bluuebunny/crossref_metadata_2025 huggingface dataset:
A Shelved Structure for the Support of An Electron Optical Column
Authors: McLaughlin P.H.
Published: June 2020

A shelved structure for the support of an electron optical column affords advantages both to the designer and the user. A lens may be removed for cleaning for example, without demounting the remaining lenses. A custom device for another example, may be placed on a shelf, substituting for the standard lens perhaps so that some specialized research may be undertaken. Especially advantageous is a shelved arrangement if the column assembly is designed to hang from a supporting structure such as a gas borne floating platform, as is the case with the system described below.

As shown on the schematic, a floating platform (I) supports the electron source apparatus (2) and a U-shaped column support shelf (3). The column support shelf acts as a key for locating and supporting three struts (4) which with nuts (5) support the condenser shelf (6), the objective shelf (7), the upper projector shelf (8), and the lower projector shelf (9).
Characterisation of Polycrystalline Silicon Carbide by Scanning and Transmission Electron Microscopy
Authors: Faulkner D. , Stevens R.
Published: June 2020

Silicon carbide is an extremely hard refractory material. Corrosion resistance, which is a general limitation of most carbides, is also good. These features alone make silicon carbide an important engineering material, but in addition, its low neutron absorption cross-section, and its behaviour under irradiation make it a particularly attractive material for use in a nuclear environment.

The mechanical strength of self-bonded silicon carbide is primarily dependent on grain size and on the presence of free silicon in the material. Figure 1 shows a scanning electron micrograph of a fracture surface. The morphology is typical of a brittle transgranular fracture, although there is evidence of some ductility in the free silicon phase.
Observations oh Nucleation and Growth of Voids in Nickel
Authors: Brimhall J. L. , Kissinger H. E. , Mastel B.
Published: June 2020

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.

Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.
Excessive ThO2 Particle Growth in Ni-2ThO2 at High Temperature
Authors: Kimmel E. R. , Anthony H. L. , Scheithauer W.
Published: June 2020

It is generally accepted that a uniform spatial distribution of fine refractory oxide particles is required in an oxide-dispersion-strengthened metal to provide good elevated-temperature strengths. The presence of these particles stabilizes the cold-worked microstructure by anchoring low-angle cell boundaries and by restricting the motion of dislocations during loading. Such action by the particles must be a function of the interparticle spacing as is proposed by the Orowan model for yield stress. For a given volume percent of oxide in the metal matrix, the interparticle spacing is directly proportional to the particle size. Therefore, particle growth during the processing of oxide-dispersion-strengthened metals increases the interparticle spacing and inherently decreases the strength.
Electron Microscope Observations of Magnetic and Electric Effects
Authors: Silcox John
Published: June 2020

Several aspects of magnetic and electric effects in electron microscope images are of interest and will be discussed here. Clearly electrons are deflected by magnetic and electric fields and can give rise to image detail. We will review situations in ferromagnetic films in which magnetic image effects are the predominant ones, others in which the magnetic effects give rise to rather subtle changes in diffraction contrast, cases of contrast at specimen edges due to leakage fields in both ferromagnets and superconductors and some effects due to electric fields in insulators.
Internal Cavities in Fiber Boundaries of Annealed Tungsten Wire
Authors: Tufts Charles F.
Published: June 2020

Tungsten wires (0.010 inch diameter, doped with alumina and silica, and annealed for 10 minutes between 1500°C and 1550°C in vacuum of 10-6 torr) were examined by transmission electron diffraction contrast microscopy (TEDCM) using thin sections (800 A to 1000 A thick) prepared by a technique reported previously. Circular markings were observed with sizes ranging from 45 A to 450 A. Population of such markings was low in similar wire that was examined in the “as drawn” state before annealing. Most markings were circular; a few exhibited elongated and hexagonal shapes. Most circular markings were arranged in linear arrays (“stringers”) that were within fibers and parallel to fiber boundaries also.
Tetragonal Hydride in Lot Hydrogen Content Zircaloy
Authors: Katz O. M.
Published: June 2020

The mechanical integrity and corrosion behavior in nuclear reactor environments of zirconium alloys can be related to the formation and morphology of intermetallic hydrides which precipitate in them. The nature of these hydrides has been studied and the results summarized in the literature. However, there still seems to be some uncertainty as to the type of hydride which precipitates in low hydrogen content zirconium alloys; i.e., whether it is the face-centered-cubic ∫ phase), designated ZrH1.5, or the face-centered tetragonal hydride, γ‘, of c/a around 1.08. The composition of γ’ was originally placed at ZrH0.5 but was later shown by neutron diffraction to be non-stoichiometric and extending to ZrH.
Resistivity and Electron Microscopy Study of Precipitates in Fe-Ni-Co-Mo
Authors: Christou A. , Lowry R.W.
Published: June 2020

The details of the precipitation hardening mechanisms have been studied previously. Peters and Cupp have measured the kinetics of precipitation in an 18 pet Ni-Co-Mo steel. Hardy and Heal have studied the reversion processes caused by annealing for short times at temperatures above the aging temperature. This paper reports studies of the pre-precipitation and reversion stages in an 18 pct. Ni-Co-Mo steel (maraging with .46 pct Ti).

The annealed microstructure of the parent steel consists of BCC martensitic grains. Within the matrix lies a fairly high density of dislocations whose configurations appear irregular. These dislocations are nucleation sites and are shown in Figure 1.
A Comment on Mica as Electron Microscope Specimen Support Film
Authors: Heinemann Klaus
Published: June 2020

Single crystal mica substrate films thin and stable enough for high resolution electron microscopy can be prepared in a variety of ways, e.g., by adhesive tape cleavage, direct mechanical stripping, and by ion bombardment thinning from one side.

High resolution electron microscopic studies of such thin mica substrate films exhibit the following characteristic features:

— Relatively high rate of radiation damage during electron microscope observation

— Comparatively low amount of background phase contrast, even after complete decomposition due to radiation damage

— Good mechanical and electrical stability, especially in areas which have been exposed to a high electron flux and show radiation damage.
Electron Microscope Image-Recording System for Dynamical Observation
Authors: Mayeda M. , Tukahara S. , Yotsumoto M. , Taoka T.
Published: June 2020

Recent advance in high voltage electron microscope has entailed an expanded application of a continuous observation of non-static structures in specimens at elevated temperature or under stress. In order to attain this end, the need for a VTR system capable of recording structural changes is increasingly felt. Through several investigations, we eventually decided to adopt an Image Orthicon tube, as pick-up tube, considering its high recording speed, reliability and ease of operation.

In this paper, a detectable speed of the specimen depending upon the specified resolution, electron beam flux and size of the specimen is experimentally discussed by adjusting the gain of the amplifier so as to obtain an optimal condition. The TV system consists of a high-gain Image Orthicon tube and a transformer circuit which has a band width of 8MHz and a frame speed of 1/30 sec, as shown in Fig. 1.
Some Applications of the U. S. Steel MVEM
Authors: Lally J. S. , Thomas L. E. , Fisher R. M.
Published: June 2020

A variety of materials containing many different microstructures have been examined with the USS MVEM. Three topics have been selected to illustrate some of the more recent studies of diffraction phenomena and defect, grain and multi-phase structures of metals and minerals.

(1) Critical Voltage Effects in Metals and Alloys - This many-beam dynamical diffraction phenomenon, in which some Bragg resonances vanish at certain accelerating voltages, Vc, depends sensitively on the spacing of diffracting planes, Debye temperature θD and structure factors. Vc values can be measured to ± 0.5% in the HVEM ana used to obtain improved extinction distances and θD values appropriate to electron diffraction, as well as to probe local bonding effects and composition variations in alloys.
The 1-MeV Electron Microscope Installation at the University of Colorado
Authors: Fotino Mircea
Published: June 2020

A new 1-MeV transmission electron microscope (Model JEM-1000) was installed at the Department of Molecular, Cellular and Developmental Biology of the University of Colorado in Boulder during the summer and fall of 1972 under the sponsorship of the Division of Research Resources of the National Institutes of Health. The installation was completed in October, 1972. It is installed primarily for the study of biological materials without many of the limitations hitherto unavoidable in standard transmission electron microscopy. Only the technical characteristics of the installation are briefly reviewed here. A more detailed discussion of the experimental program under way is being published elsewhere.
Use of the Electron Microscope Hydration Chamber to Study Small Water Drops
Authors: Chang W.
Published: June 2020

The observation of water drop formation and evaporation in our electron microscope hydration chamber suggested that we might use it to study cloud physics and cloud-chamber physics problems. These would include growth of very small water droplets with and without heterogenous nuclei and their coalescence into larger drops like rain drops. Also, the evaporation of small drops and their freezing to form hail. The chamber can be regarded as an observable micro-atmosphere with variable supersaturation. Super saturation can be achieved by supplying the chamber with water vapor from an external water source at a higher temperature than the chamber. The hydration chamber developed in the Electron Optics Lab of R. P. M. I. has undergone one more refinement, i.e., temperature control stage designed by Dr. Hui.
An Environmental Wet Cell For High Voltage Electron Microscopy
Authors: Tighe N.J. , Flower H.M. , Swann P.R.
Published: June 2020

A differentially pumped environmental cell has been developed for use in the AEI EM7 million volt microscope. In the initial version the column of gas traversed by the beam was 5.5mm. This permited inclusion of a tilting hot stage in the cell for investigating high temperature gas-specimen reactions. In order to examine specimens in the wet state it was found that a pressure of approximately 400 torr of water saturated helium was needed around the specimen to prevent dehydration. Inelastic scattering by the water resulted in a sharp loss of image quality. Therefore a modified cell with an ‘airgap’ of only 1.5mm has been constructed. The shorter electron path through the gas permits examination of specimens at the necessary pressure of moist helium; the specimen can still be tilted about the side entry rod axis by ±7°C to obtain stereopairs.
High Voltage Electron Microscopy of Defects in Lithium Ferrite
Authors: Van der Biest O.
Published: June 2020

Above 750°C lithium ferrite (LiFe5 O8) has an inverted spinel structure, i.e. With Fe3+ on tetrahedrally coordinated sites and a 3:1 mixture of Fe3+ and Li3+ on the octahedral sites. The latter take on an ordered arrangement below 750°C. It has been shown that the ordered structure contains antiphase boundaries (APB), with a displacement-vector of 1/2 <110=. In this paper observations on stacking faults and dislocations in the ordered and disordered structure are reported.

Slices of a flux grown single crystal were thinned using the ion bombardment technique. Observations were made in the 650 kV Hitachi microscope, equipped with a high angle tiltstage which allows a tilt over an angle of ± 30°.
Refining of High-Yield Wood Pulp
Authors: Parham Russell A.
Published: June 2020

As the supply of wood for paper and other wood fiber products constantly dwindles, the ensuing economic situation demands that wood pulping procedures be modified to provide higher yields of usable wood substance. Mechanical, semichemical, and strictly chemical methods are presently employed to reduce wood to its fibrous components. However, use of pulp fibers for high quality papers requiring whiteness or other specific attributes limits the selection of suitable pulping routes. Essentially, for quality products, it is the residual wood lignin — the intercellular matrix and cell wall encrustant (commonly 25-30% of the wood) — that is largely removed, since it exerts a general negative effect on most paper properties. Resultant pulp yields are usually in the range of 55-60%, also reflecting the loss of some wood carbohydrates that are intimately associated with the lignin structure.
Electron Diffraction Study of Cellulose
Authors: Hebert Jacques J. , Muller Linda L.
Published: June 2020

Cellulose is the most abundant polymer occurring in nature. It constitutes the cell wall of most, if not all, green plants. In the form of wood, wood pulp and cotton, cellulose represents a very valuable agricultural commodity and is, therefore, the subject of much intensive research.

Chemical modifications of cotton are brought about predominately by the reaction of various reagents upon the surface of the crystalline elementary fibrils which make up the sub-fiber structure. For this reason, electron diffraction studies were undertaken to evaluate this microstructure and its various modifications. Electron-diffraction techniques offered several advantages over x-ray methods. Electrons have intensity; therefore, much smaller samples can be used.
Row-Nucleated and “Shish Kebab” Structures in Crystalline Polymers
Authors: Tucker Paul , George Waller , Holland V. F.
Published: June 2020

Traditionally, polymer crystallization studies have been conducted on quiescent systems, but most polymers in commercial use are crystallized while under the influence of external dynamic stress fields. Only during the last decade has attention been given to the structure and morphology of polymers crystallized in systems that resemble those used for producing fibrous products.

Although phenomenological studies of stress crystallization are now being conducted, scant attention is given to the basic theoretical raison d'etre. It is fairly well understood how stress increases the nucleation rate, but it is not well understood as to why a fibrous product results.
Chromic Acid Etching of Polyethylene
Authors: Muzzy J. D. , Hester R. D. , Hubbard J. L.
Published: June 2020

Polyethylene is one of the most important plastics produced today because of its good physical properties, ease of fabrication and low cost. Studies to improve the properties of polyethylene are leading to an understanding of its crystalline morphology. Polyethylene crystallized by evaporation from dilute solutions consists of thin crystals called lamellae. The polyethylene molecules are parallel to the thickness of the lamellae and are folded since the thickness of the lamellae is much less than the molecular length. This lamellar texture persists in less perfect form in polyethylene crystallized from the melt.

Morphological studies of melt crystallized polyethylene have been limited due to the difficulty of isolating the microstructure from the bulk specimen without destroying or deforming it.
Digital Display of Lens Current For Accurate Calibration of the Electron Microscope
Authors: Dunn Robert F. , Preiss Guenther W.B.
Published: June 2020

During normal operation a 5-10% variation is reasonable to expect between the magnification readout on the instrument and the actual magnification at the image plane. An error of this magnitude becomes ntenable when either precise comparative dimensions are necessary, or when undertaking stereology studies. In some instances, it is possible to obtain the required degree of accuracy on the basis of relative dimensions. Accurate stereology studies require for each set of samples precise magnificatipn calibration which is generally done by repeating a calibration for each set of samples. An alternative approach involves quantitative monitoring of the lens current separately for each of the objective, intermediate, and projector lenses with a digital milliampere meter.
Grain Orientation Studies on Polycrystalline Titanium by Means of Electron Channeling Patterns
Authors: Ruff A. W.
Published: June 2020

Preferred orientation textures are known to develop in wrought commercial products, such as rolled sheet or extruded tubing, depending on the material type and on the forming process. Substantial deviations from an arrangement of randomly oriented polycrystalline grains can occur. The amount and type of preferred orientation is customarily determined by x-ray diffraction measurements. That technique averages over a large number (102 to 104) of grains. This paper will describe an investigation of orientation texture in commercial titanium speet on a grain-by-grain basis. Selected area electron channeling patterns (SACP) were obtained from individual grains in the polycrystalline specimens and provided accurate orientation data. Those data were required to explain particular morphological features observed in a recent investigation of the active dissolution of titanium in sulphuric acid.
Preparation of Thin Single Crystal Silicon Substrates for in situ Electron Microscope Studies
Authors: Maa J. S. , Lee J. I. , Hutchinson Thos. E.
Published: June 2020

The in-situ electron microscope technique has been shown to be a powerful method for understanding the nucleation and growth of thin films formed both by vacuum vapor deposition and ion beam sputter-deposition. Single crystal silicon which has only been chosen as substrate for thin film deposition outside the electron microscope has now been prepared in a form suitable for in-situ deposition.

The method of the preparation of thin silicon substrate is a combination of jet chemical etching and modified ion beam thinning. A specimen of thickness roughly 0.010 inch is first etched from both sides by the jet etching technique. After jet etching, it is transferred to the Commonwealth Scientific ion micro-milling instrument and bombarded from both sides with Argon ion beam. A pin hole occurs in the center of the specimen after about 30 minutes of ion bombardment.
Phosphorus Precipitation in Si-Ge (30 at. %) Alloy
Authors: Hills C. R. , Thomas G. J. , Maurin J. K.
Published: June 2020

Solution treated and quenched Si-Ge (30 at. %) alloy doped with phosphorus to a level of 1.54 × 1020 atoms/cm3 has been shown to increase in resistivity following aging at elevated temperatures. This effect is indicative of a loss of phosphorus from substitutional sites in the Si-Ge lattice and consequent precipitation of the excess phosphorus into electrically inactive centers. The structural changes occurring as a result of aging have been studied using transmission electron microscopy.

Examination of the solution heat-treated material (1 hr. at 1000°C, then quenched) prior to aging revealed the presence of small defect clusters ranging in size from 20-80 Å, as well as larger defects approximately 200 Å in diameter exhibiting large strain field contrast.
Neutron Radiation Damage in Zr-2.5 wt % Nb Alloys
Authors: Faulkner D. , Styles R.C.
Published: June 2020

There has been much speculation recently concerning the nature of radiation induced defects in zirconium and its alloys. In particular, the absence of voids in pure zirconium and in Zircaloy-2 at high fluences and at temperatures in the range 0.3 to 0.5 Tm is inconsistent with observations made on most elemental f.c.c., b.c.c., c.p.h. metals, on stainless steels and on Nimonic PE16 alloys. Wolfenden and Farrell have reviewed the evidence and discuss the importance of dislocation density and/or gas content on void formation.

The specimens examined in this study were.3 m.m. discs of Zr-2.5 wt % Nb fuel sheath material irradiated to 1.24 × 102 1 n. cm−2 (E > 1 MeV) at 380-390°C (∼ 0.31 Tm, where Tm is the melting temperature of the β phase) and to 1.37 × 102 1 n. cm−2 at 470 - 490°C (∼ 0.36 Tm) in the WR-1 organic cooled reactor.
Electron Microscopy and X-Ray Microanalysis of Metal Spheres Formed in a Low Gravity Environment: A Prelude to Skylab
Authors: Brown John L. , Hubbard James L. , Johnson James W.
Published: June 2020

Skylab is America's first manned space station. It offers a unique opportunity to conduct experiments in astronomy, geoscience, the life sciences and engineering. Included in the latter category is the M512 facility for materials processing in space. In addition to other experiments this unit is equipped with a chamber which can be vented to space vacuum and an electron beam heating source capable of melting small metal pendants attached to a rotating pin wheel which may be successively placed at the electron gun focal point. Mechanical fixtures are provided to release the molten body from its support post, if desired, allowing it to solidify under high-vacuum zerogravity conditions.
Observation of Superlattice Dislocations on Cube Planes in Ni3Al
Authors: Oblak J. M. , Rand W. H.
Published: June 2020

The energy of an a/2 <110> shear antiphase. boundary in the Ll2 expected to be at a minimum on {100} cube planes because here strue ture is there is no violation of nearest-neighbor order. The latter however does involve the disruption of second nearest neighbors. It has been suggested that cross slip of paired a/2 <110> dislocations from octahedral onto cube planes is an important dislocation trapping mechanism in Ni3Al; furthermore, slip traces consistent with cube slip are observed above 920°K.

Due to the high energy of the {111} antiphase boundary (> 200 mJ/m2), paired a/2 <110> dislocations are tightly constricted on the octahedral plane and cannot be individually resolved.
Electron Mtcroscope Study of the Structure of Natural Pyrolusite (Pseudo-Psilomelane)
Authors: Staudhammer K. P. , Murr L. E.
Published: June 2020

A manganese-bearing mineral characterized by a black hair-like surface crystal growth, and somewhat unique to the Socorro County, New Mexico area, has been referred to as psilomelane (pseudo-pyrolusite). Psilomelane, however, is a hydrated barium manganese oxide, generally A 3 X6Mn8016 (A= B2+, Mn3+, Al3+, Fe3+, S14+, etc. and X=O, OH). Natural psllomelane 1s a smooth, black, uniform or botryoidal mineral possessing an or- thorhombic crystal structure.

Large specimens of the hair-like c·rystalline mineral (Fig. 1 (a) were analyzed by X-ray diffraction utilizing Debye-Scherrer nd diffractometer techniques and found to be tetragonal (a=4.42A, c = 2.87A).
Observations on Virgula Structure in Two Graptoloid Graptolites
Authors: Berry W. B. N. , Takagi R. S.
Published: June 2020

The sexually-produced individual in the fossil colonial organisms, the graptolites was housed in a conical structure, the prosicula. Prosiculae in many graptoloid graptolites, those graptolites that were planktonic, have a tubular extension from their apices. That extension in graptoloids with uniserial and biserial scandent rhabdosome form has the aspect of a relatively rigid, rod-like structure that extends through the thecate part of the rhabdosome and beyond. Details of the virgula structure are most readily observed using electron microscopy.

Virgula structure has been examined in a uniserial scandent graptoloid, a monograptid of the M. priodon group, and in a biserial scandent graptoloid, an Orthograptus of the O. quadrimucronatus group.
Contrast in High Resolution Bright Field and Dark Field Images of Thin Specimens
Authors: Cowley J. M.
Published: June 2020

The resolution attained in an electron microscope image may be judged in a number of ways, depending on the means of interpretation used. The capabilities of available instruments are now approaching the point where a clear distinction between types of limitation of resolution and interpretive processes becomes important. Until recently the attainable resolution was limited by incoherent blurring of the image intensity by chromatic aberration effects due to electron energy spread and by electrical and mechanical instabilities of the microscope. Then the incoherent “spread function” defines the resolution, which may possibly be improved by ‘image deblurring’ by optical or computerized image processing. Now with the best microscopes the effects of the incoherent blurring can be reduced until the dominating effect in the limitation on resolution comes from coherent perturbations of the image due to defocus and spherical and other aberrations.
Inelastic Scattering in Electron Microscopy
Authors: Isaacson M. , Langmore J. , Wall J. , Crewe A. V.
Published: June 2020

The effort to image biological molecules by high resolution (2-4 Å) dark field electron microscopy has stimulated interest in those factors Which influence image contrast. It is known that elastically scattered electrons can be used to obtain high resolution information about a specimen. On the other hand, most inelastically scattered electrons cannot contribute any high resolution information about the specimen since they are the result of a nonlocalized interaction of the incident electrons with the electrons in the specimen. Moreover, in the conventional transmission electron microscope (CTEM) without a chromatic aberration corrector or an energy filter between the specimen and recording plane, inelastically scattered electrons blur the image, due to the chromatic aberration of the objective lens. This has particular importance in biological electron microscopy, since the ratio of total inelastic to elastic scattering for carbon is 1.6.
Comparison of Image Modes for the Low Resolution (20.0nm) Observation of Thick Biological Objects
Authors: Turner J. N. , Parsons D. F.
Published: June 2020

One-of the major efforts of our laboratory is the observation of hydrated whole cell mounts in the electron microscope. Efforts to date have shown superior resolution as compared to the light microscope only in the thin portions of spread cells (Parsons et al., 1972). The thicker portions suffer from severe chromatic aberration which limits contrast and resolution even at 800kV. Thus, an image mode capable of enhancing image contrast and eliminating chromatic aberration is necessary. Furthermore, it is presently unrealistic, for the thick portions of the cell, to rely on increasing the accelerating potential. Since the selection of an image mode is a complex function of the required contrast and resolution, and the specimen under observation, we have limited ourselves to a resolution of 20.0nm as an intermediate goal, and ask what image mode will maximize the contrast.
A Spherical-Aberration Corrector Using Electrontransparent Conducting Foils
Authors: Thomson M. G. R.
Published: June 2020

One of the problems associated with building any aberration-corrected electron microscope objective lens lies in the difficulty of obtaining a sufficiently short focal length. A number of systems have focal lengths in the 1cm. range, and these are more suitable for microprobe work. If the focal length can be made short enough, the chromatic aberration probably does not need to be corrected, and the design is much simplified. A corrector device which can be used with a conventional magnetic objective lens of short focal length (Fig. 1) must either have dimensions comparable to the bore and gap of that lens, or have very large magnetic or electric field gradients. A successful approach theoretically has been to use quadrupoleoctopole corrector units, although these suffer from very large fifth order aberrations and a limited field of view.
Computer Enhancement of Weak-Beam Images
Authors: Horgen H.M. , Villagrana R. E. , Maher D. M.
Published: June 2020

In order to perform quantitative image-contrast analysis of low-contrast electron micrographs one must first increase the signal to noise ratio. As an example, consider the weak-beam method of imaging defects by transmission electron microscopy. In this technique an increase in the resolution of closely spaced dislocations is obtained through a narrowing of the individual dislocation image widths. However, this reduction in image width is accompanied by a corresponding decrease in the signal to noise ratio, which in many instances renders quantitative image-contrast analysis impractical. In this note we present an example of the computer image enhancement of a weak-beam micrograph.
Electron Energy Analyzer Design
Authors: Kuyatt Chris E.
Published: June 2020

The use of electron energy analyzers has increased dramatically in the last few years. Monochromator-analyzer combinations have achieved resolutions of a few milli-electron volts for electron energies from a few tenths of an electron volt to tens of thousands of electron volts. Figure 1 shows an energy loss spectrum of nitrogen which is typical of the performance of low energy electron spectrometers, and illustrates the wide dynamic range of these instruments.

Various energy dispersing elements have been used in electron energy analyzers, some of the most popular being cylindrical and spherical electrostatic deflectors and the Wien filter.
A Prototype Field-Emission Scanning Transmission Electron Microscope
Authors: Banbury J.R. , Bance U. R.
Published: June 2020

A prototype field emission scanning transmission electron microscope has been constructed and is under further development at AEI Scientific Apparatus Limited.

The field emission gun has a triode construction, with geometry such as to produce a divergent beam from a virtual source whose position remains substantially constant over a wide range of total accelerating voltages. The gun has been operated satisfactorily from below 10 kV to over 90 kV (upper limit set by power supplies), with the field emission diode voltage typically between 2 kV and 4 kV and total emission of a few microamps. Single-crystal tungsten tips of either (111) or (310) orientation are used, though (310) tips normally produce a superior probe current stability.
Contrast Enhancement of Glutaraldehyde Cross-Linked, Ethylene Glycol Dehydrated Tissue With Triafol Nets
Authors: Kretzer Frank
Published: June 2020

When tissue is prepared for thin section, high resolution electron microscopy with the specific goal of minimally denaturing membrane protein and with the least lipid solubilization possible, the method of choice is cross-linking membrane protein with a short exposure to 1% glutaraldehyde, brief dehydration in O°C ethylene glycol, and Vestopal infiltration. After such a procedure, the resultant contrast, even after uranyl acetate section staining, is extremely low. This low contrast is due to the few charged groups on native proteins available for interaction with the stain and the protein's compact structure which prohibits stain ions from penetrating into the nonpolar interior.

To optimally increase the resultant low contrast in an effort to study the complex, three dimensional, condensed state of heterogeneous membrane proteins (10-100A) in the 300A-thick mitochondrial inner membranes (Figures 1-2) and the 270A-thick chloroplast partition membranes, sections were mounted over Triafol nets (Figure 3) spanning one hole slot grids.
Prolonged Fixation Studies For Spaceflight
Authors: Corbett Robert , Philpott Delbert E. , Black Sam
Published: June 2020

Observation of subtle or early signs of change in spaceflight induced alterations on living systems require precise methods of sampling. In-flight analysis would be preferable but constraints of time, equipment, personnel and cost dictate the necessity for prolonged storage before retrieval. Because of this, various tissues have been stored in fixatives and combinations of fixatives and observed at various time intervals. High pressure and the effect of buffer alone have also been tried.

Of the various tissues embedded, muscle, cartilage and liver, liver has been the most extensively studied because it contains large numbers of organelles common to all tissues (Fig. 1).
Scanning Electron Microscopy of Human Articular Cartilage
Authors: Redler I. , Zirany M.L. , Mansell J.
Published: June 2020

Specimens of human normal and osteoarthritic cartilage obtained during surgical procedures were washed with normal saline to remove gross debris and synovial fluid, fixed in 0.1% glutaraldehyde in Ringer's solution for periods varying between one and four hours, dehydrated in graded acetone solutions and air dried. They were coated with a layer of carbon(100A°) and gold palladium alloy(200A°) and examined in a JSM-U3 SEM.

The articular surface of normal cartilage appeared undulated and was composed of a dense irregular network of fibers approximately 0.1 micron thick.(Fig.1) Ridges on the surface measuring between 2 and 6 microns in width were frequently noted in a parallel, intersecting, or random pattern.
The Chatterbox: A Device for Hearing Chatter as Sections are Cut
Authors: McCutchen C. W. , Tice Lois W.
Published: June 2020

Ultramicrotomists live in a state of guerilla warfare with chatter. This situation is likely to be permanent. We can infer this from the history of machine tools. If set the wrong way for the particular combination of cutting tool and material, most if not all machine tools will chatter.

In more than 100 years since machine tools became common, no one has evolved a practical recipe that guarantees avoiding chatter. Rather than follow some single very conservative rule to avoid chatter in all cases, machinists detect it when it happens, and change conditions until it stops. This is possible because they have no trouble telling when their cutting tool is chattering. They can see chatter marks, and they can also hear a sometimes deafening noise.
Similarities of the Embryonic Liver and Hepatoma in the Human
Authors: Weide G. C. Vander , Burns W. A. , Geschickter C. F.
Published: June 2020

The human embryonic liver and hepatocellular carcinoma (hepatoma) have been infrequently studied at the ultrastructural level. It has been mentioned that there probably is an ultrastructural similarity between embryonic-fetal liver and hepatoma, but this has not been adequately documented in the literature. We wish to report the fine structural similarities we have seen between the embryonic liver and hepatocellular carcinoma.

The outstanding similarity is the appearance of the cellular membrane. This is differentiated into microvilli indicating increased activity. The majority of the microvilli are notably elongated. The hepatocytes do not demonstrate a compact arrangement and cellular attachments are infrequent. Bile canaliculi, when observed, appear large with prominent microvilli. The rough endoplasmic reticulum is relatively increased and prominently arranged in stacks. Glycogen is not readily apparent. Lipid-like vacuoles are seen in the cytoplasm.
Ultrastructural Evaluation and Pathophysiology of Testicular Sertoli Cell Neoplasms from Dogs With a Syndrome of Hyperestrogenism
Authors: Capen C. C. , Martin S. L.
Published: June 2020

A syndrome of feminization associated with testicular neoplasms has been reported frequently in male dogs but occurs rarely in man and other species. Although an excessive secretion of estrogenic hormones has been suspected on the basis of clinical and pathologic findings, elevated circulating levels have not been demonstrated conclusively. The specific objective of this investigation was to evaluate ultrastructural1y functional Sertoli cell neoplasms from 5 male dogs with feminization and to correlate these findings with the results of estrogen assays.

The affected testes were enlarged, irregularly lobulated, firm and were retained in the abdomen of all dogs (Fig. 1A). The neoplastic cells were spindle-shaped or polyhedral and formed distinct tubules separated by a delicate connective tissue stroma (Fig. 1B).
Ultrastructural Localization of Cholesterol in Human Arteriosclerosis
Authors: Sekhri Karta , Mills Clint , Younes Henry
Published: June 2020

Several reports have appeared recently demonstrating a technique for the localization of cholesterol in a variety of tissues. The technique is based on the premise that free cholesterol reacts with digitonin to form cholesterol digitonide which appears as needle-like crystals or spicules under the electron microscope.

In order to study the fine structure of the aorta, surgical biopsies from several patients (ranging in age from 45 to 68 years) and with clinical evidence of arteriosclerosis were fixed promptly in Flickinger's fixative (2% formaldehyde, 2.5% glutaraldehyde) containing 0.2% digitonin but buffered with .1M sodium cacodylate. After fixation for 3 hours aortic samples were washed in cacodylate buffer and post fixed in buffered osmium tetroxide for 2 hours & embedded in Epon-Araldite.
The Morphology of Vacuolated Cells in the Liver Following Administration of Vitamin A.
Authors: Minick Odell T. , Yokoo Hidejiro , Batti Fawzia
Published: June 2020

Vacuolated cells in the liver of young rats were studied by light and electron microscopy following the administration of vitamin A (200 units per gram of body weight). Their characteristics were compared with similar cells found in untreated animals.

In rats given vitamin A, cells with vacuolated cytoplasm were a prominent feature. These cells were found mostly in a perisinusoidal location, although some appeared to be in between liver cells (Fig. 1). Electron microscopy confirmed their location in Disse's space adjacent to the sinusoid and in recesses between liver cells. Some appeared to be bordering the lumen of the sinusoid, but careful observation usually revealed a tenuous endothelial process separating the vacuolated cell from the vascular space. In appropriate sections, fenestrations in the thin endothelial processes were noted (Fig. 2, arrow).
Preparation of Amyl Acetate and Acetone Labile Eggs From Parasitic Nematodes For Scanning Electron Microscopy
Authors: Specian Robert D. , Allison Venita F. , Ubelaker J. E. , Martin J. H.
Published: June 2020

The structure and composition of parasitic nematode eggs, particularly the shells, are of interest to various investigators. Egg morphology is widely used for species identification where sacrifice of the host is not desirable. Scanning electron microscopy (SEM) allows surface sculpture patterns on eggs of closely related species to be observed and aids in identification. The egg shell, in many species of parasitic nematodes, is composed of a proteinchitin-lipid complex which, unfortunately, is labile in many organic solvents including those routinely employed in the preparation of samples for SEM by the critical point drying method.

The present study is concerned with the fine surface morphology of eggs from Toxocara canis (Werner, 1782), Toxocara mystax (Zeder, 1800), and Ascaris suum Goeze, 1782, as revealed by SEM after several preparative procedures.
Scanning Electron Microscopy of Dried and Acid Treated Shells of Difflugia
Authors: Eckert Barry S. , McGee-Russell S. M.
Published: June 2020

Difflugia lobostoma is a shelled amoeba. The shell is an external structure of considerable mass which presents the animal with special restrictions in cell locomotion which are met by the development of active pseudopodial lobopodia containing, apparently, an organized system of thick and thin microfilaments (Eckert and McGee-Russell, 1972). The shell is constructed of sand grains picked up from the environment, and cemented into place with a secretion. There is a single opening through which lobopods extend. The organization of the shell was studied by scanning electron microscopy (SEM).

Intact shells or animals with shells were dried by the critical point method of Anderson (1966) or air dried, after primary fixation in glutaraldehyde.
Occurrence and Anatomy of Dense Axillary Cells at the Juncture of the Shoot Apical Meristem and Leaf Primordium in Maize
Authors: Graham Effin T.
Published: June 2020

The test plant was a single cross hybrid maize (Zea mays), WF9 X 38-11. Shoot apices were sampled at the three-leaf stage of seedling growth. The tissues were fixed 72 hr in cacodylate-buffered (0.025 M, pH 7-3) 5% glutaraldehyde, and were postfixed 3 hr in buffered 2% osmium tetroxide and 1 hr in aqueous 1% uranyl acetate. Dehydration was done in a long series of acetone solutions, 10% to absolute. Embedding was done in a low viscosity epoxy resin, and the sections were stained with lead citrate. All steps from fixation to embedding were done at room temperature.

The accompanying figure depicts a group of 3 dense cells located at the base of the axil separating the lower flank of the apical dome and the leaf primordium.
Cryoprotection of Irradiated Specimens
Authors: Box Harold C.
Published: June 2020

Breedlove and Trammell predict that visualization of molecules by electron microscopy will prove impossible because in the imaging process the molecular architecture will be destroyed Their contention has stimulated considerable debate. In this paper we wish to consider one aspect of the problem, namely, can the effects of radiation damage be minimized by maintaining the sample at low temperature during observation? In this discussion low temperature implies 4.2°K (boiling point of liquid helium at atmospheric pressure) or lower.

Low temperature will not, of course, prevent the ionization of molecules by high energy electrons. Electron spin resonance (ESR) studies on a variety of biological compounds do suggest, however, that much less atomic rearrangement occurs at low temperature.
Surface Ultrastructure and Topochemistry of Parasitic Platyhelminths
Authors: Lumsden Richard D.
Published: June 2020

The “cuticle” of tapeworms and trematodes is, in reality, a cellular syncytium, referred to in the recent literature as a tegument. The external limiting membrane is coated with a layer of carbohydrate-rich polyelectrolytes. In its structure and cytochemistry, this coating of the tegument plasmamembrane closely resembles the ubiquitous glycocalyx of more conventional animal cell types. This paper will review some of the cytological features of tapeworm and trematode body surfaces, focusing on the contributions of the glycocalyx to the functional properties of the host-parasite interface.

Lacking a gut, tapeworms utilize the tegument alone for chemical interchange with the host. Attendant to this function is a brush border containing a number of enzymes and transport mechanisms.
Flagellar Attachment in Selected Trypanosomes
Authors: Paulin J. J.
Published: June 2020

Movement in epimastigote and trypomastigote stages of trypanosomes is accomplished by planar sinusoidal beating of the anteriorly directed flagellum and associated undulating membrane. The flagellum emerges from a bottle-shaped depression, the flagellar pocket, opening on the lateral surface of the cell. The limiting cell membrane envelopes not only the body of the trypanosome but is continuous with and insheathes the flagellar axoneme forming the undulating membrane. In some species a paraxial rod parallels the axoneme from its point of emergence at the flagellar pocket and is an integral component of the undulating membrane. A portion of the flagellum may extend beyond the anterior apex of the cell as a free flagellum; the length is variable in different species of trypanosomes.
Permeability of Endometrial Blood Vessels to Exogenous Horse Radish Peroxidase in Mice. Electron Microscope Study
Authors: Castillo-Jessen M.C. , González-Angulo A.
Published: June 2020

Information regarding the normal morphology of uterine blood vessels at ultrastructural level in mammals is scarce Electron microscopy studies dealing with endometrial vasculature despite the functional implications due to hormone priming are not available. Light microscopy observations with combined injection of dyes and microradiography along with histochemical studies does not enable us to know the detailed fine structure of the possible various types of blood vessels in this tissue. The present work has been designed to characterize the blood vessels of endometrium of mice as well as the behavior of the endothelium to injection of low molecular weight proteins during the normal estrous cycle in this animal. One hundred and forty female albino mice were sacrificed after intravascular injection of horse radish peroxidase (HRP) at 30 seconds, 5, 15, 30 and 60 minutes.
Electron Diffraction of Wet Retina Rod Disc Membranes
Authors: Hui S. W. , Matricardi V. R. , Parsons D. F.
Published: June 2020

Electron diffraction is extremely useful in studying membrane preparations in microscopic quantities. Although certain biological membranes, especially those occured in natural lemella form, have been subject to X-ray diffraction studies, so far no electron diffraction study of wet membranes had been reported, apart from a preliminary attempt made in this laboratory.! The reasons had been: 1) The inability to keep the specimen in its natural state during observation, and 2) The naturally occured lemella of membranes such as nerve myelin, retina rod and chloroplast are usually too thick for the electron beam to penetrate.

We report here our preliminary results on an electron diffraction study of the disc membranes of whole wet retina rod outer segments, using the 1 Mev electron microscope at the U.S. Steel Research Center at Monroeville, Pa., with a hydration stage built by this laboratory for that microscope.
Electron and Light Microscopy of Wet Unstained Mammalian Cells
Authors: Matricardi V.R. , Parsons D.F.
Published: June 2020

Dynamically pumped hydration stages have been developed for electron microscopes. These devices are able to maintain the specimen under a controlled atmosphere (e.g. 100% relative humidity) while being viewed by the electron beam. These devices preserve the pressure differential by using apertures to impede the flow of gas escaping into the column. If adequate pumping is provided the stage can maintain the specimen at a pressure of one atmosphere while the pressure in the column is of the order of 10−4 torr.

We have already obtain d electron micrographs of whole wet cells by using the United States Steel high voltage microscope (see figures one and two), but have not yet been able to visualize cytoplasmic streaming or brownian motion within the cell.
Structural Specializations of Sarcoplasmic Reticulum in Skeletal Muscle
Authors: Waugh R. A. , Spray T. L. , Sommer J. R.
Published: June 2020

The sarcoplasmic reticulum (SR) in muscle is a complex system of tubules in which several regions of discrete structural specializations can be distinguished, e.g. junctional SR (terminal cisternae), extended junctional SR, intermediate cisternae and fenestrations. This study reports the presence of two of these in locations where they have not been described previously.

The discovery of additional locations of SR fenestrations was substantially aided by the fortuitous filling of the SR by lanthanum which, in addition, provided a negative stain of the intraluminal contents of the SR. The preparatory techniques were quite routine.