bluuebunny/crossref_metadata_2025 huggingface dataset:
Viropexis and Phagocytosis of Type B (Mouse Mammary Tumor) Virus Particles in vivo
Authors: Seman Gabriel , Dmochowski Leon
Published: June 2020

Electron microscope examination of spleen tumors of RIII/Dm female mice with reticulum cell sarcoma revealed the presence of extracellular and budding type C, type B, and intracytoplasmic type A virus particles. Penetration of type B particles into cytoplasm of tumor cells has been observed. It consisted of inclusion of the particles into pinocytotic vesicles and of the release of the nucleoids into the cytoplasmic matrix. They were frequently seen penetrating into tumor cells producing type C or intracytoplasmic type A particles at the same time (Figs. 1 and 2). A similar penetration of other viruses into cells in vitro has been described as viropexis.
Continuous Production of Type “C” Particles from a Cell Line Derived from a Transplanted Testicular Tumor
Authors: Sarkar Nurul H. , Lasfargues Etienne Y. , Moore Dan H.
Published: June 2020

Large inclusions of intracytoplasmic A particles in the cytoplasm of estrogen-induced interstitial cell tumors of mouse testicles have been described. It has been shown that A particles in these tumors are antigenically related to the soluble antigen of the mouse mammary tumor virus. It was our interest to maintain these tumor cells in tissue culture as a constant source of A particles to be isolated and studied for their biophysical and biochemical properties.

One mouse with testicular tumor was obtained through the courtesy of Dr. W. U. Gardner (Yale Univ. School of Med., Conn.). The tumor was minced, trypsinized and a cell line (GTT) was established (E.Y. Lasfargues and W. Coutinho, 1969 unpublished).
Scanning Studies of Cell Surfaces
Authors: Fonte Virginia , Weller Nancy , Porter Keith R.
Published: June 2020

The surfaces of a cell in its topography and anti-genicity expresses subtle variations in the effective genome, as well as the physiology and structural organization of the underlying cytoplasm. Understanding the relationship of these various factors to the surface depends in part on obtaining a detailed characterization of the topography of cells and how this topography changes with phases in the cell cycle, with transformation to malignancy and with the cell's response to such physiologically active agents as cyclic AMP.

We have therefore explored the usefulness of the scanning electron microscope in investigations of the cell's topography. Cells grown under favourable in vitro conditions have been fixed in glutaraldehyde, dehydrated in acetone and dried by the critical point method of Anderson.
The Fine Structure of Rat Renal Microbodies and Cytoplasmic Bodies Following Perfusion Fixation
Authors: Barrett J. M. , Heidger P. M.
Published: June 2020

Microbodies have received extensive morphological and cytochemical investigation since they were first described by Rhodin in 1954. To our knowledge, however, all investigations of microbodies and cytoplasmic bodies of rat renal proximal tubule cells have employed immersion fixation. Tisher, et al. have shown convincing evidence of fine structural alteration of microbodies in rhesus monkey kidney following immersion fixation; these alterations were not encountered when in vivo intravascular perfusion was employed. In view of these studies, and the fact that techniques for perfusion fixation have been established specifically for the rat kidney by Maunsbach, it seemed desirable to employ perfusion fixation to study the fine structure and distribution of microbodies and cytoplasmic bodies within the rat renal proximal tubule.
Observations on the Vierergruppe during Spermiogenesis in Equisetum
Authors: Polette T. , Ridgway J.
Published: June 2020

The occurrence of a multi-layered structure and a raicrotubular sheath have been enumerated for the spermatids of various lower plants. These structures, Vierergruppe (V) and Spline (S) respectively, do not show the strict conjunction with the nuclear membrane in Equisetum as previously reported. Although associated with the nuclear and plasma membranes, the Vierergruppe and Soline generally are found underlying the plasma membrane with the Spline encircling the cell in a spiral sheath, (Fig. 1). At either ends of the cell are the Vierergruope and associated mitochondria connected by the spiral Spline, with one extremely large mitochondrion having cristae in parallel array to the layers of the Vierergruppe.

Clearly reaffirming mitochondrial association, the Vierergruppe have been observed on either side of another extremely large mitochondrion (M) (Fiq. 4.).
Arrangement of Mitochondria in Spermatozoa of the Mexican Axolotl, Ambystoma Mexicanum
Authors: Keyhani Ezzatollah , Lemanski Larry F. , Lemanski Sharon L.
Published: June 2020

Energy for sperm motility is provided by both glycolytic and respiratory pathways. Mitochondria are involved in the latter pathway and conserve energy of substrate oxidation by coupling to phosphorylation. During spermatogenesis, the mitochondria undergo extensive transformation which in many species leads to the formation of a nebemkem. The nebemkem subsequently forms into a helix around the axial filament complex in the middle piece of spermatozoa.

Immature spermatozoa of axolotls contain numerous small spherical mitochondria which are randomly distributed throughout the cytoplasm (Fig. 1). As maturation progresses, the mitochondria appear to migrate to the middle piece region where they become tightly packed to form a crystalline-like sheath. The cytoplasm in this region is no longer abundant (Fig. 2) and the plasma membrane is now closely apposed to the outside of the mitochondrial layer.
The Fine Structure of Primordial Germ Cells of the Rat
Authors: Eddy E. M.
Published: June 2020

Primordial germ cells are readily recognizable in embryos of the rat due to their large size, generally rounded shape and prominent nuclei with uniformly dispersed heterochromatin. They often have blunted pseudopodal processes at one end and small ruffles or trailing processes at the other, characteristics expected from their known ameboid activity- and migratory abilities. Also, the cytoplasm is rich in polyribosomes and contains a modest amount of rough endoplasmic reticulum and the mitochondria are frequently larger and less dense than those of adjacent somatic cells.

In addition to these general characteristics, there are features unique to germ cells which allow them to be identified with certainty. These are: 1) small vesicles containing an irregular, dense core and 2) discrete accumulations of fibrous material known as nuage. Both of these features are present in other species and at other times in the life history of germ cells. The dense-cored vesicles have been noted in fetal and early postnatal mouse oogonia and oocytes, and in hamster and rabbit oocytes.
Surface Changes of Arachnoid Granulations With Varying Pressure Gradients A Scanning Electron Microscope Study
Authors: Gomez D. G. , Potts D. G. , Perecko J. P.
Published: June 2020

Most current ultrastructural studies of the arachnoid villi and granulations in mammals have not taken into account the maintenance of constant pressure gradients during perfusion and fixation showing arachnoid villi and granulations partially or totally collapsed. Recent ultrastructural studies of monkey arachnoid villi fixed at different pressure gradients showed that the endothelial cells covering the villi were flatter and further apart with shorter cell-to-cell overlappings as the gradient was increased. The spaces between these endothelial cells appeared irregular and widened possibly increasing the passive passage of cerebrospinal fluid across the villi and granulations. It has been also shown that during physiologically occurring positional changes in living animals the normally existing pressure gradient remained almost Constant.
Vascular Leakage of Horseradish Peroxidase Following Acute Spinal Cord Injury
Authors: Beggs John L. , Waggener John D.
Published: June 2020

Under normal CNS conditions, circulating horseradish peroxidase (HRP) fails to enter the perivascular spaces due to the presence of interendothelial tight junctions and the absence or low rate of pinocytotic activity. Under some conditions where the blood brain barrier (BBB) is altered, HRP leakage occurs. Possible routes of HRP leakage include increased pinocytotic activity, breakdown of the interendothelial tight junctions, and direct penetration across severely damaged endothelial cells. The modes of leakage may vary with the type of insult.

Following acute compression of upper thoracic spinal cord (cat), leakage and distribution of HRP is confined to the posterocentral gray matter with minimal involvement of white matter (Fig. 1).
Comparison Between Regional Cerebral Ischemia and Total Cerebral Ischemia. an Ultrastructural Study in the Cat
Authors: Garcia Julio H. , Kalimo Hannu , Kamijyo Yoshinari , Lessler Mary Jane , Trump Benjamin F.
Published: June 2020

It has been suggested that cerebral cellular changes in regional cerebral ischemia, resulting from occlusion of a cerebral artery, are structurally indistinguishable from those occurring after total cerebral ischemia, resulting from total cessation of cerebral circulation.

Significant differences were detected in these two forms of circulatory impairment, which we produced in cats, as follows: a) regional cerebral ischemia by clipping a middle cerebral artery (MCA); b) total cerebral ischemia by filling the intracerebral vasculature with Eagle's minimum essential medium containing 6°U dextran (mw. 80,000) at 37°C. Both experiments lasted 60 minutes, and then the brain was fixed by perfusion with aldehydes. Completeness of perfusion was verified by including carbon black in the final 200 cc of aldehyde perfusate, which revealed even distribution through the capillary bed.
Effects of TRH on Pituitary Grafts in the Rat
Authors: Shiino Masataka , Rennels Edward G.
Published: June 2020

To date, many investigations have been reported on the ultrastructure of the “thyrotroph”. However, there is still confusion in regard to the ultrastructure of this cell type.

In the present study, we observed ultrastructural alterations of anterior pituitary grafts following chronic treatment of the animals with synthetic thyrotrophin releasing hormone (TRH) (Schwarz-Mann). Male, Sprague- Dawley derived rats were hypophysectomized at 40 days of age. Seven days after the operation the anterior pituitary gland from a littermate male rat was transplanted under the kidney capsule. Thirty days following the transplantation, 100 pg of TRH was injected subcutaneously twice daily for 15 days (9:00 am and 4:00 pm). TRH was dissolved in 3% gelatin-saline solution at a concentration of 100 pg/0. 1 ml for each injection. As controls, hypophysectomized male rats with pituitary grafts were injected with 3% gelatin-saline solution by the same procedure.
Fine Structural Features of Pineal Gland Development
Authors: Sheridan Michael N. , Walker Susan H.
Published: June 2020

The pineal gland develops as an evagination from the roof of the diencephalcn. In many mammals, the definitive location of the structure is at the apex of the pineal recess, rostral to the posterior commissure and caudal to the habenular commissure. In most rodents the pineal migrates dorsocaudally and assumes a position just beneath the skull nesseled in a pocket of dura mater near the venous sinus confluence. The pineal gland of the golden hamster is unique in that the original single evagination divides into two parts; one, the superficial pineal positioned at the venous sinus confluence and two, the deep pineal remaining at the apex of the pineal recess (Sheridan and Reiter, 1970). We have studied pineal gland development at daily intervals in the hamster from birth up through the third postnatal week. Division of the gland into its components is complete at the middle of the second postnatal week.
A study of the fracture surface of cured epoxy resin
Authors: Gupta V. B. , Drzal L. T. , Chen Y. L.
Published: June 2020

The dependence of the fracture behavior of cured epoxy resin on its morphology is an area of interest and controversy. It is believed that the resin is heterogeneous, comprising spherical entities of high crosslink density in a matrix of relatively lower crosslink density. These heterogeneities have quite a wide size distribution, predominantly in the 10 to 50nm range and are believed to be aggregates of a few elementary entities of around 5nm in diameter. Since the fracture pattern has been observed to be around the boundary of the aggregate rather than through it, it is important to understand how these larger entities influence the fracture behavior. Hence the present study was designed to map the size distribution of aggregates which will henceforth be referred to as nodules. Although it has been pointed out that scanning electron microscopy is more suited for the study of polymer fractography than transmission electron microscopy, there has been a much greater use of TEM employing the replica method in morphological investigations of cured epoxy resins. It will be shown here that if suitable specimens are used, the morphology of cured epoxy resins can be studied with SEM.
Precipitation of ϕ1-CaZr4O99 and ϕ-Ca6Zr19O44 in calcia-stabilized zirconia
Authors: Hangas J. W. , Mitchell T. E. , Heuer A. H.
Published: June 2020

CaO stabilizes the high temperature cubic phase field of ZrO2 resulting in an eutectoid reaction at 1140°C, as shown in Fig. 1. Two ordered defect structures are known to occur in the zirconia-calcia system on the hypereutectoid side of the cubic phase field. One is a monoclinic precipitate called ϕ1 with the composition of CaZr4O9, whereas the other is a rhombohedral precipitates (R3c) called ϕ2 which has a composition of Ca6Zr19O99. The names of the precipitates are derived from analogous structures in the calcia-hafnia system, and these structures are described by Allpress, et al., The present study has been designed to use TEM to describe the microstructures more fully.
Microstructure of TiB2liquid phase sintered with Ni3Al
Authors: Angelini P. , Bentley J. , Finch C. B. , Sklad P. S.
Published: June 2020

TiB2is a ceramic material which possesses exceptional thermal, chemical, and electrical properties. Commercial powders can be formed into bulk pieces by hot pressing at temperatures near 2000°C. However, this produces excessive grain growth which can lead to cracking and low mechanical integrity due to the relatively large anisotropic thermal expansion of the TiB2grains. Liquid phase sintering can be used to produce structural forms of TiB2by hot pressing at temperatures near 1450°C. This process limits the TiB2grain growth but introduces an intergranular phase. Previous work used Ni as a binder and under most hot-pressing conditions this resulted in the formation of a Ni3B intergranular phase. Additional binders are being considered to understand the phase development during liquid-phase sintering and to improve the properties of the bonded TiB2forms.

The present research concerns the use of Ni3Al as a binder for TiB2. The Ni3Al powder was a physical mixture of 32 wt % NiAl and 68 wt % of a solid solution of 95 at. % Ni with 5 at. % Al powders.
Transmission electron microscopy of rapidly solidified micron-size carbide powders of titanium and zirconium
Authors: Pande C. S. , Smith S.
Published: June 2020

It is well known that rapid solidification in materials may result in unique microstructure and properties. These novel features are determined largely by the transport processes occurring at the liquid/solid interface. However, a detailed study of the basic mechanism of rapid solidification and its correlation with resultant chemistry and microstructure is needed to fully utilize the potential benefits of rapid solidification processing. We have used transmission electron microscopy, and related techniques such as energy dispersive x-ray analysis in thin films and electron energy loss analysis for this study. The material chosen for this purpose was rapidly solidified very fine carbide powders of titanium and zirconium.

The method of producing these powders using spark machining has been described in detail elsewhere. The carbide is formed during the machining of the metal due to a reaction between the metal and carbon from kerosene which is used as a dielectric for spark machining. The rate of solidification and the carbon content of the carbides can be varied by varying the frequency and polarity of the electric discharge.
Microfabrication research at the National Submicron Facility
Authors: Wolf E.D.
Published: June 2020

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.
Ultra-high resolution electron-beam lithography with a research scanning electron microscope
Authors: Craighead H. G.
Published: June 2020

An electron microscope of the type normally used for analysis has been employed as an experimental beam writing instrument. With this instrument less than 10 nm size structures have been fabricated in a variety of materials by electron beam lithography. The important parameters that determine the resolution limit are: electron beam probe size, electron beam energy, characteristics of the beam sensitive material and the nature of the substrate. These parameters were studied with a Philips 400 T TEM/STEM/SEM modified for external beam control and interfaced to a DEC MINC 11-23 computer for pattern generation. With this microscope's ability to image thick samples by secondary and backscattered electron detection conventional type lithography was done on semiconductor substrates. The general lithographic technique is described, for example, in reference 2. In addition fabrication techniques on thin films were studied. The effect of the resolution determining parameters and several examples of lithographic results are described in this paper.
Redistribution and precipitation of dopant on thermal annealing of bismuth implanted silicon
Authors: Pennycook S. J. , Narayan J. , Holland O. W.
Published: June 2020

Ion implantation above a certain dose leads to the formation of amorphous layers, which if recrystallized under interface-controlled growth at 450-600°C, result in solid solutions far exceeding the equilibrium solubility limits. In this investigation, we have annealed high-dose implanted specimens at 1000°C for one hour to study the redistribution and precipitation of dopant due to the presence of extended defects.

Figure 1 shows a cross section TEM image taken near the [01] Si pole of (100)Si implanted with 209Bi+ (250 KeV, 5 x 1015 cm−2) and annealed (1000°C, 1 hr). As well as a band of precipitates typically 5 nm in size centered at a depth of 100 nm there are some much larger precipitates (28 nm in size) at the original surface of the silicon. These show a curved meniscus protruding out of the surface since the bismuth is liquid at the annealing temperature. These precipitates are located on twins suggesting that the dopant has diffused along the twin boundaries from the band of high concentration to the surface.
New precipitate morphology in heat treated CZ Si wafers
Authors: TSAI H.L. , CARPENTER R.W.
Published: June 2020

The morphological forms of the precipitates and other defects in the heat-treated oxygen-containing CZ silicon have been extensively documented, but little information concerning the morphology as a function of the position in the ingot has been reported. Recent studies, using high resolution analytical electron microscopy, have shown that plate type precipitates observed in the seed end of the silicon ingot were amorphous and contain oxygen. We have carried out a detailed TEM study of the precipitate morphology in the heat-treated wafers cut from the seed, middle, and tang regions of the CZ ingot. The interstitial oxygen concentrations in the as grown Si were 2.1×1018cm−3, 1.6×10−18cm−3, and 1.5×1018cm−3in the seed, middle and tang regions, respectively. Initial carbon was below IR detectability limit, but was higher in the tail than seed, based on segregation coefficients. The wafers were subjected to two-step anneals: 1. 0-16 hrs., 800°C in nitrogen and 2. 16 hrs., 1050°C in dry oxygen.
The study of interfacial reactions of nickel thin films on GaAs
Authors: Chen L.J. , Hsieh Y.F.
Published: June 2020

One measure of the maturity of a device technology is the ease and reliability of applying contact metallurgy. Compared to metal contact of silicon, the status of GaAs metallization is still at its primitive stage. With the advent of GaAs MESFET and integrated circuits, very stringent requirements were placed on their metal contacts. During the past few years, extensive researches have been conducted in the area of Au-Ge-Ni in order to lower contact resistances and improve uniformity. In this paper, we report the results of TEM study of interfacial reactions between Ni and GaAs as part of the attempt to understand the role of nickel in Au-Ge-Ni contact of GaAs.

N-type, Si-doped, (001) oriented GaAs wafers, 15 mil in thickness, were grown by gradient-freeze method. Nickel thin films, 300Å in thickness, were e-gun deposited on GaAs wafers. The samples were then annealed in dry N2 in a 3-zone diffusion furnace at temperatures 200°C - 600°C for 5-180 minutes. Thin foils for TEM examinations were prepared by chemical polishing from the GaA.s side. TEM investigations were performed with JE0L- 100B and JE0L-200CX electron microscopes.
EBIC microscopy for the characterization of semiconductor materials and devices
Authors: Varker C. J.
Published: June 2020

For dislocation-free silicon crystals, defects generated during semiconductor device fabrication processes are often the end result of inhomogeneities formed during crystal growth. Impurity-point defect complexes are often transformed into a variety of microdefects during subsequent thermal processing. Extensive investigations have been published on the analysis of microdefects such as stacking faults, complex dislocation colonies and impurity precipitates in silicon crystals. For crystals grown with the Czochralski method, oxygen and carbon have been the subject of many recent investigations. Oxygen precipitation during thermal annealing has been identified as a dominant cause of minority carrier lifetime degradation. The investigative methods used in the majority of these studies include: transmission electro microscopy, scanning electron microscopy, I.R. absorption spectroscopy, X-ray transmission methods and chemical decoration etching.

Conventional electron microscopy provides no direct information on the relationship between defects in crystals and electrical effects in semiconductor devices.
Spinodal decomposition microstructures in synthetic pyroxenes
Authors: Nord Gordon L. , McCallister Robert H.
Published: June 2020

Pyroxenes (Na,Ca,Mg,Fe,Al)SiO3, are common rock-forming minerals. They are particularly important in that they record igneous and high-grade metamorphic processes in the terrestrial and lunar crust as well as deformational processes in the terrestrial mantle. Pyroxenes are also abundant in both meteorites and extraterrestrial dust. The pyroxene structure consists of tetrahedral chains of SiO3 units that occur in layers parallel to (100). Between the tetrahedral layers lie octahedral layers that contain the cations. There are three important space groups in the Ca, Mg, Fe pyroxenes. Symmetry changes between structure types are the result of various stacking sequences of the octahedral layers and/or of symmetrically-distinct tetrahedral chains. Because of the size difference between Ca (1.14Å) and Mg.Fe (0.86Å, 0.75Å) the pyroxene subsolidus is dominated by a miscibility gap that separates Ca-rich pyroxenes from Ca-poor pyroxenes. The presence of several structure types, an extensive miscibility gap and the universal abundance of pyroxene minerals in rocks combine to form an important mineral system that has high potential for deciphering pressure and temperature of formation as well as subsequent cooling and decompression rates of important rock bodies.
Identification of preferential polishing effects using broad-probe AEM
Authors: Maziasz P. J.
Published: June 2020

Many applications of AEM (XEDS or EELS) in multiphase alloys demand the highest spatial resolution microanalysis, hence minimum probe size and thin (50-75 nm) foils. The quantitative elemental analyses, however, can be misleading if preferential polishing has occurred causing exaggeration or even removal of microstructural/microcompositional features. In this study, a large probe or “broad-beam” XEDS technique was employed to detect and identify preferential polishing effects. The broad-beam technique yields a “bulk” analysis, which, ideally, should be equivalent to the bulk chemical analysis. The XEDS analyses were performed with a JEM 120CX AEM equipped with a Kevex detector. Spectra were quantified with an ORTEC-EEDSII computer/multichannel analyzer employing the standardless technique and absorption correction (where necessary, following Tixier and Philibert) with programs developed by Zaluzec. Matrix analysis were made in a spot mode and “bulk” analyses were made with a broad, elliptically stigmated probe (∼10μm major axis), with the major axis parallel to the foil edge to minimize thickness variations in the analyzed volume.
Effects of cooling rate on the mechanical properties of dual phase treated vanadium steels
Authors: Chen L.J. , Cheng H.C. , Gong J.R. , Yang J.G.
Published: June 2020

For fuel savings as well as energy and resource requirement, high strength low alloy steels (HSLA) are of particular interest to automobile industry because of the potential weight reduction which can be achieved by using thinner section of these steels to carry the same load and thus to improve the fuel mileage. Dual phase treatment has been utilized to obtain superior strength and ductility combinations compared to the HSLA of identical composition. Recently, cooling rate following heat treatment was found to be important to the tensile properties of the dual phase steels. In this paper, we report the results of the investigation of cooling rate on the microstructures and mechanical properties of several vanadium HSLA steels.

The steels with composition (in weight percent) listed below were supplied by China Steel Corporation: 1. low V steel (0.11C, 0.65Si, 1.63Mn, 0.015P, 0.008S, 0.084Aℓ, 0.004V), 2. 0.059V steel (0.13C, 0.62S1, 1.59Mn, 0.012P, 0.008S, 0.065Aℓ, 0.059V), 3. 0.10V steel (0.11C, 0.58Si, 1.58Mn, 0.017P, 0.008S, 0.068Aℓ, 0.10V).
Fracture toughness relationships in a low-alloy steel
Authors: Padmanabhan R. , Wood W. E.
Published: June 2020

Utilization of high austenitization temperatures to improve fracture toughness of UHSLA steels at similar strength levels has received considerable interest. However, these heat treatments result in reduced ductility and impact toughness. This inverse response of impact and plane strain fracture toughness is essentially due to microstructural effects and it is possible to achieve simultaneous improvements in all these properties through controlled variations in the microstructure.

A vacuum remelted Si-modified 4340 steel was chosen for this study under three heat treated conditions, viz., conventional, high temperature and step with austenitization temperatures of 1143 K (1 hr), 1473 K (1 hr) and 1473 K (1 hr) furnace cooled to 1143 K (5 min), respectively. All samples were quenched in oil and tempered at 553 K (1 hr). A modified conventional heat treatment was also designed to achieve a desired microstructure with a 1143 K (1 hr) austenitization, a 923 K (1 hr) intermediate temper (after oil quenching), a 1123 K (3 min) reaustenitization and a final 553 K (1 hr) temper (after requenching) steps.
Coherency loss in γ' precipitates in nickel-base superalloy
Authors: Ricks R. A. , Porter Angus J.
Published: June 2020

During a recent investigation concerning the growth of γ' precipitates in nickel-base superalloys it was observed that the sign of the lattice mismatch between the coherent particles and the matrix (γ) was important in determining the ease with which matrix dislocations could be incorporated into the interface to relieve coherency strains. Thus alloys with a negative misfit (ie. the γ' lattice parameter was smaller than the matrix) could lose coherency easily and γ/γ' interfaces would exhibit regularly spaced networks of dislocations, as shown in figure 1 for the case of Nimonic 115 (misfit = -0.15%). In contrast, γ' particles in alloys with a positive misfit could grow to a large size and not show any such dislocation arrangements in the interface, thus indicating that coherency had not been lost. Figure 2 depicts a large γ' precipitate in Nimonic 80A (misfit = +0.32%) showing few interfacial dislocations.
Phase chemistries in a precipitation-strengthened superalloy
Authors: Hall E. L. , Kouh Y. M. , Chang K. M.
Published: June 2020

The majority of Ni-base superalloys are strengthened by precipitation of the γ' phase, which has a coherent ordered Ll2 structure based on Ni3(Al,Ti). However, a few superalloys, most notably Inconel 718, are strengthened instead by a γ" phase, which is a metastable coherent ordered DO22 precipitate with a tetragonal unit cell and nominal stoichiometry Ni3(Nb,Ta). The γ' phase generally precipitates homogeneously in the form of spheres or cubes, whereas the γ" phase occurs as disks with the (001) γ" plane parallel to one of the {100} planes of the cubic matrix. Thus, three variants of γ" are possible. The γ" phase is generally metastable and is replaced on extended aging by the δ phase, which is also Ni3(Nb,Ta) but which has a Cu3Ti-ordered orthorhombic structure.

It has been shown that the type of precipitate formed in Ni-base alloys is a sensitive function of overall alloy chemistry. In particular, the Ti+Al/Nb+Ta ratio has a strong effect, with increases in this ratio favoring γ and decreases γ'.
The crystal morphology of 2:17 rare-earth cobalt permanent magnets
Authors: Hadjipanayis G. C. , K. R.
Published: June 2020

Precipitation hardened Sm2(Co,Fe,Cu,Zr)17 permanent magnets are of great technological importance because of their large coercive fields (Hc∽ 6-15 kOe) and energy products ((BH)m ∽ 25-30 MGOe). The hard magnetic properties of these magnets are usually achieved after a complex heat treatment. The samples are first sintered at 1200 C and then quenched to room temperature. The sintered magnets are aged at around 830 C, slowly cooled to 400 C and then quenched again to room temperature. Microstructure studies have been reported on several 2:17 magnets at their optimum state. The purpose of this study is to examine the changes in the microstructure that are produced by the described heat treatment and determine how they affect the hard magnetic properties of the magnets. Samples of a commercial TDK REC-26 magnet (Sm(Co,Fe,Cu,Zr)7.5) were prepared at different stages of the heat treatment. Electropolishing together with ion thinning were used to prepare the specimens for transmission electron microscopy. The microstructure observations were made with a Philips 400 TEM equipped with an energy dispersive x-ray analysis unit.
In situ annealing of aluminum ion-implanted with molybdenum
Authors: Bentley J. , Stephenson L. D. , Benson R. B. , Parrish P. A.
Published: June 2020

As part of an analytical electron microscopy study of aluminum ion-implanted with molybdenum, in situ annealing experiments have been performed to better understand the phase transformation mechanisms in material with a peak molybdenum content of approximately 11 at. % Mo. Ion implantations were performed at the Naval Research Laboratory on electropolished coupons 38 × 28 × 0.5 mm of 99.999% Al with 0.5 mm grain size. A dual energy implant schedule of 1.12 × 1020 ions/m2 at 50 keV. plus 1.24 × 1020 ions/m2 at 110 keV was employed. The TEM specimens were prepared by electrodischarge machining 3-mm diameter disks from the implanted coupons and backthinning by electropolishing. In situ annealing was performed in a Philips EM 400T/FEG with the use of a Philips single-tilt heating holder. Videotape recordings were made from the TEM fluorescent viewing screen in the tilted position.

A high concentration of small dislocation loops and possibly a tangled dislocation network were present in the as-implanted material. No precipitates were observed; this is consistent with a supersaturated solid solution.
Decomposition of the metastable beta titanium alloy Ti-15-3
Authors: Chen Y. L. , Fujlshiro S.
Published: June 2020

Metastable beta titanium alloys have been known to have numerous advantages such as cold formability, high strength, good fracture resistance, deep hardenability, and cost effectiveness. Very high strength is obtainable by precipitation of the hexagonal alpha phase in a bcc beta matrix in these alloys. Precipitation hardening in the metastable beta alloys may also result from the formation of transition phases such as omega phase. Ti-15-3 (Ti-15V- 3Cr-3Al-3Sn) has been developed recently by TIMET and USAF for low cost sheet metal applications. The purpose of the present study was to examine the aging characteristics in this alloy.

The composition of the as-received material is: 14.7 V, 3.14 Cr, 3.05 Al, 2.26 Sn, and 0.145 Fe. The beta transus temperature as determined by optical metallographic method was about 770°C. Specimen coupons were prepared from a mill-annealed 1.2 mm thick sheet, and solution treated at 827°C for 2 hr in argon, then water quenched. Aging was also done in argon at temperatures ranging from 316 to 616°C for various times.
Rocking curves for specular reflection from crystal surfaces in the TEM
Authors: Turner P. S. , Eades J. A.
Published: June 2020

In transmission electron microscopy, electron diffraction is most frequently undertaken in the “Laue condition” (i.e. the electron beam entering one surface of a parallel sided slab and leaving through the opposite surface) or some approximation to it. In contrast, surfaces studies by RHEED are carried out in the “Bragg condition” (i.e. the electron beam enters and leaves through the same surface of the crystal and the Bragg reflection is from planes parallel rather than perpendicular to the surface).

Now that high quality images from surfaces are being obtained in reflection e.g., Yagi, it is appropriate to develop diffraction techniques for the Bragg condition in the electron miroscope; there are many examples of such work in RHEED equipment e.g. The symmetric Bragg condition is obtained when the incident and diffracted beams make the same angle with the specimen surface; this is specular reflection. Thus to obtain a rocking curve in the symmetric Bragg case requires variation of both the incident beam angle and the take off angle. This is not practical in an unmodified microscope.
Attractive and repulsive forces between clusters: A STEM study of platinum clusters
Authors: Chen E. G. , Ohtsuki M. , Crewe A. V.
Published: June 2020

Zanghi et al. measured the radial distribution functions of gold clusters on a KC1 substrate before and after annealing, and interpreted their results as indicating that a repulsive force exists between each pair of clusters. However, these results may be insufficient to explain the clustering phenomenon in all cases. For instance if this were the only force involved then coalescence could not occur. However, coalescence always occurs in the forming of thin films.

We present experimental results and some theoretical considerations of the interactive forces applied to the clustering of platinum deposited on a thin carbon film of about 20Å thickness. The ultra high vacuum (UHV)-STEM and digital image processor were used for the measurements of the size (d) and edge to edge (r-d) distributions (see Fig. 1).
A thin-section technique for transmission electron microscopy of catalysts
Authors: Hall J. B. , Hruskoci P. P.
Published: June 2020

Transmission electron microscopy (TEM) is often used to image the different phases, the metal dispersion, and the pore structure of heterogeneous catalysts. Although fine particle dispersion ts the most common sample preparation method because of its simplicity, it suffers from a paucity of sample areas which are thin enough. A less common technique for catalysts is thin sectioning. Sprys et al reported that the thin section technique is prohibitively expensive due to damage to the diamond knife, although Sawruk et al reported satisfactory results using a diamond knife with a relatively large angle (55°). An improved thin section technique has been developed for catalysts which has proven to be practical and efficient. Three catalysts have been used to evaluate and compare these preparation techniques.

The fine particle dispersion technique used in this evaluation involves spraying a suspension of the finely ground catalyst onto a holey Triafol film covered grid.3 Figure 1 is a SFM micrograph of an area of a TEM grid with a catalyst sample prepared by this technique. Most of the particles lying on the holey film are obviously too thick for TEM.
Electron-diffraction studies in synthetic polymer materials
Authors: Grubb D.T.
Published: June 2020

Diffraction studies in polymeric and other beam sensitive materials may bring to mind the many experiments where diffracted intensity has been used as a measure of the electron dose required to destroy fine structure in the TEM. But this paper is concerned with a range of cases where the diffraction pattern itself contains the important information.

In the first case, electron diffraction from paraffins, degraded polyethylene and polyethylene single crystals, all the samples are highly ordered, and their crystallographic structure is well known. The diffraction patterns fade on irradiation and may also change considerably in a-spacing, increasing the unit cell volume on irradiation. The effect is large and continuous far C94H190 paraffin and for PE, while for shorter chains to C 28H58 the change is less, levelling off at high dose, Fig.l. It is also found that the change in a-spacing increases at higher dose rates and at higher irradiation temperatures.
Light element analysis of irradiation-induced precipitates in Ti-modified 316 stainless steel
Authors: Thomas L. E.
Published: June 2020

G and n phases are complex nickel silicides which commonly form in Fe-Ni-Cr based stainless steels and superalloys during neutron irradiation at 400-600°C. Both phases are cubic and are structurally similar to the common carbides M2 3C6 and M6C which form in many of the same alloys during thermal aging. Although G and n have been analyzed previously by energy-dispersive x-ray spectrometry (EDXS), little is known about their carbon contents.

To further determine the compositional relationships between the G/n silicides and the M 23C 6/M6C carbides, an irradiated Ti-modified 316 stainless steel specimen containing 0.05 to 0.5μm particles of G and n was analyzed by means of electron energy loss spectroscopy (ELS) and EDXS in a field emission gun scanning transmission electron microscope (STEM). The alloy, LSI, has the nominal composition of Fe-16.8Cr-13.5Ni-l.9Mo-0.87Si-2.0Mn-.15Ti-.045C and was irradiated to 2 x 1022n/cm2, E >0.1 MeV, at 510°C in the EBR-II breeder test reactor.
A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments
Authors: W. J. Abramson  , Estry H. W. , Allard L. F.
Published: June 2020

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.

Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.
Automatic focus control system for scanning electron microscope (Model S-570)
Authors: Otaka T. , Yamada O. , Saito S. , Watanabe T.
Published: June 2020

We have developed an automatic focus control and astigmatism correction system for electron microscopes. Fig. 1 shows the Model S-570 SEM.

In the scanning electron microscope focusing operation at high magnifications (several thousand times or higher) requires a great deal of skill and experience. The Automatic Focus Control System enables this difficult operation to be done automatically. Fig. 2 shows the principle of the detecting system of focus.

The electron beam is converged on a specimen by an objective lens and the signal emitted from the specimen is detected by a detector as an imaging signal. Waveform of the imaging signal is sharp at optimum focus conditions and consequently its differential signal shows a large peak height. On the other hand, when the focus condition is not optimum, the imaging signal is smooth and the differential signal shows small peak height. The Automatic Focus Control is a system in which focus condition is regulated automatically so that peak height of the differential signal becomes maximum.
Correlation of x-ray and electron crystallography of biological structures
Authors: Caspar Donald L. D.
Published: June 2020

The development of electron crystallography of biological structures recapitulates in many ways the history of x-ray crystallography started by W.L. Bragg in 1913 and, more particularly, protein crystallography begun by Bernal and Crowfoot Hodgkin in 1934. By the early 1950s Perutz and Bragg were mapping the outline of the hemoglobin molecule by tracing the molecular transform through the use of a kind of negative staining for x-ray diffraction. The demonstration by Perutz and his colleagues that the isomorphous replacement method could be used to solve the phase problem in protein crystallography opened the way to determining the atomic structure of proteins starting with myoglobin.

Electron crystallography was begun by Klug and his colleagues in the mid 1960s using optical diffraction to detect periodicities in the image and then applying optical filtering to separate superimposed two-dimensional lattice images and to average the image of the repeating unit. Following the underlying unity in the optics of image formation and diffraction of light, x-rays and electrons, DeRosier and Klug developed the theory and methodology of three-dimensional image reconstruction with the use of Fourier transforms of digitized images.
High-resolution structural analysis of purple membrane
Authors: Henderson R. , Baldwin J.M. , Agard D.A. , Leifer D.
Published: June 2020

Two crystal forms of the purple membrane from Halobacterium halobium are being investigated. One is the native p3 form which occurs naturally, and the other is an orthorhombic p22121 form which is made artificially with detergent.

Both forms diffract to better than 3 Å resolution. They have been studied by electron diffraction at high (3 Å) resolution, and at lower resolution (6.5-7 Å) by electron microscopy. Both crystal forms occur as membrane sheets, containing a single molecular layer of protein molecules with a lipid bilayer filling the space between the protein molecules, the whole having a thickness of about 45-50 Å. The electron microscopic and diffraction analyses have been carried out in three dimensions using specimens tilted at angles of up to 60° to the incident electron beam.

The resulting Fourier maps of the two structures enable a common shape for a single molecule of bacteriorhodopsin to be determined, which is free of the ambiguity of molecular boundary normally found in crystal structure analyses at lower resolution than that required to trace the path of the polypeptide chain.
Electron crystallography of crotoxin complex thin crystals
Authors: Jeng T.W. , Chiu W.
Published: June 2020

Crotoxin complex is a neurotoxin isolated from the venom of the South America rattlesnake, Crotalus durrissus terrificus. It consists of two dissimilar subunits, one very acidic and the other very basic. Both acidic and basic subunits are required to show its neurotoxicity. The toxin attacks novally on both the pre-synaptic and the post-synaptic sites of the neuro-muscular junction.

This protein has been crystallized in thin platelet forms suitable for electron crystallographic studies and an electron diffraction pattern of a glucose embedded crotoxin complex crystal has been recorded to an atomic resolution. The space group of this thin crystal was determined to be P4222 by a combination of electron microscopic techniques. In each unit cell, there are 8 crotoxin complex molecules arranged in a 4 layer configuration along the c axis. Different crystals have been found to have different thicknesses. We have been able to determine whether the diffraction data is obtained from a crystal with a half or a full unit cell by calculating the crystallographic reliability factors from the digitized electron diffraction pattern and by measuring optical density of a low magnification image recorded immediately after each electron diffractign pattern.
Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin
Authors: Tivol William F. , King Murray Vernon , Parsons D. F.
Published: June 2020

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.

Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.

We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.