bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Contrast from Lattice Defects
Authors: Bell W. L. 
Published: June 2020

The differential equations of the two-beam dynamical theory of electron diffraction in an absorbing single crystal are, ignoring unimportant phase factors:where T(z) and S(z) are the transmitted and diffracted amplitudes, the mean and anomalous absorption distances; to is the extinction distance, z the foil thickness, Sg the macroscopic deviation parameter, ḡ the reciprocal lattice vector and R the displacement function of any defect present in the crystal. Occasionally, but not often, these equations can be handled by standard techniques; the wave vectors allowed in the crystal can be determined and the transmitted and diffracted waves expressed as linear combinations of waves with these wave vectors.
Dislocation Configurations in the γ’ Phase Ni3(AlTi)
Authors: Thornton P. H. , Davies R. G. 
Published: June 2020

The γ’ phase Ni3Al, as with all f.c.c. metals and also the isomorphous phase CU3Au, deforms by octahedral slip over a wide temperature range. However, in contrast to these other materials cube slip can also occur in γ'. This extra slip mode, which is very unusual in metals, has been observed to operate at temperatures near 800°C. In the present study of the deformation behavior of the γ' phase Ni3(AlTi), the critical resolved shear stress for cube slip was found to become equal to that of octahedral slip at 400°C approximately and was less than that of octahedral slip at 700°C.An examination of slip plane sections of <100> oriented crystals of Ni3(AlTi), in which deformation is restricted to the ﹛111﹜ mode, revealed mainly screw dislocations in samples deformed at temperatures between 25°C and 750°C. At the lower temperatures, the screw dislocations were straight (Fig. 1) whereas at the higher temperatures the dislocations were more heavily jogged (Fig. 2). In contrast, slip plane sections taken from crystals which could deform by cube slip showed both edge and screw dislocations (Fig. 3).
Stacking Fault Contrast in an Ordered L12 Lattice
Authors: Oblak J. M. , Kear B. H. 
Published: June 2020

Stacking fault contrast arises from the phase shift α = 2π ḡ · experienced by the diffracted wave at the fault. In an ordered L12 lattice, the displacement <111> is not necessarily equivalent to a displacement of the type <112>. 1 and 2 differ by a displacement <110> which can introduce a phase shift of π when ḡ is a superlattice diffraction vector. The physical difference can be seen by examining the formation of an intrinsic fault. When the fault is produced by removal of a close packed plane, <111>, no nearest neighbor violations of order result; on the other hand,nearest neighbor order is disrupted by shear of the <112> type.Similarly, there are two types of extrinsic faults. Values of α are listed in Table I for [111] and [112] with ḡ of the form 100, 200, and 300. As expected, the two representations are equivalent when ḡ is a fundamental reflection. For g = 100, 010 the values of α for 1 and 2 differ by π because of the antiphase boundary associated with the latter displacement.
Dislocations and Growth Occlusions in Tungsten Selenide
Authors: Richman M. H. , Prince K. D. , Wold A. 
Published: June 2020

Tungsten selenide, WSe2, crystallizes in the molybdenite structure and has the space group . The cations are arranged in close-packed hexagonal layers surrounded by two adjacent close-packed planes of anions - in such a way that the metal ions occupy trigonal prismatic sites. The basic unit cell consists of three of these AX2 units and exhibits basal plane cleavage. WSe2 is a semiconductor and is transparent to light; transmitting it in the long-wavelength red region of the spectrum. The existence of these properties makes it interesting to study, at the electron microscope level, the structural effects which could influence the electrical and optical properties of this material.Samples of WSe2 single crystals were grown by vapor transport with iodine using the technique of Kershaw, Vlasse, and Wold. By using repeated cellophane tape strippings, thin flakes were obtained with a basal plane orientation. These were then floated from the tape in benzene, rinsed in acetone, and mounted on grids.
A Simplified Electron Beam Gun for Producing Evaporated Films in Electron Microscopy
Authors: Schneidniller R. F. , Richardson J. H. 
Published: June 2020

The use of an electron beam as the source of heat for the vacuum evaporation of materials has increased rapidly in the past few years. Some of the advantages of electron beam over resistance heating are; 1) it can be easily controlled and manipulated. However, even with these significant advantages it has not found extensive application in most electron microscopy laboratories. The main reason for its limited use is that the commercial instruments available are for heavy production work; as a result they are overdesigned for this purpose. The object of this study was to design an electron beam instrument specifically for this field. This would require the instrument to be: 1) easily constructed using readily available commercial parts, 2) nominal in cost and 3) uncomplicated to operate.The initial phase of this study was concerned with the electron gun design. A television picture tube gun was chosen because it produces a fine beam of electrons, it has incorporated into its design all of the elements necessary for critical control of the electron beam and it is readily available.
A Newly Designed 650kv Electron Microscope
Authors: Shiraishi K. , Katsuta T. , Ozasa S. , Todokoro H. 
Published: June 2020

We have recently completed a newly designed 650KV electron microscope. An external view of this advanced instrument is shown in Figure 1. A symmetrical Cockcroft-Walton circuit has been adopted as the high voltage generator. The cathode is heated by high frequency power; a battery is not employed. The high voltage stability is better than 1 x 10-5/min.The sectional diagram of the column shown in Figure 2 is 420mm in diameter and 2750mm in height. The illuminating system consists of a double condenser lens and a magnetic alignment device. Dual deflector assemblies for dark and bright field images, selectable by push button, are built beneath the condenser lens. Two selectable stigmator power supplies are also provided for dark and bright field image operation.
Objective Lens Properties of Very High Excitation
Authors: Suzuki S. , Akashi K. , Tochigi H. 
Published: June 2020

Recently the image quality of the electron microscope has been highly improved, because of technical advances made for the exclusion of mechanical and electrical instabilities in the instrument itself. To further improve the resolution, it is important to minimize the chromatic aberration, as well as the spherical aberration. This is true, even though the accelerating voltage has excellent stability; because of the unavoidable velocity fluctuations of electrons, resulting from thermal emission from the cathode, and the energy-loss in the specimen.Therefore, the specimen should be immersed deeply into the lens field, to make these aberrations small. The result will be very high lens excitation. In 1962, Professor E. Ruska and Dr. W. Riecke had investigated the single field condenser-objective lens at the center of which the specimen is placed. Prior to that, in 1960, Dr. S. Suzuki, one of the authors, had pointed out that this new objective lens, in which the specimen is placed at the image side from the center of the lens field,(of the condenser-objective lens: but no special illuminating system is necessary.
High Voltage Electron Microscopy
Authors: Fisher R. M. 
Published: June 2020

The striking results obtained by Dupouy and Perrier using the Toulouse microscope sparked extensive interest in high voltage microscopy throughout the world. Several similar instruments are now in use and others will be operational in the near future.The Physical basis for high voltage microscopy is a marked reduction in electron wavelength and scattering cross section with increasing voltage (Fig. 1) which promise improved resolution and penetration. Because of the relativistic increase in electron mass, the refractive power of the lenses in the electron optical column would have to be increased 20x to maintain the dimensions of 100 kv microscopes. The maximum peak field (Hm) magnetic lenses is limited by saturation of the iron pole-pieces resulting an increase in minimum focal length (Fig. 2) and hence of column dimensions. The suitability of superconducting lenses for high voltage microscopy has not escaped attention and no doubt they will be utilized in the near future.
The Potentials of Scanning Microscopy
Authors: Crewe A. V. 
Published: June 2020

If the resolving power of a scanning electron microscope can be improved until it is comparable to that of a conventional microscope, it would serve as a valuable additional tool in many investigations.The salient feature of scanning microscopes is that the image-forming process takes place before the electrons strike the specimen. This means that several different detection systems can be employed in order to present information about the specimen. In our own particular work we have concentrated on the use of energy loss information in the beam which is transmitted through the specimen, but there are also numerous other possibilities (such as secondary emission, generation of X-rays, and cathode luminescence).Another difference between the pictures one would obtain from the scanning microscope and those obtained from a conventional microscope is that the diffraction phenomena are totally different. The only diffraction phenomena which would be seen in the scanning microscope are those which exist in the beam itself, and not those produced by the specimen.
Thermal Stress Effects of Thin Superconducting Films
Authors: Connella M. , Deck R. J. , Morriss R. H. 
Published: June 2020

In order to completely understand the role of microstructural defects in superconductivity, it is very desirable to have quantitative correlations between superconducting properties and structural properties. This research is part of a study to correlate grain-sizes with “flux creep phenomena” which occur in the mixed state of Type II superconducting films. Since the superconducting properties in our study must be observed at liquid helium temperatures, whereas the films are evaporated at elevated temperatures, the structural changes produced in some films by cycling to 4.2°K have been investigated.As the temperature of a film is lowered, the difference in thermal expansion coefficients of a film and its substrate results in thermal stress. This stress can produce structural changes. Films have been examined by electron microscopy techniques before and after a temperature cycle down to 4.2°K and back to room temperature. All temperature cycles were carried out in approximately 20 minutes. Both transmission and replication techniques have been employed. The direct replication method was employed using carbon. The carbon replica was separated from the film and post-shadowed with Pt-C.
Structure of Amorphous Films Using Direct Recording Electron Diffraction
Authors: Dove D. B. 
Published: June 2020

Vapor deposited layers of certain materials show a diffuse, amorphous diffraction pattern; carbon is an example. Such patterns may not be interpreted by identification of Bragg peaks, instead the intensity profile is measured with all possible precision and the data is then treated by computer, yielding what is, in effect, a spectrum of interatomic distances within the specimen.The direct recording electron diffraction technique is particularly suited to the measurement of diffuse patterns. The electron beam from a conventional electron gun and magnetic lens arrangement produces a transmission diffraction pattern of a thin film specimen. Coils beneath the specimen produce a magnetic field which deflects the diffraction pattern across a very small aperture.
Systematic-Reflection Effects in Electron Diffraction
Authors: Fukuhara A. 
Published: June 2020

Many workers have recently noticed what is called many-beam effects In the electron diffraction by crystals. In particular it was found and studied by several people that some second-order reflections vanish even at the exact Bragg position when the acceleration energy coincides with a particular characteristic value EC. This phenomenon has been confirmed to be due to the effect of the first order reflection which is not exactly excited at this position. Systematic reflections sometimes have a decisive role as in this example depending upon the crystal and the reflection. Furthermore it must be noted that the effect is intensified with the rise of the acceleration energy owing to the relativistic change in the electron diffraction.In this study the effects of systematic reflections on extinction contours obserable in an electron-microscopic image of a crystal have been investigated on the basis of dynamical theory taking more than two beams into account. Suppose a wedge-shaped crystal which bends uniformly. As is well known extinction fringes are observed in a bright-field image of such a crystal. This intensity distribution due to diffraction contrast has been computed and printed as in half-tone process by a line-printer of an electronic computor Hitac 5020. Four groups of systematic reflections are studied in the present report: Al(nnn) at 100kv, Al(nnn) at 1000kv, Si(nnn) at 100kv and hexagonal CdS(noo) at 150kv.
Charge transfer in binary alloys: A future for electron energy loss spectroscopy in materials science
Authors: Ahn C. C. , Pearson D. H. , Fultz B. T. 
Published: June 2020

The redistribution of atomic charge which takes place from an atom of one type to that of another in a binary alloy system is fundamental to the formulation of models of enthalpies of formation of these systems. Of special interest are charge transfers where one of the alloy constituents is from the first row transition series. The extent to which the 3d band is filled, ultimately plays an important role in the propensity with which alloys will form intermetallic phases. An understanding of electron charge transfer is important not only in crystalline systems but can also serve as the basis for the determination of the extent of chemical short range order (CSRO) in amorphous binary alloys.Electron energy loss spectroscopy (EELS) in the electron microscope can probe unoccupied bound states and unlike other spectroscopies which probe core levels, is not surface sensitive. The features of the energy loss spectra of the 3d metals which make charge transfer studies possible are the L23 transitions. These spectra are characterized by two “white lines” at the threshold energy which result from ionizations from the 2p3/2 and 2p1/2 spin orbit subshells to a narrow bound 3d state. Beneath and beyond the white line transitions are transitions to the continuum states.
Electron microscopy and the deep sea: Discovery and exploration of symbioses between invertebrates and bacteria
Authors: Cavanaugh Colleen M. 
Published: June 2020

Electron microscopy has played an important role in the discovery of symbioses between sulfur-oxidizing chemoautotrophic bacteria and marine invertebrates. Initially proposed for deep-sea hydrothermal vent tubeworms, associations between chemoautotrophs and invertebrate hosts appear to be widespread in nature (see review). In these proposed mutualistic symbioses, bacterial endosymbionts are thought to provide the host animal with an internal source of nutrition via the autotrophic fixation of CO2, analogous to the role of chloroplasts in plants. Reduced inorganic compounds, e.g., sulfide, serve as the symbionts' source of energy and reducing power. The host, in turn, provides its symbionts with the necessary inorganic nutrients for chemosynthesis.Transmission and scanning electron microscopy have indicated that numerous procaryotic-like cells, resembling Gram-negative bacteria in ultrastructure, comprise the bulk of the trophosome tissue in Riftia pachyptila, the vent vestimentiferan tubeworm. Further transmission electron microscopy (TEM) studies show that the symbionts are contained within membrane-bound vacuoles and appear intracellular. Activities of enzymes associated with sulfur metabolism and with carbon fixation, notably ribulose-1,5-bisphosphate carboxylase (RuBPCase), the key enzyme of the Calvin Benson cycle, have been detected in the trophosome tissue, indicating that the symbionts are chemoautotrophs.
3-D organization of fibrinogen receptors using computer reconstruction and whole-mount microscopy
Authors: O'Toole E. T. , Hantgan R. R. , Lewis J. C. 
Published: June 2020

Thrombocytes (TC), the avian equivalent of blood platelets, support hemostasis by aggregating at sites of injury. Studies in our lab suggested that fibrinogen (fib) is a requisite cofactor for TC aggregation but operates by an undefined mechanism. To study the interaction of fib with TC and to identify fib receptors on cells, fib was purified from pigeon plasma, conjugated to colloidal gold and used both to facilitate aggregation and as a receptor probe. Described is the application of computer assisted reconstruction and stereo whole mount microscopy to visualize the 3-D organization of fib receptors at sites of cell contact in TC aggregates and on adherent cells.Pigeon TC were obtained from citrated whole blood by differential centrifugation, washed with Ca++ free Hank's balanced salts containing 0.3% EDTA (pH 6.5) and resuspended in Ca++ free Hank's. Pigeon fib was isolated by precipitation with PEG-1000 and the purity assessed by SDS-PAGE. Fib was conjugated to 25nm colloidal gold by vortexing and the conjugates used as the ligand to identify fib receptors.
Fluorescent microtubules break up under illumination
Authors: Vigers G.P.A. , Coué M. , McIntosh J.R. 
Published: June 2020

The dynamic behavior of microtubules (MTs) in living cells has recently been elucidated by the use of tubulin tagged with a fluorescent molecule and then injected into cultured cells. The dynamics of the labelled tubulin are then followed either by watching the incorporation of the fluorescence immediately after injection, or by monitoring fluorescence redistribution after photobleaching (FRAP).Until recently, the best fluorescent analogue of tubulin appeared to be dichlorotriazinyl-amino-fluorescein tubulin (DTAF-tubulin). We have now made fluorescein, rhodamine and X-rhodamine n-hydroxy-succinimidyl derivatives of tubulin. These analogues all have a higher fluorescence to protein (f-to-p) ratio and better in-vitro assembly characteristics than the DTAF-tubulin previously used. They have been injected into cultured PtKl cells, where they incorporate well into the microtubule cytoskeltons of the cells. However, while characterising the properties of these four analogues we discovered that they all suffer from a major problem: Microtubules formed from them, either in vitro or in vivo, are destroyed as the bound fluorophore becomes photobleached. We have characterised the photolability of the fluorescent microtubules both in vivo, using epifluorescence microscopy, and in vitro with DIC microscopy.
Preparatory techniques for the quantitative analysis of asbestos in tissues
Authors: Roggli V. L. 
Published: June 2020

With the heightened awareness of various diseases related to asbestos exposure in the workplace, there is an increasing demand for the analysis of tissue for its asbestos fiber content. Quantitative analysis of tissue asbestos burden is not only a valuable research technique, but also has medical implications regarding etiology in patients with suspected asbestos-related diseases and legal implications regarding product liability. It is the purpose of this article to briefly review the various techniques used in the preparation of tissues for quantitative analysis of asbestos fiber content. These can be conveniently divided into four steps: 1) tissue selection; 2) digestion; 3) filtration; and 4) mounting.Tissue selection. The first requirement for tissue asbestos analysis is that an adequate sample is available. Since there is some variation in tissue asbestos content from one site in the lung to another, the more tissue that is available to sample the better.
Confocal microscopy at the integrated microscopy resource for biomedical research (IMR) of the university of wisconsin
Authors: Schatten G. , Paddock S. , Cooke P. , Pawley J. 
Published: June 2020

Confocal microscopy holds great promise for improved imaging of fluorescent or reflective biomedical specimens. The IMR is actively investigating the advantages and optimal usage of the Medical Research Council's Lasersharp laser - scanning confocal microscope and Tracor/Northern's Tandem Scanning Microscope, which benefits from the principles outlined by Petran et al. and Boyde.Quantitative evaluation of microscopic images has always been complicated by the effect of out-of-focus structures on the final image. These effects can be greatly reduced if the conventional light microscope is replaced by a scanning-confocal light microscope. In such an instrument two conditions are met: 1) only a single point of the sample is illuminated at any time and 2) this point on the sample is then imaged onto the pinhole at the entrance to the photodetector. Because little light from out-of-focus planes will pass through the pinhole, only in-focus data is recorded.
Cryotransfer device for cryo-SEM to observe unfixed frozen biological samples
Authors: Makita T. , Asahina T. , Manba K. , Kagabu S. 
Published: June 2020

Further to our previous reports on the combination of CRYO-SEM and WET-SEM, this is application of another type of cryo-SEM device(SP2000 Sputter cryo, ST2000 Semtran, and SC2000 Semcool of Emscope Lab,England) attached to WET- SEM(W-40,Akashi Beam Technol.Tokyo) and SEM(DS130,ABT.Tokyo) to observe unfixed tissues of rats. The main check points of this system were how its cryotransfer device could prevent frost and ample space of cryo chamber which is independent to SEM chamber could safely utilized.Briefly preparation steps before observation were as follows;To insert thin specimen into two metalic tubies and install this assembly in specimen holderFor rapid freezing immerse this whole assembly into semi-solid nitrogen.Enclose this frozen specimen within a small chamber of transfer device and evacuate the chamber.Transfer to precooled (less than-170°C) specimen preparation chamber.By a stroke of handle,crack two metalic tubes in which frozen samples are contained. Alternatively scrach the surface of samples by a surgical knife.
Low-temperature specimen preparation apparatus and techniques for low-temperature scanning electron microscopy (LTSEM) and synchrotron soft x-ray microscopy
Authors: Bastacky Jacob , Hayes Thomas L. , Lee Joong , Lee Charles , Goerke John , Ferreira Steve , Thrasher Ralph , Garcia Edwin 
Published: June 2020

We have developed equipment and techniques for low-temperature scanning electron microscope (LTSEM) and x-ray microscope examinations of animal tissue samples. A cryoprobe for rapidly freezing tissue in vivo, a low-temperature saw for cutting large blocks of frozen tissue without warming, cardboard containers for sample storage in liquid nitrogen (LN2), tools for holding and manipulating frozen specimens, and an under-LN2 specimen viewer are described here. An LTSEM specimen holder for small blocks of tissue and a low-temperature trim saw for precisely cutting such blocks are described elsewhere. We have found such equipment, along with various commercial and specially fabricated dewars, to greatly facilitate our LTSEM experiments.To minimize ice crystal size by freezing as rapidly as possible and to maintain tissue in as close to normal physiologic state as possible during freezing, we use a cryoprobe for freezing 1 cm2 surfaces of tissue in vivo. The cryoprobe (Fig. 1) is a highly-polished 1 mm thick, 10 mm diam.