bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass Loss of Biological Molecules in the Electron Microscope
Authors: Isaacson M. , Langmore J. , Lamvik M. , Lin P. , Golladay S. , Hainfeld J. , Pullman J. , Furlong D.
Published: June 2020

Although present-day electron microscopes can resolve single atoms, resolution of biological specimens has usually been limited to 20 Å in large part by beam-induced specimen damage. Use of the STEM, which is potentially superior to the CTEM in both contrast and specimen radiation dose necessary to form an image, and development of new specimen preparation techniques may increase resolution somewhat, but the fundamental limitation of radiation damage will still remain. Therefore we have undertaken a study of the modes of radiation damage in electron microscopy with the hope that a better understanding of these processes may aid development of techniques to reduce their effect.

We present here direct measurements of the decrease of the elastic and inelastic cross sections due to electron irradiation in the STEM. These measurements cover a wide range in dose rate from less than 10-4 amps/cm2 to 300, encompassing those dose rates found in conventional as well as high resolution scanning microscopy.
Annulate Lamellae in Hindgut Epithelial Cells of Isopoda
Authors: Herold Laura , Goggins J.A. , Witkus E. R. , Vernon G. M.
Published: June 2020

In an ultra structural study of the digestive tract of the aquatic isopod, Asellus communis, and the terrestrial isopod, Armadillidium vulgare, annulate lamellae were observed in the large epithelial cells of the anterior hindgut. The isopod digestive tract consists of two pairs of hepatopancreatic lobes and a straight tube foregut and hindgut. The foregut extends from the mouth to the area of insertion of the hepatopancreas. The hindgut extends from this area of insertion to the anus.

The annulate lamellae consist of a stack of parallelly arranged membranes in the cytoplasm. In A. communis there is defonite continuity between the ends of two adjacent lamellae in the stack (Fig. 1). The number of cisternae comprising the organelle is much greater in A. vulgare than in A. communis. The pores or annulae are also much more numerous in A. vulgare (Fig. 2) than in A. communis.
Direct Measurements of Intracellular Elemental Composition Utilizing a New Approach to Freezing In Vivo
Authors: Somlyo Avril V. , Bond Meredith , Silcox John C. , Somlyo A.P.
Published: June 2020

Many biological experiments can be successfully carried out on tissues isolated under well-defined experimental conditions, but for some physiological or pharmacological studies, knowledge of the in vivo elemental composition and/or structure is essential. We have developed a method for rapid freezing of organs in situ, with a new spring-loaded, hand held, clamping device that holds two apposing melting Freon popsicles (Fig. 5). The melting Freon surfaces that contact the tissue are at the melting point of Freon 22, and these mold to the unevenness of the tissue surface. Rapidly frozen samples of liver, pancreas or mesentery were obtained by placing an anesthetized rat in a cloth sling over an environmental chamber kept at 37°C, 100% humidity (Fig. 5). A small incision is made in the abdomen, and the abdominal wall is manipulated until a lobe of liver protrudes through the incision, while taking care not to touch the surface of the organ. Immediately, the Freon clamper is activated to snap freeze the tissue.
Microstructural Evolution During Solidification of Al-Fe-Ce Powders
Authors: Chu M. G. , Rioja R. J. , Hildeman G. J. , Denzer D. K.
Published: June 2020

Al-Fe-Ce alloys produced from gas atomized powders exhibit greater strength at 150°-315°C than conventional aluminum alloys. This higher strength can be attributed to small dispersoids that form during the rapid solidification and precipitates that form after solidification and during consolidation. Understanding the powder microstructure is essential to establishing the relationship between wrought product microstructures and properties. Microstructures present in Al-8 wt% Fe-4 wt% Ce and Al-7 wt% Fe-6 wt% Ce powders (-325 mesh) are presented; in addition, a solidification sequence for atomized droplets is proposed.

Analyses include: SEM, TEM, and Chemical Analyses from thin foils via EDXS. Powder samples were compacted into wafers at 200 ksi and subsequently electropolished via the window technique.
The Deflection of Electron Reams Traversing A Crystal Face
Authors: Cowley J.M. , Kang Z.L.
Published: June 2020

A serious discrepancy exists between the experimental and theoretical results on the deflection of an electron beam passing parallel to, and just outside, the flat face of a crystal. In a previous paper we reported that for a beam of diameter about 15Å traversing the face of a small gold crystal within a distance of 20Å or less, the central spot of the diffraction pattern is seen to be displaced through angles of up to 10-2 radians. Similar observations had been made for MgO crystals. Rough agreement with the observations could be obtained by assuming the beam to be deflected by a potential field extending into the vacuum and having the form

where ϕo is the inner potential of the crystal and A, B and C are positive constants. This model for the potential field is based on the assumption of an image force modified for small x by a second order term.
A New Method For Calibrating Focusing Steps Of Electron Microscopes
Authors: Hsu Tung
Published: June 2020

Focusing steps of an electron microscope, i.e., the change of focus, Δf, corresponding to one click on any one of the focus dials must be calibrated. Two methods have been used; measuring the distance between bright field and dark field images of small crystalline particles and measuring the diameters of optical diffractograms obtained from the image of an amorphous specimen.

A new method utilizing the large depth of field in reflection electron microscopy (REM) provides a direct means of measuring the focusing steps on the micrograph. The in focus area in an REM image can be recognized as the “least grainy” part or the minimum contrast of images of steps. Using surface steps, particles, or other features as References, the shift of this in focus position due to the variation of objective lens current can be readily measured on the micrograph. This distance is then converted to f by taking account of magnification (calibrated) and the foreshortening factor (calculated from the diffraction pattern).
A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures
Authors: Burke M.G. , Miller M.K.
Published: June 2020

Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).

The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.
Comparison of the Particle Size Distribution of Alpha Quartz in Respirable Coal Mine Dust Samples With Four Reference Standards
Authors: Huggins C. W. , Johnson S. J. , Segreti J. M. , Snyder J. G.
Published: June 2020

For the past 3 years the Bureau of Mines, Avondale Research Center, has been doing extensive particle size measurements on respirable coal dust collected at surface and underground mines in the eastern United States. Respirable dust is the portion of airborne dust that penetrates the deepest portion of the lungs and is generally considered to be particles less than 10 μm in size. To monitor dust exposure, approximately 40,000 respirable dust samples are collected by inspectors annually. The quartz in these samples is determined by either infrared spectrophotometry or x-ray diffraction. Both methods require quartz standards. The response of both methods, however, as shown by Tuddenham, Huggins, and Klug is particle size dependent. Joint studies by the Bureau of Mines and Mine Safety and Health Administration show that inaccuracy in quantitative quartz values may be as much as 30% when the particle size of the quartz standard does not match that of the quartz in coal dust.
Spatial Variations of Sulfur and Absorbed Copper Ions in Human Hair By X-Ray Line Scanning
Authors: Basu S.
Published: June 2020

The x-ray line scanning technique has the inherent ability to produce useful parameters for objective discrimination between the sites of metal ion incorporation, through dietary or drug ingestion, and sites of external application. Such parameters of comparative hair identification are not only important in forensic investigation but are also needed for diagnostic purposes. The project is intended for x-ray excited fluorescence spectroscopy within a scanning electron microscope (SEM) which will include, in due course, analysis of trace elements. The present studies were conducted by a careful application of the analog, or ratemeter approach, to energy dispersive x-rays of the major element (sulfur of hair Keratin) and a minor element (copper) of hair, with a view to determine the merit of the line scanning approach.
Evaluation of Concentration Techniques For Small Populations of Gunshot Residue (GSR) Particles Using Calibrated GSR Suspensions
Authors: Zeichner A. , Foner H. A. , Dvorachek M.
Published: June 2020

It is generally accepted that the best method for the identification of GSR is by scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDX), a technique which utilizes not only the chemical composition of the particles but also their size and morphology. Nevertheless, there remain many problems in the effective use of this technique.

The main problem is the length of time required to conduct a comprehensive search for GSR in the samples as presented to the SEM. Attempts to solve this problem have been made in two main directions: (1) Concentration of the GSR after sampling onto a small area concomittant with some sort of treatment to remove extraneous interfering matter, and (2) computer-aided mechanization of the searching procedure. The latter approach is still in its very early experimental stages, whilst the methods used in the second approach are in need of further improvement. In particular, there has been no quantitative work on the efficiency of various concentration processes when using very small populations of GSR.
Some Advantages of a 400-Kv High Resolution Analytical Electron Microscopy
Authors: Bando Y. , Matsui Y. , Kitami Y. , Inomata Y. , Oikawa T. , Suzuki S. , Honda T. , Harada Y.
Published: June 2020

There are some fundamental limitations in the use of the conventional analytical electron microscope (AEM), which restricts notably observation capabilities of high resolution imaging and microanalysis, mainly due to its poor image resolution and low peak to background ratio in EDS and EELS spectra, because operating voltages are lower in the range of 100 to 200 kV. It can be expected that such observation capabilities are very much improved with the increase of the accelerating voltage. From the point of view, a new JEM-4000EX AEM with an intermediate voltage of 400 kV is much prefered. The present paper describes some advantages of the 400 kV high resolution AEM in the use of both high resolution observation and microanalysis in EDS and EELS.

Fig.1 shows a phase contrast transfer function (CTF) curve, obtained for the JEM-4000EX with full analytical systems, in which a side entry specimen holder of beryllium stage with tilting angles of 30° in X-Y double axes is used. The EDS detector with a high angle location of 68, an energy analyzer (ASEA40) and a scanning image device (ASID40) are attached to the column.
Structural Transitions in AI203
Authors: Morrissey K.J. , Carter C.B.
Published: June 2020

The importance of A1203 materials in applications such as catalysis (γ-Al203) has brought about renewed interest both in the structures which form during the transition from γ- to α-Al203 and in the grain morphologies which accompany the transition. These transitions are especially important in the area of ceramic processing, as demonstrated by the recent reports. The structures of the transition aluminas, while still not completely understood, have been studied by several groups. The present paper reviews an on-going study of the transition from γ- to α-alumina where the emphasis is on the identifying the forms observed, and the morphology the grains adopt. Results from the initial parts of this study have previously been reported. The method of preparation determines the amounts and the forms of alumina present in the final sample.
Stress-Induced Ordering in Y203-Stabilized Tetragonal Zr02
Authors: Koo J. Y. , Anderson M. P.
Published: June 2020

Tetragonal Zr02 has been used as a toughening phase in a large number of ceramic materials. In this system, complex diffraction phenomena have been observed and an understanding of the origin of the diffraction effects provides important information on the nature of transformation toughening, ionic conduction, and phase destabilization. This paper describes the results of an electron diffraction study of Y203-stabilized, tetragonal Zr02 polycrystals (Y-TZP).

Thin foils from the bulk Y-TZP sample were prepared by careful grinding and cryo ion-milling. They were carbon coated and examined in a Philips 400T/FEG microscope. Fig. 1 shows a typical bright field image of the 100% tetragonal(t) Zr02. The tetragonal structure was identified by both bulk x-ray diffraction and convergent beam electron diffraction (Fig. 2. A local region within a t-Zr02 grain was subjected to an intense electron beam irradiation which caused partial martensitic transformation of the t-Zr02 to monoclinic(m) symmetry, Fig. 3 A.
The Microstructure of Steatite (Protoenstatite)
Authors: Lee W. E. , Heuer A. H.
Published: June 2020

Introduction

Traditional steatite ceramics, made by firing (vitrifying) hydrous magnesium silicate, have long been used as insulators for high frequency applications due to their excellent mechanical and electrical properties. Early x-ray and optical analysis of steatites showed that they were composed largely of protoenstatite (MgSiO3) in a glassy matrix. Recent studies of enstatite-containing glass ceramics have revived interest in the polymorphism of enstatite. Three polymorphs exist, two with orthorhombic and one with monoclinic symmetry (ortho, proto and clino enstatite, respectively). Steatite ceramics are of particular interest a they contain the normally unstable high-temperature polymorph, protoenstatite.

Experimental

3mm diameter discs cut from steatite rods (∼10” long and 0.5” dia.) were ground, polished, dimpled, and ion-thinned to electron transparency using 6KV Argon ions at a beam current of 1 x 10-3 A and a 12° angle of incidence. The discs were coated with carbon prior to TEM examination to minimize charging effects.
Energy-Minimizing Structures For Low-Angle Grain Boundaries in Zinc
Authors: Che Fu-Rong , King A.H.
Published: June 2020

Dislocation models for low angle grain boundaries have been widely known since 1950 and the proposed structures have been extensively confirmed by transmission electron microscopy, although most studies have been confined to the cubic metals. A generalization of the earlier geometrical work, known as the 0-lattice, represents the state of the art in predicting grain boundary structures on a purely geometrical basis, but the analysis is always predicated on the assumption that grain boundaries are basically planar defects. In some work on precipitation in the Al-Zn-Mg system Vanderwalker and Vander Sande observed non-planar low angle grain boundaries, although these may have been the results of pinning by embryonic precipitates or other solute interaction effects: we have observed non-planar boundaries in pure zinc where no such pinning effects are available to explain the puckering.
Yttrium Location and Chemical State in the Scale Formed On Y–Implanted 20%Cr/25%Ni/Nb Stabilised Stainless Steel in Carbon Dioxide at 825 C
Authors: Bennett M.J. , Desport J.A. , Labun P.A.
Published: June 2020

Understanding how the so-called reactive elements improve the protection afforded to alloys by Cr203 and Al203 scales continues to be a major topic of high temperature oxidation research. Considerable progress has stemmed from studies on alloy surfaces modified by the controlled addition of these elements, such as yttrium and cerium, by ion implantation. The influence of yttrium ion implantation upon the oxidation behaviour of the technologically important 20%Cr/25%Ni/0.7%Mn/0.7%Si/Nb stabilised (20/25/Nb) austenitic stainless steel in carbon dioxide at 825°C has been the subject of extensive investigation. The implantation of 1017 yttrium ions cm-2 reduced the overall attack of the 20/25/Nb steel and maintained scale adhesion during extended exposure (6500h). These effects derived from the initial stage (<1h) of scale development.

Further mechanistic understanding of the role of yttrium is critically dependent upon ascertaining both its location within the scale and its chemical state. This paper reports the preliminary results from an analytical electron microscopy examination of both back thinned(planar) and transverse sections of scales formed on yttrium implanted 20/25/Nb steel following 775 and 6500h oxidation in carbon dioxide at 825°C respectively.
Low-Voltage SEM Surface Studies of Microhardness and Topography of Ion-Implanted Cemented Carbides
Authors: Hefter J. , Oblas D.W. , Emma T.A.
Published: June 2020

The modification of metal, ceramic, and composite surfaces by implantation with high-fluence ion beams is an area of active current research. An implantation depth on the order of 200 nm is typical, necessitating specialized techniques for the determination of the physical properties of the surface. For example, microhardness measurements by indentation techniques must be made using low-load conditions. Furthermore, the high fluences required for surface modification produce topographical changes which can affect the sample surface. Low-voltage scanning electron microscopy (LVSEM) has proven to be an excellent approach for evaluating low-load Knoop microindents as well as providing valuable information on the topographic changes due to implantation.

EXPERIMENTAL. Samples were WC-6%Co cemented carbides tool inserts implanted perpendicularly to the surface with nitrogen at a fluence of 2x1017N2+/cm2. The implantation voltages were 90, 120, and 180 keV with corresponding implantation depths of 43, 57, and 84 nm. Microhardness measurements were made with a LEC0-M400LF tester at an indentation load of 10 g.
The Effects of Ion Implantation on the Surface Features of Inconel 600
Authors: Rubio John D.
Published: June 2020

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.

To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.
Observation of Phase Transition & Separation in an Amorphous Al:Ge Alloy
Authors: Lereah Yossi
Published: June 2020

Conductor-insulator composite materials are scientifically interesting, and also technologically if their structure could be well-controlled. Abeles considered their physical properties according to granular structure, i.e., small conducting particles embedded in insulator matrix. Deutscher has shown that the conducting and insulating materials are random distributed in Ge:metal systems (Ge is the insulator for this purpose, particularly at low temperatures); accordingly, their physical properties can be described by percolation theories. We show here, that by careful preparation, it is possible to get a fiber structure, which is challenging towards the preparation of one-dimensional conductors. Since amorphous alloys are becoming an important issue, this research is a good opportunity for studying their stability and transformation to the crystalline phase.
Point Defect Absorption and Dislocation Loop Formation at Grain Boundaries in Hvem-Irradiated Zr and Its Alloys:1. Influence of Solute Addition
Authors: Herring R.A. , Griffiths M. , Loretto M.H , Smallman R.E.
Published: June 2020

Because Zr is used in the nuclear industry to sheath fuel and as structural component material within the reactor core, it is important to understand Zr's point defect properties. In the present work point defect-impurity interaction has been assessed by measuring the influence of grain boundaries on the width of the zone denuded of dislocation loops in a series of irradiated Zr alloys. Electropolished Zr and its alloys have been irradiated using an AEI EM7 HVEM at 1 MeV, ∼675 K and ∼10-6 torr vacuum pressure. During some HVEM irradiations it has been seen that there is a difference in the loop nucleation and growth behaviour adjacent to the grain boundary as compared with the mid-grain region. The width of the region influenced by the presence of the grain boundary should be a function of the irradiation temperature, dose rate, solute concentration and crystallographic orientation.
AEM Investigation of a Thermomechanically Processed U-6NB Alloy
Authors: Ludtka Gail M.
Published: June 2020

The uranium-6 niobium (U-6Nb) alloy has been shown to exhibit elongations of 400-600% after a thermomechanical processing (TMP) sequence. This sequence (below the monotectoid temperature of 647°C) was utilized to develop the ultrafine grain size essential for superplastic behavior. The room temperature mechanical properties of the thermomechanically processed (TMP) U- 6Nb alloy before and after a gamma solution heat treatment (GSHT) were measured and compared to conventionally processed, GSHT U-6Nb alloy. These data are in Table I. The data show that the GSHT conditions have comparable mechanical properties and, so, the prior TMP treatment does not cause any loss of properties. However, the as-thermomechanically processed U-6Nb alloy exhibits negligible ductility and an extremely high yield strength. Metallography and AEM techniques have been utilized to characterize the TMP U- 6Nb microstructure to explain this behavior.
Influence of MBE Growth Conditions on Dislocation Densities of GaAs/Ge Epilayers Grown on Silicon Substrates
Authors: Hones K.M. , Sheldon P. , Yacobi B.G. , Mason A.
Published: June 2020

There is increasing interest in growing epitaxial GaAs on Si substrates. Such a device structure would allow low-cost substrates to be used for high-efficiency cascade- junction solar cells. However, high-defect densities may result from the large lattice mismatch (∼4%) between the GaAs epilayer and the silicon substrate. These defects can act as nonradiative recombination centers that can degrade the optical and electrical properties of the epitaxially grown GaAs. For this reason, it is important to optimize epilayer growth conditions in order to minimize resulting dislocation densities. The purpose of this paper is to provide an indication of the quality of the epitaxially grown GaAs layers by using transmission electron microscopy (TEM) to examine dislocation type and density as a function of various growth conditions. In this study an intermediate Ge layer was used to avoid nucleation difficulties observed for GaAs growth directly on Si substrates. GaAs/Ge epilayers were grown by molecular beam epitaxy (MBE) on Si substrates in a manner similar to that described previously.
Examination of Penetrable Volumes ("Pores") in A High-Performance Size-Exclusion Chromatography Matrix
Authors: Rigsby W. E. , Lingle W. L. , Kane D. J. O , Lee J.
Published: June 2020

The separation of proteins by high performance size exclusion chromatography (HPSEC) is based upon the interaction of a protein, having an effective hydrodynamic radius, A, with "pores" in the HPSEC matrix material. Two different theoretical treatments (1, 2) yield widely different estimates of the mean "pore" radius, Ao, and have different prediction errors for A. A given "pore" can be characterized by the radius of the largest molecule that it can accomodate, AiIf A > Ai, the protein is excluded from the "pore".

The "pore" diameter value quoted for TSK G3000 SW is 24.0nm (3). This is at variance with A0calculated by either treatment using the same HPSEC data: 28.4 ± 6.3nm (1) and 0.89 ± 5.4nm (2). From a knowledge of the "pore" volume it was calculated that approximately 50% of the total surface area of the HPSEC matrix corresponded to "pore". If Ae= 28.4nm, then ≥ 25% of the total surface area of the matrix should be occupied by "pores" with radii ≥ 28.4nm. These results prompted an investigation of the structure and size of "pores" in the HPSEC matrix material TSK G3000 SW.
Chemical Classification and Particle Sizing of Foundry Sands
Authors: DeMiglio D.S.
Published: June 2020

Much progress has been made in recent years towards the development of closed-loop foundry sand reclamation systems. However, virtually all work to date has determined the effectiveness of these systems to remove surface clay and metal oxide scales by a qualitative inspection of a representative sampling of sand particles. In this investigation, particles from a series of foundry sands were sized and chemically classified by a Lemont image analysis system (which was interfaced with an SEM and an X-ray energy dispersive spectrometer) in order to statistically document the effectiveness of a reclamation system developed by The Pangborn Company - a subsidiary of SOHIO.

The following samples were submitted: unreclaimed sand; calcined sand; calcined & mechanically scrubbed sand and unused sand. Prior to analysis, each sample was sprinkled onto a carbon mount and coated with an evaporated film of carbon. A backscattered electron photomicrograph of a field of scale-covered particles is shown in Figure 1. Due to a large atomic number difference between sand particles and the carbon mount, the backscattered electron signal was used for image analysis since it had a uniform contrast over the shape of each particle.
Planar Defects in Small Particles
Authors: Pérez R. , Avalos-Borja M.
Published: June 2020

Transmission electron microscope techniques have been extensively used in the determination of the morphology of fine metallic particles. These techniques have been of particular importance in obtaining topographical information during particle growth and sintering. Thus, for example, it has been found that some of the most elementary forms consist of half cubo-octahedral units with (111) faces and (100) basis. Furthermore, full cubo-octahedral units have also been found, some of them showing stacking faults (SF) through the particles.

It is important to point out that the characterization of this type of planar defects in small metallic particles has commonly been based on geometrical con. siderations. Additionally, the imaging conditions which have been used are the so-called weak beam (WB) diffraction conditions. Recent investigations have shown, on the other hand, that SF images under WB conditions present serious inconveniences, for example, contrast asymmetries in SF images which are not totally explained. Another difficulty with these WB fault images arises from twin boundaries which display image contrast similar to SF when a common reflection is strongly excited.
Energy-Filtered TEM With an External Spectrometer: Problems and Solutions
Authors: Chang C.F. , Shuman H. , Somlyo A.P.
Published: June 2020

Some of the requirements for obtaining reliable compositional images with high resolution energy filtered electron microscopy (EFEM) were tested through EFEM of negatively stained (with uranyl acetate) catalase crystals. We present energy filtered inelastic images of the catalase crystals showing the distribution of both uranium (U) and carbon (C) to 3.4 nm resolution, and introduce a more rigorous approach of image analysis of inelastic CTEM images. This approach is intended to eliminate two artifacts commonly encountered by EFEM, i.e. (a) contrast arising from variations in the shape of energy-loss background as a function of position (b) the amplitude contrast modulation at all energies. We have performed EFEM with a spectrometer that is a homogeneous field magnetic sector corrected for second order energy aberrations and is mounted below the projection chamber of a Philips EM (FEG) 400. The energy filtered electron image was converted into a light image by a transmission phosphor screen, detected with a silicon intensifier target(SIT) camera and displayed on a TV monitor.
Use of an Artificial Test Substrate For Evaluation of Immunocytochemical Labelling at the EM Level
Authors: Gagne G. D. , Lyter P. , Mollison K. , Mandecki W. , Miller M. F.
Published: June 2020

Immunocytochemical labelling by the protein A-gold (PAG) method is affected by many factors, including fixation and embedding procedures, concentrations of the antibody and PAG conjugate, incubation times, etc. Optimization of these parameters for the demonstration of an antigen in tissue sections can be difficult and time consuming, particularly when the antigen is sparsely distributed or is not contained within a well defined cellular compartment. Recently an artificial substrate system for the LM evaluation of immunoper-oxidase reactions was reported. We reasoned that a similar method could be employed to appraise PAG labelling at the EM level and selected a C5a (human complement factor) antigen/antibody system to test our hypothesis.
The “KIMWIPE” Effect in Ultra-Thin Cryosections
Authors: Taylor I. , Ingram P. , Sommer J.R.
Published: June 2020

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).
Reduction of Potassium in Kidney Proximal Tubules to Aid in Electron Probe X-Ray Microanalysis of Calcium
Authors: LeFurgey A. , Ingram P. , Mandel L.J.
Published: June 2020

For quantitative determination of subcellular Ca distribution by electron probe x-ray microanalysis, decreasing (and/or eliminating) the K content of the cell maximizes the ability to accurately separate the overlapping K Kß and Ca Kα peaks in the x-ray spectra. For example, rubidium has been effectively substituted for potassium in smooth muscle cells, thus giving an improvement in calcium measurements. Ouabain, a cardiac glycoside widely used in experimental and clinical applications, inhibits Na-K ATPase at the cell membrane and thus alters the cytoplasmic ion (Na,K) content of target cells. In epithelial cells primarily involved in active transport, such as the proximal tubule of the rabbit kidney, ouabain rapidly (t1/2=2 mins) causes a decrease2in intracellular K, but does not change intracellular total or free Ca for up to 30 mins. In the present study we have taken advantage of this effect of ouabain to determine the mitochondrial and cytoplasmic Ca content in freeze-dried cryosections of kidney proximal tubule by electron probe x-ray microanalysis.
“Skeletal” Elements Involved in Prey Capture by the Antrarctic Foraminiferan Astrammina Rara
Authors: Bowser Samuel S. , DeLaca Ted E.
Published: June 2020

Benthic foraminifera are considered primarily as “grazers” on bacteria, algae and other protozoans. However, in the benthic communities of the Ross Sea, Antarctica, field observations indicated that several species of agglutinated foraminifera (e.g., Astramina rara—shell ca. 2mm diameter) captured and digested larger metazoans (e.g., isopods such as Munna sp.—ca. 1cm in length). During prey capture the foraminiferan's reticulopodia (thin, anastomosing pseudopodia; Fig. 1) withstood the prey's vigorous escape efforts. We have attempted to identify the structural elements which impart the apparently high tensile strength of reticulopodia.

To study the reticulopodial cytoskeleton, we fixed specimens of Astramina with 3% glutaraldehyde/0.1M PIPES supplemented with 0.04% tannic acid, followed by brief postfixation with 0.5% 0s04. The reticulopodial surface was examined in specimens fixed with 3% glutaraldehyde/0.1M PIPES supplemented with 1.5mg/ml ruthenium red, followed by 0.5% OsO4 containing 1.5mg/ml ruthenium red.
Na+/Ca2+ Exchange in Plasma Membranes and Microsomal Fraction of Brain Cortex
Authors: Coutinho O.P. , Norton W.N. , Carvalho C.A.M. , Carvalho A.P.
Published: June 2020

The Na+/Ca2+ exchange system is one of the mechanisms responsible for regulating intracellular Ca2+ concentrations in neurons. However, the precise mechanism of Na+/Ca2+ exchange among synaptic plasma membranes and microsomes of neurons has yet to be resolved. The primary objective of the present investigation was to determine the specific transport properties with regard to Na+/Ca2+ exchange among neural synaptic plasma membranes and the various fractions of a microsomal density gradient separation.

Synaptic plasma membranes were obtained by hypotonic disruption of sheep brain cortex synaptosomes (Fig. 1). Enzymatic characterization of the synaptic plasma membranes revealed high Na+/K+ ATPase activity and low RNA content, which suggest that the material is predominantly of plasma membrane origin. The most common constituents consisted of membrane fragments and resealed vesicles (Fig. 2).
Postnatal Development of the Feline End Bulb of Held
Authors: Larsen S. A. , Pappas George D.
Published: June 2020

Maturation of the end bulb of Held (EBH) in the anteroventral cochlear nucleus (AVCN) was studied to determine what degree of plasticity is found in a synapse undergoing maturation, at the same time that the recipient neuron is increasing in size. Although the normal development of the neurons in the cochlear nucleus has been studied by Larsen and Morest, the normal development of the EBH has not been reported at the EM level.

The EBH was studied in kittens ranging in age from birth to 60 days postpartum and in adult cats using electron microscopy and Golgi preparations with light microscopy. At selected developmental ages (birth, alternate days starting at the second day of life and extending throughout the first postnatal month, and adult), serial-sectioned electron micrographs of the EBH and its recipient neuron, the large spherical cell (LSC), were traced using computer-assisted morphometry.
Midgut Endocrine Cells in the Mosouito, Aedes Aegypti
Authors: Brown Mark R.
Published: June 2020

The ultrastructure of a cell type in the insect midgut resembles that of peptide hormonogenic cells in the vertebrate gut. Also, vertebrate-like peptides such as pancreatic polypeptide (PP), glucagon, and insulin have been detected by immunoassays in insect midguts. Research was initiated to characterize the endocrine cells in the mosquito midgut, determine their immunoreactivity to antisera against vertebrate peptide hormones, and to identify organelles related to secretion of the hormones.

Female mosquitos had access to water or a sucrose solution for 7 days. Midguts from the insects were processed for TEM by routine methods. To assess the role of lysosomal enzymes in the secretory process, midguts were incubated in cerium-based medium for acid phosphatase histochemistry. For immuno-cytochemistry, midguts were fixed in a modified Bouin's solution (pH 7.6) and 156 glutaraldehyde for 1 hr and embedded in epon/araldite. Thin sections of midgut on nickel grids were sequencially emersed in filtered rabbit antisera to PP, 1:1000 in 0.05M Tris (pH 7.6); anti-rabbit IgG, 1:20; and PAP, 1:200.
X-Ray Microanalysis of Hooks and Calcareous Corpuscles in Tapeworm Larvae
Authors: Rikihisa Yasuko , Fainter Lily K. , Lin Y.C.
Published: June 2020

The Taenia taeniaeformis strobilocercus like other metacestodes has a unique hard structure: hooks and calcareous corpuscles. Previous studies on chemical analysis of the isolated hooks and calcareous corpuscles indicated that hooks are made of keratin-like protein and calcareous corpuscles contain calcium, phosphate and magnesium. In this study, x-ray microanalysis and the dot mapping procedure were carried out on these structures.

L. taeniaeformis larvae were dissected from the liver of the infected rats. The larvae were fixed in mixture of 1.25% paraformaldehyde, 2.5% glutaraldehyde and 0.02% trinitrophenol in cacodylate buffer, pH 7.2, and postfixed for 1 hr in 1% osmium tetroxide in the same buffer. After dehydration in a graded series of ethanols, larvae were embedded in Poly/Bed 812 (Polysciences, Inc.).
Backscattered Electron Imaging of Colloidal Gold Markers For Leukocyte Surface Antigens
Authors: Harven Etienne de , Soligo Davide
Published: June 2020

Markers for immuno-scanning electron microscopy had been, so far, selected for easy identification based on their distinctive shape (for example, haemocyanin, bacteriophage T4). These markers were always viewed in the secondary electron imaging (SEI) mode. Their size was not posing much of a problem of resolution for commercially available SEM, but was likely to prevent good labeling efficiency, due to steric hindrance phenomena. Higher labeling efficiency necessitates the use of markers of smaller size which, unfortunately, can rarely be unambiguously recognized in topographical SE images.

To correlate antigenic distribution with small cell surface structures like microvilli or coated pits, markers of smaller size (i.e., in the 20 nm range) must be used and clearly identified on the surface of well preserved cells. With the availability of colloidal gold particles complexed with various ligands this became possible, particularly if the labeled cells are viewed in the backscattered imaging (BEI) mode of the SEM, therefore basing the identification of the marker on its atomic number contrast rather than on its topographical contrast.
Application of Backscattered Electron Imaging to the Study of Scavenger Receptor-Mediated Endocytosis by Sinusoidal Cells in Bone Marrow
Authors: Becker R.P. , Geoffroy J.S.
Published: June 2020

The endothelial cells lining the postcapillary venous sinuses (sinusoids) in bone marrow take up colloidal gold-bovine serum albumin (BSA-Au) conjugates by means of a pathway involving coated pits and vesicles. Endocytosis of BSA- Au by these sinusoidal endothelial cells (sinusoidal cells) is rapid. Within one minute of pulse presentation (5 sec; intraaortic injection) with BSA-Au the probe is internalized and processed through pleomorphic endosomes to dense bodies known to be secondary lysosomes. By this time, 17% of the sinusoidal cell related BSA-Au is associated with the surface, while 83% is internalized, of which 2% is present in lysosomes. By four minutes, less than 8% of the observed BSA-Au is not internalized, the bulk being present predominantly in large pleomorphic vacuoles and dense bodies.

That the endocytic process involves coated pits and vesicles prompts the suggestion that it may be receptor mediated. In order to investigate this possibility, biochemical and morphological studies were performed to determine the specificity and saturability of the putative receptor. Morphological analysis of TEM thin sections was aided by viewing large areas of the luminal sinusoidal cell surface in secondary electron (SEI) and backscattered electron imaging (BEI) modes of the scanning electron microscope.
Intralysosomal Accumulation of Colloidal Gold-Low Density Lipoprotein Conjugates in Chloroquine-Treated Fibroblasts
Authors: Handley Dean A. , Arbeeny Cynthia M. , Witte Larry D.
Published: June 2020

Low density lipoproteins (LDL) are the major cholesterol carrying particles in the blood. Using cultured cells, it has been shown that LDL particles interact with specific surface receptors and are internalized via a coated pit-coated vesicle pathway for lysosomal catabolism. This (Pathway has been visualized using LDL labeled to ferritin or colloidal gold. It is now recognized that certain lysomotropic agents, such as chloroquine, inhibit lysosomal enzymes that degrade protein and cholesterol esters. By interrupting cholesterol ester hydrolysis, chloroquine treatment results in lysosomal accumulation of cholesterol esters from internalized LDL. Using LDL conjugated to colloidal gold, we have examined the ultrastructural effects of chloroquine on lipoprotein uptake by normal cultured fibroblasts.
Detergent Modification of Membranes: Fact or Artifact?
Authors: Hogan Margaret E. , Baker Karen K. , Flegler Stanley
Published: June 2020

Detergents have been used to modify biological membranes from nuclear envelopes and organelles to cellular bilayers of many cultured organisms. These modifications, usually designed to permeabilize or strip away the lipid bilayer, are as varied as the types of detergents used. The most commonly used agents are those with low critical micelle concentrations (Triton X-100, Tween-20, NP-40) making them difficult to completely remove from the reaction mixture. Octyl-POE (polydisperse octyloligooxyethylene), a detergent of high critical micelle concentration, is dialyzable and has been used in hopes of eliminating the possible masking effects of residual detergent in electron microscopy preparations. Through the use of a common treatment for all test solutions, a comparison of Triton X-100, NP-40, octyl-POE and a buffered solution as a control has been performed on isolated rat liver nuclei.
HVEM of Central Nervous System Tissue: Localization of the Site of Physiologic Measures
Authors: Turner J. N. , Swann J. W. , Brady R. J. , Carpenter D. O. , Collins D. N.
Published: June 2020

The correlation of physiology and ultrastructure is critical to many areas of neurobiology, but is usually possible only in “simple” systems, (neuromuscular junction, isolated invertebrate or lower vertebrate preparation or in culture). Such correlation is difficult in the central nervous system (CNS) due to its complex microanatomy, large number of synapses on each neuron and lack of techniques for finding specific sites, (e.g. presynaptic terminals buried in a mass of tissue). We are developing specimen labeling and preparation methods to mark the site at which a physiologic parameter has been measured or manipulated by a microelectrode. The marker must be either electron dense or fluorescent - the former is preferred. It must bind to the cell surface without excessive diffusion into surrounding tissue, and it must be visible during block trimming and sectioning, to form a traceable link from the macroscopic to the ultrastructure.
Ultrastructural Study of the Salivary Glands of Ornithodoros Moubata Nymphs During Feeding
Authors: Rosell-Davis Rosemarie , Coons Lewis B. , Needham Glen R.
Published: June 2020

Tick salivary glands are the principal organs through which pathogens are transmitted to the vertebrate host. Salivary glands of the argasid nymph, O. moubata, consists of grape-like clusters of two morphologically distinct types of acini; agranular or Type I and granular or Type II. Type I acini have an unknown function but in ixodids they produce a hydroscopic fluid used by the tick to take up moisture from the atmosphere. Type II acini secrete a fluid that contains an anticoagulant and pharmacologically active substances. The purpose of this study is to describe the ultrastructure of both types of acini using the nomenclature developed for ixodid salivary glands by Needham and Coons and Fawcett, et al.
Scanning Microscopy with Soft X Rays
Authors: Jacobsen C. , Kenney J. M. , Kirz J. , Rosser R. , Rarback H.
Published: June 2020

Among the various forms of soft x-ray microscopy, scanning offers several advantages. It is capable of forming images with the lowest radiation dosage to the specimen. The image is recorded digitally, therefore quantitative information on specimen absorptivity as a function of position is immediately available. In addition it is possible to make quantitative comparisons of images formed at more than one wavelength. Based on such information, elemental maps can be formed.

In collaboration with scientists from IBM and the National Synchrotron Light Source (NSLS), we constructed a scanning soft x-ray microscope that is operating on Beamline Ul5 of the 750 MeV VUV storage ring at the NSLS. The schematic diagram of the instrument is shown in Figure 1. The monochromatized beam of x-rays is collimated by a small pinhole. This small source is then further demagnified, using a Fresnel zoneplate, to form a focal spot, The specimen is mechanically scanned across this focal spot, and the x-rays transmitted by the specimen are detected by a flow proportional counter.
System For Producing 3-D Views in Contact Microradiography
Authors: Newberry Sterling P.
Published: June 2020

Through advances in X-ray Lithography, Contact Microradiography at submicrometer resolution is now commonly practiced. As with other forms of microscopy, eg Projection X-ray Microscopy, a 3 dimensional view can substantially enhance the usefulness of Contact Microradiography. The author wishes to show how this is accomplished by reporting previously unpublished work which demonstrates these possibilities and by projecting how the technique may possibly be applied at submicrometer resolution.

In the winter of 1949-50 while doing exploratory work on various forms of X-ray microscopy at General Electric, the author carried out comparative tests in his home laboratory on Contact Microradiography at accelerating potentials from 1.5 to 10 KV. A schematic of the demountable source and camera is shown in fig 1. The electron focusing system, independently discovered at about the same time by Ehrenberg and Spear, is simple and obvious. For this paper we are more concerned with the specimen holder and camera which are separated form the x- ray source by a thin beryllium window.