bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Microtubule Assembly: The View From The End
Authors: Cassimeris L , Spittle C , Kratzer M 
Published: July 2020

Abstract
The mitotic spindle is responsible for chromosome movement during mitosis. It is composed of a dynamic array of microtubules and associated proteins whose assembly and constant turnover are required for both spindle formation and chromosome movement. Because microtubule assembly and turnover are necessary for chromosome segregation, we are studying how cells regulate microtubule dynamics. Microtubules are polarized polymers composed of tubulin subunits; they assemble by a process of dynamic instability where individual microtubules exist in persistent phases of elongation or rapid shortening with abrupt transitions between these two states. The switch from elongation to shortening is termed catastrophe, and the switch from shortening to elongation, rescue. Although dynamic instability is an intrinsic property of the tubulin subunits, cells use associated proteins to both speed elongation (∼ 10 fold) and regulate transitions.
The only protein isolated to date capable of promoting fast polymerization consistent with rates in vivo is XMAP215, a 215 kD protein from Xenopus eggs.
3-D Electron Crystallography Reveals the “Off” State of Smooth Muscle Myosin.
Authors: Wendt T , Taylor D , Trybus K , Taylor K 
Published: July 2020

Abstract
The activity of myosin II from vertebrate smooth and non-muscle cells is controlled by phosphorylation of the regulatory light chain (RLC). Smooth muscle heavy meromyosin (HMM) is a truncated double-headed myosin molecule that is soluble at physiological ionic strength. Subfragments of myosin containing two heads retain phosphorylation dependent regulation but single headed subfragments do not and are always “In”(Cremo et al., 1995; Trybus et al., 1997) thereby implicating head-head interactions as a fundamental feature of regulation. We have used a positively charged lipid monolayer to obtain 2-D crystalline arrays of both the unphosphorylated, inactive form (I-form) and thiophosphorylated, activated form (P-form) from chicken gizzard smooth muscle HMM obtained from a Baculovirus expression system.
A comparison of averaged 2-D projections of both forms in negative stain at 2.3 nm resolution reveals distinct structural differences (Wendt et al., 1999). The two crystals have p2 symmetry but vastly different unit cell dimensions.
Role of Calcium Currents in E-C Coupling and Evolution of the T-System and SR in Developing Cultured Embryonic Amphibian Skeletal Muscle Cells
Authors: H Gonzalez-Serratos , R Cordoba-Rodriguez , D.R. Matteson , M. Rozycka 
Published: July 2020

Abstract
Adult frog phasic skeletal muscle cells have slow inward calcium current (ICa) (Stanfield, 1977) carried through L-type voltage dependent calcium channels. It has been suggested that ICa may play a role in E-C coupling (Cota & Stefani, 1981, 1989). However, phasic skeletal muscle cells contract for several minutes after the extracellular Ca2+ concentration ([Ca2+]o) is lowered to &lt;10-8 M (Armstrong et al, 1972). Therefore, extracellular Ca2+ (Ca2+o) is not essential for contraction in these fibers. It has been also shown, by blocking Ica that Ica is not essential for triggering contraction (Gonzalez-Serratos et al., 1982). These results have led to the conclusion that Ica has no obvious role in E-C coupling in adult amphibian phasic skeletal muscle. The question arises then as to what is the biological role Ica in phasic skeletal muscle? We have observed that embryonic skeletal muscle cells are capable of contracting during the first day of development in culture (Cordoba-Rodriguez, et al., 1996), before the T-system and the sarcoplasmic reticulum (SR)may have fully developed (Flucher, et al., 1993).
Quantitative Interpretation and Information Limits in Annular Dark-Field STEM Images
Authors: Nellist P D , Pennycook S J 
Published: July 2020

Abstract
In making quantitative measurements using electron micrographs we must regard the electron microscope as being an information channel. The information about the object is both in some way transformed by the image forming process, and information is lost through the existence of a spatial resolution limit and the addition of noise. To make quantitative measurements, we need to take account of all these effects.
Great progress has been made in making quantitative measurements from high-resolution transmission electron microscope (HRTEM) images (for example see Ref. [1]). However, the simulation of HRTEM images requires a full dynamical electron scattering calculation in addition to computing the effects of the objective lens aberrations. Although such calculations can provide excellent agreement with experimental data, the calculation times involved restrict the number of trial structure models that can be used, with the danger that such trial and error methods might miss the true object solution.
Environmental Optimization for Sub-0.2NM Scanning Transmission Electron Microscopy
Authors: Muller D A , Grazul J , Baumann F H , Hynes R , Hoffman T L 
Published: July 2020

Abstract
Sub-0.2 nm probes can now be readily obtained on Schottky field-emission microscopes[1]. However environmental instabilities are proving to be the limiting factors for atomic resolution spectroscopy and distortion-free annular-dark field imaging, as a result of the long acquisition times (comparable to those required for inline holography[2]), and from the serial nature of the scanning system where instabilities result in image distortions rather than reductions in contrast. Troubleshooting the two most common environmental problems are discussed here.
Electromagnetic interference can cause beam deflections in both the scanning system and the spectrometer [3](&lt; 0.3 mG r.ms for 0.3nm, &lt; 0.2 mG for 0.2 nm). These are most easily dealt with before the machine is installed, as substantial rewiring may be necessary. There is little that can be done about quasi-DC fields, such as from elevators and nearby trains and buses. Major sources of AC electromagnetic interference are unbalanced electrical loads.
Atomic Scale Characterization of Oxygen-Deficient Ceramic Membranes by EELS and Z-Contrast Imaging
Authors: Klie Robert F , Ito Yasuo , Browning Nigel D , Stemmer Susanne , Mazanec Terry J 
Published: July 2020

Abstract
The Perovskite structured ceramic (Lax,Sr1-x)(Fey,Cr1-y)O3-δ being developed for applications in oxygen transporting membranes. The permeability of this material is limited by the number of free ions, point-defects (oxygen vacancies) and electrons in the bulk. As any ordering of these unbound particles will restrict their mobility one key issue for controlling the membrane efficiency is the formation of ordered oxygen vacancies. In particular it is very likely, that at elevated temperatures ordered micro-domains progressively grow and asymptotically reach a stable equilibrium concentration. This is consistent with the observations of Kruidhof that below a specific order-disorder transition temperature equilibrium times of 30-40 h are required to attain steady-state conditions, irrespective of the thermal history of the sample.
We investigate the formation of ordered vacancies in (Lax,Sr1-x)(Fey,Cr1-y)O3-δ by atomic resolution Z-contrast imaging and electron energy-loss spectroscopy (EELS) using a 200 keV STEM/TEM JEOL2010L with a post column Gatan Image Filter (GIF).
Solute Atom Segregation to Yttria-Stabilized Cubic Zirconia Grain Boundaries
Authors: Dickey EC , Fan X , Pennycook SJ 
Published: July 2020

Abstract
Grain boundaries in yttria-stabilized cubic zirconia (YSZ) are believed to have positively charged grain boundaries with compensating negative space charge layers at ambient temperatures and pressures [1]. The space charge region is formed by equilibrium segregation of point defects to the vicinity of the grain boundary to establish local charge neutrality. The point defect distributions, calculated from analytical space charge models [1] show that the negative space charge region is formed by a depletion oxygen vacancies and an excess of substitutional Y atoms, indicated as'VO” and YZr’ in standard Kröger-Vink notation (see fig. 1). The grain boundary segregation, in turn, has important ramifications for the mechanical and electrical behavior of the material [1,2]. The present work addresses space-charge segregation in YSZ, specifically addressing variations in segregation with grain boundary misorientation. We have examined a range of symmetric tilt [001] YSZ grain boundaries since they allow us to systematically vary the misorientation while providing the opportunity for atomic scale analysis.
Direct Atomic Scale Characterization of Interfaces and Doping Layers in Field-Effect Transistors.
Authors: Topuria Teya , James Edward M , Browning Nigel D , Ma Zhiyong 
Published: July 2020

Abstract
The demand for the higher performance of semiconductor devices, for instance IC functionality, has stimulated industry to further scale the critical dimensions of the semiconductor devices [6]. Also, as parasitic capacitances are reduced in small device structures, the energy loss in these devices is consequently reduced. [1] Achieving the desired performance from such reduced device structures requires optimization of both the interface properties and dopant redistribution processes, such as diffusion and segregation, under various processing conditions. Only through a careful and accurate characterization of these properties on the atomic scale in the electron microscope we can achieve the understanding of the materials interactions during processing necessary to optimize these properties [2].
Conventional imaging and microanalysis techniques in transmission electron microscopy (TEM), such as phase contrast imaging and energy dispersive X-ray spectroscopy (EDS), lack either the spatial resolution or require extensive simulations and through focal series reconstructions to reveal the structure and composition of such interfaces/doping layers (and in the case of simulations may still not give a unique solution).
Electron Optical Consideration of 1 Å STEM With a Monochromator
Authors: Tsuno Katsu 
Published: July 2020

Abstract
Recent success of spherical aberration (Cs) correctors for TEM and STEM opened a new generation of microscopy. In order to achieve sub Å resolution in experiment, however, it is necessary to use a monochromator to reduce the effect of chromatic aberration due to the energy spread of the electron source. The monochromator is also necessary for the high energy-resolution EELS (HREELS). Three microscopes - sub Å TEM, 1 Å STEM and HREELS - and those combinations are considered to bring the high performance electron microscopes of the next generation. Among those three, 1 Å STEM has the highest technical difficulties from the point of view of electron optics instrumentation. In this investigation, we will describe the main electron optical problems, which we should solve within a few years, to achieve 1 Å STEM.
The main reason, why 1 Å STEM is so difficult, is the spread of the beam due to the second order aberrations of the energy filter used as the monochromator.
Mechanism of Reversible Conductance Transitions in a Crystalline Thin-Film
Authors: Sohlberg Karl , Gao Hongjun , Penny cook Stephen J 
Published: July 2020

Abstract
Recently there has been considerable interest in developing nanometer- and sub-nanometer-scale electronic devices. Of particular interest in this regard is whether individual molecules or molecular complexes can be employed as electronic device elements. Aviram et al. have reported switching and rectification in an organic thin film. More recently, Potember et al. have shown a field-induced conductance transition on a 500 nm scale, but did not demonstrate local reversibility of the transition. The reverse transition was induced only by application of a broad laser pulse or heat. We have observed and replicated reversible conductance transitions in a fully-organic crystalline complex, on a scale close to the dimensions of the unit cell.
A crystalline thin-film organic complex of 3-nitrobenzal malononitrile and 1,4-phenylenediamine (NBMN-pDA), exhibits reversible conductance transitions on the sub-nanometer scale when exposed to local electric field pulses from an STM tip.
Nu-Phase in Fe-Al-B Alloys
Authors: Chisholm M F , Duscher G , Pang Lixin , Kumar K S 
Published: July 2020

Abstract
FeAl alloys with 40 to 50 at % Al have an impressive combination of oxidation and sulfidation resistance, low density, and low cost and are thus considered as possible substitutes for stainless steels. However, before these materials can be used in structural applications, the fracture characteristics of the alloy's grain boundaries need to be improved. Small additions of carbon and boron have been considered and the resulting properties have been reported. Boron is found to prevent intergranular fracture in iron-rich alloys and to mitigate environmental embrittlement although the improvement is not as dramatic as is seen with Ni3Al alloyed with boron. Boron segregates to the grain boundaries in Fe-Al alloys and boride precipitates at the boundaries and within the grains have been observed.
In this paper, we report the composition and atomic arrangement in a recently discovered phase (designated v phase) found in Fe-Al alloys containing small boron additions using a combination of Z-contrast imaging and electron energy-loss spectroscopy.
Quantitative Analysis Of Bological Specimens by Spectrum-Imaging in the Energy Filtering Transmission Electron Microscope
Authors: Leapman RD , Brooks CM , Rizzo NW , Talbot TL 
Published: July 2020

Abstract
Electron energy loss spectrum-imaging (EELSI) in the energy filtering transmission electron microscope (EFTEM) can provide more accurate analysis of elemental distributions than that obtainable by the standard two-window or three-window background subtraction techniques. Spectra containing many channels can be extracted from regions of interest and analyzed using established methods for quantitation. For example, the pre-edge background can be fitted by an inverse power law and subtracted from the post-edge spectrum. EELSI in the EFTEM is often superior to spectrum-imaging in the scanning transmission electron microscope for mapping specimen regions of size greater than 1 μm. This is due the much larger total beam current that is available at the specimen in a fixed-beam microscope relative to a scanned-beam microscope. Our aim here is demonstrate the advantages of such EELSI measurements for analysis of biological specimens. However, we also indicate some potential pitfalls in acquiring elemental maps in the EFTEM, which can be attributed to specimen instabilities during the acquisition.
Determining Concentration Limits for Boron Quantification Using EELS and for Energy-Filtered Imaging
Authors: Malac M , Zhu Y , Egerton R F 
Published: July 2020

Abstract
Electron energy-loss spectrometry and energy-filtered imaging allow the possibility of detecting, quantifying and mapping of boron. Boron spatial distribution in biological tissue is of particular interest for boron neutron capture therapy (BNCT) for cancer. We have studied the limits of boron quantification and mapping using electron energy-loss spectroscopy and energy-filtered imaging.
To evaluate the concentration limits for boron mapping and quantification three types of specimens were used. First, a uniform boron layer of well known thickness deposited onto of 50 nm-thick carbon film was used to determine the limits for boron quantification. Second, samples for boron mapping with non-uniform boron distribution were prepared by electron-beam evaporation of boron onto a shadow-masked 50 nm-thick carbon film. Third, tobacco mosaic virus (TMV) in a water solution of boronophenylalanine fructrose (BPA-F) was deposited onto a 2 nm—thick carbon film.
Towards 0.1 EV EELS Using a Beam Monochromator And Maxent Deconvolution
Authors: Tiemeijer PC , Overwijk MHF , de Jong AF 
Published: July 2020

Abstract
The resolution in Electron Energy Loss Spectroscopy (EELS) in (S)TEM is presently limited by the instabilities of the high voltage supply (typically 0.2 eV), by the resolution of the spectrometer (typically 0.7 eV), and by the energy spread of the electron source (typically 0.7 eV for a Schottky field emitter). An increase of this resolution to better than 0.1 eV would enable chemical analysis on a nanometer scale. We are presently following hardware as well as software approaches in order to reach this energy resolution in a 200 kV (S)TEM.
The hardware side of our project focuses on the three limiting factors mentioned in the previous paragraph. The instabilities of the high voltage supply are mostly noise and drift, which can be reduced significantly by isolating the high voltage tank, thermally as well as acoustically. In addition, Gatan is developing an imaging filter for this project, which has sub-0.1 eV resolution.
Development of a Real-Time Elemental Mapping System in a Scanning Transmission Electron Microscope
Authors: Kaji Ueda K , Aoyama T , Taya S , Tanaka H , Isakozawa S 
Published: July 2020

Abstract
The ability to obtain elemental maps in a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) is extremely useful in the analysis of materials, and semiconductor devices such as ULSI's and GMR heads. Hitachi has developed a new type of elemental mapping system, consisting of a STEM (Hitachi, HD-2000) equipped with a two-window electron energy filter. In-situ calculation of the energy-filtered signal makes it possible to observe real time elemental mapping images with nanometer resolution.
Figure 1 shows a schematic of the elemental mapping system. In the STEM, electrons are generated from a cold field emission gun and accelerated to a potential of 200 kV. The electrons arc focused by the objective lens into a small probe (&lt;1 nm), which is then rastered over the specimen using scanning coils. Transmitted electrons are collected by an energy filter, which is located beneath the specimen., and consists of quadrupole lenses, a magnetic prism spectrometer and two kinds of electron beam energy detectors.
Analysis of the Structure of Bulk Metallic Glasses Using EXELFST
Authors: Alamgir FM , Hug G , Williams DB , Jain H , Schwarz RB 
Published: July 2020

Abstract
There has been a rejuvenation of interest in the field of metallic glasses in the last decade, ever since the discovery of alloy compositions which allow bulk glass formation. By definition, bulk metallic glasses (BMGs) are characterized by a critical cooling rate &lt; 10 K/s or a minimum dimension &gt; 1mm. We have chosen to examine the structure of the Pd-Ni-P system in order to explain, from an atomic structural point of view, its precipitously high glass-forming ability in this system with respect to those of the binary alloys. With three constituent elements the study of the Pd-Ni-P system remains tractable in comparison to other BMGs that often contain five or more elements. This system has a critical cooling rate lower than 1 K/s and is one of the simplest prototypes of a BMG. However, binary alloys of transition metals (e.g. Pd, Ni, Cu) with metalloids (P, Si, etc.) will not form BMGs even though they can be forced to retain a glassy structure with rapid quenching from the liquid phase.
Stability Performance of an Energy Filtering TEM
Authors: Benner G , Zellmann E , Harscher A , Härle R , Kabius B , Seybold Volker , Probst W 
Published: July 2020

Abstract
The electron-optical design and the technical realisation of correctors, monochromators and imaging spectrometers as well as methods of resolution improvement (Focus variation, Holography) have made significant progress in the past few years. For all such devices and methods the mechanical and electrical stability of the microscope are the main challenges.
Such requirements are even more critical in case of Energy Filtering Transmission Electron Microscopes (EFTEMs), where the achievement of highly resolved analytical results requires long detection times (in the range of a few 10s of seconds). Resolution in such case could mean both spatial and energy resolution even at the same time. The stability performance of the combined system is more complex than the sum of the stabilities of the single components. Thus, a specified HT short- and long-term stability of 2 ppm is not sufficient to achieve an energy resolution of 0.2 eV at 100 kV acceleration voltage.
Elemental Mapping of Materials Using Omega Filter and Imaging Plate
Authors: Ikematsu Y , Shindo D , Oikawa T , Kersker M 
Published: July 2020

Abstract
Elemental microanalysis has been important in materials characterization, since the elemental distribution strongly affects the property of various materials. A recently developed post-column energy filter coupled with a slow scan CCD camera makes it possible to carry out elemental mapping with a transmission electron microscope. Here, we develop the elemental mapping technique utilizing the omega filter and imaging plates (3760x3000 pixels). Since the data obtained from the imaging plates consist of a large number of pixels, fine and detailed elemental analysis will be expected.
Energy-filtered images were obtained by a JEM-2010 electron microscope installed with an omega-type energy filter, and they were recorded on imaging plates (FDL-UR-V:25 μm/pixel). The width of an energy-selecting slit was set to be 20 eV. Elemental maps were obtained from the energy-filtered images using the three window technique. Special care was taken to reduce the image shifts among the three filtered images used in the three-window method.
Determination of Mean Free Path for Inelastic Scattering in Poly(2-Vinyl Pyridine) by Low-Loss Spectrum Imaging
Authors: Aitouchen A , Chou T , Libera M , Misra M 
Published: July 2020

Abstract
The common experimental method to determine the total inelastic mean free path i by electron energy-loss spectroscopy (EELS) is by the relation : t/λi= ln(It/IO) [1] where t is the specimen thickness, It, is the total integrated intensity, and Io is the intensity of the zero-loss peak. The accuracy of this measurement depends on the thickness determination. Model geometries like cubes, wedges, and spheres enable accurate thickness determination from transmission images.
Spherical polymers with diameters of order 10-200nm can be made from a number of high-Tg polymers by solvent atomization. This research studied atomized spheres of poly(2-vinyl pyridine) [PVP]. A solution of 0.1% PVP in THF was nebulized. After solvent evaporation during free fall within the chamber atmosphere, solid spherical polymer particles with a range of diameters were collected on holey-carbon TEM grids at the bottom of the atomization chamber.
Simulation of in - Line Holograms
Authors: Frost Bernhard , Joy David 
Published: July 2020

Abstract
We simulated in-line holograms as obtained from a point projection microscope (PPM) [1]. The principal of the PPM is shown in Fig.1. A coherent electron wave emitted from a point source illuminates a sample transparent to the wave and travels to an electron detector. Since the wave from a point source is divergent the distance d of two points in the object plane results in a magnified distance D in the detector plane. The magnification of this arrangement is given by M=D/d=(z1+z2)/z1, where z1 and z2 are the tip to sample distance and the sample to detector distance, respectively. As no lenses are used we find a highly defocused shadow image in the detector plane. This arrangement is equivalent to Gabor's in-line holography with a physical source in plane of a lens-focused crossover, and the out-of-focus images are in-line electron holograms.