bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spot Scan Imaging and the Future of High Resolution
Authors: Downing K.H. 
Published: June 2020

Electron crystallographers who have been working on determination of protein structure have set a goal of obtaining image information to a resolution of about 3.5 Å, from specimens tilted up to 60 degrees. This information would allow the construction of a three-dimensional density map within which the path of the peptide chain could be followed and locations of side chains defined. The recent determination of an atomic model of the membrane protein bacteriorhodopsin (bR) from EM data (1) which was not as complete as we would like, used a good deal of other biochemical and biophysical data to constrain the model. In cases where this type of information is not as extensive as with bR, isotropic high-resolution data would be required. Significant advances in several different areas have brought us tantalizingly close to reaching our goal, but there are still improvements to be made.The essential limitations in obtaining high resolution data from proteins arise from the radiation sensitivity of the specimen, which severely limits the electron exposure that can be used in recording an image and thus limits the signal-to-noise ratio (SNR). Increasing both the electron dose, which is possible with cold specimens, and the area processed, which required implementation of significant computer software, have each given about a factor of three improvement in SNR. Still, with conventional imaging, a study by Henderson and Glaeser (2) revealed that the best images contained only a small fraction of the signal that would be present in a perfect image. Factors such as the envelope of the contrast transfer function and the modulation transfer function of the photographic film account for some loss of contrast, but the factor causing the most loss was found to be beam-induced specimen motion. This motion results from the stress which is produced by changes in bond structure during the course of radiation damage.
An Illuminating System of a 100-kV Analytical Electron Microscope with a Field-Emission Electron Gun
Authors: Delong A. , Chmelík J. , Kolařík V. 
Published: June 2020

Our aim was to design a microscope for application in both the classical transmission electron microscopy (CTEM) and in the analytical electron microscopy having in the scanning modes (SEM, STEM) a resolving power approaching that in the CTEM. The problem can be optimally solved by using the field emission source of electrons. The illuminating system and the objective lens have the following parameters:a) The resolving power of the objective lens in the transmission mode is as high as 3.5 Å.b) The optical aberrations of the pre—field of the objective lens and of the set of condenser lenses allow a resolution of approx. 5 Å to be achieved in the scanning mode.c) The illuminated area of the specimen observed in the transmission mode is large enough to allow operation with the objective lens switched on at a magnification 1000 x.
Libraries of Locations for Different Specimens: An Application of Remote Specimen-Stage Control on the CM Microscope
Authors: Busing Wim M. , Coppoolse Harald P. 
Published: June 2020

A session on the Transmission Electron Microscope normally starts at low magnification with an overview of the specimen to find the region(s) of interest. This region is then centered with the specimen drives and further investigation at higher magnification can start. However, the operator is often in doubt whether the region centered is actually the best, but is also reluctant to move elsewhere for fear of not being able to retrieve the present area. Thus in many cases time and photographic material are wasted on sub-optimal regions of the specimen.The CM-series transmission electron microscopes have a goniometer stage with mechanical read-out of the position of the specimen on the micrometer drives, thereby making it possible to record specimen locations but only by hand. Optionally, the microscope can be equipped with the Specimen Relocation System which provides a digital read-out of specimen position as well as the capability to store specimen locations for later retrieval. A number of potentially interesting locations can thus be stored and, by recalling each location with the Relocation System's motordrives, these locations can be screened quickly at higher magnifications to select the best one for further work.
Development of the H-7100 Tem and its Computer System
Authors: Kobayashi H. , Tomita M. , Ukiana M. , Mizuno H. , Ueki Y. , Yotsuji T. , Konopka J.F. 
Published: June 2020

Built-in TV-systems for TEM image processing and storage are becoming popular in the recent TEM instrumentation. We have completed the development of the H-7100 which has greater expanding capability than the conventional instruments. The H-7100 has been designed around the computer controlled electronics of the H-7000. The new H-7100 electronics is accessible from an external computer including the specimen stage control. When it is coupled with an EDX spectrometer, an automated microanalysis is performed.Fig.l is a system diagram of the specimen stage. The rotation of the DC motor is converted to linear movement by transmission gears and a linear actuator. The linear motion is used to drive the specimen stage. The stage traverse is detected and regulated by numbers of pulse generated by a rotary encoder which is connected to the DC motor. The smallest traverse step of 1nm is available. The pulse signal of the rotary encoder is processed by a computer together with the working magnification to determine the optimum stage traverse. This design allows operator to perform both the low and high magnification work with maximum convenience and comfort. Further, specimen position memory, automatic tracking of the stage traverse and automatic return to a zero position have been incorporated.
The CM-CRYO: A Microscope Dedicated to Cryo-Electron Microscopy in Life Science Applications
Authors: Busing Wim. M. , de Jong Marc J.C. 
Published: June 2020

Low-temperature (cryo) electron microscopy has been established as a promising approach for alleviating technical problems encountered in electron microscopy of life science materials. Cryofixation freezes in the native situation of biological material, with the rapid freezing process preventing redistribution of water-soluble elements in cellular and non-cellular compartments. Thus it becomes possible to correlate tissue morphology with chemical and physical properties.The use of cryo techniques puts stringent demands on the electron microscope technology: an ultra-high vacuum, including special measures to tackle the water vapour released by the specimen; stable, low-drift cryo-temperature specimen holders; special functions providing low-dose imaging conditions; electron dose indicators; and a TV system for observation under low-level illumination. The new CM-CRYO combines these features with the ease of use of the CM microscope concept and the quality of the TWIN objective lens system.
Vibration Isolator System for Electron Microscope
Authors: Ohi K. , Mizuno M. , Kasai T. , Ohkura Y. , Mizuno K. , Murakami K. , Miyazaki T. 
Published: June 2020

In recent years, with electron microscopes coming into wider use, their installation environments do not necessarily give their performance full play. Their environmental conditions include air-conditioners, magnetic fields, and vibrations. We report a jointly developed entirely new vibration isolator which is effective against the vibrations transmitted from the floor.Conventionally, large-sized vibration isolators which need the digging of a pit have been used. These vibration isolators, however, are large present problems of installation and maintenance because of their large-size.Thus, we intended to make a vibration isolator which1) eliminates the need for changing the installation room2) eliminates the need of maintenance and3) are compact in size and easily installable.
Oil-Free Forepumps for Electron Microscopes
Authors: Farrant J.L. , Bez E. 
Published: June 2020

Even the best present day ultrahigh resolution electron microscopes embody a paradox. They are equipped with the most modern ion pumps, cryopumps or turbomolecular pumps, but the forepumps are oil-sealed rotary pumps invented by Gaede in 1905. Consequently efficient protective systems are necessary to prevent oil-derived vapour from contaminating the specimen, the objective lens aperture diaphragm, the field emission or lanthanum boride electron sources and other sensitive areas. Continuously operable, reciprocating, dry fore-vacuum pumps, based on our designs, have been made and sold by Varian for over three years and have proved reliable in a wide range of equipment. Electron microscopes too, should be provided with oil-free forepumps.The need for oil-free forepumps occurred to one of us in 1949 when it was shown that pump oil was the major source of the carbonaceous contamination of microscope specimens and objective lens diaphragms. Materials available at that time seemed unsuitable for the construction of oil-free forepumps but during 1968 we learnt that highly wear resistant, low-friction composites of polytetrafluoroethylene (PTFE) filled with finely divided bronze, graphite, etc. were being marketed. In 1970 we began to devise a practical oil-free pump. Rotary designs were rejected because all practicable shaft seals require oil lubrication to transfer heat from the seal to the shaft to prevent the seal material from reaching temperatures at which it would soften and wear rapidly. Each lubricated shaft seal would expose, at least, a narrow annulus of oil to the vacuum in the working chamber and seal wear would lead to substantial leakage of oil.
The Added Value of Graphical Input and Display for Electron Lens Design
Authors: Lencova B. , Wisselink G. 
Published: June 2020

Recent progress in computer technology enables the calculation of lens fields and focal properties on commonly available computers such as IBM ATs. If we add to this the use of graphics, we greatly increase the applicability of design programs for electron lenses. Most programs for field computation are based on the finite element method (FEM). They are written in Fortran 77, so that they are easily transferred from PCs to larger machines.The design process has recently been made significantly more user friendly by adding input programs written in Turbo Pascal, which allows a flexible implementation of computer graphics. The input programs have not only menu driven input and modification of numerical data, but also graphics editing of the data. The input programs create files which are subsequently read by the Fortran programs. From the main menu of our magnetic lens design program, further options are chosen by using function keys or numbers. Some options (lens initialization and setting, fine mesh, current densities, etc.) open other menus where computation parameters can be set or numerical data can be entered with the help of a simple line editor. The "draw lens" option enables graphical editing of the mesh - see fig. I. The geometry of the electron lens is specified in terms of coordinates and indices of a coarse quadrilateral mesh. In this mesh, the fine mesh with smoothly changing step size is calculated by an automeshing procedure. The options shown in fig. 1 allow modification of the number of coarse mesh lines, change of coordinates of mesh points or lines, and specification of lens parts. Interactive and graphical modification of the fine mesh can be called from the fine mesh menu. Finally, the lens computation can be called. Our FEM program allows up to 8000 mesh points on an AT computer. Another menu allows the display of computed results stored in output files and graphical display of axial flux density, flux density in magnetic parts, and the flux lines in magnetic lenses - see fig. 2. A series of several lens excitations with user specified or default magnetization curves can be calculated and displayed in one session.
Aberrations of Accelerating Tube for High-Voltage Electron Microscope
Authors: Ohye Toshimi , Uchikawa Yoshiki , Morita Chiaki , Shimoyama Hiroshi 
Published: June 2020

The accelerating tube (AT) which accelerates electrons up to a desired energy also functions as an electrostatic lens, In the present paper, numerical calculations were conducted on the electron optical characteristics including the spherical aberration of the AT for the high voltage electron microscope. Several electron optical problems arising from a combination of the AT with a thermionic electron gun (TEG) or a field emission gun (FEG) were studied.<Estimation of aberration for AT lens> The AT consists of 34 electrodes with the inner diameter of 3.3 cm and has the overall length of 142.3 cm (Fig.l). The voltage Va is applied between the cathode and the final electrode of the AT. The initial energy of the electron incident to the AT is eVo, where Vo is the anode voltage of the electron gun mounted on the AT. The electric field inside the AT was calculated using the surface charge method. The ray tracing was carried out on the basis of the relativistic paraxial ray equation, and the cardinal elements of the AT lens were obtained.
High-Brightness Gaseous Field ION Source for Light ION Species
Authors: Siegel Benjamin. M. , Mioduszewski John 
Published: June 2020

We have reported on the very high brightness gaseous field ion source that has been developed at Cornell to produce high angular current density H2+ ion beams with low energy widths. Axially oriented H2+ ion beams from single emission sites with angular currents dl/dΩ= 10-20 μa/sr are obtained routinely. The energy width (FWHM) has been measured to be Δe=1.0 ev. H2+ beams with angular currents as high as 70 μa/sr. have been observed, but these higher current beams have a tail spread on their energy distribution curve.We have now extented this source to produce ion species of He+ with angular current densities, dl/dΩ, in the 10-15 μa/sr range and ions beams of Ne+, A+, N2+ and O+ ions with angular currents dl/dΩ of 3-7 μa/sr.Ion beams with these characteristics have have been achieved by operating the gaseous field ion source under the following conditions:1. In an ultrahigh vacuum system at cryogenic temperatures cooled with LHe and heated to obtain an optimum balance of gas concentration at the emitter tip with physisorption on the tip at temperatures that allow good surface transport from a large area near the apex of the tip to the emission site.
Three-Dimensional Structure of Rotavirus-Fab Complex
Authors: Prasad B.V.V. , Marietta E. , Burns J.W. , Estes M.K. , Chiu W. 
Published: June 2020

Rotaviruses are spherical, double-shelled particles. They have been identified as a major cause of infantile gastroenteritis worldwide. In our earlier studies we determined the three-dimensional structures of double-and single-shelled simian rotavirus embedded in vitreous ice using electron cryomicroscopy and image processing techniques to a resolution of 40Å. A distinctive feature of the rotavirus structure is the presence of 132 large channels spanning across both the shells at all 5- and 6-coordinated positions of a T=13ℓ icosahedral lattice. The outer shell has 60 spikes emanating from its relatively smooth surface. The inner shell, in contrast, exhibits a bristly surface made of 260 morphological units at all local and strict 3-fold axes (Fig.l).The outer shell of rotavirus is made up of two proteins, VP4 and VP7. VP7, a glycoprotein and a neutralization antigen, is the major component. VP4 has been implicated in several important functions such as cell penetration, hemagglutination, neutralization and virulence. From our earlier studies we had proposed that the spikes correspond to VP4 and the rest of the surface is composed of VP7. Our recent structural studies, using the same techniques, with monoclonal antibodies specific to VP4 have established that surface spikes are made up of VP4.
Electron Microscopic Comparison of Frozen-Hydrated with Negatively Stained and Rotary-Shadowed Creatine Kinase Single Molecules
Authors: Winkler H. , Schnyder T. , Lücken U. 
Published: June 2020

The mitochondrial isoform of creatine kinase isolated from chicken cardiac muscle consists predominantly of an octameric protein species with an Mrof 364000 and a small fraction of a dimeric species (Mr=86000). Electron micrographs of negatively stained creatine kinase show the square-shaped octameric molecules (Fig. 3) and the banana-shaped dimers. Mass measurements of individual molecules by scanning transmission electron microscopy yield about 340 kDa for the octamer, and 89 kDa for the dimer. After freeze-drying and high-resolution shadowing the surface of the octameric molecules shows a distinct cross-like division into four units (Fig. 4). The image analysis with circular harmonic averaging reveals a pronounced four-fold symmetry of both the rotary-shadowed and negatively stained octamers.Unstained creatine kinase molecules are investigated with cryo-electron microscopy. The samples were diluted with buffer solution to about 1 mg/ml. Drops of the suspension were applied to glow-discharged holey carbon films, blotted to remove excess liquid, immediately plunged into partially solidified liquid ethane, and stored under liquid nitrogen until insertion into the microscope. The specimens were examined in the DEEKO 250 electron microscope, operated at 100 kV. Micrographs were recorded by minimum-dose methods at a magnification of 60000 and an underfocus of about 1000 nm (Fig. 1).
Imaging with the Tunneling and Force Microscopes
Authors: Quate C. F. 
Published: June 2020

THE SCANNING TUNNELING MICROSCOPEThe STM is an instrument that is used for measuring surface structure. The new instrument was introduced when Rohrer, together with Binnig, discovered that a single atom at the end of a sharp tungsten needle could probe the electronic structure of smooth conducting surfaces. Their atomic probe was placed in close proximity to the surface and mechanically scanned over the image. The resolution is sufficient to define the spatial positions of the atomic sites with extraordinary precision. This instrument is ideal for characterizing small structures.The instrument operates over a wide range of temperatures - from liquid helium at 4K to room temperature and beyond. It works in a variety of atmospheres; vacuum, gases and liquids. Piezoelectric scanners are used to move the probe over the surface with the precision necessary to determine the atomic positions. The most favored scanner consists of a single piezotube with electrodes configured to provide motion in three dimensions.The scanning tip is the STM component, more than any other, that determines the resolving power. The tip is usually formed with electrochemical etching similar to that used in making tips for the field emission microscopes. However, more elaborate systems can be used. Fink has shown that it is feasible to fabricate, in a controlled way, a tip that consists of a single atom. He uses single crystal (111) tungsten and evaporates ions from the tip with a combination of heat and high field. This procedure reduces the apex of the tungsten rod to a single atom.
High-Resolution UHV Electron Microscopy of Reconstructed and Adsorbed Surfaces
Authors: Takayanagi Kunio 
Published: June 2020

High-resolution electron microscopy (HREM) has been applied for structure analyses of reconstructed and adsorbed surfaces at atomic resolution in transmission (TEM) and reflection (REM) mode by using an UHV electron microscope (modified 2000 FXV). In the last ICEM conference, we reported instrumental design of the new UHV electron microscopet[1] with a review on atomic structure study by UHV -EM[2]. In this review we show dynamic structural studies of surfaces which have been revealed by using a TV camera-and-video recording system. Details of each topic shown here are given in original papers[3-8].The UHV electron microscope of 200 keV has the theoretical point-to-point resolution of 0.21 nm. The microscope has two exchange system for evaporators and a gas-inlet system. Surface structural changes recorded on a video tape are resolved at time resolution of 1/30 sec. Figures shown are reproduced from the video frames.High-Resolution REMIn REM mode, we obtain lattice fringes of the surface superlattices by interference of reflections so that the position of the fringes vary with the excitation condition similarly to lattice fringes in TEM. In a certain reflection condition the lattice fringes can be regarded as the structure image. In case of Si(111)7×7 surface, positions of dark lattice fringes (0.23 nm spacing) of the 7×7 coincide almost with the steps[9,10].
Scanning Low-Energy Electron Diffraction Microscopy Combined with Scanning Tunnling Microscopy
Authors: Ichinokawa Takeo 
Published: June 2020

A ultra-high vacuum scanning electron microscope (UHV-SEM) with a field emission gun (FEG) has been operated in an energy range of from 100 eV to 3 keV. A new technique of scanning low energy electron diffraction (LEED) microscopy has been added to the other techniques: scanning Auger microscopy (SAM), secondary electron microscopy, electron energy loss microscopy and the others available for the UHV-SEM. In addition to scanning LEED microscopy, a scanning tunneling microscope (STM) has been installed in the UHV-SEM-.The combination of STM with SEM covers a wide magnification range from 105 to 107 and is very effective for observation of surface structures with a high resolution of about 1 Å.A UHV-FEG-SEM is equipped in a chamber in which the vacuum is better than 2×10-10 Torr. A movable cylindrical mirror analyzer (CMA), a two dimensional detector of diffracted LEED beams, an ion gun and a deposition source are installed in this chamber. The concept of the scanning LEED microscope is comprised of two steps: (1) the formation of a selected area LEED pattern and (2) the generation of raster images with information contained in the diffraction pattern. In the present experiment, the LEED detector assembly shown in Fig.l has been used; it consists of two hemisherical grids, a two-stage channel-plate amplifier and a position-sensitive detector. The selection of one (or more) diffracted beam is performed electronically by a window using the two-dimensional analogue comparators. The intensity of a particular beam selected by the window modulates the brightness of the scanning image and a dark field image sensitive to the surface structure is formed. The experimental spatial resolutions of 150 Å and 500 Å have been attained at the primary electron energy 1 keV and 250 eV, respectively.
High-Speed Reflection Electron Microscopy of Laser-Induced Surface Transitions
Authors: Heinricht F. 
Published: June 2020

Micropatterning of bulk material by pulsed laser radiation is a promising technique for many applications, e.g. drilling and data storage. Due to the fact that laser radiation can be applied very localized, high power densities in a small volume of the treated specimen can be realized. As a result of rapid heat-up and cool-down processes, unusual phases and microstructures can be generated.Time-resolving methods, especially imaging with short exposures times are quite useful in order to understand the physics standing behind. As a diagnostic tool electrons are superior to other probes, e.g. light optics, due to their sensitivity to topography, material composition and structure. Unfortunately , the SEM - one of the most common microscopes for surface analysis - cannot be used for investigations in the the nanoseconds time domain due to its far to slow scan time. On the other hand, the reflection electron microscope (REM) is one of the very few instruments, which is capable to image all points of the treated surface simultanously.In order to achieve electron optical images of laser pulse induced processes on surfaces with exposures times of a few nanoseconds, a high-speed REM was developed. This new instrument is based on a conventional TEM, additionally equipped with the following units:- a laser pulsed thermal electron gun, which delivers high-brightness electron pulses with duration of 20ns.