bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of electron-diffraction intensity profiles using a photodiode-array detection system
Authors: Warren J. B. 
Published: June 2020

Electron diffraction intensity profiles have been used extensively in studies of polycrystalline and amorphous thin films. In previous work, diffraction intensity profiles were quantitized either by mechanically scanning the photographic emulsion with a densitometer or by using deflection coils to scan the diffraction pattern over a stationary detector. Such methods tend to be slow, and the intensities must still be converted from analog to digital form for quantitative analysis. The Instrumentation Division at Brookhaven has designed and constructed a electron diffractometer, based on a silicon photodiode array, that overcomes these disadvantages. The instrument is compact (Fig. 1), can be used with any unmodified electron microscope, and acquires the data in a form immediately accessible by microcomputer.Major components include a RETICON 1024 element photodiode array for the de tector, an Analog Devices MAS-1202 analog digital converter and a Digital Equipment LSI 11/2 microcomputer. The photodiode array cannot detect high energy electrons without damage so an f/1.4 lens is used to focus the phosphor screen image of the diffraction pattern on to the photodiode array.
Simultaneous TEM thin foil preparation and SIMS analysis of multi-layered photovoltaic devices
Authors: Jones Kim M. 
Published: June 2020

Ion etching of multi-layered photovoltaic devices is commonly used in thin foil preparation for transmission electron microscopy studies. A technique by which a particular intermediate layer of interest can be retained for examination has been developed. By combining a secondary ion tthss spectrometer (SIMS), with an ion etching instrument, we have a powerful means of controlling sanple preparation. Figure 1 is a schematic of the type of thin film photovoltaic device for which these techniques were developed. This device is representative of the generic problans that are associated with the polycrystalline low cost photovoltaic approaches. The limitations on ultimate cell performance can be directly related to defects occuring at interfaces and within the crystallites, nultiple phase formation at Junctions, crystallographic integrity of the grains, impurity segregation and accunulation at intergrain regions, and enhanced diffusion down grain boundaries.Isolating a particular layer of 1-10 μm thickness in multi-layered devices is at best time consuming and inefficient using the conventional methods of pre-polishing chanical etching, or ion etching alone.
Slow-scan imaging applications of a digital video framestore system
Authors: Boyes E. D. , Goringe M. J. , Gill J. J. , Muggridge B. J. , Northover J. p. , Salter C. J. 
Published: June 2020

Conversion of slow scan signals with a continuously updated image display or video recording at TV rate is one of the functions available using a digital video framestore system in conjunction with a scanning electron microscope (SEM, STEM, AEM etc.) or other types of electron probe equipment e.g. EPMA, AES etc. Acceptable inputs are standard TV format; digital sampling of a range of analogue slow scans or directly coupled digital scans.Routines for noise reduction by spatially resolved time averaging during acquisition are under software control with direct operator involvement in selecting the appropriate conditions via a soft-key redesignation of the VDU numeric pad functions (Fig.l) and within the possibilities of the hardware; making TV rate more useable e.g. to reduce specimen charging and as an essential prerequisite to more sophisticated signal/image processing. Both running average (RVP, 8-bit) and straight integration (16-bit) modes are possible with the Microconsultants Intellect systems in use in our laboratory.
Production and STEM examination of controlled-size silver clusters
Authors: Listvan M. A. , Andres R. P. 
Published: June 2020

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.
Direct observations of radiation-enhanced transformations in glass
Authors: DeNatale J. F. , Howitt D. G. 
Published: June 2020

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.
The effect of particle height on the analysis of precipitates in alloy foils
Authors: Allen Robert M. 
Published: June 2020

The relative height of small second-phase particles within a thin alloy foil can have a significant effect on the characteristic x-ray signal obtained from the particle during microanalysis in a STEM. Figure 1 illustrates this for the case where the energy dispersive x-ray detector attached to the STEM views the sample on the side entered by the incident electron beam. If the particle is located below the top foil surface, as in Fig. 1a, beam spreading may reduce the total current striking the particle, thereby reducing the generated signal. The x-ray spectrun of the particle may be further reduced and distorted by matrix absorption en route to the detector. Clearly the optimal position for microanalysis is shown in Fig. 1b: The particle to be analyzed should be on the sample surface facing the beam and x-ray detector.These considerations were demonstrated in an experiment performed on a sample of Alloy 800, a high-allqy austenitic steel. The STEM used was a JEQL 200CX operated at 200kV. The second phase particles (Ti-carbides in this case) in the Alloy 800 electropolished at different rates from the matrix during sample preparation. Those particles located at the surface of the foil after thinning therefore produced surface relief and could be imaged using the secondary electron detector on the STEM. Figure 2 shows a mixed secondary electron/transmitted electron image of the TiC particles analyzed for this experiment.
Very-high spatial resolution analysis in STEM
Authors: Garratt-Reed A.J. 
Published: June 2020

When analyzing a composition profile in a thin foil using a Scanning Transmission Electron Microscope, the measured profile is a convolution of the electron probe diameter, the actual profile and the degree of beam spreading in the sample. While it is possible to show that fractions of a monolayer of segregant are detectable in foils 100 nm thick, similar calculations indicate that if a probe 0.8 nm in diameter is incident upon a foil 20 nm thick, then broadening is insignificant. For example, fig. 1 is a computation (using the method of Hall, et.al) of the predicted measured profile resulting from a real gaussian distribution of chromium in iron, 2.5 nm wide, measured in the conditions just mentioned. Such results indicate that distributions of solutes well under 10 nm in separation should be readily distinguishable from each other.In some pearlitic steels, alloy elements are incompletely partitioned during the pearlite reaction, and subsequently diffuse from the ferrite into the cementite, where they form very narrow (∿ 2 nm wide) enriched zones either side of the cementite plate, which is itself around 10 nm thick.
The role of radiation damage to the analysis of composition in electron microscopes
Authors: McElfresh D. K. , Howitt D. G. 
Published: June 2020

The effect of the illuminating electron beam on the local composition of beam sensitive specimens is an important consideration when applying the techniques of analytical electron microscopy (AEM). The decrease in the signal from certain elements is often attributed to their volitalization under beam heating, however, radiation damage to the material by the electron beam is another mechanism which can contribute to compositional changes.The ionization and displacement processes that occur within the region of the specimen irradiated by the electron beam can lead to relatively high concentrations of interstitials. The surrounding material is virtually devoid of these species and so these elements will diffuse down the concentration gradient that is generated and so reduce the X-ray or electron loss signal as the region within the probe is depleted.The radiation damage process will continue as long as the electron beam impinges on the specimen and the presence of high vacancy concentration could induce the displacement of other species as the local binding energies are reduced. In the extreme case one might expect to observe tunnels of condensed vacancies arising from the diffusion process.
Electron energy loss spectroscopy in glancing reflection and other recent EELS developments
Authors: Krivanek O.L. , Tanishiro Y. , Yagi K. , Burgner R.P. 
Published: June 2020

Surface reflection images have recently revealed surface steps, surface- intersecting dislocations, and even the nature of a surface reconstruction process. While a large fraction of electrons incident on a crystal at a low angle penetrate into the bulk where they excite X-rays thus rendering glancing reflection EDXS surface insensitive, the electrons which emerge eventually penetrate typically only 10 to 30Å into the crystal, and should thus be highly sensitive as a surface probe. We have therefore investigated the suitability of glancing reflection EELS as a surface-sensitive chemical analysis technique complementary to glancing reflection imaging.The experiments were performed in a JEM 100B electron microscope modified for ultra-high vacuum (UHV) performance by the addition of liquid He cryo- pumping around the specimen, using a Gatan 607 electron energy loss spectrometer. Fig. 1 shows a series of spectra recorded for various glancing reflection conditions on clean (111) Si. It is clear that most electrons with which REM images are formed have been scattered inelastically at least once.
Application of computer control to STEM
Authors: Clark L. D. , Garratt-Reed A. J. 
Published: June 2020

The current trend in instrumentation of all types is towards computer control. Major increases in system utility are often achieved, and it is frequently also possible to digest and display, in a useful fashion, quantities of data that would be quite unmanageable without the aid of the computer.As the owners of a VG HB5 STEM, for which no commercial computer control package currently is available, our only option was to build a system. This paper describes the reasons we chose to proceed, the type of system we designed, and the results we have obtained so far.The bulk of the work performed on our HB5 consists either of generating composition profiles across grain or phase boundaries, or of particle identification and analysis. In these cases, the work involves much tedium, and the performance of quite simple operations. We decided initially to provide computer-control of the beam position and x-ray analysis, to allow automation of these tasks.
Some applications of a computer-interfaced TEMSCAN
Authors: Nash James W. , Kokubo Yasushi 
Published: June 2020

An electron microscope, interfaced to a computer and image processor becomes a powerful analytic tool. With a simple general interface, applications are defined entirely in software and are thus very flexible.Our system consists of a 100CX TEMSCAN and PDP-11/23 (figure 1). Two selected SEM/STEM signals are converted to digital using Voltage to Frequency convertors (VFC) and counters. The use of VFC's insures capturing an integrated signal over the sample period. Acquired images are stored in a Recognition Concept Inc. "Trapix" image processor. The Trapix consists of memory organized as six 512 x 512 x 8 bit images, and a Pipeline Image Processor with which we can rapidly perform many of transformations useful to disk storage, analysis and presentation of images.The Trapix is able to scroll one image relative to another and combine them in 1/30th second. Hence, stereo pairs can be aligned and combined to display red/green stereo images in real time. The data is stored as 512 x 512 x 4 bits showing some contouring or as 512 x 256 x 7 bits having decreased resolution.
Frozen hydration of protein crystals
Authors: Chiu Wah , Cohen Harold A. , Grant Robert A. , Jeng Tzyy-Wen 
Published: June 2020

The choice of medium for maintaining the protein crystal hydrated on an electron microscopic investigation is made by taking into account its effectiveness in keeping the crystal wet and its scattering density relative to protein molecules. The frozen hydration method first introduced by Taylor and Glaeser seems to be an attractive procedure. They obtained electron diffraction patterns of catalase crystals with reflections beyond 3 Å resolution, and low resolution images with remarkable contrast. This paper deals with our recent experience in applying this technique to the structural studies of the thin crystals of crotoxin complex from rattlesnake venom, T4 DNA helix destabilizing protein, and Fc fragment from IgG of rabbit serum.The most difficult part of the frozen hydration technique is the preparation of a proper amount of ice embedding the protein crystals. We have adopted the method of using double carbon films to sandwich the protein crystals and ice. A visual judgement of the water thickness is made prior to its being frozen in liquid nitrogen
The native structure of the eukaryotic ribosome
Authors: Milligan R.A. , Unwin P.N.T. 
Published: June 2020

A detailed understanding of the mechanism of protein synthesis will ultimately depend on knowledge of the native structure of the ribosome. Towards this end we have investigated the low resolution structure of the eukaryotic ribosome embedded in frozen buffer, making use of a system in which the ribosomes crystallize naturally.The ribosomes in the cells of early chicken embryos form crystalline arrays when the embryos are cooled at 4°C. We have developed methods to isolate the stable unit of these arrays, the ribosome tetramer, and have determined conditions for the growth of two-dimensional crystals in vitro, Analysis of the proteins in the crystals by 2-D gel electrophoresis demonstrates the presence of all ribosomal proteins normally found in polysomes. There are in addition, four proteins which may facilitate crystallization. The crystals are built from two oppositely facing P4 layers and the predominant crystal form, accounting for >80% of the crystals, has the tetragonal space group P4212, X-ray diffraction of crystal pellets demonstrates that crystalline order extends to ~ 60Å.
Three-dimensional structure of a regular bacterial surface layer: The HPI-layer of Deinococcus radiodurans
Authors: Baumeister W. , Hahn M. , Saxton W.O. 
Published: June 2020

Regularly organized surface (RS) layers are a feature common to many bacterial species; they are clearly more abundant than was anticipated even a few years ago. The RS-layers are believed to fulfil a variety of functions in the interaction between the cell and its environment (see e.g. [1]). The so-called HPI-layer of the radiotolerant bacterium Deinococcus radiodurans is a typical example of such a layer: It is composed of a single polypeptide species (Mr 105 kDa) arranged on a hexagonal lattice to form a network that covers the entire surface of the bacterium; it is associated with the outer membrane via hydrophobic protein-protein interactions.Isolated HPI-layer sheets, released from the outer membrane by detergent treatment, have been studied in the electron microscope making extensive use of the present arsenal of preparation techniques: negative staining, (auro- thio)glucose embedding, freeze-dried/unstained, freeze-dried/metal shadowed etc.Because of the notorious problem of lattice imperfections image processing usually followed the strategy of correlation averaging as outlined in some detail elsewhere.
High-voltage electron microscopy of capillary endothelial vesicles
Authors: Wagner Roger C. , Robinson Candy S. 
Published: June 2020

The three dimensional association of endothelial vesicles must be a determinant in their role in transcapillary transport: Vesicles which shuttle materials across the capillary wall would constitute a discontinuous and nonhydraulically-conductive pathway. Transendothelial channels of fused vesicles would be true pores conducting materials in response to hydrostatic and osmotic pressure gradients across the capillary wall. Sessile, fused clusters of vesicles attached to the plasma membrane but not communicating across the endothelial cell would be inconsequential in transcapillary transport. In order to discern the three dimensional association of vesicles, we have employed high voltage electron microscopy to obtain stereopairs of thick sections through blood capillaries.Whole rats were perfuse-fixed with glutaraldehyde-tannic acid (both 1% w/v) via the left ventricle of the heart. The diaphragm muscle was removed and cut into small strips parallel to the muscle fibers. These were osmicated, dehydrated and embedded in Spurr's medium in an orientation such that cross sections of the capillaries could be taken.
Remarks on the application of backscattered electron imaging (BEI) to the scanning electron microscopy (SEM) of biological structures
Authors: de Harven Etienne 
Published: June 2020

Biological ultrastructures have been extensively studied with the scanning electron microscope (SEM) for the past 12 years mainly because this instrument offers accurate and reproducible high resolution images of cell shapes, provided the cells are dried in ways which will spare them the damage which would be caused by air drying. This can be achieved by several techniques among which the critical point drying technique of T. Anderson has been, by far, the most reproducibly successful. Many biologists, however, have been interpreting SEM micrographs in terms of an exclusive secondary electron imaging (SEI) process in which the resolution is primarily limited by the spot size of the primary incident beam. in fact, this is not the case since it appears that high resolution, even on uncoated samples, is probably compromised by the emission of secondary electrons of much more complex origin.When an incident primary electron beam interacts with the surface of most biological samples, a large percentage of the electrons penetrate below the surface of the exposed cells.
An immunogold study of protein synthesis in plant tissue
Authors: Craig Stuart , Goodchild D.J. 
Published: June 2020

Two reserve proteins, legumin and vicilin, account for ∽70% of the total protein in mature pea seed cotyledons, where they are restricted to small membrane bound organelles, the protein bodies. These protein bodies are formed by fragmentation of the cell vacuoles during seed development. The reserve proteins were first detected by immunofluorescence in isolated deposits within such vacuoles.On-grid immunogold labelling of fixed and embedded cotyledons offered the possibility of detecting ultrastructurally the site of synthesis and subsequent stages in the relocation of the protein to the vacuoles. Biochemical data indicate that synthesis takes place on ER-bound polysomes, but has not been able to establish subsequent steps in the transport pathway (5). Immunocytochemical localisation was carried out on glutaraldehyde-osmium fixed tissue embedded in Spurr's resin, sectioned and then treated on-grid with NaIO4. and HCl. This chemical treatment unmasks protein antigenicity, probably by removing protein-bound osmium and aldehyde.
Two types of lipidic particles
Authors: Hui S.W. , Stewart T. P. , Boni L.T. 
Published: June 2020

The molecular arrangements in lipidic particles (LIP) seen on freeze fracture faces of liposomes have been a subject of much discussion. Miller and Hui proposed that these particles were intermembrane attachment sites, while Cullis and de Kruijff favored a model consisting of inverted micelles between bilayer leaflets.In our study of polymorphic phase transitions in mixtures of unsaturated phosphatidylethanolamine (PE) and phosphatidylcholine (PC), We have found evidence of two distinct types of LIP. In most PE/PC mixtures such as soybean PE and egg PC, the LIP have a dimple-like appearance and are definitely conical in cross fracture (fig. 1). Both concave and convex forms are commonly found on the same fracture face (fig. 2). In mixtures of dilinoleoyl-PE and palmitoyl-oleoyl-PC, the LIP are larger and have a round, bead-like appearance. These LIP often align in rows between entrapped water space (fig. 3), or stack in a cubic arrangement (fig. 4). In less ordered areas, conical and spherical LIP can be viewed as complementary lattice.
Nexuses in cultured heart cells: Response to oxygen/substrate deprivation
Authors: Odegarden S. , LeFurgey A. , Sommer J. , Murphy E. , Lieberman M. 
Published: June 2020

Synchronously contracting cultures of embryonic chick heart cells have been developed as a model for evaluating biochemical and structural parameters of functional significance in the intact myocardium during normal or pathophysiological states. Of particular importance in these cells is the morphology of the gap junction or nexus, the structure often associated with cell-to-cell communication (e.g. ionic translocation, electrical coupling). The aims of the present study are [a] to ascertain the presence and describe the morphology of gap junctions in this model system of cardiac cells using freeze fracture electron microscopy and [b] to evaluate changes in the structure of the nexus associated with experimental conditions that alter or disrupt cell metabolism and electrical coupling.For control preparations muscle-enriched monolayer cultures of heart cells from 11-day old chick embryos were grown and maintained in a 5% CO2/95% oxygen atmosphere at 37°C with or without substrate (glucose) as previously described.