in performing in vivo studies has given rise to new methods of increased resolution (e.g., “near field” techniques, photon-tunneling, phase interference contrast).
Direct mechanical measurement of single DNA molecules through an optical microscope
Authors: Bustamante Carlos , Smith Steven B. 
Published: June 2020

Understanding the mechanical properties of DNA such as their bending and torsional rigidity can provide a great deal of insight about the factors that determine the folding of DNA during the cell cycle. These quantities have been obtained from bulk experiments using light scattering, equilibrium sedimentation, DNA cyclization, etc. Determination of the elastic properties of DNA with these methods is indirect, via a theoretical framework relating the observable quantities to the elastic parameters of the molecules. Moreover, the results represent an ensemble average over all accessible configurations of the molecule, with small contribution from stretched un-likely states.We have carried a systematic study of the elastic properties of single DNA molecules. Single DNA molecules were chemically attached by one end to a glass surface and by their other end to a magnetic bead. Equilibrium positions of the beads are observed in an optical microscope while the beads are acted on by known magnetic and hydrodynamic forces.
Subcortical excitatory inputs to nigral dopaminergic and non-dopaminergic neurons: A light and Electron Microscopic study
Authors: Damlama Meri , Tepper James M. 
Published: June 2020

Midbrain dopaminergic neurons are involved in the symptomotology of motor disorders such as Parkinsonism as well as psychiatric disorders such as schizophrenia. The normal functioning of substantia nigra (SN) dopaminergic neurons is greatly influenced by their afferent inputs as evidenced by significant differences in the physiological characteristics of in vivo vs. in vitro preparations. Although the sources and neurotransmitters of many afferents to the SN are known, because dopaminergic and non-dopaminergic dendrites co-mingle in pars reticulata, the precise postsynaptic targets, particularly those of the presumed excitatory inputs, remain to be determined. In the present study inputs from the subthalamic (STN) and the pedunculopontine (PPN) nuclei (both presumed excitatory) to the SN were investigated by combined anterograde tracing and tyrosine hydroxylase (TH) immunocytochemistry at the light and electron microscopic levels.The anterograde tracers biocytin or PHA-L were iontophoretically injected into either the STN or the PPN. Following appropriate survival times the animals were perfused transcardially with a mixture of 4% paraformaldehyde and 0.2% glutaraldehyde.