bluuebunny/crossref_metadata_2025 huggingface dataset:
In-Lens Low-Loss Electron Detector for the Upper Specimen Stage in the Scanning Electron Microscope
Authors: Wells Oliver C. , LeGoues Françoise K. , Hodgson Rodney T.
Published: June 2020

For the best resolution in either the scanning electron microscope (SEM) or the transmission electron microscope (TEM) the sample must be mounted in the high-field region of a condenser-objective lens. Detectors for either the secondary electrons (SE) or the backscattered electrons (BSE) in the SEM must allow for the fact that both of these are strongly deflected by the focusing magnetic field of the lens. Typically the SE are collected above the lens, while the BSE are collected using either diode(s) or scintillator(s) between the polepieces.

Low-loss electrons (LLE) are scattered from a solid target with an energy loss of less than a few percent of the incident beam energy. These can be collected from a steeply tilted sample from below the exit polepiece of a condenser-objective lens. A suggestion to use the second half of the lens field as an energy filter was shown to by Munro to be unlikely to work because the chromatic dispersion of this part of the lens field is insufficient.

The magnetic field of a condenser-objective lens can provide energy filtering as follows.A flat sample is mounted at typically 25° to 30° from the horizontal at or near the center of the lens. Figure 1 shows the trajectories of the electrons scattered with no loss of energy as calculated by Munro. These electrons are confined within a “containment region” with a well-defined boundary beyond which they cannot go. If a suitable detector is placed just inside the surface of this region then it will collect LLE. The slower BSE are confined within a smaller region and so are not collected.
Scattering of Electrons at High - Pressure and Restoration of Image Contrast in High Pressure Scanning Electron Microscopy
Authors: Shah J. S. , Durkin R. , Farley A. N.
Published: June 2020

It is now possible to perform High Pressure Scanning Electron Microscopy (HPSEM) in the range 10 to 2000 Pa. Here the effect of scattering on resolution has been evaluated by calculating the profile of the beam in high pressure and assessing its effect on the image contrast . An experimental scheme is presented to show that the effect of the primary beam ionization is to reduce image contrast but this effect can be eliminated by a novel use of specimen current detection in the presence of an electric field. The mechanism of image enhancement is discussed in terms of collection of additional carriers generated by the emissive components.

High Pressure SEM (HPSEM) instrumentation is establishing itself as commercially viable. There are now a number of manufacturers, such as JEOL, ABT, ESCAN, DEBEN RESEARCH, selling microscopes and accessories for HPSEM. This is because high pressure techniques have begun to yield high quality micrographs at medium resolution.

To study the effect of scattering on the incident electron beam, its profile - in a high pressure environment - was evaluated by calculating the elastic and inelastic scattering cross sections for nitrogen in the energy range 5-25 keV. To assess the effect of the scattered beam on the image contrast, the modification of a sharp step contrast function due to scattering was calculated by single scattering approximation and experimentally confirmed for a 20kV accelerated beam.
Dependence Upon Thickness of Passivation in Low Voltage SEM Inspection of Electronic Devices
Authors: Ikeda S. , Maruse S. , Uchikawa Y.
Published: June 2020

It was reported that SEM observation of micro electronic devices can be made without serious charging disturbances under a condition of low primary electron energy (Ep=1keV). Besides, the SEM can visualize a voltage profile of electrodes under a passivation layer as a contrast in the secondary electron images of the devices. This contrast appears in the first frame of imaging corresponding to the applied voltage, and disappears when the total dose of irradiated electrons exceeds a critical value. By observing the contrast variations, it was found that the total dose (Dm) of electrons is a linear function of the DC voltage (V) applied to the electrodes under the passivation layer. Utilizing this linearity, unknown local electrode voltage can be estimated, even when the electrodes exist under the passivation layer. However the coefficient of linearity depends on thickness of passivation. In this work we investigated into the dependence of Dm-V characteristics upon the thickness.

A test specimen for SEM observation was prepared as follows. As shown in Fig.l, copper electrodes separated by a 0.1mm gap in shape of a hair-pin were evaporated on a quartz glass and then a layer of Si-oxide with varied thickness was deposited upon the surface of electrodes by means of the eximer laser abrasion. Selecting four points (A,B,C,D in Fig.l) of different thicknesses (A:4870A, B:4120A, C:3080A, D:2180A) on the surface of Si-oxide, while appling the voltage (V) between inner and outer electrodes under the passivation layer, the total dose (Dm) irradiated over the specimen untill the contrast of secondary electron image diminishes (Fig.2) was measured. As shown in Fig.3, there exist linearities between Dm and V for various values of the thickness (t) of Si-oxide. Futhermore, the rate of the total dose per voltage (Dm/V) changes depending on t (Fig.4). It should be noted that the total rate per voltage decreases linearly against the thickness.
In Situ Scanning Electron Acoustic Microscopy
Authors: Franceschi J.L. , Murillo R. , Bastié A. , Ez-Zejjari M. , El Abdary H. , Boughanmi N.
Published: June 2020

A mini scanning electron microscope, the MEBIS [1] (“Microscope Electronique à Balayage In situ”) is used to inspect “in situ” bulk specimens. The electron-optical column which has been made small and light, can be placed just over the sample. With a specially designed control circuitry, a chopped electron beam is used as a source of thermoelastic waves at the surface of specimen. The induced thermal and ultrasonic waves are used for detection and, by combining this acoustic signal with the scanned electron beam, imaging of the subsurface is possible.

The accelerating potential used is 10 kV and the equivalent source of thermoelastic waves is less than one micrometre in metals. Below the megahertz range for the chopped beam (frequency f), the wavelength of sound λa is greater than that of the thermal waves λg. Approximately, only thermal waves determines the spatial resolution [2]. These waves are damped with an experimental decay dT = Cte.f−1/2, and the spatial resolution is similar to dT, typically five micrometres in metals for the beam modulation frequency of 100 kHz, with linear signal detection [3]. Above the MHz range, submicronic spatial resolution is possible. But the sensitivity is also a function of the frequency. The signal to noise ratio (S/N) is proportionnal to f−1 (low frequency). A compromise must be made between S/N ratio and satisfactory spatial resolution, since for bulk specimens the signal decays with the thickness [4].
T-Max and TRI-X: Comparisons of Sheet Film Emulsions for Use in SEM Photography
Authors: Long J.C.
Published: June 2020

The potential benefits of Kodak's Tabular Grain Emulsion Films (brand name: T-MAX) has resulted in our lab considering a switch from Kodak TRI-X 4×5 sheet film to Kodak T-MAX 4x5 sheet film for use in SEM photography. The current regime is TRI-X sheet film developed in D-19 diluted 1:2. Processing is at 20°C in large (4l) tanks with N2 burst agitation. The procedure used for this study was T-MAX and TRI-X sheet film processed in T-MAX RS developer; using the same large tank, and No burst system, but at temperatures ranging from 20° -24°C. The potential benefits are: 1) Improved image quality; tabular grain emulsions are purported to have improved sharpness, a finer grain at a given film speed, and better tonal separation than previous emulsions. 2) Ease of use; T-MAX RS is a highly miscible liquid concentrate which can be used at 20°-24°C. The primary temperature recommendation is 24°C; this would reduce the need for chilled water at our facility.

The initial comparison was made using Kodak TRI-X and Kodak T-MAX 400 sheet film. Exposures were made using a JEOL T330A equipped with a high resolution photo CRT and waveform monitor (WFM). Brightness settings were determined using the WFM in the procedure described by Holm. Four sets of eight exposures each were made for both T-MAX 400 and TRI-X. A set consisted of one sheet of film exposed at each of the zones represented by the lines of the WFM. One set of each type of film was processed at each of the four specified temperatures,(20°, 21° 22°,24°, using T-MAX RS developer, at the time recommended by Kodak. Negative density was determined using a Zeiss Axiophot equipped with a MPM 20 Photometer. The percent value of transmitted light (%T) was converted to diffuse density (D) using the formula D=Log 1/T. The calculated diffuse density was plotted against the brightness line position on the WFM. Granularity was examined by visual comparison using 12x enlargements from T-MAX and TRI-X negatives of similar density.
Correlation of Pore Structure and Permeability by SEM-Image Analysis
Authors: Callender C. A. , Dawson Wm. C. , Funk J. J.
Published: June 2020

The geometric structure of pore space in some carbonate rocks can be correlated with petrophysical measurements by quantitatively analyzing binaries generated from SEM images. Reservoirs with similar porosities can have markedly different permeabilities. Image analysis identifies which characteristics of a rock are responsible for the permeability differences. Imaging data can explain unusual fluid flow patterns which, in turn, can improve production simulation models.

Analytical Scheme

Our sample suite consists of 30 Middle East carbonates having porosities ranging from 21 to 28% and permeabilities from 92 to 2153 md. Engineering tests reveal the lack of a consistent (predictable) relationship between porosity and permeability (Fig. 1). Finely polished thin sections were studied petrographically to determine rock texture. The studied thin sections represent four petrographically distinct carbonate rock types ranging from compacted, poorly-sorted, dolomitized, intraclastic grainstones to well-sorted, foraminiferal,ooid, peloidal grainstones. The samples were analyzed for pore structure by a Tracor Northern 5500 IPP 5B/80 image analyzer and a 80386 microprocessor-based imaging system. Between 30 and 50 SEM-generated backscattered electron images (frames) were collected per thin section. Binaries were created from the gray level that represents the pore space. Calculated values were averaged and the data analyzed to determine which geological pore structure characteristics actually affect permeability.
Optimization of LaB6 Cathode Tip Shape for Maximum Brightness Over Lifetime
Authors: Christman Locke
Published: June 2020

LaB6 cathodes are widely used as high brightness cathodes in electron microscopy and are capable of providing about five times the brightness of a tungsten hairpin filament. It is desirable to optimize the shape of the LaB6 tip to provide the highest possible brightness and to insure that this high level of brightness is maintained over the life of the cathode.

It is well known that a high brightness electron beam is important in obtaining ultimate resolution in electron microscopy. Brightness is defined as the current density per unit solid angle, or amperes per square centimeter per steradian, in the electron beam. In electron microscopy, one would like to obtain the maximum possible brightness for the particular electron gun. Brightness is a conserved quantity, meaning that as the beam traverses the column, brightness can not be gained, only lost. Therefore, one must begin with the brightest possible cathode in order to obtain the best possible electron beam brightness.

Much work has been done to determine the optimum LaB6 cathode tip shape and crystallographic orientation which will provide the highest brightness over cathode lifetime. The purpose of this is to review some of the previous results, present further data, and draw conclusions as to the optimum LaB6 cathode tip shape for high sustained brightness over cathode life. Nearly all commercially available LaB6 cathodes for electron microscopy employ an axially oriented LaB6 <100> crystal with a conical tip. Most are made with a full cone angle of 2α=90° (Figure 1). Some have a small radius, hemispherical point at the apex of the cone, while others simply have a small diameter truncation (flat) on top of the cone. The geometrical parameters affecting cathode brightness which will be considered here are hemispherical tip radius (R) and flat diameter (ϕ). Of primary interest is the dependence of brightness over lifetime with the variation of these parameters, and the comparison between the hemispherical and the flat tips.
Performance and Capabilities of a New, Integrated SEM Image Store
Authors: Gross U. , Mulder J.C.
Published: June 2020

Loosely-coupled, add-on image stores have been used in electron microscopy for some years. Only recently have they been more closely integrated into the system architecture. With the introduction of the new XL series of scanning electron microscopes Philips goes one step further by making the image store the central image information switchboard with one common user interface for all microscope functions (Fig. 1).

Fig. 2 shows the functional structure of the XL image store.

Each of the dual-port, dual-speed memory boards (MEM) stores two 8 bit planes of 680 lines (of which 525 are used complying with the US TV standard) containing 768 pixels each. Up to four boards can be used. It is possible to couple four image planes to form one high definition display area of 1050 lines and 1572 pixels which can be fully used for image acquisition and for hardcopy. The monitor then shows either a full image in normal definition or a quarter of an image in high definition, which can be positioned at will within the image area.

Signal transfer is performed by three 16 bits wide image data buses, one of which (MAIN DISPLAY BUS) is always driven at TV rate, whereas the other two (SIGNAL PROCESSOR and AUX DISPLAY BUS) follow the speed of the input signal. This extremely flexible bus concept not only allows normal recursive averaging and integration as described by O'Keefe et.al., but also two-dimensional convolutions on acquired images within only a few TV cycles. Different processing schemes can be chosen inside and outside the selected area.
A Macintosh Interface for the Cameca Camebax-Micro Electron Microprobe
Authors: Henderson Carl E.
Published: June 2020

Over the past few years it has become apparent in our multi-user facility that the computer system and software supplied in 1985 with our CAMECA CAMEBAX-MICRO electron microprobe analyzer has the greatest potential for improvement and updating of any component of the instrument. While the standard CAMECA software running on a DEC PDP-11/23+ computer under the RSX-11M operating system can perform almost any task required of the instrument, the commands are not always intuitive and can be difficult to remember for the casual user (of which our laboratory has many). Given the widespread and growing use of other microcomputers (such as PC’s and Macintoshes) by users of the microprobe, the PDP has become the “oddball” and has also fallen behind the state-of-the-art in terms of processing speed and disk storage capabilities. Upgrade paths within products available from DEC are considered to be too expensive for the benefits received. After using a Macintosh for other tasks in the laboratory, such as instrument use and billing records, word processing, and graphics display, its unique and “friendly” user interface suggested an easier-to-use system for computer control of the electron microprobe automation. Specifically a Macintosh IIx was chosen for its capacity for third-party add-on cards used in instrument control.
Low - Voltage Scanning Electron Microscopy Imaging, Secondary and Backscatter, With Microchannel Plate Detector
Authors: Powers Galen , Cochran Ray
Published: June 2020

The capability to obtain symmetrical images at voltages as low as 200 eV and beam currents less than 9 pico amps is believed to be advantageous for metrology and study of dielectric or biological samples. Symmetrical images should allow more precise and accurate line width measurements than currently achievable by traditional secondary electron detectors. The low voltage and current capability should allow imaging of samples which traditionally have been difficult because of charging or electron beam damage.

The detector system consists of a lens mounted dual anode MicroChannel Plate (MCP) detector, vacuum interface, power supplies, and signal conditioning to interface directly to the video card of the SEM. The detector has been miniaturized so that it does not interfere with normal operation of the SEM sample handling and alternate detector operation. Biasing of the detector collection face will either add secondaries to the backscatter signal or reject secondaries yielding only a backscatter image. The dual anode design allows A−B signal processing to provide topological information as well as symmetrical A+B images.

Photomicrographs will show some of the system capabilities. Resolution will be documented with gold on carbon. Variation of voltage, beam current, and working distance on dielectric samples such as glass and photoresist will demonstrate effects of common parameter changes.
Scanning Transmission and Computer-Aided Volumic Electron Microscopy: 3D Modeling of Entire Cells by Electronic Imaging
Authors: Bron Cph. , Gremillet Ph. , Launay D. , Jourliny M. , Gautschi HP. , Bächi Th. , Schüpbach J.
Published: June 2020

The digital processing of electron microscopic images from serial sections containing laser-induced topographical references allows a 3-D reconstruction at a depth resolution of 30 to 40 nm of entire cells by the use of image analysis methods, as already demonstrated for Transmission Electron Microscopy (TEM) coupled with a video camera. (Cf ref)

We decided to use a Scanning Transmission Electron Microscope (STEM) to get higher contrast and better resolution at medium magnification. The scanning of our specimens at video frequencies is an attractive and easy way to link a STEM with an image processing system (see Fig 1) but the hysteresis of the electronic spools responsible for the magnetic deviation of the scanning electron beam induces deformations of images which have to be modelized and corrected before registration. Computer algorithms developed for image analysis and treatment correct the artifacts caused by the use of STEM and by serial sectioning to automatically reconstruct the third dimension of the cells.(see Figs 2 and 3) They permit the normalization of the images through logarithmic processing of the original grey level information. The automatic extraction of cell limits allows to link the image analysis and treatments with image synthesis methods by minimal human intervention. The surface representation and the registered images provide an ultrastructural data base from which quantitative 3-D morphological parameters, as well as otherwise impossible visualizations, can be computed.
Application of Cross Entropy and Factorial Analysis to Image Processing
Authors: Trebbia P.
Published: June 2020

Most of the time, the problem that image analysis has to face is the following : from a given data set obtained with independant measurements, how to extract the signal (the “useful information”) which is mixed with a background (coming from the object itself or from the detector) and statistical noise? If a pre-knowledge of the specimen (or of the experimental procedure) gives some reasonable hypothesis about an empirical mathematical description of the background and of the noise, then, one can try some “fitting” method (maximum likelihood for example) in order to solve the problem. But if no a-priori model is available, one is reduced to try to understand the “meaning” of the images through an analysis of the information content of the data set. Two main statistical approaches can be of some help in that process:

) first, one can measure from the histogram of the data set some characteristic statistical parameters (mean and variance) and compare it with a gaussian histogram of same mean and variance which would be obtained under the same experimental conditions (same number of detected electrons for example) in a pure random process, that is with a “neutral” specimen showing absolutely no contrast. Then from these two histograms, one may estimate the relative cross entropy, that is the information value added by the real presence of a given object in the specimen chamber. Moreover, one can make a 2D-plot of this information in order to localize the pixels, in the data set, whose intensities significantly differ from a pure random process.

) the second possibility is to make a variance analysis of the data set : if we have a pre-knowledge that some of the images in this set do not contain the “contrast information” we are looking for, then, there must be some quantitative difference between these images and the other ones. Among the various algorithms available from multivariate statistics, the factorial analysis has been proved to be suited to this kind of analysis.
Beam-Induced Indeterminacies In The Ivem
Authors: Hobbs Linn W.
Published: June 2020

Intermediate-voltage electron microscopes accelerate electrons to energies U between 200 keV and 600 keV to take advantage of a U-3/8 improvement in resolving power which enables sub-0.2nm atomic structure projections to be routinely imaged. This exciting prospect is, however, purchased at the price of uncertainties in the integrity of the images obtained, because the investigating probe unavoidably perturbs the structure which is being imaged. Such perturbations have been relegated historically to the anecdotal realm of “radiation effects” but are really a perverse manifestation of the Uncertainty Principle. That electron microscopists are able to resolve the structure of solids at all is a tribute to the strength and mutliplicity of atomic bonds in solids and the large “recoiless fraction” (in the parlance of nuclear spectroscopies like the Mossbauer effect) for which the whole solid, and not an individual atom, recoils from the impact of the investigating probe.

Atomic structure is sensitive to the impact of incident IVEM electrons because they lose energy (at a rate of order 1 GeV/m) in traversing a solid, a small portion of which is available as kinetic energy to restructure atomic positions. About 98% of the energy loss goes into electronic excitations which can in certain materials (notably organic materials, halides, silicates and almost anything explosive) destabilize atomic positions within the specimen interior with unnervingly high efficiency by radiolytic processes. Analogous radiolytic loss or restructuring of surface atoms, whose bonding constraints are fewer than for atoms in the interior, has been coined “desorption induced by electronic transitions” (DIET). Of the remaining 2% of the energy loss, which is transferred instead to atomic nuclei, most goes into the generation of heat (the eventual fate of most non-radiative electronic transitions as well), but about 1 part in 105 (or 1 part in 107 overall) is available to generate atomic displacements ballistically, by direct knockon: at the surface for almost all solids examined by IVEM (leading to sputtering) and in the interior for many medium atomic-weight solids.
The Structure of The 70S E. Coli Rtoosome In Ice
Authors: Penczek Pawel , Srivastava Suman , Frank Joachim
Published: June 2020

We have obtained two reconstructions of the 70S ribosomal subunit embedded in ice using the random-conical method on particles showing two distinctive views.

Ribosomes were applied to grids covered with thick holey carbon film whose holes were in turn covered with a second, thin carbon film. The frozen-hydrated preparation was done as described previously using GATAN cryo-transfer equipment and specimen holder on a Philips EM420. The images were taken in pairs at 2μm defocus and a dose of less than 10 e-1/Å2. The first was taken with the specimen tilted to 50°, the second untilted. A total of 838 particles from two micrograph pairs were selected for image analysis.

A new reference-free alignment algorithm was used to align the 0°-images. In the subsequent multivariate statistical analysis and factor-space based hierarchical classification, several distinct groups were found, two of which (averages, Fig. 1) with memberships above 10% were selected for two separate 3D reconstructions. The averages were found to have a resolution of 3.3 nm as established by phase residual analysis. For computing the reconstruction, we used an iterative scheme that is based on a Chi-square minimization. In this way, we were able to reduce distortions caused by the missing cone as well as by large gaps in angular spacing.
Video Graphics and High-Voltage Electron Microscopy For Analysis of Microtubule Distributions In Fixed Cells
Authors: Mcintosh Richard , Mastronarde David , McDonald Kent , Ding Rubai
Published: June 2020

Microtubules (MTs) are cytoplasmic polymers whose dynamics have an influence on cell shape and motility. MTs influence cell behavior both through their growth and disassembly and through the binding of enzymes to their surfaces. In either case, the positions of the MTs change over time as cells grow and develop. We are working on methods to determine where MTs are at different times during either the cell cycle or a morphogenetic event, using thin and thick sections for electron microscopy and computer graphics to model MT distributions.

One approach is to track MTs through serial thin sections cut transverse to the MT axis. This work uses a video camera to digitize electron micrographs of cross sections through a MT system and create image files in computer memory. These are aligned and corrected for relative distortions by using the positions of 8 - 10 MTs on adjacent sections to define a general linear transformation that will align and warp adjacent images to an optimum fit. Two hundred MT images are then used to calculate an “average MT”, and this is cross-correlated with each micrograph in the serial set to locate points likely to correspond to MT centers. This set of points is refined through a discriminate analysis that explores each cross correlogram in the neighborhood of every point with a high correlation score.
Automatic Video Thresholding for Individual Particle Analysis Using a Computer-Controlled Analytical Scanning Electron Microscope
Authors: Germani Mark S.
Published: June 2020

Automated analytical scanning electron microscopes (ASEM) and electron microprobes are extremely useful for analyzing multi-phase particulate dispersions. Global thresholding is often used to discriminate particles from the supporting substrate. This is usually done by manually setting a video threshold while viewing the video signal waveform. The problems with this approach are that the threshold is operator dependent, requires that the instrument be stable and the background remain constant during the analysis, and it can be very difficult to reproducibly set the threshold near the background signal which is essential for locating low contrast features such as submicrometer particles on filter substrates. Local thresholding on a pixel-by-pixel basis eliminates many of the problems associated with global thresholding but is a time consuming and computer intensive process.
A program for simulation of changes in diffraction patterns with crystal rotations
Authors: Mijlhoff F.C. , Zandbergenl H.W.
Published: June 2020

Orientation of crystals for HREM is done in diffraction mode. To do this efficiently thorough knowledge of the electron microscope and the reciprocal lattice of the investigated material is essential. With respect to the electron microscope extensive training is required to obtain the ability to tilt a crystal in the desired orientation. Familiarity with the reciprocal lattice of the investigated materials has to be obtained by tilt experiments on a relatively large number of crystals in the electron microscope. Even for experienced electron microscopists this can be very time consuming.

In order to be able to practice tilt experiments without using the electron microscope, a program to simulate the electron microscope in diffraction mode was developed. The inexperienced electron microscopist may use the program to practice tilting of crystals. The experienced microscopist can use the program to familiarize with the reciprocal lattice of materials, which have not been studied by him before.
Measurement of feature clustering in images
Authors: Russ John C.
Published: June 2020

The spatial distribution of features in an image is often interesting, but not simple to characterize. Mapping of the image into a different space (e.g., Fourier or Hough) offers direct information on various regularities in feature spacing or alignment, but does not deal directly with the individual features. Two other approaches are available; each has advantages and drawbacks, which are discussed here.

Schwarz & Exner determine the spatial coordinates of the centroids of features, and sort them to locate the nearest neighbor for each feature present, constructing a distribution plot of the frequency of nearest neighbor distances. Figures 1 and 2 show an example. The three fields in Figure 1 contain, respectively, features which are well-spaced from each other, randomly arranged on the plane, and clustered together. For the random distribution of points, the histogram of nearest neighbor distances is a Poisson distribution, and the mean value is 0.5/NA1/2, where NA is the number of features divided by the area of the image.
Quantitative Scanning Electron Microscopy of the Cellular Structure of Wood
Authors: Reine Barbara A. , Fowler Norman J. , Fisher R. M.
Published: June 2020

The physical properties of wood, such as density, moisture content, tensile, compression and shear strength, elastic modulus and anisotropy all vary considerably between different species of wood. These variations are reflected in the long standing differentiations into hard and soft woods that have been established as well as quality classifications or commercial grades such as clear grain, select, structural etc. that are commonly used. These variations in properties arise from differences in the size, shape and distribution of the cells, as well as in the thickness of the cellulose-lignin walls that enclose them.

Scanning electron micrographs that are representative of the variations in cellular structure that exist between woods are shown in Figure 1 for ultrasoft hard maple and ultrasoft cork oak. These higher magnification images illustrate the duplex cell configuration that is required to sustain the growth of trees and support their height. Although the differences in cell structure are quite apparent in the micrographs, any quantitative interpretation of the various properties mentioned above requires detailed measurements of specific microstructural components to obtain statistically significant measurements of the relevant structural components.
The Scanning Photoelectron Microscope : A Novel Tool in Surface Science
Authors: von Oertzen A. , Rotermund H.H. , Jakubith S. , Kubala S. , Ertl G.
Published: June 2020

Photoelectron microscopes using electron optics had been built long before. Until recently these microscopes were not widely used in surface science due to unsufficient vacuum conditions as well as weak image intensifying devices. In this paper we will present a new approach to photoelectron microscopy, the Scanning Photoelectron Microscope (SPM).

Photoelectron emission will occur as soon as the photon energy is higher than the work function on the illuminated area. Since work functions never exceed 6.5 eV, ultraviolet (UV) light with λ ≥ 190 nm will be appropriate. This kind of radiation is a very gentle probe, even for sensitive adlayers.

The experimental setup is shown schematicaly in Fig. 1. A UV light optics outside the ultra high vacuum (UHV) system focusses the actual 30 W Deuterium discharge lamp through a grid monochromator onto a small aperture (50 to 400 microns). The aperture hole is projected with a reflecting microscope objective (Schwarzschild type) onto the surface of the sample yielding a lateral resolution of about 3 microns.
Photoemission Electron Microscopy Experiments with the Balzers Ke3 Metioscope
Authors: Hammond C. , Imam M. A.
Published: June 2020

In the Balzers KE3 ’Metioscope’, photoelectron emission is stimulated by the action of four mercury arc U.V. lamps, the light from which is reflected onto the specimen surface from the anode plate. The specimen may be heated in a wire-wound furnace enclosure or by an electron beam. In both cases temperatures of the order of 1200°C are attainable. Surface oxidation and contamination may be removedin situby the use of an argon ion and/or neutral particle gun. The emitted electrons are imaged using electromagnetic lenses onto a fluorescent screen which is linked to a TV camera and recorder. Hence dynamic changes occurring at high temperatures or during heating or cooling may be recorded continuously.

This paper will first briefly review recent published and unpublished work carried out using the Metioscope, which illustrate both the capabilities and limitations of the technique. Secondly, the results of a series of on-going experiments on ferrite nucleation and growth from austenite grain boundaries in low carbon alloy steels will be described and illustrated with video-recordings. The steels were austenitised at 975-950°C and either (a) rapidly cooled at 775-725°C and transformed isothermally or (b) continuously cooled at rates in the range 0.5-0.05°C/sec.
An Electron Diffraction Study on Litnerized Potato Starch
Authors: Jésior Jean-Claude , Vuong Roger , Chanzy Henri
Published: June 2020

Starch is arranged in a crystalline manner within its storage granules and should thus give sharp X-ray diagrams. Unfortunately most of the common starch granules have sizes between 1 and 100μm, making them too small for an X-ray study on individual grains. There is only one instance where an oriented X-ray diagram could be obtained on one sector of an individual giant starch granule. Despite their small size, starch granules are still too thick to be studied by electron diffraction with a transmission electron microscope. The only reported study on starch ultrastructure using electron diffraction on frozen hydrated material was made on small fragments. The present study has been realized on thin sectioned granules previously litnerized to improve the signal to noise ratio.

Potato starch was hydrolyzed for 10 days in 2.2N HCl at 35°C, dialyzed against water until neutrality and embedded in Nanoplast. Sectioning was achieved with a commercially available low-angle “35°” diamond knife (Diatome) after a very carefull trimming and a pre-sectioning with a classical “45°” diamond knife. Sections obtained at a final sectioning angle of 42.2° (compared with the usual 55-60°) and at a nominal thickness of 900Å were collected on a Formvar-carbon coated grid. The exact location of the starch granules in their sections was recorded by optical microscopy on a Zeiss Universal polarizing microscope (Fig. 1a). After rehydration at a relative humidity of 95% for 24 hours they were mounted on a Philips cryoholder and quench frozen in liquid nitrogen before being inserted under frozen conditions in a Philips EM 400T electron microscope equipped with a Gatan anticontaminator and a Lhesa image intensifier.
Chitin Systems Studied by Electron Diffraction, Diffraction-Contrast Electron Microscopy and Lattice Imaging
Authors: CHANZY Henri , Gaill Francoise , Giraud-Guille Marie-Madeleine , Persson Jan , Sugiyama Junji , Vuong Roger
Published: June 2020

Chitin the poly β (1-4)-N Acetyl D glucosamine is widespread in nature and occurs normally as a crystalline fibrillar substance. As opposed to most of the crystalline polysaccharides, chitin is quite resistant to the electron beam. In particular, at room temperature, accumulated doses as high as 200 elec/nm2 at 120 kV can be used to record successful images showing crystalline details. For this reason, chitin can be studied without too much difficulty by electron diffraction (ED), diffraction contrast transmission electron microscopy (DCTEM) and lattice imaging. This study presents some of the diversity of chitin morphology.

Several chitin rich specimens were studied. They include : 1) cross sections of an ovipositor from an ichneumon fly Rhyssa persuosaria ; 2) cross sections of fragments of demineralized crab cuticle ; 3) cross sections of a tube from the vestimentiferan worm Tevnia jerichonana ; 4) bundles of chitin microfibrils isolated from Tevnia tube fragments after deproteinization.
The First Experience with new Small-Sized Commercial Tem (TEM -100) and Biological Specimens
Authors: Vukovié Jovan
Published: June 2020

Conventional electron microscope TEM -100 (Made by “ELECTRON”, Sumy, USSR; Fig. 1) was presented at the XI Int. Congress on Electron Microscopy (Kyoto) by I.S. Lyalko et al. (1,2). The purpose of the microscope constructors were to design a small-sized general conventional TEM for various application fields. The microscope have mini lenses, which winding is placed in closed casing and soaked in working liquid (low boiling temperature) but upper part of the casing being water cooled.

In this communication we gave our first experience and impression as a customer, beginning from the montage, the instruction and the testing of the microscope to our application in the field of biological specimens. Just after montage of the microscope on the second floor, the test of the point resolution power was performed by Ir specimen. It was achieved 0.5 nm (Fig. 2 and 3) on the roll film (ORWO 22 DIN) with 300 OOOx magnification and anticontamination device. The ultimate vacuum (about 10exp-6 mm Hg, ion discharge pump) also achieved using large trap cooled by liquid nitrogen.
Optimal 3D Representation of Serial Transmission Electron Microscopy Data
Authors: Leitao Carlos , Trogadis Judy , Stevens John
Published: June 2020

Three-dimensional representations of serial TEM data can provide useful visualization of morphological detail and spatial distributions of biological structures. The standard method of wireframe representation of 3D outlines of membrane contours can prove to be visually confusing. Thus alternate modelling for recreating biological surfaces from serial TEM data sets were investigated using the Icar 80.8 workstation (l).

Serial TEM micrographs were collected from a PC12 cell whose nucleus had an invagination which contained organelles and microtubules. This nuclear tube is believed to play a role in nucleo-cytoplasmic exchange.

Contours representing membrane boundaries of a nuclear tube as well as organelles found therein were traced and digitized from a set of serial electron micrographs using a data collection system described in (2). Lines representing the axes of microtubules were also collected.
Ballistic Electron Emission Microscopy
Authors: Hecht M.H. , Bell L.D. , Kaiser W.J.
Published: June 2020

Ballistic Electron Emission Microscopy (BEEM) is a scanning-tunneling-microscopy-based technique which gives a plan view, nanometer scale image of electronic properties of a buried interface. Among the properties which can be imaged are barrier height, the edges of multiple conduction and valence bands, and carrier scattering. These properties can be correlated with strain, defects, and stoichiometry variations at the interface. A topographic image of the sample surface is aquired simultaneously with the interface image. BEEM data has been reported from six laboratories to date, including images of Au/Si, Au/GaAs, NiSi2/Si, and Au/CdTe. Several new systems, some designed for ultra-high-vacuum operation, are under construction.

In the simplest implementation, electrons or holes are injected from a tunnel tip into the metal electrode of a metal-semiconductor diode (figure 1). The carriers are ballistically transported across the electrode and, if momentum, energy, and scattering criteria are satisfied, are collected in the semiconductor base. Momentum conservation requires the ballistic electron or hole beam to cross the interface within a small cone of solid angle, and hence the collected current only reflects injection into a small region of the Brillouin zone. This small critical angle cone is responsible for the high spatial resolution of BEEM. By varying the potential of the initial injected beam (i.e. tip voltage with respect to electrode), the electronic dispersion relation of the substrate can be spectroscopically probed.
Recurrent outbreaks of mumps in Lothian and the impact of waning immunity
Authors: Waugh C. J. , Willocks L. J. , Templeton K. , Stevenson J.
Published: June 2020

Another large outbreak of mumps occurred in Lothian from October 2017, which coincided with the commencement of the higher education term. During this period 324 cases were notified, most of whom were aged 18–22 years old. Although previous outbreaks had a focus in student populations, 43% of current cases reported that they were not a student. There has been increases in private student housing where students from all universities live, which may have contributed to the wide spread of the outbreak and complicated outbreak control. Information on vaccination status was available for 244 cases (75%), of whom the majority (75.8%) reported having two MMR doses. To investigate potential waning vaccine immunity the mean length of time since last mumps containing vaccine was calculated as 14.3 years. The outbreak was declared over in May 2018 after case numbers returned to background levels. This outbreak highlighted that mumps outbreaks occur cyclically coinciding with new cohorts of susceptible students entering the Lothian population. The lessons from this outbreak are to encourage students to have two MMR doses and also be prepared for mumps outbreaks in the near future. In future outbreaks the utility of a third MMR for outbreak control could be examined.
Lernen in immersiven Virtuellen Realitäten?
Authors: Lerner Dieter , Hölterhof Tobias
Published: June 2020

Zusammenfassung. Immersiven Virtuellen Realitäten (VR) werden in verschiedenen Trendreports große Potenziale für das Lernen attestiert. Allerdings verkennt eine allein auf die Medientechnologie fokussierte Perspektive die damit verbundenen Herausforderungen. Lern- und medienpsychologisch gut begründbare Effekte von VR lassen sich in Studien nur eingeschränkt nachweisen. Spezifische Entwicklungs- und Forschungsansätze sind nötig, um Potenziale und Grenzen der Nutzung zu erproben.
Patient Reported Outcome von Online-Pflegekursen
Authors: Caspari Florian , Kropp Florian , Zündel Matthias
Published: June 2020

Zusammenfassung. Pflegekurse sind in Deutschland eine verpflichtende Leistung der Pflegekassen für pflegende Angehörige und sonstige interessierte Personen. Ziel der in diesem Bericht dargestellten Studie war es, Informationen über die Wirkung von Online-Pflegekursen zu erhalten.
Marine Nitrous Oxide Emissions off Northwest Europe
Authors: Sidder Aaron
Published: June 2020

Continental shelves and estuaries are natural sources of nitrous oxide, but current global estimates of these emissions carry a lot of uncertainty, a problem that calls for regional studies.
Injection‐Induced Earthquakes on Complex Fault Zones of the Raton Basin Illuminated by Machine‐Learning Phase Picker and Dense Nodal Array
Authors: Wang Ruijia , Schmandt Brandon , Zhang Miao , Glasgow Margaret , Kiser Eric , Rysanek Sarah , Stairs Ryan
Published: June 2020

Seismicity in the Raton Basin over the past two decades suggests reactivation of basement faults due to waste‐water injection. In the summer of 2018, 96 short period three‐component nodal instruments were installed in a highly active region of the basin for a month. A machine‐learning based phase picker (PhaseNet) was adopted and identified millions of picks, which were associated into events using an automated algorithm—REAL (Rapid Earthquake Association and Location). After hypocenter relocation with hypoDD, the earthquake catalog contains 9,259 ML −2.2 to 3 earthquakes focused at depths of 4–6 km. Magnitude of completeness (Mc) varies from −1 at nighttime to −0.5 in daytime, likely reflecting noise variation modulated by wind. The clustered hypocenters with variable depths and focal mechanisms suggest a complex network of basement faults. Frequency‐magnitude statistics and the spatiotemporal evolution of seismicity are comparable to tectonic systems.
BRPF3-HUWE1-mediated regulation of MYST2 is required for differentiation and cell-cycle progression in embryonic stem cells
Authors: Cho Hye In , Kim Min Seong , Lee Jina , Yoo Byong Chul , Kim Kyung Hee , Choe Kwang-Min , Jang Yeun Kyu
Published: June 2020

Brpf-histone acetyltransferase (HAT) complexes have important roles in embryonic development and regulating differentiation in ESCs. Among Brpf family, Brpf3 is a scaffold protein of Myst2 histone acetyltransferase complex that plays crucial roles in gene regulation, DNA replication, development as well as maintaining pluripotency in embryonic stem cells (ESCs). However, its biological functions in ESCs are not elucidated. In this study, we find out that Brpf3 protein level is critical for Myst2 stability and E3 ligase Huwe1 functions as a novel negative regulator of Myst2 via ubiquitin-mediated degradation. Importantly, Brpf3 plays an antagonistic role in Huwe1-mediated degradation of Myst2, suggesting that protein–protein interaction between Brpf3 and Myst2 is required for retaining Myst2 stability. Further, Brpf3 overexpression causes the aberrant upregulation of Myst2 protein levels which in turn induces the dysregulated cell-cycle progression and also delay of early embryonic development processes such as embryoid-body formation and lineage commitment of mouse ESCs. The Brpf3 overexpression-induced phenotypes can be reverted by Huwe1 overexpression. Together, these results may provide novel insights into understanding the functions of Brpf3 in proper differentiation as well as cell-cycle progression of ESCs via regulation of Myst2 stability by obstructing Huwe1-mediated ubiquitination. In addition, we suggest that this is a useful report which sheds light on the function of an unknown gene in ESC field.