bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthetic aluminous goethite investigated by high-resolution transmission electron microscopy
Authors: Dixon J. B. , Golden D. C. , Calhoun F. G. , Buseck P. R. 
Published: June 2020

Goethite (alpha-FeOOH) contributes significantly to aggregation and color of soils. Since goethite of soils usually occurs in low concentrations its investigation would be enhanced if it can be synthesized in a pure form especially if it resembles its form in soils by being fine grained and with some Al substitution. This report presents morphological and structural information on synthetic aluminous goethite prepared by a simple laboratory procedure. Aluminum substitution greater than 11 mole % appreciably reduces crystal size and increases the tendency for aggregation.The surface crust of a botryoidal goethite from Biwabik, MN, USA (Source: Wards Natural Science Establishment, Rochester, NY) was crushed in acetone to a fine powder. A series of pure goethites also was prepared from Fe(CIO4)2 and A1(CIO4)3. The synthetic samples were then digested in a bomb for 17 hr at 150°C. All samples were dispersed in an ultrasonic water bath for 30 minutes prior to dip mounting on Cu grids coated with a holey carbon mesh.
Explosive consolidation of amorphous iron-base alloy powder
Authors: Shankar S. , Murr L.E. , Hare A.W. 
Published: June 2020

Amorphous metals and alloys, and especially the metallic glass ribbon or Metglas alloys developed by Allied Corporation, have been shown to have very remarkable properties. There is special interest in magnetic iron-base alloy ribbon which is finding commercial uses in electromagnetic laminate applications such as transformers. There is intense interest in fabricating other metal glass structures, but conventional powder metallurgy techniques are intractible even when amorphous powders are available because of the dramatic property degradation when crystallization occurs at elevated temperatures.Recent research has demonstrated that metal and alloy powders can be efficiently consolidated using explosives. The resulting materials can have unique microstructure and properties, and under certain circumstances, interparticle melting does not seem to occur, and particle bonding is apparently achieved by a kind of “mechanical mixing” similar to that explored earlier by Benjamin, and more recently by Kang. In addition, Murr, et al have also recently demonstrated that the passage of strong shock waves through amorphous (glassy) iron-base ribbon at pressures as high as 30 GPa (and 2 μs pulse duration) did not induce crystallization.
A HREM study of the interfacial structure of γ' precipitate plates in an Al-15 wt % Ag alloy
Authors: Howe J.M. 
Published: June 2020

The interfacial structure and growth kinetics of γ' and γ (Ag2Al) precipitate plates in Al-Ag alloys have been extensively studied by conventional TEM methods. Although most results have confirmed the predictions of the general theory of precipitate morphology proposed by Aaronson, some new questions have arisen. The present study is an attempt to address the specific points of contention concerning the details of ledge growth in this system.An Al-15 wt % Ag alloy was solution treated at 500°C for 30 minutes, quenched and aged for 30 minutes at 350°C. Thin foils were jet polished in a nitric acid-methanol solution and lightly ion-beam milled prior to insertion into a JE0L 200 CX microscope. A through focus series of [110] axial lattice images was taken at 200,keV, using a pointed LaB6 filament and an objective aperture of radius 0.64Å-1.Fig. 1(a) shows twoend-on γ' plates about 200Å thick and lying on {111} planes as evident from the diffraction pattern in Fig. 1(b).
Segregation and domain structure in rapidly solidified Ni3Al
Authors: Horton J. A. , Koch C. C. , Liu C. T. 
Published: June 2020

Rapid solidification processing (RSP) in conjunction with microalloying is being used to enhance the ductility of Ni3Al. Boron which strengthens grain boundaries was added for significant improvement in ductility of Ni3Al. Specimens of Ni3Al (24 at. % Al) with additions of 0, 500, and 1000 wt ppm boron were splat-cooled in an arc-hammer apparatus. The specimens without boron were brittle while specimens with boron were ductile for all but the fastest quench rates. Microstructural characterization was performed with a Philips EM400T/FEG and JEM 120CX transmission electron microscopes.Antiphase boundaries (APB) are not observed in Ni3A1 alloys fabricated from cast ingots, but are present following RSP. The average domain sizes were 50 and 80 nm for specimens with and without boron, respectively, but were independent of solidification rate. Near the surface of the splats the domain size was approximately the same as in the center even though the grain size was much smaller. Regions of small domains which were always in the center of the grains were surrounded by larger domains.
Calculations of Z-Contrast for organic and biological specimens
Authors: Egerton R.F. , Misra M. 
Published: June 2020

So-called "atomic-number contrast" is obtained in STEM by displaying a ratio signal formed by dividing the annular-dark-field signal Iadby the inelastic component Iiof the bright-field intensity (isolated by means of an electron spectrometer; see Fig. 1). Originally used for single-atom imaging, the technique has more recently been applied to polymer samples and biological tissue.We report here estimates of the ratio signal from organic specimens, based on the following assumptions:(1) That the specimen is amorphous and that phase contrast may be neglected for the electron-optical conditions and specimen features being considered; (2) That atomic cross sections may be used to estimate the amount of elastic and inelastic scattering. Modern calculations differ from simple Lenz theory in predicting that the cross section is not a smoothly-increasing function of atomic number (see Fig. 2), particularly for the 1ighter elements. (3) We assume a slightly idealized detection system in which all elastically scattered electrons contribute to Iad, while all electrons which have been inelastically (but not elastically) scattered contribute to Ii.
Pd/ MgO reaction study
Authors: Warble C.E. , Cowley J.M. 
Published: June 2020

It has been known for some years that, under appropriate conditions, palladium will interact with magnesium oxide at temperatures well below the melting point of the metal. Several studies based upon bright field transmission electron microscopy (BFTEM) have already been carried out. This work established the following main points about the reaction.The phenomenon observed is a reaction.The reacting phase exhibits characteristics typical of liquid substances.The reaction proceeds by means of an amorphous phase at a temperature lower than the melting point of either material.The ceramic remains virtually strain-free during the reaction as well as after normal or quench-rate cooling.The reaction phase maintains an amorphous structure when cooled slowly or quenched.X-ray microprobe analysis on the reaction zone indicated that at least 95% of the cations were palladium.This paper discusses recent findings from further studies made using the VG-HB5 scanning transmission electron microscope (STEM), and the JEOL 200CX (BFTEM).
Quantitative assessment of radiation damage in protein crystal
Authors: Chiu Wah , Jeng T.W. 
Published: June 2020

Radiation damage is a well known phenomenon in the electron microscopic study of thin crystals of macromolecules. A quantitative description of radiation damage is essential for at least 3 reasons: (i) it can provide numerical parameters for evaluating the extent of specimen damage at various experimental conditions, (ii) it can provide an indicator as to the maximum number of diffraction patterns and images obtainable from a single crystal before the specimen is significantly altered, and (iii) since the specimen is being altered after the initial hit by the electrons, schemes are needed to make correction of the data prior to its use for structural calculation. This paper primarily deals with the methodology used to evaluate the quantitative aspects of radiation damage of thin protein crystals. The example of crystal used in this study was crotoxin complex embedded in glucose.A standard set of data recorded in a radiation damage study is a series of electron diffraction patterns from a single crystal. The important experimental variables include the exposure rate, the exposure time and the accumulating exposure between successive patterns.
The limits of microanalytical information as set by electron-beam damage
Authors: Isaacson M. S. 
Published: June 2020

The task given to me was try to address how radiation damage limits the information that we can extract from a sample in the electron microscope and to somehow i11ucidate what is known about the mechanism of the damage itself. I am afraid that the tasks are more formidable than I first realized, and I shall not (in this paper) be able to come to definitive conclusions. However, the attempt will be made to tie together various observations and bits of knowledge from different areas which may not be familiar to the general practitioner of electron microscopy.The area of radiation damage in electron microscopy tends to be somewhat descriptive. After all, it is really not the main item on the microscopist's agenda, but rather happens to be the unfortunate consequence of the act of viewing the sample. One can liken the electron microscopist to someone who is ill. It is not too important why or how the illness occurred, but rather, how to remedy it.
Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM
Authors: McConville Richard L. 
Published: June 2020

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.
Structure of the insect flight muscle Z disk
Authors: J.F. Deatherage , B. Luke , G.M. Sainsbury , B. Bullard 
Published: June 2020

The Z disk of striated muscle is a regular planar network of connections linking two sets of oppositely directed thin filaments from adjacent sarcomeres. Ashurst has inspected images of oblique thin sections through insect Z disks, and proposed that parallel overlapping filaments in the Z disk are arranged in hexagonal bundles of six, which alternating filaments enter from opposite sarcomeres. We have now analyzed images of thin-sectioned and negatively-stained Z disks using Fourier filtering and crystallographic image processing methods. Our findings confirm the basic model of Ashurst for the arrangement of filaments inside the Z disk. By evaluating contour maps of crystallographically averaged images at higher resolution, we have obtained additional information about the positions of the filaments and the connections linking them.We have examined Z disks of flight muscles of three orders of insect, Diptera (blowfly), Hemiptera (Lethocerus) and Hymenoptera (bumble and carpenter bee). Thin sections from Lethocerus whole muscle fibers and negatively-stained isolated Z disks from bumble bee were examined in most detail. The connectivities of thin filaments of one sarcomere through the Z disk to the adjacent sarcomere were traced on Fourier-filtered images of oblique thin-sections. These cut the myofibril at an angle off perpendicular, intersecting it on one side of the Z disk, passing through it, and exiting on the other side. The filaments in the Z disk lattice, and the connections between them, were examined on crystallographically averaged images of transverse sections through the Z disk, and of isolated, negatively-stained Z disks.The insect flight muscle Z disk is arranged on a hexagonal lattice with unit cell dimensions of about 465Å. Images of both thin- sectioned and negatively-stained Z disks diffract optically to the fifth or sixth order (about 75Å resolution). The projection symmetry of the Z disk is p3m. Contour maps of crystallographically averaged images of thin- sectioned and isolated Z disks show prominent features arranged in roughly hexagonal bundles of six. These features correspond to extensions of the thin filaments into the Z disk, three from each of the opposing sarcomeres. By analysis of oblique sections we have confirmed that the opposed thin filament lattices of the two sarcomeres meet in three-fold to six-fold register (that is, a third of a unit cell out of register along both crystallographic axes). The relative strengths of features in these images are consistent with long overlap of filaments from opposite sarcomeres inside the Z disk.
Development of apical pits in chloride cells of the gills of Pimephales promelas after chronic exposure to acid water
Authors: Leino Richard L. , Anderson Jon G. , McCormick J. Howard 
Published: June 2020

Groups of 12 fathead minnows were exposed for 129 days to Lake Superior water acidified (pH 5.0, 5.5, 6.0 or 6.5) with reagent grade H2SO4 by means of a multichannel toxicant system for flow-through bioassays. Untreated water (pH 7.5) had the following properties: hardness 45.3 ± 0.3 (95% confidence interval) mg/1 as CaCO3; alkalinity 42.6 ± 0.2 mg/1; Cl- 0.03 meq/1; Na+ 0.05 meq/1; K+ 0.01 meq/1; Ca2+ 0.68 meq/1; Mg2+ 0.26 meq/1; dissolved O2 5.8 ± 0.3 mg/1; free CO2 3.2 ± 0.4 mg/1; T= 24.3 ± 0.1°C. The 1st, 2nd and 3rd gills were subsequently processed for LM (methacrylate), TEM and SEM respectively.Three changes involving chloride cells were correlated with increasing acidity: 1) the appearance of apical pits (figs. 2,5 as compared to figs. 1, 3,4) in chloride cells (about 22% of the chloride cells had pits at pH 5.0); 2) increases in their numbers and 3) increases in the % of these cells in the epithelium of the secondary lamellae.
A scanning electron microscopic study of the alimentary canal in the grass lizard
Authors: Ooi E. C. V. , Chan C. W. 
Published: June 2020

The histology of the reptilian alimentary tract has been described in numerous light microscopic studies. However, no information on surface morphology is available for any species of reptiles. In the present communication, the alimentary canal of the grass lizard, Takydromus sexlineatus, is investigated by means of light and scanning electron microscopy.Various portions of the alimentary canal were dissected and removed rapidly. While immersed in cacodylate buffer, the inner lining of each portion was exposed and rinsed. The tissues were then fixed in 2% glutaraldehyde in cacodylate buffer, dehydrated in graded ethanol series, and critical point dried with carbon dioxide. After coating with gold, the specimens were examined on a JOEL JSM-35 operated at 35 KV. Tissues for light microscopy were processed routinely.
Ultrastructure of Russell's bodies in plasma cells of normal ovine hemal lymph nodes
Authors: Al-Bagdadi F. , Seger C. 
Published: June 2020

Hemal lymph nodes occur in a wide range of animals including ruminants, primates, horses and man. It is generally believed that they are separate lymphatic organs capable of performing hemopoietic and immunologic functions. The plasma cells are the main source of antibody synthesis. They are formed when antigens enter B-lymphocytes and induce their transformation into plasma cells. The plasma cells release immunoglobulins (Russell's bodies) directly into adjacent tissues.Different reports expressed varied opinions on the significance and the fate of Russell bodies in plasma cells. Some of the opinions are that Russell bodies appear in pathological conditions. it is believed that the appearance of Russell's bodies in plasma cells is a cellular defect. They are also considered heterogenous in nature. This report shows that Russell bodies have appeared in plasma cell of healthy ovine hemal lymph nodes.Hemal lymph nodes were collected from different regions near the viscera of five native Louisiana sheep. Small slices of the nodes were fixed in 3% gluteraldehyde in phosphate buffer (pH 7.4), postfixed in 1% OSO4 and embedded in epon. Ultra-thin sections were examined with a Zeiss 10 electron microscope.
The blood/air barrier as defined by horseradish peroxidase in the normal guinea pig lung
Authors: Ford J.O. , Dodson R.F. , Williams M.G. , Hurst G.A. 
Published: June 2020

The blood/air barrier is established by the combined influences of the capillary endothelial cells, the interstitial space and the alveolar epithelial cells. The present study examined the morphological basis of the blood/air barrier as defined by a tracer model. This barrier is altered in many pathological states as reflected by the presence of exudate and/or increased cellularity in the alveoli. This investigation provides comparative data which can be used to assess early changes and potential recovery of barrier integrity whether response is caused by internal physiological alterations or external toxic stimuli.A small molecular weight protein, horseradish peroxidase (HRP), was used in the guinea pig model to ultrastructurally show the existence of a barrier at the level of the alveolar epithelium. Adult animals were injected intravenously with 300 mg/kg of the tracer in a small volume of saline (4% of total blood volume) and sacrificed at varying intervals by either intratracheal filling or right-ventricular perfusion with a fixative consisting of 3% glutaraldehyde buffered with 0.1M phosphate.
Spherulitic crystal growth in the prodissoconch larval of Crassostrea virginica
Authors: Cocks George G. , Leibovitz Louis , Lee DoSuk D. 
Published: June 2020

Our understanding of the structure and the formation of inorganic minerals in the bivalve shells has been considerably advanced by the use of electron microscope. However, very little is known about the ultrastructure of valves in the larval stage of the oysters. The present study examines the developmental changes which occur between the time of conception to the early stages of Dissoconch in the Crassostrea virginica(Gmelin), focusing on the initial deposition of inorganic crystals by the oysters.The spawning was induced by elevating the temperature of the seawater where the adult oysters were conditioned. The eggs and sperm were collected separately, then immediately mixed for the fertilizations to occur. Fertilized animals were kept in the incubator where various stages of development were stopped and observed. The detailed analysis of the early stages of growth showed that CaCO3 crystals(aragonite), with orthorhombic crystal structure, are deposited as early as gastrula stage(Figuresla-b). The next stage in development, the prodissoconch, revealed that the crystal orientation is in the form of spherulites.
Freeze fracture imaging and computer simulation of liposome structure: Membrane geometry and defects
Authors: Zasadzinski Joseph A. 
Published: June 2020

At low weight fractions, many surfactant and biological amphiphiles form dispersions of lamellar liquid crystalline liposomes in water. Amphiphile molecules tend to align themselves in parallel bilayers which are free to bend. Bilayers must form closed surfaces to separate hydrophobic and hydrophilic domains completely. Continuum theory of liquid crystals requires that the constant spacing of bilayer surfaces be maintained except at singularities of no more than line extent. Maxwell demonstrated that only two types of closed surfaces can satisfy this constraint: concentric spheres and Dupin cyclides. Dupin cyclides (Figure 1) are parallel closed surfaces which have a conjugate ellipse (r1) and hyperbola (r2) as singularities in the bilayer spacing. Any straight line drawn from a point on the ellipse to a point on the hyperbola is normal to every surface it intersects (broken lines in Figure 1). A simple example, and limiting case, is a family of concentric tori (Figure 1b).To distinguish between the allowable arrangements, freeze fracture TEM micrographs of representative biological (L-α phosphotidylcholine: L-α PC) and surfactant (sodium heptylnonyl benzenesulfonate: SHBS)liposomes are compared to mathematically derived sections of Dupin cyclides and concentric spheres.
Effect of permeabilization of tight junctions on morphology of 3-cell intersection
Authors: Polak-Charcon Sylvie , Pitelka Dorothy R. 
Published: June 2020

Tight junctions (TJ) at 3-cell intersections (3Cl) appear in freeze-fracture replicas as channels limited by 2 vertical strands in one cell's membrane, each representing the line of fusion with one of the other cells. Recent observations show in mammary cells exposed to a calcium chelator, retraction of microvilli from cell borders, starting at the 3Cl. Ca2+ depletion is also known to reduce transepithelial resistance. These observations led us to inquire whether 3Cl might be the sites most vulnerable to agents that increase junction permeability. We used the rat mammary adenocarcinoma cell line LA7 (from R. Dulbecco) to ask this question.LA7 monolayers were treated with reagents known to affect transepithelial permeability: Ca2− and Mg2+-free phosphate-buffered saline (PBS-CMF), the Ca2+ chelator EGTA (0.025%), colchicine (0.1mM), cytochalasin B (10 μg/ml), procaine (1 - 10 μg/ml), kinetin (0.4 μM), phalloidin (10-50 μM). Confluent LA7 on impermeable substrates form many domes (Fig I) as fluid transported basally is trapped between the monolayer and the plastic. Their presence is proof of TJ integrity and was the criterion used in this study. Functional effects of the treatments were measured by maintenance or change in dome numbers and morphological effects were followed by freezefracturing.
Structure of bacteriophage lambda receptor protein
Authors: Jap Bing K. , Glaeser Robert M. 
Published: June 2020

Receptor protein for phage lambda (LamB protein) is a major outer membrane protein in maltose-induced E. coli cells. This protein (M.W. ∼48,000) facilitates the passage of maltose, maltooligosaccharides and other sugars across the outer membrane. LamB and matrix proteins (OmpC and OmpF) form permeability channels and share a number of unique physical and biochemical properties. Yamada et al. have carried out experiments reconstituting LamB proteins with 1ipopolysaccharides, 1ipopolysaccharide derivatives, fatty acids, and phospholipid. The reconstituted specimens show first order hexagonal lattice with lattice constants that vary with the reconstitution component.We have reconstituted LamB protein with phosphatidylcholine from soybean. The reconstituted LamB membrane patches have dimensions from 0.2 μm to 3 μm in diameter with typical size of about 0.4 μm. LamB specimens negatively stained with phosphotungstic acid is shown in Figure l together with its optical diffraction pattern. The optical diffraction pattern shows a hexagonal lattice with lattice constant ∼7.2 nm. The diffraction intensities extend to a resolution of ∼2.4 nm.