bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation averaging: Lattice separation and resolution assessment
Authors: Radermacher M. , Frank J. , Mannella C.A.
Published: June 2020

Correlation averaging is a well established technique and has been extensively applied to the analysis of two-dimensional arrays in electron microscopy. The resolution of the structure of the unit cell can be improved in many situations compared to the resolution achievable by Fourier filtration techniques. Lattices of a specimen consisting of more than a single layer array can be reconstructed separately. we have analysed the theoretical background of some of the steps involved in the procedure. Our results confirm that a separate reconstruction of single overlapped layers is possible whenever the conditions found necessary for lattice separation by Fourier filtration are met.
Sectioning grids of negatively stained cytochrome oxidase crystals
Authors: Chang Tan , Frey Terrence G.
Published: June 2020

Three-dimensional reconstruction of proteins from data obtained by tilting two-dimensional crystals has provided a wealth of information on structures of membrane proteins and their relationship phospholipid bilayers. One limitation of this technique has been the restriction to tilt angles of, commonly, ±60" which results in decreased resolution perpendicular to the plane of the membrane. Interpretation of three-dimensional reconstructions of negatively stained specimens is also hampered by possible uneven staining of the two exterior surfaces of the membrane.
Reconstruction with noisy data
Authors: Barrett T. A.
Published: June 2020

The problem of deducing the 3-D structure of an object given a limited number of 2-D projections (e.g., STEM micrographs) is well-known. It is an ill-posed problem in the sense that very many solutions exist that have the same 2-D projections. If the data are assumed to be noisy (most STEM images are very noisy), then the problem is still ill-posed: many solutions exist that yield the same least-square error from the data.

Crewe et al. have shown that, remarkably, the constraint that many objects are essentially Boolean in nature (have constant density) means that their structure can be determined very well even with very few projections, if there is little noise.
Electron microscopic anatomy of the granulomatous giant cells of catfish
Authors: Liu K. C. , Mai L. M.
Published: June 2020

Giant cells are the histopathological units of granulomatous tissue which can be induced by the presence of endogenous or exogenous materials. Besides in other animals it has been reported in several fish species. A histopathological study of systemic granuloma in reared catfish Parasilurous asotus was reported in Taiwan. The ultrastructure of the giant cells of the granulomatous tissue of the same species of catfish was studied. The giant cells with a central amorphrous core, a transitional zone and a peripheral cellular zone (Fig. 1) is present in this report.
Collagen fibrillogenesis in vitro: interaction of types I and V collagen
Authors: Wasserman Arthur J. , Kloos Kathy C. , Birk David E.
Published: June 2020

Type I collagen is the predominant collagen in the cornea with type V collagen being a quantitatively minor component. However, the content of type V collagen (10-20%) in the cornea is high when compared to other tissues containing predominantly type I collagen. The corneal stroma has a homogeneous distribution of these two collagens, however, immunochemical localization of type V collagen requires the disruption of type I collagen structure. This indicates that these collagens may be arranged as heterpolymeric fibrils. This arrangement may be responsible for the control of fibril diameter necessary for corneal transparency. The purpose of this work is to study the in vitro assembly of collagen type V and to determine whether the interactions of these collagens influence fibril morphology.
Quantitation of intramembrane particles of Mcleod red cells
Authors: Khodadad J.K. , Weinstein R.S. , Steck T.L.
Published: June 2020

The McLeod phenotype is characterized by numerous acanthocytic red cells. Glaubensklee et al report a significant increase in numerical density and decrease in the volume of intramembrane particles (IMP) of McLeod red cells on unidirectionally shadowed replicas of freeze fractured membranes and suggest that the dissociation of band 3 glycoprotein in this membrane may underlie the abnormal shape. Rotary shadowing has several advantages over unidirectional shadowing rendering it more reliable for IMP counts. In this study we compare and quantitate the numerical densities of the IMP of red cells of normal donor and McLeod patient on rotary shadowed replicas.
A pre-embedding, protein a-gold immunolabelling technique for cytocentrifuged cell monolayers for lm and tem
Authors: Chien K. , Shintaku I.P. , Sassoon A.F. , de Velde R.L. Van , Heusser R.
Published: June 2020

Identification of cellular phenotype by cell surface antigens in conjunction with ultrastructural analysis of cellular morphology can be a useful tool in the study of biologic processes as well as in diagnostic histopathology. In this abstract, we describe a simple pre-embedding, protein A-gold staining method which is designed for cell suspensions combining the handling convenience of slide-mounted cell monolayers and the ability to evaluate specimen staining specificity prior to EM embedding.
A controlled environment system for vitrification of liquid tem samples
Authors: Bellare Oayesh
Published: June 2020

Vitrification of aqueous samples is becoming an important technique for visualization of biological and colloidal dispersions and aggregates by electron microscopy. Vitrification prevents phase separation, rearrangement and problems of electron optics interaction with a crystalline matrix and artifact formation due to crystal growth. Vitrification also reduces radiation damage in some samples. Water can be vitrified with ultrafast cooling (> 100,000 K/s) by rapid plunging into melting ethane. Electron diffraction of bulk water films, thinned by blotting and cryo-fixed by quenching, has provided direct evidence for vitrification.
Density gradient method for preparing fluid cell samples for diagnostic electron microscopy
Authors: Gillies C. , Eastwood C. , Leiper D. , Vitelli K.
Published: June 2020

The separation of lymphocytes from blood, applying the principle of differential migration through a density gradient, is used extensively in research. We first used Ficoll-Paque to prepare a lymphocyte sample for electron microscopy in a clinical study. We subsequently have used this solution to prepare cytologic specimens such as pleural and peritoneal fluid, as well as, bone marrow and small blood samples (1 ml) from infants, for diagnostic electron microscopy. The usual method of processing a cell suspension for electron microscopy is to centrifuge an aliquot of the sample, fix the resulting pellet, and proceed as for tissue samples. When the fluids are heavily contaminated with blood, however, this procedure may result in sections with few diagnostic cells in a sea of red blood cells.
Cluster ion impacts ontobacco mosaic virusparticles
Authors: Ledbetter M. C. , Beuhler R. J. , Friedman L.
Published: June 2020

Mass analyzed beams of accelerated cluster ions deposit large quantities of kinetic energy in assemblies of atoms at surfaces to produce extremely high transient pressures and temperatures on impact. We have shown that impacts of clusters of appropriate size and acceleration on naked and metalized carbon foils can be visualized by electron microscopy as structural alterations interpretable in terms of energy transfer processes. For these experiments on biomolecules we choseTobacco Mosaic Virus(TMV) as a well characterized macromolecular complex consisting of a single species of protein attached to a spiral of nucleic acid, all formed into a rod 180 by 3000 Å and having a mass of about 40 million daltons.
Localization of neuraminidase-sensitive regions in the Haemophilus pleuropneumoniae Capsule by enzyme-gold affinity cytochemistry
Authors: Steffens W. L. , Kadis S. , Byrd I. W.
Published: June 2020

Haemophilus pleuropneumoniae is the etiologic agent of a serious respiratory disease of swine known as porcine Haemophilus pleuropneumonia. There is some evidence suggesting the role of the capsule as a virulence factor in the pathogenesis of the organism and recent investigations have demonstrated and compared the appearance of the capsule in both virulent and avirulent strains by several mucopolysaccharide stains. Our own investigations have demonstrated variability in capsular sensitivity to the hydrolytic enzyme, neuraminidase which cleaves n-acetyl neuraminic acid (sialic acid) from mucins, including those found in several types of bacterial capsules. In an effort to localize the sites of neuraminidase sensitivity within the capsule and to possibly develop a scheme to quantitate the degree of neuraminidase sensitivity among differing serotypes and between cells of similar serotypes grown on complex and chemically defined medium, affinity cytochemistry utilizing colloidal gold-labelled neuraminidase was employed.
Scanning electron microscopy of composite hydroxylapatite/plaster implants for bone reconstruction
Authors: Hanker J. S. , Giammara B. L.
Published: June 2020

Nonresorbable sintered ceramic hydroxylapatite (HA) is widely employed for filling defects in jaw bone. The small particles used for alveolar ridge augmentation in edentulous patients or for infrabony defects due to periodontal disease tend to scatter when implanted using water or saline as the vehicle. Larger blocks of this material used for filling sockets after tooth extraction don't fit well. Studies in our laboratory where we compared bovine serum albumin, collagen and plaster of Paris as binders to prevent particle scatter during implantation suggested that plaster was most useful for this purpose. In addition to preventing scatter of the particles, plaster enables the formation of implants of any size and.shape either prior to or during surgery. Studies with the PATS reaction have indicated that plaster acts as a scaffold for the incorporation of HA particles into bone in areas where the implant contacts either host bone or periosteum. The shape and integrity of the implant is maintained by the plaster component until it is replaced over a period of days by fibrovascular tissue.
Membrane-associated microtubular areays induced in proximal myelinated processes of dorsal root ganglia by large doses of vitamin B6
Authors: Montpetit V.J. , Dancea S. , Tryphonas L. , Clapin D.F.
Published: June 2020

Very large doses of pyridoxine (vitamin B6) are neurotoxic in humans, selectively affecting the peripheral sensory nerves. We have undertaken a study of the morphological and biochemical aspects of pyridoxine neurotoxicity in an animal model system. Early morphological changes in dorsal root ganglia (DRG) associated with pyridoxine megadoses include proliferation of neurofilaments, ribosomes, rough endoplasmic reticulum, and Golgi complexes. We present in this report evidence of the formation of unique aggregates of microtubules and membranes in the proximal processes of DRG which are induced by high levels of pyridoxine.
A sample preparation and microprobe x-ray imaging method for histological localization of cisplatin
Authors: Hook G.R.
Published: June 2020

Cis-diamminedichloroplatinuum II (CDDP or cisplatin) is a chemotherapeutic drug used to treat cancers of the testicals, ovaries, head, neck and bladder. Although the histological distribution of cisplatin may provide important information on the drug's affect, the cisplatin histological distribution has not been determined because suitable sample preparation and analytical methods have not been developed. We describe here a sample preparation and analytical method to image cisplatin at histological resolution within rat abdominal wall tissue.
Crystallization sequence of an A1N-Y2O3-SiO2 glass-ceramic
Authors: Dinger T.R. , Thomas G.
Published: June 2020

The use of Si3N4, alloys for high temperature, high stress structural applications has prompted numerous studies of the oxynitride glasses which exist as intergranular phases in their microstructures. Oxynitride glasses have been investigated recently in their bulk form in order to understand their crystallization behavior for subsequent Si3N4 applications and to investigate their worth as glass-ceramic precursors. This research investigates the crystallization sequence of a glass having a normalized composition of Y26Si30Al11 ON11 and lying in the A1N-Y2O3-SiO2 section of the Y-Si-Al-O-N system. Such glasses exist as intergranular phases in the technologically important Y2O3/Al2O3-fluxed Si3N4 alloys.
AEM investigation of the noncrystalline phase in a mullite/zirconia/titania composite
Authors: Srikrishna K. , Thomas G. , Moya J. S.
Published: June 2020

Reaction sintering of zircon and alumina has emerged as an economically attractive route for obtaining high toughness zirconia composites. To reduce sintering temperatures various techniques such as the use of fine reactive powders, hot pressing and sintering additives such as MgO and TiO2 have been used. All these techniques have their potential disadvantages and it has been argued that the use of an additive capable of acting in solid solution will prove beneficial to the microstructure without any associated problems.
Strain analysis in composite ceramics
Authors: Kriven W. M.
Published: June 2020

Significant progress towards a fundamental understanding of transformation toughening in composite zirconia ceramics was made possible by the application of a TEM contrast analysis technique for imaging elastic strains. Spherical zirconia particles dispersed in a large-grained alumina matrix were examined by 1 MeV HVEM to simulate bulk conditions. A thermal contraction mismatch arose on cooling from the processing temperature of 1500°C to RT. Tetragonal ZrO2 contracted amisotropically with α(ct) = 16 X 10-6/°C and α(at) = 11 X 10-6/°C and faster than Al2O3 which contracted relatively isotropically at α = 8 X 10-6/°C. A volume increase of +4.9% accompanied the transformation to monoclinic symmetry at room temperature. The elastic strain field surrounding a particle before transformation was 3-dimensionally correlated with the internal crystallographic orientation of the particle and with the strain field after transformation. The aim of this paper is to theoretically and experimentally describe this technique using the ZrO2 as an example and thereby to illustrate the experimental requirements Tor such an analysis in other systems.
Microanalytical investigations of ordering in Y2O3-doped tetragonal zirconia polycrystals
Authors: Bielicki T.A. , Thomas G.
Published: June 2020

The crystal structures of zirconia have been widely studied in relation to its transformation toughening and ionic conduction properties. The system of zirconia stabilised with Y2O3 is important in both applications. This investigation concerns the observation of unexpected crystallographic features in a fine-grained 2.3 mol% Y2O3 composition. This material is an example of the mechanically-outstanding “tetragonal zirconia polycrystals” (TZP) materials, in which virtually all of the ZrO2 is believed to be retained in the crucial tetragonal phase.
HREM images and atom positions
Authors: Saxton W. O.
Published: June 2020

How accurately may atomic positions (in projection, at least) be deduced from high resolution electron images? If your experience begins before the last ten to fifteen years, when ‘lattice’ and ‘atomic’ images have become almost commonplace, you are likely to regard a micrograph as at least as much a complicated interference pattern as an image, and be much less sanguine than younger microscopists about the accuracy with which dark spots in images may be expected to correspond to actual atomic sites. The ‘simulation’ approach to image intepretation, in which atomic positions are deduced via a comparison of experimental and calculated images whether or not these bear any direct interpretation, is born of this caution; however, atomic sites are increasingly being inferred directly from micrographs, and this paper is concerned with the two principal ways in which digital processing can be used to make the process more reliable.
Nucleation of γ' plates from G.P. zones in an Al-Ag alloy
Authors: Howe J.M. , Gronsky R.
Published: June 2020

Experimental and theoretical studies on the role of G.P. zones in the nucleation of either transition or equilibrium phases have been an active area of research for many years. In Al-Ag alloys, these zones are not usually thought to serve as nucleation sites for metastable γ' plates, although the alternative view was expressed during early research on this system. Instead, γ' plates are nucleated either by the splitting of perfect a/2<110> dislocations into pairs of a/6<112> Shockley partial dislocations, or by the propagation of a Shockley partial dislocation across an a/3<111> Frank loop. The stacking faults produced by these reactions thus create an initial two-atom layer of hep γ' precipitate. However, in this study it was found that γ' plates can nucleate from G.P. zones during ion milling of thin foils prior to TEM examination.
Metastable phases formed in rapidly solidified Nb-Ge alloys
Authors: Evans N. D. , Bayuzick R. J. , Kenik E. A.
Published: June 2020

The 100 meter Long Drop Tube, located within the Marshall Space Flight Center in Huntsville, AL, provides a unique opportunity for the study of rapid solidification of bulk processed materials. Here, Nb-Ge alloys have been melted into large drops in an electromagnetic levitation furnace, and then released to fall down the tube. Drops were approximately 300 mg in mass and 2-3 mm in diameter. A data acquisition system recorded the release temperature, and the resulting cooling curve from each specimen which may have included recalescence events. Knowledge of thermophysical parameters then allowed the determination of the undercooling. More extensive discussions of the drop tube are elsewhere. Undercoolings of 350 K (0.15 Tm) have been achieved.
A TEM study of the influence of microstructure on the superplastic behavior of a U-5.8 wt.% Nb alloy
Authors: Ludtka G. Mackiewicz
Published: June 2020

Historically, metals exhibit superplasticity only while forming in a two-phase field because a two-phase microstructure helps ensure a fine, stable grain size. In the U-5.8 Nb alloy, superplastici ty exists for up to 2 h in the single phase field (γ1) at 670°C. This is above the equilibrium monotectoid temperature of 647°C. Utilizing dilatometry, the superplastic (SP) U-5.8 Nb alloy requires superheating to 658°C to initiate the α+γ2 → γ1 transformation at a heating rate of 1.5°C/s. Hence, the U-5.8 Nb alloy exhibits an anomolous superplastic behavior.
A parallel-detection electron spectrometer using quadrupole lenses
Authors: Ahn Channing C. , Krivanek Ondrej L.
Published: June 2020

Serial detection systems that are standardly employed in electron energy loss spectrometry (EELS) only examine one energy channel at a time and are therefore inherently inefficient. Parallel detection systems using either photodiode arrays or charge-coupled devices (CCDs) promise to remove this inefficiency. However, to completely replace the serial detection systems, they will need 1) a detective quantum efficiency (DQE) approaching 100%, 2) a dynamic range sufficient to cover the range of intensities encountered in the energy loss spectra (about 106), and 3) ability to operate without any loss in energy resolution.

We have constructed and tested a parallel detection system which incorporates three quadrupole lenses placed after the magnetic sector prism of the Gatan 607 spectrometer, a single crystal YAG scintillator, and a fiber-optically coupled linear photodiode array. The quadrupoles magnify the small dispersion (1.8μm per eV at 100kV primary voltage) of the spectrum produced by the magnetic sector to as high as 1 mm per eV without producing any spectrum rotation and with small power requirements.
On parallel illumination conditions for ALCHEMI
Authors: Christenson K. K. , Eades J. A.
Published: June 2020

ALCHEMI is a technique for locating atomic species within a crystal structure. It depends on the fact that, near low index planes or zone axes, the ratio of the x-ray signals from different sublattices vary as a function of the angle between the incident beam and the crystal structure.

In order to see the changes in these ratios, it is necessary that the illumination be close to parallel in order to minimize the angular range of the measurement. In simple cases it is sufficient to make the convergence angle smaller than the operating Bragg angle. This requirement can often be met by the conditions of a focussed probe.
A SEM/TEM examination of a ceramic membrane
Authors: Voegele-Kliewer C.E. , McMaster A.D. , Dirks G.W.
Published: June 2020

Materials other than polymers, e.g. ceramic silicates, are currently being investigated for gas separation processes. The permeation characteristics of one such material, Vycor (Corning Glass #1370), have been reported for the separation of hydrogen from hydrogen iodide. This paper will describe the electron microscopy techniques applied to reveal the porous microstructure of a Vycor membrane. The application of these techniques has led to an increased understanding in the relationship between the substructure and the gas transport properties of this material.
A microdiffraction study of Os10C(Co)24-2 in the Scanning Transmission Electron Microscope
Authors: Mochel M. E. , Masel R. I. , Mochel J. M.
Published: June 2020

Recent papers have discussed some of the difficulties in determining the structure of very small (<10Å) metal particles using electron microscopy. One of the ideas in the literature is that electron diffraction could provide structural information even under conditions where imaging is difficult. The purpose of the work reported here is to demonstrate that one can use electron diffraction techniques to obtain structural information about small metal particles, in this case 5Å osmium particles on a carbon film.
Mass thickness determination by use of Bethe sum rule normalization in Eels
Authors: Crozier P. A. , Egerton R. F.
Published: June 2020

In analytical electron microscopy it is desirable to have a method of determining the local mass thickness of a sample. One area where this is of importance is in the experimental determination of the electron scattering cross-sections required in EELS micro-analysis. For several years, the Bethe sum rule has been used to place relative cross-section measurements from gases on an absolute scale. We have applied this method to the energy loss spectra recorded frcm thin films in the electron microscope.
Electron microscope characterization of MOCVD-grown gap layers on Si
Authors: Jones K.M. , Al-Jassim M.M. , Olson J.M.
Published: June 2020

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).
On the role of tin underlays for the prevention of thermal grooving in thin gold films
Authors: Kim Jin Young , Hummel R. E. , DeHoff R. T.
Published: June 2020

Gold thin film metallizations in microelectronic circuits have a distinct advantage over those consisting of aluminum because they are less susceptible to electromigration. When electromigration is no longer the principal failure mechanism, other failure mechanisms caused by d.c. stressing might become important. In gold thin-film metallizations, grain boundary grooving is the principal failure mechanism.

Previous studies have shown that grain boundary grooving in gold films can be prevented by an indium underlay between the substrate and gold. The beneficial effect of the In/Au composite film is mainly due to roughening of the surface of the gold films, redistribution of indium on the gold films and formation of In2O3 on the free surface and along the grain boundaries of the gold films during air annealing.
Structural changes in silicon-on-insulator material during post-implantation annealing
Authors: Jung C. O. , Krause S. J. , Wilson S.R.
Published: June 2020

Silicon-on-insulator (SOI) structures have excellent potential for future use in radiation hardened and high speed integrated circuits. For device fabrication in SOI material a high quality superficial Si layer above a buried oxide layer is required. Recently, Celler et al. reported that post-implantation annealing of oxygen implanted SOI at very high temperatures would eliminate virtually all defects and precipiates in the superficial Si layer. In this work we are reporting on the effect of three different post implantation annealing cycles on the structure of oxygen implanted SOI samples which were implanted under the same conditions.
In situ STEM observations of electromigration on thin aluminum stripes
Authors: Maskowitz J. V. , Rhoden W. E. , Kitchen D. R. , Omlor R. E. , Lloyd P. F.
Published: June 2020

The existence of electromigration in thin films has been acknowledged since the early sixties. Electromigration is described as the main transport for atoms in a conductor under a current stress. Initial interest had been of a theoretical nature as electromigration had little impact on circuit reliability. With the maturing of Very Large Scale Integrated Circuit (VLSI) technology, current densities are exceeding 106 Amps/cm2 while linestripes are reaching into the submicron range. In this environment, electromigration can cause unwanted open or short circuits in thin films. This has serious implications on the reliability of any integrated circuit. By 1990, millions of transistors may be fabricated on a chip with feature sizes smaller than the wavelength of visible light.
High-resolution characterization of zeolites
Authors: Gómez-Castillo R. , Angel-Vicente P. Del , Domínguez-Esquivel J. M.
Published: June 2020

Structural variations such as microdefects, symmetry changes and crystalline intergrowths might influence the catalytic and chemisorptive properties of zeolites. Those variations occur at a very local scale, making it that traditional x-ray diffraction techniques are unsuitable to detect them. The alternative methods are high resolution electron microscopy and solid state- NMR.

The HREM images obtained in the microscope are influenced by instabilites of the zeolite crystals, beam damage, electronoptical parameters and other dynamical interactions, which add each other to produce a rather complex picture. Thus, the correct interpretation of results requires the determination of pa rameters, i.e. defocus, resolution level, astigmatism, etc.; together with the calculation of images, i.e. through Multislice methods.
The evaluation of six sealants used to encapsulate insulation material which contains asbestos
Authors: Hubbard J. L. , Papanicolopoulos C. D. , Jackson R. L.
Published: June 2020

The spraying of insulation which contains asbestos onto the steel structure of large buildings was a common construction practice in the past. Unfortunately, due to the recently disclosed health hazard associated with asbestos fibers, the business community is now faced with controlling a substance found in the most inaccessible areas of their structures. Many of these areas represent the return air plenum for the heating and air conditioning systems and as such can represent a health concern for all who occupy the building. Removal of this material is very expensive and at times impossible because of location. The need for a material which can penetrate and seal this insulation is unquestioned. There are a number of products on the market which claim to perform this task and the following study is a set of tests designed to evaluate some of these products.
Studies on natural silks of insects
Authors: Mazzone H.M. , Douglas S.M.
Published: June 2020

The role of silk among the arthropods has been reviewed, and these reports ascribe much importance to the production of silks and to their extramural functions as protective cocoons, trapping webs, and attachment fibers. Although considerable data are available on fibroin and sericin, the proteins comprising silk, there is little information on the morphological and biochemical properties of whole, natural silk (raw silk) extruded from arthropods, e.g., insects. We have studied and compared natural silk from two insects: the gypsy moth,Lymantria disparLinnaeus, and the silk worm,Bombyx mori, Linnaeus. The comparisons were structural studies by scanning electron microscopy (SEM) and amino acid (AA) composition by automated analysis.
A comparison of hog and synthetic bristles
Authors: Barish Leo
Published: June 2020

It is generally accepted that hog bristles hold paint and resist dripping better than synthetics. It would appear that these properties may be related to the wettability of the bristle surfaces by paint. As an analog, experiments were performed in which advancing and receding contact angles of drops of mineral oil were measured against bristle surfaces. Surprisingly, it was found that hog bristles produced higher contact angles indicating that wetting was actually less than that of synthetics.

Major differences in the texture of the surfaces between both types of bristles were found which probably relate to paint holding ability. Whereas conventional synthetic bristles showed smooth, featureless surfaces, the hog bristles (Figure 1) exhibit a very rough, scaled structure. Such an intricate surface would be expected to present a greater area and entrap paint better than a smooth surface.
Atomic chemistry by HREM and image simulations?
Authors: Howe J.M. , Gronsky R.
Published: June 2020

The technique of high-resolution electron microscopy (HREM) is invaluable to the materials scientist because it allows examination of microstructural features at levels of resolution that are unobtainable by most other methods. Although the structural information which can be determined by HREM and accompanying image simulations has been well documented in the literature, there have only been a few cases where this technique has been used to reveal the chemistry of individual columns or planes of atoms, as occur in segregated and ordered materials.
Microstructural observations of flux-sintered barium titanate
Authors: Armstrong T. R. , Buchanan R. C.
Published: June 2020

High permittivity materials are usually based on BaTiO3 and other Perovskite systems. Hetero-substitution of Ca, Pb, Zr, and Sn provide the necessary control in selection of suitable dielectric constants, temperature-resistance coefficients and dielectric losses. However, preparation of these materials require sintering temperatures in excess of 1300°C and often extended sintering times. Lower sintering temperatures are economically favorable and commercially important in monolithic capacitor fabrication, since they allow the use of base metal electrode systems such as Ni or Cu, replacing the more expensive Ag-Pd systems now employed. The approach has been to lower the sintering temperature of the dielectric by small additions of fluxing agents such as LiF and borates, which promote liquid phase sintering. By sintering in the presence of a liquid, densities approaching theoretical can be achieved at significantly reduced densification temperatures and times. With the electronic industries trend toward miniaturization, dielectrics with a high dielectric constant and low sintering temperature offer a significant advance in packaging density.
Ore characterization by digital color x-ray mapping
Authors: DeMiglio D.S.
Published: June 2020

A silver ore was examined by scanning electron microscopy (SEM) to aid in the selection of an extraction process by documenting the distribution and association of elements found within a representative sampling of ore particles. Through the use of color image processing similar to that used by Krakow digital X-ray maps were acquired which showed elemental distributions indicative of mineral phases previously identified by X-ray powder diffraction. Prior to this investigation silver particles (<10 microns) were observed to be randomly distributed throughout the host rock which was primarily a silica gangue.
Observation of slip propagation across grain boundaries in Ni3Al
Authors: Baker I. , Schulson E.M. , Horton J.A.
Published: June 2020

Recent modelling of the grain size dependence of the room-temperature yield strength of Ni3Al has invoked the concept of dislocation pile-ups. The idea is that the yield strength measured in the Liiders regime (i.e. the Liiders band propagation stress) represents not the stress to independently nucleate slip in each grain but the stress required to propagate slip through the material. This paper presents direct evidence of slip propagation from one grain to the next and thus validation of the use of a pile-up model for Ni3Al.

Miniature tensile specimens (3 mm x 7 mm x0.2 mm), made from an extruded rod of fine-grained (∽10 μm) Ni3Al containing 0.35 at.% boron, were strained under tension whilst being observed in a Philips EM 430T operated at 300 KV. Details of the design and operation of the straining stage and of the specimen preparation techniques are given elsewhere.
Computer-assisted analysis of incomplete powder electron diffraction patterns
Authors: Gibbon Donald L. , Komlosi Beverly J.
Published: June 2020

Incomplete powder electron diffraction patterns are traditionally difficult to interpret and are usually simply overlooked as being a sort of not-veryuseful background noise in the flow of data gathered in sample analysis. However, if techniques can be developed to systematize the information contained in those patterns, it can be a major contribution to the unravelling of complex materials problems. The following simple techniques are applied in our laboratories:

1. Patterns are recorded on Technical Pan 35mm film, using a double-exposure to obtain a well-exposed record of the rings and spots; a very small central spot is exposed at much lower intensity with the beam stop removed. The film is developed at high contrast in HC-110, dilution F (1:9).
HVEM and conventional TEM studies of post-shadow labeled surface molecules in freeze-etch replicas
Authors: Dinchuk J. E. , T.J.A. Johnson , J.E. Rash
Published: June 2020

Post-shadow labeling of freeze-etch replicas permits 3-dimensional molecular localization to within 10-30 nm. In this tutorial, we will describe methods of postshadow labeling as well as the use of simple systems for testing reagents and for evaluating the steps in this new methodology.

Preparation of Murine Splenic Lymphocytes

Murine splenic lymphocytes are isolated by gentle disruption of fresh spleen and fixed in suspension by addition of glutaraldehyde to a final concentration of 2%. After two minutes, 1.0 M glycine is added to a concentration of 0.1 M and the cells are pelleted at 500 x g for 5 minutes.
Optical microscopy beyond the diffraction limit
Authors: Betzig Eric
Published: June 2020

The near-field optical interaction between a sharp probe and a sample of interest can be exploited to image, spectroscopically probe, or modify surfaces at a resolution (currently down to ~12 nm with visible light) well beyond the diffraction limited response of traditional far-field systems. The resulting technique, near-field scanning optical microscopy (NSOM), still retains many of the attractive features of conventional optics, including non-invasiveness, low cost, reliability, and ease of use. Most importantly, NSOM takes advantage of the numerous and powerful contrast mechanisms and associated sample preparation procedures developed for optical microscopy over the last three centuries.

Several applications have been investigated to demonstrate the versatility arising from these contrast mechanisms. For example, polarization contrast has been coupled with near-field surface modification capabilities to image and record domains in thin-film magneto-optic materials (Fig. 1). This might form the basis for a new method of ultra-high density optical data storage, or could be used in a study of domain wall energetics in magnetic systems.

In the biological arena, NSOM has been used to image fluorescently labeled cytoskeletal actin in fixed mouse fibroblast cells (Fig. 2), and applied in a study of the actin organization within wound healing protrusions. The resulting images were also compared to topographic data arising from the shear force mechanism which regulates the probe-to-sample separation.
The presence of active, mature goblet cells in the small intestine of newborn miniature piglets
Authors: Kömüves László G.
Published: June 2020

Goblet cells in the intestine produce intestinal mucus, which acts as a protective barrier. Histochemical studies in 1-wk-old piglets have shown that goblet cells were fully mature, and contained both neutral and acidic mucopolysaccharides. There is no information, however, about the secretory activity of goblet cells in newborn piglets. We present evidence that goblet cells in newborn, nonsuckled miniature piglets actively synthesize and secrete glycoproteins, as detected by wheat germ agglutiningold conjugates (WGA-AU15) in LR White-embedded tissues. Details of the surgical procedures, tissue collection, fixation and tissue processing have been reported. Nonspecific binding of WGA-Au15 to the sections was prevented by incubating the grids on drop of 10 mM Trizma buffer, pH=7.4, containing 0.1% Tween 20, and 500 mM NaCl, for 30 min. This buffer was used to dilute WGA-AU15. The grids were then incubated with WGA-AU15, for 60 min, followed by extensive washing. Inclusion of free WGA or 1 mM N-acetyl-glucosamine in the buffer abolished the labelling by WGA-AU15.
An improved method for ultrastructural examination of paraffin-embedded tissues for diagnostic purposes
Authors: Howard Tamara A. , Ziesmer Donna N. , Ries Ardith L. , Becich Michael J.
Published: June 2020

Small cell tumors, liver and skin biopsies for metabolic disorders, soft tissue tumors and kidney biopsies are the paraffin embedded tissues most frequently requested for ultrastructural examination. Preservation of cell membranes, glycogen, mucopolysaccharides, glycoproteins, glycolipids and other soluble components is problematic in these cases. Causes of cellular extraction when processing paraffin embedded tissue are:

a) inadequate fixation of carbohydrates, mucopolysaccarides, glycoproteins and glycolipids

b) extraction of lipids and cell membranes by polar solvents

c) temperature effects

d) extraction of sugars and glycoproteins due to pH and non-buffered, hypo-osmolar solutions.

A methodology which improves preservation is described below:

1) Tissue samples are cut from paraffin blocks and deparaffinized in 2 changes of xylene at 4°C for 2-4 h (low temperature decreases extraction in solvent).

2) The samples are then rehydrated through a decreasing series of acetone concentrations (5-10 min each) at 4°C to 2, 5-10 min changes of 0.1 M cacodylate buffer containing 14.4 mM sucrose and 3.5 mM CaCl2, pH 7.8 (less polar solvent -- acetone vs. ethanol -- should decrease lipid extraction thereby enhancing membrane preservation)
Application of high-resolution field-emission LVSEM, backscatter imaging, immunogold staining to definition of the spatial distributions of two human neutrophil adherence receptors
Authors: Nelson Robert D. , Hasslen Sharon R. , Erlandsen Stanley L.
Published: June 2020

Receptors are commonly defined in terms of number per cell, affinity for ligand, chemical structure, mode of attachment to the cell surface, and mechanism of signal transduction. We propose to show that knowledge of spatial distribution of receptors on the cell surface can provide additional clues to their function and components of functional control.

L-selectin and Mac-1 denote two receptor populations on the neutrophil surface that mediate neutrophil-endothelial cell adherence interactions and provide for targeting of neutrophil recruitment to sites of inflammation. We have studied the spatial distributions of these receptors using LVSEM and backscatter imaging of isolated human neutrophils stained with mouse anti-receptor (primary) antibody and goat anti-mouse (secondary) antibody conjugated to 12 nm colloidal gold. This combination of techniques provides for three-dimensional analysis of the expression of these receptors on different surface membrane domains of the neutrophil: the ruffles and microvilli that project from the cell surface, and the cell body between these projecting structures.
Immunocytochemical localization of a brush border hydrolase, lactase, in newborn suckling rat jejunum
Authors: Kömüves László G. , Dudley Mary A. , Nichols Buford L.
Published: June 2020

Lactase-phlorizin hydrolase (LPH, EC 3.2.1.23), an integral membrane glycoprotein of the small intestinal brush border, converts lactose, the main carbohydrate in milk, to its monosaccharide components. Although the activity of LPH is high in suckling rats, little is known about its distribution within the intracellular compartments of the secretory pathway and brush border. We present the first description of the ultrastructural localization of LPH in the neonatal jejunum of suckling rat pups.

Pieces of jejunum from 12- to 14-d-old suckling rat pups from three litters of Sprague- Dawley rats were fixed with 4% freshly prepared paraformaldehyde in 100 mM phosphate buffer, pH=7.40, for 4 h, and stored in 1% paraformaldehyde, at 4°C, until further processing. The samples were sectioned after cryoprotection in 2.3 M sucrose in an RMC MT-7 ultramicrotome equipped with CR21 cryoattachment. Ultrathin cryosections were collected on Formvar-coated, carbon-evaporated nickel grids. The nonspecific binding sites were blocked by 1% heat-inactivated newborn calf serum in 10 mM Trizma buffer, pH=7.60, containing 500 mM NaCl, 0.05% NaN3and 20 mM glycine (buffer A).
Freeze-fracture views of membrane motors of bacteria
Authors: Khan Shahid
Published: June 2020

The locomotory organelles of many bacteria are long, helical filaments called flagella. Bacterial flagella rotate. Flagellar rotation is driven by a molecular motor that is part of the membrane embedded flagellar base and fueled by electrochemical proton (or sodium) gradients. Rapid-freeze electron microscopy has revealed that rings of intramembrane particles found clustered around flagellar bases are a key structural module of this motor.

The morphology of the ring particles provides clues to their function. The particles are located in the cytoplasmic membrane across which the electrochemical gradients that energize flagellar rotation are maintained. In Escherichia coli, in addition to proteins needed for assembly of the flagellum, two proteins, MotA and MotB, are required for motility. MotA conducts protons across membranes and interacts with MotB, a protein with a large periplasmic domain. In non-motile mutants lacking MotA and MotB, flagellar bases lack the particle rings. Plasmid based expression of both MotA and MotB is necessary for restoration of motility and the ring structures.
The incenps: Chromosomal proteins with an essential cytoskeletal role during mitosis
Authors: Mackay Alastair M. , Chue Calvin , Mark Eckley D. , Earnshaw William C.
Published: June 2020

The INCENPs (INnerCENtromereProteins - Mr133 and 145 kDa) are tightly bound to chromatin until early metaphase, and arrive at the metaphase spindle plate as integral components of the chromosomes (Cooke et al., 1987; Earnshaw & Cooke, 1991). It is thus surprising that the INCENPs leave the chromosomes during the latter part of metaphase to become associated with fibrous structures traversing the metaphase plate (presumably the overlapping polar microtubules of the spindle). Following the onset of anaphase, the INCENPs remain closely associated with the stem body material in the central spindle and also become associated with the inner surface of the cell membrane at the position where the cleavage furrow subsequently forms.

By combining library screening with reverse-transcriptase PCR, we have recovered cDNA clones that contain the complete open reading frames (ORFs) of the two chicken INCENPs. Class 1 INCENP cDNA contains an ORF of 839 codons, which includes a predicted central coiled-coil domain of about 200 residues.
The dynamics of synapse formation: Time-lapse observations by confocal fluorescence microscopy in hippocampal slices and zebra-fish embryos
Authors: Smith Stephen J , Dailey Michael E. , Pike Susan , Buchanan JoAnn , Bergles Dwight E.
Published: June 2020

Our present information about the formation of synapses in the central nervous system is based almost exclusively on observations of fixed tissue specimens. Such observations can only provide very limited inference about the dynamics of the underlying developmental processes. In the hopes of obtaining direct information about the dynamics of synapse formation, we have explored new methods that allow repeated, high-resolution optical imaging of synapse formation events in live neural tissues.

Our efforts have focused on specific excitatory synapses in two vertebrate nervous systems: (1) the mossy-fiber-to-CA3-pyramidal-cell synapse in the hippocampus of postnatal day 4-8 rats and (2) the mauthner-fiber-to-motoneuron synapse in intact early embryos of the zebrafish Brachydanio rerio. We are using laser-scanning confocal fluorescence microscopy and fluorescent membrane stains such as di- I and di-O. Individual neurons or limited subsets of the neurons within a tissue are stained by applying these dyes in dimethylformamide solution through micropipettes.
High-resolution 3-D and 4-D imaging using wide-field CCD-based microscopy
Authors: Swedlow Jason R. , Scalettar Bethe A. , Sedat John W. , Agard David A.
Published: June 2020

Because of the limited numerical aperture of a light microscope objective lens, every image recorded from a microscope is blurred and therefore degraded. This problem is particularly acute when a full three-dimensional image stack is viewed in projection. The blurred image is a convolution between every light source in an object and the point-spread function (PSF) of the objective lens and can be mathematically calculated or empirically measured. To eliminate blurring, we record three- and four-dimensional images with a charge-coupled device (CCD) -based computerized optical sectioning microscope and mathematically deconvolve out-of-focus photons using the appropriate three-dimensional, empirically measured PSF. The use of the empirical PSF is important because of the presence of a partial confocal effect in a wide field microscope caused by the presence of the field diaphragm. The advantage in this method is that collection and restoration of out-of-focus photons results in high sensitivity and resolution.

In order to follow nuclear and chromosome dynamics, we have injected Drosophila melanogaster embryos with various fluorescent proteins and then monitored the distribution of these proteins during mitosis by recording a series of three-dimensional data sets at regular time intervals-- a four dimensional data set.