bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Resolution Lattice Images of Superconductors Observed at 4.2 K
Authors: Yoshida Hiroyuki , Yokota Yasuhiro , Hashimoto Hatsujiro , Iwatsuki Masashi , Harada Yoshiyasu 
Published: June 2020

High resolution cryo electron microscopy has been applied to the observation of microstructures of A15-type and oxide superconductors. In order to study the relation between atomic structures and superconducting properties the atomic resolution observation at cryogenic temperatures seems to be important, especially for high Tc superconductors with perovskite structure whose coherent length along c axis is closed to the lattice spacings. High resolution lattice images were obtained using a superconducting cryo electron microscope JEM-2000 SCM operated at 160 KV. The microscope enable the specimen to keep at 4.2 K without thermal drift and vibration under ultra high vacuum. The magnetic field at the specimen position is 1.4 T when the electron microscope is operated at 160 kV.Figure 1 shows a high resolution image of the electropolished thin crystal of Nb3(A10.77Ge0.23) (Tc=19 K). In the both sides of the grain boundary the (100) lattice fringes with 0.52 nm spacing of the A15 structure are clearly resolved. The high resolution images obtained for Nb3Sn superconductors gave the bright dots at the position of Nb atom chains along 001 direction as confirmed by the image contrast calculation.
HREM Study of the Plasticity in a Si Bicrystal
Authors: Thibault Jany , Luc Putaux Jean , Elkajbaji Mohamed 
Published: June 2020

The Σ=9(122) <011> pure tilt silicon bicrystal has been deformed. The evolution of its structure under stress has been studied in details. It was shown /1,2,3,4,5/ that the deformation induced dislocations generally enter the grain boundary (GB) where they decompose into elementary GB dislocations (GBD'). GBD's react by glide and climb. The GB migrates when GBD's associated with step are moving along the interface. This leads to appreciable changes of the original GB structure whereas the misorientation angle between the two grains varies. This paper deals with the structure determination of all the defects involved in the previous transformation and of the different GB's structures encountered during the process. The HREM observations were performed on the JEOL 200CX (Cs=1.05mm) to avoid electron irradiation damage in silicon and the images were simulated using a dedicated computer.i) Initial Σ=9 (122) GB (θ = 38.94°): the initial structure has been studied /6,7,8/. The main feature is the zig-zag stacking of the 7-5 atom rings (called M structural unit Jin the (122) common plane.In the following the stacking of the GB period will be described by the sequence M+M− (M+ is the mirror of M− with respect to the GB plane).
Electron Crystallographic Determination of the Structure of Bacteriorhodopsin
Authors: Henderson R. , Baldwin J.M. , Ceska T.A. , Beckman E. , Zemlin F. , Downing K. H. 
Published: June 2020

The light driven proton pump bacteriorhodopsin (bR) occurs naturally as two-dimensional crystals. A three-dimensional density map of the structure, at near atomic resolution, has been obtained by studying the crystals using electron cryo-microscopy to obtain diffraction patterns and high resolution micrographs (1).New methods have been developed for analysing micrographs from tilted specimens, incorporating the methods previously developed for untilted specimens that enable large areas to be analysed and corrected for distortions. Data from 72 images, from both tilted and untilted specimens, have been analysed to produce the phases of 2700 independent Fourier components of the structure. The amplitudes of these components have been accurately measured from 150 diffraction patterns. Together, these data represent about half of the full three-dimensional transform to 3.5 Å. The distribution of the data which is included in the map is shown in fig. 1. For specimen tilts up to around 20° the data is essentially complete. For higher tilts the data is more sparsely sampled, and is at present about half complete.
Development of 120KV Electron Microscope
Authors: Suzuki S. , Mori S. , Mizuno M. , Ichikawa R. , Honda T. 
Published: June 2020

A new electron microscope (EM) of 120 kV has been developed. This EM is designed for biological study but it incorporates many new ideas as a new transmission electron microscope. The main features of this new electron microscope are as follows.A. New Lens System and ControlThe illumination lens and imaging lens system and these control methods have been improved in this EM. It has three illumination mode, which are the spot focus mode, the parallel focus mode and the α focus mode. In the parallel focus mode, the cross over point under the specimen is kept on an objective aperture, which is placed in the back focal plane. That makes it possible to set the small objective aperture such as 20 micron without field cut and any sacrifices of specimen tilting angle at very low magnification. The objective lens condition in the diffraction mode is depending on the imaging mode, which are MAG mode and LOW MAG mode. That means it has two diffraction mode, the objective lens is kept on in one mode and off in the other mode corresponding to the imaging mode, MAG and LOW MAG modes. So the beam position is kept exactly on the specified area on the specimen during the changeover between the imaging mode and diffraction mode.
Beyond One Angstrom
Authors: Crewe Albert. V. 
Published: June 2020

I believe everyone would agree we have just about reached the limit of performance of today's electron microscopes. This is not to say that additional advances will not take place, because there is always one more drop of blood to squeeze out. But it is certainly becoming increasingly apparent that we can not expect more out of the magnetic lenses that we now have. I am sure that everyone who has ever been concerned with this problem has arrived at the same set of conclusions but it may help to set them down one more time.The available resolution in electron microscopy is distressingly poor compared to the wavelength of the electrons. The culprit is always the objective lens. For low energy, say less than 5,000 volts, chromatic aberration is the offending element whereas at high voltages it is the spherical aberration coefficient which we must be concerned with. In both cases, there are some basic restrictions which apply. In the case of chromatic aberration it is always very closely equal with the focal length of the lens and for the spherical aberration coefficient the best we can do is about 1/4 or 1/2 the focal length.
Experimental Study on Correction of Spherical Aberration in Electro-Magnetic Round Lens
Authors: Chen Ergang , Mu Chongjun 
Published: June 2020

As we know that the spherical aberration in a round electromagnetic lens can not be eliminated. Therefor,the correcting of such aberration is an important subject to improve the ultimate resolution of electron microscopes and the performance of other electron optical instruments, such as electron beam manufactureing machines, electron lithographic machine etc.A combination of quadrupoles and octupoles which was proposed by Scherzer is a reasonable way to correct this aberration, but it has been proved practically unsuccessful. Crewe suggested that the sextu-pole elements could be used as a device to correct the 3rd order aberration of a round lens. Later he has showed that a system of two sextupoles with a round lens placed in the middle of it can acturely act as an electromagnetical concave lens if the focal length of this middle lens be settled to satisfy certain condition. Instead of taking terms of z7 in series solution of motion equation of electron in sextu-pole which Crewe had done, we took it up to z20to compute the amplitude r and slope r' of electron trajectory at each specific point z1 , z2 , z3, and z4along the optical axis. The results show that the action of sex-tupole-lens-sextupole system does act as an optical concave lens. It produces a negative spherical aberration. Differing from optical concave lens, in this system the negative aberration can be varied in a wide rang by adjusting the strength of sextupole k. Fig.2 shows a series of computed performances of electron beam near Gaussian image point while the strength of sextupole k=0 incase(a) and k1< k2in case (b) and (c). Evidently, this system does produce a negative spherical aberration while k is not zero.
CRYO-Electron Microscopy of Muscle and Muscular Componants
Authors: Lepault Jean , Delacroix Hervé , Erk Inge , Nicolas Gisèle , Ranck Jean-Luc 
Published: June 2020

Cryo-electron microscopy of vitrified specimens is used to study biological objects in their native aqueous environment. Preparation artifacts are therefore minimized. In addition, due to the fast cryo-fixation associated with the vitrification process, cryo-electron microscopy may be used for dynamic structural investigations. To take full advantage of these possibilities, we are studying isolated muscular componants: actin and myosin.We observed the polymerization process of actin filaments. When the ionic strength of a globular actin suspension (G-actin-ATP) is increased, actin polymerized and filamentous actin (F-actin) is formed. During the polymerization, ATP is hydrolyzed. Three chemical forms of F-actin are then successively formed: F-actin-ATP, F-actin-ADP-Pi and F-actin-ADP. F-actin visualized in the short time of the polymerization process (F-actin-ATP; F-actin-ADP-Pi is characterized by a disordered polymer. At steady state (F-actin-ADP), F-actin appears more ordered and has its well known appearence of a helical polymer. These results show that actin has different structures which may play a role in muscular contraction.
Performance Evaluation of a Novel Type of Low-Energy Electron Microscope
Authors: Senftinger Bertholdand , Liebl Helmut 
Published: June 2020

During the last few years the investigation of clean and adsorbate-covered solid surfaces as well as thin-film growth and molecular dynamics have given rise to a constant demand for high-resolution imaging microscopy with reflected and diffracted low energy electrons as well as photo-electrons. A recent successful implementation of a UHV low-energy electron microscope by Bauer and Telieps encouraged us to construct such a low energy electron microscope (LEEM) for high-resolution imaging incorporating several novel design features, which is described more detailed elsewhere.The constraint of high field strength at the surface required to keep the aberrations caused by the accelerating field small and high UV photon intensity to get an improved signal-to-noise ratio for photoemission led to the design of a tetrode emission lens system capable of also focusing the UV light at the surface through an integrated Schwarzschild-type objective. Fig. 1 shows an axial section of the emission lens in the LEEM with sample (28) and part of the sample holder (29). The integrated mirror objective (50a, 50b) is used for visual in situ microscopic observation of the sample as well as for UV illumination. The electron optical components and the sample with accelerating field followed by an einzel lens form a tetrode system. In order to keep the field strength high, the sample is separated from the first element of the einzel lens by only 1.6 mm. With a numerical aperture of 0.5 for the Schwarzschild objective the orifice in the first element of the einzel lens has to be about 3.0 mm in diameter. Considering the much smaller distance to the sample one can expect intense distortions of the accelerating field in front of the sample. Because the achievable lateral resolution depends mainly on the quality of the first imaging step, careful investigation of the aberrations caused by the emission lens system had to be done in order to avoid sacrificing high lateral resolution for larger numerical aperture.
A Simulation of Electron Scattering in Metals and its Application for Scanning Electron Microscopy
Authors: Kotera Masatoshi , Ijichi Ryoji , Fujiwara Takafumi , Suga Hiroshi , Wittry David B. 
Published: June 2020

In a recent research, the scanning electron microscope(SEM) has been shown to provide spatial resolution of less than 0.5nm. With the knowledge of the ultimate resolution or the factor which controls the resolution, it is possible to optimize the specimen preparation method and the choice of various electron beam parameters (eg. acceleration voltage etc.) For a precise discussion of the SEM image, it is necessary to take into account not only the signal (electron) production and the propagation in a specimen and its emission from the surface, but also electron trajectories in vacuum toward the detector. However, electron scattering process in the specimen does not depend on the detection system, and the resolution is mainly attributed to the spatial distribution of the electron emission from the specimen surface. Here, we focused on the electron scattering mechanisms in metals and developed a Monte Carlo simulation model of electron trajectories. Also, this simulation is applied to evaluate a compositional contrast in the SEM.In the present study electron interactions with atomic potential, inner-shell electrons, conduction electrons are taken into account. Cross sections calculated by the present model are shown in Fig.1 for [l]elastic scattering, [2]inner-shell (1s, 2s, 2p for Al) electron ionization, [3]conduction electron ionization through non-radiative plasmon decay, and [4] stable plasmon excitation in the conduction band electrons for Al. For the elastic scattering, the Mott cross section is used. For inner-shell electron ionizations by an electron collision, the Gryzinski equation is used. In order to express the plasmon-electron interaction in a free electron gas at the conduction band, the Lindhard treatment is used. This treatment is based on the random phase approximation in the dielectric response function of metals. The cross section is shown in a unit of the inverse mean free path. The cross sections for conduction electron ionization and the plasmon excitation agree with the data of Tung, Ashley, and Ritchie. Cross sections for inner-shell electron ionization, which Tung et al. have derived using the generalized oscillator strength, are also shown in Fig.1 for a comparison.
EDS Image Classification by Projection after Partitioning
Authors: King L. , Browning R. , Paque J. M. , Pianetta P. 
Published: June 2020

In the analysis of multispectral x-ray dispersive images of geological materials, it is found that the large number of mineral phases typically present, leads to a large number of significant principal component images. This large dimensionality produces difficulties in graphically presenting the data, and interactively partitioning die image. A further problem is in the nature of the mineral phase distributions. Some phases will be well separated, in at least one projection direction, and other phases are continuous mixtures, with two or more end points. Both types of mineral phase distributions can be found intimately mixed in a geological sample. The very different types of these distributions implies that routines for searching n-space for clustering will have difficulty producing a good projection of the continuous mixture phase. Also for this reason it is difficult to see how alternative projection techniques can give a meaningful weight to a mixed phase in the presence of well separated components.Here we describe a multi-step image analysis which circumvents the above problem, and promises to be a convenient, and relatively simple extension of principal component analysis (PCA). The analysis method relies on the fact that there is very often, some clear separation of an image after PCA, and that this clear separation can be readily observed in the first few principal component images. Thus the information in the first few principal component scatter diagrams can be partitioned interactively into regions that are well separated from each other, but may be individually complex. PCA can then be applied to the data subsets, and the process can be repeated until a meaningful projection of the data can be viewed in a low dimensional scatter diagram. The real image can then be formed using either density or false color imaging, depending on which is appropriate for the subset alone. The method is thus finding projections after partitioning.
Advantages of using Digitized Micrographs for Serial-Section 3-D Reconstruction
Authors: Marko Michael , Leith ArDean , Parsons Donald 
Published: June 2020

Digitized micrographs provide advantages in making 3-D reconstructions from serial sections. The use of image enhancement, magnification zoom, synthetic stereo, and rapid interactive review of the entire set of serial sections improves the accuracy and ease of reconstruction. We use the STERECON system for tracing contours from serial sections, storing the contour data, editing, and displaying the 3-D reconstructions. STERECON has options for stereoscopic input and display. Either digitized or conventional photographic images can be used with the system.Structures can be traced more easily in digitally-enhanced images. Digital image enhancement techniques have been extensively developed in the medical imaging field, and many of the same techniques are also useful for microscopy. Among the most difficult images to deal with photographically are those which have uneven exposure or a large variation in density. Since photographic film has a wider dynamic range than paper, it is difficult to bring out details in both light and dark areas of the image on the same print. Dodging results in loss of contrast which cannot always be recovered by using higher contrast grades of paper. Routine digital techniques can easily deal with this situation. In addition, nearly invisible, very-low-contrast structures in the image can be made distinct. Most importantly, edges of structures can be enhanced for more accurate tracing of contours. The extension of this is automatic contouring, which is used with varying degrees of success, depending on the complexity of the image.
Interaction of Proteins with Functional Monolayers: Recognition, 2D-Crystallization and Function
Authors: Ahlers M. , Darst S.A. , Grainger D.W. , Kornberg R.D. , Müller W. , Reichert A. , Ringsdorf H. , Rump E. , Salesse C. 
Published: June 2020

The interaction of molecular self organization and molecular recognition leads to the formation of functional supramolecular systems (see Figure 1). They combine order and mobility and their function is based on their organization.’ These fascinating phenomena - and the living cell is only the most perfect example - can help to mimic biomembrane processes as well as to develop new materials. The interaction of proteins with biomembranes is of fundamental relevance in many fields of biochemistry and medicine. Model biomembranes offer the possibility to simulate such naturally occuring processes. The monolayer technique in particular has proven to be an ideal tool to investigate the interaction of water soluble proteins with model membranes. Unspecific adsorption of proteins at charged lipid monolayers, specific recognition of ligand molecules by proteins and enzyme binding followed by enzyme action may lead to highly oriented protein domains and even to 2D-crystallization (see Figure 2).Due to its high binding constant (Kd = 10−15 mol-1), the biotin/streptavidin system is an ideal tool to investigate the specific interaction between a membrane incorporated receptor and a protein. Streptavidin is a protein which comprises four identical subunits, each binding one biotin molecule, and is well known from affinity chromatography. Biotin lipids with biotinylated headgroups have been synthesized to act as the membrane-incorporated receptors. Injection of fluorescent-labeled streptavidin underneath a monolayer of biotin lipids in the gas-analogue state results in formation of regular H-shaped optically anisotropic two-dimensional streptavidin domains. The crystallinity of these two-dimensional domains was determined by electron crystallography, revealing diffraction patterns with a resolution of 1.5 nm. The match of the electron density map thus obtained and the X-ray crystal structure of streptavidin is remarkably close, showing that two binding sites are still free and face away from the lipid layer, exposed to the aqueous solution. This offers the possibility of building up protein multilayer structures - even a second crystalline protein layer is imaginable, using the first streptavidin layer as a matrix for the binding of other biotinylated proteins.
Dosimetric evaluation of whole-pelvis radiation therapy of prostate cancers: clinical experience
Authors: Osei Ernest , Mansoor Hafsa , Darko Johnson , Osei Beverley , Fleming Katrina , Rachakonda Ramana 
Published: June 2020

AbstractBackground:The standard treatment modalities for prostate cancer include surgery, chemotherapy, hormonal therapy and radiation therapy or any combination depending on the stage of the tumour. Radiation therapy is a common and effective treatment modality for low-intermediate-risk patients with localised prostate cancer, to treat the intact prostate and seminal vesicles or prostate bed post prostatectomy. However, for high-risk patients with lymph node involvement, treatment with radiation will usually include treatment of the whole pelvis to cover the prostate and seminal vesicles or prostate bed and the pelvic lymph nodes followed by a boost delivery dose to the prostate and seminal vesicles or prostate bed.Materials and Methods:We retrospectively analysed the treatment plans for 179 prostate cancer patients treated at the cancer centre with the volumetric-modulated arc therapy (VMAT) technique via RapidArc using 6 MV photon beam. Patients were either treated with a total prescription dose of 78 Gy in 39 fractions for patients with intact prostate or 66 Gy in 33 fractions for post prostatectomy patients.Results:There were 114 (64%) patients treated with 78 Gy/39 and 65 (36%) treated with 66 Gy/34. The mean homogeneity index (HI), conformity index (CI) and uniformity index (UI) for the PTV-primary of patients treated with 78 Gy are 0.06 ± 0.01, 1.04 ± 0.01 and 0.99 ± 0.01, respectively, and the corresponding mean values for patients treated with 66 Gy are 0.06 ± 0.02, 1.05 ± 0.01 and 0.99 ± 0.01, respectively. The mean PTV-primary V95%, V100% and V105% are 99.5 ± 0.5%, 78.8 ± 12.2% and 0.1 ± 0.5%, respectively, for patients treated with 78 Gy and 99.3 ± 0.9%, 78.1 ± 10.6% and 0.1 ± 0.4%, respectively, for patients treated with 66 Gy. The rectal V50Gy, V65Gy, V66.6Gy, V70Gy, V75Gy and V80Gy are 26.8 ± 9.1%, 14.2 ± 5.3%, 13.1 ± 5.0%, 10.8 ± 4.3%, 6.9 ± 3.1% and 0.1 ± 0.1%, respectively, for patients treated with 78 Gy and 33.7 ± 8.4%, 14.1 ± 4.5%, 6.7 ± 4.5%, 0.0 ± 0.2%, 0.0% and 0.0%, respectively, for patients treated with 66 Gy.Conclusion:The use of VMAT technique for radiation therapy of high-risk prostate cancer patients is an efficient and reliable method for achieving superior dose conformity, uniformity and homogeneity to the PTV and minimal doses to the organs at risk. Results from this study provide the basis for the development and implementation of consistent treatment criteria in radiotherapy programs, have the potential to establish an evaluation process to define a consistent, standardised and transparent treatment path for all patients that reduces significant variations in the acceptability of treatment plans and potentially improve patient standard of care.