bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the UHV-STM
Authors: Iwatsuki M. , Kitamura S. , Mogami A.
Published: June 2020

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.

Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.

The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.

On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.
Construction Of UHV-REM-PEEM for Surface Studies
Authors: Kondo Y. , Yagi K. , Kobayashi K. , Kobayashi H. , Yanaka Y.
Published: June 2020

Recent development of ultra-high vacuum electron microscopy (UHV-EM) is very rapid. This is due to the fact that it can be applied to variety of surface science fields.

There are various types of surface imaging in UHV condition; low energy electron microscopy (LEEM) [1], transmission (TEM) and reflection electron microscopy (REM) [2] using conventional transmission electron microscopes (CTEM) (including scanning TEM and REM)), scanning electron microscopy, photoemission electron microscopy (PEEM) [3] and scanning tunneling microscopy (STM including related techniques such as scanning tunneling spectroscopy (STS), atom force microscopy and magnetic force microscopy)[4]. These methods can be classified roughly into two; in one group image contrast is mainly determined by surface atomic structure and in the other it is determined by surface electronic structure. Information obtained by two groups of surface microscopy is complementary with each other. A combination of the two methods may give images of surface crystallography and surface electronic structure. STM-STS[4] and LEEM-PEEM [3] so far developed are typical examples.

In the present work a combination of REM(TEM) and PEEM (Fig. 1) was planned with use of a UHV CTEM. Several new designs were made for the new microscope.
Advances in Stem Instrumentation for Biology
Authors: Wall J. S.
Published: June 2020

The forte of the Scanning transmission Electron Microscope (STEM) is high resolution imaging with high contrast on thin specimens, as demonstrated by visualization of single heavy atoms. of equal importance for biology is the efficient utilization of all available signals, permitting low dose imaging of unstained single molecules such as DNA.

Our work at Brookhaven has concentrated on: 1) design and construction of instruments optimized for a narrow range of biological applications and 2) use of such instruments in a very active user/collaborator program. Therefore our program is highly interactive with a strong emphasis on producing results which are interpretable with a high level of confidence.

The major challenge we face at the moment is specimen preparation. The resolution of the STEM is better than 2.5 A, but measurements of resolution vs. dose level off at a resolution of 20 A at a dose of 10 el/A2 on a well-behaved biological specimen such as TMV (tobacco mosaic virus). To track down this problem we are examining all aspects of specimen preparation: purification of biological material, deposition on the thin film substrate, washing, fast freezing and freeze drying. As we attempt to improve our equipment/technique, we use image analysis of TMV internal controls included in all STEM samples as a monitor sensitive enough to detect even a few percent improvement. For delicate specimens, carbon films can be very harsh-leading to disruption of the sample. Therefore we are developing conducting polymer films as alternative substrates, as described elsewhere in these Proceedings. For specimen preparation studies, we have identified (from our user/collaborator program ) a variety of “canary” specimens, each uniquely sensitive to one particular aspect of sample preparation, so we can attempt to separate the variables involved.
Novel Approaches to Low-Voltage Scanning Electron Microscopy
Authors: Jones Arthur V.
Published: June 2020

In comparison with the developers of other forms of instrumentation, scanning electron microscope manufacturers are among the most conservative of people. New concepts usually must wait many years before being exploited commercially. The field emission gun, developed by Albert Crewe and his coworkers in 1968 is only now becoming widely available in commercial instruments, while the innovative lens designs of Mulvey are still waiting to be commercially exploited. The associated electronics is still in general based on operating procedures which have changed little since the original microscopes of Oatley and his co-workers.

The current interest in low-voltage scanning electron microscopy will, if sub-nanometer resolution is to be obtained in a useable instrument, lead to fundamental changes in the design of the electron optics. Perhaps this is an opportune time to consider other fundamental changes in scanning electron microscopy instrumentation.
Secondary Electron Imaging of Liquid Water Films in the Environmental Scanning Electron Microscope
Authors: Peters Klaus-Ruediger
Published: June 2020

High gas pressure scanning electron microscopy is now routinely possible with new microscopes operating between 0.1 and 20 torr gas pressure. Since the specimen chamber is separated from the electron optical column by pressure-limiting apertures, high gas pressures present at the level of the specimen do not affect the high vacuum in the column. The use of a single PLA underneath the last probe-forming lens allows maintainance of ∼0.1 torr. Twenty torr can be stabilized with two PLA, forming two differentially pumped pressure zones which may be incorporated into the last probe-forming lens.

One of the most important new features of high gas pressure microscopy is the possibility to alter the type of gas and its pressure over a large range. High gas pressures (>1 torr) are required for charge neutralization on rugged insulators and for gas amplification of the SE signal. Additionally, using water vapors, liquid water can be stabilized. However, the aqueous environment is only one example among many possibilities.

The secondary electron imaging of liquid water is a fascinating new aspect of scanning electron microscopy. At saturated water vapor pressures, water is stable indefinitely. Increasing or decreasing the vapor pressure allows condensation or evaporation of water and provides means to generate water films. As can be seer from Fig. 1, the stabilizing pressure for water at 20°C is 17.5 torr. Such a pressure would require a very short working distance for SE imaing. Therefore, it is preferable to reduce the specimen temperature and to establish vapor saturation at lower pressures. However, liquid water can only be stabilized at pressures greater than ∼4.5 torr.
New Configurations of Single - Crystal Scintillator Detectors in SEM
Authors: Autrata R.
Published: June 2020

There are two reasons for designing special geometrical configurations of detectors of signal electrons in EM.

1. For some traditional shapes of scintillators (discs) the quantum efficiency of single crystal YAG or YAP scintillators amounting to 5% - 7% is not fully utilized for achieving the maximum light output signal propagated in the desired. The reason is the small critical angle given by the high index of refraction of both single crystal materials. The shaping of single crystal scintillators and treating of surfaces by making use of the laws of geometrical optics lead to an increase of the value of the light output signal propagated in the desired direction.

2. Different kinds of information carried by signal electrons (especially BSEs) of different types must be collected by a detector of a specific geometrical shape placed in a suitable position with regard to the specimen.

Non-traditional geometrical configurations and optical modifications of detectors have been designed to solve the problem of a more
efficient propagation of light towards the photocathode of PMT, considering different types of signal electrons.
Condition of Energy and Incident Angle of Primary Beam for Voltage Contrast Observation Over Passivated Devices
Authors: Kodama T. , Koyama N. , Uchikawa Y.
Published: June 2020

Inspection of passivated micro devices using the scanning electron microscope (SEM) at a low primary electron energy has been increasingly studied. Under an appropriate condition of energy Ep and incident angle Φp of the primary beam, the voltage contrasts follow regular and reversible variations, corresponding to the device electrode voltage under the passivation; i.e., the capacitive coupling voltage contrasts (CCVC). In our previous papers, we reported an empirical formula for conditions under which SEM observations over the passivation layer can be made without serious charging disturbances. In the present work we investigate the charging free conditions of PSG, SiN and Si3N4 passivated devices and the storage time of the voltage contrast is measured for various values of Ep and Φp.

There exist a clear threshold of imaging conditions of CCVC with respect to Ep and Φp. Below the threshold, while continued imaging, the observed voltage contrasts follow regular and reversible variations. Above the threshold serious charging occurs and appears as bright and unclear contrast which never disappears throughout the observation. The two kinds of contrasts can be readily distinguished, since the charging contrast does not change its polarity whereas CCVC dose, when the applied voltages to the device electrodes are turned on and off. As was done in our previous works, the threshold values are determined by observing whether or not the observed voltage contrast follows reversible variation. The specimen used are PSG (1.2μm thick), SiN (1.1μm thick) and Si3N4 (0.8μm thick) passivated devices. Table 1 shows the threshold values of Ep for eachΦ p. The value of product Ep· cos2 Φp for each material becomes practically constant (= Ec). The value of Ec does not depend on the other imaging parameters such as magnification, primary beam current and scanning time per frame.
Low-Voltage Diffraction-Limited Probe Current: Limits Due to e-e Interactions in Intermediate Cross-Over
Authors: Barth J.E. , Jansen G.H. , Kruit P.
Published: June 2020

The minimum diameter of an electron probe is limited by diffraction to the FWHM of the Airy disc, δa≃ λ/2α where the objective aperture semi-angle will be limited by aberrations. For probe voltages Vp less than 10 kV, the relative energy spread ε will cause a to be limited by chromatic aberration to about (λ/Ccε)1/2. The total probe diameter is then δp = Kλ/2α:, K=1. Thus δp = (Ccε;)1/2, which is proportional to V −3/4. Altho the diameter of the diffraction limited probe depends on the voltage, energy spread and the quality of the optics, the current depends (very nearly) only on the voltage independent reduced brightness Br of the e-source.

The current into a probe that contains the gaussian image dg of an electron source of reduced brightness Br is Ip = BrVp(π/2 dgα)2. Since a probe without current is not very useful, dg must be greater than zero for sources of less than infinite brightness. The diameter of the probe will not dramatically increase until dg≃δp≃δa. Thus the current into a diffraction limited probe can be as much as Ip = BrVp(π/2 λ/2α α)2 = Brπ2/32 h2/me = Br 10−18 A.
The Determination of Spatial Homogeneity in Multiphase Mixtures
Authors: Misirli Zülal , Altan Burhanettin S. , Yörücü Hüseyin
Published: June 2020

The modifications of the properties of composite materials by controlling the ratio, size, shape, orientation and spatial distribution of the second phase particles is a well known phenomena. Although there are technique available for the quantifying of most of these parameters, there is no established technique for the determination of the spatial homogeneity; yet this property is also highly influental on the behavior of the material. The aim of this paper is to introduce a fully automated technique to determine the spatial homogeneity of second phase particles.

The technique presented in this paper was based on the technique reported by Eisenkolb and Lange and Hirlinger. In this technique the image area was divided by a grid having equal size squares (Fig.1). In a homogeneous mixture the proportion of the second phase would be the same in each square. However, because of the finite size and the agglomeration of particles, the proportion of the second phase varies. This variation is best represented by Relative Standard Deviation, Srel, which is defined as the standard deviation divided by the average. As finer grid sizes are used Srel would naturally increase. It was assumed that for a random dispersion Srel increases linearly as the size of the grid squares becomes smaller. In this study it was shown mathematically that this increase becomes faster when agglomerations are present.
User Interface Design Concepts of the Philips XL-Series Scanning Electron Microscopes
Authors: Peeters Marc H.
Published: June 2020

Recent developments in Scanning Electron Microscopy have been technology driven. Major improvements have been made in information exchange, image processing technology, mechanical precision devices such as specimen stages, detector design, field emision guns, etc. In this process of automation and refining , the SEM became a rather complicated instrument to handle up to its full capabilities. When designing a user interface for such an instrument, considerable care must be taken that the instrument can be operated in an easy, straightforward way without losing functionality due to oversimplified automation.

In the Philips XL SEM series, the user interface provides functional control over the microscope, where a function is defined by what the user wants to achieve, rather than by the individual hardware parts that have to be addressed in order to achieve the result. Such a function-based user interface can be realised by emploing a three-layered machine structure.

The first layer consists of a mix of hardware parts such as an electron gun, lenses, a scan generator, an image processor, etc. In a second layer automation and compensation routines are performed by dedicated computers linked within a distributed intelligence network. Thus any of the primary parameters can be changed and the effect can be observed immediately as the related parameters are automatically readjusted. The third, outer layer is the actual user interface, implemented as customer-defined application programs running in an MS-DOS (MICROSOFT™) Windows environment on a personal computer. Simple mouse control provides fast access to a variety of application programs such as microscope setup, imaging, specimen survey, EDX analysis, linewidth measurement, image analysis and image database management. The window applications are overlaid on the microscope image, since the image is the essence of microscopy.
Development of an Ultrahigh-Vacuum Ultrahigh-Resolution Scanning Electron Microscope
Authors: Tomita T. , Kokubo Y. , Harada Y. , Daimon H. , Ino S.
Published: June 2020

An ultrahigh-vacuum (UHV) ultrahigh-resolution (UHR) 100kV scanning electron microscope with a UHV specimen preparation chamber has been developed for in situ observation of clean specimen surfaces. The measured vacuum in the specmen area was about 2.2 × 10-8 Pa, and a 0.14nm lattice image of Au (220) was observed.

Field emission scanning electron microscopes have been developed for the past ten years for sub-nanometer analysis. However, in recent analytical electron microscopy of so-called “new materials” such as ceramics and semiconductors, half nanometer analysis in UHV has become extremely important for materials characterization.

Figure 1 shows an external view of the microscope. The microscope column and it’s control console are shown at the left and right, respectively. The seales of microscope column are only metal 0 rings and Cu-gaskets, and automatic bake-out is carried out at about 160°C.

Figure 2 shows the electron optics of the system. A thermal assisted field emission gun (TFEG) with a W (100) emitter was used as a high-brightness gun, thus ensuring a brightness of 2 × 108 A/cm2 · str at 100 kV.
Image Recovery Using Set-Theoretic Methods
Authors: Sezan Ibrahim
Published: June 2020

Recently, there is some interest in the application of set-theoretic methods to the solution of the image recovery problem in electron microscopy. Several current studies have reported promising results.The purpose of this paper is to introduce set-theoretic methods to the electron microscopy community.

In electron microscopy, the image recovery problem refers to obtaining an estimate of the ideal three-dimensional (3-D) image distribution from its incomplete and possibly noisy Fourier transform data.In the spatial domain, the recovery problem is stated on the basis of theobservation equation:

where vectorsg, fandn∈ RNdenote the lexicographical ordering of the (N-voxel) measured (degraded) image distribution, the ideal image distribution and the noise processes, respectively. The operatorD: RN→ RNdenotes the degradation operator that effectively limits the data to the “data cone” in the frequency domain. The degradation operator can be adequately modeled by a space-invariant (convolutional) operator, and thereforeDhas a block-Toeplitz structure.
Three-Dimensional Reconstruction of Native Androctonus Australis Hemocyanin
Authors: Boisset Nicolas , Taveau Jean-Christophe , Lamy Jean , Wagenknecht Terence , Radermacher Michael , Frank Joachim
Published: June 2020

Hemocyanin, the respiratory pigment of the scorpion Androctonus australis is composed of 24 kidney shaped subunits. A model of architecture supported by many indirect arguments has been deduced from electron microscopy (EM) and immuno-EM. To ascertain, the disposition of the subunits within the oligomer, the 24mer was submitted to three-dimensional reconstruction by the method of single-exposure random-conical tilt series.

A sample of native hemocyanin, prepared with the double layer negative staining technique, was observed by transmisson electron microscopy under low-dose conditions. Six 3D-reconstructions were carried out indenpendently from top, side and 45°views. The results are composed of solid-body surface representations, and slices extracted from the reconstruction volume.

The main two characters of the molecule previously reported by Van Heel and Frank, were constantly found in the solid-body surface representations. These features are the presence of two different faces called flip and flop and a rocking of the molecule around an axis passing through diagonnally opposed hexamers. Furthermore, in the solid-body surface of the top view reconstruction, the positions and orientations of the bridges connecting the half molecules were found in excellent agreement with those predicted by the model.
Binomial Attribute Sampling as an Aid in Defining a Representative Field of View in Microscopy
Authors: Osten Evariste F.
Published: June 2020

Statistical analyses are routinely applied to microscope data from micrographs (measurements, shape factors) and, using electron microscopes, from x-ray microanalytical systems (net counts, peak ratios). However selection of a field of view which is recorded on a micrograph and implied to be a representative image of the bulk of the sample (at that magnification) is done intuitively. Experienced microscopists do consider a number of factors in selecting and preparing a sample and then choose from many instrument operating parameters before they view the sample. At this point assuming that the best microscopy practice has been exercised there is still the problem of a great number of fields of view to select from. High magnifications exacerbate this selection problem: in an Ultra High Resolution Field Emission Scanning Electron Microscope sharp images of routine samples are easily obtained at magnifications of X100,000 - at this magnification, even with a small sample size (4mm × 7mm), there are 28 million mutually exclusive fields of view.
Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules
Authors: Mandelkow Eva-Maria , Milligan Ron
Published: June 2020

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].

In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?
Electron-Spectroscopic Imaging (Esi) of Frozen-Hydrated Lipid Vesicles and Membrane Proteins: A Comparison With Tem
Authors: Lücken Uwe
Published: June 2020

Imaging of frozen-hydrated lipid vesicles was carried out in TEM by Lepault et al. and Talmon et al. . It was concluded that the bilayer profile is independent of the lipid composition but depends upon the phase transition of the lipids forming the bilayer. Toyoshima et al. reported that the bilayer dimension depends upon the lipid composition. They found 4 nm for a cholesterine-rich membrane part in the surrounding area of the acetylcholine receptor.

Lipid vesicles of homogeneous size were prepared by sonication, dialysis and ultrafiltration with 200nm-pore membrane filter. Proteins were reconstituted into these vesicles by conventional methods.

Depending on the lipid-acid composition, the bilayer width varies between 3 and 6 nm; this width could be used as a standard provided it remains unaltered during preparation for electron microscopy. Embedment in ice should preserve the native dimension. The goal of this study is to confirm this contention. Therefore, we addressed the following questions:

Does the choice of focus influence the image dimension of the bilayer?

Does ESI provide advantages over regular cryomicroscopy?
Tomographic Three-Dimensional Reconstruction of Patch-Clamped Membranes Imaged With The High-Voltage Electron Microscope
Authors: McEwen B.F. , Song M.J. , Ruknudin A. , Barnard D.P. , Frank J. , Sachs F.
Published: June 2020

Patch-clamped membranes have revolutionized the field of cellular electrophysiology, but nothing was known about their ultrastructure until they were imaged using the high-voltage electron microscope (HVEM). In present study we compute a tomographic three-dimensional (3D) reconstruction ofpatch-clamped membranes made from a Xenopus oocyte according to standard techniques. The sample was prepared for viewing in the HVEM according to the dry-mounting technique previously described. A tilt series was collected with a 2° angular interval and an angular range from -64° to 66°. All micrographs were recorded at 1 MV (Fig. 1). Our alignment procedure was hampered by the lack of good fiduciary markers and the presence of the wall of the micropipette, however, we were able to compute a preliminary reconstruction of reasonable quality using the weighted back projection method.

Tomograms from the 3D reconstruction demonstrate that the cylindrical axis of the micropipette was not coaxial with the tilt axis of the HVEM state (Fig. 2). The reconstruction was rotated until it was coaxial with the y-axis of the reconstruction volume and a series of cylindrical projections were computed (Fig. 3). The projections from the inner radii show the thin profile of the disk which spans the micropipette, while the projections at larger radii show the distribution of features along the wall or the micropipette. The blurred area in the middle (and at the ends) of each cylindrical projection is caused by the missing angular range, while the blank area in the longest projection is a result of the slightly elliptical cross-section of the micropipette. A small 3D volume containing the pipette-spanning disk was extracted from the reconstruction volume (Fig. 4); the fibrous nature of the disk is evident. A different view of the disk is presented by removing tomograms which contain interfering features from the front and back walls of micropipette from the reconstruction in its original orientation (Fig. 5).
Principles and Practice of On-Line Data Acquisition For Transmission Electron Microscopy
Authors: Tietz R.
Published: June 2020

For about 15 years now TV-camera based image acquisition systems have been used in many laboratories. These TV-systems facilitate focusing and stigmating of the instrument at low beam currents and the recording of dynamic events in the microscope with a video-tape recorder. Recently, digital image processing systems have become available which make image accumulation or averaging possible, or which can correct for uneven illumination conditions. This simple image processing is the basis for further image analysis (Automatic control of TEM parameters or real analysis of the specimen).

The bottle neck in on-line data acquisition for a TEM is the image pick-up system. Compared to a photographic plate, which has about 10.000 by 10.000 resolved pixels, the resolution of commercial, TV-based camera systems is very poor, in the best case about 500 by 500 pixels. The poor resolution of TV-systems restricts the use of image analysis to objects which do not need large image fields.

Fig. 1 illustrates the principles of TV-based image pick-up systems.
Methods and Applications of UV Photoelectron Microscopy in Heterogeneous Catalysis
Authors: Rotermund H.H. , Engel W. , Jakubith S. , Oertzen A.v. , Ertl G.
Published: June 2020

A newly designed photoemission electron microscope (PEEM), based on electrostatic electron optics and fully compatible with UHV conditions, has been applied for the investigation of spatio-temporal pattern evolution associated with the oscillatory catalytic CO oxidation on platinum single crystal surfaces. The design of the instrument will be described by W. Engel in detail. The oscillations can be understood on the basis of an adsorbate induced (CO) structural change of the surface, which modulates the catalytic activity via the sticking coeffizient of O2. The mentioned spatio-temporal pattern evolution during CO-oxidation on Pt (100) has been previously observed by scannig photoemission microscopy (SPM), but time resolution was in this case restricted to about 1 min. Work function differences of about 0.3 eV between the oxygen and the CO covered Pt (110) surface give rise to the sufficent contrast of the images taken by the SPM as well as by the PEEM. The new instrument allows real time observation, storing the images by a video system still enables 20 ms time resolution. Imaging of the much faster reactions of CO and O2 with a Pt (110) surface has therefore become possible. For the first time “live” pictures of the spatial patterns on the (110) surface during these fast oscillations (period ˜ 1 s), including period doubling and transitions to chaotic behavior, have been observed.
Photoelectron Energy Spreads and Emission Properties of Some Organic Thin Films
Authors: Ash Timothy J. , Massey Gail A. , Zhou Hanchang
Published: June 2020

Photoelectric emission is of current interest for its applications to microscopy as well as for its possible use as an electron source for integrated circuit lithography, particle accelerators, x-ray sources, and free electron lasers. These diverse applications share a common requirement for electron sources of relatively high brightness. A significant difficulty to be overcome results from the fact that available light sources have photon energies too low to induce photoelectron emission from the materials of most interest. In particular, surfaces which emit electrons under illumination by visible or near ultraviolet light are limited to a small number of materials based on highly reactive metals. To explore a possible alternative, we have investigated the emission of electrons from organic compounds possessing an intermediate electron energy level which assists the emission process through multiphoton absorption. The energy spreads of electrons emitted from these surfaces are important because beam spreading and aberrations in an instrument can depend on the energy distribution. Here we describe transverse energy measurements of photoelectrons from thin films of 2,2‘-binaphthyl on silicon and copper substrates. This coating material was chosen because of its high two-photon quantum yield.
Analytical Electron Microscopy of Extraterrestrial Ice Analogs
Authors: Blake D.F. , Allamandola LJ. , Palmer G. , Pohorille A.
Published: June 2020

The natural history of the biogenic elements H, C, N, O, P and S in the cosmos is of great interest because it is these elements which comprise all life. Material ejected from stars (or pre-existing in the interstellar medium) is thought to condense into diffuse bodies of gravitationally bound gas and dust called cold interstellar molecular clouds. Current theories predict that within these clouds, at temperatures of 10-100° K, gases (primarily H2O, but including CO, CO2, CH3OH, NH3, and others) condense onto submicron silicate grains to form icy grain mantles. This interstellar ice represents the earliest and most primitive association of the biogenic elements. Within these multicomponent icy mantles, pre-biotic organic compounds are formed during exposure to UV radiation. It is thought that icy planetesimals (such as comets) within our solar system contain some pristine interstellar material, including ices, and may have (during the early bombardment of the solar system, ∼4 Ga) carried this material to Earth.

Despite the widespread occurrence of astrophysical ices and their importance to pre-biotic organic evolution, few experimental data exist which address the relevant phase equilibria and possible structural states. A knowledge of the petrology of astrophysical ice analogs will allow scientists to more confidently interpret astronomical IR observations. Furthermore, the development and refinement of procedures for analyzing ices and other materials at cryogenic temperatures is critical to the study of materials returned from the proposed Rosetta comet nucleus and Mars sample return missions.
Fsem: Fast Scanning Electron Microscopy
Authors: Fishbine Brian H. , Macy Robert J.
Published: June 2020

Commercially available SEM‘s offer a maximum “TV” framing rate of ∼30 Hz. We have obtained a digitally-acquired framing rate of 381 Hz with submicron resolution [1]. This is at a 25 MHz pixel rate, compared with the ≤4 MHz video bandwidth of TV-rate machines. We have also performed analog-acquired experiments at effective framing rates of 4.9 kHz and effective pixel rates of >50 MHz. Our present detection and recording system is capable of 200 MHz pixel rates, with reduced contrast range at higher rates. Extrapolating current technology suggests that GHz pixel rates with useable final image signal-to-noise ratios are possible [2].

In large part, the success of electron microscopy is due to: the high resolution possible with the small de Broglie wavelength of even keV electrons, small effective electron source diameters, and small optical aberrations of well-designed electron optics. With this resolution, SEM also attains large depth of focus with scanned, narrow electron beams. SEM micrographs are generally noted for exceptional sharpness and large depth of focus. The highest quality micrographs require scan times of tens of seconds or more.
Wealth Inequality in the Ancient Near East: A Preliminary Assessment Using Gini Coefficients and Household Size
Authors: Basri Pertev , Lawrence Dan
Published: June 2020

Investigating how different forms of inequality arose and were sustained through time is key to understanding the emergence of complex social systems. Due to its long-term perspective, archaeology has much to contribute to this discussion. However, comparing inequality in different societies through time, especially in prehistory, is difficult because comparable metrics of value are not available. Here we use a recently developed technique which assumes a correlation between household size and household wealth to investigate inequality in the ancient Near East. If this assumption is correct, our results show that inequality increased from the Neolithic to the Iron Age, and we link this increase to changing forms of social and political organization. We see a step change in levels of inequality around the time of the emergence of urban sites at the beginning of the Bronze Age. However, urban and rural sites were similarly unequal, suggesting that outside the elite, the inhabitants of each encompassed a similar range of wealth levels. The situation changes during the Iron Age, when inequality in urban environments increases and rural sites become more equal.
Investigation of central electrode artefacts of ionisation chamber effect on dose calculation using advanced calculation algorithms AAA and Acuros XB
Authors: Shaiju V. S. , Kumar Rajesh , Rajasekhar K. V. , Zacharia George , Phani Debjani , Bhasi Saju , Nair Raghuram K
Published: June 2020

Aim:

To investigate the central electrode artefact effect of different ion chambers in the verification phantom using the dose calculation algorithms Analytical Anisotropic Algorithm (AAA) and Acuros XB.

Materials and methods:

The dosimetric study was conducted using an in-house fabricated polymethyl methacrylate head phantom. The treatment planning system (TPS)-calculated doses in the phantom with detectors were compared against the dummy detector fillets using AAA and Acuros XB algorithm. The planned and measured doses were compared for the study.

Results:

The mean percentage variation in volumetric-modulated arc therapy plans using Acuros XB and the measurement in the head phantom are statistically significant (p-value = 0.001) for FC65 and CC13 chambers. In small volume chambers (A14SL and CC01), the measured and TPS-calculated dose shows a good agreement.

Findings:

The study confirmed the CT set of the phantom with detectors (FC65 and CC13) give more artefacts/heterogeneity caused a significant variation in dose calculation using Acuros XB. Therefore, the study suggests a method of using phantom CT set with the dummy detector for mean dose calculation for the Acuros XB algorithm.
Integration – Care Work – Diversity Management
Authors: Berchem David Johannes
Published: June 2020

Zusammenfassung. In die Qualifizierung von Geflüchteten zu zukünftigen Fachkräften im Pflege- und Gesundheitssektor setzen zahlreiche Einrichtungen große Hoffnungen. Doch wie gestalten sich die Integration von Menschen mit Fluchtbiografie und die Verankerung von Diversitykonzepten im Pflegealltag? Auf der Basis empirischer Forschungsergebnisse werden in diesem Beitrag die Herausforderungen sowie die Handlungsempfehlungen für das Praxisprojekt im St. Augustinus Memory Zentrum in Neuss diskutiert.
Sozial-kommunikative Kompetenzen in der Pflegeausbildung mit Projektarbeit stärken
Authors: Köhler Waltraud
Published: June 2020

Zusammenfassung. Auszubildende an der Schule für Gesundheitsfachberufe in Idar-Oberstein bearbeiteten innerhalb eines Projektes komplexe Aufgaben zum Thema „Demenz im Krankenhaus“. Ein Ziel der Projektarbeit bezog sich auf das selbstständige Arbeiten in heterogenen Lerngruppen. Die Auszubildenden lernten ihre eigenen Stärken sowie die der anderen Gruppenmitglieder kennen, diese zu vertiefen und individuell einzusetzen. Die Kommunikation und der Umgang mit Widerständen stellten eine nachhaltige Lernerfahrung dar.
3‐D Intrinsic and Scattering Seismic Attenuation Structures Beneath Kyushu, Japan
Authors: Shito A. , Matsumoto S. , Ohkura T. , Shimizu H. , Sakai S. , Iio Y. , Takahashi H. , Yakiwara H. , Watanabe T. , Kosuga M. , Okada T. , Yoshimi M. , Asano Y.
Published: June 2020

The attenuation of seismic wave energy is caused by intrinsic absorption and scattering. The former involves the conversion of seismic wave energy to heat energy via internal friction due to the anelasticity of the medium, whereas the latter involves the scattering of seismic wave energy due to random elastic heterogeneities in the medium. Quantifying both intrinsic (
) and scattering (
) attenuation is therefore important for understanding the physical properties of the Earth's interior and predicting seismic wave propagation. Here we develop a new procedure to separately map three‐dimensional (3‐D)
and
structures. The path‐averaged
and
values are obtained via an envelope‐fitting approach that employs a multiple‐scattering model. The path‐averaged
and
structures are then mapped into 3‐D space using a tomographic inversion technique based on sensitivity kernels, which are calculated from a Monte Carlo simulation of the radiative transfer equations. We apply this method to map the crustal structure beneath Kyushu, Japan, and obtain 3‐D
and
structures for the 1–2, 2–4, and 4–8 Hz frequency bands. The spatial attenuation patterns are similar for each of the analyzed frequency bands, with the spatial variability in
being more pronounced than that in
. The high‐
and
regions correspond to the locations of active volcanoes. Conversely, the northern Kyushu area possesses low‐
and
zones that correspond to low heat flow and Cretaceous granite, respectively. The overall
and
distributions correlate with thermal and geological structures, respectively.
Changes in Tropical Precipitation Intensity With El Niño Warming
Authors: Sullivan Sylvia C. , Schiro Kathleen A. , Yin Jiabo , Gentine Pierre
Published: June 2020

Mesoscale convection generates the majority of extreme precipitation in tropical regions. Changes to these precipitation intensities, P, with long‐term modes of climate variability have been hard to assess because they are not well represented in current climate models. Here we stratify a satellite climatology of convective systems by El Niño phase and cloud top temperature. We find that gains (losses) in high precipitation intensity (
 10 mm hr−1) are largest for the deepest (least deep) systems during El Niño relative to La Niña. The surface temperature and wind changes that define El Niño manifest as surface flux changes but are not sufficient to explain these
trends. We explore also the dynamical component of precipitation generation with a vertical momentum budget. Midtropospheric drying in the vicinity of the deepest systems boosts instability and ascent rates during El Niño, while the strengthened large‐scale ascent minimizes the drag force on their updrafts.
Does Ring Current Heating Generate the Observed O+ Shell?
Authors: Krall J. , Huba J. D. , Fok M.‐C.
Published: June 2020

The Naval Research Laboratory (NRL) Sami3 is Also a Model of the Ionosphere (SAMI3) ionosphere/plasmasphere code is used to examine the effect of ring current heating during a storm. With a ring current heating function added to SAMI3, a cold thermal (<1 eV) oxygen ion outflow is produced, with O+ density and location similar to observations of the so‐called “oxygen torus.” The ring current heating function is based on a Comprehensive Inner Magnetosphere‐Ionosphere (CIMI) model simulation of the 7 October 2015 storm. We find that the ring current can heat plasmasphere electrons, subsequently heating plasmasphere H+, and ionosphere O+. The resulting O+ outflows resemble observed O+ enhancements in the inner magnetosphere.
Using polygenic scores for identifying individuals at increased risk of substance use disorders in clinical and population samples
Authors: Barr Peter B. , Ksinan Albert , Su Jinni , Johnson Emma C. , Meyers Jacquelyn L. , Wetherill Leah , Latvala Antti , Aliev Fazil , Chan Grace , Kuperman Samuel , Nurnberger John , Kamarajan Chella , Anokhin Andrey , Agrawal Arpana , Rose Richard J. , Edenberg Howard J. , Schuckit Marc , Kaprio Jaakko , Dick Danielle M.
Published: June 2020

Genome-wide, polygenic risk scores (PRS) have emerged as a useful way to characterize genetic liability. There is growing evidence that PRS may prove useful for early identification of those at increased risk for certain diseases. The current potential of PRS for alcohol use disorders (AUD) remains an open question. Using data from both a population-based sample [the FinnTwin12 (FT12) study] and a high-risk sample [the Collaborative Study on the Genetics of Alcoholism (COGA)], we examined the association between PRSs derived from genome-wide association studies (GWASs) of (1) alcohol dependence/alcohol problems, (2) alcohol consumption, and (3) risky behaviors with AUD and other substance use disorder (SUD) criteria. These PRSs explain ~2.5–3.5% of the variance in AUD (across FT12 and COGA) when all PRSs are included in the same model. Calculations of area under the curve (AUC) show PRS provide only a slight improvement over a model with age, sex, and ancestral principal components as covariates. While individuals in the top 20, 10, and 5% of the PRS distribution had greater odds of having an AUD compared to the lower end of the continuum in both COGA and FT12, the point estimates at each threshold were statistically indistinguishable. Those in the top 5% reported greater levels of licit (alcohol and nicotine) and illicit (cannabis and opioid) SUD criteria. PRSs are associated with risk for SUD in independent samples. However, usefulness for identifying those at increased risk in their current form is modest, at best. Improvement in predictive ability will likely be dependent on increasing the size of well-phenotyped discovery samples.
The phosphodiesterase-4 and glycine transporter-1 inhibitors enhance in vivo hippocampal theta network connectivity and synaptic plasticity, whereas D-serine does not
Authors: Ahnaou A. , Broadbelt T. , Biermans R. , Huysmans H. , Manyakov N. V. , Drinkenburg W. H. I. M.
Published: June 2020

Dysfunctional N-methyl-D-aspartate receptors (NMDARs) and cyclic adenosine monophosphate (cAMP) have been associated with deficits in synaptic plasticity and cognition found in neurodegenerative and neuropsychiatric disorders such as Alzheimer’s disease (AD) and schizophrenia. Therapeutic approaches that indirectly enhance NMDAR function through increases in glycine and/or D-serine levels as well as inhibition of phosphodiesterases that reduces degradation of cAMP, are expected to enhance synaptic strength, connectivity and to potentially impact cognition processes. The present in vivo study investigated effects of subcutaneous administration of D-serine, the glycine transporter 1 (GlyT1) inhibitor SSR504734 and the PDE4 inhibitor rolipram, on network oscillations, connectivity and long-term potentiation (LTP) at the hippocampi circuits in Sprague-Dawley rats. In conscious animals, multichannel EEG recordings assessed network oscillations and connectivity at frontal and hippocampal CA1–CA3 circuits. Under urethane anaesthesia, field excitatory postsynaptic potentials (fEPSPs) were measured in the CA1 subfield of the hippocampus after high-frequency stimulation (HFS) of the Schaffer collateral-CA1 (SC) pathway. SSR504734 and rolipram significantly increased slow theta oscillations (4–6.5 Hz) at the CA1–CA3, slow gamma oscillations (30–50 Hz) in the frontal areas and enhanced coherence in the CA1–CA3 network, which were dissociated from motor behaviour. SSR504734 enhanced short-term potentiation (STP) and fEPSP responses were extended into LTP response, whereas the potentiation of EPSP slope was short-lived to STP with rolipram. Unlike glycine, increased levels of D-serine had no effect on network oscillations and limits the LTP induction and expression. The present data support a facilitating role of glycine and cAMP on network oscillations and synaptic efficacy at the CA3–CA1 circuit in rats, whereas raising endogenous D-serine levels had no such beneficial effects.
Sodium butyrate inhibits high cholesterol-induced neuronal amyloidogenesis by modulating NRF2 stabilization-mediated ROS levels: involvement of NOX2 and SOD1
Authors: Kim Seo Yihl , Chae Chang Woo , Lee Hyun Jik , Jung Young Hyun , Choi Gee Euhn , Kim Jun Sung , Lim Jae Ryong , Lee Joo Eun , Cho Ji Hyeon , Park Hansoo , Park Changho , Han Ho Jae
Published: June 2020

The gut–brain axis is currently being studied as a therapeutic strategy for neurological diseases, especially Alzheimer’s disease (AD). Obesity results in the gut microbiota dysbiosis, which includes butyrate-producing bacteria are reduced. Although sodium butyrate (NaB) has emerged as the potential therapeutic substance in AD, there is a lack of detailed results into what signaling pathways affect amyloidogenesis in AD induced by obesity. Thus, we investigated the regulatory role of NaB on amyloidogenesis in neuronal cells under high cholesterol. In our results, we verified that increased amyloid β peptide (Aβ) accumulation in the brain of obese mice and a reduction in butyrate-producing bacteria due to the gut microbiota dysbiosis induced by obesity. We showed that NaB decreased the expression levels of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) and Aβ accumulation induced by high cholesterol in SK-N-MC cells. We demonstrated that NaB was absorbed in cells through sodium-coupled monocarboxylate transporter 1 (SMCT1) and then inhibited high cholesterol-induced Aβ accumulation. Subsequently, we also observed that reactive oxygen species (ROS) were overproduced because of increased NADPH oxidase 2 (NOX2) expression under high cholesterol. Meanwhile, NaB decreased NOX2 levels through a reduction of NF-κB activity, which ultimately inhibited Aβ accumulation caused by high cholesterol. We demonstrated that NaB increased the expression levels of p21 under high cholesterol, contributing to p21/NRF2 (Nuclear factor erythroid 2-related factor 2) colocalization, which leads to NRF2 stabilization. NRF2 stabilization causes NF-κB inactivation, followed by NOX2 suppression and superoxide dismutase 1 (SOD1) upregulation. Thus, NaB withSOD1silencing under high cholesterol did not eliminate excessive ROS, and eventually resulted in Aβ accumulation. In conclusion, we demonstrated that NaB prevents excessive ROS through NOX2 suppression and SOD1 upregulation by p21/NRF2 pathway, which is critical for inhibiting BACE1-dependent amyloidogenesis in neuronal cells exposed to high cholesterol environment.