bluuebunny/crossref_metadata_2025 huggingface dataset:
Setting of composite hydroxylapatite/plaster implants with blood for bone reconstruction
Authors: Hanker J. S. , Randolph D. A. , Giammara B. L. , Yates P. E. , Lange R. G.
Published: June 2020

Nonresorbable sintered hydroxylapatite (HA) particles are widely used for alveolar ridge augmentation in edentulous patients to support dentures or for filling infrabony defects due to bone resorption in progressive periodontal disease. these particles tend to scatter when implanted with water or saline as the vehicle. studies in our laboratory of different binders to prevent particle scatter during implantation suggested the utility of plaster of paris for this purpose. In most operative procedures the ha/plaster mixtures moistened with water or saline set and harden adequately, especially when a small amount of potassium sulfate has been added to the plaster component to accelerate setting. when the implantation site is bloody or has an excess of tissue fluids, setting of the mixture is considerably slowed if, indeed, the plaster is not actually washed away.
The blister of porphyria cutanea tarda: A Scanning and Transmission Electron Microscopic study
Authors: Burmeister Veronika , Swaminathan R.
Published: June 2020

Porphyria cutanea tarda (PCT) is a disorder of porphyrin metabolism which occurs most often during middle age. The disease is characterized by excessive production of uroporphyrin which causes photosensitivity and skin eruptions on hands and arms, due to minor trauma and exposure to sunlight. The pathology of the blister is well known, being subepidermal with epidermodermal separation, it is not always absolutely clear, whether the basal lamina is attached to the epidermis or the dermis. The purpose of our investigation was to study the attachment of the basement membrane in the blister by comparing scanning with transmission electron microscopy.
Ultrastructure of uterine glands of mares infused with povidone iodine solution
Authors: Al-Bagdadi F. , Richardson G. R. , McCoy D. , Braun W. , Archbald L. , Olsen L. , Thompson D. , Titkemeyer C.
Published: June 2020

Infertility in the mare is of major concern in the equine breeding industry. It has been stated that intrauterine infusion of certain solutions will produce an inflammatory reaction in the endometrium. The response of the uterine glands to intrauterine infusion has not been examined. Other investigators have described the epithelial changes of the uterus. This study describes the fine structure of the uterine gland cells and their response to povidone iodine infusion with the emphasis on the mast cell occurrence in the uterine glands and the lamina propria of the uterus
Structural and functional renal alterations in five-sixth nephrectomized rats on unrestricted diet
Authors: Stachura I. , Pardo M. , Costello J. , Landwehr D.M.
Published: June 2020

Under experimental conditions severe reduction of renal mass results in the hyperfiltration of the remaining nephrons leading to a progressive renal insufficiency. Similar changes are observed in patients with various renal disorders associated with a loss of the functioning nephrons. The progression of renal damage is accelerated by high protein and phosphate intake, and may be modified by the dietary restrictions.

We studied 50 five-sixth nephrectarrized male Wistar rats on a standard diet (Rodent Laboratory Chow 5001 Ralston Purina Co., Richmond, Indiana; containing 23.4% protein) over a 20 week period.
Effects of soman on rat blood-brain barrier
Authors: Petrali John P. , Maxwell Donald M. , Mills Kenneth R.
Published: June 2020

Soman, an organophosphorous irreversible inhibitor of acetylcholinesterase was studied for its effect on the rat blood- brain barrier (BBB) during the first 24 hours of intoxication. Young adult male Sprague-Dawley rats injected with Evans blue dye (1. V. 2ml/kg of a 2% solution) and surviving a subsequent single convulsive dose of Soman (0.9 LD50) presented focal and diffuse penetration of dye in areas of brain normally considered protected by the BBB. Invasion was widest during the the first hour, when signs of excitation, respiratory distress, and convulsions peaked and was absent at 24 hours. During this time period, acetylcholinesterase inhibition, as measured by enzyme assay, persisted in brain and blood at 10 percent and 6 percent of control values respectively. Brains of nonconvulsing animals and animals pretreated with sodium pentobarbital (45mg/kg) or with diazepam (10 mg/kg) were free of extravasated dye.
The effect of 2,3,4 trimethylpentane on the ultrastructure of kidneys from normal versus castrated male rats
Authors: Mattie D.R. , Chase M.R. , Hobson D.W.
Published: June 2020

Studies in this laboratory have shown that exposure to vapors of hydrocarbon fuels such as JP-5, JP-4 and diesel fuel-marine produce kidney lesions, including protein deposition, proximal tubular cell degeneration and intratubular casts in male rats, but not in female rats. 2,2,4 trimethylpentane (TMP) is a principal component of gasoline. Both 2,2,4 TMP and its more potent isomer, 2,3,4 TMP, in gavage studies produced Kidney lesions identical to those seen in acute fuel inhalation exposures. Only male rats produce a testosterone dependent alpha 2u globulin, a low molecular weight plasma protein. Since this protein appears to be involved in the pathogenesis of the kidney lesion, castrated rats were also exposed to 2,3,4 TMP and examined by transmission electron microscopy.
Ultrastructural changes in the mouse liver induced by hepatotoxin from the freshwater cyanobacterium Microcystis aeruginosa
Authors: Dabholkar A.S. , Carmichael W.W.
Published: June 2020

The colonial cyanobacterium (Blue-green alga) Microcystis aeruginosa can form heavy growths or waterblooms of toxic cells in drinking and recreational water supplies. Intraperitoneal (i.p.) administration of toxic cells (LD50 i.p. mouse = 40 mg/kg) or purified toxin (50 μg/kg) causes death in laboratory rats or mice within 1-3 h. The most acutely affected organ is the liver which shows severe hemorrhagic necrosis. Previous liver ultrastructure studies have shown damaged endothelium, swollen mitochondria and fragmented membranes. Our time-course electron microscopic study is focused on the time sequence of intracellular changes in the hepatocytes of the mouse caused by lethal and sublethal doses of the toxin.
The electron microscope as a diagnostic tool for skeletal muscle disease
Authors: Bilbao J. E. , Turner R. A. , King R. T. , Stinson J. C.
Published: June 2020

Time and experience has proven that striated muscle has only a limited number of reaction patterns. However, the electron microscopic examination has given information about the ultrastructural reaction of muscle fibers and about the pathologic physiology of diseased muscle. Although specific abnormalities are not useful when present individually. When present in a combination they may be diagnostic.
High-resolution TEM of thin-film β-SiC interfaces
Authors: Nutt S.R. , Smith David J.
Published: June 2020

Silicon carbide is a large band gap semiconductor under development for microelectronic device applications involving high temperatures, high frequencies, and high power. Single crystal thin films of high purity β-SiC can be fabricated by epitaxial CVD onto a <100> silicon wafer substrate. Epitaxial growth is achieved by a two-step process in which the surface of the silicon substrate is first converted to SiC by heating in the presence of hydrocarbon vapors, Despite the large lattice mismatch, this process results in an epitaxial film of β-SiC 10nm in thickness, upon which the SiC crystal is then chemically vapor deposited. Relatively thick (20 microns) crack-free films of SiC can thus be fabricated, although significant problems remain, such as lattice constant and thermal expansivity mismatches, and metallization and passivation of the surface. These reasons have provided the motivation for a detailed examination of interface structures in β-SiC thin films using HRTEM imaging of cross-sectional specimens.
Shock consolidation of Ni-Ti alloy powder
Authors: Thadhani Naresh N. , Vreeland Thad , Ahrens Thomas J.
Published: June 2020

A spherically-shaped, microcrystalline Ni-Ti alloy powder having fairly nonhomogeneous particle size distribution and chemical composition was consolidated with shock input energy of 316 kJ/kg. In the process of consolidation, shock energy is preferentially input at particle surfaces, resulting in melting of near-surface material and interparticle welding. The Ni-Ti powder particles were 2-60 μm in diameter (Fig. 1). About 30-40% of the powder particles were Ni-65wt% and balance were Ni-45wt%Ti (estimated by EMPA).

Upon shock compaction, the two phase Ni-Ti powder particles were bonded together by the interparticle melt which rapidly solidified, usually to amorphous material. Fig. 2 is an optical micrograph (in plane of shock) of the consolidated Ni-Ti alloy powder, showing the particles with different etching contrast.
Precursors to crystallization in amorphous CdGeAs2
Authors: Speyer R.F. , Kriven W.M. , Risbud S.H.
Published: June 2020

A myriad of crystalline microstructures may be obtained by minute variations in thermal treatment during the devitrification of CdGeAs2 from the glass. Differential Scanning Calorimetry (DSC) studies show that the single crystallization exotherm observed under moderate heating conditions, splits into two superimposed exotherms (a moderately energetic one followed by a substantially energetic one) at very slow heating rates, as shown in Figure 1.

It is believed that the first DSC exotherm represents the nucleation and partial growth of a non-stoichiometric. crystalline precursor phase. X-ray diffraction studies of samples sequentially quenched along the DSC exotherm indicated, to reasonable confidence, that the precursor phase was pure germanium, and with absolute confidence that the larger exotherm represents the formation of CdGeAs2 adopting the chalcopyrite structure. The TEM. STEM, and EDS studies described herein substantiate our elucidation of the precursor phase.
Interface structures in polycrystalline ceramic materials
Authors: Morrissey K. J.
Published: June 2020

Grain boundaries and interfaces play an important role in determining both physical and mechanical properties of polycrystalline materials. To understand how the structure of interfaces can be controlled to optimize properties, it is necessary to understand and be able to predict their crystal chemistry. Transmission electron microscopy (TEM), analytical electron microscopy (AEM,), and high resolution electron microscopy (HREM) are essential tools for the characterization of the different types of interfaces which exist in ceramic systems. The purpose of this paper is to illustrate some specific areas in which understanding interface structure is important. Interfaces in sintered bodies, materials produced through phase transformation and electronic packaging are discussed.
Structure determination of γ-Fe2O3 particles
Authors: Ho Huei-Min , Thomas Gareth
Published: June 2020

γ-Fe2O3 particles used in magnetic recording media are commonly prepared via the conversion of αFeOOH or γFe2O3 to Fe3O4, followed by oxidation of the Fe3O4 to γ-Fe2O3. Fe3O4 which has a cubic inverse spinel structure converts to γ-Fe2O3 by the removal of 8/3 Fe ions per unit cell. Although γ-Fe2O3 particles have been widely used for several decades, the structure of this material remains unresolved mainly because the techniques involved in previous studies did not have the resolution needed for localized information.
Convergent-bceam diffraction studies on lead zirconate titanate Ceramics
Authors: Dass M.L.A. , Bielicki T.A. , Thomas G. , Yamamoto T. , Okazaki K.
Published: June 2020

Lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), ceramics are ferroelectrics formed as solid solutions between ferroelectric PbTiO3 and ant iferroelectric PbZrO3. The subsolidus phase diagram is shown in figure 1. PZT transforms between the Ti-rich tetragonal (T) and the Zr-rich rhombohedral (R) phases at a composition which is nearly independent of temperature. This phenomenon is called morphotropism, and the boundary between the two phases is known as the morphotropic phase boundary (MPB). The excellent piezoelectric and dielectric properties occurring at this composition are believed to.be due to the coexistence of T and R phases, which results in easy poling (i.e. orientation of individual grain polarizations in the direction of an applied electric field). However, there is little direct proof of the coexistence of the two phases at the MPB, possibly because of the difficulty of distinguishing between them. In this investigation a CBD method was found which would successfully differentiate between the phases, and this was applied to confirm the coexistence of the two phases.
Microstructures of SiC and Si3N4 with fibrous inclusions
Authors: Tighe N. J. , Sun J. , Hu R.-M.
Published: June 2020

Particles of BN,and C are added in amounts of 1 to 40% to SiC and Si3N4 ceramics in order to improve their mechanical properties. The ceramics are then processed by sintering, hot-pressing and chemical vapor deposition techniques to produce dense products. Crack deflection at the particles can increase toughness. However the high temperature strength and toughness are determined byphase interactions in the environmental conditions used for testing. Examination of the ceramics by transmission electron microscopy has shown that the carbon and boron nitride particles have a fibrous texture. In the sintered aSiC ceramic the carbon appears as graphite fiber bundles in the triple junctions and as compact graphite particles within some grains. Examples of these inclusions are shown in Fig. 1A and B.
An investigation of ion beam and pulsed laser Ni-SiC mixed surface structures by cross-sectional TEM
Authors: More K. L.
Published: June 2020

Ion beam and pulsed laser mixing have been used as surface modification techniques in an attempt to increase the mechanical properties of sintered α-SiC. Thin Ni overlayers (50 nm - 100 nm) were evaporated onto the SiC surface and subsequently irradiated with pulses of a krypton-fluoride (KrF) excimer laser or bombarded with high energy Si+ ions. Both techniques are non-equilibrium processing methods capable of inducing unique microstructural changes at the specimen surface which, under particular processing conditions, can result in enhanced physical properties. It has been shown previously that laser annealing of Ni-coated α-SiC resulted in a fracture strength increase of ≈20%; however, the fracture strength was not changed following ion beam mixing. High resolution cross-sectional transmission electron microscopy (X-TEM) was used to characterize the extent of mixing between the Ni and the SiC following surface modification.
The characterization of rapidly solidified Al-8Fe-2Mo powder
Authors: Plummer H.K. , Donlon W.T. , Allison J.E. , Shinozaki S.
Published: June 2020

A centrifugally atomized rapidly solidified Al-8Fe-2Mo powder was characterized by Light Microscopy (LM), Scanning Electron Microscopy (SEM) and Analytical Electron Microscopy (AEM). The powder sample was studied in an as-solidified state and after annealing in 1 at. argon for 6 hr at 400°C. Further studies have characterized the consolidated bars produced by compaction and extrusion of these powders.

The 30 to 150 μm powders are spherical as seen in the SEM (Fig.1) with small (5 to 15 μm) satellite powders sometimes attached in external (A,B Fig.1) and internal (A Fig.2C) locations. A comparison of powders (epoxy mounted and polished) by both the LM (Fig. 2A) and the SEM (Figs. 2B and 2C) reveals a two component microstructure with occasional voids.
Microstructural evolution in mechanically alloyed Nb-25 at.% Ge
Authors: Kenik E.A. , Bayuzick R.B. , Kim M.S. , Koch C.C.
Published: June 2020

Mechanical alloying involves the mixing and milling of compositionally different powders in a high energy ball mill. During this process, powder particles cold-weld to others upon impact and subsequently fracture. The coldwelding (which may involve local melting or at least elevated temperature just after impact) produces a zone of intermediate composition. As a result of the rapid heating and cooling of the interdiffused zone and the large amount of strain energy stored in the powder, mechanical alloying may produce metastable materials. The current study involves the microstructural evolution in mechanically alloyed elemental niobium and germanium powder blends.
The effect of metallurgical factors on the quality of fine multifilamentary NbTi superconducting wires
Authors: Sabatini R. L. , Suenaga M. , Garber M.
Published: June 2020

Metallurgical factors during the fabrication process have a large influence on the quality of composite NbTi multifilamentary superconducting wire. The observed critical current density, Jc, is sensitive to microstructure on the scale of the fluxoid-defect interaction, and also to macroscopic variations in filament diameter.

Earlier work at the University of Wisconsin, Lawrence Berkeley Laboratory, Wah Chang, and Intermagnetics General Corp. was concentrated on improving the intrinsic Jc for wires with a relatively large filament diameter (~20 μm). By improving homogeneity of the NbTi alloy and by optimizing the drawing-anneal treatment schedule, wires with Jc ∼3000 A/mm2 were produced.
The effect of deformation on the banded martensite microstructure in a dilute uranium alloy
Authors: Speer John G. , Edmonds David V.
Published: June 2020

Experimental observations of shape-memory behavior and related phenomena have been reported for uranium alloy systems. Vandermeer, et al. published the first evidence of shape-memory in uranium alloys using a U-14 at.% Nb alloy. On heating the deformed martensitic phase, complete shape recovery was observed for tensile strains up to 7%. The work hardening rate was very low in the region of recoverable strain, and Vandermeer suggested that the shapememory behavior in these alloys results from the ability of the banded martensite to deform by the movement of glissile interfaces. The present investigation was undertaken in order to examine the effect of deformation on the microstructure of a banded uranium martensite, and to provide a better understanding of the underlying mechanisms responsible for the mechanical behavior of these alloys.
AEM analysis of solidification catalysts in atomized Fe-Ni
Authors: Libera Matthew R.
Published: June 2020

The liquid droplets produced by atomization processes are believed to undergo substantial supercooling during solidification, because the catalytic heterogeneities, for statistical reasons, tend to be isolated in the larger droplets. This supercooling can lead to the nucleation of metastable phases. As part of a study on the effect of liquid supercooling on nonequilibrium solidification, three binary Fe-Ni alloys have been produced by conventional argon atomization (Fe-20Ni, Fe-30Ni, and Fe-40Ni). The primary variables in these experiments are: i) the alloy composition; and ii) the powder particle diameter (inversely proportional to supercooling). Of particular interest in this system is the competitive nucleation kinetics between the stable fee and metastable bec phases. Bcc is expected to nucleate preferentially with decreasing %Ni and decreasing particle diameter.
Modern TEM systems architecture
Authors: Gross U. , Hagemann P.
Published: June 2020

By addition of analytical equipment, scanning transmission accessories and data processing equipment the basic transmission electron microscope (TEM) has evolved into a comprehensive information gathering system. This extension has led to increased complexity of the instrument as compared with the straightforward imaging microscope, since in general new information capacity has required the addition of new control hardware. The increased operational complexity is reflected in a proliferation of knobs and buttons.

In the conventional electron microscope design the operating panel of the instrument has distinct control elements to alter optical conditions of the microscope column in different modes. As a consequence a multiplicity of control functions has been inevitable. Examples of this are the three pairs of focus and magnification controls needed for TEM imaging, diffraction patterns, and STEM images.
Low-voltage SEM update
Authors: Pawley J.B. , Scala W.R.
Published: June 2020

The advantages of operating an SEM at low beam voltage (Vo) are now widely recognized and significant progress has been made in overcoming the practical limitations to high resolution operation with Vo = 1-2 kV. A Symposium on Low Voltage SEM (LVSEM) was held at the 1984 EMSA meeting and several of the papers presented there were later collected for a special issue of the Journal of Microscopy. The purpose of this contribution is to outline three developments in instrumentation for LVSEM that have recently appeared. These include: 1) The new pole-pieces on the upper stage of the ISI DS-130c which permit it to produce very low aberration coefficients with low energy beams. 2) The replacement of the final lens of the Hitachi S-800, field emission SEM with an immersion lens to create the new S-900; 3) The development of the micro-lens for mounting in the chamber on a conventional’ SEM to produce both low aberration coefficients and a favorable geometry for signal collection.
Low-voltage Scanning Electron Microscopy of polymers
Authors: Vaz O. W. , Krause S. J.
Published: June 2020

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. These problems may be avoided by imaging polymer samples at a “crossover point”, which is located at low accelerating voltages (0.1 to 2.0 keV), where the number of electrons impinging on the sample are equal to the number of outgoing electrons emerging from the sample. This condition permits the polymer surface to remain electrically neutral and prevents image distortion due to “charging” effects. In this research we have examined Teflon (polytetrafluorethylene) samples and studied the effects of accelerating voltage and sample tilting on charging phenomena. We have also determined the approximate position of the “crossover point”.
Observation of liquid transport in the ESEM
Authors: Danilatos G.D. , Brancik J.V.
Published: June 2020

The environmental SEM (ESEM) allows the observation of liquid and liquid/solid systems in a controlled gaseous environment. In order to study the wetting properties of a wool fiber, or to understand various stages of wool scouring, a system has been devised which allows the transfer of microdroplets onto the specimen surface. A description of the microinjector device together with dynamic observations of liquid transport recorded on video cassette are reported here.

Fig. 1 shows a descriptive diagram of the principle employed to transfer liquids from ambient pressure (about 1000 mbar) into the specimen chamber at hypobaric pressure (about 25 mbar). A small cavity (L) is open to the outside space via two tubes M (with 1 mm inside diameter) so that this cavity can be filled or emptied freely and quickly with a given liquid from the outside.
X-ray absorption correction using the bremsstrahlung shape
Authors: Garratt-Reed A. J.
Published: June 2020

The Bremsstrahlung background, present in every electron-induced x-ray spectrum, is affected by absorption in the sample in the path to the x-ray detector in exactly the same way as the characteristic x-rays. In principle, therefore, the Bremmstrahlung x-rays could provide a means of correcting a spectrum for self-absorption effects. Craven and Adam have examined this possibility, and have concluded that it may indeed have value.
Transmission electron microscopy of semiconductor devices
Authors: Brown J. M.
Published: June 2020

The search for further miniaturization in the semiconductor industry has resulted in the reduction in the dimensions of devices to a size which can no longer be effectively seen by the conventional methods of light microscopy. The use of both transmission and scanning electron microscopy in the field of silicon device characterization has now become an essential ingredient of the design and manufacture of new technologies. It is often the only way in which a device designer can know for certain whether the manufacturing process is producing the required structure. Cross-sectional TEM has therefore become an integral part of both quality control and development.

One of the most important areas which resulted in the increased importance of TEM in the semiconductor device field was the development of sample preparation techniques which enable cross-sections through layers of widely differing compositions that are found in the devices structures.
Analysis of epitaxial CoSi2/Si and Si/CoSi2/Si heterostructures
Authors: Lewis N. , Hall E. L. , Hunt B. D. , Schowalter L. J.
Published: June 2020

The formation of thin epitaxial metal silicide layers on Si and Si/metal silicide/Si heterostructures has received considerable attention recently for applications as ohmic contacts, permeable and metal base transistors and 3-D integrated circuits. Cobalt disilioide (CoSi2) is promising for these applications because its cubic fluorite structure is similar to that of Si. In addition, the lattice parameters of CoSi2 and Si are reasonably close (-1.2% mismatch at room temperature) making this system attractive for epitaxial growth. The quality of the epitaxial layers is particularly important for device applications. In this paper the microstructures of several CoSi2/Si and Si/CoSi2/Si specimens were investigated using transmission electron microscopy. Planar and cross-sectional samples were prepared. The planar specimens were first mechanically ground from the Si substrate side and then ion-milled in argon.
Microstructure of buried nitride films in silicon formed by implanted nitrogen
Authors: Datye A. K. , Tsao S. S. , Myers D. R.
Published: June 2020

High fluence ion implantation of nitrogen ions in silicon is currently of great interest in the formation of silicon on insulator (SOI) structures. After ion implantation, the single crystal silicon water usually exhibits a highly defective surface layer followed by an amorphous layer corresponding to the peak of the nitrogen implant profile. Annealing the sample at ∽ 1200 C yields a buried layer of silicon nitride underneath a top layer of single crystal silicon. The Quality of the single crystal silicon, buried nitride and the silicon/silicon nitride interface is of paramount importance from the standpoint of device design. We have used high resolution cross section TEM to examine the Si/nitride interface and the buried nitride layer.
Mono-Atomic Tips and Scanning Tunneling Microscopy
Authors: Fink H.-W.
Published: June 2020

The power of the Scanning Tunneling Microscope (STM) to resolve the detailed structure of solid surfaces is based on the strong distance dependence of the tunnel current, while the tip is scanned over the surface to be investigated.

In the first part of the paper, the basic principles of operation of the STM are to be reviewed, and examples of the information that can be obtained today are presented. From this, it will be evident that knowledge of the atomic arrangement of the tip is important in order to separate tunnel-current changes related to the tip from those owing to the structure of interest, namely, the sample surface.
Limits of the STEM
Authors: Crewe Albert V.
Published: June 2020

I suppose that there will be cynics in the audience who believe that the very title of this talk is a non-sequitor - that STEMs are inherently and severely limited. They are, of course, wrong. Nevertheless, it is apparent that the belief is widespread since there are so few STEMs in everyday use. For this reason it is important to address both issues, the physical limitations of the STEM and the perceptual limitations of the average microscopist.

It is difficult to know where to begin because there is so much to say, but there is one word of caution which must be said at the beginning. Only about thirty or so STEMs have been built and I doubt whether anyone who has built one would claim that it was the best that could be done. Compared with the experience and engineering manpower which has gone into the CTEM, the effort on the STEM has been miniscule. We must therefore speak more about what could be done or what could have been done than about actual accomplishments.
Alignment of small Ru and Au Particles on MgO
Authors: Shastri A. G.
Published: June 2020

The alignment of small metal particles on semiconducting or insulating substrates is of considerable importance in the areas of heterogeneous catalysis and electronic materials research. Previous work has shown an epitaxial growth of 2nm Au particles on MgO smoke prepared by an indirect exposure of the oxide to evaporated Au atoms. Others reported an epitaxial growth or random orientation of An on MgO depending on whether the oxide was vacuum cleaved or air cleaved. EDS showed the presence of bimetallic clusters in supported Ru-Au/MgO catalysts prepared by coimpregnation of the oxide with aqueous precursor metal salt solutions. A μED study of two bimetallic samples having a total metal loading of 3.75 wt % (with 93 atom % Ru) and 3.37 wt % (with 14 atom % Ru) was carried out to understand the structure of small bimetallic clusters and the relative alignment of metal particles on MgO. In spite of the bulk immiscibil ity of Ru and Au, bimetallic clusters were identified by EDS in the size range of < 5 nm.
Development of an ocular hydrogel drug delivery system
Authors: Weiss E. , Zhang D. T. , Ryoo J. P. , Greer R. T.
Published: June 2020

An ocular insert to release antibiotic is being studied for use in the treatment of infectious bovine keratoconjunctivitis (IBK). of several systems investigated, the hydrogel copolymer formulation containing 90% methylmethacrylate - 10% hydroxyethyl methacrylate shows antibiotic (tylosin tartrate) release characteristics compatible with desired rates required throughout a 5-day period. Thin layer chromatography (TLC) is being used to characterize the amounts of tylosin tartrate released at different periods from two release device systems. Scanning electron microscopy (SEM) is being used to monitor surface smoothness, to insure adequate joining of device segments, and to identify the presence of microstructural defects.
Dislocation Luminescence in ZnSe
Authors: Batstone J. L. , Steeds J. W.
Published: June 2020

Thin film, high purity II-VI semiconductors such as ZnSe are attracting increasing interest as optoelectronic device materials. Recent developments in low temperature epitaxial growth techniques such as organometallic chemical vapour deposition (MOCVD) have enabled growth of single crystal films on a variety of different substrates resulting in blue emission bands at 300K. Characterization of undoped, Al-doped and In-doped MOCVD ZnSe/(100)GaAs layers grown at RSRE, Malvern has been performed using transmission electron microscopy (TEM) and cathodoluminescence (CL). Optically and electrically active stacking faults and dislocations have been observed, revealing correlations with emission bands Y at 2.60eV and S at 2.52eV. Y and S are particularly characteristic of epitaxial growth and radiative emission has been observed from individual dislocations and complex tangles of dislocations commonly found in doped ZnSe. Recent work has concentrated on obtaining an understanding of the mechanism of radiative recombination at dislocations by studying thermal activation energies and excitation dependences.
Microstructure of high-energy product Fe-Nd-B magnequench ribbons
Authors: Chen Y. L.
Published: June 2020

Melt-spun Fe-Nd-B MAGNEQUENCH® ribbons have been produced by Croat et al. with energy products in excess of 10 MG.Oe using a relatively narrow window of composition and quenching speed. The hard magnetic phase has subsequently been identified as the Nd2Fe14B compound which has a very high anisotropy field. The microstructure of the MAGNEQUENCH® ribbon which has a maximum energy product of 14.1 MG•0e was found to consist of equiaxed Nd2Fe14B grains surrounded by a very thin intergranular film. This paper presents the results of some of our earlv work on the microstructural characterization of high energy product MAGNEQUENCH® ribbons having nominal compositions of Nd13Fe82.6B4.4 and Nd15Fe79.9B5.1. The purpose of this investigation was to characterize the microstructures of various MAGNEQUENCH® ribbons for correlation with their magnetic properties.
Interphases and interfaces in BaTiO3-NaNbO3 ceramics
Authors: Xu Z. , Payne D. A.
Published: June 2020

The properties of polycrystalline ceramics are greatly influenced by the boundary conditions which exist within ceramic microstructures. This is especially so for dielectric materials, where discontinuities in periodicity and variations in chemical heterogeneity, perturb electric flux passage through ceramic microstructures. In this investigation, dielectric mixtures in the system BaTiO3-NaNbO3 were prepared by liquid-phase sintering methods. The purpose was to distribute a continuously connected minor phase (e.g., NaNbO3) within the boundary regions of BaTiO3-based ceramics. Characterization data are presented, from TEM and STEM analyses, for the grain-size dependence on niobate content; and for the spatial distribution of Nb from the interphase into the interfacial region.
Microstructural examination of modified yttria stabilized zirconia by EM analytical techniques
Authors: Davison W. W. , Buchanan R. C.
Published: June 2020

Yttria stabilized zirconia (YSZ) has become a significant technological material due to its high ionic conductivity, chemical inertness, and good mechanical properties. Temperatures on the order of 1700°C are required, however, to densify YSZ to the degree necessary for good electrical and mechanical properties. A technique for lowering the densification temperature is the addition of small amounts of material which facilitate the formation of a liquid phase at comparatively low temperatures. In this study, sintered microstructures obtained from the use of Al2O3 as a sintering aid were examined with scanning, transmission, and scanning transmission microscopy (SEM, TEM, and STEM).
Fate of sperm membrane in fertilized ova
Authors: Longo Frank J.
Published: June 2020

Measurement of the egg's electrical activity, the fertilization potential or the activation current (in voltage clamped eggs), provides a means of detecting the earliest perceivable response of the egg to the fertilizing sperm. By using the electrical physiological record as a “real time” indicator of the instant of electrical continuity between the gametes, eggs can be inseminated with sperm at lower, more physiological densities, thereby assuring that only one sperm interacts with the egg. Integrating techniques of intracellular electrophysiological recording, video-imaging, and electron microscopy, we are able to identify the fertilizing sperm precisely and correlate the status of gamete organelles with the first indication (fertilization potential/activation current) of the egg's response to the attached sperm. Hence, this integrated system provides improved temporal and spatial resolution of morphological changes at the site of gamete interaction, under a variety of experimental conditions. Using these integrated techniques, we have investigated when sperm-egg plasma membrane fusion occurs in sea urchins with respect to the onset of the egg's change in electrical activity.
Freeze-fracture cytochemistry: A goal set by Russell Steere in 1957
Authors: Severs Nicholas J
Published: June 2020

In his pioneering demonstration of the potential of freeze-etching in biological systems, Russell Steere assessed the future promise and limitations of the technique with remarkable foresight. Item 2 in his list of inherent difficulties as they then stood stated “The chemical nature of the objects seen in the replica cannot be determined”. This defined a major goal for practitioners of freeze-fracture which, for more than a decade, seemed unattainable. It was not until the introduction of the label-fracture-etch technique in the early 1970s that the mould was broken, and not until the following decade that the full scope of modern freeze-fracture cytochemistry took shape. The culmination of these developments in the 1990s now equips the researcher with a set of effective techniques for routine application in cell and membrane biology.

Freeze-fracture cytochemical techniques are all designed to provide information on the chemical nature of structural components revealed by freeze-fracture, but differ inhowthis is achieved, in preciselywhattype of information is obtained, and inwhichtypes of specimen can be studied.
Immunolocalization of phospholipids using freeze-fracture cytochemistry
Authors: Kan Frederick W.K. , Rauch Joyce
Published: June 2020

Phospholipids are found ubiquitously in all mammalian cell membranes. The fracture-label technique offers the opportunity to localize phospholipids in tissues and cells. This technique has recently been used in combination with colloidal-gold-conjugated phospholipase A2 to demonstrate the presence of phospholipids in epithelial tight junctional strands. In the present study, we show the localization of specific phospholipids in the plasma and intracellular membranes in the rat exocrine pancreatic cells using murine monoclonal anti-cardiolipin (CL) antibodies that are reactive with phosphatidylethanolamine (PE) and have lupus anticoagulant activity. These antibodies were produced from BALB/c mice immunized with either ADP-activated murine platelets or CL mixed with apolipoprotein H.

Pancreatic tissue was excised from adult male Sprague-Dawley rats under light ether anesthesia and fixed by immersion with 1% glutaraldehde in 0.1 M cacodylate buffer. The tissue was trimmed into 1-mm cubes which were then embedded in 30% bovine serum albumin in 0.01 M PBS, and cross-linked with a final concentration of 1% glutaraldehyde to form a hardened gel.
Biological applications of microscopic magnetic resonance imaging
Authors: Jacobs Russell E. , Fraser S. Earl
Published: June 2020

The ability of MRI to provide three dimensional images of thick opaque samples in a noninvasive manner has made it an extremely important clinical tool. In addition, the large number of types of contrast mechanisms in a MR experiment offer the clinician and research scientist the possibility of adapting the image contrast to fit the problem of interest. While typical resolutions employed clinically are on the order of a millimeter, the notion of using MRI at microscopic resolutions arose early in the development of this technique. Spatial information is encoded in both the frequency and phase of the nuclear magnetic resonance signal by selective application of magnetic field gradients. Spatial resolution in biological samples is typically limited by a number of physical effects as well as signal-to-noise ratio (S/N) considerations. Estimate of the theoretical limits of resolution in the MR image arising from these phenomena range from 2 to 0.5μm. The practical spatial resolution is currently determined by the S/N which is often limited by the amount of time available to actually acquire the image (i.e. the temporal resolution). For example, a reasonable S/N clinical MR image can be obtained in about 5 minutes with a voxel (volume element) size of (1mm). We are interested in voxels down to ∼1μm on a side. Because most of the proton MR signal arises from water in biological samples and water concentration is roughly constant, the S/N change in the image will be proportional to the volume change: a factor of 10−9. Of course, this is true only if all experimental parameters are the same.
Tomographic methods for detailed examination of large structures in the nervous system
Authors: Soto Gabriel E. , Young Stephen J. , Martone Maryann E. , Deerinck Thomas J. , Lamont Stephan , Carragher Bridget O. , Ellisman Mark H.
Published: June 2020

One of the limitations of electron microscopy has been the requirement for very thin samples to allow penetration of the electron beam. It is often the case that structures of interest are not contained within a single thin section. In these cases, serial sectioning techniques are required to reconstruct the object in its entirety. The use of higher voltage electron microscopes has allowed researchers to examine specimens up to fifty times thicker than those suitable for a conventional TEM. However, images from thick sections are often difficult to interpret as the electron micrograph is essentially a projection of the overlapping material within the section. The method of computerized axial tilt electron microscopic tomography offers the potential to visualize and analyze information contained in a thick section by deriving a three dimensional volume from a series of projections acquired by collecting images of the specimen at successive tilt increments about the Y axis. Unfortunately there are practical limitations to the resolution that can be obtained using this technique with very thick sections. Resolution of the tomogram increases with finer tilt sampling and an increased range of tilts but decreases with section thickness.
Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes
Authors: Cleary Ann
Published: June 2020

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study ofTradescantiastamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells ofTradescantialeaf epidermis.

The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.
Tissue printing for scanning electron microscopy and microanalysis
Authors: Reine Barbara A.
Published: June 2020

The study of plant morphology and plant cells in the scanning electron microscope is often compromised by the limitations of specimen preparation techniques. Simple natural dehydration usually results in unacceptable shrinkage and distortion of the normal surface morphology of plant cells. Chemical fixation followed by critical point drying or some substitute for critical point drying such as Peldri II or HMDS (hexamethyldisilazane) improves morphological results but still imparts artifacts, adds chemical constituents to the specimen, and requires the use of toxic chemicals, a hood, and much time.

One technique that eliminates many of these disadvantages and is even suitable for specimen preparation in the field is tissue printing. For low magnification imaging and chemical analysis its “elegant simplicity” (2) is compelling. Historically, the application of tissue printing has been in connection with optical microscopy (1,2). However, this technique works very well for low magnification SEM and associated elemental characterization of residues by x-ray microanalysis.
Immunocytochemical localization of nicotine in developing leaves of two cultivars ofNicotiana tabacum
Authors: Echlin Patrick
Published: June 2020

Improved techniques have been developed for thein situlocalization of nicotine in developing leaves ofNicotiana tabacum. Earlier studies had shown that aldehyde fixed and partially dehydrated material embedded in different hydrophillic resins at low temperatures, retained up to 50% of the nicotine but invariably at the expense of good structural preservation. Significant improvements have now been made to the methods and it is now possible to obtain excellent structural preservation with high retention of nicotine.

Tobacco plants were grown in a glasshouse maintained at 23-26°C with 16H light and were well watered and fed with a high nitrogen fertilizer. The flower heads were removed from the plants as they appeared. Samples were taken from between the main veins at a distance 10mm from the edge of the mid part of the leaf at 10, 13, 16, 20, and 22 weeks from the time of seed germination which corresponded to the Juvenile, Mature, Ripe, Senescent and Old stages of leaf development.
Intelligent computational 3-D microscopy: New results in segmentation, noise removal, cell counting, and automated neuron tracing
Authors: Roysam Badrinath , Bhattacharjya Anoop K. , Ancin Hakan , Cohen Andrew R. , Mackin Robert W. , Becker Douglas E. , Rodriguez Carlos
Published: June 2020

This paper presents a review of recent advances made by us in the broad area of intelligent computational 3-D microscopy. This research involves the development and application of automated pattern recognition, computer vision and image interpretation algorithms to problems in 3-D biological microscopy. The broad goal of this work is to develop computational tools for rapid, unsupervised, flexible, quantitative and unbiased analysis of large sets of complex 3-D images of thick biological specimens. The imaging modalities used in this work have thus far involved laser-scanning confocal microscopy (LSCM) and 3-D brightfield microscopy. The specimens of interest have been thick slices of brain tissue, large selectively-stained neurons, indocyanin green and fluorescein retinal angiograms, and duck overlapping cell clusters in cytological preparations such as Papanicolaou smears.

Image segmentation is an essential first step for most forms of analysis. This task is straightforward when the image data is isotropic, has uniform high contrast, and is free of noise.
Laser scanning confocal microscopic analysis of cytoskeletal and nuclear reorganization in liveDrosophila embryos
Authors: Theurkauf William
Published: June 2020

Cell division in eucaryotes depends on coordinated changes in nuclear and cytoskeletal components. In Drosophila melanogaster embryos, the first 13 nuclear divisions occur without cytokinesis. During the final four divisions, nuclei divide in a uniform monolayer at the surface of the embryo. These surface divisions are accompanied by dramatic changes in cortical actin and microtubule structure (Karr and Alberts, 1986), and inhibitor studies indicate that these changes are essential to orderly mitosis (Zalokar and Erk, 1976). Because the early embryo is syncytial, fluorescent probes introduced by microinjection are incorporated in structures associated with all of the nuclei in the blastoderm. In addition, the nuclei divide synchronously every 10 to 20 min. These characteristics make the syncytial blastoderm embryo an excellent system for the analysis of mitotic reorganization of both nuclear and cytoskeletal elements. However, the Drosophila embryo is a large cell, and resolution of cytoskeletal filaments and nuclear structure is hampered by out-of focus signal.