bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of Polyethylene Fibrils as Revealed by Gold Decoration
Authors: Yeh G. S. Y. , Krueger D. L.
Published: June 2020

Periodic structures present in polyethylene fibrils that were produced upon deformation of single crystals either by shearing between glass slides, by drawing on Mylar substrates, or by ultrasonic waves are revealed with clarity by gold decoration as compared to platinum shadowing. In all three cases, the periodicity as ludged by the spacing of gold particles decorated along the fibrils varies between 100 and 300 Å depending somewhat on the perfection of the original crystals; although it does not appear to be related to the original lamellar crystal thickness. Beady structures about 250 Å in diameter are often present in fibrils produced by drawing crystals that were grown at large supercoolings or crystals that had been subsequently crosslinked. Another interesting feature is that the fibrils produced by the shearing method appear to have a limiting diameter of about 100 Å.
Transmission Electron Microscopy of Terrestrial Rocks and Minerals
Authors: Inman Maurice C.
Published: June 2020

Comprehensive application of transmission electron microscopy (TEM) to rocks and minerals has been made possible by the recent introduction of reliable ion beam thinning devices. The potential of TEM as a diagnostic tool for evaluation of the thermal history, mode of formation, age and general environment of both terrestrial and lunar materials is a matter of considerable present interest. Studies of terrestrial basalts and volcanic glasses at this University have recently revealed that TEM can provide information of considerable diagnostic significance, a specific example of which is given below.

Figure 1 is a view of twin bands which we have commonly observed in the plagioclase (Labradorite) component of an olivine basalt from the Cascade Mountains, Oregon. The twin planes are defined by parallel light and dark contrast fringes, and selected area diffraction indicates that we are observing albite twins with composition plane (010). Of particular interest is the morphology of the albite twins at region A. For purposes of comparison, Fiqure 2 reproduces the characteristic appearance of a growing annealing twin in the metal nickel.
Field Ion Microscopy of Tantalum-Carbon Alloys
Authors: Rao P.
Published: June 2020

Transmission electron microscopy has proved the existence of interstitial order in the tantalum-carbon system and the structure has been suggested to be tetragonal of composition Ta64C. Detection of interstitial order using field ion microscopy is shown to be possible by observing the general morphology of the interstitial atoms appearing as bright spots at the tip surface. This is necessitated by the fact that photographic recording of stable images from interstitial solid solutions is difficult due to the inherent instability of interstitials present at and in a thin shell of undetermined thickness below the surface. However, interstitial ordering, if present, should be detectable by the appearance of regularly spaced rings of carbon atoms when both species (metal and interstitial) are continuously field evaporating.
Selected Area Diffraction of Very Small Specimen Areas using Improved Lattice Imaging Methods
Authors: Heinemann Klaus , Poppa Helmut
Published: June 2020

In conventional selected area electron diffraction methods, the lower limit of the selected specimen area is usually of the order of 10,000 Å. For many applications – including the detailed study of very early stages of thin film growth – it is imperative, however, to (a) study the crystallography of much smaller specimen areas, and (b) to obtain selected area orientation information from extremely thin diffracting specimens where the ratio of electron scattering specimen mass to that of the supporting film is so low that no useful electron diffraction pattern can be obtained.
Observation of Ferrimagnetic Domain Walls in CoFe2O4 With A High Voltage T.E.M.
Authors: De Jonghe L. C.
Published: June 2020

Cobalt ferrites are ferrimagnetic oxides of the spinel type, exhibiting magnetic ordering along <100>. Ferrimagnetic domain walls have been observed in this ceramic material with the specimens in the regular position. Even though the field of the objective lens is quite high ∼7 k gauss) domain walls may be observed if the specimens are symmetrically oriented with respect to the field direction of the objective lens, so that adjacent domains have approximately equal energy. Ill are such orientations for cobalt ferrites. Under these conditions, only ╥/2 domain walls are expected. Such ╥/2 ferrimagnetic domain walls are shown in Fig. 1. Since magnetostriction accompanies magnetic ordering, the domain wall boundaries are also coherent twin boundaries which can be imaged with the specimen in focus.
In-Situ Metal-Gas Reaction Studies
Authors: Heinemann Klaus , Poppa Helmut
Published: June 2020

Studies of the kinetic and microstructural aspects of the high-temperature interaction of oxygen and hydrogen with single crystalline {100} nickel films were conducted in-situ in a differentially pumped UHV specimen chamber of a transmission electron microscope. To atomically clean the specimen surface before initiating the reaction process, a miniature argon ion gun was developed and installed in the chamber, allowing sputter etching of the specimen surface under simultaneous electron microscope observation while removing surface material at a rate of up to 50 Å/min. The background pressure in the chamber was in the low 10−9 torr range. During the ion etching and metal-gas reaction processes, the total contribution of all background gases – except for tne particular reaction gas – was kept below 2×10−8 torr and recovered to the low 10−9 torr range within several minutes after closing the gas inlet valve.
Crystallinity of Liquid-Like, Vapor-Deposited Tin Films
Authors: Murr L. E.
Published: June 2020

In a previous paper, Singh and Murr described the vapor-liquidsolid phase growth of Sn thin films according to the conventions originally outlined by Semenov and Komnik. More recently, Singh and Murr also quantitatively outlined the nucleation and growth characteristics of vapor-deposited Sn thin films and concluded that the results were indicative of a recrystallization process involving the supercooling of liquid drops as described earlier by Takagi.

The present study involves a rigorous examination of the nature of the solidified liquid-like Sn clusters following vapor deposition onto air-cleaved NaCl (001) substrates for the condition Ts≥2/3Tm; where Ts and Tm are the substrate temperature and the melting temperature of the Sn in °K respectively.
Characterization of Sputtered Films using the Scanning Electron Microscope
Authors: Schneidmiller R. F. , Thrower W. F. , Ang C.
Published: June 2020

Solid state materials in the form of thin films have found increasing structural and electronic applications. Among the multitude of thin film deposition techniques, the radio frequency induced plasma sputtering has gained considerable utilization in recent years through advances in equipment design and process improvement, as well as the discovery of the versatility of the process to control film properties. In our laboratory we have used the scanning electron microscope extensively in the direct and indirect characterization of sputtered films for correlation with their physical and electrical properties.

Scanning electron microscopy is a powerful tool for the examination of surfaces of solids and for the failure analysis of structural components and microelectronic devices.
An Electron Microscope Study of Switching from Glass to Crystalline Liquid and Vapor Phase in Thin Se Films
Authors: Herd S. , Chaudhari P.
Published: June 2020

Selenium is a common alloying addition to a variety of materials that show switching behavior, however, few electron microscope studies of amorphous Se exist presumably because of the difficulties in crystallizing the material due to its high vapor pressure. The crystallographic aspects of the crystallization behavior of amorphous Se have been reported by Shiojiri and the dislocation formation during the growth of Se crystals have been studied by Asseev et al. We investigated the reversible transformation of vacuum deposited amorphous Se to the crystalline, liquid and vapor phases by utilizing a triple sandwich film structure of C-Se-C or SiO2-Se-C. The electron beam itself was used as power source in all experiments.
Technique for Visualizing Subgrain Structure at Fatigue Crack Tips by Ion Etching and Scanning Electron Microscopy
Authors: Shaw G. G. , Benson D. K.
Published: June 2020

The subgrain structure in ram size areas adjacent to fatigue cracks has been observed by ion etching followed by scanning electron microscopy. The etch patterns have been definitely identified as subgrain structure resulting from the fatigue strains by direct comparison with channelling electron microscopy. The technique is described as it was applied to a single crystal of aluminum which had been fatigued in Stage I by reversed bending.

A 5 mm long section of crystal containing the crack was cut from the fatigue sample by spark machining. This section was sliced into pieces 2 to 3 mm thick, and a slice selected with the crack tip close to its center. The selected slice was placed in a shallow aluminum cup about 2 cm in diameter.
Preparation of Zirconium Alloys for Ion Bombardment and Transmission Electron Microscopy
Authors: Koch E. F. , Lee D.
Published: June 2020

A procedure has been developed to reveal ion induced damage in Zircaloy by transmission electron microscopy. The technique consists of using a modified twin-jet electropolishing method to prepare samples for Ni ion bombardment at elevated temperatures followed by further polishing to provide foils suitable for transmission electron microscopy. The electrolyte used to polish Zircaloy-2 consisted of 50 ml perchloric acid (70%), 175 ml glacial acetic acid, and 100 ml ethylene glycol,. A 0.005” thick and 1/8” diameter sample was first polished from one side only, using a E.A. Fischione twin jet electropolisher equipped with a sample holder designed by W.G. Johnston and J.H.Rosolowski, (Fig.1).
Effects of a Modified Wehnelt Grid Assembly on Electron Microscope Image Contrast
Authors: Maher D. M. , Tanaka A.
Published: June 2020

The need for higher brightness electron sources with improved coherence has been appreciated for some time by electron microscopists and electron optical manufacturers. The results given in this paper suggest that changes in these electron source characteristics can be expected to influence the image quality of lattice defects taken under two-beam dynamical conditions in thick crystals.

In this study stacking faults and bounding partial dislocations in silicon were imaged at various crystal thicknesses using JEM 200 electron microscopes operated at 200 kV. linages were, obtained using microscopes equipped with a normal Wehnelt grid assembly and a modified assembly. In both cases a standard hair-pin filament was used. The modified Wehnelt assembly (so-called Cool beam assembly) differs from the normal one both in shape and filament position.
Observations of Defect Generation at Stacking Faults in Boron Diffused and Oxidized Silicon Films
Authors: Cullis A. G. , Maher D. M. , Hsieh C. M.
Published: June 2020

Recently, the transmission electron microscope (TEM) has been used to study the formation and geometry of defect colonies in annealed and quenched silicon and in thermally oxidized and boron diffused silicon. The purpose of the present study was to examine subsidiary defect formation which can occur during the climb of Frank partial dislocations bounding stacking faults in boron diffused and subsequently thermally oxidized silicon. In these experiments, a {001} epitaxial silicon wafer (n-type, 1Ω−cm) was boron diffused (to 5×1018/cm3), and then steam oxidized for 2 hr at 1050°C. Prior to oxidation the wafer was cleaned using HF as a last step. After oxidation the oxide layer was first removed and then specimens from the wafer were chemically thinned from the substrate side for TEM observations (200 kV).
The Third Dimension in Scanning Electron Microscopy: Scanning Auger Microscopy
Authors: MacDonald Noel C.
Published: June 2020

During the past few years, Auger Electron Spectroscopy (AES) has been successfully applied to solving many practical surface chemistry and thin film problems. When used as a surface chemical analytical tool, AES identifies chemical elements present in the first 5-50 Å of a solid surface. The combination of AES and ion sputter etching is used to chemically profile thin films with an in-depth resolution of better than 10% of the thickness of the film. Examples of chemical profiles will be presented which illustrate the good in-depth spatial resolution obtainable using AES combined with ion sputter etching.

In the past, the lateral spatial resolution has been limited by the electron gun available in commercial AES equipment.
The Application of SEM Techniques to the Study of Crystal Defects
Authors: Thompson M.N.
Published: June 2020

The present study is directed to the imaging of dislocations using backscattered electrons and verification that defect analysis procedures established using TEM techniques can also be applied to scanning transmission electron microscopy (STEM). A SEM attachment based on the design of Ong coupled to a Philips EM300 microscope equipped with goniometer stage was used in this investigation. Fundamental to the design of this TEM/STEM system, which utilises a Riecke-Ruska condenser-objective lens, is the formation of a convergent beam diffracttion pattern whose intensity distribution is dependent only on the scattering processes in the crystal and independent of the scanning probe position. The presence of this stationary diffraction pattern allows the crystal orientation to be monitored on the TEM viewing screen during STEM operation and assists accurate collection of a specific scattered electron fraction for image formation.
Climb Behavior of Dislocations during Small Plastic Deformation at Low Temperature
Authors: Geiss R. H. , Kuhlmann-Wilsdorf D. , Tropf W. J. , Wilsdorf H. G. F.
Published: June 2020

The climb behavior of dislocations during stage I was studied in specially prepared crystals of two types: (a) Copper crystals virtually free of super-saturated vacancies and their condensation products were grown at a rate of 2.5 to 3 cm/hr by passing a molten zone through 99.999% copper samples kept in a high vacuum at ambient temperatures within a few degrees of their melting point, then slow cooling them so as to minimize vacancy supersaturations (b) Crystals prepared as above were reheated to near their melting point in evacuated quartz tubes, then removed from the furnace and air cooled. According to earlier results a substantial fraction of the supersaturated vacancies arising during air cooling were expected to precipitate out in the form of very small voids which on slight straining would be collapsed by dislocations) while at the same time causing the dislocations to tangle and “mushroom”).
Observations of the Cell Structure of Heavily Rolled Phosphor Bronze
Authors: Caron R. N. , Shapiro S.
Published: June 2020

Transmission electron microscopy has often been used to observe the nature of the heavily cold worked condition in metals in order to evaluate the effect of this microstructure on subsequent processes and properties. However, interpretation of a heavily cold rolled microstructure when viewed normal to the rolling plane is made difficult by the fact that the average thickness of the elongated cells resulting from such deformation is often smaller than the thickness of the foil. The final thickness of a heavily rolled structure is often too thin for convenience in making thin foils trans- verse to the rolline plane. The technique of plating copper to thicken the thin cold rolled sample sufficiently for om pat ibility with standard methods for preparing transmission foils has been successfully used.
Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys
Authors: Fornwalt D. E. , Geary A. R. , Kear B. H.
Published: June 2020

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.

Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.
Structural Characterization of Powder Metallurgy and Composite Materials
Authors: Lawley Alan
Published: June 2020

Of the broad spectrum of new or advanced competitive engineering materials for structural applications, composites and high-density powder metallurgy (P/M) materials are perhaps of most interest. Rational development necessitates a thorough knowledge of the associated structure-property relationship; particular importance is vested in the role of microstructure on properties such as strength, creep resistance, ductility, toughness and fatigue resistance. Examination of structure in these materials presents a number of unique problems; however, intelligent application of the various techniques of optical and electron microscopy can provide a quantitative characterization. The primary objective here is to review these approaches and to illustrate observations by reference to metal-matrix composites and various P/M materials.
Interfacial Stability and Mechanical Behavior of Nichrome-Tungsten Filamentary Composites
Authors: Burden S. J. , Lawley A.
Published: June 2020

Filamentary composites are frequently fabricated by an elevated-temperature process such as diffusion bonding. Because of differences in chemical potential of the elements at the interface, processing or subsequent elevatedtemperature exposure is accompanied by interdiffusion and/or reaction. Generally, this is reflected in the degradation of mechanical properties since it is the interface that controls stress transfer from matrix to reinforcement. The purpose of this study was to characterize the interfacial dependence of mechanical behavior in potential high-temperature nickel-alloy matrix composites reinforced with refractory metal wires, and to determine the effectiveness of diffusion barrier layers between fiber and matrix.

Tungsten wire-reinforced nichrome composites (Vf in range 10% to 20%; wire diameter 0.010“) were diffusion bonded under vacuum for one hour at 1100°C.
Radiation Damage and High Resolution Biological Electron Microscopy
Authors: Glaeseral Robert M.
Published: June 2020

The task of obtaining high resolution images that contain useful information in a size range smaller than 10Å to 15Å has proven to be much more difficult in the case of biological and organic specimens than in the case of inorganic materials. One of the fundamental difficulties that limits these efforts is the fact that organic materials are almost always much more susceptible to radiation damage than are inorganic specimens. If meaningful results are to be obtained, the total electron exposure must be kept below some maximum “critical exposure”, such that the amount of damage that does occur is still below a specified, acceptable level. When the allowed, “critical” exposure is very low, then fluctuations in the number of electrons collected per resolved picture element will be relatively high. At some point these fluctuations are so severe that it becomes impossible to see the actual structure of the image.
Test Specimens For High Resolution Scanning Electron Microscopy
Authors: Greer Raymond T.
Published: June 2020

A useful resolution specimen for day-to-day SEM instrument standardization should exhibit uniform, periodic microstructure of hundreds to thousands of angstroms, show low contrast, have low cost, be easily prepared, and demonstrate long term stability.

Opal (Figure 1) is particularly useful as a resolution specimen; however, several aspects of sample preparation should be emphasized. A high quality gem opal chip a few millimeters in diameter is sufficient for carefully controlled etching in, for example, 10% HF for 30 seconds. The choice of test specimen microstructure size is established by the maximum wavelength of color observed under white light. The iridescence effect is dictated by the microstructure of uniform silica spheres arranged in a cubic closest packing array.
An Electron Microscope with Highly Coherent Illumination
Authors: Worsham R. E. , Mann J. E. , Richardson E. G. , Ziegler N. F.
Published: June 2020

It has been shown theoretically that it is possible to correct for the defocus and the primary spherical aberration of the objective lens in a conventional transmission microscope column if the chromatic aberration can be made negligible and the transverse coherence length of the illuminating beam is about 1000A, or higher. The techniques were demonstrated with simulated micrographs. The microscope shown in the accompanying drawing and photograph was designed to test this procedure experimentally.
A Computer Controlled Vidicon System For High Resolution Microscopy
Authors: Goldfarb William , Siegel Benjamin M.
Published: June 2020

The image collecting system of the experimental high resolution electron microscope being developed in this laboratory must be compatible with the ultra-high vacuum (10−10Torr) maintained in the total column. The characteristics of an SEC porous KCl target used to record directly the primary high energy beam has been previously reported. It was also noted that a phosphor transducer could be used with an external recording medium without loss of information if adequate electron optical magnification and sufficient light coupling are utilized.
Object Wave Determination by Single-Sideband Methods
Authors: Downing Kenneth H. , Siegel Benjamin M.
Published: June 2020

Under the “weak phase object” approximation, the component of the electron wave scattered by an object is phase shifted by π/2 with respect to the unscattered component. This phase shift has been confirmed for thin carbon films by many experiments dealing with image contrast and the contrast transfer theory. There is also an additional phase shift which is a function of the atomic number of the scattering atom. This shift is negligible for light atoms such as carbon, but becomes significant for heavy atoms as used for stains for biological specimens. The light elements are imaged as phase objects, while those atoms scattering with a larger phase shift may be imaged as amplitude objects. There is a great deal of interest in determining the complete object wave, i.e., both the phase and amplitude components of the electron wave leaving the object.
Wiener Processing of Phase Contrast Electron Micrographs
Authors: Welton T. A. , Ball Frances L. , Harris W. W.
Published: June 2020

Previously reported work has given some theoretical reason to believe that the effective resolution of an electron micrograph can, under suitable conditions, be enhanced by computation. The Oak Ridge High Coherence Electron Microscope, described elsewhere in these proceedings, will attempt to exploit this concept to its logical limit, but a preliminary test has been thought worthwhile. For this purpose, a series of micrographs has been made of TMV on thin carbon, negatively stained with PTA. The Siemens 1A was used at 100 μ and magnification 150,000, with condenser aperture 100/tand no objective aperture. The defocus was exaggerated to imitate the effect of sphercal aberration in the High Coherence Microscope. Figure 1 is a portion of one member of the focal series, with a size of 425Å square.
Color Lithography of Electron Micrographs-An Example of Art in Science, Science in Art
Authors: Watson John H.L. , Jacobs Ellen
Published: June 2020

Although essentially still an art form, the lithographic process in both black and white and in color has been applied here to present the infinite variety and form of subjects available from both transmission and particularly from scanning electron micrographs. It is our purpose in this exhibit to emphasize the subject as one of “art in science” rather than the reverse, and to illustrate the unexpected beauty inherent in and derivable from color lithography of electron micrographs. At the same time development of the technique can offer obvious aids in communicating ultrastructural observations: the artist can strengthen those parts of a micrograph which it is desirable to emphasize, or with his art he can increase the threedimensional effects in a single picture, or areas and objects can be accurately color-labeled.
Observations on Diamond Knife Composition Through Electron Microprobe X-Ray Analysis
Authors: Spurr A. R. , Wittkopp R. W.
Published: June 2020

In the use of diamond knives for sectioning materials to be observed by electron microscopy, new knives occasionally do not have the expected durability or do not yield satisfactory sections from the outset. The problem seems to be inherent in specific diamond knives with no apparent tearing on the manufacturing source. Among the causes or combination of factors that may account for this, we are confining our attention to one, namely, variations in composition of the diamond itself. Impurities such as silicon, magnesium, aluminum, calcium, iron, and copper in quantities of 0-79 ppm are reported in diamond (Raal, 1957; Bunting and Van Valkenburg, 1958) and some are believed to be related to lattice defects.
Golgi Apparatus and Melanogenesis: Ultrastructural Study of a Human Cellular Blue Nevus (Melanocytoma)
Authors: Allegra S.R.
Published: June 2020

The respective roles of the ribo somes, endoplasmic reticulum, Golgi apparatus and perhaps nucleus in the synthesis and maturation of melanosomes is still the subject of some controversy. While the early melanosomes (premelanosomes) have been frequently demonstrated to originate as Golgi vesicles, it is undeniable that these structures can be formed in cells in which Golgi system is not found. This report was prompted by the findings in an essentially amelanotic human cellular blue nevus (melanocytoma) of two distinct lines of melanocytes one of which was devoid of any trace of Golgi apparatus while the other had normal complement of this organelle.
Changes in Heart Ultrastructure Following Exposure To High Levels of CO2
Authors: Harrison Gladys A. , Klein Gloria
Published: June 2020

A number of factors (e.g., chemicals, altitude, ischemia) are known to affect cardiovascular tissue at the subcellular level, but little is known about the specific changes associated with spaceflight factors. Conventional physiological measurements of heart rate, blood pressure and blood flow velocity all demonstrate significant changes under spaceflight conditions; however, the basic mechanisms for these changes have not been determined. Other factors affecting the cardiovascular system which may be encountered in spaceflight include excess carbon dioxide, increased temperature and alterations in the ionic balance. Certainly changes occur in function and these functional alterations may very well be mirrored by structural alterations. An analysis of these changes induced by various spaceflight factors would be a valuable addition to the knowledge of spacerelated pathology.
Characterization of Tamm-Horsfall Urinary Glycoprotein
Authors: Robinson John P. , Puett J. David
Published: June 2020

Much work has been reported on the chemical, physical and morphological properties of urinary Tamm-Horsfall glycoprotein (THG). Although it was once reported that cystic fibrotic (CF) individuals had a defective THG, more recent data indicate that THG and CF-THG are similar if not identical.

No studies on the conformational aspects have been reported on this glycoprotein using circular dichroism (CD). We examined the secondary structure of THG and derivatives under various conditions and have correlated these results with quaternary structure using electron microscopy.

THG was prepared from normal adult males and CF-THG from a 16-year old CF female by the method of Tamm and Horsfall. CF female by the method of Tamm and Horsfall.
Utilization of Ion Beam Etching in Conjunction With Scanning Electron Microscopy to Study Red Blood Cell Structure
Authors: Spector M. , Burns L. C. , Kimzey S. L.
Published: June 2020

Human red blood cells (Fig. 1) were ion beam etched in the specimen chamber of a scanning electron microscope in order to study the red cell structure. The red blood cells were fixed in glutaraldehyde and critical point dried in carbon dioxide prior to etching. Etching was carried out at about 10−4 torr using 3KV through 20KV argon ion beams at angles of incidence of 10, 38, and 90 degrees. In some cases the red cells were rotated at about 2 rotations per minute in the ion beam. Etching time varied from 1 to 30 minutes. After etching, the cells were removed from the microscope and coated with carbon and gold palladium before being reinserted in the microscope for examination.
Ultrastructure of the Ascospores and Conidia of Venturia Inaequalis
Authors: Granett A. L.
Published: June 2020

Venturia inaequalis (Cke.) Wint. is the causal agent of scab,a worldwide disease of apples. There have been few electron microscopic investigations on any phase of this fungus. The studies reported herein were initiated to clarify some ultrastructural characteristics of ascospores and conidia.

In the spring ascospores develop within perithecia on decaying apple leaves from the previous year. Either whole perithecia were teased from leaves, or ascospores were isolated from leaves in an air tunnel device. Conidia develop on living leaves, blossoms, and fruits. Infected leaves were sprayed with distilled water and these spores were collected and concentrated into a pellet by low speed centrifugation. Perithecia, ascospores, and conidia were fixed in glutaraldehyde and osmium tetroxide; ultrathin sections were stained with uranyl acetate and lead citrate.
Fine Structure of Pollen Walls in Lychnis Alba and the Presence of Silicon
Authors: Crang Richard E.
Published: June 2020

Acid resistant components of the pollen wall and tapetal membrane in flowering plants have long been known to be composed of sporopollenin—a highly resistant mixture of organic compounds. Recent light microscopy and cytochemical analyses have led to the recognition that additional organic compounds comprise a significant part of these anther structures. However, comparatively little consideration has been given to the inorganic composition of the pollen exine and the morphologically similar tapetal membrane. Electron microscopy allows the morphological characterization of components and, when coupled with energy dispersive x-ray analysis, offers the opportunity to characterize elemental composition.
An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope
Authors: Parikh Mihir
Published: June 2020

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used
Fine Structure Changes Produced by Gastric Mucosal Irritants: Ethanol and Urea
Authors: Eastwood Gregory L. , Kirchner John P.
Published: June 2020

Many substances cause physiologic alterations in the gastric mucosa such that the subsequent back-diffusion of H+ ion leads to morphologic damage. To account for the abnormal permeability induced by gastric irritants, it has been suggested that the tight junctions between surface epithelial cells are loosened. However, since little is known regarding the fine structural effects of these substances, we performed the following studies using two recognized irritants, ethyl alcohol (EtOH) and urea.

Fasted adult male Swiss mice in groups of 3 mice each received via esophageal intubation one of the following solutions for 15 minutes: distilled water, 145 mN NaCl, 10% EtOH, 10% EtOH + 100 mN HCl, 25% EtOH, 25% EtOH + 100 mN HCl, 45 mN NaCl + 100 mN HCl, 900 mN urea, or 1500 mN urea.
Central Monoamine Neurons
Authors: Hökfelt T.
Published: June 2020

Considerable interest has been focused on a group of biologically highly active substances often called biogenic monoamines including dopamine (DA), noradrenaline (NA), adrenaline (A) and 5-hydroxytryptamine (5-HT). Initially their existence in various non-neuronal cell systems and their role as hormones called for extensive research efforts. Subsequently their possible involvement in neurotransmission both in the peripheral and central nervous system has been studied in laboratories all over the world.

Today a wide variety of methods are available for studies on monoamine neurons among others histochemical techniques at the light and electron microscopic level. These techniques have been of importance not only for identification and mapping of such neurons but also for the understanding of their physiological role(s) e.g. in brain function.
Spontaneous Activation of the Hamster Eggin vivo
Authors: Longo F. J.
Published: June 2020

Spontaneous activation of the hamster ovum is a normal occurence in oviducal eggs that are not inseminated. Many aspects comprising this process of parthenogenesis mimic events characteristic of fertilization and include for example, the formation of the second polar body and the development of one or two pronuclei. Occasionally the activated egg cleaves to form a two-cell stage. The similarity between the spontaneously activated hamster ovum and the inseminated egg has been previously documented at the light microscopic level of investigation; however, further investigation is warranted for the study of parthenogenesis in mammals provides an opportunity of elucidating developmental mechanisms of the fertilized egg. Accordingly, unfertilized eggs were flushed from the oviducts of hamsters at different intervals during the estrus cycle (6 to 70 hours postovulation), prepared for light and electron microscopy, and compared with fertilized eggs obtained at corresponding periods.
Measurements of Single-Stranded RNA From Foot-and-Mouth Disease Virus
Authors: Breese Sydney S. , Bachrach Howard L.
Published: June 2020

In the continuing study of the physical and chemical properties of purified foot-and-mouth disease virus (FMDV), particles were treated to release RNA strands by dialysis against demineralized distilled water. The RNA strands were mounted by loop drop on formvar carbon coated specimen grids pretreated with 0.1% bovine plasma albumin to give a protein spreading surface. Dilutions were made in demineralized distilled water to achieve the best concentration for subsequent measurements. Specimen grids were rotary shadowed at low angle with uranium. 2.5 to 3.0 X prints of electron micrographs taken of random fields at 8,000 to 11,000 X were used for measurements with a map-measuring device.

Samples were selected from supplies in long term storage which had been made according to methods outlined previously.
Manchette Microtubules of Mouse Spermatids and their Resistance to Pepsin Digestion
Authors: Wolosewick John J. , Bryan John H. D.
Published: June 2020

The manchette is a transitory microtubular complex associated with a spermatid nucleus during the morphopoietic events of spermiogenesis. Behnke and Forer provided evidence for four classes of microtubules (mts) in crane fly spermatids, rat sperm tails and tracheal cilia. Their observations also included the Sertoli cell and spermatid tail mts in rat testis, but they failed to mention the manchette mts. This present paper points out the distinct difference in stability or resistance to pepsin digestion between the manchette mts and other microtubular elements in the seminiferous epithelium of the mouse.

Testes of adult mice were removed from the’ animals after cervical dislocation and placed into 2.5% glutaraldehyde/Millonig's phosphate buffer (pH 7.2). Testicular capsules were gently split and separated, thus exposing the tubules. After 15 min.
The Ultrastructural Localization of Acid and Alkaline Phosphatase Via Sulfhydryl Reduction of a Nonosmiophilic Tetrazolium Salt to an Osmiophilic Formazan
Authors: Shannon W. Allen , Hoshino Yoshinobu , Seligman Arnold M.
Published: June 2020

The metal salt capture methods for acid phosphatase and alkaline phosphatase with numerous variations based principally on the Gomori method have been useful methods for direct cytochemical visualization of the enzymes. However, the possibilities of nonenzymatic deposition of reaction product, possible inhibition of enzymatic activities, and other suggested weaknesses of the methods which are found in the literature give reason to develop a new approach to the cytochemical localization of these enzymes. Other attempts along these lines have thus far been more or less partially successful. More recently Hanker et al. have demonstrated lysosomal hydrolases by the formation of osmium blacks based on synthetic substrates which initially deposit Hatchett's brown (cupric ferrocyanide) at the reactive sites. The synthetic substrate', 2-naph-thylthiolphosphate (NTP), developed by Seligman et al. to use in the demonstration of acid and alkaline phosphatase and subsequently used by Hanker et al.
The Ultrastructural Demonstration of a Fixative-Stable Dehydrogenase Acting on Leuco Nitroxyl Analogs
Authors: Shannon W. Allen , Wasserkrug Hannah L. , Plapinger Robert E. , Lynm Dwo , Seligman Arnold M.
Published: June 2020

A dehydrogenase which is relatively stable in formalin fixative and which reduces various leuco nitroxyl analogs is demonstrated cytochemically in rat myocardial, hepatic, and prostatic tubuloalveolar glandular cells.

The various tissues were extricated and fixed in phosphate-buffered formaldehyde for up to 1 hr. The substrates used were products produced by catalytic hydrogenation of four different compounds with stable nitroxyl free radicals (Fig. 1). These compounds were 4-hydroxy-2,2,6,6, tetramethyl piperidine-l-oxyl (I), the urethane derivative (II) formed by reacting compound I with phenylisocyanate, 4-amino-2,2,6,6, tetramethyl piperidine-l-oxyl (III), and 2,2,6,6, tetramethyl piperidine-l-oxyl (IV). The nonosmiophilic tetrazolium salt, 2-(2'-benzothiazolyl)-5-styryl-3-(4'-phthalhydrazidyl) tetrazolium chloride (BSPT), which produces an insoluble, osmiophilic formazan upon reduction, was used as the electron acceptor at pH 7.4. Following incubation in the reaction medium, the tissues were osmicated in 2% osmium tetroxide at 50°C for 2 hr.
Localization of RNA on Mitotic Chromosomes
Authors: Papsidero Lawrence D. , Braselton James P.
Published: June 2020

Thin sections of aldehyde fixed Cyperus alternifolius root tips were stained with uranyl acetate, washed with EDTA, and poststained with lead citrate to selectively stain ribonucleic acid (RNA) containing structures. As previously shown by other investigators RNA containing structures appeared electron dense, while nuclear regions known to contain DNA appeared less electron dense or “bleached”. RNase treatment removed all nuclear structures staining for RNA; light microscopic cytochemistry (Azure B) was performed on 1-3 micron sections of plastic embedded material to confirm the enzymatic removal of RNA.

Granular appearing fibrils with indistinct boundaries were observed at the periphery of bleached metaphase chromosomes (Fig. 1). These fibrils are similar to the ribonucleoprotein perichromatin fibrils observed by Monneron and Bernhard in interphase nuclei. Nucleolar remnants were also observed associated with metaphase chromosomes.
Epitaxially grown paraffin: An electron crystal structure analysis
Authors: Moss Barbara , Dorset Douglas L.
Published: June 2020

Epitaxial crystal growth proceeds in a manner entirely different from solution- growth. By a careful two-dimensional lattice matching in the substrate and the material of interest, crystallization in a desired orientation may be obtain. The area of each single microcrystal will, of course, depend upon the crystallinity of the substrate and the possibility of different growth directions thereon.

Epitaxy offers considerable advantages over solution growth, since resultant crystals give electron diffraction intensity data suitable for total structure determination. Crystallographic phasing techniques such as Patterson maps and direct methods rely upon the kinematic or single-scattering approximation. Their usefulness thus requires minimizing perturbations to the intensity data due to dynamical scattering and crystal bending. Diffracted beam amplitudes are most insensitive to crystal bends when the electron beam is parallel to a short unit cell dimension. Dynamical scattering effects are reduced if there are few repeat units in the beam direction, which requires very thin crystals. The value of this approach is illustrated with paraffin.
Phosphotungstic acid staining of latexes for transmission electron microscopy
Authors: Shaffer O. L. , El-Aasser M. S. , Vanderhoff J. W.
Published: June 2020

Measurement of particle size and particle morphology by transmission electron microscopy (TEM) is important in the characterization of polymer latex systems. Special sample treatment methods have been developed to permit the study of latexes that present problems, such as low-glass-transition-temperature (Tg) and electron-transparent particles. Some of these methods include hardening and staining by osmium tetroxide or bromine of latexes that contain unsaturation, negative staining by uranyl acetate, and freezing of latexes with low glass-transition temperatures.

We have recently found phosphotungstic acid (PTA) to be useful in both negative and positive staining of latex particles. As a negative stain, PTA can enhance the contrast between the electron-transparent particles and the dense PTA-stained background. This has been particularly useful with latexes such as poly(butyl acrylate), poly(ethyl acrylate), poly(ethylene), and other polymers of similar electron densities. As a positive stain, PTA can also react with the surface functional groups of particles, such as hydroxyl, carboxyl, and amine groups.
A modified replication technique to study the morphology of cured epoxy resin
Authors: Gupta V. B. , Drzal L. T. , Omlor R.
Published: June 2020

There is a great deal of interest in the study of the morphology of cured epoxy resin. Generally the surfaces of the cured samples or fracture surfaces, unetched or suitably etched, are examined on the transmission electron microscope using the two-stage replica method. The replicating fluid commonly used is 25% polyacrylic acid (MW ∼ 250,000) solution in water. It dries to a brittle replica which is removed by mechanical prying with the help of tweezers; extreme caution is required to ensure that it is not damaged. It has been shown that for fractographic studies of epoxy resin, replication based on PAA can give rise to artifacts and hence it is necessary to back it uo with other evidence, e.g. from the SEM. The standard replicating fluid, containing 10% cellulose acetate in acetone, gives a softer and easily removable replica but the acetone can affect the surface of epoxy resin. To circumvent the latter problem, a modified replication method was developed and is described here.
Faceted grain boundaries in Al2O3
Authors: Morrissey K. J. , Carter C. B.
Published: June 2020

The occurrence of faceted grain boundaries in commercially produced Al2O3 is quite common. This type of boundary has been noted previously, but little structural information has been reported. The different types of faceted boundary include twin boundaries, special high-angle boundaries, and lowangle grain boundaries. Faceted interfaces between Al2O3 grains and secondphase particles have been briefly discussed elsewhere. The present work is concerned mainly with the crystallography of special high-angle boundaries and twins.

The planes of the facets can be understood using the concepts of the O-lattice and the CSL, which have been successfully used to study metals and semiconductors. Wagner, Tan, and Balluffi have proposed the generalized CSL, in which the coincident lattice sites in the two grains need neither be identical nor be occupied by atoms. It is in this sense that the CSL model will be used in this work.
Microtomy of spherical Al2O3 powders
Authors: Jenkins E.J. , Tucker D.S. , Hren J.J.
Published: June 2020

The size range of mineral and ceramic particles of one to a few microns is awkward to prepare for examination by TEM. Electrons can be transmitted through smaller particles directly and larger particles can be thinned by crushing and dispersion onto a substrate or by embedding in a film followed by ion milling. Attempts at dispersion onto a thin film substrate often result in particle aggregation by van der Waals attraction. In the present work we studied 1-10 μm diameter Al2O3 spheres which were transformed from the amprphous state to the stable α phase.

After the appropriate heat treatment, the spherical powders were embedded in as high a density as practicable in a hard EPON, and then microtomed into thin sections. There are several advantages to this method. Obviously, this is a rapid and convenient means to study the microstructure of serial slices. EDS, ELS, and diffraction studies are also considerably more informative. Furthermore, confidence in sampling reliability is considerably enhanced. The major negative feature is some distortion of the microstructure inherent to the microtoming operation; however, this appears to have been surprisingly small. The details of the method and some typical results follow.
The spatial resolution limit of electron lithography
Authors: Joy David C
Published: June 2020

As the size of microcircuit elements continues to decrease it is important to attempt to determine what factors ultimately limit the width of the finest line that could be fabricated by electron lithography and conventional polymer resists. Since the line profiles in an exposed and developed resist are determined by the contours of equal absorbed energy density this can be done by modelling the scattering which occurs in the polymer. We consider here the idealised case of a thin resist layer supported on a substrate of negligible scattering power, and irradiated with a beam of electrons in the energy range 30 to 100 keV, and calculate the minimum line width attainable under these optimum conditions.

In the absence of any backscattering from the substrate it might be expected that the energy deposition profiles would be determined by elastic scattering in the resist.