bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Resolution Cryo-Electron Microscopy of Biological Macromolecules
Authors: Fujiyoshi Yoshinori 
Published: June 2020

The resolution of direct images of biological macromolecules is normally restricted to far less than 0.3 nm. This is not due instrumental resolution, but irradiation damage. The damage to biological macromolecules may expect to be reduced when they are cooled to a very low temperature. We started to develop a new cryo-stage for a high resolution electron microscopy in 1983, and successfully constructed a superfluid helium stage for a 400 kV microscope by 1986, whereby chlorinated copper-phthalocyanine could be photographed to a resolution of 0.26 nm at a stage temperature of 1.5 K. We are continuing to develop the cryo-microscope and have developed a cryo-microscope equipped with a superfluid helium stage and new cryo-transfer device.The New cryo-microscope achieves not only improved resolution but also increased operational ease. The construction of the new super-fluid helium stage is shown in Fig. 1, where the cross sectional structure is shown parallel to an electron beam path. The capacities of LN2 tank, LHe tank and the pot are 1400 ml, 1200 ml and 3 ml, respectively. Their surfaces are placed with gold to minimize thermal radiation. Consumption rates of liquid nitrogen and liquid helium are 170 ml/hour and 140 ml/hour, respectively. The working time of this stage is more than 7 hours starting from full LN2 and LHe tanks. Instrumental resolution of our cryo-stage cooled to 4.2 K was confirmed to be 0.20 nm by an optical diffraction pattern from the image of a chlorinated copper-phthalocyanine crystal. The image and the optical diffraction pattern are shown in Fig. 2 a, b, respectively.
High Resolution Electron Microscopy in Organic Chemistry: 1-MEV Electron Microscope in Kyoto
Authors: Moriguchi Sakumi , Kurata Hiroki , Isoda Seiji , Kobayashi Takashi 
Published: June 2020

Since the epock-making results of 1.5 Å point-to-point resolution obtained with the 500 kV HREM in Kyoto in 1978, we are convinced of the validty of the high voltage electron microscope for the high resolution. However, in order to attain the higher resolution of about 1.3 Å, which is required to resolve a carbon-carbon distance in an aromatic hydrocarbon, there remain so many problems to be solved. In 1990 a new 1 MeV microscope with twin-tank (JE0L-ARM1000) in top-entry type has been installed in Kyoto university aiming to achieve such high resolution.The stability of high voltage is especially important for high resolution because the energy spread of the incident electron beam attenuates the phase transfer function and reduces the image contrast in higher spatial frequencies region. In order to suppress the high voltage fluctuation lower than 1 p. p. m. at 1 MeV and to monitor it, the twin-tank system is adopted, which has produced also satisfactory results in the previous high voltage electron microscopes in Kyoto. Fig. 1 shows the stability of the high tension measured at the top of the accerelating column of the new 1 MeV microscope. The fluctuation is evidently suppressed to less than 1 × 10-6 for five minutes long. The ripple monitored on a sincroscope is also less than 1 p.p.m. The chromatic abberation constant Cc is 3.6mm.
Computer-Assisted High-Re Solution TEM
Authors: Ponce F.A. , Hikashi H. 
Published: June 2020

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.
Profile Imaging of Surfaces
Authors: Smith David J. , Lu Ping , McCartney M. R. 
Published: June 2020

Profile imaging is a method whereby the atomic resolution capabilities of the modern electron microscope can be harnessed to provide direct information about the topography of particular types of surfaces. However, several prerequisites must be satisfied before the surface features visible in the profile image can be considered as genuinely representative of the specific material. The microscope must be properly adjusted (i.e. focus, alignment and astigmatism), the surface in profile must be thin (typically 100Å or less), and it should be free of contaminants or surface reaction products. In the absence of contamination or other amorphous specimen regions, however, correct operating conditions are difficult to establish. Moreover, it is not obvious that any surface reactions or reconstructions that occur along the thin profile edge of the sample are related to bulk surface morphology. Finally, facilities forin situsurface treatment must be considered as essential for materials with reactive surfaces. In this paper, recent progress in surface profile imaging is briefly reviewed, keeping in mind these diverse requirements. The possibility for dynamic image viewing and recording without loss of performance levels should also be appreciated.OxidesClean fracture surfaces of many maximally valent oxides can be obtained by the simple expedient of crushing under a clean solvent with a mortar and pestle, and the ubiquitous holey carbon support film solves the problem of a means for microscope adjustment. Alternative techniques of specimen preparation such as ion-milling or chemical thinning may be required in order to obtain extended areas of a specific surface and orientation, but care is then required to avoid surface, or near-surface, modifications. Typical projected cation spacings in the major low-index zones are such that it is possible to resolve individual cation columns, and profile images such as the [001] SnO2 crystal shown in Fig. 1 clearly reveal the atomic (re-)arrangements at the surface. Several electron-beam-induced processes during extended observations of oxide surfaces have been documented. These include surface diffusion, as well as surface, and near-surface, reduction due to electron-stimulated desorption (ESD) of oxygen. In some maximally-valent transition metal oxides, the epitaxial development of a lower (metallic) oxide takes place, but a variety of end-products can in general be anticipated depending on such factors as the initial surface cleanliness, the residual microscope vacuum and the degree of covalency/ionicity of the original oxide.
UHV-Sem Observation of Si(111) Surface Partially Covered with Surface Structure Induced by Au or Ag
Authors: Endo Akira , Daimon Hiroshi , Ino Shozo 
Published: June 2020

It is well known from LEED (low energy electron diffraction) and RHEED (reflection high energy electron diffraction) studies that when Au or Ag is deposited onto a clean Si (111) surface, many surface superstructures, for example 5×2-Au, √3 × √3-Ag etc. are formed depending upon the substrate temperatures and the coverages of the metals. Applying REM (reflection electron Microscopy) method. Osakabe et al. observed domains of these surface structures in real space, but detailed domain structures are not clear because the method cannot obtain high resolution due to the foreshortening effect. We have developed a SEM (scanning electron microscope) apparatus which have very high resolution and can be operated in UHV (ultra high vacuum). Using this UHV-SEM detecting the secondary electron, the clear domain structures of the two dimensional surface superstructures have been observed for the first time.This UHV-SEM can obtain 2.2×l0-8 Pa by baking all parts related to the vacuum. The lattice image of Au(11O) has been clearly observed with STEM (scanning transmission electron microscope) mode, thus the resolution of 0.143 nm has been obtained. In the secondary electron imaging mode, the resolution of 0.5-0.7 nm has been obtained for the Au particles evaporated on a thin carbon film. This UHV-SEM apparatus has a sample preparation chamber equipped with a RHEED system and Au or Ag evaporation source, in which samples are cleaned, formed into the aimed structures and transferred into the UHV-SEM apparatus.
The Surface of α-Al2O3(0001) Studied with the REM Method
Authors: Kim Yootaek , Hsu Tung 
Published: June 2020

Reflection electron microscopy (REM) and reflection high energy electron diffraction (RHEED) techniques[1] are applied to the study of single crystal α-Al203 surfaces [2,3,4,5] .Specimens were prepared by polishing and 1400°C annealing in air and microscopy was done on a JEOL JEM-200CX and a Philips 400T microscopes operated at 100KV. Most of the REM images were recorded in the mutually perpendicular azimuths.We found that the surface smoothness over a 1 mm2 specimen is not uniform. In some areas the surface steps follow the directions (Fig. 1a. The scale in this figure also applies to all other figures.) while in other areas the steps are continuously curved (Fig. lb). The steps have a rather wide range of heights, probably from one atomic layer to several nm. There is no definite evidence on the smallest steps being one atom high, we have observed steps terminating at a dislocation (Fig. 2) and the weak contrast indicates that the step is only one or two atoms high. But we cannot determine the projection of the Burger's vector in the surface normal [6]. Consequently, we cannot determine the exact height of the step.
Low-Profile Microchannel-Plate Electron Detector System for SEM
Authors: Postek Michael T. , Keery William J. , Frederick Nolan V. 
Published: June 2020

One main impetus of present-day scanning electron microscopy is in the low accelerating voltage mode. This mode of operation is useful for nondestructive inspection especially in the on-line inspection and metrology of semiconductor samples. Today, the majority of the scanning electron microscopes used in nondestructive inspection utilize the standard Ever-hart/Thornley (E/T) detector or a modification of this detector as the main detection system. The E/T detector although extremely efficient, suffers from poor signal to noise ratio at low accelerating voltages. This type of detector also suffers from alignment difficulties especially where linewidth measurement for semiconductor applications is concerned because of the uneven distribution of the collection field which is possible, especially if the detector is not located in a plane of symmetry of the specimen and electron beam. These limitations and others have recently led investigators to reconsider the design of secondary electron detection systems especially for low accelerating voltage and metrological applications.A unique situation developed at the National Institute of Standards and Technology (NIST) where a high efficiency electron detector with an exceptionally low profile was needed for the highly customized scanning electron microscope based metrology instrument under development. This instrument incorporates a large laser interferometer stage in the sample chamber which is used for traceability to the national length standard. The large interferometer stage and the restrictive size and shape of the specimen chamber required the development of a lower-profile electron detector than the standard E/T detector and one which does not interfere with the stage motions and interferometry. It was decided that, since the microchan-nel-plate-type electron detector fulfilled the fundamental requirements imposed by the space restrictions, and since this type of detector is also highly efficient at low accelerating voltages, this type of detector system would be used.
On the Correction Possibilities of the Topo and Compo Signals in SEM
Authors: Mulak Andrzej , Kaczmarek Danuta 
Published: June 2020

The present paper deals solely BSE signals. Murata has determined approximately the angular BSE charakteristic by assuming scattering law of Rutherford, the Everhart’s model and the Thomson - Whidding-ton losses law. Then we haveFor the sake of simplicity we assume a specimen the single - dimensioned topography of which changes solely in the scanning direction. Angular characteristic BSE in the system of primary beam is obtained from (l) by substitutingθ=θ' +αWhile scanning the specimen and taking into account of the Lambert law the current of detector of solid angle dΩ placed at angles θ and φ, takes the form
A Biological Cryosystem for the Scanning Electron Microscope
Authors: zhaohua Zhang , Dong Luo , Yisong Guo 
Published: June 2020

Since early 1970's the use of cold stage on SEM for observation of hydrated samples in their natural state has become more and more popular despite its high cost. Experiences gained from earlier experiments indicate that a successful design should incorporate thefollowing features:1. The specimen temperature should be below −135°C (the recrystallization point of water), lower the temperature, better the results.2. The frozen specimen, the cold block in the specimen preparation chamber, as well as the cold stage should be kept under vacuum at all times to keep them frost free.3. Different specimen preparation processes such as fracturing, coating and sublimation should be possible in one compact preparation chamber .
Accuracy of Stereoscopic Technique in S.E.M.
Authors: Wang D. , Feng Y. , Lu H. 
Published: June 2020

The principle of 3-D reconstrution for SEM image is not so conplex, ie. the SEM image of polar project is treated with a rectangular coordinate, however,it accuracy is an attractatble topic.The accuracy of a stereopair is effected by following factors:(1) Sample's position:Image’s field depth of SEM is determined by
Development of a New Digital Fe SEM
Authors: Ohi M. , Harasawa K. , Niikura T. , Okazaki H. , Ishimori Y. , Miyokawa T. , Nakagawa S. 
Published: June 2020

By combining a conical type field emission gun and an auto gain controlled noise cancelling system, we have developed three types of digital FESEMs equipped with a digital imaging processor and three different sized specimen chambers each with a stage.It is known that when a cold field emission gun (C-FEG) with a W (310) single crystal tip is used at a vacuum pressure of 10-10 torr, the emission current constantly fluctuates by 5 to 10% due to the adsorbed gas, etc. on the tip surface.Since the probe current in an FESEM equipped with this C-FEG fluctuates to the same extent, the noise caused by emission current fluctuation (emission noise) appears on secondary electron images (SEI) and backscattered electron images (BEI).In order to eliminate emission noise, an aperture (noise cancelling aperture or N/C aperture) installed under the C-FEG detects emission current fluctuation and inputs it to the differential amplifier of the video amplifier system for SEI or BEI on conventional FESEMs.With FESEMs, however, when the accelerating voltage is change in the range from 0.5 to 30 kV, the virtual source of an FEG using Butler type electrodes moves several tens of centimeters on the optical axis. Moreover, the probe current is changed from 10-13 to 10-10 A by changing the excitation current of the condenser lens. For these two reasons, there have been adopted such methods as installing an N/C aperture in two positions (under the C-FEG and at the objective lens aperture position) and controlling the amplifier value of the noise cancelling system and condenser lens excitation by ROM data.
The Advantages of Cryotechniques: Application To Bioluminescent Cells
Authors: Nicolas Gisèle , Bassot Jean-Marie , Nicolas Marie-Thérèse 
Published: June 2020

The use of fast-freeze fixation (FFF) followed by freeze-substitution (FS) brings substantial advantages which are due to the extreme rapidity of this fixation compared to the conventional one. The initial step, FFF, physically immobilizes most molecules and therefore arrests the biological reactions in a matter of milliseconds. The second step, FS, slowly removes the water content still in solid state and, at the same time, chemically fixes the other cell components in absence of external water. This procedure results in an excellent preservation of the ultrastructure, avoids osmotic artifacts,maintains in situ most soluble substances and keeps up a number of cell activities including antigenicities. Another point of interest is that the rapidity of the initial immobilization enables the capture of unstable structures which, otherwise, would slip towards a more stable state. When combined with electrophysiology, this technique arrests the ultrastructural modifications at a well defined state, allowing a precise timing of the events.We studied the epithelium of the elytra of the scale-worm, Harmothoe lunulata which has excitable, conductible and bioluminescent properties. The intracellular sites of the light emission are paracrystals of endoplasmic reticulum (PER), named photosomes (Fig.1). They are able to flash only when they are coupled with plasma membrane infoldings by dyadic or triadic junctions (Fig.2) basically similar to those of the striated muscle fibers. We have studied them before, during and after stimulation. FFF-FS showed that these complexes are labile structures able to diffentiate and dedifferentiate within milliseconds. Moreover, a transient network of endoplasmic reticulum was captured which we have named intermediate endoplasmic reticulum (IER) surrounding the PER (Fig.1). Numerous gap junctions are found in the membranous infoldings of the junctional complexes (Fig.3). When cryofractured, they cleave unusually (Fig.4-5). It is tempting to suggest that they play an important role in the conduction of the excitation.
Selection of Em Analysis Points Using the Euclidian Distance Map
Authors: Bright David S. 
Published: June 2020

An image with morphological information, such as a backscatter electron image, can be acquired quickly to provide points for spectroscopic analyses that usually take more instrument time. It is desirable to have the analysis points be in the interior of the particles or objects of interest. The Euclidian distance map is applied directly to this problem to maximize the distance of the analysis sites from any part of the object perimeter.The first step in using an electron image to select points for spectroscopic analysis is often to make a binary image of the original, in which picture elements (pixels) corresponding to particles, or the crystalline phase of interest, for example, are white, while all other pixels, corresponding to background, are black. The second step is to select analysis points for each particle or ‘blob’ (group of contiguous pixels) in the binary image. The centroid or center of area (at tips of arrows, Fig. 1) is used when one analysis point is desired and the blob is sufficiently convex or straight (upper left arrow, Fig. 1). However, if the blobs are curved or have indentations or holes, the centroid may actually lie in the background rather than in the area to be analyzed (middle and lower arrows, Fig. 1).
A Computer Graphic Method to Enhance the Display and Interpretation of Three-Dimensional Data
Authors: Dryden Kelly A. 
Published: June 2020

Three-dimensional density information derived from electron micrographs may reveal complex structural features which are difficult to interpret from one or more two-dimensional views. Displaying a series of static views on a graphics device in quick succession provides an effective means to examine the structure dynamically and in a way which enhances the depth perception.Digital images derived from three-dimensional models are transfered to the memory of a 1280x1024 resolution (8-bit pixel) color raster graphics device (Lexidata 3400, Adage Inc., Billerica, MA) and displayed on a 19 in. color monitor at a 25-30 Hz interlaced refresh rate. Individual pixels are displayed as one of 256 different colors or grey levels from a palette of up to 224—1 combinations. An entire series of images is loaded into the graphics memory in a sequential order, usually in rows. The displayed series is zoomed up to focus on a single frame and separate frames are displayed in appropriate sequence by panning to different regions of the graphics memory. The frequency at which each frame can be displayed is adjustable and only limited by the refresh rate of the monitor. Such dynamic image sequences can be photographed with a standard video camera and replayed on a television monitor with a video cassette recorder. The programs for displaying image data are written in FORTRAN and have been implemented on a VAX/VMS 8550 minicomputer (Digital Equipment Corp., Maynard, MA).
A Photoelectron Microscope for Applications in the Biological Sciences
Authors: Griffith O. Hayes , Rempfer Gertrude F. , Skoczylas Walter P. 
Published: June 2020

A photoelectron microscope (photoemission electron microscope, PEM or PEEM) has been developed for the study of organic and biological surfaces. The basic experiment is illustrated in Figure 1A. The specimen is placed on a solid conductive surface, inserted in the PEM, and subjected to UV light (rather than an electron beam as in TEM or SEM). A simplified diagram of the PEM is shown in Figure 2B (note the specimen mount is inverted). The emitted electrons are accelerated by the electric field between the specimen (at -30 kV) and the anode (at ground potential). After passing through the anode aperture, the electrons are focused by electron lenses resembling those of a transmission electron microscope.An engineering drawing of the instrument is shown in Figure 1C. It differs from the earlier metallurgical instruments in several respects. This is an oil-free ultra high vacuum instrument to minimize contamination of specimen surfaces. The objective, intermediate and projector lenses are unipotential electrostatic lenses, and are described elsewhere. The theoretical resolution limit of this instrument is on the order of 5 nm for representative energy current densities and energy distributions encountered with threshold illumination (i.e. Hg short arc lamps). The experimental resolution is presently within a factor of two of this figure. Additional improvements in resolution can, in principle, be made with a corrected electron optical system. Magnifications up to 250,000X have been recently achieved with this instrument in combination with an image processor.